[rollei_list] Re: Completely OT- Loudspeaker info
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Tue, 15 Feb 2005 16:08:55 -0800
----- Original Message -----
From: "Jerry Lehrer" <jerryleh@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, February 15, 2005 10:06 AM
Subject: [rollei_list] Re: Completely OT- Loudspeaker info
> Akhil,
>
> We have had Likwitz as a guest speaker at our audio club.
>
> I am intimately familiar with his and his associate,
> Riley's,
> theories on crossovers
>
> I have an active crossover in which I can plug in a card
> which can be configured to any order. The Likwitz-
> Riley 2nd order is not to my liking.
>
> Jerry
>
> "A. Lal" wrote:
>
Boy is this a name from the past. I still worked for HP
when Linkwitz published his paper on crossovers. He was not
the first to suggest the use of low level crossovers nor of
phase matching crossovers. I remember my friend Richard
Heyser, who had some fame in audio himself, being very
skeptical of this system.
Low level crossovers and individual amplifiers are a very
good idea for several reasons but this is a different issue
from the nature of the crossover itself. Crossovers are
still something of a compromise but the ability to introduce
delay at will using digital circuitry allows a much closer
approach to the ideal where the acoustic fields of the
individual speakers add in a way that approximates a single
source.
I have no idea what he is doing with the very strange
looking cabinets shown on the web site. Dipole suggests to
me that the backwave is being radiated directly. I remember
some talk of dipole speakers in the distant past and, by
memory, that the idea was based on a misunderstanding of the
way loudspeakers radiate. The text on the web site is chock
full of the sort of hype which is so familiar in consumer
audio. My once golden-ear hearing is no longer good enough
to make judgments about some aspects of audio system
performance but I can still tell the difference between
loudspeakers, at least other than the very top frequencies.
It would be interesting to compare is speakers with good
conventional systems.
Many years ago I worked with Dick Heyser on his method of
making acoustical measurements called Time Delay
Spectrometry. I tried at the time to get HP to buy the Cal
Tech patents, they wouldn't and assured me that the system
wound't work. In fact, I was making such measurements using
a standard HP spectrum analyser at the time! HP then tried
to break the Cal Tech patent. Cal Tech has very good patent
attorneys so they had no luck. Cal Tech would have sold the
patent rights for very little so I think there was a large
dose of "not invented here" about the whole thing. Another
company finally picked them up and made the equipment
commercially. HP had to modify the tracking generator in its
spectrum analysers to avoid an infringement.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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