Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!cbnews!tl
From: tl@cbnews.ATT.COM (thomas.l.du breuil)
Newsgroups: rec.audio.high-end
Subject: Re: (very) Unconventional Speakers
Message-ID: <2792@uwm.edu>
Date: 6 Mar 90 22:33:14 GMT
References: <2678@uwm.edu>
Sender: news@uwm.edu
Reply-To: tl@cbnews.ATT.COM (thomas.l.du breuil)
Organization: AT&T Bell Laboratories
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Approved: tjk@csd4.csd.uwm.edu


In article <2678@uwm.edu> aipp@castle.edinburgh.ac.uk (Pavlos Papageorgiou) writes:
>	Has anybody out there investigated, or at least considered, the
>concept of a 'digital speaker'?  --- meaning a method for driving the
>cone in discrete steps. 
[...lines deleted...]

As someone else has pointed out, Bell Labs has invented such a device.
There was an article on it in the old Bell System Technical Journal (BSTJ),
circa 1980 I think.  Being the telephone company, the speaker demonstrated
was for direct digital to sound conversion of the standard U.S. 8-bit ulaw
telephone bitstream and I think it was sized to fit in a conventional
telephone handset.  I don't remember all the details, but each bit drove
a different piece of the diaphram, with the most significant bit at the
outer edge and the least significant bit in the center.  The diaphram
mechanically integrated the "bits" to produce the appropriate sound output.
I don't remember the details about how well it worked, but I guess it was
much more expensive than telephone codecs and regular phone speakers...
Maybe there will be renewed interest in this when there is general availability
of the digital bitstream in residential homes...  I don't recall if the
article said anything about a digital microphone to go with it...

Tom du Breuil

--

Thomas Krueger                        UW-Milwaukee Engineering Electronics Shop
tjk@csd4.csd.uwm.edu                            "A Veteran Of The Psychic Wars"
Moderator, Rec.Audio.High-End                                 +1 (414) 229-5172