I realize this is probably an economic limitation, but it seems to me that a
few "price-no-object" driver manufacturers should be making something like
this:

I have some Dynaudio Acoustics woofers that are 8" and have 4" dia voice
coils. For their size, they sound incredible, big, deep, loud and very
responsive to transients, not to mention the power handling of 300W.

Now, I work with a lot of 18" woofers in sound reinforcement applications,
but the voice coil sizes are rarely larger than 3" or 4". I know there is a
British company called Precision that makes 21" woofer with 6" voice coils,
but if we consider the scale of things, an 18" woofer should do amazing
things if it had a 10" voice coil. The larger coil reduces the length of
unsupported piston area, provides enormously more power for accurate
transients, and has more rigidity against lateral movement. Plus with a
motor this large, the Xmax could be huge. Imagine an 18" woofer with a
redesigned skiver/suspension surround and the ability to stroke 8". Such a
driver would displace the volume of twenty 18" conventional woofers and be
capable of infrasonic low frequency extention.

In a sound reinforcement situation that is not a permanent installation,
such a driver would be the holy grail--just hook up a 10kW amplifier to it
and rock the house. While such a driver might have a 100lb magnet structure
(and if price is no object, we could make that a lighter weight neodymium
magnet), the benefit of having just one, heavy cabinet, over hauling two
dozen cabinets would be enormous.

And for the ultimate "Bass Pigs", such as this author :-) , this would be
the ultimate loudspeaker that could take over the neighborhood without
taking over the livingroom decor.

I've been thinking about this concept occasionally for the past 6-7 years.
It should be a reasonable progression. If Bob Carver can invent an 8"
subwoofer with a 2.35" stroke, then by golly, it should be possible to scale
this design up to an 18" driver.

I feel that 18" drivers have undersized voice coils. They could be larger,
both extending power handling, Xmax, upper frequency usefulness, transient
response and efficiency. Such drivers would really be useful for extreme low
frequency output, as of course, Doppler limits the maximum speed the piston
can move without causing audible pitch shifting.

Are we really at the technological limit with 5" voice coils on 18" drivers?


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Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
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