Another Plate Reverb

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mrmiller
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Another Plate Reverb

Post by mrmiller » Wed Jan 17, 2007 8:18 pm

Hey all. I'm planning on building myself a plate reverb, and am looking for some input as per specs. I've read up a bunch on it, and learned more than I could possibly care to know about steel sheet in the process. Anyway, the dilemma I'm facing right now has to do with the sheet itself. As far as a driver, I'm using the Vidsonix Ghost as of now--$20 purchase, so I guess I wouldn't feel too horrible if it doesn't work out.

Anyway, the plate on the other hand is a little more expensive and a lot less flexible.

The spec I was originally aiming for was a 28 gauge (.016") x 48"x96" sheet of cold rolled steel, full hard temper if possible. This is approximately what was used in the original EMT 140, as well as others. The same specs (as I understand) was used for the Ecoplate, except it used stainless steel instead. The TapeOp article makes mention of the difference between stainless and regular: apparently some think stainless sounds more tinny, while others claim it's density leads to a smoother, more consistent sound.

This all factors into a decision that I need to make about the plate. I've spent days looking online for small quantity retailers and found approximately four. None have the specs above precisely. For most, the maximum gauge is 24 (.02"). Also, for those that do have 28, the maximum size is 36"x48", less than half the size of what I was planning to build. As well, most do not offer full hard temper. This is also true of the 30+ stores I called in the yellow pages.

The closest spec I have found is 28ga x 36" x 96" full hard temper in stainless. Now, I have reservations about this for three reasons:

(1) Does the 48" width versus 36" width make a big difference? And if so, would it be worth compensating with some extra length to get closer to the same total area? Instinct tells me the shape in this case is more important than the actual area, but I could very well be wrong.
(2) The price of stainless is 3-4x higher than that of plain, so there's a cost-benefit analysis here at work.
(3) I have the option with half-hard and quarter-hard tempers of going as thin as 30ga.

The closest in non-stainless I've come across is 26ga x 36" x 48", unknown temper (probably annealed/dead soft).

As far as sound, is the stainless comparably pleasant to the standard steel? Also, how much does thickness matter? Would the difference between 28 and 24 be disastrous and would the difference between 28 and 30 be miraculous? Lastly, the question of dimensions: is the overall shape what's important or is it primarly surface area?

Anyways, thanks for your time. I'm really looking forward to this project and hope some of you have some good input on steel plate!

- Mike

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Post by djimbe » Thu Jan 18, 2007 10:20 am

WARNING!!! rectal conversation follows....

O.K. I'm not talking too far out my ass as I have 2 EMT 140's and have worked as a mechanical engineer in the steel rolling business for almost 20 years. Still, I have some holes in my knowledge about some of your questions, so take my speculation as that.

First off, you likely won't ever find full hard material, even by the ton. Maybe if you wanna buy a 15-20 ton coil but that's it (15-20 tons is about usual for the coils of steel you see on the back of trucks going down the highway...). It's far too difficult to work with. Just getting a 4x8 blank flat requires some heavy machinery. Shearing it and welding it are also not easy for mortals to do. I did some banging on scrap lengths once upon a time, and didn't hear a dramatic difference between full hard and half hard. If you can get half hard, that's probably your candidate.

Similarly for thickness. I was banging on thicknesses from about 0.040" to about 0.018". A few thousandths didn't make a huge difference in sound. Using 0.020" instead of 0.016" probably wouldn't be too noticable a difference.

Size. Yeah the 140 is a big bastard. Other manufacturers made some smaller plates. If it was me, I'd try to keep the plate rectangular rather than square, so if 36" wide is what you can find, then maybe you scale back the length a little (like maybe from 8 feet down to 6) to keep the dimensions sorta relative to the EMT's.

Stainless. Not for me. You need a plasma torch to cut it clean, and my suspicion is that it would be much harder to tension up than carbon steel. Welding it isn't too hard if you have a gas shielded welder. I have no experience with sound difference between 300 and 400 series stainless, or how they might compare with carbon.

So that's what I got to say on sheet material. There are some other parts for a plate 'verb though, ones that will have a big impact on the sound. The sheet needs to be clean, meaning free of oxidation. One of mine isn't and I'm sure it's part of the sound of that unit. Amplifiers, both for the driver and the pickup(s) (at least in the EMT) also play a big part in the sound. My #1 plate has the model 162 stereo solid state amp. The #2 plate has two model V54 tube amps. Big difference in sound there, probably enough to overcome things like minor differences in plate size and/or thickness. Your frame/tensioning system will have some impact as well. An EMT 140 has a curb weight of about 425 lbs, much of which is the frame holding the plate. You'll want a big rigid frame so you can tension the plate without warping the whole shebang. One thing I can say for both of my plates is thay are FLAT. You want that, particularly if you envision a damper system since a plate damper NEVER actually touches the plate.

I guess that's about enough idle speculation. I'd say get the closest you can on the plate material and focus on a good support and your electronics, 'cause those aspects are just as important to the final sound. Good luck! I loves me some EMT. I'll never forget the first time I heard signal through my #1...like the voice of God...
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Post by mrmiller » Thu Jan 18, 2007 11:24 am

Wow! Thanks for your informed reply! It's really helpful and I'm that much closer to figuring out what I should do.

As far as electronics go, what I'm working with in terms of hardware is:
(1) Millenia Origin STT-1 Preamp/Compressor
(2) Digidesign/Focusrite Control24
(3) Digidesign 96io

Not the most impressive setup until you understand it was paid for entirely by an MIT a cappella group. We'll leave a cappella out of this discussion, as it tends towards arguments about whether it's music. Certainly not fine art. Anyways, I want to take the group to the next level and write a lot of original "vocal art" tunes with a tip of the hat to Bjork's Medulla, but not in that style necessarily. We also record CDs of covers. Seeing how my favorite band is the Beach Boys (over a day of Beach Boys music) and I love the 60s, I'm looking to the plate reverb as both a way to get a gorgeous vocal sound for an entirely vocal group as well as to emulate that 60s sound. Lastly, it's just a fun project!

Anyways, the Vidsonix ghost would be driven from the Digidesign outputs. The whole setup amps pretty cleanly, as I recall, and is solidstate. The preamp for the contact mics is a hot piece of equipment, and has a switch for toggling between solid state and vacuum tube amplification. Only problem is it's a single input preamp. Which, for stereo operation of the plate reverb leads to the last available amp source, the Control24 which has built in solid state mic preamps.

Now, back to the plate discussion:

I'm friends with a mechanical engineering major who works as a blacksmith here. That means I have access to a lot of metal working tools and he'd be able to help me through a lot of the hard stuff. Failing that, there's also professors who I'm sure could offer a little help if I asked as well.

The frame I'm imagining in my mind would be welded steel tubes (round or square? Is there a good reason to go one way?), mounted on wheels. As far as tensioning goes, the threaded "hook" setup they show in the TapeOp article looks reasonably satisfactory:

http://www.prosoundweb.com/recording/ta ... plate2.php

What did they use on the original EMT 140s?

As far as the actual plate goes--I'm not even sure I can find half hard sheets. That's what was fortunate about the stainless I found: it was specificed full hard, with the correct thickness. Also, you mention the oxidization issue: stainless should overcome that as well, neh? The flatness thing has a lot to do with temper as well, as I understand it. Annealed (which is what I'd be likely to get if I didn't know) is speced to be able to bend back on itself without cracking. Full hard on the other hand is only a right angle, as I understand it.

The closest I'd be able to get in non-stainless at this point is 24ga (.024") and unknown temper. 26ga (.02") would be great if I cound find it but I have been unable to except for a lone rusty piece sitting at one of 30 places I called. Right now, I'm heavily leaning towards the stainless despite the working difficulties because it's closest to the spec and also would be tredding new ground as far as online DIY plate reverbs are concerned.

Back to the size thing again--would larger be detrimental? It's a $20 price difference between 6' and 8', and as a percentage of the total price, that's not huge. Between 7' and 8' it's a $5 difference so there's no reason to go 7' unless 8' would actually hurt it. I mean, it seems like a "bargain" to go larger than 6', but might it hurt the sound rather than potentially add to it?

I'm gonna keep looking into finding 26ga plain steel but my hopes aren't high. Nobody around MA seems to carry anything that thin, unfortunately.

You mention a plasma cutter, but hopefully I won't need to cut the steel as I'm getting it precut to the right size. As far as welding goes, I'm relyng on this friend to help me through it. The only welding on the plate that I see would be corner supports.

Anyways, thanks so much for your informed time so far. I'm getting closer, thanks to you!

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Post by Bill @ Irie Lab » Fri Jan 19, 2007 9:19 am

Whoa, hossie!

That Digi doesn't have anywhere near the oooomph (read: ability to deliver current) to power the exciter.

To drive the plate adequently the line-level out must be boosted by either a quality high-current capable headphone amp (few are available) or a small high-quality power amp.

Doo-doo in -> doo-doo out.

Give your electronics a little more thought before totally focussing on construction details.

Good luck.

Writing from another school on the Charles,

Bill
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Post by djimbe » Fri Jan 19, 2007 11:53 am

I have no experience with the exciter you've chosen or the capabilities of some of your gear, Mike. I'd bow to Bill's experience there.

I can confirm that the original EMT amps take a line level signal and boost it appropriately for the EMT driver and pickups. There's a well defined calibration procedure for the EMT amps, as regards input and output levels. They don't like to be fed wrong. The marriage of amp, driver, and pickup is very important in one of these things, and the thought them crazy Germans put into these components working together as a system is one of the reasons 40+ year old plates still work and sound so great. And just to finish the thought, the build quality of the EMT amps is beautiful. Like Studer decks, they were made to be serviced and they're a pleasure to work on...

Plate tensioners: the EMT ones are only slightly different from the ones shown in the TO article. If'n I was building a plate, I'd probably settle on a design like the article, since it's a bit easier to impliment than what EMT chose.

I'd build me a frame out of square tube rather than round, but that's just 'cause square tube would be easier for a hack like me to weld and keep nice right angles. The EMT's use round tube for the frame, and angle iron for the driver and pickup mounts.
And I just looked inside #2 and noticed another detail to be aware of. The driver is not located in the center of the long dimension on the plate, though it is on the center of the short dimension. Similarly, the two pickups (since I have stereo units) are also not equidistant from the driver (this I knew, but I did want to mention it).

O.K. More for you to think about. This is a big project, and it's just one reason why I opted for the real deal, rather than home brew....
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Post by mrmiller » Fri Jan 19, 2007 12:55 pm

I haven't focused on electronics as much yet because while they're slightly replacable, the plate itself definitely is not: once I've got it and put it together, there's no way I'm changing the plate for anything else.

I'm taking a look at electronics now, and wondering what exactly I should be looking for in a power amplifier: what should I need for specs and price point? Also, am I correct that the preamp will be satisfactory for the pickup? It would unfortunately only be mono, unless I wanted to settle for the not-so-great Control24 preamps.

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Post by djimbe » Fri Jan 19, 2007 8:39 pm

Can't help much with electronics advice for your driver. Maybe I'll hunt that thing up and an idea will come to me...

If your pickup is just a contact mic of some sort, then yeah, your preamp should work work just fine. Make sure it works that way on a guitar, and it should work on your plate. The pickups on an EMT are very special accelerometers (hmm...senior moment here with the spelling of that word...). Your Mechanical Engineer buddy should be able to help you understand what those are about if you don't know. We use 'em in the mill for vibration analysis all the time. For your rig, a contact mic is better, trust me...
I thought this club was for musicians. Who let the drummer in here??

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Post by mrmiller » Sat Jan 27, 2007 5:26 pm

Well, things are starting into motion at last--I'm getting all the steel on Tuesday and will hopefully get it all welded at the MIT Machine Shop soon thereafter. Then the tensioning, and sometime in there making the contact mics. I'll have more to update after all that, I guess.

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Basic Sound Clips

Post by mrmiller » Sun Mar 04, 2007 5:50 pm

Put everything together. Haven't really tightened any bolts accurately or anything, and my contact mic has a lot of noise, and I don't have a power amp. But other than that, I think it sounds pretty good. The trail's also rather long, so I should probably figure out some way to cut the reverb time. Anyways, just one sample for now. Eventually I'll have pictures and more isolated samples, but here's a few sung parts.

The only effect on the tracks is the plate reverb:
http://web.mit.edu/mrmiller/Public/boy2.mp3

With some convolution reverb thrown in, and more voices present:
http://web.mit.edu/mrmiller/Public/boy.mp3

Suggestions? Feedback?

Thanks.
- Mike

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Post by syrupcore » Sun Mar 04, 2007 10:00 pm

that sounds sweet. Can you post the first one without any reverb without having to do a bunch of work?

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Post by mrmiller » Sun Mar 04, 2007 11:29 pm

Not tonight, but I'll be in the studio tomorrow so I'll grab the tracks then hopefully. I'm swamped with schoolwork currently, but I'll try to have it up tomorrow night for comparison.

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nice!

Post by nopenopenope » Mon Mar 05, 2007 7:50 am

doesn't have a very classic sound yet, but it does sound really promising. instantly worlds better than any plugin plate. congrats on such a huge project! good luck with the rest!

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Post by runrunrun » Sun Apr 29, 2007 9:20 pm

did you get a chance to do anymore samples with this?

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Post by mrmiller » Sun Apr 29, 2007 9:24 pm

Yes and no. I decided that the contact mic I was using was to blame for shoddy sound quality, so I'm waiting on one not made by me to come in the mail. It's unfortunately been a rather busy semester at school for me and I haven't had much time to fiddle around in the studio. But I'm itching to play around with it once I have the actual equipment working right. I'll probably have something to add around late May when I'm done with finals and can just spend all my time playing in the studio.

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Post by tony_tomlinson » Sun May 20, 2007 9:04 pm

I also recently built a plate. I used a Vidsonix Ghost as a driver and that works great if you have an amp to power it but am having a tough time with the pickup being too noisy. I made a contact mic out of a doorbell buzzer. That worked but it was noisy. I tried a piezo and that was just a noisy.

What contact pickup did you use?


Tony

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