Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/3/84; site teddy.UUCP 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: <1471@teddy.UUCP> Date: Mon, 21-Oct-85 14:14:32 EDT Article-I.D.: teddy.1471 Posted: Mon Oct 21 14:14:32 1985 Date-Received: Tue, 22-Oct-85 08:17:24 EDT References: <1395@teddy.UUCP> <1556@hammer.UUCP> <1431@teddy.UUCP> <1575@hammer.UUCP> <1459@teddy.UUCP> Reply-To: rdp@teddy.UUCP (Richard D. Pierce) Distribution: na Organization: GenRad, Inc., Concord, Mass. Lines: 54 In article <1459@teddy.UUCP> rdp@teddy.UUCP (Richard D. Pierce) writes: > >(For those reeady to flame, yes I have made some simplifying assumptions >here, but the basic relation ship of transient response and bandwidth >still hold true) > Well, for those still ready to flame, I have researched the subject a bit and have come up with some more defining descriptions of the slow-woofer nonsense. I had, in a previous article, made a hypothetical table of woofers/bandwidths and rise times that looked like this: MODEL BANDWIDTH RISE TIME ----- --------- --------- 8" woofer 2000 Hz ~.2 mSec 12" woofer 1000 Hz ~.4 mSec 65' woofer 500 Hz ~.8 mSec Using this, I then stated that crossing these each out at 200 Hz will effectively give them the same rise times, or "speed". This conclusion is essentially correct. However, in the interest of presenting more accurate and verifiable information, I looked up specific references and have found the following: The total rise time of the system is proportional to the square root of the sum of the squares of rise times of each element in the circuit. As taken from "Electric Designers Handbook", edited by Plandee, Davis, et al, pp. 13-49: 2 2 2 1/2 Tr = (tr + tr + ... tr ) 1 2 n This means that the second table of rise times (those rise times which result from a 200Hz crossover applied to each woofer) can be modified as follows: MODEL BANDWIDTH RISE TIME ----- --------- --------- 8" woofer 200Hz 2.00997 mSec 12" woofer 200Hz 2.03961 mSec 65' woofer 200Hz 2.15401 mSec The point remains the same. As long as the bandwidth of the driver is than the crossover allows it to be, then the rise time is determined by the crossover. "slow" woofers, by definition, have not the bandwidth of "fast" woofers. There is no such thing as a slow, wide bandwidth driver. As for other potential flames, no I do not know who sells 65' woofers. Nor will I reveal this information if I mistakenly stumble across it. Maybe the saga of the Hartley 24" subwoofer would be good material for the "Audio Anecdote of the ? Dick Pierce