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XRT20 Speaker System Restoration (and questions)

w1jim

w1jim

I can fix it but good...
Subscriber
I just picked up a pair of the McIntosh XRT20 speakers and have a few questions in my quest to restore these monsters.

First off (as to be expected) the 2-8" mids and 4-12" woofers need to be refoamed.
The refoaming of the mids is straightforward but the woofers have me in a bit of a quandary.
The surrounds on these appear to be typical foam but with some kind of a flexible substance applied to them. This can be seen in the first picture.

The foam is all deteriorated but there is some gooey / flexible stuff applied to the front which actually held them together.
In replacing the foams is there some sort of a treatment I should use on these? Perhaps whip up some brushable latex and apply it?
Or just leave them as is?

These were originally installed by Gordon Gow and he mounted the tweeter columns on the wall about 1 foot from the corners.
The manual (which came with it) specify that the wall should be divide into thirds and the columns mounted 1/3 of the way from each corner. Any thoughts on how I should mount these?

Lastly (for now) since my anticipated mounting location precludes the flush mounting I plan on building some brackets that will closely mimic the original CS20 brackets which position the rear of the tweeter columns and woofer/midrange boxes on the same mounting plane.
Would there be a problem / loss of imaging/soundstage if I position the tweeters forward about 6-8 inches?

Any other recommended mods?

Thanks, more to follow as I progress.
JimB



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Time allignment was an unknown quantity back when we first installed these back in 1980s, became the hip thing to do in the 90s, and now not so much.

I mounted a number of pair with the tweeters even with the woofer front with no ill effect. (I think they had less diffraction issues).

No special coating was on the woofer surrounds that I can remember. Maybe 3rd refoam?

The later pairs used a crossover modeled after the XRT19s. Titghted up the mid bass to only have 1 12 working that part of the spectrum.


Make sure to plan on finding someone to voice them for you with a MQ107.
 
How critical is the MQ107? Could I emulate it's characteristics with a more "garden-variety" EQ or parametric EQ? I'm under the impression that I'd need to adjust <400hz frequency range.
Any comments on Gordon's positioning the tweeters in the corners?

Thanks for your feedback on the surrounds - sounds like it was someone's idea of a tweak. I won't worry about it.
 
In my research I find evidence that the 12" woofers on some of the McIntosh speakers were treated with some sort of a "dope".
I found this thread on the XR-6 speakers, specifically posts 17, 26, 27 and 29 lead me to this conclusion.
None-the-less it appears that nobody thinks it is important to redope the speakers after a refoaming so I will continue that trend.
 
I think the most critical thing is that the 1/2 round surround has enough roll, Roger makes a point of this, so that it will not restrict the woofer movement.

Most EQs do not play well between a Mac preamp and amp's 2.5 volt output/input.

The room nodes and speaker paplacement will determine the areas of adjustment.

Even the beloved Gordon could not make the customer do the right placement. Sometimes you have to do what you have to do. When you read Roger's article about the club with tweeter on the ceiling, that was our company, doing what the customer wanted.

I will try to post some pictures of a room that Sid Coderman and Roger helped me design when a client built a room just for the 20s and his office.
 
I get what you say about customer demands. Our motto when I owned a car stereo business was "The customer is often right".

I'll be running these from my restored Pioneer SX-1980 so the 2.5v isn't a consideration here. Initially I'll try a Pioneer SG-9500 that I have.
 
c_dk said:
The Pioneer will be thin on......lets just say grunt if you catch my drift.
Click to expand...
Well then I may need to go another route in the future but for now it'll have to suffice as a sort of a mini-system :scratch2:.
I'm currently devising a standalone mount for the tweeter array while I await the arrival of the 12" foams. I've already got the mids done and reinstalled.
I was thinking about replacing the wire connections on the back with some 5-way binding posts but I'm going to stick with the stock ones for now.
 
c_dk said:
The push connection speaker contacts were awfull on all the XR series speakers.
Click to expand...
Good to know - then I'll consider replacing them with a receptacle that accepts banana plugs. I have some of these that I think are silver. It's unlikely that I would use bare wires or ring connectors in the tight confines. These would be much easier to plug/unplug.

Any other weakness I should address?
For example, the electrolytic caps in the crossovers, the 1/4" phone plugs for the tweeter array or the plug that links the upper and lower sections of the array?
 
Kind of a PITA but I changed out the old speaker connectors with some binding posts. It's somewhat tight in there with limited wire length to deal with.


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Everything is refoamed and reassembled - now I just have to get them into the house and move the big KEF's out of the way..
Soon, very soon...


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Making up my list of audition records-
Telarc 1812 overture
Joan Baez - Diamonds & Rust
Buddy Rich - Class of '78 (D2D)
Bill Evans, etc - For Duke (D2D)
 
Don't baby 'em - let there be rock !

Surely you must have some nice clean copies of The Who, or Zeppelin or something else like that to get those surrounds all broken in ?

:-)

jblnut
 
I would contact Roger Russell on his web site. The wrong surround a dope could altar the frequency response and lower the over all output. Its been over 7 years since I refoamed Mac speakers at work. I know he will be glad to help. TWI
 
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