Spring Reverb Design - A Masteroom Clone with Springs or DSP

[quote author="mediatechnology"]Erik - Pretty cool site. Has anyone thought about using a piano with the damper locked open? Think about it....Sing into one.

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I had not thought of it, but now I will try it. I am gona rigg up a speaker so I can play it into it. This of an out of tune piano and some odd overtones you could get that way too.
Anyway, back to creating a reverb...

For info and I am not sure whether this is the right place - but I just finished reading an old Tape Op and it mentioned a bespoke dual spring reverb design that somebody built for Andy Hong (I think) for use in M/S
The reverb tanks where I think put opposite each other to try and cancel out mechanical noise - if you want I can try and find the article

Just to go off tangent a little. One of the most appealing aspects about spring lines is the fact that their 'side-effects' are actually quite desirable.
If you've ever listened to any reggae records or classic dubs then you will have heard that classic 'doing' sound when the snare hits. Similarly with Fender giutar amps, that great twang you get from the spring line can't be mimicked very easily.
Now a lot of the units you have been talking about here go to great lengths to get rid of those the side-effects - using limiters etc and I think it somewhat misses the point.
The great spring reverb used on reggae records was the Fisher Spacexpander which was a valve driven unit with a transformer link to the reverb tank - you see them up for sale on eBay occasionally. They sound great.
I got myself a Tapco unit off eBay. It has two independant spring lines with equalisers after each one. The first thing to do on this unit is to disable the limiters - after which it becomes a very usable effect.
Also worthy of note in the category of 'spring reverbs' are the units that AKG produced in the 70's. Their springs were much larger than the Accutronics types you've been talking about here. In general they sounded very good - particularly the BX20.

The Fisher one was Accutronics (or whatever it was called before Accutronics). It had Spacexpander stamped on it but was a two spring unit similar to the type still available.
I've experimented with the Tapco unit and found that the FET limiters kill the twang as well as the sparkle.
I also experimented with various drive circuits using an Accutronics tank and couldn't duplicate the Fisher sound. I think there is definitely something to the valve amp/transformer coupling to the sound.
The Tapco drive design is pretty good. The worse one was that which is often suggested by a well known author using an op-amp drive.
But yes, there is life left those springs !

Yep, that unit on eBay is the one. It looks in pretty good condition too.

I don't want to start mentioning names (I've got into trouble like that before !) but the design I tried used a LM386. It was pretty lifeless.

I think it's fairly clear that a good deal of equalisation is necessary to get these springs to sound good. I notice in the Tapco circuit that there is a lot of tweaking before and after the tank.

Yes, the BX20 was like a big box. However for smaller studios that couldn't afford an EMT plate or didn't have the space, it was pretty good.
I never knew how they changed the decay time - usually it was just left on one setting.
The Orban got a lot of stick because people compared it to the larger units, but I suppose for a little rack-mount unit they got the best out of it that they could. However, I never saw anyone go out of their way to use it !
I heard a simulation of a spring reverb on a software plugin a while back that was very amusing. They had tried to copy the flutter and twang of guitar amp type unit. It sounded very odd.
Like I say, maybe there is still some mileage in these dangly springy thingies...