I've never encountered an ultrasonic bias power supply that didn't work properly with the published values. A first time for everything, unless of course you have a bad component somewhere. If necessary to obtain the correct HV output, it is permissible to increase the zener voltage a bit. Keep in mind that the accuracy of measuring the bias will vary greatly with the method used. The desired result (regardless of what you measure) is that 1) both speakers produce the same bias voltage, and (2) that the setting of the HV yields an acceptable balance between ESL and woofer. Also make sure the board is fully installed in the chassis, as the proximity of the metal chassis will slightly affect the bias voltage.
The Spectra series benefits from a number of evolutionary improvements in Acoustat’s product lifecycle.
Higher resistivity coating, yielding more dynamic capability (i.e. less ‘crackling’ on loud bass notes). Later non-Spectra models also used this coating, but there a very good chance that any Model Two will not have this improved coating.
Improved audio transformers: the Spectra transformers are a different type of construction using better insulating materials. This makes for a more reliable transformer (less chance of over-driving failures).
Improved stereo imaging, thanks to Spectra’s segmented construction and resulting dispersion pattern.
All of these things combined mean that the Spectra 22 (or 2200) is a vastly improved product compared to any Model Two. Adding to its technical superiority, any Spectra 22/2200 will be years younger than any Model Two, adding to its longevity.
Replacement panels (or any other parts, for that matter) are available only on a “used basis”, as they are no longer being manufactured. In that respect, a Model Two and Spectra 22 have equal chances of being repairable.
Higher resistivity coating, yielding more dynamic capability (i.e. less ‘crackling’ on loud bass notes). Later non-Spectra models also used this coating, but there a very good chance that any Model Two will not have this improved coating.
Improved audio transformers: the Spectra transformers are a different type of construction using better insulating materials. This makes for a more reliable transformer (less chance of over-driving failures).
Improved stereo imaging, thanks to Spectra’s segmented construction and resulting dispersion pattern.
All of these things combined mean that the Spectra 22 (or 2200) is a vastly improved product compared to any Model Two. Adding to its technical superiority, any Spectra 22/2200 will be years younger than any Model Two, adding to its longevity.
Replacement panels (or any other parts, for that matter) are available only on a “used basis”, as they are no longer being manufactured. In that respect, a Model Two and Spectra 22 have equal chances of being repairable.
Thanks for the thorough reply.
What if one had a panel failure on a Spectra model, and couldn't find another Spectra
"donor" to purchase to use to replace the defective one.
Can one use a panel from a non Spectra model?
I realize the panel from a different model other than "Spectra " are wired differently, so one wouldn't have the benefits of the improved imaging and coating material that allow for higher SPL's, etc......but would the speaker actually function this way, or would the transformers have to be modified to accommodate the different panel?
One final thought...if the speaker would actually function with the " different ' panel, would the fact that the one panel that would still be using a Spectra panel, versus the replacement panel from the older series create imaging issues?
What if one had a panel failure on a Spectra model, and couldn't find another Spectra
"donor" to purchase to use to replace the defective one.
Can one use a panel from a non Spectra model?
I realize the panel from a different model other than "Spectra " are wired differently, so one wouldn't have the benefits of the improved imaging and coating material that allow for higher SPL's, etc......but would the speaker actually function this way, or would the transformers have to be modified to accommodate the different panel?
One final thought...if the speaker would actually function with the " different ' panel, would the fact that the one panel that would still be using a Spectra panel, versus the replacement panel from the older series create imaging issues?
Generally speaking, a Spectra speaker needs a Spectra panel. This is due to the segmented stator, it's corresponding wiring, and the special equalization and filtering applied to each segment. The only exception to this is for 3-panel-wide Spectra models (Spectra 3, 33, 3300, 66 and 6600), where the outermost panel of each speaker has both segments driven equally (i.e. low frequencies only). For this outermost panel, one could use a non-Spectra panel as a replacement. Depending on the vintage, that replacement non-Spectra panel may or may not have the improved coating.
However, it is possible to use a Spectra panel in any non-Spectra model, simply by wiring the two segments together.
The very different nature of how the panels are driven for non-Spectra vs. Spectra models makes any conversion of the driving electronics from one to the other version quite impossible.
However, it is possible to use a Spectra panel in any non-Spectra model, simply by wiring the two segments together.
The very different nature of how the panels are driven for non-Spectra vs. Spectra models makes any conversion of the driving electronics from one to the other version quite impossible.
Before I change anything else after refurbishing the Spectra 1100 and measuring the HV at maximum potentiometer setting at 3.2 Kv I should note this measurement was at the speaker end of the new 500 Meg 1 % resistor. The Fluke HV probe is 1 Gigohm 1% in impedance so the voltage divider would say the supply was actually 4.8kv at the end of the diode string and should be turned down to the recommended 4.3 kv. So be careful where you measure and use a proper HV probe.
Do you have a Weak Panel? - Acoustat Troubleshooting
I realized something when I was looking over the troubleshooting guide that I wrote. (Posts #2,978 and 2979.) It occurred to me that people may NOT KNOW they have a weaker panel. I do not believe this is a common situation but it is good to be aware of the possibility.
One possible clue is when you cannot get mono music to exactly "center" unless you tweak the balance knob off-center. This assumes your distance to them and the angles of both speakers is the same, and the speakers are symmetrically arranged in the room, same distances to the side and back walls, etc.
Now the “off-center” problem can be in your system: swap the speaker cables at the amp OR at the speakers (not both) to determine that. If the problem swaps it is in the system somewhere.
I found I needed to put my ear up close to each panel in order to detect those that were weaker. I did this a few times from the front and the back to be certain before I thought about doing any troubleshooting or repair work. Put on some music with lows, mids, and highs. A comfortable volume level will work. You don't need high volume as you are listening for differences from one panel to the next.
Of course if you have Spectras you will get different frequency balances as you move along. But you can also compare one section to the same section on the other speaker. Put it on mono or play mono material, and remember they are mirror image speakers.
The probable causes and fixes for a weak panel are given in section 4 of the Troubleshooting Guide.
I suppose that a loose diaphragm might cause this as well, but that is known to cause other problems, such as loose (indistinct, flabby) bass. See section 2 of the Troubleshooting Guide.
If you check all the above and you find that the whole speaker is weak (all panels) see section 5.
I hope this helps.
Brandon
I realized something when I was looking over the troubleshooting guide that I wrote. (Posts #2,978 and 2979.) It occurred to me that people may NOT KNOW they have a weaker panel. I do not believe this is a common situation but it is good to be aware of the possibility.
One possible clue is when you cannot get mono music to exactly "center" unless you tweak the balance knob off-center. This assumes your distance to them and the angles of both speakers is the same, and the speakers are symmetrically arranged in the room, same distances to the side and back walls, etc.
Now the “off-center” problem can be in your system: swap the speaker cables at the amp OR at the speakers (not both) to determine that. If the problem swaps it is in the system somewhere.
I found I needed to put my ear up close to each panel in order to detect those that were weaker. I did this a few times from the front and the back to be certain before I thought about doing any troubleshooting or repair work. Put on some music with lows, mids, and highs. A comfortable volume level will work. You don't need high volume as you are listening for differences from one panel to the next.
Of course if you have Spectras you will get different frequency balances as you move along. But you can also compare one section to the same section on the other speaker. Put it on mono or play mono material, and remember they are mirror image speakers.
The probable causes and fixes for a weak panel are given in section 4 of the Troubleshooting Guide.
I suppose that a loose diaphragm might cause this as well, but that is known to cause other problems, such as loose (indistinct, flabby) bass. See section 2 of the Troubleshooting Guide.
If you check all the above and you find that the whole speaker is weak (all panels) see section 5.
I hope this helps.
Brandon
It's been a long time since I spent much time in this forum, but I'm still loving the Acoustat 2+2's I upgraded to in 2019 after using 1+1's for the previous 10 years. I'm also loving the Hafler 9300 Amplifiers both on the Acoustats and on a pair of Revel M20's in my kitchen. It's a wonderful amplifier that is much cleaner than about anything made before it's time, and I like the fact it doesn't have series capacitors or servos or relays or current limiters or stuff that wears out in a short time. It's also the perfect amount of power for both 1+1's and 2+2's, anything more is wasted.
My pair of 2+2's has the original transformers, but the C mod. Except I mistakenly changed one HF transformer to medallion during a repair and haven't bothered to change back. (The issue was elsewhere.)
Now I have an opportunity to buy some more Acoustats, 1+1 and 2+2, both with Medallion transformers, which I'm planning to take. The panels may be in better shape than the ones I have too.
How exactly are Medallion transformers different anyway? I would expect it's a winding with better coupling, which probably translates to lower distortion. Some guy was claiming that only the HF medallion transformer made significant difference, but I wonder if that's true (given the better coupling hypothesis). He said Medallions also didn't overload as well. I wonder about that, it's possible that a tighter winding might have slightly harder clipping so to speak. Hence (and for other reasons) the C mod is a good idea (and I'm going to modify anything I get to C mod if it isn't already asap) because it limits low frequencies to the HF transformer better.
Is it still possible to order Medallion transformers?
My pair of 2+2's has the original transformers, but the C mod. Except I mistakenly changed one HF transformer to medallion during a repair and haven't bothered to change back. (The issue was elsewhere.)
Now I have an opportunity to buy some more Acoustats, 1+1 and 2+2, both with Medallion transformers, which I'm planning to take. The panels may be in better shape than the ones I have too.
How exactly are Medallion transformers different anyway? I would expect it's a winding with better coupling, which probably translates to lower distortion. Some guy was claiming that only the HF medallion transformer made significant difference, but I wonder if that's true (given the better coupling hypothesis). He said Medallions also didn't overload as well. I wonder about that, it's possible that a tighter winding might have slightly harder clipping so to speak. Hence (and for other reasons) the C mod is a good idea (and I'm going to modify anything I get to C mod if it isn't already asap) because it limits low frequencies to the HF transformer better.
Is it still possible to order Medallion transformers?
I myself was predisposed against Acoustat 2+2's before hearing them. After hearing them, I realized what had been accomplished. They found an angle for the two panels such that beaming in the center (the issue with the flat panel front 1+1's) is virtually eliminated. You get the benefits of a curved driver without the compromises needed to do that with electrostatic panels.
If you are right on the beam of an electrostatic, it's very uncomfortable to listen to and sounds worse in many ways. Slight head movements result in massive shifts of image and brightness.
Anyway, the optimal way to listen to any flat speaker is not directly on-axis. Electrostatics sound especially bad that way. Electrostatics are best towed slightly outwards of being on ear axis, to minimize crosstalk with the other channel, and to slightly tame the top end without dialing down the room response too much. With the 1+1's I found the optimal position was WAY off ear axis, 10 degrees or more, to get away from any kind of beaming. The ear-axis sound is then much duller than the room response when the brightness is adjusted right. WIth the 2+2's, the optimal position is only slightly off the ear axis because the angled drivers eliminate beaming. Then the ear-axis sound is near identical to the room response. The angled drivers also mean there is better imaging as the source better approximates the line source. A completely flat driver the width of the 2+2's would be terrible (unless electronically compensated as in Spectra).
The manual also advises slight off axis towing of the speaker.
Overall it's an amazing speaker which was under appreciated in it's time and perhaps now because it's trickier than most to deal with.
have you (or anyone else) tried toeing them in the same amount, but instead of crossing them slightly to the outside of your ears, cross them over slightly in front of your ears? i've found this to work quite well with many "normal" speakers. it also widens the "sweet spot", as if you're off center, the speaker further from you is providing a more direct sound than the speaker closest to you. some mfr's actually recommend this - i know vmps did, for one, w/its ribbon towers.
thanks,
doug s.
thanks,
doug s.
As I've mentioned, I tried every way. The way I have them is when the image melds and becomes holographic. It fades in and out within just a degree of toe in or out. I'm not sure how precisely my ears are on the intersection but it's very close. I hear a much bigger difference moving my head forward to back than side to side.
Hello all.
Few weeks ago I have got 1 pait Acoustat MK141-C speakers. I'm not expert I'm full layman in this hifi topic. I would like to buy one amplifier what would be good for these rare elektrostatic speakers. Very importatn info, that I have enough hobby
thats why I dont want buy amplifier very high price. Is it possible I'm looking for something about 1000-1500 USD. I hope you are understand my situation and can offer me something. I'm looging for the internet but this topic is very difficult one layman. Now for example I looked this pair Emotive PT-100 with A-300. But the Advanced Acousctic Smart BX2 is would be good for me. BUT - I don't know what parameters have to watch when I look for amplifier for the MK141. Added info for you that I have only one Google Chromecast Audio Media Streamer - RUX-J42 music source. I would like to thank yopu for your help
Few weeks ago I have got 1 pait Acoustat MK141-C speakers. I'm not expert I'm full layman in this hifi topic. I would like to buy one amplifier what would be good for these rare elektrostatic speakers. Very importatn info, that I have enough hobby
thats why I dont want buy amplifier very high price. Is it possible I'm looking for something about 1000-1500 USD. I hope you are understand my situation and can offer me something. I'm looging for the internet but this topic is very difficult one layman. Now for example I looked this pair Emotive PT-100 with A-300. But the Advanced Acousctic Smart BX2 is would be good for me. BUT - I don't know what parameters have to watch when I look for amplifier for the MK141. Added info for you that I have only one Google Chromecast Audio Media Streamer - RUX-J42 music source. I would like to thank yopu for your help I've been running a YBA Integre DT (integrated amp) into Model 3s and 2+2s for about 25 years and I have little urge to upgrade. It's incredibly transparent and revealing with no perceptible colouration and very importantly can deliver current with a damping ratio of about 300. If I were up to upgrade, it might be to a YBA Passion series. DTs are available under US$1000 and are hard to beat at that price.
Why don't you buy one that was designed for it? Jim Strickland's Trans-Nova Twin 120 or 200 would fit thew bill.Hello all.
Few weeks ago I have got 1 pait Acoustat MK141-C speakers. I'm not expert I'm full layman in this hifi topic. I would like to buy one amplifier what would be good for these rare elektrostatic speakers. Very importatn info, that I have enough hobby
Maybe you all right Disco-Pete. But I think very small the opportuniti to find this modell.
Acoustat Trans Nova Twin-120 Pure FET
or
Acoustat Trans Nove Twin-200
Acoustat Trans Nova Twin-120 Pure FET
or
Acoustat Trans Nove Twin-200
They are not rare. If you have a bit of patience, one will come up sooner than later. I see them regularly. The 120 is a better amp than the 200. I've used them both. Both are great amps but the 120 has a blacker backround.
