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Rubber Surrounds Hardening With Age
Rubber Surrounds Hardening With Age
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Old 10th October 2017, 05:39 PM   #61
PB2 is offline PB2  United States
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Quote:
Originally Posted by riker1384 View Post
I worry about this in regard to my PSB Stratus Gold-i's. They have some white-ish discoloration of the black midrange surrounds. This seems to be common for this series, as I can see it on other Stratus speakers for sale on eBay and such. They appear to be just fine in terms of flexibility for now but I wonder how they will fare in the future, and if they might have subtly degraded performance that I'm not aware of.

I've seen Ken Kantor comment on Audiokarma that you can't properly replace the surround on a midrange cone. He said at these frequencies the details such as the exact material, shape and even the temperature and amount of the glues applied can greatly change the frequency response.

"Refoaming a midrange": Refoaming a midrange - AudioKarma.org Home Audio Stereo Discussion Forums
The Stratus Gold midrange is a custom version of the P17 Vifa with a 1" VC rather
that the slightly larger catalog version. You can buy the catalog version new under
the Scan Speak name by the way, even today. It is a very nicely engineered mid
with a very smooth response. I would not worry about the discoloration unless it
begins to feel stiff or there are audible changes in the system. The very small closed
box is the dominant compliance for the Stratus Gold mid so some shift in Fs should
not cause an issue. I would not try to redo the edge unless Fs measured way off.

I still have not redone my woofers, the systems sound fine.

I simulated the FR change in the vented bass section based on the Fs shift in our woofers
and the low bass (< 80 Hz) was shifted down a dB or 2.
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Old 10th October 2017, 05:44 PM   #62
PB2 is offline PB2  United States
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Source for Butyl rubber surrounds but only up to 8", have not tried them:
Butyl Rubber Surrounds & Kits Archives - Speaker Exchange
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Old 10th October 2017, 06:26 PM   #63
Fernando R is offline Fernando R  United States
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Over an 18 year period, the fs of my P17WJs has increased from 42Hz to 80Hz, and my P13WHs have gone from around 68Hz to 112Hz. This is using the exact same CLIO 4 setup so it is not different measurement techniques, it's just plain hardening of the surrounds. I am more concerned with the upper frequency response from the extra resistance since the change is not limited to compliance.


By contrast, My Vifa M26WR 10" woofers have only changed fro 27Hz to 29Hz over the same time span. These surrounds were much larger and softer to start with. These woofers had a hard paper cone and were the predecessors of the PL26WR and the new Scan 26W/8434 Discovery. They were great woofers. I believe a version of this woofer was used in the PSB Stratus Gold.
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Old 10th October 2017, 11:18 PM   #64
PB2 is offline PB2  United States
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Originally Posted by Fernando R View Post
By contrast, My Vifa M26WR 10" woofers have only changed fro 27Hz to 29Hz over the same time span. These surrounds were much larger and softer to start with. These woofers had a hard paper cone and were the predecessors of the PL26WR and the new Scan 26W/8434 Discovery. They were great woofers. I believe a version of this woofer was used in the PSB Stratus Gold.
The original Status Gold employed a very nice stamped frame woofer that looked like
something Eminence might do. Paper cone, bumped back plate, rubber edge takes
power very well. Probably had a kapton former as it did compress at VERY high levels.

Don't know about the Gold-i but I did tell Paul Barton about the thermal compression
and suggested that the port probably compressed also and should be bigger.

Last edited by PB2; 10th October 2017 at 11:29 PM.
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Old 10th October 2017, 11:28 PM   #65
PB2 is offline PB2  United States
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Quote:
Originally Posted by Fernando R View Post
Over an 18 year period, the fs of my P17WJs has increased from 42Hz to 80Hz, and my P13WHs have gone from around 68Hz to 112Hz. This is using the exact same CLIO 4 setup so it is not different measurement techniques, it's just plain hardening of the surrounds. I am more concerned with the upper frequency response from the extra resistance since the change is not limited to compliance.
It seem to be safe to assume that some very different rubber types are used.

I agree that the edge changes in the smaller drivers might alter the breakup modes,
might be interesting to look into.
I measured the PSB drivers sometime back in the mid 1990s, probably 1997.
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Old 10th October 2017, 11:54 PM   #66
phivates is offline phivates  United States
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Nice to see you here PB2
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Old 12th October 2017, 02:16 AM   #67
Top Shelf is offline Top Shelf  Canada
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Sorry off topic but related.
I've used 25 year g.e. pure silicone caulk on 4 infinity 6" drivers that the foam surround was starting to crack on.
Let it dry a couple of days and presto back to normal.
Sealed up the cracks as they did not open again.
Used a flat bristel fine art paint brush to apply it till smooth.
Did not measure drivers before or after so ymmv.
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Old 12th October 2017, 11:59 PM   #68
phivates is offline phivates  United States
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I have seen some instances of cone doping slopped onto the surrounds and leading to cracks but otherwise the "rubber" surrounds in my collection are still soft and flexible. Maybe it's our temperate climate. Oddly the only foam surrounds from the eighties that are still good are on certain RS drivers. Meanwhile the ScanSpeak and SEAS drivers from that time are projects in the repair queue. Then there are the yellow fabric ones...
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Old 13th October 2017, 12:08 AM   #69
andy2 is offline andy2  United States
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Mine seems fine after all these years. The mid driver seems fairly soft to the touch and does not show any sign of hardening. I gave it a gentle squeeze and felt alright.
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Old 13th October 2017, 07:44 AM   #70
smndao is offline smndao  Denmark
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The cause of the problem is that many rubber surrounds are not made from true rubber but plastic that has been mixed with phthalate. And the phthalate will evaporate over time thereby turning the surround in to plastic.

An example of a driver with this surround material is the Vifa P13WH.

Phthalate - Wikipedia
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