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Old 23rd February 2013, 11:23 PM   #541
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Join Date: Feb 2008
Location: Jackson,michigan
When using a bridged amp configuration the impedance that each amp see's is half of what the load is.

It is common for ESL setups to get down to a 2 ohm impedance (or lower) at 20Khz.
Therefore each amp would be seeing a 1 ohm ( or less) load on them at 20Khz.
Some amps can handle this but most don't, and, they don't like this type of situation at all.

At the lower frequency's this is okay as the impedance is much higher, typically below about 10Khz to 5Khz as long as you stay away from transformers core saturation point.

Bridging an amp also doubles its output voltage so if your interface is design to go as low as 20hz with a certain amount of voltage, you must now have to limit the input to the interface at 40Hz if you plan on cranking higher than you would if you were using a single amplifier.
Otherwise would it saturate the interfaces transformer core and this too will cause distortions and overload the amplifier.



Last edited by geraldfryjr; 23rd February 2013 at 11:32 PM.
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Old 23rd February 2013, 11:33 PM   #542
tyu is offline tyu  United States
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A,b C mods have nothing to do with the Bias....i am just give u info i have found after 30 years of owening Acoustats.....Xs..1+1s..2+2s M2s.. M3..M4..Sp 11...1100...
The new bias is low cost an one way to get the best sound out of any esl.....good luck ....glad thay sound great...
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Old 24th February 2013, 07:59 AM   #543
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Location: Burgundy, france
Lucky guy who could get a pair of 2+2... Seem great speakers.
Have a look to the EHT supplies on
Audio Transformer
Tremendous improvement on my 1+1's.

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Old 24th February 2013, 01:30 PM   #544
tyu is offline tyu  United States
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Acoustannoy...........Thanks for the link.........yes the outboarding of the bias in All Acoustats well give more than a new the best thing for any the Acoustats...
In the Stock setup evey time the base tranfourmer get a big base pulls the bias down...what 4-5kv less than 1" from the base the high fre caps...jim would have done it diff....but it cost....we got the deal...Acoustat panels have lasted an still sound great...just littel lov an man...theres not much better...i drive my M3 with a 60year old 50watt tube amp...90-100db output with a bias i can set....
Long Live Acoustat
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Old 24th February 2013, 05:28 PM   #545
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Join Date: Feb 2013
What size (gauge) speaker cable do you use with your Acoustats?
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Old 24th February 2013, 06:34 PM   #546
tyu is offline tyu  United States
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Join Date: Jul 2009
I use two run per + an two -- 24ga solid copper....sweet sound with tubes are Sand amps...well to me...
i got a lot of wire here. 10ga 12ga 14ga was one of the best size wize for sound...when i buy speakers people give the stuf...i was useing Purist Audio... water jacketed wire with my Krell an Apogee setup think it 14ga...out of all for years of diff wire the small sounds best with any of my setup...Now some go to small for me like 36ga but thats about the wire in the Magnepans voice i dont care for the sound..
lot money spent... this 24ga cost the less an sound better....gofig...
but wire is a tuff call i would never say for others.
....lot buzz about coax for ESLs...good luck
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Old 25th February 2013, 05:32 PM   #547
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Join Date: Feb 2013
Well, i finally got the 2+2's dialed in. I called in my 19 year old daughter, who has excellent ears.
I had her sit in what would be my place on the couch, and then unplugged the right speaker.
I told her to tell me when the sound sounded best. I turned the left slowly and then she said "go back!'. I turned it the other and she yelled "Stop!". I repeated this on the other side.
It actually worked, sounded pretty full.
I noticed when using MCAAC room correction (probably goes for any room correction scheme) that if the speakers are not aimed correctly, the MCAAC will up the frequencies above 1.5khz.
If the speakers are aimed correctly, it will subtract a little from some of the higher frrequencies and add a little to lower, like a small bump at 40hz.
Sounds great now!
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Old 5th March 2013, 08:13 PM   #548
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Join Date: Mar 2013
Highs either lost or severally attenuated on 1 panel, switched panels, same thing so problem not in arrays but in crossover/pwr supply interface (MK-2123) low freqs may also be attenuated when compared to other interface. When switching panels, the good interface gave a nice spark when discharged but the faulty interface did not spark.

Looking at the meters on my amp (Mac), both channels are outputting the same power to speakers but bad interface has substantially reduced output (volume).

I figure that the problem lies in the bias supply, but then I am no expert and I only fool around when something is not working correctly.

Your thoughts would be appreciated.

Bob Riddle

The schematic I have for MK-2123, rev 1. 5/29/91 does not appear to be exactly like my MK-2123. My schematic shows no fuses in the power line-in but the interface as internal fuses on each leg. From going thru the forum, the 15v ac input which I originally thought a misprint actually is for an upgraded pwr/crossover interface. I have yet to find a schematic for my interfaces.
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Old 6th March 2013, 03:12 AM   #549
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Location: St-Catherine Quebec
Originally Posted by tyu View Post
I for one dont like the sound of any bridged amps on any speakers,most have a chip in the input for bridging. cost about 50.cent ...
The 121 interfaces are over 30 years old...Just littel you got some of the best ESLs at any $$$
An the Bias needs to be re-worket most likely...just new diodes an cap in the bias well give more output...
Any amp that wont give you the output you need unbredged.... I would not put on any of my ESLs interfaces transfourmers .... Acoustats...old are new
Others have there input ... there tons of info on Acoustat here....
good luck
Just one man o-pine....... Long live Acoustat
Yes tyu, Acoustat's may be OLD but for me they are still #1 bang for the buck speakers. - - - Long live Acoustat's. - - -
Chord CPM-2600 amplifier - Chord One cd player - Acoustat 1+1 speakers -
Life without Acoustat is possible BUT senseless.
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Old 6th March 2013, 03:14 AM   #550
mortron is offline mortron  Canada
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Location: Town
Originally Posted by MrAcoustat View Post
Yes tyu, Acoustat's may be OLD but for me they are still #1 bang for the buck speakers. - - - Long live Acoustat's. - - -
I clicked this thread thinking, I wonder if AAM was Andre... I guess I was wrong
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