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Longish story...
I have a 20 year old pair of Martin Logan Quests and am running in parallel with them a pair of VMPS standard subs. Both sets of speakers powered from the same set of Bryston 7 series monoblock amps. Bryan Cheney, when he installed these subs about 2 decades ago said no need for a separate crossover and set of amps for the subs, as running both direct from the same amps would work fine, especially given the power from the Bryston monoblocks.
I have been listening this way for years and it is OK, as the subs sound like they produce very little sound over the low bass.
Recently saw a used Bryston electronic sub crossover at a good price. I have an good 125 watt Parasound amp that I am not using so the only other major cost would be a set of cables to the crossover and another set to the subs.
Anyone experienced with this question? Between the Bryston crossover and the (expensive) cables to go from preamp to crossover and (reasonably cheap) cables to go to the sub amp, I am probably looking at about $1,500 or so. Your thoughts?
Thanks
Mark
Follow Ups:
I want to thank you all for the helpful comments. Truly appreciated and gave me some added insights.
Mark
Here is an inexpensive alternative to consider on this site.
Seems to good to be true. Similar to the X-Ray specs sold on the last page of comic books years ago. ;> )
Your crude analogy is not applicable here. Limiting a passive crossover to only one selected frequency significantly reduces complexity and cost.
Sorry, didn't know it was your site.
I have tried mating subs to stats with electronic crossovers to gain the inherent advantage of removing strain from the full range panels.
The problem for me: every electronic crossover I have tried (including the Bryston) imparted a haze or coloration that I could not live with even thought the flexibility of the active crossover had many advantages. The stats were just too revealing.
There are some pretty sophisticated crossovers available on the marketplace so I have not tried them all.
I found that a passive filter and subs worked best and am now trying something else-with some success- a pair of new RELs driving of the main amps speaker terminals with their in-built filter network. The REL solution sounds pretty good right now.
What electrostatics?- QUAD USA monitors, ESL 57s and a pair of Bevridge Model 3s ( these ones are spooky in what they do well).
Unfortunately, you are going to live with and try some options,I did , and spent a sum of money doing so that did not get me where I wanted to go. YMMV and all that.
Good luck.
Also try side wall placement of the subs...
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
nt
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
The 10B is a very good and flexible crossover and would allow you to take the deep bass load off the Quests and limit the higher frequency output of the subs so that they don't interfere higher up.
I think your plan is a good idea and you should consider something more powerful for the subs than the 125 WPC Parasound. Remember that you are driving these with big Bryston monos and you don't really know how much of their power the subs are sucking out. I would wager that the subs eat much of the power.
There are subwoofer amplifiers from Parts Express that you can buy at a reasonable cost. There are plenty of older amplifiers that will offer more power and better control of the subs.
You could just low-pass the subs with a passive network. No extra cables required. Finding the point and slope would be an issue.
E
T
A passive LP filter would not relieve the "strain" on the ML woofer but this may be okay for your setup. FWIW I run my Magnepans full with only a LP filter to the sub. However a passive line-level filter is essentially limited to 1st order as a 2nd order filter is hard to implement and in any case has a low Q ( <0.5) and may have substantial insertion loss. An active filter is the way to go.
Line-level biamping is a great idea but it is more involved than just throwing together some components that one has lying around. For one, the gain of the amplifiers need to be matched or compensated. Satie's recommendation is a good idea. An inexpensive Class D plate amplifier will probably give you better performance. Also while the Bryston 10B is a very nice device, it might be overkill for your application and less expensive crossover like a Rane might save you some bucks.
Edits: 07/30/15
'Stats can struggle in the deep bass, and this can have an impact further up.That is, it is possible that they would sound a lot better when fed a high-pass filtered signal, say from 40Hz up or higher.
In other words you might not know how to maximise the return on the crossover until you try it out.
Is there a low-pass passive filter built into each VMPS sub? If yes what is its -3db frequency?
What is the frequency range of the Bryston crossover?
If it gets down to say 30Hz or even 40 hz it might be possible to run just the low-pass side of the crossover and not use the high-pass side to feed a filtered signal to the existing amp's and your 'stats.
At least one sub maker - REL - used to recommend this approach.
The benefit there is that the feed to the Logan's does not pass through an extra line-level circuit. So that part of you system would remain as transparent as it is now. But the issue of over-excursion of the 'stats is still there.
Given it's a Bryston it is likely that it has 4th order Linkwitz Riley slopes. That increases the likelihood that it has just one pair of matching HP and LP slopes, OR a set of discrete frequencies with matching HP and LP slopes.
You might need to be pretty certain of at what frequency the Logan's roll-off in-room on their own and how quickly they die below that.
It might be possible to have the R and C of the filters changed to meet your needs.
If it's an old item it might be worth looking at upgrading the PSU at least.
I've linked this thread over to the planar asylum. Some folks there possibly have a pr of the same era Logans and can advise precisely about these issues.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 07/29/15
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