I was an Acoustat dealer along with Classe Audio. One of my favorite amps on the Acoustats was the DR-3VHC. What a wonderful combination! Brings back a lot of memories.
Please help me Acoustat Answer Man!
I am the original owner of these Acoustat Spectra 1100 speakers. I have a peak in both speakers which starts at 1400Hz, rises about 5-6 DB then returns to normal at 4200Hz. This causes all of my music to sound sharp and harsh, especially when a woman is singing and when a horn hits certain notes.
Is there a bias adjustment that will fix this problem, flattening out this hump a little bit and returning my speakers to the enjoyable speakers that they once were? Please help? Thank you
I am the original owner of these Acoustat Spectra 1100 speakers. I have a peak in both speakers which starts at 1400Hz, rises about 5-6 DB then returns to normal at 4200Hz. This causes all of my music to sound sharp and harsh, especially when a woman is singing and when a horn hits certain notes.
Is there a bias adjustment that will fix this problem, flattening out this hump a little bit and returning my speakers to the enjoyable speakers that they once were? Please help? Thank you
Not sure how you are making your measurements, as acoustic measurements of planar speakers can be difficult and the results misleading. But, you HEAR a problem that didn't exist before, so let's go with that. A properly working Spectra 1100 is not known to exhibit this anomaly. Did this start at the same time in both speakers? Although it's possible for both speakers to start acting up at the same time, it's unlikely, so your problem might not be the speakers.
I doubt adjusting the bias will solve your problem, but it's good thing to check to make sure the woofer output matches the output of the panel. Too high of a bias voltage could contribute to your issue, but I doubt it is entirely responsible.
Also check that the wires from the panel (terminated in pin plugs) are connected to the interface correctly (they are color coded). If you are feeding full range to the whole panel (as opposed to just half of it), and lows/mids to only half the panel (instead of all of it), this could play havoc with the frequency response. I've never intentionally mis-wired a pair, so I can't say for sure of the effect, but this is definitely something you should check.
I doubt adjusting the bias will solve your problem, but it's good thing to check to make sure the woofer output matches the output of the panel. Too high of a bias voltage could contribute to your issue, but I doubt it is entirely responsible.
Also check that the wires from the panel (terminated in pin plugs) are connected to the interface correctly (they are color coded). If you are feeding full range to the whole panel (as opposed to just half of it), and lows/mids to only half the panel (instead of all of it), this could play havoc with the frequency response. I've never intentionally mis-wired a pair, so I can't say for sure of the effect, but this is definitely something you should check.
I just used my air compressor on low to blow off the grills and the panel. So, I will set them back up where they have been for the last 30 years and listen for improvements. If that didn't work then I will have to buy a 1000:1 high voltage probe for my digital meter so that I can measure the bias voltage.
Come to think of it, originally when I purchased them I also purchased a Theta Data II CD Transport along with the Theta DS Pro Prime DAC. The sound according to reviews said that the Theta had a really deep bass. Yet, through the Acoustat's, which are known to have a bit of a bass boost and using my McCormack DNA-1 power amp, the bass was not boomy and the sound was pristine. About 10 years ago I had trouble with the laser on my Theta and had it replaced at the Theta factory. When I received it back, the sound was totally different. The bass was boomy and there was a rise in the region that I mentioned. I borrowed a friend's spectrum analyzer to confirm this. I suppose that the original laser was a beautiful anomaly. Because it seems to me, that laser had the frequency response dips and peaks that made the Acoustat's sound so natural. Detailed, yet not bright or harsh.
But, ever since the laser replacement, the harshness is there and getting worse.
So much so, that I haven't listened to them in quite a while.
Originally, when my friend measured the speakers after the laser change, there was a 3-4 db rise in response, although the Stereophile review shows 1-2db, using pink noise, between 1400Hz and 4200Hz. But, now 10 years later when he measured, the peak rise in that same region is 5-6 db. I have tried at least 11 different CD players and DACs, but the peak remains. Different players only having an effect of either fuller or thinner sounding vocals with the harshness still there.
I've brought my Amp at the shop and had bias and other adjustments checked and everything was right on. So, I will let you know how they sound after I've put them back together after cleaning.
And if they are the same, then I will purchase a 1000:1 high voltage probe for my meter and adjust the bias. Hopefully this works
Come to think of it, originally when I purchased them I also purchased a Theta Data II CD Transport along with the Theta DS Pro Prime DAC. The sound according to reviews said that the Theta had a really deep bass. Yet, through the Acoustat's, which are known to have a bit of a bass boost and using my McCormack DNA-1 power amp, the bass was not boomy and the sound was pristine. About 10 years ago I had trouble with the laser on my Theta and had it replaced at the Theta factory. When I received it back, the sound was totally different. The bass was boomy and there was a rise in the region that I mentioned. I borrowed a friend's spectrum analyzer to confirm this. I suppose that the original laser was a beautiful anomaly. Because it seems to me, that laser had the frequency response dips and peaks that made the Acoustat's sound so natural. Detailed, yet not bright or harsh.
But, ever since the laser replacement, the harshness is there and getting worse.
So much so, that I haven't listened to them in quite a while.
Originally, when my friend measured the speakers after the laser change, there was a 3-4 db rise in response, although the Stereophile review shows 1-2db, using pink noise, between 1400Hz and 4200Hz. But, now 10 years later when he measured, the peak rise in that same region is 5-6 db. I have tried at least 11 different CD players and DACs, but the peak remains. Different players only having an effect of either fuller or thinner sounding vocals with the harshness still there.
I've brought my Amp at the shop and had bias and other adjustments checked and everything was right on. So, I will let you know how they sound after I've put them back together after cleaning.
And if they are the same, then I will purchase a 1000:1 high voltage probe for my meter and adjust the bias. Hopefully this works
Something placed behind the speakers like a big TV set? This could reflect this part of the audio spectrum (planar speakers need more attention placing them in the room as reflections are difficult to avoid). I cannot think of any electronic cause other then your audio source has a defect (measure first what is presented to your speakers).
Hello Acoustatanswerman, I’m going to buy a pair of model 4 and hopefully they will arrive safely here in ITALY. The Mk- 121 2 are set now to 117V and I would like to know if I’ll be able to have them working on 220V by changing wiring. I also noticed that some Mk- 121 2 have integrated power cords and other have not the power cords attached and you can use yours.
Many Thanks for your help. Alex
Many Thanks for your help. Alex
rufusen - Acoustat bias transformers are configured for a single mains voltage. If currently configured for 117V, they cannot be re-wired for another voltage. To operate directly from 220V, you'd need to change the bias transformer, which would be very difficult to find now.
However, since the power consumption of the speakers is minimal (a few watts), you can use a step-down transformer from convert from 220V to 117V (more likely labelled as 220 to 120V). These transformers are inexpensive, and if desired, you can use a single step-down transformer for both speakers.
However, since the power consumption of the speakers is minimal (a few watts), you can use a step-down transformer from convert from 220V to 117V (more likely labelled as 220 to 120V). These transformers are inexpensive, and if desired, you can use a single step-down transformer for both speakers.
A Model 8 is NOT the same as a stacked-pair of Models 4s. The low frequency transformers (2 per speaker) used in the Model 8 have a lower turns-ratio, which yields less bass boost. This is to compensate for the increased panel area, which would otherwise produce too much bass for most tastes.
So yes, you can do as you propose, but you may find the bass response too much for your liking. Depending on your set-up, you may be able to introduce external equalization to compensate for the exaggerated bass. These same comments apply to the idea of stacking two Model 3s to produce a Model 6.
Also consider that it's not a great idea to parallel two interfaces on one amplifier channel, so you will need four channels of amplification. This is normal practice for the standard Model 8 (or Model 6) which has two interfaces per speaker. Don't try to drive more than four panels from one interface.
So yes, you can do as you propose, but you may find the bass response too much for your liking. Depending on your set-up, you may be able to introduce external equalization to compensate for the exaggerated bass. These same comments apply to the idea of stacking two Model 3s to produce a Model 6.
Also consider that it's not a great idea to parallel two interfaces on one amplifier channel, so you will need four channels of amplification. This is normal practice for the standard Model 8 (or Model 6) which has two interfaces per speaker. Don't try to drive more than four panels from one interface.
These informations are very helpful to avoid disasters, I really appreciate. If I understand correctly there is no way to modify the standard interfaces 121 -2A of the model 4 to make them produce less bass, correct? Yes, it can be managed by a processor but it will introduce a higher level of complication in the setup, however it seems that sometimes you have to accept it.
There is a way to modify bass response by adjustment of the low frequency transformer tap. However, for the Model 4, you will already have that set on the YELLOW position, which yields the minimum bass equalization. For most tastes, that will be too much for an 8-panel system. Beyond the LF tap, there is no method of reducing bass response.
A little side note:
Can the transformers of the Acoustat hv power supplies be connected in series in case these are shipped from the US to Europe ? In this case no change need to be made except some little wiring. And if done with care it should work i would say.
I am not talking about the amplifiers here but merely the passive units.
Can the transformers of the Acoustat hv power supplies be connected in series in case these are shipped from the US to Europe ? In this case no change need to be made except some little wiring. And if done with care it should work i would say.
I am not talking about the amplifiers here but merely the passive units.
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Stacking them that way will depend on total height achieved - is your ceiling high enough? I suppose you could do that for experimental purposes, and if you like the result, then build proper 8-panel frames. With 8 panels, I think you'd get the best results with the bottom panels essentially at floor level, as was done with all "stacked" Acoustat models. These models were 7-feet,10-inches tall, barely able to fit a standard 8-foot ceiling.
I would not recommend series-connecting the bias transformers. You may (and probably will) run into grounding issues, and the voltage may not divide evenly between the two transformers. Far better to use a 240/120V step-down transformer - it doesn't need to be very big (figure about 5 watts per speaker).
I would not recommend series-connecting the bias transformers. You may (and probably will) run into grounding issues, and the voltage may not divide evenly between the two transformers. Far better to use a 240/120V step-down transformer - it doesn't need to be very big (figure about 5 watts per speaker).
I made frame drawings for the Spectra models when I was employed at Acoustat. Not sure if I ever made drawings for the older models. In any case, I no longer have access to those drawings. I would suggest developing a drawing based on the panel arrangement in your Model 4, and build UP from there.