Modern foam compositions certainly last a lot longer than they used to, but not neccessarily longer than rubber. However, no one seems to have made the point that rubber is not just rubber. There are many different materials used for surrounds, that may have the lay appearance of rubber, but in fact are not. They may be heavily plasticiced PVC, or polypropylene derivatives, etc. Each has it's place in the design of drivers. Don't tar all surrounds with the same brush.
The choice of surround material depends on many factors. Although foam is the lowest cost, it is also the lightest which is very important for high sensitivity drivers. "rubber" is very much denser so to keep weight down has to be made thin. It then tends to invert at large negative excursions due to enclosure internal air pressure and so makes nasty noises. Another very important aspect of surrounds is how they terminate resonant modes in the cone. Their shape and material composition is critical to getting a smooth response from the driver. There is not one optimal material. What works best with paper cones may not be the best for polypropylene etc. In fact, foam still is an excellent choice with paper cones.
This does mean that replacing a foam surround with a "rubber" one will almost certainly change the frequency response of the driver, and almost always reduce the sensitivity.
The choice of surround material depends on many factors. Although foam is the lowest cost, it is also the lightest which is very important for high sensitivity drivers. "rubber" is very much denser so to keep weight down has to be made thin. It then tends to invert at large negative excursions due to enclosure internal air pressure and so makes nasty noises. Another very important aspect of surrounds is how they terminate resonant modes in the cone. Their shape and material composition is critical to getting a smooth response from the driver. There is not one optimal material. What works best with paper cones may not be the best for polypropylene etc. In fact, foam still is an excellent choice with paper cones.
This does mean that replacing a foam surround with a "rubber" one will almost certainly change the frequency response of the driver, and almost always reduce the sensitivity.
Many high efficiency drivers have a specially treated cloth surround, this is probably an area where rubber will be not very useful. I also think that most of the professional drivers do not use rubber surrounds for that reason.
But in Hifi/HighEnd there are only very few designs left which still use foam surrounds. I maybe wrong, but for me always foam was a mere budget solution.
But in Hifi/HighEnd there are only very few designs left which still use foam surrounds. I maybe wrong, but for me always foam was a mere budget solution.
Andrew you are absolutely right and put it more eloquently than I had hoped to in my original post.
As for JBL; if Grey does not consider some of their drivers in the high end league, I wish he would let people bidding ridiculous amnounts on the much sought after and highly regarded LE 8 on ebay know so that they could save their money. Of course this is only one example of many highly regarded JBL units that is in this class though I'm no great fan of the marque, one has to concede this much at least. No?
tomcat
As for JBL; if Grey does not consider some of their drivers in the high end league, I wish he would let people bidding ridiculous amnounts on the much sought after and highly regarded LE 8 on ebay know so that they could save their money. Of course this is only one example of many highly regarded JBL units that is in this class though I'm no great fan of the marque, one has to concede this much at least. No?
tomcat
No.
Price doesn't equal high end, viz. McIntosh. (Although it seems that Mc is trying to get back into the swing of things. I wish them luck. Regardless of how bad they've sounded since the '70s onwards, their equipment has always been some of the sexiest looking stuff out there.)
Want another example? Try a lot of the way overpriced California cabernets.
Grey
Price doesn't equal high end, viz. McIntosh. (Although it seems that Mc is trying to get back into the swing of things. I wish them luck. Regardless of how bad they've sounded since the '70s onwards, their equipment has always been some of the sexiest looking stuff out there.)
Want another example? Try a lot of the way overpriced California cabernets.
Grey
Gee I guess this $6000 driver doesn't qualify as top unit, nor do any other of the best Audiobahn woofers.
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How about these $500 Gs Designs?
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These $1000 Doran Orian's?
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The top of the MA-Audio line?
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The entire Earthquake sub line?
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[Edited by ThomasW on 12-06-2001 at 02:54 AM]
'Almost all'? Those I posted represent a fairly significant number of the top-end auto mfgrs.
Rollins
What part of 15+yrs (home audio) don't you understand?
You're the one with the 12pk of Titanics, right?
Why do you suppose Paul and the boys at PE have introduced the MkII version of the driver using a santoprene surround and kelvar reinforced cone? Was their goal to make an inferior driver? I think not.....
People that rant and rave about the inferiority of modern santoprene surrounds have their heads in the sand.
Responsible people, instead of those standing on soap boxes pontificating about rubber is better, rubber lasts longer, rubber is bla, bla bla... will do some research.
Start by looking at the finite analysis studies done of the materials being used. Talk with Thilo Stompler, Deon Beardon, and others on the fore front of modern driver technology.
AndrewJ
Do know how to post a regular link? If so then use img and /img, instead of url and /url
[Edited by ThomasW on 12-06-2001 at 12:24 PM]
ThomasW,
When I use the term rubber, I include synthetics such as neoprene and its variants, as long as it's solid. When I use the term foam, I specifically mean foam, i.e. something with little bubbles in it. If you're assuming that I have something against synthetics, you're incorrect. To the best of my knowledge, no one uses true rubber (i.e. a product made from the sap of the rubber tree) in speaker surrounds.
Whether or not you've grasped what I'm saying, your manners are deteriorating.
Regardless of claims to the contrary, I've never seen a driver with a foam surround last more than about ten to twelve years. If, perchance, they have managed to push that to fifteen years, I:
A) Will believe it when I see it. I've heard claims of this nature for years and years. They <i>always</i> claim that they've solved the longevity problem...and they've always proved to be, shall we say, optimistic.
B) Am still unimpressed. Why buy a foam surround when they don't sound any better, yet will decompose much sooner than a (let's call it a--) solid surround. Just to clarify, in case anyone has misunderstood--I have nothing against foam surrounds as far as sound quality, only their long-term reliability.
Grey
When I use the term rubber, I include synthetics such as neoprene and its variants, as long as it's solid. When I use the term foam, I specifically mean foam, i.e. something with little bubbles in it. If you're assuming that I have something against synthetics, you're incorrect. To the best of my knowledge, no one uses true rubber (i.e. a product made from the sap of the rubber tree) in speaker surrounds.
Whether or not you've grasped what I'm saying, your manners are deteriorating.
Regardless of claims to the contrary, I've never seen a driver with a foam surround last more than about ten to twelve years. If, perchance, they have managed to push that to fifteen years, I:
A) Will believe it when I see it. I've heard claims of this nature for years and years. They <i>always</i> claim that they've solved the longevity problem...and they've always proved to be, shall we say, optimistic.
B) Am still unimpressed. Why buy a foam surround when they don't sound any better, yet will decompose much sooner than a (let's call it a--) solid surround. Just to clarify, in case anyone has misunderstood--I have nothing against foam surrounds as far as sound quality, only their long-term reliability.
Grey
pkgum,
I haven't really noticed that it's helped any.
I once knew a guy who tried massaging that silicone stuff you use on dashboards (can't remember the name of the product) into his (foam) surrounds. He was thinking that might help. Unfortunately, I lost touch with him, so I don't know if it ultimately helped. That might be worth a try.
Grey
I haven't really noticed that it's helped any.
I once knew a guy who tried massaging that silicone stuff you use on dashboards (can't remember the name of the product) into his (foam) surrounds. He was thinking that might help. Unfortunately, I lost touch with him, so I don't know if it ultimately helped. That might be worth a try.
Grey
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