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Path: utzoo!decvax!ucbvax!ucdavis!lll-crg!seismo!harvard!talcott!panda!teddy!rdp
From: rdp@teddy.UUCP
Newsgroups: net.audio
Subject: Re: subwoofers and xovers
Message-ID: <1431@teddy.UUCP>
Date: Tue, 15-Oct-85 10:51:55 EDT
Article-I.D.: teddy.1431
Posted: Tue Oct 15 10:51:55 1985
Date-Received: Wed, 16-Oct-85 15:32:17 EDT
References: <1395@teddy.UUCP> <1556@hammer.UUCP>
Reply-To: rdp@teddy.UUCP (Richard D. Pierce)
Distribution: na
Organization: GenRad, Inc., Concord, Mass.
Lines: 72

In article <1556@hammer.UUCP> tekecs!doghouse.TEK!snoopy writes:
>Before everyone runs off and builds subwoofers with two 8" drivers,
>I'd like to point out that this isn't going to be much of a subwoofer.

Well, on the contrary, I would like to point out that I have built about
a half dozen pair of such beasts, using two KEF B-200 SP-1014's, in
properly terminated transmission lines (which I am not to successfully
avoiding to elaborate on) that were measured, anechoically, at being
-3 db at 25 Hz.

>I've seen specs for so-called "subwoofers" that doen't even go down
>as far as my AR-11s. (-3dB @ ~35Hz)  A subwoofer should go down to
>at least 20Hz, if you're into organ music there's one last note down
>around 16Hz or so.  

At the risk of resurrecting the Pierce/Grantges debate again, I should
point out that very little energy of consequence comes out of organs
at the fundamental, the vast majority (in the case of pedal reeds and
open principals, upwards of 80%) of the energy is distributed amongst
the harmonics.

>Producing these frequencies at any sort of volume
>means pushing LARGE volumes of air around.  The AR-9 has two 12"
>woofers each, and the -3dB point is 28Hz. (sigh)  You can go to larger
>drivers, but transient response will probably suffer.  

If the crossover limits the high-end cut-off to something like 200Hz,
and any loudspeaker system can get up at least that far reasonably, 
transient response will suffer only because of the crossover (neglecting
the fact that the lower cutoff also affects it as well). 

> The enclosure is also going to have to be fairly large.

No question about that!

>Yes, there are subwoofers on the market with a single 12" driver
>in, say a 14" cube that go down to 20Hz.  A friend of mine has one.
>It won't play very loud before running into problems.
>
>Of course you could set up the system in a smaller room, like a
>walk-in closet... :-)
>
>Physics by any other name presents the same restrictions.

No argument here, also.

>(BTW, no I don't have a subwoofer.  Maybe someday...)
>
> Snoopy

Well, let's note that the poster lives in a small dog house, so bass
really isn't an issue :-) (doesn't anyone sign their real names anymore?)

Here is an aside that may be of interest to you sub-woofer enthusiasts.

Several manufacturers have made an sold subwoofers based on "slot" loading
or "floor" coupling. IN the cases I am discussing here, the woofer ends
up facing downwards near the floor. Almost universally, I found such systems
to have the "won't play very loud before running into problems" syndrome.
The reason? Well, the vast majority of woofer/driver/suspension/spider/voice
coil/magnet makers make one assumption about drivers; that they will be used
in a horizontally-facing orientation. Facing a woofer up or down causes
the driver to be offset mechanically from the center of its linear 
mecahnical operating region. This then severelly reduces the amount of
linear mechanical (and electro-magnetic) motion left for the driver to
operate with. The result is that the amount of SPL before noticeable
distortion occurs is not very great.

Once again, the extensive knowledge of the designer overcomes any
limitations impossed by reality!

Dick Pierce