Bi-amped Acoustat

I just spent a while re-building 4 sets of interface for my 2+2's.
I went through all the mods I've seen here, the C-mod, a high voltage 0.22uf across the zener string, different values of final output resistor, from 100M to 500M.
The original design was just about spot on, all the latest "mods" dont really do much, give it a bit more tizzle if anything, which some will interpret as detail.
Even the original design with the 220uF crossover cap is pretty good, ( replacing the 220uF with a new piece brings it back to life, maybe the tales of it being necessary to replace with polyprop cap aren't exactly true)
A refurbished interface is about as good as you will get, whether its the old 220Uf design or the C-mod with 47uF polyprop.

BUT, there is a way to get a drastic improvement in clarity, open-ness, bass tightness and all round musicality, although in theory it shouldn't work.
Separating the inputs to bass and HF transformers, ie, providing two sets of speaker connectors and using two sets of amps, one for bass transformer and one for HF transformer, really makes the Acoustat a superb loudspeaker (which it already is, but now its even better.)

Now I know that the two transformers get blended at the HV section feeding the panels, and I agree that bi-amping shouldn't make any difference, but it surely does, and I just cant listen to the single amped version now.

I'm using very powerful amps, so I dont think its just a matter of doubling up with power, maybe it is, but whatever, if you get a chance to try this its very worthwhile.

But having said that, I have enormous respect for the original design and dont want to infer that there is anything wrong with it.

For me, bi-amping is the ultimate way to listen to Acoustats, despite my brain saying it shouldn't be so.
 

tyu

Member
2009-07-18 8:16 pm
Thanks for you input....I have done this ...for bi-wireing...not much to gain....that I hear....
BUT...don't get the added pos-neg 121 input post... revised....you can kill your amp an or kill a stepup trans...
heres my 2+2s interfaces as you see..... with 2 pr of post....
...The 2+2 are being ran with the Spectra 3 interfaces....full rang output only...
in this pic....
 

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Thanks for you input....I have done this ...for bi-wireing...not much to gain....that I hear....
BUT...don't get the added pos-neg 121 input post... revised....you can kill your amp an or kill a stepup trans...
heres my 2+2s interfaces as you see..... with 2 pr of post....
...The 2+2 are being ran with the Spectra 3 interfaces....full rang output only...
in this pic....

Yes I remember you saying it wasn't much of a gain for you, which is opposite of what I found, although I'm somewhat perplexed how it can make such a difference.
I'm big on sound-staging, imaging, all the 3D stuff , and it makes a big difference to that.
Yes it's a job for experienced acoustatophiles
 

tyu

Member
2009-07-18 8:16 pm
All that matters....is you feel your getting better ,diff sound.....vary cool... I too am All about the big 3D stage... that ESLs an ribbon do...
One big sound change for the better...was when I pull the high frc tran input off the fuse....that left only the bass tran on the fuse......this gives a much better topend for me.....................have fun
 
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Supra? Can you bi-amp the 2+2's with the stock interfaces? if so how? Like to try it myself. thanks

No, you have to modify the interface.
One thing i didnt mention is that by using two amps, and adjusting level of each amp, you can change the balance of bass and treble, thus making subtle or significant changes of tone.
I have the tone just a tad warmer than the single interface sound , to suitmy room and taste.
 

tyu

Member
2009-07-18 8:16 pm
I put two of my hafler Trans Nova P7000 amps 375wpc....running one amp pr interface......to bi-amp my 2+2 an the my M 3 Acoustat....your right..... it give one a lot more control on the tone....what not to like...next I well try run the Sunfire 300 amps with two diff tube pramps.... one for the top one for the bottom......I have one set of my 121 interfaces with the c-mod.....other with the first none crossover the 6 ohm new 220 cap....poly bypass.....for me I like the none c-mod best in the bi-amp or nom-setup.....lot fun
I have also done Soundlabs for bi-wire setup........
thanks for any an all input on getting better sound out of any ESLs...
 

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tyu

Member
2009-07-18 8:16 pm
Yes I hear ...what I call the ear candy eqing sound of the c-crossover....that what it is... a added crossover....
But I have the Spectra 3 ...an they use nothing on there input but a 1 ohm res....the 121 first 220 setup sounds a lot like the Spectra....but that's just my ears.....the sound of that c-mod 47-61mf cap can make a Big diff in sound....I stop at a 40mf Metallized Polypropylene in oil....with a 20mf Polystyrene.....but others will have diff....lot fun
thanks for your input
 

tyu

Member
2009-07-18 8:16 pm
It been so long ....on the stock M cable...cant be sure..it dose have a sound...I do know liked it better than the 12ga solid... romex type Roy uses in his mod....that's for sure...
I use for the pos input for the bass tran.... a 18gaTeflon siver coated stranded copper.....on the neg I use a 14 ga stranded copper pvc.....this for me give the best match with topend.....
All wires used on input for the topend tran right off the post no fuse... soiled 22ga copper in pvc....best sound so far...to day..right
 

tyu

Member
2009-07-18 8:16 pm
There one mod you may not have tried......I have the Spectra3s an 11..an in all there interfaces...an yes.... I know the tran are diff........but there tran center taps are floated off the bias board..... with wire wound 100 meg ohm res...10meg on the 11
So with my 121 interfaces...I have put one 20mg res were the center taps were on the bias board...an the center taps.....lets them float up.....sounds sweeter..fuller.....if you try this can your give your input on the sound....thanks
 

tyu

Member
2009-07-18 8:16 pm
Here as with Spectra 11 setup... see how there two center taps are move above earth-ground.. with the 10meg res......
I just do the same thing with the 121 high an low trans centaps......right at the bias board...
Leting the tran center taps talk to each others ..an not just be shorted out.... give more of that 3D...an better tone...
it can be put right back if you don't like the sound...thanks
 

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