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RE: Tweeter difference problem with 3.3Rs and more

Posted by Davy (A) on August 31, 2010 at 15:45:48

In Reply to: RE: Tweeter difference problem with 3.3Rs and more posted by Satie on August 31, 2010 at 14:23:34:

Hi Satie,
Many thanks for the reply. (bit of a long one this!)

OK cool will try to run the resistors in and see what happens.Thanks for the tip.

Many thanks for the info on the Technics damping, - that's interesting, - I might try the Denon DL304 then, - I had two but broke both!, - a bit costly, so I'll have to get another. (actually I've also broken 2 DL110s and 3 DL103s before as well)!
I agree the DL110 and DL160 are very good for the money too, - they actually have more bass than the 304, but they are nothing like as refined or transparent.
I agree with you on the OC9,- I tried that before, - its a horrible cartridge in my opinion, -clinical sounding and just coarse and nasty. From what I have read, the AT33PTG is vastly better though so I might try that one day, - people tend to like that one a lot.
To get started with he Technics I only have one cartridge to try at the moment which is on my LP12, - a retipped Linn Troika, - not sure how it will fare on the Technics, but its medium compliance so should work quite well on the stock arm I guess.

I agree with you it would be a great idea to move my crossover to all PLLXO, - I tried the stock Behrginer again tonight on both top and the bottom, - it really is terrible sounding in my opinion, - using the Behringer on the top section degrades the sound so much, - the part Behrginer on the bass/PLLXO on the top sounds so much better it is not even funny, and its my only decent option for the time being until I go all PLLXO

UPDATE!
I’ve found out something pretty interesting, - I got the MG3.3R manual from helpful Karen at Magnepan (looks like she scanned it for me).

What did you calculate the stock crossover points to be?, - was it 240Hz for the LP and 330 for the Hz?
Well in the manual it lists the stock crossover points at end of manual and also some recommended settings for using an active crossover. They are slightly different.

MG3.3R
Stock crossover points (at end of manual)
LP= -18dB (Butterworth) @ 200 Hz
HP= -12dB @ 300Hz

Recommended setting for use with an active crossover.
LP= -18dB (Butterworth) @ 200 Hz
HP, - Either use -12dB@ 250 Hz OR -6dB @ 300Hz


This is a bit weird, - why specify different crossover points to the stock setting when using active for the 3.3R? The 3.5 manual states something similar, - and even lower points for the HP when using active. In the manuals for the MGIII and MGIIIa they recommend the same points as the stock crossover when using active.

So for the 3.3R these recommended crossover points are obviously lower than what I have been using so far. Do you think the HP PLLXO values you calculated based on that stock schematic have a crossover setting of 250Hz? Or would it be nearer to 300Hz?, I guess its likely to be more like 300Hz if you calculated it from that stock passive schematic?. I don’t understand the poles thing you were on about and all that,so maybe that explains these differences?

But anyway based on these recommend settings, - this might explain partly why I am having trouble getting things to work. And explain the slight hole in the midrange I am hearing (though I agree the phase issue is obviously very important too).

But certainly what I need to do now hiss or not is to connect up the Behringer for both LP and HP sections (and ignore the hiss!) and try these settings (200Hz -18dB Butterworth for the LP) and both -12dB 250Hz and -6dB 300 Hz for the HP. 300Hz seems pretty low setting for a 1st order HP? Anyway, I must obviously try it.
Like I say I am not sure what crossover point the HP PLLXO you gave me was but when I was using the Behrigner for testing both HP and LP sections (before I knocked up the PLLXO) I was using 230-240 and 330-350 for the crossover points which are both obviously higher and more widely spaced than Magnepan specify for use with an active crossover.

Do you think I need to calculate some values for a PLLXO corresponding to this recommended lower crossover frequency of 250Hz? For -12dB HP?

The -6dB @ 300 Hz listed as an option instead of -12dB @250Hz looks very attractive to me too, - as that just a simple capacitor, - less parts so I guess in theory it might have the potential to sound better using that as a PLLXO than a 2nd order setup in that regard. And I think too (from what I have read, that its easier to blend a 3rd order crossover with a 1st order than is it to blend a 3rd order with a 2nd order. I have read that phase is less of an issue when blending 3rd and 1st order. Is that right? Certainly for the HP PLLXO I need to try both 2nd order (possibly with adjusted values) and also 1st order to see how they fare.


So I will test first with the Behringer (if I can put up with this hiss!). Just a quick extra question for when I do this, - When you drive both sections actively is the phase situation more or less of an issue then when you are using active for LP and PLLXO for HP? Or does it just depend on the orders you are using? Sorry if this is a noob question!

FURTHER UPDATE.
Okay tested the behrginer using these points. Put up with the hiss and the poor sound quality! (which really is poor in comparison to the great sounding PLLXO). Despite these two drawbacks I think this setup works a lot better, - 200Hz for the 3dB LP (butterworth) and 250Hz 2nd order for the HP (also Butterowrth) seems to work pretty well, no mid suckout like I have been experiencing Beseel 2nd order for the HP sounds too thin, only Butterowrth works well. I also tried 1st order Butterowrth 300Hz but that did not sound as good, - something wrong there, lacking lower midrange and sort of thin sounding.

The phase does not seem to change things when using the Behringer for both top and bottom despite whatever curves you use, - is that right? only inverted or normal phase make a difference.

So what do you reckon? Do you think I should build another HP PLLXO using 250Hz as the crossover point? and if so I'm not sure what type of slope to use? the Butterowrth/Bessel hybrid like you calculated before based on the stock or just straight Butterworth which seemed to work well on the test using the Behringer? If you reckon its a good idea is there any chance you could help me calculate the cap/resitors values again for this (sorry!, - then I'll owe you two big favours!)
Its a shame 1st order HP sounded no good, - would have been easier to build a PLLXO based on that.

I've not tried using 2nd order LP crossovers on the Behringer with these lower crossover points yet. I realise if I want to go all PLLXO it will be difficult to make a 3rd order crossover work well without getting it properly built with inductors. 2nd order is my only easy option
But if I can replicate what I just tried with the PPLLXO on the top (2nd order at 250Hz crossover point) , with 3rd order Butterworth on the Behringer, and it WORKS it would be a good to use for the time being until I can decide where to go. Like I said before I couldn't get 3rd order Butterworth LP to blend well with the HP PLLXO, - I guess because the crossover points were not low enough and not closely spaced enough? The midrange was too sucked out and when I increased the LP crossover point higher to try to make up for this it did not sound right, - again I guess because it was crossing over too high!

Anyway, so more progress, - the manual came in handy, - its seems weird that in the manuals for the MG3.3R and 3.5R they specify using different crossover points for active setup compared to the stock crossover, but it does seem to work! Like I say though in the MGIII and MGIIIa manuals the same stock crossover points are recommended for active operation.

Sorry for the long meandering message!!
All the best,
Colin

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