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A pair of speakers that I have found (Royal Device "Laura") has foam surrounds on the drivers. Bear in mind that msrp for these speakers is around $11,000. I don't see foam surrounds being used on modern speakers much anymore, but I have been told that several manufacturers still prefer to use them.
Besides the longevity issues, are there any other reasons why foam surrounds have become unpopular?
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I used to like butyl rubber surrounds better because they lasted longer. That was until I saw the foam that Atlantic Tech used. It is both thick and flexible. I think it is impregnated with silicone. Phase tech builds good cabinets bet their foam surrounds are cheap. Foam surrounds can be of good quality but many are not.
Self-damping is probably about comparable to butyl rubber (and certainly better than pleated/treated fabric), but foam can allow for greater excursion and sensitivity due to its lower mass and higher compliance. Modern formulations are far more resistant to deterioration from temperature/humidity variations and UV exposure than those used in the 1970s and '80s. Butyl is still regarded as more durable, but it too can dry out and crack after about 30 years.
Foam adheres well to metal frames, and best to paper cones with non-toxic water-based glues. With appropriate glues, it also sticks well to polypropylene, carbon fiber, Kevlar, glass fiber, etc.
Of course foam is ubiquitous in cheap drivers because it's, well, CHEAP. But some prestigious high-end makers still use it for its beneficial properties, to achieve desired driver parameters in conjunction with other elecro-mechanical factors.
Not sure I agree it is better than pleated or treated cloth. It depends on the system and driver design. Decades ago Art JansZen of electrostatic fame licensed his technology to Neshameny(sp?) a coany that was manufacturing a great woofer using a pleated cloth surround. The coupled the 2 technologies together than the result was a woofer that beautifully transitioned to the e'stat and was as fast. Later the company discontinued the woofer and went to a dynamic tweeter, lasted a couple of years and folded. Art took over manufacturing of the JansZen using an acoustic suspension vs infinite baffle design and the woofer while good just did not do as well as the cloth pleated woofer.
ADS in the late '70s used foam and converted to butyl surrounds at the time stating the new L310 woofer with the butyl was acoustically better than the earlier foam surround L300 woofer and the ONLY difference was the surrounds. My L300 woofers were replaced by ADS with the L310 woofers at not charge under warranty. I was offered either version but had discussed this with someone in their engineering department before making a choice.
Wharfedale was the first company to use foam surrounds and within a few.years went back to the earlier, I think it lamb's wool surround.
Some companies like AR went from cloth to foam mostly because of manufacturing efficiencies and cost containment on the same speakers model such as the 3 series.
Don Brian Levy, J.D.
Toronto ON Canada
Actually new glues do a rather marvelous job with all types of materials and people like Loc-tite manufacture a range of glues with excellent adherence.
The main issue these days is that many of them are not environmentally friendly nor friendly for human breathing either.
Actually that is one reason why so many speaker subassemblies are now made in China no matter where the companies claim to be centered. The lax OSHA and EPA laws in China allow them to use quite toxic glues which entail special ventilation in the US and Europe. In addition they sweep up the heavy metal grindings from magnets right into the regular dump, if lucky.
However, Andrew Jones once told me that pleated fabric surrounds were superior for bass drivers only because their motion back and forth from the center rest was more symmetrical. But he wouldn't use them for a driver that went into the mid-range because a half roll surround damped the cone breakup better.
I have another pair of speakers (Clements hybrid ribbon monitors) that use foam surrounds on poly woofers. Going on 20 years and no sign of cracking or deterioration! But, truth be told, they have been shielded from UV by being kept been in dark storage much of that time.
Edits: 07/30/14
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