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From: dca@edison.UUCP (David C. Albrecht)
Newsgroups: net.audio
Subject: Re: Reply to Herb Chong (A/B CD, Bose 901)
Message-ID: <475@edison.UUCP>
Date: Thu, 25-Apr-85 09:22:39 EDT
Article-I.D.: edison.475
Posted: Thu Apr 25 09:22:39 1985
Date-Received: Sun, 28-Apr-85 23:36:55 EDT
References: <3623@alice.UUCP>
Organization: General Electric Company, Charlottesville, VA
Lines: 84

> Herb Chong made the following claim in a prior article:
> 
> > The BOSE tends to be very forgiving of suboptimal sources, and might
> > lack the resolution to differentiate between the players.
> 
> I asked him for evidence to support his claim.  He responded by giving
> me arguments (not evidence) to support a completely different claim --
No, what we have here is a failure to communicate since, like religion
open mindedness to criticism of ones favorite piece of stereo is like
attacking ones faith.  People who cannot reason well enough to follow
a simple and easily provable argument get no respect in my book, I
certainly don't feel compelled to get numbers scribbled on a sheet
of paper to give to this person and how do you measure imaging anyway?
> namely, that he thinks Bose 901's have significant design problems.
> Here's what he says, and here are my comments on his remarks.
> 
> > for starters, by its very design, the Bose 901's are nonlinear phase
> > transducers.
> 
> I'm not sure what this statement means.  Is this somehow supposed
> to summarize what follows?
> 
I assume he means that using equalization to produce a (semi)linear
reponse from a speaker as in the 901s intrinsically produces phase
shifts in the affected parts of the frequency spectra.  Some discussion
has been made to the effect that this hurts imaging but this is definitely
not conclusive.
> > the primary sound is from the rear speakers which reflect
> > off of the walls and back into the listening area.  great cancellations
> > occur between the back sound wave and the one from the front speaker.
> 
> This is true of any loudspeaker in any room with partially reflecting
> walls, floor, or ceiling -- in other words, any room but an anechoic
> chamber.  Believe me, having an anechoic chamber for a living room
> would be very uncomfortable indeed!
> 
> It is far from obvious to me that these problems should be any more of
> a problem with 901's than anything else.
Horse pucky, a major portion of the high frequency energy of the 901's
comes off the walls, an artificially induced condition and one certainly
not true of most loudspeakers where most reflective energy is considerably
reduced in amplitude.
> 
> > there are 8 drivers in the back.  even if each were an ideal point
> > source, the combined is anything but, and after reflecting off of
> > uncontrolled wall surfaces with absorption curves that can be wildly
> > different between setups, flat freqency response can't be guaranteed
> > even with equalization.
> 
> So far, you haven't said anything that isn't true of any loudspeaker.
> 
Both parties are to some degree right but, certainly the 901's are much
worse in this respect because of their degree of reflected energy.

The major points that I have seen about the 901's

  Overdriving drivers to produce low and high frequencies produces a
  great deal of IM distortion.

  Splattering the high frequencies all over the rear wall of the
  room while giving a dispersed sound stage will certainly not
  give any ability to localize sources (i.e. the imaging sucks,
  in my opinion the Polk SDA, Carver sonic hologram, etc. approach
  is much better).  This is an OBVIOUS point to any but the most
  brain damaged.  This is why everyone is hopping on the person
  that submitted the CD review (personally I enjoyed the review
  but some people have no humor).

  They are more sensitive to placement and room furnishing due
  to their reflective nature (again OBVIOUS).

  Frequency dependent phase shifts are induced by the equalization
  network which is required to get semi-linear frequency response.
  This is possibly not an important point but it is a point.

Now this is not to say it isn't a perfectly fine speaker if you
like the spread sound stage, don't care about the lack of localization
of images, and like the way it sounds in your room.

I certainly agree that it is not a suitable speaker for monitoring since
imaging is certainly a factor in such evaluation.

David Albrecht (My opinions have always been and always will be, my own)
General Electric