Acoustat Answer Man is here - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Planars & Exotics

Planars & Exotics ESL's, planars, and alternative technologies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th February 2011, 03:52 PM   #11
diyAudio Member
 
AcoustatAnswerMan's Avatar
 
Join Date: Feb 2011
Location: Chandler Arizona
Quote:
Originally Posted by hella356 View Post
Thanks, Andy. I learned a lot about my various Acoustats from your site. Did you ever experiment with a tube front end on the Servo amps?
Sorry, no. I did do some service work on the Servocharge Amps, but never used them in my own system. Never cared much for their reliability or danger-value, so I always preferred transformers. Admittedly many of the reliability problems were addressed by later mods at the factory, and those done by Mike Savuto of Analogue Associates.
  Reply With Quote
Old 15th February 2011, 03:57 PM   #12
diyAudio Member
 
AcoustatAnswerMan's Avatar
 
Join Date: Feb 2011
Location: Chandler Arizona
Quote:
Originally Posted by SY View Post
Thanks, Andy- I had them apart once before (replaced diaphragms), but that was a very labor-intensive process; that time, the wires were intact. This time, they're not... sounds like I may want to just do a scratch build of new ones. Any particular wire recommendations?
The wire was custom made, 24-gauge fine-strand OFC, with PVC insulation, 100% tested to 10-kV. Jim Strickland did a lot of experimentation with wire insulation types, and found that PVC had the best combination of high voltage resistance and yet was 'leaky' enough to provide the right amount of resistance in the electric field (Jim's White Paper explains it better than I ever could!).
  Reply With Quote
Old 15th February 2011, 04:09 PM   #13
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
Originally Posted by AcoustatAnswerMan View Post
The 'C-Mod', introduced after the initial use of Medallions, was actually suggested by David Hafler (quite the expert in transformers himself). It involved changing the input crossover network to the hi-freq transformer, resulting in a smoother freq transition and less likelihood of core saturation.
Thanks for the info on the Medallion transformers. I had often wondered if the push for the transformer upgrade was mainly a reliability issue.

Your mention of the 'C-mod' brings up another topic I have been wondering about.
If you compare the Acoustat 'C-mod' interface schematic to the Soundlab Model A-1 interface schematic, they are nearly identical.
Do you happen to know if Strickland or Hafler was involved in developing the Soundlab transformer crossover network?
It seems their network should have been covered under Strickland's patent US4323736.
The 'C-mod' (and Soundlab) crossover networks do add a shunt resistive load across the primary of the HF transformer to reduce tendency for core saturation, but other than that, the basic circuit is the same.
  Reply With Quote
Old 15th February 2011, 04:24 PM   #14
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by AcoustatAnswerMan View Post
The conductive coating was a proprietary mix of carbon black, plastic compounds and solvents for bonding to the diaphragm. It was applied with a brush. Good luck in your attempts at Acoustat panel repair - if successful, please share your results.
Moray James is/has built replacement panels from scratch so it can be done.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 15th February 2011, 04:39 PM   #15
diyAudio Member
 
AcoustatAnswerMan's Avatar
 
Join Date: Feb 2011
Location: Chandler Arizona
I know that Jim maintained communication with other manufacturers of ESL's, most notably (Harold?) Beveridge, and he was never reluctant in sharing his expertise, but I am not aware of any actual design work that was done for other companies. Any similarity in circuit designs was coincidental, unless there was some 'copying' done, but I'm not making any accusations. Since Acoustat was somewhat the pioneer in making affordable, reliable ESL's (and in my humble opinion, never surpassed in those respects), designs that followed were bound to take advantage of lessons learned at Acoustat. As Jim was fond of saying "You can always tell the pioneers - they're the ones with the arrows in their back".
  Reply With Quote
Old 15th February 2011, 04:43 PM   #16
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Afaik, based upon actual tests - 20+ years ago now - and iirc, the HF xfmr has a different turns ratio in the C medallion version, the HF coupling caps were also changed. I wrote it down, and it is probably in a folder marked Acoustat, if I'm lucky.

Afaik, and I could be wrong, the PVC wires seemed to be attached with polystyrene dope, not epoxy. But on this I am only going by appearances.

There is/was an article in Speaker Builder years ago called "Amber" which was a DIY clone of the Acoustat panels in most regards.

The wire was essentially similar to "test lead" wire, except it was copper, not tinned (certainly on the later ones) and the PVC insulation was not as fat as standard test lead wire. Where one would get such a thing today is a good question, since it's not a standard wire afaik. If it made 10kv test, I'd be very surprised, but certainly better than standard PVC wire...

If you go with a very high ohm coating then it's unclear that the insulation is going to be much of an issue. In other threads on the Acoustat people have said that using a lighter diaphragm and lighter coating results in better HF performance and overall sound. At least that opinion was voiced, iirc.

Now, here's a question - there was an outfit in Florida that was making replacement transformers, do you know if they or someone else is still around??

Welcome to diyaudio!

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 15th February 2011, 05:05 PM   #17
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
Originally Posted by bear View Post
Now, here's a question - there was an outfit in Florida that was making replacement transformers, do you know if they or someone else is still around??
I believe Russ Knotts from JustRealMusic can make replacements.

Here is a link to his repair website showing a burnt up coil from a LF Acoustat transformer.
gallery

Here is a link to his main website:
Home Page
  Reply With Quote
Old 15th February 2011, 05:19 PM   #18
diyAudio Member
 
Join Date: Feb 2009
Andy, any info on how Acoustat tested regarding the angles of the panels, particularly the 4 wide speakers? Also, how important it is to mix 8" & 9" panels vs just going with 9 inchers in a Model 8 / 4+4 type? I'm planning to build such a speaker with all the extra panels I've got. Thanks!
  Reply With Quote
Old 15th February 2011, 05:49 PM   #19
diyAudio Member
 
AcoustatAnswerMan's Avatar
 
Join Date: Feb 2011
Location: Chandler Arizona
Quote:
Originally Posted by bear View Post
Afaik, based upon actual tests - 20+ years ago now - and iirc, the HF xfmr has a different turns ratio in the C medallion version, the HF coupling caps were also changed. I wrote it down, and it is probably in a folder marked Acoustat, if I'm lucky.

Afaik, and I could be wrong, the PVC wires seemed to be attached with polystyrene dope, not epoxy. But on this I am only going by appearances.

There is/was an article in Speaker Builder years ago called "Amber" which was a DIY clone of the Acoustat panels in most regards.

The wire was essentially similar to "test lead" wire, except it was copper, not tinned (certainly on the later ones) and the PVC insulation was not as fat as standard test lead wire. Where one would get such a thing today is a good question, since it's not a standard wire afaik. If it made 10kv test, I'd be very surprised, but certainly better than standard PVC wire...

If you go with a very high ohm coating then it's unclear that the insulation is going to be much of an issue. In other threads on the Acoustat people have said that using a lighter diaphragm and lighter coating results in better HF performance and overall sound. At least that opinion was voiced, iirc.

Now, here's a question - there was an outfit in Florida that was making replacement transformers, do you know if they or someone else is still around??

Welcome to diyaudio!

_-_-bear
You are correct that the original 'glue' used to attach the wires to the panel was a home-made brew of styrene pellets dissolved in MEK. The MEK actually melted the panel slightly, allowing the wire to 'sink into' the panel. I suggested epoxy since it is readily available and would probably work fine for spot-repairs. But for building a new panel - probably not.

I know there WAS a company in Florida making replacement transformers for Acoustat - at a handsome price - but not sure if they are still around or offering that service. I believe they were a successor to the original Southeastern Transformer, who made all of Acoustat's transformers except towards the very end of Arizona production.

I cannot confirm nor deny your suggestion that the turns ratio was changed for the Medallion HF tranny. However, there was NO difference in transformer from B Meallion to C Medallion - only the passive network changed.

The wire that Acoustat used was most certainly rated for 10-kV, and was 100% tested by the manufacturer for pinholes and other sources of leakage.
  Reply With Quote
Old 15th February 2011, 10:57 PM   #20
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Andy, I just said that I was surprised that the wire would handle 10kv...

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
No answer Antoni D The Lounge 2 13th February 2011 06:19 AM
need a tech to answer this one pks71 Car Audio 1 19th November 2004 11:50 AM


New To Site? Need Help?

All times are GMT. The time now is 02:14 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2