Spring Reverb Preemphasis

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555x555
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Spring Reverb Preemphasis

Post by 555x555 »

Hi all! Someone from mod wiggler directed me here. [1]

I'm thinking about trying preemphasis/deemphasis with spring reverb. Seems like the way the spring reacts is highly frequency dependent, and you might be able to get more usable out of it by boosting high frequencies going in, cutting them going out. One might even use the RIAA curve and then reuse cutter/phono preamp designs for the drive and recovery. I kind of imagine something has been tried before, and I'm curious to hear about that.

Many thanks, and regardless, happy to have found this forum!

[1] https://www.modwiggler.com/forum/viewto ... 2b370585b5
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JR.
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Re: Spring Reverb Preemphasis

Post by JR. »

Springs have odd overload characteristics, I'm not sure how much pre-emphasis they would tolerate.

Companding NR has difficulty with the spring reverb tail altering the expansion decode accuracy.

JR
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mediatechnology
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Re: Spring Reverb Preemphasis

Post by mediatechnology »

Thanks for joining us 555x555.

You might want to read through this thread: viewtopic.php?t=213

Preemphasis with spring reverbs is often used to emulate constant-current drive to maintain an equal driving current vs. frequency into the highly-inductive load of the driving transducer. We used it in the AudioScape XL-305 re-issue.

You mentioned in the modwiggler post you were interested in preemphasis to reduce "boing." I doubt that will help and encourage you to read the above thread.

Additional preemphasis could be used in an attempt to extend frequency response but I've found that with the Accutronics/Bell/Hammond/Mod type springs that they stop reveberating/delaying above 8 kHz or so.
Above 8 kHz an undelayed cross-talk-like effect occurs due to a change in (I think) the spring transmission mode.

In both the the original MicMix and AudioScape rolloff is introduced to reduce the "leakage." (Leakage is used for lack of a better word.)
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JR.
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Re: Spring Reverb Preemphasis

Post by JR. »

yup... the "boing" is the odd overload artifact I was referring to.

JR
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555x555
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Re: Spring Reverb Preemphasis

Post by 555x555 »

Ahhh, so the boing is not a problem of the spring being a bad delay line, just the opposite---it's still too "good" of a delay line, given that there are only 2-3 of them. That makes so much more sense. It's not that spring reverb goes boing because springs go boing, it's that springs go boing because they are comb filters. So the solution is more springs, better spacing of delay times, and/or more complex feedback between different springs.
Additional preemphasis could be used in an attempt to extend frequency response but I've found that with the Accutronics/Bell/Hammond/Mod type springs that they stop reveberating/delaying above 8 kHz or so.
Above 8 kHz an undelayed cross-talk-like effect occurs due to a change in (I think) the spring transmission mode.
Interesting. Does the delayed signal just vanish, or is this an additional transmission mode that drowns out those frequencies and makes them unuseful? Does the transition frequency depend on the delay of the spring, L,M,S?
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mediatechnology
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Re: Spring Reverb Preemphasis

Post by mediatechnology »

555x555 wrote: Thu Feb 08, 2024 4:39 pm Ahhh, so the boing is not a problem of the spring being a bad delay line, just the opposite---it's still too "good" of a delay line, given that there are only 2-3 of them. That makes so much more sense. It's not that spring reverb goes boing because springs go boing, it's that springs go boing because they are comb filters. So the solution is more springs, better spacing of delay times, and/or more complex feedback between different springs.
Exactly. You're hearing the comb filters.
555x555 wrote: Thu Feb 08, 2024 4:39 pm
Additional preemphasis could be used in an attempt to extend frequency response but I've found that with the Accutronics/Bell/Hammond/Mod type springs that they stop reveberating/delaying above 8 kHz or so.
Above 8 kHz an undelayed cross-talk-like effect occurs due to a change in (I think) the spring transmission mode.
Interesting. Does the delayed signal just vanish, or is this an additional transmission mode that drowns out those frequencies and makes them unuseful? Does the transition frequency depend on the delay of the spring, L,M,S?
The delayed doesn't vanish - the added signal sounds like direct signal HF crosstalk or leakage. It doesn't seem to make much difference if the delay is long or short.
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