Power supply

Behind me the 3-way crossover

Each individual revbration unit was suspended on the inside in 4 rubber bands.

A producer for a record label wanted a reasonably usable reverb for his own use.
At that time, there was no reasonable and good reverb that could be used for simple recordings.
So I decided to help him build something.

The problem and solution:
It had to be Mono in and Stereo out.
Hammond is a well-known producer of organs.
In most of these vintage organs, Hammond used a cleverly designed reverb called spring reverberation.
(I think this long spring reverb is the best ever made) These were available from Hammand wholesaler in Oslo.
At the time, Hammond provided two types of spring reverb, Low or middle impedance (Z), on the input side.
A low Z = 4 - 16 ohms and a medium Z = 1 - 2 k ohms. For this project I chose a low Z.
The idea was to use 6 Hammond spring reverbs, 3 for the left lm, and 3 for the right lm.
This type of reverb is known for its poor frequency response on bass and treble.
Therefore, a separate volume had to be arranged for each section.

We ended up with a 3-way passive standard 8 ohm speaker crossover, with separate volume for each reverb.
Used 3 pcs 8 ohm speaker attenuator (A speaker potentiometer with constant Z = 8 ohm).
We also needed a small power amplifier.
To achieve stereo out, I figured it was very common among reciprocal Hammond springs,
and this was the case.
None of the springs had the same frequency Exact range, so it was a kind of stereo....

Together we ened up with six units.

1. Box of suspension for 6 pcs Hammond organ spirals.
2. Box 3-way crossover and potentiometers.
3. Box with power supply + cables.

Usually the input impedance of the driver side varies much with the input frequency.

Therefore none reverb unit had the same frequency

I have several times later used Hammond springs for reverb.

Since the op-amp entered the world of audio systems, this type of construction has become much easier.
The secret is the very content of the driver construction itself.
To be able to achieve a better drive output in relation to the input impedance of the spring.
In addition, I used a 10 step EQ for better mutual balance.

The principle is shown in the figure below.