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In Reply to: RE: And each box has just 1 pair of input terminals? nt posted by rrob on August 09, 2010 at 20:52:45
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Follow Ups:
The bass amp (Adcom) was connected to the external crossover input and then from the bass output to bass section of speaker.MR/tweeter amp (Threshold) was connected directly to speaker's MR/tweeter section. The midrange fuse blew because there was no low pass filter for the midrange. The ribbon was protected by its low pass filter. I think I could use the Threshold on the MR/tweeter if there was a filter to protect the MR from DC.
I'm not sure whether the XO-1 provides any low pass filtering for the MR. If it does, it would solve the problem.
I do understand that active bi-amping is more efficient and why since the signal goes to the amp after the crossover.
Would an active crossover provide a low pass filter for the MR? If so that would be a better solution.
Randy
Edits: 08/09/10
Hi Randy,
You should not feed one amp directly into the Mid/Tweeter connectors on the Maggie back-plates ... these must be connected to the Mid/Tweeter output of the external XO boxes.
(Or to the output of the amp fed by the "hi" output of a 2-way active XO.)
So you need to choose 1 of your 2 amps to drive the Maggies currently - presumably the more powerful one?
NB: Whether one of your amps produces DC or not is not something you need to worry about.
You asked: " Would an active crossover provide a low pass filter for the MR? If so that would be a better solution ?"
No, the 2-way active XO completely replaces the external XO boxes and delivers bass LP & mid HP. The LP filter for the mid is part of the mid/ribbon XO which is under the sock, down the bottom of the frame, at the rear.
You also said: " The ribbon was protected by its low pass filter ."
Not exactly! :-)) The ribbon is protected by its high pass filter, which is part of the internal XO, under the sock. (A "high pass filter" passes the high frequencies - IOW it rolls off the bass.)
Regards,
Andy
Andy, clearly I don't understand crossover lingo. I think that under the sock is a crossover that divides the signal between the mid and tweeter. I think that the external crossover divides the signal between bass and MR/tweeter.
Why does connecting an amp directly to the mr/tweeter section of the speaker cause the fuse to blow?
Randy,As you say, under the sock is a crossover that divides the signal between the mid and ribbon. This is mid LP (lowpass - ie. it passes the lows and rolls off the mid as frequency increases) and ribbon HP (highpass - ie. it rolls off the ribbon as frequency decreases).
And the external crossover divides the signal between bass and MR/tweeter. This is bass LP (lowpass - ie. it rolls off the bass as frequency increases) and mid HP (highpass - ie. it rolls off the mid as frequency decreases).
" Why does connecting an amp directly to the mid/tweeter section of the speaker cause the fuse to blow ?"
Because you are feeding all the bass signal into the mid (which "normally" gets removed by the mid HP section of the external XO). So, far too much current is going through the mid panel ... and the fuse is doing what it's intended to do!! :-))
Just to repeat - you can't passively biamp with the stock external XOs that you have ... so just use one of your amps.
Regards,
Andy
Edits: 08/10/10
Hi Randy,
Its is very confusing I know and I have recently bought a pair of 3.3Rs from a shop where they had them wired up like this too for a demo, - thats how they thought you wried them up . In fact this was even worse as they didn't even have the external crossover boxes at all and didn't realise they were even needed, - they had one amp running directly into the bass panel inputs (so the bass panel was reproducing a full range signal!!) and the other into the internal crossover for the mid/treble, - both wrong of course! And of course the sound was appaling!I don't understand crossover lingo either!, - let me me try to explain it as I see it. Hopefully you will understand.
It confusing as you are right, the internal crossover does divide the mid/treble, but what were not getting is that the signal you were feeding into this internal crossover needs to initially be filtered of some low freqneucies (by a particular section in the external box) first before it reaches there. Its an obivious mistake to make. You were feeding the internal crossover a full range signal directly from the one the power amps instead and were missing out the first stage of the filtering process that cut off the low feqnecuies going into the the mid/tweeter terminal on the speaker, - this is not correct, and like Andy says its why the midrange fuse was blowing.Some Magnepan external crossover boxes (the wodden sides passive speaker level boxes) have two sets of inputs for biwiring/biamping, - your model does not unfortunately! This might seem like an unfortunate pain, and its true that yes you would have more flexibility to immediately passive biamp the speakers if you had an external crossover with two sets of inputs instead of one but you can get better results anyway I would have thought by mimiking what the external crossover box does for the mid/treble branch of the signal at line level instead of speaker level, - you can use a single capacitor at line level between preamp and the power amp (the power amp you are using for the mid/tweeter section) that will give you a bass cut signal BEFORE the signal actually reaches the power amp (not after the power amp as it usually does), - this bass cut signal from the power amp then does onto the internal crossover of the speaker and is correct as its a bass cut signal entering there. The advantage of doing the first stage of filtering needed for the mid/treble branch at line level is you can use a high quality and much cheaper/smaller voltage popypropylene capacitor for line level rather than the much bigger ones used in the wodden box at speaker level.
This is of course what the line level XO-1 (the black box) crossover does, - just some line level comopoenets inside that box, but you might as well do it yourself for much cheaper (if you can solder etc) , - you can also choose a capacitor tailor suited for your power amp's input impedance too.
So yeah Andy is right the reason the fuse was blowing is because the signal entering the internal crossover (the mid/treble terminals) was unfiltered of bass frequencies and contained too much current, - its a good job the fuse was there protecting the midrange panel. Send the internal crossover a signal filtered of bass freqneucies (either from an active crososver or a line level passive crossover as explained above) and there will not be a problem, - the fuse will not blow as there is less current in the signal.
Hope I have not confused you more. Let me know if you get it now. If not I'll try to explain again!
Cheers,
Colin
Edits: 08/10/10 08/10/10
Here another explanatnion of the same thing I just wrote explaining more how to hook it up, - let us know if you get it.So yeah if you want to passively biamp these speakers, - here is exactly what you have to do (hook up wise)
From the preamp, the signal is split into two. The first branch does into the power amp used for the bass panel. You connect the speaker cables coming out of that power amp into the wodden sides external crossover box you have, and then the "bass" OUTPUT leaving that wooden box goes into the bass panel terminals on the speaker. The other output of the wooden box that goes to the mid/tweeter seciton is totally unused. This is the SAME thing as you are doing now. NO CHANGE for the bass side.
This is where it gets different
The other output from the preamp is fed to the other power amp used for the mid/treble, but BETWEEN the PREAMP and the POWER AMP on this branch of the signal you need to insert a line level capacitor (solder one into an interconnect I guess) which will filter the signal of bass frequencies before it reaches that particular power amp. Then you run the speaker cable from that power amp into the mid/treble input directly on the speaker.
The alternative to this is to use an active crossover in between the preamp and power amps and achieve active biamping. This would be a massive improvement but to get started using the cap or the XO-1 is the only way for you to biamp these speakers.
The major advantage of using the active crossover is not to do with the part thats for the mid/treble seciton, - it on the other side, - giving you a huge advantage in running of the bass panel. You can send a signal cut of high frequencies at line level (from the active crossover) to the power amp for the bass panel as well, and then hook up that power amp directly into the bass panel terminals on the speaker, totally bypassing the external wodden crossover box and all the power /current sapping components in it. Hopefully you can see this will give a massive improvement in the drive of the bass panel.This is the best option by far, - take away that nasty wodden external crossover box and use an active crossover at line level instead. You can use the active crossover (between preamp and the power amps) to do the filtering at line level for both the bass panel and the initial imnportant bass cut filtering for the mid/treble branch OR (and especially if you get a cheap active crossover like the Behringer) you can instead use the active crossover on the bass side only. That is put the active crossover in between the preamp and the power amp used for the bass section ONLY. On the other side, between preamp and the other power amp (the one for the mid/treble) you can use the same line level capacitor you would use for passive biamping as I explained before. The latter option is potentially going to give you a purer/better sounding signal into the mid/tweeter power amp, and is a very good option to use if the active crossover you are using is a cheapie. As long as your preamp can supply enough active signal this will be fine.
Again I hope I have not confused you more!, - and I hope I have explained sufficiently the advanatges of going active and you understand now how relatively easy it is to do from where you are now!
Cheers,
Colin
Edits: 08/10/10 08/10/10
Thanks to all for the explanations, suggestions and patience. I started up without blowing a fuse. Next step is to find a starting point for bi-amping.
Your Threshold seems to be putting out DC at start up. This means that you need to leave a speaker level cap on the Threshold like the one inside the external crossover box. You can biamp with an active crossover on the bass, but the Threshold amp will have to be crossed at the speaker level with the stock value capacitor - just get a better one, like a Mundorf M cap - say the 12 uf bypassing a Jensen crosscap or Solen of 47 uF.The bass amp - Get another Threshold. Or a Pass. But bass duties are best done by one of the new very powerful class D amps that you can leave on forever and they will take less energy than a light bulb. The Threshold consumes far more power as a class A amp, and leaving it on will age it more quickly because of the higher operating temperature of Class A amplification.
Edits: 08/12/10
I was thinking about the Wyred 4 Sound 250 watt mono amps, but first I have to find a crossover. When you "say crossed at the speaker level with the stock value capacitor" does that mean add the cap to the crossover on the speaker?
I would not add it there, since it would be big and bulky and bulging out of the panel, but set it up in a little box with decent binding posts - you can tie it up on top of the original crossover box while you use it for passive biamp (bass crossover).
What were you going to use the 250s for? top or bottom?
on the bottom.
If I built a small box with two sets of binding posts, what would it look like inside? Is there just one 12 uf cap between the positive input and positive output? I'm trying to get a picture of what this looks like.
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Re Amp, the Wyred4sound amp for the bass would be the 500 monos. The 250 is too small (I talked to their guys a few months ago - their suggestion - I also believe them).
The IIIa external crossover is more complicated than I remembered, The midrange crossover is more complex than the one on the 3.6.
The portion of the external crossover for the midrange/treble is second order and includes a capacitor in series and an inductor in parallel .
The capacitor is a 60 uF piece, as we discussed. You can assemble it from the following wired in parallel
2 X Mundorf Mcap 22 uf
1 X Mundorf MCap 15 uF
about $540 see http://www.partsconnexion.com/capacitor_film_mundorf_suprm.html
Or compromise (what I suggested):
12 uF Kimber cap
47 uF Jenzen Cross Cap
Cost $100
http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-948&DID=7
Using a Mundorf M Cap for the small value (15 instead of 12 uF) would raise the cost to $170
To assemble the parallel cap, align the caps together with the short leads on one side and the long leads on the other, on each of the sides take the lead from the physically smaller cap and bend them towards the lead of the larger cap and twist the end around the larger cap's lead to form a loop around it. Solder that loop onto the other cap's lead at least 1/2 " away from the cap body.. Repeat on the other side.
Foil Inductors
http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=JANTZEN%20%20INDUCTORS&srchExt=&perPage=25&sortBy=4&layout=LIST&page=1&srchPrice=&srchCat=282&srchMfg=&srchPromo=&srchAttr=
you need a 3.5 mH Coil I would take a 12 gauge, which would be a $210 (3.3 mH)
The 14 gauge, which is definitely sufficient, would be $110
The 16 gauge - which is cutting corners just slightly, would be $80
Let me confirm that I understand. If I built this box with the 60 uf capacitor and 3.5 mH coil, I would then not need the external crossover for the mid/tweeter panel. I would place the box between my amp and the speaker. It would filter out 350 hz and lower (high pass) and therefore protect me from DC. I would still need an active crossover for the bass.
If instead I bought a two way active crossover, used the Threshold for the top and the Wyred 4 Sound on the bottom, I would still be vulnerable to DC.
I talked to Walter at Underwood Hifi. He suggested the bigger Wyred 4 Sound amps as well. I also wrote to Soderberg at Vintage Amp asking if my Threshold needs to be checked.
Randy
Hi Randy,
I am sure Satie will confirm but you are right on all that I think, - if you want to use the Threshold on the mid/tweeter section and avoid passing DC you could build this box consisting of the 60 uf capacitor and 3.5 mH coil which would be place after the Threshold. The box would then go on feed your mid/tweeter internal crossover, and you would not need to use the stock wodden sides external crossover at all if you used an active crososver for the bass amp/panel to do biamping (a great cheap option is of course the DCX2496 everyone keeps mentioning). The only other way to achieve biamping would be to buy an XO-1 or build a line level passive crososver for the bass section (same thing as the XO-1 anyway). But of course actively driving the bass section in a biamp setup (with the mid/treble driven passively at speaker level) would give you a big leap in performacen over using an XO1 and also protect your mid/tweeter from DC.But I've just realsied there is something you can very simply do here to achieve part active/part passive biamping and not have to build a box with the 60 uf capacitor and 3.5 mH coil yourself! Its very simple, - if you look at the IIIa crossver box on this schematic (section on the left) the 60 uf cap and 3.5 coil are of course already there to use for your mid tweeter barch befor entering the internal crossover of the speaker.
http://www.integracoustics.com/MUG/MUG/tweaks/stranger/MG-IIIa_Crossover.htmThe problem you are having now is there is no way to phsycailly access these two componenets in a biamp setup (only if you are using a single amp). BUT if you buy an active crossover for the bass the problem is sorted!, - use the active crossover and other amp on the bass panel, - thats one side of the biamp setup sorted, and simply run the other side going from the Threshold into the inputs of the external crossover box (which are now free to use) and then use the mid/tweeter output on it feeding your mid/treble input on the speakers. The bass output from the crossover box is of course not used - all sorted, no need at all to build another box wih that cap and inductor in at all. If you wire up the external crossover box like this with the bass output on it not used the bass components of the crossover in that box are not being used.
This is a pretty simple solution I think, - a bit of volume matching to do and fiddling about setting up the active crossover but thats it!. All you have to do is buy an active crossover that can do the right slope (3rd order I think it is) and right crossover point.
I don't have the external crososver boxes (they was missing) for my 3.3R so I can't do this unless I buy them from Magnepan. However after reaisling how simple this makes it to run a part active/part passive biamp setup I might well now buy external crossover boxes. I could use a line level equivalent instead using caps and inductors for the mid/treble (putting them between preamp and power amp) but that would involve changing values etc for use with different power amps and using the speaker level components protect the speaker from DC and that is a nice advantage and I like that. You are still getting the benefit of active operation of the bass panel, - far more efficient drive of it, - I'm sure it woudl be a big improvement.
Hope this helps. Satie if you reading this can you comfrim this is sound (I am pretty sure it is though despite not being very technical!)
Cheers,
Colin
Edits: 08/14/10
Hi Colin,I think you're right. I could use the external crossover for the mid/tweeter instead of building the one Satie suggested. The difference between the two options would be quality of parts.
If the Threshold is putting out DC, I can't use it with an active crossover without adding that extra filter...which kinda defeats the purpose of having an active crossover on that section...unless the DC is coming from my tube linestage??? My memory is returning. I spoke with Kent English at Pass Labs about DC when I was interested in the X250:
"I have a single ended tube linestage and am in the market for an amp. My preference is to buy a solid state amp. I understand there can be matching problems with DC amps. Frankly I'm not sure whether this meant direct current, direct coupling or both but the X250 is both. Elsewhere I read that having coupling capacitors engaged/installed could remedy this. Another source said as long as the frequency response has a lower cutoff, I would be safe. The X250 has 0 to 100 kHz freq. response. The X250.5 has 1.5 to 100 kHz.. Is it ok to use the X250.5 with a tube linestage? Does it have coupling capacitors?
Randy
---
"The original X250 does not have DC coupling caps and will happily pass DC. This is not a problem for the X250, but can be for speakers with input transformers (IE some Electrostats). The X250.5 has input blocking caps and will not pass DC.Kent English / Pass Labs
------
Kent,I was looking at Magnepan for two channel but have older Def Techs in home theater which might be used for awhile until I collect all the pieces. Would the Maggies be safe with either amp?
thanks,
Randy
----Yes, as long as the pre-amp isn't dumping lots of DC into the power-amp.
Kent English / Pass Labs"Maybe active would filter out the DC if it comes from the tube preamp. Any thoughts?
If someone can explain differences between the Behringer, Marchand and Rod Elliot's active crossover, I would appreciate it. Can I buy an active crossover that has 3 way potential? I would like the option of eventually moving to that.
Edits: 08/14/10
The tube pre would have a coupling cap before the output and is unlikely to have produced the DC.
coupling caps. When I spoke to the maker of my preamp about using it with a Pass Labs X250, he had this to say:
"However, I see that it is a DC amplifier (can amplify signal right down to 0 Hz) and that may be an issue with any tube preamp. There are bound to be some start-up or switching transients in the tube circuitry that will pass straight through the power amp to the speakers and cause some popping and significant cone excursions. You can take precautions, such as always powering on the preamp 30 sec before the power amp and vice-versa on power down, but sooner or later you may end up damaging the power amp and/or speakers (although the power amp should have built in protection). If you do choose to go with this amp, perhaps you should consider canceling your preamp order and I will refund your deposit. I would hate to see you do damage to your power amp or speakers."
Regards,
Lloyd
Lloyd Peppard
Mapletree Audio Design
-----------------------------
Lloyd was definitely against using his preamp with an amp capable of DC amplification. Doesn't this mean that if the amp has frequency response of 7 hz to 100k hz, the amp would not amplify the DC signal generated by the preamp and therefore the amplified DC signal would not get to the speaker? By having a lower cutoff to frequency response, the amp is filtering out DC.
I was blowing fuses on start-up with the Threshold wired direct to the mid/tweeter panel. Isn't it possible that my preamp generated the DC, the amp amplified it because the frequency response of my amp must be 0 hz to 100k hz. There is no high pass filter on the internal crossover for the mid. The high pass mid filter is on the external crossover. The fuse responded appropriately protecting the mid from DC? An un-amplified DC signal would have been harmless.
And if that is the case, wouldn't an active crossover which sent only 350 hz and higher to the mid/tweeter panel protect the midrange from DC?
I looked at the schematic and the pics of the assembled pre. There is indeed an output cap, so I guess his simplified power supply is the cause, as it may leak current into the signal path and cause the coupling cap to charge rapidly and create a thump, and the signal ground can also introduce pops from the power supply at turn on if there is no control of its hookup prior to stabilization.
That said, your own Threshold experimentation shows that it is responsible for the DC at turn on, so you must have a cap in series with the Threshold's output. At least until you have a service tech deal with the issue.
An active line level crossover may prevent your preamp's start up spike - depends on the wiring, but a passive line level crossover will not do it because ground will be direct coupled and we suspect the ground to be a conduit for the DC.
Now I'll try to learn about the different active crossovers.
Randy
Hi Randy, -
ME too! (need to find out more about active crossovers options!)
We are in similar situations! (wanting to do this with the IIIa and 3.3R respectively). Guess you are interested in the active crossover as it might prevent this DC problem.
If you come across any interesting ideas let me know! From what I have read so far the Behringer DCX2496 digital crossover is probably the best option in terms of price and flexibility and with some cheap modding it can have really great sonic performance too. But if you see anything you think is better than let me know!
The recommended crossover for the Maggies is the Bryston 10B (thats what Magnepan recommend) but it very expensive and according to other guys here its not worth the money. I heard the Marchand are very good too (better value than the Bryston). Better sounding than the Behringer but not as flexible in the setup. I guess an upgraded Behringer would be comparable to a Marchand though.
Cheers,
Colin
Hi Rob,
Hope that helps you get started with the active crossover options. As for an active crossover potentially filtering the DC if its coming from the tube amp, I agree with you it sounds possible, but I am not technical enough to know!. Perhpas there is a way you can test if the DC is coming from the tube preamp and then whether an active crossover filters it out? I have little knowledge on this though you need to speak to someone like Satie!
Cheers,
Colin
HI Randy,
Yes I think the plan of using the external crossover boxes for just your midrange and treble section, and driving the bass section from an active crososver might be the answer for you, and maybe me too!
I don't know much about the different options for active crossovers but have started to gather a little info in the past few weeks as I plan to do what you are going to do as well.
The Marchards I'm sure are better sonically than the Behrginer DCX2496, but also more pricey. Not sure about the rod eliot.
However the Behringer I'm sure is hands down the most felxible unit, - it will do anything you way, - 2 way, 3 way (maybe even 4 no sure), and you can adjust the slopes to anything you want. (1st order, 2nd order, 3rd, 4th etc). Its does everyting in the digital domain too which the Marchard (for example) does not do (using A/D converters and then back using D/A converters). And it has a digital input too which might give better sound using a suitable source. Its also flexible in that you can use it with the Mic etc to get the base phase and EQ optimsied for your room (Looks a little tricky though). Satie and others know a lot more like this than I do but apparently its very useful feature.
I've gathered so far that the downside of the Behringer is that its sound is not as good as the others - BUT you can get the output stage changed/upraded for reasonable money which makes the sound a lot better apparently. And also bear in mind too you will not be using it for the mid/treble sections (initially at least) so its sound signature will not effect that. Satie told me that its bass performace is excpetional and the sound quality of it in stock form matters a lot less if you are using it only the bass panel. So I really think its easily the most flexible option for you right now. If you want to go 3 way active with it in the future and you want its sonics improved then you can get its output stage section upgraded by a place such as Endler Audio (Steves suggestion).
Bear in mind the cheaper Behringer analouge crossovers (CX2310, 3400) are apprently trash sound wise and only have 4th order slopes so are no good for the Mggies anyway). The DCX2496 is the unit to get.
Cheers,
Colin
Any worries about inductor resistance being lower than stock changing frequency balance?
The inductor of my 1.6 is 0.40 ohms and is of course, iron cored. The replacement I've drawn is aircore, 13 ga and 0.38 ohms, since even though I could go lower in resistance, I don't want to bump the output below the crossover frequency.
In process of designing a coil winding jig, so i can build 'em in pairs.
Too much is never enough
Look up the resistances and you will see that it is not that big a difference, Magnepan at least used to use fairly fat gauge wires for wiring and winding inductors - at least for the Tympani and later 3.x models.
The insertion losses did not come from the resistance but the active impedance.
Finally, if there need be a tweaking of relative volume levels (I think it is a must), it should be done at line level with a passive device like a Prometheus TVC, a Luminous Axiom, or an inline attenuator (see Tweakaudio and Endleraudio).
My problem is that I don't know how much of a difference in inductor DCR is 'not a big difference'.
That's why in my modeling of aircore inductors, I shot for a DCR close to 'stock'. My goal is to reap the benefits of greater power-handling capacity and near-zero saturation.....at nosebleed levels without effecting panel frequency balance.
Too much is never enough
The DCR and the minor deviation on inductance will not change anything of substance since the voltage ratio of the filter (Vout/Vin) is proportional to L/Rf so what will change is the crossover frequency, and the phase will move a little up or down. Furthermore, if you decrease L and R roughly in proportion, you will end up with stock value performance. Hence going to bigger gauge and taking a slightly lower value should keep you in line, while the net DCR difference on the order of 10% will give you a 0.4db difference - nearly inaudible. I don't believe the DCR of the speaker with the stock crossover and the DCR of the speaker with thick gauge inductors will end up more than 10% difference.
Cheers Randy,
Hope you can understand my long winded explanations, - tell me if not I'll try to short it down.
Like I say your cheapest bet right now to achieve passive biamping would be to use a line level capacitor in between the preamp and power amp used for the mid/tweeter. This is the most sensible way for you to achieve passive biamping. Adding a capacitor at speaker level instead is pointless.
Of course the XO-1 black crossver box will do the same job as the line level capacitor but it will cost you a lot more to buy the XO-1. The main advantage of buying a used XO-1 is that it will be more convenient and quicker, - no soldering of the capacitor to do.
A suitable capacitor for the job should cost you well you under $1. I don't know myself but Satie (to name but one) is a very helpful guy here, - he should be able to tell you what value capacitor to use if he has a look at your setup, - amps etc, and the IIIa speaker specs.
Let me know if you understand it OK,
Cheers,
Colin
Not exactly. The value of the capacitor depends on the treble amplifier impedance (C=1/2*pi*f*R) and may have to be changed. Also while a $1.00 cap will work, it will sound much better with a quality cap. These can be had from PartsConnexion and will run about $6-10 which on a relative scale is very expensive but, in absolute terms, very manageable.
I plan to procrastinate my demise for as long as possible. In the meantime, I practice by putting off all the little stuff.
Cool, thanks for the info, - I need to do this myself with the 3.3Rs when I get them to go active. When you say no soldering is needed? eeer....! what do you mean? (I am probably asking silly questions now!)And yeah if a £5-10 dollar cap will give a worthwhile improvement it well worth doing, - thats still relative peanuts, and I will do that myself too. I have no ideas about caps though and whats a good type to choose, - can you recommened one or two types at that sort of price range which would be suitable? (obviously the value would have to be worked out).
Cheers,
Colin
Edits: 08/10/10
I used Rel-Caps polystyrene-tin when I had a XO-1. A big difference from the caps that came with my XO-1 (which I bought back in 1980 or so for my IIb's and then used with my IIIa's). You can get them at Parts Connexion . If you can't find the exact value you may come close by paralleling them.
The high pass filter for the 3.3 mid driver is lower than the IIIa. I am not sure if Magnepan was recommending the XO-1 for the 3.3 but I would think that the -3db point would be about 350 Hz.
I plan to procrastinate my demise for as long as possible. In the meantime, I practice by putting off all the little stuff.
Thanks Neo,
Yes the 3.3R and IIIa crossovers have different values in them. I know for sure the ribbon is slightly different too so perhaps this is partly why the crossover is different.
I won't be getting an XO-1 as I might as well go for the Behringer DC2496 and go active instead instead (and like you say the XO-1 might be the best choice for me anyway as its probably designed for the IIIa, not 3.3R), but if I go with Satie's idea of using a partly active/partly passive line level crossover (passive on the mid/tweeter side), how would I go about choosing a suitable capacitor value to use if (for example) the right crossover point was 350Hz? I am a real NOOB with this!! Satie said too you might have to take into account your amp's input impedance when choosing the cap value too (input impedance of both my power amps is 20K)
Cheers,
Colin
The formula is C=1/2*pi*f*R so for a 20Kohm amp, C in mfd is 10^3/2*pi*350*20 or 0.022 mfd.
I chose 350 hz because looking at the native crossover, the mid HP has a -3db at 300 and since a first order xo has a softer slope I moved it up a bit.
I plan to procrastinate my demise for as long as possible. In the meantime, I practice by putting off all the little stuff.
Hi Neo,
I somehow missed this message before, - just read it now when browsing this thread, - many thanks for that, I was wondering what units to use when calculating this!!
Cheers,
Colin
Thanks a lot Neo,
This thread is getting a bit confusing to navigate!
If you see Satie's later posts with the diagrams he is saying that because of the IIIa (that Randy has) and the 3.3R use a different bass crossover scheme to the 3.6R (Satie had thought it was similar but it isn't, - he says the earlier speakers are more complicated in the bass crossover), I would not be using a single cap but 2 caps and a resistor as per his diagram, - I am now trying to understand that post (with trouble!) and work out what values to use! (again I'm not there yet by a long way!)I know normal passive single operation of the speakers is not as good, as active by a long way, but its an awful lot easier to do! I am starting to get a bit daunted with the planning for active operation! But I'm going to perseverve though, - I'll get there eventually (I hope!)
Cheers,
Colin
Edits: 08/13/10 08/13/10
NT
After my lenghtly correspondance with Satie (on the 3.3R crossover thread below) and his kind patience in explaining it to me many times!, I have now understood the following about active biamping operation of a 3 series Maggie. There are two main options for me.1. Get a HIGH QUALITY active crossover like a Bryston or another expensive one. Use this at line level between preamp and both power amps. No caps needed there.
2. The other option is for if you are using a much cheaper active crossover such as the Behringer DCX2496. Acoording to Satie if you hook this up in the same way as option 1 the bass will be great, but the mid/treble quality will suffer as the output stages of the Behringer are not up to scracth compared to an expensive active crossover.
You can get the Behringer upgraded apparently with better components, - this is available and is an option. But another option is to use the Behringer active crossover for the bass panel only. And for the mid/treble section to use partly a passive line level crossover (a cap between preamp and the respective power amp). Satie says this will give a much better sound quality to the mid/treble sections than having those important sections running through the Behrginer.So you can see this has an overlap with the passive biamping Randy wants to achieve, - for now he could use a suitable capacitor between the preamp and mid/tweeter power amp, and run the bass panel passively from the other power amp through the external MGIIIa speaker level crossover. Then perhpas at some point in the future he could then buy a Behringer DCX2496 or another active crossover for very cheap and use that for the bass panel ONLY (and remove the external MGIIIa crossover box), but leave the other side (mid/treble side as it is) with the capacitor there in between the preamp and power amp on that side.
Of course with the Behringer you can adjust the relative volume of the bass panel (you only need to adjust one section) so no probs in getting the levels right.
Its a bit confusing, - I'm sorry Randy if you don't undertsand it fully yet but hopfeully you are getting there. Have a read through my posts on this thread, - have gone over it a lot of time with different explanation so hopefulyl you'll get there eventually.
It took me while too to fully understand these two options for running a 3 series speaker actively, but thanks to Satie's patience I got there eventually!Cheers,
Colin
Edits: 08/10/10
I am active biamping with a modded Behringer DCX2496 and am very happy with my system. Perhaps I'll try the cap for the mid/high some day to see if I can hear a difference. You don't know if it is better or worse if you don't try it!
Thanks,
Steve
That Cool and good to know. It great the Behringer does not sound that bad, - so perhaps Satie was exaggerating a little bit!!
I will find out myself too when I try the two options out (and I will try both for sure to hear the difference) but I'd be very interested to hear as well your opinions if you try the line level cap in between preamp and power amp on the mid tweeter section, bypassing the Behringer on that side.I can see from connections and adjustments point of view its a lot easier/more convenient using Behringer on both sides, but if there is a big improvement in sound quality to be had from doing it the other way....?!!!! Look forward to hearing it you try it out! Its sort of a half active/half passive line level crossover scheme!! (active line level on the all important bass side, and passive line level on the mid/tweeter side!)
Cheers,
Colin
Edits: 08/10/10 08/10/10 08/10/10
Satie is much more knowledgeable than I am. The stock Behringer was acceptable, definitely a step up from using the Magnepan supplied external boxes and XO-1, but the mod is very good IMHO. I bought the DCX2496 with the intention of having it modded. I've included a link to the Endler Audio site. He even has some basic information on how to do the mod yourself. Of course, not having heard anything else I can't make a judgement. The Behringer has alot of flexibilty in crossover selection and setup. I have a spare pair of dead MGIII's that I intend to semi-Frankenpan/semi-Razor/semi-etc. one of these days. The Behringer would be quite useful for dialing in the XO for that.
Regards,
Steve
Cool, its great to know the stock Behringer is still acceptable so I can use that to get started with the 3.3Rs. Satie did mention the input impedance of the Behringer is a little low so the preamp would have to work a bit hard if you were using the line level passive crossover on the mid/tweeter side. But he said a buffer will help if you have an impedance matching issue from preamp to power amp on that side. So there might be some fine tuning to do but at least I'll be able to use the Behringer for everything initially to get started then I can choose the cap and tune that up for the other option of operation.
Many thanks for the link to the mod, - looks good. It might not be cost effective for me to do that with the shipping etc as I am in the UK. And its looks beyond my DIY capabilities! There is a place here Satie told me about that does Behringer mods too, - not sure if its the same thing, but I will look into it.
In the meantime I'd be very interested to hear the results if you tried the half active/half passive line level crossover approach in your setup, - to see if it sounded better than the upgraded Behringer. I understand though if you think its too much hassle to try and you are happy with your system the way it is now!
Cheers,
Colin
Randy, I hope all my posts have not confused you more!, are you OK now with the options available to sort things out?Steve, just wanted to ask, - I assume you run your Behringer DCX2496 using its analogue inputs only. I will be doing this too most of the time when I get mine, but I will also probably try its AES/EBU digital input as well as that bypasses the A/D converters. Most CD players don't have a AES/EBU output though of course, so I'd have to get a pro CD player or recorder, a CD player like a Roksan that has them, or use a coax digital to AES/EBU converter). I've heard too that SOME CD players can work from their coax digital output if you use a RCA to XLR converter, (but I need to look into that further)
I know you probably haven't , but was just wondering if you've used this digital input on the Behringer at all and if it is an improvement over using a CD player into the analogue inputs?Of course I realise that if you ran a CD player into the digital input on the Behringer, Satie's half active/half passive crossover scheme would not work, you'd need to run active only.
Cheers,
ColinAll the best,
Colin
Edits: 08/10/10
Colin,
I haven't tried the digital input, just the analog. There was a significant drop in the output when I had the mod done, i.e. I could turn the pre up very high and not get close to a red bar on the DCX input. I was using a pre that only had RCA outputs so I was using RCA/balanced adaptors. When I got a pre with balanced outputs I went balanced from the pre to the DCX, and from the DCX to the power amps. That helped to get the volume back. Then I used the adapators from the RCA output on the CD player to the balanced input on the pre and pretty much got back to where I was. Recently I put an audiophile fuse in the CD player and the output appears to be higher - I get more bars on the DCX input with the same volume knob position on the pre. Haven't put much thought into why this happened, but I'm enjoying the improved sound.
I didn't notice a drop in output with the stock DCX. To be honest, I've only scratched the surface of what can be done with the DCX. I've replicated the original crossover points and slopes but haven't played around to see if I can do better. Maybe when the snow flies again...
Regards,
Steve
Cheers Steve,
Thanks for the info, - so are you saying before you had the mod done there was more volume? (it sounds like the DCX was more sensitive to input then), - adn you were using exactly the same equipment as you were using before the mods?I think it might be (from what I've read about balanced/pro/XLR connections) that the output level coming from a device with an actual XLR Pro socket (like a preamp or CD player) is 10dB higher level than standard RCA, - this is the Pro standard output level I think. So this explains why you were getting more volume when you changed your CD and Preamp for ones with balanced/XLR connections. When you were using the older preamp with RCA to XLR adaptor the output level of that preamp was a lot lower than pro standard.
The DCX2496 is indeed a Pro device of course. And I guess its better running it at the intput levels it was designed for so I might get a preamp with XLR outputs that have the higher output level (and maybe a CD player with analogue XLR outputs too)I am not sure exactly but from what I have read the digitial input on the Behringer is better (if you are using CD) becuase it cuts out the A/D conversion stage used for the analogue inputs, and I think a lot of the mods for the unit address the quality of the A/D stage to get it those inputs up to the same scratch as the digital input (having said that though it looks like the mods you linked were for upgrading the output stages of the DCX).
I look forward to getting one of these Behringers. I will probably do the same as you and just really scratch the surface of what it can do, - I think Satie recommended doing bass management, - time deay for phase etc and other stuff to tune the unit to your room acoustics in the bass (he reckons it makes a big improvement ), - but I think you need a good microphone to do that to set it up, and I would have no idea where to start really! But if I find out how to do it and its not that hard I'll let you know!
Cheers,
Colin
Edits: 08/11/10
Get a Behringer SRC2496 to provide the necessary functionality: RCA inputs (or XLR) digital coax SPDIF - A/D - D/A and provide the AES/EBU digital out.
Here again, mods are available from Audiosmile's Behringer mods site and from Endleraudio.com and tweakaudio.com. Each do their thing differently, but achieve similar sonic results.
Re Endler audio, I pimp his mods and those from Tweakaudio.com very often - very cost effective, and make junk priced products useful to the audiophile. That said, I went to fish for the Audiosmile site for you since you are in the UK and shipping stuff for the US modsters to work on with incompatible line voltages and plugs is not my first choice in efficiency and cost control.
Thanks again Satie,
Sounds very useful, - I will look out for an SCR2496 as well then. My priority for the time being though is to try to find a used DCX2496. Nothing here at the moment (I missed a couple of cheap ones the other week). Hope something turns up soon. I plan to just set it up basically for the time being (perhaps running the mid/treble from it as well to start off with (before I get into finding the right cap values for the passive line level operation on that branch) and of course I'll look into setting up with a microphone after that is all sorted.
You are right about the modding, - very good thing to do. It looks like the Endler and the Audiosmile mods both alter the analogue output stage,. So you reckon that although they are different mods they probably both achieve a similar upgrading in sound quality from stock form?
Cheers again,
Colin
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Yes, they all take care of the output stage so as to take out the insane pile of redundant gain pull down and gain architecture that Behringer put in.
Take a look at the post I left for rrob on the crossover, yours is similar, and not like the 3.6 (cap only). The model 3.3 has a 90 uF cap and an 8.5 mH inductor.
For the line level equivalent, you need two caps and a resistor.
The circuit is in the pic above.
General rules
R1 = Ramp / 10
C1 = 1/ 2 Pi R1 f
C2 = C1/ 10
Values of caps are typically in the nanofarads and tens of nanofarads.
R2 is necessary when using tube preamps in order to bring up the load for the preamp, Typically this should be about 15 k ohms min. It will increase the insertion loss substantially, so don't put it in if you are using a SS preamp with single volt outputs (like the quad 66) with low output impedance.
Cheers Satie, Great info, really appreciate your help once again!
Am a bit lost again though to tell the truth though, but will try to understand this and get back to you!
Could using these caps resistors etc, be avoided output if I run mid/treble section actively from the Behringer instead (via power amp)? (like Steve is doing?). I know it won't sound as good as your suggestion, but for something more simple to get up and running?!, Or does it depend on what power amp I am using to power the mid/treble section?
Cheers,
Colin
Yes, for sure you can do it, but you need to understand that the original stock crossover slope here is second order not first.
The other thing is that it will make it necessary (rather than a nice thing to do) to upgrade the Behringer DCX. Our friend Keith here couldn't stand the Behringer at the mids/highs but was unwilling to put anything into modding till he had proven to himself that biamping works for him. Obviously it couldn't because the top end was irritating and he eventually gave up.
Thanks a lot Satie,
Well Steve said he used the Behringer in stock form before he got it up graded and whilst it was better upgraded and has better (less) gain, stock form was still acceptable to him. So I will try it to see how it sounds.
I'm a bit lost when you say
"you need to understand that the original stock crossover slope here is second order not first."
So are you saying if I use the Behringer it will be a first order slope whcih is wrong, - and it should be second? I am a bit lost, - I thought the Behringer was splitting at the bass/mid junction only which is 3rd order?
I'm going to also have to try to understand the diagram and notes you posted for me and Rob/Randy. So Randy should definitely put his 2 caps and resistors at speaker level becuase he is using that Threshold amp but I shoudl be OK doing this at line level? (and save a lot of money getting smaller components?, - hopefully!!)
Thanks once again,
Colin
Hey Davy you got a little lost.
First, the Behringer has adjustable slopes, it is not a fixed slope device. So what I am saying is that you will need to program in a second order slope rather than a first order (which is appropriate for an MG 3.6).
Magnepan normally builds crossovers asymmetrically, the low pass is an order higher than the high pass to the next higher driver. They then space the crossover somewhat widely to minimize phase or closely to fill in the dip in the crossover region, in which case the asymmetry allows the avoidance of cancellation off axis.
the IIIa 3.3 and 3.6 external crossovers are all different.
The IIIa and 3,3 have second order crossovers for the mid/tweeter combo. The values are different for both, with the 3.3 having a lower crossover frequency and hence a higher value cap and inductor. The line level equivalent would be like the one I posted above.
The MG3.6 has a simpler crossover for the midrange (1st order HP, 3rd LP) but a fourth order for the bass, a departure from prior maggie crossovers. I initially gave you a structure that is appropriate for the 3.6 (as I was helping a couple of folks with that model just before) but not right for your 3.3 or rrob's IIIa. It would work, but not be an exact equivalent to stock.
In the 3.3 you have the woofer with third order low pass, The midrange has a second order high pass (in the external crossover) and inside the speaker we have a third order low pass for the midrange and a second order high pass for the tweeter.
The 3.3 can be successfully crossed over with a third order electronic crossover for triamping, though the stock crossover differs in having a second order midrange high pass and a second order tweeter high pass. The sharper orders on the low pass filters cut off the drivers one to two octaves below their cavity resonances, for the benefit of clarity. The stock high pass filters follow the natural second order rolloff. With the third order electronic crossover, the asymmetrical crossovers are replaced with symmetrical ones and the alignment becomes orthogonal - thus allowing a somewhat broader sweet spot. The crossover area would not be as well integrated as in the stock crossover's careful alignment.
Hi Satie,
Sorry for my technical incompetance!, - thanks for the explanation, - I think I just about roughly understand that (well sort of!). So tiamping the maggies with an active crossover such as the Behringer would not be as straightforward as I thought (if you wanted to get the same good driver integration as with the stock crossover) due to the asymmetrial arrangement of the stock crossover.
So sorry for the misinformation Randy!However back to biamping and our current dilemmas, - am I right (in the post from easlier today), - in thinking Rob could just drive the bass panel actively using an active crossover and then use his now available MGIIIa external crossover box on the end of the Threshold amp?, - feeeing the mid/tweeter inputs on the speaker from the mid/mid tweeter outputs on the external crossover box, - as it has the same cap and inductor in it as the schematic you put up for him? Obviously the bass outputs on the external crossover box would be unused as the Behringer is being used as the crossover for the bass.
As for me I am in a different situation as I don't have the external crossover boxes. I am now tempted to buy them having reaslised you could do the above and that's quite simple to hook up, - would the above be accetpable from a sound point of view?, - basically drive the bass driver actively using Behringer and the mid/tweeter completely passively after the power amp? It would be nice to have the external crososver boxes in case I ever need to use just one amp on its own or if I ever wanted to resell the 3.3Rs.
Obviously I could just buy the Behringer and use that for the bass and put the first stage of the mid crososver passively at line level like you suggest in your diagram (2 resistors and 2 caps). I would not then need the external crossover boxes. Might the sound be a little better on the mid and treble doing this , as the first stage of that part of the crossver would then be line level not speaker level ? is that right?
Could I also instead go all the way and build myself a version of the entire external crossover box at line level instead? The mid/tweeter first stage does not look too hard (using the 2 resistors and 2 caps in you diagram), but is the bass part straightforward to replicate at line level too? Or is that not possible? And if it was possible would the results be as good as using the Behringer on the bass?
If I did it all passive line level I suppose I could use my Moth passive preamp between active preamp and the Quad 606 power amp (which has higher gain than the NAD208 amp I have) to balance the volume levels for the two sections.
Of course this option (building it all at line level) looks like it might be quite a bit cheaper than the other options!Thanks for the advice yet again!,
Colin
Edits: 08/14/10
The Behringer allows for any filter alignment you can conceive, so it is not a problem to perfectly reproduce the stock slopes and obtain Magnepan's chosen driver integration. After some time with the Behringer you can also try to tailor the bass - midrange crossover to fit the acoustics of your room better. So you were right earlier.
Re rrob's option of doing the bass with an active and crossing the mid/treble passively with the stock box, it is plainly doable. But that would mostly improve the bass. The top end will benefit from the Threshold remaining within its class A power delivery envelope for the bulk of playback time rather than only some of it (as is the case when it is tapped to power the bass too).
Sound wise, the parts in the mid/treble high pass in both the IIIa and 3.3 are really weak and old components and their replacement with good quality line level components would be a substantial benefit - in some aspects, even the stock Behringer will sound better.
"Obviously I could just buy the Behringer and use that for the bass and put the first stage of the mid crososver passively at line level like you suggest in your diagram (2 resistors and 2 caps). I would not then need the external crossover boxes. Might the sound be a little better on the mid and treble doing this , as the first stage of that part of the crossver would then be line level not speaker level ? is that right?"
YES absolutely!!! and it would be more than a little better.
You can build a purely passive version at line level for the bass and mid/treble, but it is no easy task (I tried it) as the insertion loss of a third order crossover for the bass will make it necessary to put in a gain stage and a volume control unless you build it with inductors - which will be warehouse sized spools of magnet wire or will have to have a ferrite core like Marchand uses for their passives. Since you have excess preamps, you can use one for the extra gain stage on the bass.
You will need at least one active preamp if you go all passive with the Quad, because its output voltage is low and will be used up in the insertion loss of the crossovers. The diagram I gave you contains an extra resistor R2 that would not be necessary with a solid state preamp like your quad.
Thanks Satie,
Thanks a lot for your great advice once again.
I have got the point now about the external crossover boxes, - it really is a waste of money buying them and the only advantage of having them is if I ever want to resell the speakers. So I will definitely try active or PLLXO options first, as I don't intend the sell the 3.3Rs anytime soon! (though mind I've not heard them in my room yet, they might terrible!, - lets hope not!)
Ahh I see you if you want to use two PLLXOs you get too much insertion loss, particularly from the 3rd order one for the bass, unless you build one with inductors which I obviously can't do easily.
So are you saying I could build a 3rd order PLLXO without inductors and use it for the bass if I use another active preamp?. I have another 2 available apart from the 2 Quad preamps (I will sell the Quad 66 but have have two NAD active preamp which sound fine (both with 2v output I think and capable of 12V peak). So where would I put the extra preamp? Between the main premamp and the 3rd order PLLXO or between the 3rd order PLLXO and the bass power amp? Sorry if this seems like a stupid question!
I bought the other NAD 1000 1990s preamp recently (not got it yet) as a spare preamp. Its similar to my NAD 1155, but a little newer. I was trying the 1155 today against the Quad 66 and 99 preamps. It does sound comparable, - more attacking than the 66 and a but less clinical than the 99. So its not bad at all. Its perhaps not QUITE as good as either of the Quads but surprisingly close, and it got a lot more gain too.
I like the Quad 99 preamp as it has it has remote volume, the tilt (which does work OK I've found out), and the adjustable phono stage (which I tried to day and it pretty good as well and very convenient). And of course it has adjustable input sensitivity on all inputs. The 66 sounds good too and a bit more musical but a bit too laid back so I'll resell that and keep the 99 for its more attacking sound and better features.
I'm guessing the NAD 1000 preamp will sound pretty similar to the 1155. Will find out when it comes.
So yeah I'd like to use the Quad 99 as the main preamp if possible. But like you say it has low output, so I if necessary I could use one of the NADs instead as the main preamp if that would be better for PLLXOs. The NAD 1155 has two sort of preamp outputs, - one is normal level and one is "high" level, - looking at the specs. The high one does have more gain than the normal one. And according to the specs the high level output can output a max peak voltage of of 15V in 10K (normal output gives 12V max into 20K). The output impedance of them is 600 ohms for the normal output and 220 for the high. So I think either of these outputs on this NAD 1155 preamp is more beefy than either of the Quad preamps. The NAD 1000 preamp only has the normal level output but according the specs again it can also output 12V into 20K max output, (and its output impedance is 220ohms).
So yeah do you think it would be possible to use one of these higher output NAD preamps feedling 2 PLLXOs, or would I still need another active preamp for the bass side? Like I say I could use the Quad 99 (or a NAD) and one of the NADs on the bass side if needed.
I hear what you say about the Behringer, the problem is right now I missed those used ones on Ebay (and none more have turned up) and I can't afford to buy a new one right now until I sell the Quad 66! (its summer and selling is slow!), and I need to pay for the 3.3Rs this week too (got them for £700 without the crossover boxes).
So I was thinking of maybe trying the 2 PLLXOs just to get started, then get the Behringer which I have the funds. I recognise the Behringer is great to have because the flexiblilibty it has in optimising the bass, and the sound potential if you get the output stage upgraded.
I've been reading aroudn about PLLXOs and foudn diagrams of 1st and 2nd order one but now 3rd order ones. I read though that a 3rd order low pass PLLXO is just three caps and three resistors? Is that right? And if so have you any ideas how I calculate the values? (haven't a clue!) If this is a really bad idea then let me know (and I'll wait and get a DCX2496 instead) but like I say I have 3 active SS preamps (Quad 99, Nad 1155 and NAD 1000) I could use for this 2 PLLXO set up if it might work.
Thanks again for your patience and help!
Cheers,
Colin
You can get a calibrated Behringer for not that much:
http://www.cross-spectrum.com/measurement/calibrated_behringer.html
Thanks Josh,
Thats cool, - I will consider that, - its pretty cheap you are right. Err, - how hard is it to use it?, - it is nearly as simple as locate the mic, then press a button on the DCX2496 to take some measurements or do you need to be a rocket scientist to use it?!!
Cheers,
Colin
I've never used the DCX2496, but AFAIK it doesn't have automatic calibration. In which case you'll have to do some response sweeps using your computer, and adjust the filters/crossover frequency to get the LF response (I assume you're using it on your subs?) that you want. Don't forget a mic pre and a stand! A little boom is good for response measurements. Keep in mind that you should try to get as close to the response as you can before applying EQ, since it can have audible side effects. Also, that you can't EQ out a null.
Thanks for the tips!, I am a bit lost with it really, - so you do test tone from the computer (do you mean play through the DCX2496). And you are hooking up the mic to the DCX? Have you any ideas how much a suitable mic preamp and stand cost.
As for the subs, I have two but not sure how they are going to blend with the Maggies. So you can use the Mike to set it up for the subs too (the crossover points for the sub etc?)
I will no doubt just do as Steve has done for the time being and try to replicate the stock crossover points and volume. Then I'll look into doing the mic! And setting up the subs as well!
Cheers,
Colin
The mic goes into the preamp, the preamp into your computer. Stand maybe $20-30, mic preamp not much more -- if you do a search online you'll find suggestions on preamps (or semi-pro sound cards) that are suitable, you might begin by checking that Beringer calibration site to see if they have a FAQ.
The test signal originates in your computer. You'll need a program to generate the signal and plot the results, I believe there are some that are free.
Agree that beginning with the stock crossover points makes sense. Then you can experiment with different slopes/characteristics/crossover points. Are you going to be using the Beringer for everything, or just the bass?
Also, yes, you should add the subs in after you have the main speakers tweaked out. When you do add the sub, you may find that you want to tweak out the resonant boost in the Maggie woofer.
I suggest that, at least to start, you equalize only the bass, maybe the 100-200 Hz Allison suckout. Higher frequency EQ can easily do more harm than good. You have to take multiple readings and it's difficult to get consistent results. Then you have to know what to tweak and what to ignore. So you'd want to bone up on the topic and get the bass and crossovers OK first, and even then, you may find, depending on the tools at your disposal, that EQ in the mids and highs can do more harm than good. Whereas bass EQ is fairly simple, the rules being optimize bass first as much as possible and you can't take out deep dips caused by cancellation. Those require changes in listening/speaker location, and to the extent that that doesn't work, bass traps.
Thanks a lot for the info Josh, - suppose it does not sound too hard...!, - I will give it a go though I reckon! I'll start with sotck crossover points and take it from there
Do you think the bass equilisation etc you can do with the DCX2496 will really make a huge difference to the overall sound in one's particular room? I knwo you've not used the DCX2496 yourself but I guess you've probabyl used seomthign similar.
I have a Quad 66 preamp I just bought to go with my Quad 606 (driving my 2.7s, - not got the 3.3Rs yet). The spectral tilt tone control on this preamp is better than any other tone control I have ever used and works wonders with the 2.7s in my room (I use a profile that raises post 1Khz and lowers below 1Khz). I think the 2.7s have a falling frequency response tendency in my room (they sound dark and a bit bloated), and this tilt control really does work wonders to fix the problem to a large extent!. Its an invaluable control for anyone using dipole speakers I think, - particularly as its so easy to use, - its up or down and that's it, - a toddler could use it! I guess I can try to change things using the Behringer but if I get stuck I can still use this great and very easy adjustment on the Quad preamp to equalise the Maggies in my room.
Saite says full triamping Maggies obviously give you better even better control to finely adjust things if you have a rising or falling FR tendency in your room (as you can adjust the relative volume of each section with triamping) but until I get there I live do without this tilt control! Now I've experienced this there is no way going back to a preamp without it! Might sell most of my other preamps actually!
All the best,
Colin
Cheers,
Colin
That tilt control sounds like a great idea. The ear is tolerant of that sort of gradual change. What it doesn't seem to like is mismatched attempts at precision EQ, e.g., with a 10 band equalizer or a parametric. Some of this may have to do with the sonic characteristics of the circuit, and some may have to do with curves that aren't minimum phase. But trying to fix peaks and dips with a 10 band always seems to degrade the sound, you need at least a 1/3 octave EQ and even then it's chancy. You can EQ the room to within +/- 1 dB, but it doesn't sound natural. More sophisticated digital equalizers like DEQX, on the other hand, can work wonders and I'm looking forward to playing with Thuneau Allocator.
I'd say that the EQ in the DCX2496 can indeed work wonders in the bass. It just isn't possible to get a smooth bass response in a small room without some very serious room treatment, most good speakers are fairly reasonable in the mids and highs but below 200 Hz you're always going to be stuck with very audible peaks and dips. I don't know if they can run enough filters in the DCX to properly equalize the treble, people tend not to use it there because it doesn't sound as good in the highs as it does in the lows.
There's also an interesting little bass-only equalizer that someone makes for about $350, I think it has automatic EQ. Don't remember what it's called but it was reviewed in a recent Stereophile. You could get one of those and dispense with the measurement mic, although you'd lose the ability to tailor the mids and highs later on, except by ear. Also, a frequency display is invaluable for matching subwoofer levels, you can try to do it with tones or music but it's a fairly frustrating business, among other things, the Fletcher-Munson effect means that the ear's sensitivity to bass is strongly dependent on how loud the music is.
Hi Josh,
Thanks a lot for the info, - I can see the DCX2496 is a great option for bass equalization (or maybe the other unit you mention but were not sure of the name of).
Having Maggies I think I really am going to be stuck with a Quad preamp for a long time now due to these tone controls, - I am picking up a newer Quad 99 preamp tomorrow that has the same tone controls, - it should hopefully sound a little better than the 66 though (will sell one of them on).
The 66 preamp also has an effective bass cut filter of two possible levels. The first level works well too with the 2.7s in my room and you can use it in combo with the tilt as well. There is also a treble cut filter of two steps but I don't use that (perhaps someone else would in a different room). I am pretty sure these tone controls were designed for use with the ESL63 electrostatic speaker of course, - where the same rising or falling FR tendency can occur in some rooms, but like you say they these tone controls are probably effective as they change things over a large amount of frequencies very gradually, and in my opinion it really does work,- and does not degrade the sound either, - I can't live without these controls now, - and I understand now why everyone else who tries out these tone controls says the same thing.
So perhaps I can begin to tune the sound with my Maggies with the tilt using the Quad preamp to get a nice starting point, like you say its probably very hard to equalize the treble and mid very accurately without something very sophisticated but the Quad will give me something quite nice to start with that I can live with. Then I can of course I can then use the DCX2496 to equalize the bass on top of this.
Thanks too on the info about bass, - I can see its hard to reproduce accurately in small room if you have dips etc. I have noticed that for sure in my small room. When you say drastic treatment what do you mean? Concrete again?!!
Here is the Quad 66 preamp manual, -
http://www.dadaelectronics.eu/_literature_32811/Quad_66_User_manual
You can see on page 7 amd 8 (real pages) that the tilt control, bass cut, and treble cut is explained there, and if you look at the appendix on page 12 it shows you the graph of what the controls do in full for all the steps. My ONLY SINGLE complaint about these tone controls is that whilst there is enough range of adjustment the steps of each change could do with being a little finer, - on the tilt for example there are 7 positions (including flat) , - what would be ideal in my opinion would be for there to be 13 steps of the same range (so double the fineness/resolution if you see what I mean. The way it is now the change on each step is 1dB difference between the middle 1Khz position and ends. 0.5dB steps would have been better but I'm still not complaining that much! These tone controls are still THE business for something so effective that's also so very simple to use!
Cheers,
Colin
No concrete, just bass traps in the corners, then along the walls if you really want to go to town. The idea is to absorb the bass reflections so as to minimize standing waves.
Cool Thanks Josh, I might try this. I see you can get quite cheap bass traps on Ebay etc, but I guess the situation is the same as it is with the sounds insulation tiles etc?, - is the cheap stuff not worth buying as its not as effective?
I could for sure put bass traps in the corners of the room(I assume you mean bottom corners of the room, do you mean all 4?), - do you need to put them in the top corners as well?
What I have really noticed a problem with the bass when using dynamic speakers in my room, - with my big Proac 3.5s. The bass sound fine when you are standing up, BUT when you sit down it decreases a LOT!, - which is obviosuly not great, and there are indeed I am sure suckouts and peaks throughout the bass region. running the two REL subwoofer with the Proacs can help the bass be a bit more even, but there is still obvious peak and dips and the bass does still decrease when you sit down. I guess this might tbe due to standing waves?
With the Maggies the bass does not disappear like this when you sit down, which is nice - though there are some other problems of course, - the Maggies don't have enough space to breathe in my small room and there is the falling FR response with increased frequency and the 2.7s for sure sound a bit bloated and dark in this small room and the bass is a bit too much in general, but like I say the Quad tilt control works wonders to improve things a lot for a easy fix that makes the speakers sound a lot more acceptable without doing anything drastic. I bought the Quad 99 preamp today, am going to try it out tonight vs the 66.
All the best,
Colin
Depends on the kind of bass trap. Sometimes panels are put in the corners where three walls meet, up to eight of them. Tube traps, on the other hand, are as the name suggests big tubes that stand in the corners, so you'd use a maximum of four in the corners, then if you wanted to go to town, maybe one in the middle of the speaker wall and some more along the walls at integral divisions. The idea is to get the trap where the standing wave has a pressure maximum so that you can absorb the most energy.
As to which traps are best, I'm not up on what's available now. ASC tube traps are an old standby, but there are many alternatives. The traps you choose, and how many you use, are going to depend on the room itself, as well as cost and WAF. It isn't just a matter of throwing traps in there. You need the right amount of absorption in the right places for your room, and you have to consider whether you just want to absorb bass with a resonant trap or whether you want to absorb mids and highs as well with an absorptive one. If you use resonators, you need to choose the frequencies and the Q of the resonators.
Chances are you'd hear an improvement if you threw a couple of tube traps in the front corners, they're closer to a one-size-fits-all solution than resonators, but I think you're better off if you have some measurements or room mode calculations, particularly since your room is so problematic, and some idea of the reverberation time in your room so you don't over-absorb the mids and highs.
Many thanks Josh,
Those tube traps don't look too hard to fit in the room, - four in the corners and some on the sepaker wall. as for the other type putting one on each place where 3 walls meet obviously mean 8 of them which is quite a lot and it might be hard to put up the high ones!
The ASC tube traps look very highly regarded from what I have read so far, - but to tell the truth the price is a bit of a problem!
I know this might not be as good but how abotu a DIY tube trap like this?
http://www.teresaudio.com/haven/traps/traps.html
Does not look too hard if I can get the right fibregless wrap
I'm not bothered about the aesthetics!
Worth trying do you reckon?
You are right though I need to get some measurements done too, - am going to look into this soon anyway for optimising the Behringer etc
Cheers,
Colin
I think DIY is a great way to go. There are other DIY designs online as well, not sure how good they are but really, perfection isn't needed here. The one thing I'd warn against is overdoing it. People who are getting into room treatment tend to think "Hey, this is great, more must be better!" but what you're aiming at is the sweet point . Two channel stereo requires a contribution from the room because it doesn't include enough ambiance. If the room is too dead, imaging will be great, but the sound won't come alive. So I'd start with a couple in the front corners, then try adding the rear corners, then maybe between the speakers, then along the walls. If the room starts to get too dead and you still don't have the bass resonances under control, you'll need to use resonators instead of absorbers. Also don't forget that planars like diffusers at their first reflection points, particularly behind the speakers as we discussed a while ago, but also on the sides. And that diffusion and mid/high absorption can usually be achieved naturally, with bookshelves, carpets, furniture, wall hangings, and drapes. Used minimally, of course.
Cool,
thanks a lot for this info Josh, - didn't know these tubes existed until today! And that you coudl possibly make DIY versions and save a lot of money!
I will look into doing it by DIY then and I'll be conservative like you say. Hoepeully it will improve my bass response in this room and with the Procas as well as the Maggies (The Procas are problematic when you sit down like I say). I will look into adding stuff at the first reflection for the Maggies too like you suggest.
Cheers again,
Colin
Colin, thanks for your help. I was out of town all day.
I'm considering all of the options. I am happy to report that the Threshold does not blow fuses when the wiring is done properly.
Cool,
Glad to hear the when you hook up the Threshold to the speakers on its own (via the internal crossover then use both branches coming off it) the speaker is not blowing fuses. Guess its because the signal now reaching the mid/tweeter has less current in it and the midrange panel was being protected as designed when you wired the speakers in the previous way with both amps.If you need any help or anything explaining your biamp options then let us know. Not sure what you are thinking but if it was me I would probably try the line level cap first, - that the cheapest option for passive biamping (much cheaper than buying a XO-1). Then I'd probably rapidly go active after that using a Behringer DCX2496.
All the best,
Colin
Edits: 08/10/10
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