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ChrisM

Speaking of Surrounds.....

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I am about to start working on my IIIs. They are in essentially untouched, lovely condition. They are circa 1970’s models. I also have some butchered IIIs which are also lovely but all the drivers except the Flexair woofer were swapped out for cheap Radio Shack drivers. They basically wrecked the front panel putting in the RS parts so it will get replaced. I have the correct midranges and some little cone tweeters which might work. I am also considering just putting in one modern dome tweeter.

So in the course of this, I noticed that the Flexairs’ surrounds are a bit dry. I called the folks at Great Plains Audio because the Flexairs are relatives of the mighty Altec 15’s (which I also have) to ask about buying appropriate goop for accordion surrounds. Short answer, they don’t have any. If an Altec dries up it would get reconed. Their new cloned drivers use a PVA compound which can’t be used over the old stuff.

This brings me to a question.

Is there any way to get a larger quantity of RoyC’s magic elixir without paying a fortune?

I also have a bunch of other old drivers which need some rejuvenation.

I suspect the reason it is expensive is that because as far as I can determine the minimum quantity of liquid butyl rubber is 100lbs. Not cheap. I’m not opposed to mixing up some myself but I can’t find smaller quantities of the butyl. Toluene is easy and available in gallon cans.

Any Ideas?

 

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Send RoyC a PM

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Those 4 little cone tweeters in the Rectilinear III really do sound good together. My various past experiments with other cone & dome tweeters never quite equaled the originals. Beware those holes are small & will need to be enlarged to fit most other tweeters. 

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Parts Express had some decent looking little 2" cone tweeters a while ago for about $1.50 each. Naturally I bought a bunch on the off chance they might be decent. I haven't got to testing them yet because I moved recently. We'll see. My pristine IIIs have all their tweeters plus I have some spares out of some wrecked Mini IIIs. My OTHER IIIs which some nitwit replaced the drivers with Radio Shack "things" will be the "Semi-Modern III" experiments. As I said I have to make a new front panel so I don't have to worry about existing driver holes. I will document the fun for posterity.

In other news, I got in contact with Roy and he confirmed the unpleasant reality. The liquid butyl rubber, Kalene 800, only comes in large quantities so it is a major investment hence a large part of vintage-ar's price. Damn.

As the proud owner of some Altec Valencias, and having examined some other old school 12" and 15" drivers with accordion surrounds, all the big old boys are as tacky as ever but it appears that the ones with light weight surrounds will at some point require some sealant. Heads up Flexair owners.

So now the question, which PeteB might know the answer to, is do the Philips mids with cloth surrounds need re-sealing? The KLH 12.5s do and my Philips drivers are totally dry. I'm thinking the sealant may need to be thinned out some more.

 

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The Philips mids' surrounds were always porous & don't need sealant. 

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I have some AD5060/sq8, the ones that came with the plastic enclosure, and they have coated surrounds. I don't think they were ever used and were sealed in storage boxes.

All the ones I have which were in use in Rectilinears look really porous as you say. I think they did have some sort of super thin coating which has disipated over time.

I also have some KLH Model 20 woofers and some 12.5 drivers whose surrounds are totally devoid of sealant. You can see right through them. This obviously isn't right and I think the same thing is true of the Philips.

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