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In Reply to: RE: Recomendations for subwoofer:Beveridge, ESL & USA Monirors posted by AJ on July 02, 2014 at 19:28:02
For a cost effective piece think of a pair of the Dayton Audio dual 12" closed box subs.
Are you using the Beveridge tube amps?
you can use a simple capacitor at the line level to cross over the ESL with a high pass and use the built in XO in the subs for the low pass.
Follow Ups:
Thanks... I have the model 3's that don't have an integral amp.
You can split the ESL element to bi-amp with internal passive cross over or eliminate the internal crossover and use an active crossover.
FWIW, I am in the process of evaluating (read: ugly build) a pair of dipole 8" subs using plate amps sitting on the floor beside them.
Mine use 8 inch woofers I bought from Thiel some time ago, started out as more of an experiment when I re-acquired my Quads.
Plan is to build a pair with 12's a la Gradient, but not to sit under the Quads.
The larger ones are sorta, kinda on hold cause the 8's are pretty spectacular...Bass fiddles sound like bass fiddles, I can hear the body of the tympanis, and the bass has real tone.
I am using an "antique" Dahlquist LP 1 crossed at 110 hz to the woofers.
There are Gradients around from time to time, and Dahlquist xovers which are still special, indeed.
Hi, it sounds interesting for an 8" dipole solution! Can you share with the team on some photos showing the build plan of such 8" dipole?
What kind of plate amp solution used? Does it has some EQ facility on the amp to do the front and back cancellation thing?
THanks.
Not ready for photos yet. Just a baffle cut for two 8's. One facing in, one facing out (as does the Gradient)) wired out of phase with each other.
Both the plate amp (Dayton SPA250) and the Dahlquist xover have EQ capability, although it does not seem to be needed so far.
I had boxes with two 8's, just basically cut the back and sides off the boxes, reversed one driver, left the top and bottom of the box.
I am surprised at the results so far. At this point the drivers are wired in series which does not set well with the plate amps on loud passages, since the drivers are both four ohm and the amps are seeing something around two ohms. Loud big drums, for instance kick off the amp protection.
Still very much in the "prototype" stage, but promising.
The line level capacitor will probably sound better than the internal high pass or an active crossover. It is just limited to the particular value of the power amp's input impedance.
The Dayton looks nice as a dipole, with EQ in the plate amp. I am also in a position looking for a subwoofer solution for the Quad ESL 2905.
I am reading into the Rythmik/GR solution offering.
http://www.rythmikaudio.com/GRci.html
It's a dipole based solution with a servo enabled paper cone drivers from GR. This is said to go down 14 hz, I heard some happy stories in Audio Circle.
Look forward to more interaction and discussion on this domain.
That Dayton subwoofer is a bipole configuration, not a dipole......two completely different things.For you Quads, a dipole woofer would probably be the best solution. 14Hz claims are pretty silly for any dipole configuration. If the cabinets are anything close to reasonably sized the equalization requirement and woofer excursions are massive to counter the front/back cancellation. If you acoustically separate the front/back by larger distances you can possibly achieve lower response but then the system starts to act less as a dipole and more like two separate sources that are out of polarity with each.
Your room will play a large factor with any type of woofer system when you get down to these frequencies.
Cheers,
Dave.
Edits: 07/04/14
The woofers in the Dayton sub can be rewired to act as a dipole too - in a near isobaric loading. The stock bipolar config should be very dynamic and would be pretty much a point source in the freq range it covers.
The dipole config would require some EQ to counter cancellation.
As Davey noted, the GR research sub, though a better fit than a bipole for an ESL, it is still going to be a dipole and you can probably get near flatness at low volume down to below 20hz due to EQ, I doubt that you would be able to get that extension at high volumes.
It's completely unworkable, and there's nothing Isobaric about that configuration since it would be open on both sides.
Anyways, the amplifier provided does not have the necessary equalization and you'd have a vibrating mess with all the excellent (inherent) force-cancellation of the stock bipole configuration completely undone.
Absolutely nothing wrong with that subwoofer system used in the conventional fashion. That's the way it was designed to work, that's the way it should be operated.
Dave.
Do you think it would do any better with one driver installed "inside out" rather than wired in reverse?
Obviously you are right about losing the vibration cancelling of the original bipole design, which is why it is so deep and tight and why I like recommending it.
Yes, you'd achieve a little bit of distortion reduction......but only if the bipole movement configuration is maintained. However, it would look ugly as hell. :)
OTOH, mounting the magnets inside the box (per the stock setup) would allow them to be physically coupled together inside with a piece of wood glued securely to both magnets (making sure not to cover any vents.) That would yield a marginal improvement to the force-cancellation configuration, but wouldn't have the even-order distortion reduction.
That's the way I would do it.
Dave.
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