Tahoebrian5
Fractal Fanatic
Audioscape is releasing a recreation of this analog 12-spring reverb. Would be super cool to model it in the axe.
I am pasting the discussion of how this works below. It was an interesting read for sure.
And here is a demo with sounds. Pretty cool that it has separate levels for different bands also.
I thought it might be a good idea to expand on the "equally-tempered" tuning and how it is used to create a stereo image.
I mentioned earlier that the tuning followed a log progression similar to the musical scale. I'm not an expert on music theory but I had enough piano lessons as a kid to know that an octave represents a doubling in frequency and that there are 12 notes spanning that doubling in frequency. Each note is the 12th√2, or about 5.946% higher than the one below it.
The equally-tempered reverb follows a similar log progression that would be identical to the musical scale except for one thing: The span is a factor of 3 not 2. This is due to how the Accutronics springs work. A driver at one end rotates the spring and is picked up by a transducer at the other end. The length of the spring determines the delay. This initial delay creates the "first order" echo. The following echos follow a longer path and have to transverse the spring two more times to return to the pickup. When the signal bounces off the pickup the first time it has to transverse the spring in reverse and then reflect back off the pickup and transverse the spring in the forward direction again before being picked up the second time. The second set of echos arrive at time T*3. If the first echo of the shortest spring is 13.5 ms the remaining springs have to follow a log progression that fits between 13.5 ms and 40.5 ms.
The 305 uses 12 springs to provide lots of diffusion. It has 12 "notes." The tuning interval is the 12th√3 making each successive spring about 9.587% longer than the last one. The log progression is exactly the same as the musical scale when adjusted to span a tripling in delay (inverse frequency) instead of doubling.
To create a nice wide stereo image the left and right channels timings are interleaved. Odd-numbered lines are assigned to the left channel; the even-numbered to the right.
When hit with a pulse they look like this:
The first-order echos are to the left of the cursor; the beginning of the second-order reflections to the right. The acoustic path difference of the left's first echo and the right is about 3-1/2 feet.
The 305 can take a mono input and provide a nice wide reverb field. In situations where maximum diffusion is needed mono in/mono out provides twice the diffusion because the left and right channels compliment each other.
Left and Right will always sound slightly different because when heard individually they're slightly different rooms or two different observation points in the same room.
While this may sound easy anyone who has had to cut the springs to make one of these can attest that it's not. It's a LOT of work.
I am pasting the discussion of how this works below. It was an interesting read for sure.
And here is a demo with sounds. Pretty cool that it has separate levels for different bands also.
I thought it might be a good idea to expand on the "equally-tempered" tuning and how it is used to create a stereo image.
I mentioned earlier that the tuning followed a log progression similar to the musical scale. I'm not an expert on music theory but I had enough piano lessons as a kid to know that an octave represents a doubling in frequency and that there are 12 notes spanning that doubling in frequency. Each note is the 12th√2, or about 5.946% higher than the one below it.
The equally-tempered reverb follows a similar log progression that would be identical to the musical scale except for one thing: The span is a factor of 3 not 2. This is due to how the Accutronics springs work. A driver at one end rotates the spring and is picked up by a transducer at the other end. The length of the spring determines the delay. This initial delay creates the "first order" echo. The following echos follow a longer path and have to transverse the spring two more times to return to the pickup. When the signal bounces off the pickup the first time it has to transverse the spring in reverse and then reflect back off the pickup and transverse the spring in the forward direction again before being picked up the second time. The second set of echos arrive at time T*3. If the first echo of the shortest spring is 13.5 ms the remaining springs have to follow a log progression that fits between 13.5 ms and 40.5 ms.
The 305 uses 12 springs to provide lots of diffusion. It has 12 "notes." The tuning interval is the 12th√3 making each successive spring about 9.587% longer than the last one. The log progression is exactly the same as the musical scale when adjusted to span a tripling in delay (inverse frequency) instead of doubling.
To create a nice wide stereo image the left and right channels timings are interleaved. Odd-numbered lines are assigned to the left channel; the even-numbered to the right.
When hit with a pulse they look like this:
The first-order echos are to the left of the cursor; the beginning of the second-order reflections to the right. The acoustic path difference of the left's first echo and the right is about 3-1/2 feet.
The 305 can take a mono input and provide a nice wide reverb field. In situations where maximum diffusion is needed mono in/mono out provides twice the diffusion because the left and right channels compliment each other.
Left and Right will always sound slightly different because when heard individually they're slightly different rooms or two different observation points in the same room.
While this may sound easy anyone who has had to cut the springs to make one of these can attest that it's not. It's a LOT of work.