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In Reply to: RE: Acoustat Monitor 4 posted by Sondek on August 15, 2022 at 09:25:55
One thing I am looking for is the wiring between the MK 121 - 2A and the panels.
On Saturday when I disconnected the interfaces they were connected with old wire nuts. I was in a hurry and didn't pay close attention while doing it. I am sure one pair of wires from the interface were connected to only one wire on the panels. This made no sense but today when I connected the wires according to their R- W - B color it doesn't sound right odd bass and the entire output is not clear as with the basic equipment at the sale.
Somehow I think they were wired different than logic dictates and the one schematic I saw for the MK121.
No thoughts of keeping them. I have an amazingly understanding wife that has put up with my audio addiction for 49years.
My listening room is acoustically treated.
It contains a pair of Martin Logan CLX, 4 ML Depthi subs with CLX electronics inside.
Synology NAS -UltraRendu-SonicTransporter-Playback Designs I-Stream -Playback Designs MPS-5 -
ARC 40th Anniversary Line Stage- ARC 610T amps.
When I was talking with a friend on Saturday about purchasing the M4's she just sat there shaking her head in disblief. I assured her even if I only got my $800 back I want to try to get them to someone that could give them a good home.
That said in my shop I only had a Marantz 2245 receiver to try them with. 45 WPS 8ohm. Even low volume sounds different from pre purchase. Not what it should be.
That was when I upgraded my Monitor 4s to the dual transformer interface driven by a Threshold Stasis. I purchased them originally as the model X and later bought the kit with additional panel and new cabinet when it became available.
Agree with Sondek that one may be running out of phase with the other. I worked part time for a dealer in Atlanta during the 70s and originally the three connectors were separate bananas. Just follow the color coding! An early customer was a weatherman who happened to be color blind and fried a panel by sending the bias to the diaphragm. The triple solved that problem but it was still possible to reverse one with respect to the other.
Bass response should be darn good with that many panels unless there is a problem with one of the bass transformers. I later moved to 2+2s with two panels stacked over the other two for better rendition of image height.
$800 is a good price for a working pair. After moving to Sound Lab stats, I later purchased a needy pair of 1+1s. Sent the interfaces to a former Acoustat employee who upgraded them and I replaced the socks with more transparent spandex.
They would love being driven by your ARC gear. I drove the 2+2s with 500 watt VTL mono amps until I moved to the U-1s.
Well, I'm more confused than ever.
I reached out to Roy Esposito at Acoustat Service and he kindly responded to my email.
He informed me that I have The Monitor the first model after the X. As I assumed, they originally would have had the servo amps but he said the MK 121-2A will work with though they may have some mods done.
Part of me is starting to be a bit sorry I have attempted to save them but, it probably won't be the last time my wife tells me I told you so. :-) :-0
I already mentioned this but I am sure that when I disconnected the 3 interface wires from the 2 panel wires and 1 bias wire, it was not a 1 wire to 1 wire.
I was in a hurry and the old wires were so dirty you couldn't tell any difference in them.
When I removed one of the wire nuts connecting them, there is no doubt in my mind that it was more than 1 wire connected to 1 wire. I'm sure there was 2 connected to 1 but before it sunk in the wires all fell separate and I thought "OH NO that made no sense".
Any electrostatic speakers I have had, were 3 wires to 3 wires, interface to panels.
I have looked for a schematic for MK 121-2A but only find Mk 121 and don't know what the difference is.
I have searched the web with no luck and I have no Idea where to find one.
Roy suggested I could part them out on eBay but that would go against my reason for ignoring my beautiful wife's suggestion to not have another project.
They are now setting in the main room of our home office, recreation/ exercise equipment, storage and my work shop building. She will walk past them 10 -20 times a day, so, I probably deserve all of the snarky jokes I will endure until they are gone.
Any suggestions for schematics or my wiring issue will be welcome.
Who says, no good intentioned deed goes unpunished. :-)
Brad, come join us over here:
Post your question there. Andy's the man...
Roy is the resource I used to update my interfaces.
The panels are wired in parallel - three from each panel. With later interfaces like the ones I use, the signal cables are terminated with a curved spade connector while the bias terminates with a pin. I'm traveling and don't have easy access to internal pics but will be happy to post them later this week. I also have a schematic. Another great resource is found on DIY Audio where another ex-employee named Andrew goes by The Acoustat Answer Man and has been helpful to many.
There were many variations on the interfaces, some of which were identified a being a "Red Medallion" or "Blue Medallion". You may be aware there were one, two, three, four, six and eight panel variations and some like the 2+2, 6 and 8 were stacked sets.
So long as the transformers are good, the rest of the components can be easily replaced.
I will post a picture of the interface to see what people think.
This kind of worked it self out with the Blue and Red Medallion stickers on the interface.
I have them up and running and they sound wonderful.
I am going to list them for $1000 hoping to find a home for them.
They are in the Tampa Florida area at this time.
Those should be the older 3-wire panels. One wire for the front stator, another wire for the rear stator, and the third wire for the panel bias.
It's hard to tell from the pic, but it looks like all the panel wires are connected to those 3-way bananas, and I assume all the panels are correctly wired to those bananas. Is it possible one speaker has it's front/rear stator connections to the interface reversed from the other speaker? It's possible they're canceling each other out. Would be a simple matter to reverse the connection on one speaker and see.
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