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.
Source for Butyl rubber surrounds but only up to 8", have not tried them:
Butyl Rubber Surrounds & Kits Archives - Speaker Exchange
Butyl Rubber Surrounds & Kits Archives - Speaker Exchange
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.
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.
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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.
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.
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.
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...
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
An example of a driver with this surround material is the Vifa P13WH.
Phthalate - Wikipedia
I have these Vifa P13's and the Fs is now in the 120-135 Hz range. Is there anything to be done? Other than use them as midrange?
Thanks,
John
I have been using these for over a year and have been 100% delighted with them. I hesitate to use anything else now.
RUBBER SURROUND Kit for JBL 15" Woofers: 4331,4333,4343,4344,4350,4430,4435 | eBay
I first replaced the surrounds on my all original (09-1986) 4435’s. There is a thread on Lansing Heritage with high resolution impedance measurements if your interested.
2234 Butyl Surrounds from Japan
As has been mentioned the surround is an important piece of the system and how it acts as an impedance termination to the frame is important to the overall sound. If a piece of silicone was the answer, all would use it.
Brake fluid was (is?) different in the US and the EU hence the DOT3 (US) vs DOT4 as used in European cars. There are different rubber compounds.
The Lansaloy white foam surrounds apparently worked very well as a motional impedance transformer but the working life was very short. While DOT3 does soften them and many people aparrently use this, one would sure think the performance is severly compromised at this point.
My 4435’s surrounds lasted a full 30 years in the dry relatively clean air outside Las Vegas, not bad at all. I expect the butyl surrounds to outlast me.
Barry.
I've been thinking of installing new butyl surrounds on one of my Vifa's as an experiment and making some measurements. Can't find an exact right size replacement yet. There is a European supplier selling surrounds that are advertised as exact factory replacements for this driver but even if they are a recent manufacture, that only buys me a certain number of years before they harden and I start over. Still hunting for a solution.
John
John
Interesting. I've been whining about my AuraSound drivers. About 75% of them have cracked surrounds.
It was a bit of a mystery, because I have other woofers with rubber surrounds that haven't cracked. The only difference I noticed was that the other ones were paper coned. But your explanation makes sense.
T/S different for rubber surround TB, W-4 1320SA,neo
Hi there: Recent posts here on DIYAUDIO, caused me to run WT-3 for a TB W-4 1320SA,
neo driver (the other one is installed on a horn project). I purchased these drivers prior to a WT-3, so I do not have original T/S info. However, I found note book entry (jul12, 2004), T/S from manufacturers data sheet, Fs was 60hz. Wt-3 measured Oct 2017 Fs=101! Seems to add credence to other reports of hardening rubber surrounds (or other aging situations). Note: Also in Oct 2017, I ran WT-3 on a newly purchased Seas driver, where the info published from Seas was Fs=31hz and WT-3 was amazingly 30.94! and other T/S was very close to published Spec. Hope this adds to the general data to the subject of driver aging. ...regards, Michael
Hi there: Recent posts here on DIYAUDIO, caused me to run WT-3 for a TB W-4 1320SA,
neo driver (the other one is installed on a horn project). I purchased these drivers prior to a WT-3, so I do not have original T/S info. However, I found note book entry (jul12, 2004), T/S from manufacturers data sheet, Fs was 60hz. Wt-3 measured Oct 2017 Fs=101! Seems to add credence to other reports of hardening rubber surrounds (or other aging situations). Note: Also in Oct 2017, I ran WT-3 on a newly purchased Seas driver, where the info published from Seas was Fs=31hz and WT-3 was amazingly 30.94! and other T/S was very close to published Spec. Hope this adds to the general data to the subject of driver aging. ...regards, Michael
