Does Replacing Surrounds Degrade Performance?

[rushfan]

Hi all,

My local speaker repair shop refuses to sell refoam kits, claiming that the process degrades the sound of the speakers too much. This surprises me, given the popularity of the process here at AK. Nobody here seems to be concerned about this.

Does in fact the refoaming process, even when done well, result in a finished product that is clearly inferior to the original? If the answer is yes, can the "downgrade" be quantified - i.e the repaired speaker is only 90% as good as the original? Silly question, I know, but I'd like to put this argument to rest, at least for my own sake.

My intuition tells me that refoamed speakers sound indistinguishable from the originals when quality surrounds are used. I just want to hear it from the experts!

 

[noprayer]

I personally think the guy that told you this is a moron that probably has a large stock of cheap drivers that he paid too much for and he needs some mook to unload them on. I have re-foamed many drivers and do not think it degrades performance at all when done correctly.

 

[kermit z]

I have refoamed a few speakers. I have found there is a break-in period but once they are broken in they sound great. Not sure what that guy is talking about. I would think refoaming would fall under speaker repair which I assume he is in the business to do.

 

[dc270]

Dito noprayer, re-foaming is an excellent way to revive a proven sensible speaker design. The foams being produced today are quite similar to those they replace and can be measured as such. True enough some foams will not function or fit well on some woofers types as the foam is an integral part of the woofers overall performance. Also there is typically a break in issue when refoaming- usually after 20~40 hours of play time they are good to go. Compliance (stiffness factor) would be a nice feature or spec if the foam people would or could offer that. It is a good thing to know your foam seller- the person I know at MSound knows his foams very well and reccomends certain foams for certain applications to me often.
I have literally re-foamed hundred of speaker frames with very good results and they have sounded and measured well. The other option of replacing the woofer is a bad option in my book as it would be very $$$ and really unecessary- plus the results woulde be a total crap shoot. Re-foaming the actual woofer is a viable, inexpensive way to bring that speaker back to life with tyically good results and a sound very close to or even better than it originally had!!
I would avoid the person/ company that told you otherwise!
DC

 

[Arkay]

In SOME cases, it can degrade the sound, but it never has to. The reasons aren't hard to understand.

When the speaker-design gurus in a company are designing a speaker, they take into account how the parts interact. The surrounds will have an effect on the movement of the cone.

At one extreme, just imagine if you made the surrounds out of aluminum: the front of the cone would be totally unable to move!

At the other extreme, driving a cone without any surround lets it flop around; there is nothing to help slow and control its motion. [Ignoring for the moment that the air leaks out all around the cone, which also has a huge impact on sound!]

The shape of a surround also makes a difference: a narrower or wider roll will allow a greater or lesser degree of movement.

So both the shape and the stiffness/flexibility of the surround will affect motion of the cone (as well as air pressure/flow) and thus the driver's sound.

So the speaker designers "match" the cone with an appropriate surround, to get a particular controlled cone movement, which --if the speaker designers are doing their job well-- translates into good sound.

Sometimes this "matching up" process leads to interesting designs, like the masonite rings-plus-surrounds in large Advents, which put a 10" cone into a 12" basket, but (especially these days) most designs are very similar now, for any given driver diameter.

SO... if you refoam your drivers with surrounds that are SIMILAR in characteristics such as shape, flexibility and tendency to return to the original shape, you will get similar results to the original drivers. IF you use identical-replacement surrounds and do a good job of alignment, you will have speakers that are truly "as good as new".

But IF you use surrounds that are very different in characteristics, the result will be different. Put stiffer butyl-rubber surrounds on drivers that were designed to have soft foam surrounds, or cloth ones, or put narrow-roll, short-throw surrounds on drivers that were supposed to have wide-roll, long-throw ones, and you will have serious degradation of sound quality!

Likewise, screw up the alignment when gluing and the cones will no longer move properly. This can affect the sound. In the worst scenario, you'll end up scraping the voice coils, resulting not only in horrible sound, but also in short-lived drivers!

Another possibility is the use of an inappropriate glue, resulting in surrounds that leak or come loose... or perhaps a sloppy glue job that results in large, irregular parts of the surround being stiffer than other parts (although I've never seen that, it could happen). That would adversely impact on sound.

So your repair guy was right...sometimes. He was right if the job is screwed up by using incorrect surrounds, or by bad alignment when gluing, or a horribly sloppy glue job. But when the refoaming is done right, --and let's face it, it isn't very hard to do right!-- then he is absolutely wrong!

 

[madpioneer]

originally posted by rushfan My local speaker repair shop refuses to sell refoam kits, claiming that the process degrades the sound of the speakers too much. This surprises me, given the popularity of the process here at AK. Nobody here seems to be concerned about this.

First off I have to ask if this came from someone at a Speaker Repair Shop what do they do? Use silicone caulking, rubber cement to fix them?:headscrat

Second I have had all four of my Mach Twos woofers refoamed due to a blow out from age. Two were done professionally at a Speaker Repair Shop here locally. The other two I did a DIY on from a foam order from the web.
Without either of these I would have to just store the speakers in the garage as tables.
They sound as good today as I always remembered. The refoam jobs did the trick. Replacement woofers are now unobtainum and would have aged foam anyway so the smart thing is to refoam. If you are afraid to do it yourself, which it is not hard find a pro that WILL do it for you and knows what they are talking about.
That is all!:yes:

 

[rushfan]

I inquired about the availablity of a refoam kit for my Paradigms and this is what I was told:

"Wrong thing to do to a woofer, as it will change the acoustic properties of the speaker forever. Pawn shops/lesser repair shops do it, but we do NOT. To refoam it meaning to repair it mechanically, without paying attention to the acoustic properties of the final product. But, many shops will do it for money".

I guess that business is good there - good enough to take a pass on this revenue stream. The shop has been is business for a long time so other than this odd bit of advice, they're probably fine to deal with.

 

[karlo]

"My local speaker repair shop refuses to sell refoam kits, claiming that the process degrades the sound of the speakers too much"


speaker repair has long been a secretive con-game . all my life i've heard the "pro's"
tell me "you won't be able to do it...you won't know how! you don't have the right
glue! the glues used in the process are SPECIAL , and we're the only ones who can
obtain them from the manufacturer" a wanna-be secret society.

i've repaired well over 100 speakers .haven't a botched one yet. used contact cement
and elmers where appropriate . with a dial caliper , razor ,and assortment of paper , i
can make all the shims i need.

 

[gkimeng]

My intuition tells me that refoamed speakers sound indistinguishable from the originals when quality surrounds are used.

If you're refoaming a 30+ year old vintage driver from a manufacturer that no longer offers an exact replacement or has gone on to that great audio salon in the sky, then the refoamed unit is definitely "indistinguishable from the original," because there are no originals in original condition to compare it to, and the real question is how the refoamed speaker compares to the closest new driver you could have bought instead.

 

[dc270]

Several people here with adequate measuring equipment. tallent and time CAN verify that refoaming is typically a reliable way to reuse the same drivers AND get as good, if not better, specs than what the speaker came with. It is simply not a black art to stay away from but a great, inexpesive, relible way to revive a good speaker.
DC

 

[onepixel]

Surrounds will degrade after 15 - 20+ years.

New surrounds will change the sound that your used too... until they get broken in.

Then they will sound brand new.

 

[rushfan]

For the record - I am a believer in refoaming. I am currently restoring a pair of JBL L26's for a paltry $22. I'd never find replacement drivers for that little. This guy's opinion froze me in my tracks. I had never heard of a speaker specialist who refused to replace surrounds.

 

[karlo]

"My local speaker repair shop refuses to sell refoam kits"

does he refuse to replace surrounds as well ? perhaps there's not enough cash in
the deal for him , compared to REALLY hosing you on a recone.

( does he recone? ... when you 'recone' , aren't you- in essence- 'refoaming' at the
same time ? where in the hell do you draw the freakin' line ? .........were these woofers'
frames and surrounds magically molded from one piece ?, or ...glued -up and assembled , as they
would have been at the factory ...?)

that's bullshit!

 

[rushfan]

"My local speaker repair shop refuses to sell refoam kits"

does he refuse to replace surrounds as well ? perhaps there's not enough cash in
the deal for him , compared to REALLY hosing you on a recone.

( does he recone? ... when you 'recone' , aren't you- in essence- 'refoaming' at the
same time ? where in the hell do you draw the freakin' line ? .........were these woofers'
frames and surrounds magically molded from one piece ?, or ...glued -up and assembled , as they
would have been at the factory ...?)

that's bullshit!

He was happy to sell me a pair of replacement woofers for $80 each. My Paradigms only cost $10 to begin with!

 

[toxcrusadr]

He was happy to sell me a pair of replacement woofers for $80 each. My Paradigms only cost $10 to begin with!

Uh-huh.

I'm a believer in keeping speakers original - i.e. repairing the original drivers. Once the surrounds are shot, you can't use the speaker anyway. To me it's like saying "Yeah, that classic car with the 4 flats, if you replace those tires it won't run like it did originally."

 

[hifi_nut]

Yeah! I bet your local dealer will replace his car´s engine when the time comes for a timing belt replacement, too.

What a load of crap. It´s painfully obvious he´s out to sell you replacement drivers.

 

[Zilch]

JBL does not sell surrounds, only complete recone kits. In theory, over the 20 years it took for the surround to deteriorate, other mechanical elements will have done so, as well, and your best shot at restoring a JBL driver to original spec is a full recone with a factory kit.

JBL factory authorized service centers are under contract to follow JBL recommendations for repair of JBL drivers. However, if the customer ASKS them to, without volunteering the options, most will also recone with less-expensive aftermarket kits, or, in the case of an otherwise good cone/spider/voice coil assembly, refoam with their best guess aftermarket surrounds.

Speaker repair guys are in the business of repairing speakers, NOT selling inexpensive surrounds, and they understandably do their best to discourage those who would DIY. Instead, they expect compensation for their time, expertise, and skill in doing what they do.

I only recone if there is no option, and I trust my repair guy's recommendation in making that decision. I care less that an L26 woofer performs 100% to original factory spec than that it works, measures well, and sounds good.... :yes:

 

[karlo]

"Instead, they expect compensation for their time, expertise, and skill in doing what they do"

my audio-tech friends , my late brother ,have told me that the "recone guys" where they
worked were always the flunkies/potheads in the shop who couldn't find their way
around an amp , were so bad at repairs ,
they were demoted to changing idler wheels and reconing speakers !

 

[Zilch]

Let me put it this way, perhaps: You find a nice pair of vintage JBLs at the thrift store, and you're gonna restore them for resale. Your eBay auction will say, "I refoamed these myself at the kitchen table using unknown aftermarket surrounds I found on the internet and Aileen's Tacky Glue from Wally World. They sound WONDERFUL," right? :

 

[gkimeng]

Instead, they expect compensation for their time, expertise, and skill in doing what they do.

As with everything, there's always the old cost/effort/benefit equation. I just had a pair of AR-3a woofers refoamed. The kit that comes with the best recommendations would have cost me $25 including shipping. My local speaker rebuilder charged me $60, including parts. I'm sure he buys his surrounds and supplies in bulk and paid way less than $25 for materials, but from my POV the difference in cost worked out to $17.50 per speaker for labor, which means I would have had to refoam both woofers in about 40 minutes and get them both right the first time with no redos, no accidentally cut cones and no trips to the emergency room to patch up something that bled to make it worth my while to do it myself.

Do they sound the same as the originals? It's been 30 years since I last heard a brand new pair of AR-3a's playing, so how do I know? All I know is, they sound better than they would have with no surrounds and I didn't spend the $300 it would have cost me for today's service replacements (which I also wouldn't have any way of comparing to the originals).