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Multi-Way Conventional loudspeakers with crossovers

Rubber Surrounds Hardening With Age
Rubber Surrounds Hardening With Age
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Old 11th January 2006, 07:15 PM   #21
Joseph Hynes is offline Joseph Hynes  Denmark
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Default What to do with a dying speaker

What to do with a dying speaker:

You can turn it in to recycling, and be satisfied you've done your part to save the planet. ....ooooor......

You can recycle it more creatively, by selling it on Ebay.

You take a picture of it from a distance, so noone will notice the cracking suspension. Choose the angle well, or de-focus the camera just a touch.

Play up the brand name and put a link to the brand manufacturer's web site. Put in links to vendors showing current prices for the item being sold new.

Say you're not the one who used it (your brother, or dad, maybe) so you don't know much about it, but it was well cared for.

If that model is no longer made, you call it vintage. A collectors item. A must for any true afficionado.

State that "What you see in the picture is what you get". Makes you sound honest, but you're actually washing your hands of any responsibility.

"Looks to be in excellent condition!" ( Even a moron can tell you there's something wrong with that sentence. I don't think this line even existed before Ebay).

Use big words that appeal to the girl-hungry teen with the lowest brain-to-pocket ratio: "Awesome"..."Outstanding"..."Incredible"..."Brutal "..."Monster"..."will blow your brains out!"

Use confusing double-talk, like ":Guaranteed non-DOA".... but "All sales are final".

"Ask all questions before you bid"... sure makes you sound cooperative, but it does nothing more than place all responsibility in the buyer's lap.

If anyone asks questions about performance, answer with links to the manufacturer's current specs for the NEW item.

Sternly underline that anyone who is not **serious** shouldn't bid.
It systematically makes all those unwilling to bid on your junk not-serious. It also portrays you as a righteous crusader for the forces of good, who is, unfortunately, surrounded by too many idiots.

Cut and paste a long page of legal mumbo-jumbo (from other vendors) at the end of your page. Be sure to include a desclaimer like ..."blah blah blah...based on information believed to be accurate... blah blah...not responsible for any typing errors...blah blah.." to make sure you don't have a subpoena landing on your desk.

----------------------------------------------

PS
You should read the above three times before deciding to buy a speaker on Ebay.

Joseph
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Old 13th January 2006, 12:18 PM   #22
PB2 is offline PB2  United States
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Default SEAS Drivers From 1971 ad 1990 Are In Spec

I had intended for this thread to be about compliance shift over time in rubber surrounds in the hope of finding trends in materials, manufacturers, or the environmental exposure. I do welcome the input concerning preservatives and restoring treatments.

About what to do with a failing driver. Both US made 10" drivers in my systems, custom drivers by the way, use the same rubber edge. I purchased rubber replacement edges and they were an exact fit the part number (rr 1004) on the replacement edges is the same. I know that one of the manufacturers rebuilds the drivers for a fee, not sure about the other.

Some surprising information. I have a pair of Dynaco A-25s that I bought recently purely for the purposes of reverse engineering. The woofer used in the early production model was a SEAS 25 TV-EW with an ALNICO magnet. SEAS has a suggested ceramic magnet replacement 25 F-EW which is what was used in this system. The surprise is that both are well within specification going by the free air resonance one from 1971 and the other from 1990.

I noticed in listening to the systems that the one with the ceramic magnet was significantly more efficient and measured it midband as 3dB more. The data below shows only 2dB but it is a theoritical midband value. I believe that the cone behavior is slightly different providing a bit more output midband. This is probably the driver used in the A-25XL model from Dynaco.

Here's the data:

SEAS 25 TV-EW UNIT SAMPLE: PLB#1 1/12/06
UNIT DATE: 25 week of 1971
Rubber surround part number: SR 231/1
Effective cone diameter = 21 cm measured
Effective cone area = 285 cm^2 old SEAS spec, 350 cm^2 new (25F-EW)
seems the old spec of 285 cm^2 was an error and might explain
the difference in moving mass below:
SEAS
Delta M 15.75 Spec
Fshift -16%
Fs 23.6 20-25
Vas 205
Re 5.7
Qe .48
Qm 4.2
Mms 37.5 30
no .36
SPLref 87.6 88
Bl 6.6 .8
Qts .43
Cms .


================================================== ======================
SEAS 25F-EW(H250) UNIT SAMPLE: PLB#2 1/13/06
UNIT DATE: 48 week of 1990
Rubber surround part number: SR 231/1
Effective cone diameter = 21 cm measured
SEAS Spec effective cone area = 350 cm^2
SEAS
Delta M 15.75 Spec
Fshift -15%
Fs 27.4 26
Vas 144 175
Re 5.5 5.8
Qe .49 .39
Qm 3.9 3.8
Mms 39.6 33
no .58
SPLref 89.6 89
Bl 8.8
Qts .44 .35
Cms .85
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Old 13th January 2006, 02:08 PM   #23
DanWiggins is offline DanWiggins  United States
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ALL mechanical systems will break down with age. Foam surrounds may deteriorate, but rubber ones will harden. And of course the spiders will also break down.

In general, you should consider the "lifetime" of a speaker to be 5-8 years; older than that and it will most likely have significant shifts in T/S parameters meaning the alignment will have changed. A recone is often called for, as you need to typically replace the surround and the spider.

Dan Wiggins
Adire Audio®
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Old 15th January 2006, 03:20 PM   #24
PB2 is offline PB2  United States
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The above SEAS data has me wondering about this, it seems that deterioration depends strongly on environment and the materials used. The automotive environment is much more harsh with chemical and temperature considerations and rubber engine parts usually last longer than 5 to 8 years. It seems there is hope for vintage speakers however it should probably be taken on a case by case basis.

It is suggested at this site that Butyl rubber will have long life when not subjected to a harsh environment:
http://www.baxterrubber.com/butyl.html

Pete B.
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Old 27th June 2007, 05:50 PM   #25
PB2 is offline PB2  United States
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Quote:
Originally posted by PB2
Thank you Joseph, very informative. Turns out my dad is also a chemical engineer and a retired polymer expert so I hear a lot of this talk. Do you know if silicone oil in general is as good as Armor All?

Any products that might help after the damage is done, I don't have any that are cracked and falling apart just loosing their compliance.

I'd like to ask, if you don't mind what brand drivers those are with surrounds that cracked. I'll try to find out what type of rubber was used.

Thanks again,
Pete B.

I was about ready to put a new rubber edge on this driver and thought that I'd try some treatment before proceeding. I asked my dad, a retired polymer expert, and he suggested WD40 to try as a last resort. I applied it keeping it away from the cone so as to not alter the cone or glue joint. I did this on 9/18/05 some time ago.

This edge is an RR-1004 which seems to be a fairly common US 10" rubber edge. I don't know the type of rubber used.

Date: Fs
9/18/05 21.7 Old stock driver
9/18/05 19.9 after first application of WD40
9/18/05 19.6 after second application
9/23/05 18.5 after 3 more applications
7/27/07 18.5 nothing done since previous applications (temp = 80 deg. F)

The shift is significant considering the relation of Fs to compliance.
I have no idea what the long term effects will be with WD40 but it seems to have helped in this case.
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Old 27th June 2007, 09:20 PM   #26
Juergen Knoop is offline Juergen Knoop  Germany
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what about applying talcum? We used it in 'cable maintenance'.
regards
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Old 27th June 2007, 09:49 PM   #27
3-LockBox is offline 3-LockBox  United States
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Quote:
Originally posted by Joseph Hynes
spray the surrounds with a silicone-based conditioning product (like Armor All) to keep moisture and oxygen out of the rubber. Spray BOTH sides -- you have to get behind the speaker element.


What about mineral oil?
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Old 28th June 2007, 12:08 AM   #28
David Gatti is offline David Gatti  Australia
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A few questions/points :
Can we expect the latest generation of rubber surrounds to be better in terms of long term reliability/performance?
Why "spray-on" silicon? Wouldn't it be much more accurate and safer to wipe it on?
In the case of a midrange driver, where thiel/small paramaters are not as relevent, does it matter, or would the hardening surround increase cone-surround wave reflections (and hence greater in-band resonances) resulting frrom a poorer impedance termination?
In Australia the government has mandated the use of fluoroescent globes and the phasing out of incandescent types (to reduce energy demands). Other countries are following suit. Will this be a concern? Are fluorescent lights really more detrimental to rubber/polymers?
Since there are so many unknowns, I really think all DIYers use grills to protect their drivers, (assuming regular grill cloth absorbs UV light!)
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Old 28th June 2007, 03:31 AM   #29
CeramicMan is offline CeramicMan  Australia
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Default Re: Silicone spray lubricant

Quote:
Originally posted by PB2
Somehow it's major ingredient: "Aliphatic petroleum distillate" does not sound like silicone.

Aliphatic = free of aromatic/benzine compounds, so it shouldn't eat rubber and won't give you cancer.

Petroleum distillate = mineral oil.

Music shops stock it as a valve lubricant for brass instruments, and that stuff's practically food-grade. No Ralph, you can't drink it

Make your own minds up, but I'd probably just use a small amount of pure oil than risk adding solvents with the so-called "silicone" stuff.
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Old 28th June 2007, 05:14 AM   #30
PB2 is offline PB2  United States
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Quote:
Originally posted by David Gatti
A few questions/points :
Can we expect the latest generation of rubber surrounds to be better in terms of long term reliability/performance?
Why "spray-on" silicon? Wouldn't it be much more accurate and safer to wipe it on?
In the case of a midrange driver, where thiel/small paramaters are not as relevent, does it matter, or would the hardening surround increase cone-surround wave reflections (and hence greater in-band resonances) resulting frrom a poorer impedance termination?
In Australia the government has mandated the use of fluoroescent globes and the phasing out of incandescent types (to reduce energy demands). Other countries are following suit. Will this be a concern? Are fluorescent lights really more detrimental to rubber/polymers?
Since there are so many unknowns, I really think all DIYers use grills to protect their drivers, (assuming regular grill cloth absorbs UV light!)
Good quesions, I sprayed the WD-40 onto a paper towel and then rubbed in on as you said.

I think it does matter for cone break up and edge termination issues in a midrange.

Seems the older European drivers did fairly well and I'd guess that it was Butyl rubber, but it is just a guess. I do think Phillips/Norelco advertised the use of Butyl rubber, going from very old memory here.

Pete B.
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