[sdiy] reverb - the catch?

[JH.]

I just read the patent.

It's truly brilliant, but there is a catch:

As far as I understand it, you cannot do this with your standard Accutronics 
tanks;
you have to roll your own spring: something designed to pass ultrasonic 
signals.

(If you can do this - and they even give the formula of the material, the 
dimensions, and the temperature of the oven in the patent! - you'll have 
something that probably is far better, and certainly a lot easier to achieve 
than what I originally intended to do.)

JH.



----- Original Message ----- 
From: "JH." <jhaible at debitel.net>
To: "Eric Brombaugh" <ebrombaugh at earthlink.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, December 30, 2006 11:22 PM
Subject: Re: [sdiy] reverb


Wow!

hats off to your father.
He filed this patent the year I was born.

I'm downloading it right now ...
(http://www.pat2pdf.org/patents/pat3136853.pdf)

JH.


----- Original Message ----- 
From: "Eric Brombaugh" <ebrombaugh at earthlink.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, December 30, 2006 10:56 PM
Subject: Re: [sdiy] reverb


JH. wrote:

> Imagine this:
>
> * Reverb tanks used in pairs to get rig of the sproing.
>
> * Two such pairs used with a crossover and two frequency shifters, to
> process the 5 ... 10kHz part

Interesting. Years ago my father worked for Baldwin Piano & Organ and
got a bunch of patents on a spring reverb system the worked in the
ultrasonic frequency range. (US Pat #3136853, June 1964)

He amplitude modulated the audio up to ultrasonic range and picked it
off with a synchronous AM detector (used the original modulating carrier
for demodulation). The advantages were:

* Allowed filtering out audio-range mechnical noises (sproing)
* operated the reverb in a range where frequency response was flatter
* Got around Hammond's reverb patents :)

There are a few other interesting things in that patent, including some
stuff on the mechanical theory of this architecture, as well as a random
frequency variation imposed on the modulation carrier which caused some
musically useful changes in the reverb characteristic.

Eric