Replacing surrounds is a crapshoot because you can't be sure what compliance and Fs you will be getting. I have a pair of Focal 7K011dbl drivers and have replaced the rubber surrounds, but the rubber is thicker than the original, so Fs is 55+Hz after break-in instead of 38Hz. They look right, but the rubber is too thick. Is there a way to increase the compliance of rubber, maybe by dissolving and removing layers? Ideally a surround could be masked off and thinned in situ until Fs is reached.
My intention is to install the same replacement rubber surround kit on several throw-away drivers and learn how to tune compliance.
My intention is to install the same replacement rubber surround kit on several throw-away drivers and learn how to tune compliance.
More: I want to reduce the Young's Modulus and increase the compliance step-wise, maybe by dissolving layers of surround rubber and then scraping them off with a blade while the driver is face-up on an improvised lathe, such as an old turntable, then stop. Xylene and mineral spirits are on the list. Are there any others I should try?
No.
Xylene/toluene will redissolve raw/unpolymerized neoprene, the yellowish/brownish kind, you can dissolve a surface layer and wipe it way with a solvent wetted cotton swab or piece of cloth, but once it´s been polymerized (what you have) it´s permanent.
It will absorb some solvent and swell but not dissolve by any means, it will simply easily crumble.
You will need to get the proper surrounds.
If you want guaranteed low Fs, try plain foam ones, those which are usually greyish.
Correct
Correct
Those woofers are the best made Seas woofers I have seen.
Also those Polk speakers mentioned in this thread have good surrounds or a few of the old Polk "monitor series" or something.
I can look them up, but who cares. Have 2 passive radiators in the front I think.
See if prices go up 0% a year that is 5% inflation because everything gets made with cheaper materials.
But even if the materials didn't get cheaper, production gets more efficient and automation would make things lower in cost and other factors contribute to "deflation" also.
I believe JBL L100's were 700 USD in 1971 -- that's 20 troy ounces of gold (31.1 grams).
20 ounces of gold today is about 40,000 USD
Gold supply inflates at 2-3% a year.
Inflation is a transfer of wealth.
JBL A123 woofer would cost around 3,000 USD today, retail.
I think Chinese companies clone some less fancy Altec woofers with alnico magnets, that retail for about $1250.
Technology has created some great drivers today, but most people can't afford to buy anything like it was made even 20 years ago. Or 2019?
Then people talk about "prewar" WWI? WWI? products were well made. Preindustrial revolution?
Yeah a hand made wool rug lasts a long time, it took some one a year to make, a large one 11x16 ft for example.
A synthetic machine made ("hand tufted" typical scam PR marketing term) rug falls apart quick; go figure
Sorry but everything is garbage including the stuff you put into your body, vaccines/food.
As an American, you ever wonder why you go to Europe and you lose 10 lbs in 2 weeks? Well many factors, one of which being the food is less garbage.
Ever wonder why the autism rate is 1/44 in males in NJ USA and 1/10,000 in Germany? Over-diagnosis? Yes, but not the vast majority of it.
So, yeah, your surrounds suck. To make them only cost 5-10% more EVERY year they have to make them 5% cheaper (in quality) EVERY year or they have to make some technological magic happen
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After hearing a JBL 15" in a big box back in the sixtees I became hooked on them. Only problem, they where 6000 in my local currency, and i made 180 a month, working 6 days a week
In the seventies exchange rates and my salary improved to the point i was finally able to buy a pair of 2215 woofers for three weeks salary each.
Every time, when I saw some idiots, like the who's, destroying speakers just for fun it made me want to kill em...
In the seventies exchange rates and my salary improved to the point i was finally able to buy a pair of 2215 woofers for three weeks salary each.
Every time, when I saw some idiots, like the who's, destroying speakers just for fun it made me want to kill em...
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Hi,
Necro apologies!
I have a pair of Salk SongTowers from 2009 and the woofers (Seas CA15) appear to have this very problem. The speakers have to live in a room which gets a lot of sun and the temperature can get up to 32C in there, nothing I can do about that, the sun never directly shines on the speakers and I keep the grills on.
After about 8 years (2017) occasionally I would hear a very obvious "grating distortion" especially on vocals, lightly pressing on all four of the rubber woofer surrounds would fix it.
Fast forward to today, the problem occasionally rears its head and the pressing still fixes it.
I don't see any cracking on the rubber but there is a slight "grinding" noise when I press on the lower part of the surround.
Anyway, what to do in 2024, silicone spray dabbed on to the front and rear of the surround, if anyone has a product name I should buy (I'm in Australia) then great?
Thanks for looking!
Cheers
Richard
Necro apologies!
I have a pair of Salk SongTowers from 2009 and the woofers (Seas CA15) appear to have this very problem. The speakers have to live in a room which gets a lot of sun and the temperature can get up to 32C in there, nothing I can do about that, the sun never directly shines on the speakers and I keep the grills on.
After about 8 years (2017) occasionally I would hear a very obvious "grating distortion" especially on vocals, lightly pressing on all four of the rubber woofer surrounds would fix it.
Fast forward to today, the problem occasionally rears its head and the pressing still fixes it.
I don't see any cracking on the rubber but there is a slight "grinding" noise when I press on the lower part of the surround.
Anyway, what to do in 2024, silicone spray dabbed on to the front and rear of the surround, if anyone has a product name I should buy (I'm in Australia) then great?
Thanks for looking!
Cheers
Richard
Thanks.
I think its a lack of suppleness in the rubber surround.
Lightly pressing 360 degrees around the rubber once "fixes" it for months, it doesn't appear to be getting noticeably worse, pressing on it always fixes it.
Cone sagging, I'm not familiar with it, would that be an issue on a 5" midrange, if sagging, that is, the voice coil is off centre and rubs as the cone travels in and out, would that make a rubbing sound as I pressed around the surround, I'm doing that now and I can't hear anything?
The "grinding" noise when I press on the lower part of the surround only happened on that first "fixing" touch, it's not happening now.
The distortion that I hear when the issue pops up is mostly notable on vocals, I heard it today with Thom Yorke.
I think its a lack of suppleness in the rubber surround.
Lightly pressing 360 degrees around the rubber once "fixes" it for months, it doesn't appear to be getting noticeably worse, pressing on it always fixes it.
Cone sagging, I'm not familiar with it, would that be an issue on a 5" midrange, if sagging, that is, the voice coil is off centre and rubs as the cone travels in and out, would that make a rubbing sound as I pressed around the surround, I'm doing that now and I can't hear anything?
The "grinding" noise when I press on the lower part of the surround only happened on that first "fixing" touch, it's not happening now.
The distortion that I hear when the issue pops up is mostly notable on vocals, I heard it today with Thom Yorke.
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I have used wintergreen oil from a health food store. It softens rubber and other types of polymer surrounds but unfortunately the effect doesn't last very long.
I have some speakers with Vifa 5" midwoofers, p13 something or other. The surrounds hardened after 15ish years and nothing would bring them back for more than about 24 hours. I finally replaced them with foam surrounds and the measured T/S parameters were super close to the original specs.
I have some speakers with Vifa 5" midwoofers, p13 something or other. The surrounds hardened after 15ish years and nothing would bring them back for more than about 24 hours. I finally replaced them with foam surrounds and the measured T/S parameters were super close to the original specs.
Thanks.
I've just been tinkering with the woofers, all four, by tapping in both sides of the woofer surround at the same time I can get a subtle "scratching" sound (like fingernails gently scratching cardboard), I'm assuming (from looking at some diagrams on Google) that's the coil interacting with the magnet, not sure though, as it definately sounds more like paper scraping than metal scraping.
To me the rubber still feels pretty supple.
I'm confused 😂
I've just been tinkering with the woofers, all four, by tapping in both sides of the woofer surround at the same time I can get a subtle "scratching" sound (like fingernails gently scratching cardboard), I'm assuming (from looking at some diagrams on Google) that's the coil interacting with the magnet, not sure though, as it definately sounds more like paper scraping than metal scraping.
To me the rubber still feels pretty supple.
I'm confused 😂
rthorntn -
I'm not sure what material your surrounds are made of, but butyl rubber has natural dampening properties and is resistant to attack from oxygen. A lot of woofers have butyl rubber surrounds as a consequence. You might try looking up your Seas woofers to see if you can determine the surround composition. I just looked them up on the Madisound site, and they certainly look like they might have butyl surrounds rather than something like foam.
Edit - Actually, the spec says a natural rubber surround, so they may be prone to oxidation and stiffening over time.
I'm not sure what material your surrounds are made of, but butyl rubber has natural dampening properties and is resistant to attack from oxygen. A lot of woofers have butyl rubber surrounds as a consequence. You might try looking up your Seas woofers to see if you can determine the surround composition. I just looked them up on the Madisound site, and they certainly look like they might have butyl surrounds rather than something like foam.
Edit - Actually, the spec says a natural rubber surround, so they may be prone to oxidation and stiffening over time.