From: hsu@acuson.com (William Hsu)
Newsgroups: rec.audio
Subject: Re: Direct vs Reflecting speaker designs
Date: 25 Jan 93 23:08:29 GMT
Article-I.D.: acuson.1993Jan25.230829.13149
Organization: Acuson; Mountain View, California

gmw1@cunixa.cc.columbia.edu (Gabe M Wiener) writes:

>In article <1993Jan19.190240.359@sparky.imd.sterling.com> jim@IMD.Sterling.COM (Jim Nicholsen) writes:
>>
>>
>>The preceding would seem to say that room reflections are indeed a
>>"bad thing". However, increased reflections are listed as a "good thing"
>>in a couple of well regarded speakers (e.g. Definitive Tech "Bi-polar"
>>designs, some Magneplanar ads). Where does the truth (tm) lay?
>>

>It really depends on a number of things.

>If you design a speaker system that works via reflections...say The
>Definitive Tech bi-polar (as you mentioned), or the Miarge M-1, then
>you want a good deal of reflectivity in the live end of the room,
>because the design depends on that.  Ian Paisley up a API recommends
>that, in the ideal setup, the side walls should be reflective from the
>live end back to 2/3 of the way between the listener and speaker, so as
>to get the first reflection but no more.

>HOWEVER....when you're working with DSP, you generally do not want your
>room to be too reflective.  This is out of a need for *control*.  You can
>simulate reflectivity electronically.  You *cannot* make a reflective room
>sound dry.  Therfore, if you have t err in a DSP setup, you always want
>to err on the dry side.


It seems that you are suggesting speakers that are designed to reflect off
walls (like the Definitive Techs) are not well suited for DSP or
surround-sound applications.  Then how come their ad claims that their
speakers (combined with the BP2 rear channel and C1 center) would provide
the "Ultimate Home Theatre"?  I think someone else also mentioned on this
net that the above combination of Def speakers works very well indeed.

I am not trying to refute your statement about controlling reflectivity in
DSP applications, but I like to know what types of speakers are desirable
for surround-sound use.  I think it makes sense to use "direct" firing
speakers for front and rear channels in DSP applications, because "bipolar"
or "reflective" speakers would add uncontrolled speaker/wall interactions
that are not taken to account by the DSP/surround processor.  However, in a
lot of literature I've read, speakers with wide-dispersion and of bipolar
design are desirable in rear/effects channels because they tend to hide
away the source of the sound.  Now I'm really confused what is best.


While speaking of direct/reflective speaker designs, here's another
question:  Counting the number of response from the Bose flame wars, it 
appears that there are a lot of controversies concerning Bose's
Direct/Reflecting philosophy.  Now how come Bose failed to convince a lot of
the netters here with his design philosophy whereas other companies that
uses similiar techniques (such as Definitive Tech and Snell) are highly
rated on this net?  Perhaps I am missing the point here, maybe 8 equal-size
rear-firing drivers are different from two full-range rear drivers used by
Definitive.  Why is the controversy aimed at Bose and not of all other
reflective speaker techniques?  Aren't they based on the same philosophy?

William

-- 
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