Replacing Diaphragms

**voice of the theater** · June 17th, 2010, 12:40 PM

Originally Posted by robertbartsch

I'm restoring a set of Velencias "Bs" now and the biggest improvement you can make is swapping the HF diaphragms with new GPA units.

I've often wondered how much age effects diaphragms. My Valencias and AS 101's both have the original drivers and diaphragms and both pair sound clean and crisp and matched. I know if they're abused/have too much power cranked through them that it can damage the diaphragms and in that case replacing them would seem to be an obvious upgrade. But what if they're never abused? Do 40 year old diaphragms lose some of their "magic" just from age? I've read two different opinions here--one is that no matter what, replacing 40 year old diaphragms is always an upgrade. But I read somewhere on this forum quite a while back that someone said that replacing the diaphragms will make your horns sound different than they do now with the older/original diaphragms, but not necessarily better than they do now. I know the GPA diaphragms are REAL Altec diaphragms, so obviously they're a huge upgrade if you're replacing damaged Altec diaphragms, but what if your 40 year old diaphragms have never been abused? Anyone out there have any experience with this matter?

**bowtie427ss** · June 17th, 2010, 01:24 PM

but what if your 40 year old diaphragms have never been abused? Anyone out there have any experience with this matter?

Metal fatigue affects the compliance. New phragms are the equivalent to new strings on a guitar.

**Altec Best** · June 17th, 2010, 01:55 PM

I think alot has to do with how much they were used and not necessarily age.If they sat in cabinets for 40 years never played they will be as new (Fatigue Wise).If the drivers come out of a club,bar,etc.. Replacement is in order.

**bowtie427ss** · June 17th, 2010, 02:42 PM

Originally Posted by Altec Best

I think alot has to do with how much they were used and not necessarily age.If they sat in cabinets for 40 years never played they will be as new (Fatigue Wise).If the drivers come out of a club,bar,etc.. Replacement is in order.

Everything is a factor, play time and intensity, crossover frequency, environmental factors.

I'd submit for debate the effect that being located in a loud environment can have on them.

Those new unused for 40 years speakers in the club for instance(i happen to own a pair), were they facing the house PA where a hard rock band performed 3 nights a week for the last 40 years? if so i can almost guarantee some fatigue has taken place even though the speakers have never seen a watt of input. Acoustic energy captured by the horn is continuously "working" the diaphragm, if the speaker is connected to an amplifier, this may damp some of the motion, but probably increases stresses at the point where the dome meets the voice coil. Either way, in my mind it's mechanical "wear" that's occurring.

OTOH, a 50 yr old pair of 802's in 820 corner cabinets that have remained in those corners of a living room for those 50 years and having never been driven above a level equal to normal conversation may well perform as new in every respect.

The overall condition and "mechanical age" of HF diaphragms is IMO, a huge variable that many folks don't consider when buying drivers. This is just one of the reasons that a known history plays a big part in what i'm willing to pay for a vintage speaker component.

Just my .02 .....................................

**Altec Best** · June 19th, 2010, 01:44 PM

Originally Posted by bowtie427ss

Everything is a factor, play time and intensity, crossover frequency, environmental factors.

I'd submit for debate the effect that being located in a loud environment can have on them.

Those new unused for 40 years speakers in the club for instance(i happen to own a pair), were they facing the house PA where a hard rock band performed 3 nights a week for the last 40 years? if so i can almost guarantee some fatigue has taken place even though the speakers have never seen a watt of input. Acoustic energy captured by the horn is continuously "working" the diaphragm, if the speaker is connected to an amplifier, this may damp some of the motion, but probably increases stresses at the point where the dome meets the voice coil. Either way, in my mind it's mechanical "wear" that's occurring.

OTOH, a 50 yr old pair of 802's in 820 corner cabinets that have remained in those corners of a living room for those 50 years and having never been driven above a level equal to normal conversation may well perform as new in every respect.

The overall condition and "mechanical age" of HF diaphragms is IMO, a huge variable that many folks don't consider when buying drivers. This is just one of the reasons that a known history plays a big part in what i'm willing to pay for a vintage speaker component.

Just my .02 .....................................

That was just my point it isn't set in stone each diaghram has to be evaluated individually if possible.On all points mentioned.I just picked up a pair of 8-G's with 23744's NOS that I'm willing to bet have NO Fatigue

and they been on the shelf for 35 years.Just because they are 35 years old doesn't mean they won't perform as intended or spec'd.You have to hunt for those treasures though.

I guess the point I was making is age has nothing to do with it as long as they are in a protected enviroment.And most importantly not A-B-U-S-E-D

But already made this point in post #3 IMHO

**bowtie427ss** · June 19th, 2010, 03:09 PM

Those are a nice little treasure, and in my mind would represent the absolute peak value in 802-8G, very nice indeed!:2thumbsup:

**SOOTSHE** · June 20th, 2010, 03:49 AM

I almost feel priveliged to see something like that!

**Panomaniac** · June 20th, 2010, 10:45 AM

Wow! Nice score. Congrats on that one. What are your plans for them?
Actually, it would be great to measure them, for my fun, if nothing else.

**Altec Best** · June 20th, 2010, 12:21 PM

Originally Posted by bowtie427ss

Those are a nice little treasure, and in my mind would represent the absolute peak value in 802-8G, very nice indeed!:2thumbsup:

Thanks Tom

Originally Posted by J Henry

I almost feel priveliged to see something like that!

Hi John, I feel the same way when I got them I took off the covers just to make sure everything was Kosher and the Diaghrams are gorgeous.Each box has a little bag in the bottom with 2 nuts and 2 washers with a peice of paper in the box explaining diaghram replacement.Not going to find anything better than this.

Originally Posted by Panomaniac

Wow! Nice score. Congrats on that one. What are your plans for them?
Actually, it would be great to measure them, for my fun, if nothing else.

You know Mike I was thinking the same thing.If I had them a month sooner.I could have at least sent you my other spare pair instead of the other ones that I sent but didn't have these beauties as a back up at the time.I already know how these measure up my friend

**Cal Weldon** · June 20th, 2010, 05:38 PM

No expert here but one would think with the aluminum and pascalite diaphragms the temper would change and the metal would become harder and the the symbiotik ones with the kapton surrounds would become more brittle over time perhaps stiffening and reducing travel whereby increasing the the low cut off frequency and maybe even the Fs. Phenolics would become more brittle over time as well I guess. Dunno but it makes sense that things would change. I think the glue on the former would be more affected than anything else eventually giving up the ghost as the volatiles gas off but again I think using them would tend to cause the break down more than just sitting around.

I guess I've just said what you guys already did.