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Searching for info about Acoustic Research MGC-2 and the MGC-1e controller


Paul Croes
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Hi everybody,

i am new to this forum.

A year ago i buy in Belgium ( i live in Wiesbaden, Germany ) a beautiful pair AR MGC-2 speakers without the MGC-1e controller.

I am searching a lot on the internet about this equipment and the missing part. Maybe someone here can help me find it ! ūüôā

I also read about some alternative stuff..  the Behringher EX1 and others but i do not understand much of the technical part of it.

So, i am a little bit helpless. Maybe somebody here can explain better. And yes, i had contact with Ken Kantor about it.

In the pictures you see a review about the MGC-1, i still not find any review from the MGC-2.. 

Last picture is my little set-up :

Quad 33/303, Cambridge Audio DAC, Braun 500PS and the Acoustic Research MGC-2 speakers.

The picture above is a reproduction from a album cover 'Miles Davis hand' by Irving Penn

Kind regards and thank you for your time,

Paul Croes

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Here's a link to the 1985 Stereophile review, as re-issued in 2015. In the comments, one writer mentions that he owns Kantor's personal pair of MGC-1 speakers, but faced the same dilemma regarding its controller. His solution was to use a home theater receiver for the necessary processing.

https://www.stereophile.com/content/acoustic-research-mgc-1-loudspeaker

Maybe he's the same guy from this 20 year-old post:

https://community.classicspeakerpages.net/topic/267-ar-mgc-1/

There's undoubtedly a lot of used semi-pro digital effects equipment from the last 25 years that could be made to do the job - maybe start looking in those types of forums for assistance.

Nice QUAD system, by the way - you don't see it that often, anymore. It still looks very modern.

 

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The idea behind the MGCs was to create simulated ambience by shooting delayed signals out the sides of the speakers that would bounce off side walls. The MGC-1 had respectable 2-way woofer/tweeter side pairs, but the MGC-2 only had a single bass/midrange driver. For both models, the processor allowed the delay to each side to be separately adjusted to compensate for asymmetric listening spaces. 

In the absence of the original processor electronics, I think what I would do with an MGC-2 is just hook up the main front-firing set as the FLR pair on a HT surround unit and instead of trying to feed something to the side-firing driver, use some other ARs of the same period as surrounds and the front center channel. 

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Some times I think Ken's contribution to the audio world are overlooked. I remember when I used to frequent AudioKarma site --- many people didn't treat him too well. Perhaps they had no idea who he was.

 

Screenshot 2022-01-12 at 19-18-40 Search Results for Query ken kantor Audiokarma Home Audio Stereo Discussion Forums.png

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It has been a while since I read the papers on this speaker, there were publications in the AES.

It would be great if someone who really knows could tell us about any frequency response 

shaping, and delay range for the ambience speakers.

A MiniDSP could probably provide what's needed but not sure about the range of delay.

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Here's the excellent article that KK wrote on the MGC-1 for Audio magazine.

Assuming he has an additional stereo amplifier, the OP's need might be met for not much money with a vintage Alesis Microverb III digital delay, and their MEQ-230 1/3 octave equalizer. These were very popular as small studio devices, and there are plenty still around.

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  • 2 weeks later...

Hi Guys, sorry for the late answer.. I was traveling for work and did not realize all this support.

Thank you all for your time and knowledge.. I try to understand all the information and come back here soon.

Have a good time.. 

Kind reagards,

Paul

 

 

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Ken was co-author on "A Psychoacoustically Optimized Loudspeaker" published in the AES.

https://www.aes.org/e-lib/browse.cfm?elib=5230

I have this in my library and studied it years ago, IIRC it was the research behind the MGC speakers.

Not sure why it was not listed in the references at the end of the Audio article.  Here's the Audio

article in .pdf format starting on page 37 in the .pdf, might be easier to get a clean print:

https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1985-07.pdf

 

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Thx Pete, thx you all..

I found a good ( i think ) MGC_1e Amp. Found it in Germany at 20 km from my home. The guy had two of them, demonstrate it with his MGC-1 speakers. At home with my MGC-2 speakers and i hear no effect. I open one speaker and see.. :

The 4 pin plug only two cables connected. All other parts looks clean. The connection with the tweeter looks very strange.. Could that be the problem ?

Kind regards, Thx for your time, Paul

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The green (-) and white (+) wires go directly to the 6-inch ambience driver. 

The resistors soldered to that loose circuit board appear to be a modification.

Pins 3 & 4 from the rear connector must be attached to the main board, which doesn't seem to be the case with your speaker.

Pin 3 to one leg of the .31 mH coil, and pin 4 to the 12 mF capacitor.

It's hard to tell from your photo if the green & white ambience wires are soldered to the proper location on the main circuit board.

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10 hours ago, ar_pro said:

The green (-) and white (+) wires go directly to the 6-inch ambience driver. 

The resistors soldered to that loose circuit board appear to be a modification.

Pins 3 & 4 from the rear connector must be attached to the main board, which doesn't seem to be the case with your speaker.

Pin 3 to one leg of the .31 mH coil, and pin 4 to the 12 mF capacitor.

It's hard to tell from your photo if the green & white ambience wires are soldered to the proper location on the main circuit board.

I open the other speaker this evening and make more pictures.. Any idea why it is done like this ? 

They refoam the all speakers and it looks well done. A bit strange that they do this kind of modification. 

Is it possible to make a little drawing about the right connections and how to bring it in original condition ? 

Kind regards, thx for your time,

Paul

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Does it look as if the side mid and the added resistors have been rewired to be in series or parallel with the front-firing mid? I'm wondering if perhaps someone who didn't have the MGC amp rewired the speaker so the side-firing mid would produce output from a regular stereo amp.

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6 minutes ago, genek said:

Does it look as if the side mid and the added resistors have been rewired to be in series or parallel with the front-firing mid? I'm wondering if perhaps someone who didn't have the MGC amp rewired the speaker so the side-firing mid would produce output from a regular stereo amp.

Hi Genek, i don't know.. Normally there is no reason for any modification when the MGC-1e controller is not in use. When power is off or you have no MGC1e controller, the MGC-2 speaker act like a normal set speakers. 

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22 minutes ago, genek said:

What I'm wondering is if someone tried to hack the crossover to make the side-firing mid work without the MGC amp.

Yep - that could easily be the case. A pretty good attempt at starting a fire, anyway.

If the main board's traces haven't been destroyed, it might just be a question of de-soldering the unnecessary wires, re-connecting pins 3 & 4 to the correct spots on the board, and re-attaching the ambience driver. 

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