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#2,942
The MK-121 series of interfaces (all variations) is designed to drive a maximum of 4 panels. Increasing the number of panels will provide more bass (probably too much for most tastes) and increased HF roll-off (probably too much for most tastes) due to the increased capacitive load of the additional panels. This is why the Models 6 and 8 used two interfaces per speaker, with different LF transformers and different RC combiner values.

Simple answer: you won't hurt anything, but it's not advisable as you probably won't like the result (especially frustrating after doing all that work).
 
#2,944
AcoustatAnswerMan said:
The MK-121 series of interfaces (all variations) is designed to drive a maximum of 4 panels. Increasing the number of panels will provide more bass (probably too much for most tastes) and increased HF roll-off (probably too much for most tastes) due to the increased capacitive load of the additional panels. This is why the Models 6 and 8 used two interfaces per speaker, with different LF transformers and different RC combiner values.

Simple answer: you won't hurt anything, but it's not advisable as you probably won't like the result (especially frustrating after doing all that work).
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Andy, sorry to bother you! Did the model Six & Eight use (1) regular interface and (1) special interface or (2) of the special ones? I think I sold maybe a pair of two, but didn't install either one, so I can't remember. THANKS!!!
 
#2,947
AcoustatAnswerMan said:
Hello Audio Enthusiasts! Some of you may know my work on www.audiocircuit.com, where for many years I have been helping to advise Acoustat owners. I was an engineer and manager with Acoustat, starting when the David Hafler Co bought Acoustat out of bankruptcy, right up to the very end of US production under Rockford Corp ownership (sad day that was!). So I thought I'd lend a hand here, too, because I LOVE Acoustats and want to help as many owners as possible to keep their Acoustats running for many years to come. I don't sell parts or do repairs, but my advice is FREE! So let me know how I can help YOU with your ACOUSTAT's! (And this being a DYI crowd, I don't mind discussing modifications to the speakers.)

Andy Szabo
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Hello Andy. We worked together at Acoustat in Tempe. My name is Bud Lewis. I still have the pair of spectra 3300s and subwoofer. I have them in the storage. They are too large for my living room, and considering selling them. any thoughts of where I could do that?
 
#2,949
BudLewis said:
Hello Andy. We worked together at Acoustat in Tempe. My name is Bud Lewis. I still have the pair of spectra 3300s and subwoofer. I have them in the storage. They are too large for my living room, and considering selling them. any thoughts of where I could do that?
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Bud, how much do you want for them? Where are you located? Thanks! Wood finish and fabric color please. Thanks again.
 
#2,952
conqueeftador said:
Just picked up a pair of Spectra 1100s. The power supply that came with it is broken, this was a 13v isolating PSU. Looking around it seems power is either 12 or 15v. How do I know what is needed?
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I bought 2 of these for my Spectra 66, would recommend, even has the acoustat logo on it. Link to ebay
If you need to get something working while you wait, any 12-15v AC or DC wall wort should work.
 
#2,954
Just tried 12v DC and they have some life. Seems a bit dull on the mid/highs though.


Found this re power supplies:

There exists some confusion over the wall transformer required for the Ultrasonic Bias Power Supply used on the Spectra Series. This is not surprising, as Acoustat did use various wall transformers, depending on vendor supply, and when they were built. The earliest supplies used a 12 volt AC transformer, and later supplies used a 15 volt AC transformer. I don't recall that Acoustat ever used a wall transformer with a DC output. They were always 12 - 15 volts AC, with the 15-volt model used more predominately. The 15-volt supply provided better regulation under low line conditions. The schematic of the 2200/3300 interface shows the interface wired for 15 VAC input. Note the 470-ohm resistor in series with the zener diode. This resistor is a correct value for 15 VAC input. If you use a 12 VAC transformer, this resistor is 100 ohms. If you have an older speaker with 12-volt AC transformers, there is no need to upgrade to the 15- volt AC transformers as long as everything is functioning normally. If the wall transformer needs to replaced, and you are not sure of the required voltage, check the value of the above mentioned resistor. The replacement transformer should have a current output of at least 150 mA.
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#2,958
Should I Add an EMI/RFI Cap to my Acoustats?

I have Model 3's.
I was thinking to add a capacitor after the fuses, across the AC power in, which goes to the high voltage bias supply transformer. The interface is plugged into a power conditioner. This is to add a last filter on the incoming AC line and to help filter any noise from the bias supply going back to my power conditioner or AC line and thence to other components. I was thinking of a polypropylene cap, around 0.1 uF, safety Class Y2 * (In failure mode it opens, not a short circuit).

I had first selected a capacitor with longer leads, but it's not in stock. So, with lower ESR (electrical series resistance) than a less expensive one (lower is a good thing), this cap I can make fit:
EPCOS-TDK B32023B3104K000
https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B32023B3104K000/3489494

Have you tried this?
What was the result?
Is there any downside to doing this?


Note: also in this bias circuit I am planning on adding the snubber circuit after the transformer, per the thread:
Transformer Snubbers See posts 1, 25.
(Linked to from Post 2,176 of this thread.)

I do not think the snubber will interact (much) with what I propose, which has a different purpose. But I am not an EE, so I am asking.


Brandon


* Note: I found a good explanation of Class X and Class Y capacitors here:
https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/
 
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