View Full Version : JBL, why titanium,
10-30-2011, 09:03 PM
Why is it they never seemed to use anything else, on there tweeters?? Has polk ever tried it??
Lots of speaker makers use metal domes, usually Aluminum alloys or titanium. Energy, Focal, B&W, KEF, and many others.
Around the same time that JBL was developing its Titanium Diaphragm tweeter and experimenting with titanium deposits on synthetic tweeter domes, Polk introduced its SL-3000 tweeter--a metal deposit type--see Polk literature below:
Polk engineers, in conjunction with the Johns Hopkins University Center for Non-Destructive Testing, utilized Laser Interferometry to test a vast number of tweeter designs and materials in their search for high frequency perfection. This advanced application of laser technology allowed Polk to study digital holograms of tweeters in operation.
Exhaustive tests were conducted in developing a revolutionary dome which would produce perfect motion without the sonic degradation caused by standing waves. Ultimately, it was found that by vapor depositing stainless steel and aluminum on a polyamide surface, the new SL3000 dome was stiff enough to push standing wave resonance to beyond audible range (20khz), yet light enough for high efficiency and superior transient response.
JBLs own reasoning was not far from this. The Titanium diaphragm could be fashioned thinner than a human hair and yet not deform under the massive stresses of moving at frequencies above 20Khz. Low mass, high structural integrity and quick recovery are keys to reproducing the upper end of the frequency scale. Titanium is 'stonger' than steel and 'lighter' so it can be fashioned into a very thin low mass diaphragm.
Today, JBL uses a Titanium composite tweeter in its Monitor Pro series (a kind of coated Titanium dome of some kind??...from the pictures it looks like a carbon compound, perhaps).
There is more to it than this. But this is a good start.
Polk also used aluminum domes in some of its speakers such as the VM series--see product pages above!
10-31-2011, 01:06 AM
My experience with alloy tweeters has been that they are very detailed. However, they tend to be rather harsh and a little hard to tame. I am sure that there are good designs that overcome the harshness. I tend to lean toward the silk dome for smoothness wit good detail.
I find some metal domes way harsh but some are nice , the vifa alum dome is nice , the polk tri-lam is nice , I think klipsch uses a metal dome in the t-35 tweeter and some of the later ones like the ? rf-7 ?
I have grown to like a metal dome (be it a tri-lam or alum) on a center ch speaker because it gives it a centralization of sound and any harshness is not there because center frequencys die out arond ?10khz? .
But on mains I like the silk domes sl-2000 or a well setup trilam like in my plok ls-50's .
10-31-2011, 01:59 AM
you may want to try an old trick we used with the JBL two inch drivers....on the outside of the driver (tweeter) what have you...try applying a small bead of silicone to the diamond pattern surround...if you don't like it better you can always peel it off....Meyer pro sound used this "mod" fairly effectively in the eighties and nineties
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