[rollei_list] Re: Completely OT- Loudspeaker info a pop up question

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <rollei_list@xxxxxxxxxxxxx>
  • Date: Thu, 17 Feb 2005 13:52:40 -0800

----- Original Message ----- 
From: "John Jensen" <jwjensen356@xxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, February 17, 2005 8:20 AM
Subject: [rollei_list] Re: Completely OT- Loudspeaker info a 
pop up question

>I don't think that Altec Lansing had a Peerless line
> of speakers.  However, there was a highly regarded
> transformer maker named Peerless that was acquired by
> Altec Lansing.  Peerless output transformers were
> highly regarded back in the golden age of audio.
> Then along came David Hafler and Herbert Keroes
> (spelling?) and formed Acrosound with their
> transformers.  Hafler later spun off from Acro forming
> Dynaco making audio output transformers which seemed
> to be a knockoff of Acros.  Acro and Dynaco output
> transformers were also highly regarded.
> John
   Acro transformers were excellent. In fact, they were used 
in the amplifiers of the Westrex Stereo disc cutting system. 
Haffler was one of the first to understand than the inherent 
bandwidth of feedback amplifiers had to much wider than the 
"usable" bandwidth. A powe amplifier with 20 db of feedback 
(typical) must have a bandwidth of around 100khz to cover up 
to 20khz. Few output transformers prior to the Acro would do 
this. Frank McIntosh was another who understood the 
requirement for transformers in feedback systems. His real 
contribution was the design of an economical winding method 
that allowed very tight coupling and very low parasitic 
reactances in a transformer. The split load idea of the 
McIntosh amplifier was actually an old idea. The Acoustical 
Quad amplifier beat him to a commercial version of this. 
McIntosh was able to run his first amplifiers in class B 
because of the transformer but this really not a good idea 
when feeding loudspeaker.

Richard Knoppow
Los Angeles, CA, USA

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