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From: michaelk@tekmdp.UUCP (Michael Kersenbrock)
Newsgroups: net.audio
Subject: Re: Experiment on audibility of speaker phase response
Message-ID: <2250@tekmdp.UUCP>
Date: Sun, 25-Sep-83 18:16:50 EDT
Article-I.D.: tekmdp.2250
Posted: Sun Sep 25 18:16:50 1983
Date-Received: Wed, 28-Sep-83 02:25:21 EDT
References: tektroni.1398
Lines: 24

It seems to me that if you add an additional tweeter to a speaker
system, and move it around, what probably is being changed is not the 
"phase response" per se, but the high frequency directionality
patterns.  When there are two sources (like in an RF antenna phased
array, say, like a simple two element Uda-yagi) substantial interference
patterns result.  Moving one source a substantial portion of a wavelength
(not far for 20Khz audio) should really move things around direction-wise
and probably would mask any phase (group delay) effect.

Unfortunately even with a single source, moving the source has great
effect on interference patterns in respect to wall reflections, etc.
(This would be one good reason to move one's speakers around the room for
best imaging). Additionally, it would be a technically useful thing
to correct for groupdelay effects, but unless the speaker has 1/3 octive
drivers to be moved about it might not be too practical on a post design
basis.

Tweeters are generally known for high directionality, and so, it would
probably be quite useful to have a pointable tweeter should the rest
of the speaker cabinetry have to be fixed in some way (say for aesthetics).

Mike Kersenbrock
Tektronix Microcomputer Development Products
Aloha, Oregon