My Bozak Concert Grands were built in 1974 as I bought them new and my B401 Rhapsody's were built in 1975 so that makes them 70's speakers. Harry

I was referring more to the design period than the build date. The Concert Grands are a 1950's design. AR3a's were also available in the 70's, but their design was a product of 1960's technology and R&D.

Now that would explain things. Obviously by the time the 90's came around, performance was an afterthought.

And a recognized name was everything. I get a sick feeling when I see stuff today with names like KLH, Fisher, Scott, Westinghouse, RCA etc...

Amen...it really is awful. My experience with buying those speakers proves a point; companies today sucker people in with brand recognition. Next time I will be careful to do my homework.

I was "tricked" in the 90s into buying some speaker that have foam surrounds. Even good names like Bang & Olufsen use them in their CX-50/CX-100 speakers. Small bass drivers that are uniformly rotted out. These guys command a premium price even with the foam rotted. I did get a few and have started to replace the surround but have not finished. Now, I won't touch a speaker that has a foam surround. Cloth, paper and especially butyl rubber is just fine after 30 years...

The foam surrounds have acoustical properties that you can't get in natural rubber or paper. They are very light in weight and very stable while at the same time being very "lossy". This is a very good combination of characteristics when a woofer is being used up fairly high in frequency. Of course, given that the material is polyurethane, it's subject to oxidation; hence the "rot". I don't think the severity of this problem was well understood in the 70's-90's when this material was almost universally used in woofer surrounds. My company (SEAS) is using a new type of foam surround in a full-range driver that we build, that uses natural rubber as the material. It has all the good characteristics and will never rot.

http://seas.no/index.php?option=com_content&task=view&id=293&Itemid=255

Ditto, no foam surrounds! But have you ever tried replacing them? Every tutorial I see makes it look easy, but I have my doubts.

I have gotten the surrounds for the B&O CX-100 speakers. Got the dust cover off of the VC, cleaned the old surround off of the cone and cemented the new surround to the cone. I have not had chance to cement the surround to the basket yet. Takes a lot of time and I don't have that right now. And, I have 14 speakers to do

14 speakers?

I have done the surrounds on a pair of Infinity speakers. Came out very successfully but one of them took two tries. There are two kinds of kits -- one with just glue and surround, one which adds shims to space the voice coil properly and includes new dust caps, since you must destroy the old dust cap to place the shims.

The key to getting this right is that the voice coil clearance to the magnet must be exactly correct. So I would only use the type of kit that includes the shims. But the shims must fit properly -- firmly enough to secure the voice coil in the proper location, but not so tight that it distorts the voice coil. One of the Infinity drivers worked well and came out perfectly, but the other one had a tighter clearance. I made the mistake of forcing the shims into place, which actually set the voice coil off-center. After the glue had dried I tried the speaker and found the voice coil dragging badly. Luckily I hadn't glued the gasket yet, so I was able to slowly remove the surround from the speaker basket and try again, making up my own shims from thinner plastic material. Second time was the charm.

So yes, it can be done, but it is a bit tedious and you need to be careful.

-David

I really like my Klipsch belle's, Avid 330's, and yes my B.I.C. formula 1S! Powered by a Kenwood KR9600 reciever at home.

At work Lafayette pip-speaks, And the mother of kabuki speakers the Kenwood KZ10000Z monsters mounted to the wall. Powered by a Kenwood KR7400 reciever and a sony 300 cd changer.

dave

As for the surrounds, I did remove the dust cap so that I could shim it. I found that three strips of a business card was just about the exact thickness to shim the voice coil from the magnet pole. Just gotta have time to finish the job...

I dunno, guys...seems like very meticulous work. I think if I ever need that done, I'll leave it to a professional

Yeah, two in each CX-100 and one in each CX-50. Needless to say, I have a few. Future intentions are to use for Computer speakers among other things...

My pair of Smaller Advents purchased new in 1977 eventually rotted out.
The Advent Maestro's I purchased in 1987 rotted out too by 1999.

Oddly, Radio Shack carried a mean-looking 10" woofer at the time - 4 ohms, and had a butyl foam surround with impressive specs. - I purchased two and installed them in the Maestros.
At the time I think they were $80 each - and on half-price sale, so I had to grab them.
Wonderful performance!
Even smoother bass!
They're called "Pro Series" and to this day they're fantastic drivers.


Edit: found a photo of them.

Don, have you ever wondered whether or not it might be worth it to buy new woofers (or good used ones) as opposed to reconing? It's something I've wrestled with...I see pros and cons on each side.

I've done new foam surrounds - t'aint that difficult if you have a steady hand.

But wouldn't that mean I'd have to give up the drinking?

Indubidibly.