From jonbsherry@yahoo.com Tue Sep 16 08:19:17 2003
Subject:Organ Swell pedal

The swell pedal does come from pipe organs orginally,
but I never heard of a swell that works by varying the
air pressure going to the pipes.

The swell is a set of pipes, inside a wooden cabinet
with slats like on a window blind. These pipes are
connected to one of the organ's keyboards, called the
swell manual. The swell pedal opens and closed the
slats, causing the sound to get louder and softer.
Only the stops connected to the swell manual are
effected. As you can imagine, when the slats are
closed, the sound is somewhat muffled. So opening the
swell results in a brighter sound, as well as a louder
sound.

One might think that the Hammond, being a mediocre
clone of a pipe organ, could be trying for that effect
in its swell pedal.

Except, if the A0-28 circuit really follows the
Fletcher Munson curves, the tone should get more
mid-rangy as the volume increases.

In theory, a circuit designed to compensate for the
fletcher munson effect should be compensating for
variations in the way we perceive the tonal spectrum
at various sound pressure levels (SPLs). Basically, as
the SPL goes down, our ears perceive less bass and
treble, and that circuit should put some back in. But
as the SPL goes up the curve is flattens considerably,
and by 80dbs is fairly flat on the bass side.

So, by keeping that old stereo's loudness button on
even when the volume is cranked, you're defeating the
purpose of the loudness circuit. It basically becomes
a bass treble boost.

Likewise, pushing the swell pedal 1/4th of the way on
a Hammond M3 using the internal speaker results in a
different SPL than when you're hooked up to a
custom-amped leslie. The tone compensation circuit in
the pre-amp can't know how much of a boost the amp is
giving to the SPL.

So, it seems that the Hammond swell doesn't follow the
tonal changes of a pipe organ swell, and it can't
really track the Fletcher Munson Curves that
accurately. But it sure gives an organic dimension to
the organ tone. while a nice FC7 pedal hooked up to my
V5 is just annoying.

-jb

=====
---
Jonathan Sherry
Network & Systems Administrator
Classic Media
jonbsherry@yahoo.com
917-445-5339