Summarizing your troubleshooting steps thus far:
1) It’s in the interface, NOT the panel or wiring.
If I read all your posts correctly, you have isolated the problem to the HV 500Meg resistor or a solder joint on the resistor or bias voltage pin terminal. Both are uncommon, but I have experienced them at least once in the past 20 years.
Since you replaced the caps and diodes I’m guessing you inspected the back of the board and didn’t notice any cold or corroded solder joints on the 500Meg resistor. So next time you experience the loss in volume, try bypassing the resistor with an alligator clip jumper and see if that brings it back to life.
1) It’s in the interface, NOT the panel or wiring.
2) It’s NOT the bias transformer or fuses.
3) It’s NOT the diodes or caps in the multiplier.
If I read all your posts correctly, you have isolated the problem to the HV 500Meg resistor or a solder joint on the resistor or bias voltage pin terminal. Both are uncommon, but I have experienced them at least once in the past 20 years.
Since you replaced the caps and diodes I’m guessing you inspected the back of the board and didn’t notice any cold or corroded solder joints on the 500Meg resistor. So next time you experience the loss in volume, try bypassing the resistor with an alligator clip jumper and see if that brings it back to life.
I agree with bolserst's analysis. Although the 500-Mohm resistor is rarely the culprit, it does seem like you've eliminated all the other more common possibilities. So check the solder connections on that resistor and on the red pin-jack. If all looks good there, I would swap out the resistor.
One note of caution: the idea of bypassing the resistor to see if the volume returns is a good one, but should be done only briefly and at low volume.
One note of caution: the idea of bypassing the resistor to see if the volume returns is a good one, but should be done only briefly and at low volume.
Acoustat Felt Pads
The purpose of the felt pads attached to the rear stator of all Acoustat panels is to provide acoustic damping for the diaphragm’s low frequency, high-Q resonance. Ideally this damping would be achieved with no effect on the midrange and highs. For some time I have been wanting to measure and find out how close the Acoustat damping solution comes to the ideal. Comparison of other damping methods can be found here: http://www.diyaudio.com/forums/plan...con-dots-resonance-control-3.html#post1958582
Recent posts concerning experimentation with replacing part or all of the felt pads with paper or clear tape prompted me to take a few quick measurements next time I had the opportunity. The goal of the measurements were two fold.
1) Capture the influence of the felt pads on low frequency and high frequency response.
2) Determine effect of replacing the felt pads with paper or clear tape.
Attachment #1: Measured Low Frequency responses (ignore 60hz power line noise)
- Without any damping attached to the rear stator there is a +24dB response peak.
- Felt pads do a nice job of damping the resonance as well as lowering the frequency of resonance by adding mass loading from the air trapped between the felt pad and diaphragm.
- Neither of the tapes provide much damping at all to the peak. Note also the reduced output at 30Hz because of less mass loading from trapped air.
This explains comments by Mendel24 after experimenting with tape “…I have found that the bass only outer panels really need some felt backing on them or the bass does not sound quite right…” Post#9
Attachment #2: Measured effect on high frequency response
- Plotted responses are normalized by panel response with nothing attached to rear stator.
- Felt pads have minimal effect on the response.
- Reflections from the tapes put pronounced peaks and dips in the response. Since our hearing is more sensitive to response peaks than dips, the overall sound tends to be “brighter”.
Measurement of similar reflections from using additional thin diaphragms as dust covers like Quad does in the ESL-63 and variants can be found here: Post#16
Conclusion:
Jim Strickland did a great job of optimizing the Acoustat panel design while juggling conflicting design goals and keeping an eye on production cost.
The purpose of the felt pads attached to the rear stator of all Acoustat panels is to provide acoustic damping for the diaphragm’s low frequency, high-Q resonance. Ideally this damping would be achieved with no effect on the midrange and highs. For some time I have been wanting to measure and find out how close the Acoustat damping solution comes to the ideal. Comparison of other damping methods can be found here: http://www.diyaudio.com/forums/plan...con-dots-resonance-control-3.html#post1958582
Recent posts concerning experimentation with replacing part or all of the felt pads with paper or clear tape prompted me to take a few quick measurements next time I had the opportunity. The goal of the measurements were two fold.
1) Capture the influence of the felt pads on low frequency and high frequency response.
2) Determine effect of replacing the felt pads with paper or clear tape.
Attachment #1: Measured Low Frequency responses (ignore 60hz power line noise)
- Without any damping attached to the rear stator there is a +24dB response peak.
- Felt pads do a nice job of damping the resonance as well as lowering the frequency of resonance by adding mass loading from the air trapped between the felt pad and diaphragm.
- Neither of the tapes provide much damping at all to the peak. Note also the reduced output at 30Hz because of less mass loading from trapped air.
This explains comments by Mendel24 after experimenting with tape “…I have found that the bass only outer panels really need some felt backing on them or the bass does not sound quite right…” Post#9
Attachment #2: Measured effect on high frequency response
- Plotted responses are normalized by panel response with nothing attached to rear stator.
- Felt pads have minimal effect on the response.
- Reflections from the tapes put pronounced peaks and dips in the response. Since our hearing is more sensitive to response peaks than dips, the overall sound tends to be “brighter”.
Measurement of similar reflections from using additional thin diaphragms as dust covers like Quad does in the ESL-63 and variants can be found here: Post#16
Conclusion:
Jim Strickland did a great job of optimizing the Acoustat panel design while juggling conflicting design goals and keeping an eye on production cost.
Attachments
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Thank you for the info bolserst!
How were the frequency responses measured? Right at the panels or closer to where a listener would be seated (8 or 10 feet away)?
As noted, I have the bass only panels on my Spectra's back in stock configuration. But the inner full range panels have only the big piece of felt in place with paper tape above and below. Sounds best to me that way after much listening and experimentation.
Wonder how that would measure (combo of felt and tape)? Having the panels run in the Spectra configuration might alter the measurements as well. But if it sounds good it is good!
Long live Acoustat!
How were the frequency responses measured? Right at the panels or closer to where a listener would be seated (8 or 10 feet away)?
As noted, I have the bass only panels on my Spectra's back in stock configuration. But the inner full range panels have only the big piece of felt in place with paper tape above and below. Sounds best to me that way after much listening and experimentation.
Wonder how that would measure (combo of felt and tape)? Having the panels run in the Spectra configuration might alter the measurements as well. But if it sounds good it is good!
Long live Acoustat!
- Low Frequency measurements were near field right at the panel, giving a measure of the low frequency energy launched into the room.
- High Frequency measurements were taken about 6 feet away and windowed to remove room reflections.
Many people equalize speakers to their preferred "house sound", which may or may not be flatish on-axis. I found it educational to insert a 1/3 octave equalizer in my system and experiment with small changes to the response in different frequency ranges. It is often surprising how subtle response changes can influence our perception of the stereo image illusion and clarity/smoothness/detail/etc. Once you know what you like it is easy enough to get there with a few measurements and some line level equalization between pre-amp and power amp. I have found this to have fewer draw-backs than trying to manipulate a loudspeaker's response by acoustic means.
I would expect a combination to provide a response between the full felt and full tape curves in the bass...likely in the high frequency response as well.
.bolserst...........As with all you do for us here.... with your help an time thanks
Yes it seems like it would be ezer just too........ insert a 1/3 octave equalizer in to ones system ......but I got tell you.....were you may have found fewer draw-backs..... when geting measurements......I have never found any Acitve EQing.... that sounds are as good....as with acoustic means....... A then you add ESLs in to the sound MIX.....
adding anything more to the audio path than one has to.....never sounds better to my ears...just my 2 cent.....
Yes it seems like it would be ezer just too........ insert a 1/3 octave equalizer in to ones system ......but I got tell you.....were you may have found fewer draw-backs..... when geting measurements......I have never found any Acitve EQing.... that sounds are as good....as with acoustic means....... A then you add ESLs in to the sound MIX.....
adding anything more to the audio path than one has to.....never sounds better to my ears...just my 2 cent.....
Bolserst,
Thanks for the measurements and time taken to do them, It conforms what I hear from my 2+2s when I fooled with the removal of the felt and modding, They sound better with the felts on.
As for eq,, the Behringer DEQ2496 done in the digital domain sounds excellent to me, I also run them with 4-`15" subs crossed at 60hz in diapole.
Thanks for the measurements and time taken to do them, It conforms what I hear from my 2+2s when I fooled with the removal of the felt and modding, They sound better with the felts on.
As for eq,, the Behringer DEQ2496 done in the digital domain sounds excellent to me, I also run them with 4-`15" subs crossed at 60hz in diapole.
You should not run any equalization with 'stats. The reason being is that these are very revealing speakers and the equalization will introduce distortion. Call it coloration, whatever, but they will.
If you need equalization, you got a room problem and equalization is a band aid.
I say try this:
Run equalization. Adjust speakers, add room treatment, whatever, until the amount of correction is 3db or less. I say 3db because variations of 3db or less are not audible. Once you achieve this, put the room correction stuff in the garage.
I achieved flat response with my old Pioneer (MCAAC correction), but flat without all that correction sounded much better, more depth.
If you need equalization, you got a room problem and equalization is a band aid.
I say try this:
Run equalization. Adjust speakers, add room treatment, whatever, until the amount of correction is 3db or less. I say 3db because variations of 3db or less are not audible. Once you achieve this, put the room correction stuff in the garage.
I achieved flat response with my old Pioneer (MCAAC correction), but flat without all that correction sounded much better, more depth.
1100...........
Any one with a Nom room can hear ....just what your saying....EQings out!.....
not with just ESLs.....any great Speakers
Only people that have BIG rooms.........
like other have or wont....a room30'x50.' or biger...get real.
Were talkin big"Echo Chamber."...Not High End audio sound that most are looking for........
I have tried a $10k room correction setup for 4 weeks.....it sound great at first...hehe...tell you pull it out....Only hope for these manufacturer have is that customers have never heard a great Audio setup.................But TV....there you go....
Any one with a Nom room can hear ....just what your saying....EQings out!.....
not with just ESLs.....any great Speakers
Only people that have BIG rooms.........
like other have or wont....a room30'x50.' or biger...get real.
Were talkin big"Echo Chamber."...Not High End audio sound that most are looking for........
I have tried a $10k room correction setup for 4 weeks.....it sound great at first...hehe...tell you pull it out....Only hope for these manufacturer have is that customers have never heard a great Audio setup.................But TV....there you go....
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Apologies for lack of clarity concerning EQ…should have known better than to try and post that late at night
I was not talking about room correction, rather first arrival response of the speakers.
As pointed out, room response(modes, echos, reflections etc) is an acoustic problem that is best dealt with by acoustic means, not EQ.
The first arrival response of Acoustats tends to be pretty flat thanks to the LF and HF electrical equalization designed in to the interface units. What I was trying to say was that if this response is not to your liking it is easy to find out what response you do like with an EQ. Then you can adjust electric response to get there, rather than putting peaks and dips in the acoustic response of the ESL in search of an unknown target that will compensate for the first arrival response trend you don't like.
I didn’t mean to drag this thread into a discussion on the benefits(or not) of EQ.
If that is a topic of interest (how it specifically applies to ESLs) perhaps a new thread is in order?
Hopefully we can keep this one on the topic of Acoustats.
I was not talking about room correction, rather first arrival response of the speakers.
As pointed out, room response(modes, echos, reflections etc) is an acoustic problem that is best dealt with by acoustic means, not EQ.
The first arrival response of Acoustats tends to be pretty flat thanks to the LF and HF electrical equalization designed in to the interface units. What I was trying to say was that if this response is not to your liking it is easy to find out what response you do like with an EQ. Then you can adjust electric response to get there, rather than putting peaks and dips in the acoustic response of the ESL in search of an unknown target that will compensate for the first arrival response trend you don't like.
I didn’t mean to drag this thread into a discussion on the benefits(or not) of EQ.
If that is a topic of interest (how it specifically applies to ESLs) perhaps a new thread is in order?
Hopefully we can keep this one on the topic of Acoustats.
I'm rebuilding some spare interfaces for my 2+2's. New diodes and caps, and I'm tempted to add another 2 diodes and caps to the string for a bit more bias.
I did the 0.022uF/6000V cap mod across the string and very impressed with the result, which is why I'm tempted to add some more juice.... but I dont want to threaten or damage my
speakers.
I know others have done this, what do you think Andy? I know you dont much like mods to the original design, is there any chance I could do more harm than good?
I did the 0.022uF/6000V cap mod across the string and very impressed with the result, which is why I'm tempted to add some more juice.... but I dont want to threaten or damage my
speakers.
I know others have done this, what do you think Andy? I know you dont much like mods to the original design, is there any chance I could do more harm than good?