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DIY Stompboxes => Digital & DSP => Topic started by: Digital Larry on July 11, 2016, 11:35:53 AM

Title: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 11, 2016, 11:35:53 AM
I put this topic in the DSP forum because the end goal is to work on different approaches for DSP emulation of springs.  I also think I would like to build a standalone reverb unit with different types of springs to get different spring sounds.  So, I'm talking about REAL spring reverbs.  Not a Belton brick or any DSP emulation.

I see in the Accutronics catalog that their most expensive spring assemblies have 3 double springs (joined in the middle) while the cheapest one is just a single spring.  I'm thinking the single spring type is what I'm looking for, to maximize the "pwip" such as heard on Dick Dale's "Tribal Thunder" CD - which is the only one of his I have.

The spring in my Tech 21 trademark 60 is not very sproingy in this regard.   I haven't looked inside it, but I think that using multiple springs (no doubt of different wire gauge and/or tension) along with joining 2 springs in the middle is an attempt to minimize that "pwip".  But I want to maximize it!  At least sometimes.

DL
Title: Re: Which spring reverb is the "sproingiest"?
Post by: stallik on July 11, 2016, 02:13:33 PM
My interpretation of the word "sproinginess" must be questioned but if it's what I think you may be referring to, I'd put in a good word for the reverb circuit built into my old Roost combo ( 70's Hi Watt style amp)

Valve driven and using an accutronics box, for years it was the best reverb I had. I still have it but now much prefer to use my Chasm.

Circuit diagrams are here
http://www.andy-duke.co.uk/roost/roostschematics.html (http://www.andy-duke.co.uk/roost/roostschematics.html)
Mines a Session Master 50
And I'm not sure what pwip means either :)
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 11, 2016, 03:40:19 PM
The "sproing" I am talking about is most evident when you play muted strings.  There will be a little "pwip" kinda of sound right on the attack, whose tone does not depend on the note you are playing.  It is a resonance characteristic of the spring itself.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: stallik on July 11, 2016, 04:17:48 PM
Thanks for the explanation. I think I've heard that sound in bucket loads but not on my amp reverb so please ignore my last recommendation.
I was gifted a reverb tank and separate controller which was intended for AV work. It sounded terrible(sorry). That brash attack on notes similar to the initial attack when you kick the tank. After storing it for some years, I discarded it but do recall while salvaging components that the tank contained 3x single springs arranged in a z shape. This thing appeared to be build down to a price but, try as I might, I cannot recall the make... Sorry



Title: Re: Which spring reverb is the "sproingiest"?
Post by: cloudscapes on July 11, 2016, 05:06:19 PM
isn't the pwip just the sound of the physical spring self-resonating? at a fixed pitch?
Title: Re: Which spring reverb is the "sproingiest"?
Post by: FiveseveN on July 11, 2016, 06:00:01 PM
That would be my guess as well, and a wide-bandwidth short excitation like a muted string would make it more obvious.
Maybe on the DSP side you can control decay time (spring length), "richness" (number of springs) and resonance independently.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 11, 2016, 08:00:50 PM
isn't the pwip just the sound of the physical spring self-resonating? at a fixed pitch?
Not really.  It is the process of "dispersion" by which the delay of certain frequencies is much higher than nearby frequencies.  This paper describes it quite well. I have listened to some of the examples and they do not really sound like any spring reverbs which I have in my possession.

Assume you have an impulse or "click".  This contains "all" frequencies.  Send it into a dispersive medium and some frequencies take noticeably longer to travel through.  That is what causes the pwip.  I have been doing some DSP experiments with long chains of all pass filters and am starting to see what is going on, although it's fairly complicated to get a realistic emulation of the spring.

http://dafx09.como.polimi.it/proceedings/papers/paper_84.pdf

This guy seems to have devoted much of his professional life to the topic.  Now why don't I know anybody like that?
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Ice-9 on July 12, 2016, 01:39:01 PM
Thanks for posting the paper on Spring reverbs Larry, I will print that out and give it a read sometime.

I kno you are looking for information on real springs rather than DSP but have you seen Don Staverly's post over at Spin, he has coded up an example of a spring reverb for DSP. I haven't had time to try it myself but it looks interesting.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 12, 2016, 04:01:39 PM
Yes I've seen it and tried it.  What I haven't done is measured its spectrum or compared it to a real spring.  The only real spring reverb I have doesn't have the sound I'm looking for.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Ice-9 on July 12, 2016, 04:10:12 PM
At the moment the only spring reverb I have is an Accutronics which is in a Marshall Valvestate amp, I'm not sure what model tank it is but from memory it is about 18" long with two springs. If there is anything I can do for you to test this let me know.


Title: Re: Which spring reverb is the "sproingiest"?
Post by: samhay on July 13, 2016, 05:23:07 AM
>This guy seems to have devoted much of his professional life to the topic.  Now why don't I know anybody like that?

Because you don't hang out at a university?

Are you looking for a (relatively) simple analytical way of describing the reverb/pwip, or you thinking more along the impulse response/convolution approach?

Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 13, 2016, 06:25:40 AM
Well since I'm up to my neck in FV-1 I'd like to leverage the capabilities of that thing to try to accomplish some of these goals.  So, for example, while it does have a 2-instruction all-pass, and if you set them all to be the exact same length, you can "tune" where the pwip occurs, even if I devote the entire 128 instructions to this, minus necessary I/O, it still does not get into the zone I am looking for.  Mind you I am looking for Pwipzilla here.  So to answer your question more directly, yes I'm looking for an analytical way to describe it and there is another paper by Julian Parker that goes a long way towards that.  It' just that even his samples, while showing some evidence of pwipiness, is still more subtle than I would like.

I do recall a Johnson J-Station amp modeler which I had years ago, and actually liked patch 22 on it pretty well (you know the one).  It had a spring emulation which sounded an awful lot like a sampled pwip that was level triggered. This is NOT what I'm after! 

I've started doing some spectral measurements of recordings as well as my own reverb algorithms, and if I didn't actually have to do something else in order to pay the bills, I'd probably be a bit further down the line on the whole process.   ::)

Here's another paper that is focusing in on what I'm after.

http://dafx09.como.polimi.it/proceedings/papers/paper_36.pdf
Title: Re: Which spring reverb is the "sproingiest"?
Post by: MetalGuy on July 13, 2016, 04:02:34 PM
I don't know exactly what "pwip" you're talking about but sometimes when you hit the reverb with higher amplitude signal it will produce something similar which is usually to be avoided.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: samhay on July 13, 2016, 05:36:01 PM
>Here's another paper that is focusing in on what I'm after.

That looks like it becomes a (relatively) expensive calculation if one wants to maximise pwip with a lot of cascaded filters.

Have you seem this approach?
http://architexte.ircam.fr/textes/Cont13d/index.pdf

It also looks expensive (depending on the number of bins), but at least is potentially something different to try.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 13, 2016, 07:03:08 PM
Interesting.  Thanks for sharing it.  I have to read these things about 15 times to really absorb them.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 16, 2016, 10:11:24 AM
Here's a nice practical guide for spring reverbs.  Wow, there are so many variations!

https://www.tubesandmore.com/tech_corner/spring_reverb_tanks_explained_and_compared
Title: Re: Which spring reverb is the "sproingiest"?
Post by: PRR on July 17, 2016, 11:31:19 PM
> such as heard on Dick Dale's

In Mr Dale's early years, the only tanks were 2-spring medium and long.

3-spring seems to arise among hi-fi and studio markets for a less-fake sound.

Short tanks come as "Reverb!" came down-market to smaller amps (far too small for Dale).

Cheap 1-spring tanks are an insult to the ear.

Yes, it is possible Dale went into his springs with damping or spring-cutters to change the sound. His recordings are too complex for my old ears to analyze.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 18, 2016, 04:17:56 AM
Cheap 1-spring tanks are an insult to the ear.
Maybe, if what one was expecting was in fact some semblance of "artificial reverberation".  However, such a thing might find application as a special effect, or a mixing enhancement for specific percussion tracks.  Ever heard "Present Arms in Dub" by UB40?

As a side note, within the past few years I have become entranced with the music of the Mermen, a Northern California surf/psychedelic band.  Their guitarist Jim Thomas uses an elaborate rig with Strymon Big Sky for reverb and nary a trace of sproing.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: PRR on July 19, 2016, 12:20:23 AM
Found while back-forth tracing Hammond's patents:

http://www.google.com/patents/US8391504

Description of a digital spring emulation. Respected audio company. Too deep for me.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 19, 2016, 10:07:35 AM
Thanks Paul!  Being written as a patent, it is a little... errr... dense I'd say.  My goal is not necessarily to develop the most realistic spring reverb emulation.  It is more to try to discover unique aspects of spring reverb emulation algorithms and determine whether interesting resuts can be had by isolating and enhancing those.

DL
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Mark Hammer on July 19, 2016, 10:18:22 AM
I'm going to go out on a limb here, and suggest that the most "spring" will be obtained when the spring is long and there are fewer of them.  I base this on the assumption that:
That said, one of the aspects of the traditional Fender Reverb that made it desirable was the Dwell function, that determined how hard the springs were driven.  It's that initial big transient, telling the springs to "WAKE THE F*** UP!!!", from a deep sleep (resting position), that yields maximum sproing.  And if they are long springs, even moreso.
Title: Re: Which spring reverb is the "sproingiest"?
Post by: Digital Larry on July 19, 2016, 12:23:16 PM
For sure, multiple springs and/or springs joined in the middle help spread out the resonances.  As far as long/short I still haven't decided and as much as I've put forth a bunch of mathematical treatises on the subject I don't normally go into them much other than to think - factor in the numerator, so end result increases if it does - whether linearly or square rootedly or otherwise I don't care.

Your comment about the drive level is well taken.  Some of the papers I've read start with an assumption that the torsional displacement is very small, which aids in a linear analysis of the system, but what if it isn't?  What if you drive a garage door spring with a washing machine motor?  That's my idea of a manly reverb.   8)
Title: Re: Which spring reverb is the "sproingiest"?
Post by: ElectricDruid on July 19, 2016, 01:13:10 PM
You might have a look at old home organs too. The sproingiest spring I've ever come across was in a Yamaha BR-30 (I think that was the model) organ from the 1970s. I modded it to include an effects send/return, since the organ had an internal amp and a choice of 1x12" speaker or a single horn rotary speaker. With a soft drive pedal plugged into the effects loop and the reverb turned up, you could make the nicest chugging reggae organ stab sound I've ever heard. A large part of that sound is the spring's reaction as a overdriven stab hits it and makes it resonate. It had a long reverb tank, but I don't think I took it off so I don't know how many springs it had.

Tom