I came across this article the other day: http://www.prosoundweb.com/article/print/how_to_build_your_own_plate_rever b

I haven't got space for a 2.5m long unit like the real thing, so I've started trying to build a little one 1 by 0.5 meters. I've managed get it working and sounding like a reverb.

The plate made a fairly cool sound recorded with the piezo when I hung it in front of my drumkit, it was low end heavy, with nothing above 15kHz. I've driven it with the cannibalised speaker which sounded much better, but the weight of the plate has deformed the cardboard the voice coil is wrapped around, so I'm devising a more rigid driver, and a guy I know has offered to knock up a steel frame for nothing (working in heavy industry has its perks), so I can get some tension involved.

Has anyone had experience with a real EMT 140? I guess they must have had a pretty damn good reason for making them so big, but is there any reason a smaller one can't sound nice?

I've canibalised an old speaker, and used a piezo from maplins for £1.50 or something like that and the steel for the frame isn't costing me anything. I should have looked around for a cheaper/freer 'plate' but I was impatient so I just went in B&Q and paid £20. Still a fairly cheap experiment!

Sounds excellent! Show us some pics and let us hear a few snippets

I never thought about making one myself but reading the article you refer to made my fingers itch... unfortunately I don't have that much time...

Nevertheless, I hope you keep us up to date with your plate-adventures (pictures?)

The size of the original EMT plate was defined by the speed of sound through the steel and the required reverb time.
You can get an idea of what your plate is going to sound like by tapping it with a fingernail and listening. Tension was the key to success, the old adage was to tighten the springs to half a turn before they broke!
The EMT plates at Lansdown studios were famous for their superb sound, and it turned out that it was because they had rusted after a flood.
I've tweaked a few EMT 140 plates in the past, and found great audible success by de-greasing them with alcohol, as they are coated in a film of wax to prevent rust which tends to dull the sound. Combined with careful tension increase they really zing!
If you place two piezo pickups on the plate and experiment with different locations you should get a good stereo reverb.

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Technical Engineer

Ahhh, you can't beat a real plate reverb! I've had experience of quite a number of the EMT originals and they all sound different. Those differences seem to exasperate with age as well. Some are dark, some are bright, but all just seem to have a certain magic about them.

The secret with a DIY plate always seems to be a good sounding sheet of steel to start with (as thin as possible) and then getting it as tight as possible in the frame. Make sure your speaker is slightly off centre and experiment with twin piezos in different positions to obtain the best stereo effect.

EMT did make a smaller plate designed for outside broadcast work, I can't remember the model number, but used one a few months ago and it sounded great.

I've built a couple of small units in my time but am just about to start building a huge one using an old steel bed as the frame - I'll document it, take lots of pics and start a thread when I've sourced a big enough sheet of steel!