DIY Plate Reverb. Questions, questions, questions.

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A.David.MacKinnon
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DIY Plate Reverb. Questions, questions, questions.

Post by A.David.MacKinnon » Sun May 09, 2010 6:26 pm

I started building a plate reverb over the week-end. It's 2' x 4', 26 gauge steel plate. So far I've built the frame, hung and tensioned the plate. Now I'm researching drivers and pick-ups and wondering about damping systems.

Here's where it's at so far -

Image

Wondering if anyone here has built their own plate and if you'd be willing to chime in with your experiences and opinions. I'm leaning towards a Ghost transducer for the driver and piezio pick-ups using the pre-amp design from JCC & Associates (platereverb.com).

Have any of you guys built a plate this size? What did you do for damping? Is is as big a deal with a plate this size?

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Post by antoniosolo » Sun May 09, 2010 6:53 pm

Dan Alexander Audio has a great deal of info on plate reverbs. He handles those quite often....google him.
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Post by Jitters » Sun May 09, 2010 11:24 pm

Man, that looks SWEET! :o

I'd love to put something like that in my attic...

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Post by A.David.MacKinnon » Mon May 10, 2010 5:30 am

Jitters wrote:Man, that looks SWEET! :o

I'd love to put something like that in my attic...
Do it. It's been pretty easy so far. All the parts came from Lowes. I'm guessing it'll have cost me about $350 once the driver, pick-ups and box are in place.

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Post by E-money » Mon May 10, 2010 6:38 am

Do it. It's been pretty easy so far. All the parts came from Lowes.
Did you get the steel for the plate from Lowes?
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Post by A.David.MacKinnon » Mon May 10, 2010 6:47 am

E-money wrote:
Do it. It's been pretty easy so far. All the parts came from Lowes.
Did you get the steel for the plate from Lowes?
Yep.

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Post by A.David.MacKinnon » Mon May 10, 2010 8:02 am

I've been reading through a bunch of old DIY plate threads but I'm still not sure about the best method for mounting the driver.
Has anyone here built a plate using the Ghost transducer as a driver? If so, did you mount the driver right to the plate? Is it attached to the frame at all or just the plate? If it's not attached to the frame does the weight of the driver effect the tuning and tension of the plate?

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Post by A.David.MacKinnon » Mon May 10, 2010 12:52 pm

Day 2 -
I built and fitted the damper today. It's made out of a stiff fiberglass panel mounted on a metal frame. I'll have to adjust it by hand when I want to change the decay time but due to the smaller size of the plate I'm guessing this is going to be a set it and forget it kind of thing.

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Post by The Scum » Mon May 10, 2010 3:51 pm

Wondering if anyone here has built their own plate and if you'd be willing to chime in with your experiences and opinions.
I think you're using the same plate material I used...from the one lonely bin of welding supplies at Lowe's.

I've got a contact for some stainless that I need to be getting in touch with.

Since you're at the start: go back and replace the screws that hold the brackets on the plate with stainless. I had problems with plain steel ones getting sheared off. Are your eyebolts welded closed?

The real crux: the thing will sound best when it's tensioned absurdly tight. One of the classic descriptions is that you tension it until you break something, then back it off a hair. I've destroyed the threads on a number of #20 bolts & nuts, and opened up a number of eyebolts and s-hooks.

The frame has to be pretty rigid, too.
I'm leaning towards a Ghost transducer for the driver and piezio pick-ups using the pre-amp design from JCC & Associates (platereverb.com).
The Ghost is fine for the money.

Piezo discs will work, but sound awful - very chalky. PVDF tabs sound better, but they're a little odd to work with. A small loudspeaker with a spike that contacts the plate can work.

I've mounted pickups using neodymium magnets and/or blue painters tape.
Has anyone here built a plate using the Ghost transducer as a driver? If so, did you mount the driver right to the plate? Is it attached to the frame at all or just the plate?
I have a spike that threads into the driver where the foot used to mount...I think it's a #8 thread. The ghost sits on a little arm that's mounted on the frame, decoupled with some foam. The spike means it acts like a true point source.

I was finding that anything flat mounted to the plate tends to buzz & rattle.
I'm guessing this is going to be a set it and forget it kind of thing.
If yours comes out anything like mine, you'll want a lot of hands on damping control. The last few fractions of an inch before the damper hits the plate are were some really nice sounds live...seriously, most of the action is between 1/8" and 1/2".

I built my damper with a manual arrangement, but have been reconsidering. I'm starting to think something with a stepper motor and remote control would be useful.

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Post by A.David.MacKinnon » Mon May 10, 2010 4:20 pm

The Scum wrote:
Wondering if anyone here has built their own plate and if you'd be willing to chime in with your experiences and opinions.
I think you're using the same plate material I used...from the one lonely bin of welding supplies at Lowe's.

I've got a contact for some stainless that I need to be getting in touch with.

Since you're at the start: go back and replace the screws that hold the brackets on the plate with stainless. I had problems with plain steel ones getting sheared off. Are your eyebolts welded closed?

The real crux: the thing will sound best when it's tensioned absurdly tight. One of the classic descriptions is that you tension it until you break something, then back it off a hair. I've destroyed the threads on a number of #20 bolts & nuts, and opened up a number of eyebolts and s-hooks.

The frame has to be pretty rigid, too.
I'm leaning towards a Ghost transducer for the driver and piezio pick-ups using the pre-amp design from JCC & Associates (platereverb.com).
The Ghost is fine for the money.

Piezo discs will work, but sound awful - very chalky. PVDF tabs sound better, but they're a little odd to work with. A small loudspeaker with a spike that contacts the plate can work.

I've mounted pickups using neodymium magnets and/or blue painters tape.
Has anyone here built a plate using the Ghost transducer as a driver? If so, did you mount the driver right to the plate? Is it attached to the frame at all or just the plate?
I have a spike that threads into the driver where the foot used to mount...I think it's a #8 thread. The ghost sits on a little arm that's mounted on the frame, decoupled with some foam. The spike means it acts like a true point source.

I was finding that anything flat mounted to the plate tends to buzz & rattle.
I'm guessing this is going to be a set it and forget it kind of thing.
If yours comes out anything like mine, you'll want a lot of hands on damping control. The last few fractions of an inch before the damper hits the plate are were some really nice sounds live...seriously, most of the action is between 1/8" and 1/2".

I built my damper with a manual arrangement, but have been reconsidering. I'm starting to think something with a stepper motor and remote control would be useful.
Thanks for all of this. It's a big, big help.
I built my damper today and then half an hour later while walking the dogs I thought of a way to make it more easily adjustable. I'll probably use it for a little while before I change anything though.

Are you using a dedicated pre amp system for your PVDF tabs or just DI'ing into the console? What are you using to drive the ghost?

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Post by A.David.MacKinnon » Mon May 10, 2010 5:29 pm

The Scum wrote:
I have a spike that threads into the driver where the foot used to mount...I think it's a #8 thread. The ghost sits on a little arm that's mounted on the frame, decoupled with some foam. The spike means it acts like a true point source.
One more question. Does the spike just sit against the plate or is it bolted to the plate? My rough understanding is that the driver needs to be able to push and pull the plate. Is that right?

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Post by The Scum » Tue May 11, 2010 10:59 am

Are you using a dedicated pre amp system for your PVDF tabs or just DI'ing into the console?
I've been using instrument inputs on various preamps...2.2Meg input on a Hamptone HJFP works well.

I've been considering some sort of preamp built into the system...maybe the Shoeps 3-transistor mic head amp, so it can be phantom powered, and lead to a mic pre input. Or a variant of the Don Tillman preamp...
What are you using to drive the ghost?
30 Watt paging amp at the moment...was dirt cheap and has tone controls for preemphasis. I also used headphone amps, and a little guitar amp.
Does the spike just sit against the plate or is it bolted to the plate? My rough understanding is that the driver needs to be able to push and pull the plate. Is that right?

The spike just presses into the plate. There's a little tension from the foam on the arm that holds it in place. This means I'm not drilling holes in the plate, and can move the driver around.

I was thinking that placement would be critical, so I left it open. And then learned it's not as critical as I was thinking. Leaving some asymmetry in driver and pickup placement seems to help the stereo spread.

Tension and damping have been the real eye openers for me. And learning how to test, characterize & quantify my results in any sort of meaningful way...

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Post by Jitters » Wed May 12, 2010 8:41 am

junkshop wrote:
Jitters wrote:Man, that looks SWEET! :o

I'd love to put something like that in my attic...
Do it. It's been pretty easy so far. All the parts came from Lowes. I'm guessing it'll have cost me about $350 once the driver, pick-ups and box are in place.
It does look pretty doable... I really like that the frame is bolted together. I had always thought there would have to be some welding involved.

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Post by A.David.MacKinnon » Wed May 12, 2010 9:44 am

It remains to be seen if bolting the frame together is good or bad. It's way easier than welding but I'm not sure how tight I'll be able to tension the plate before things get dicey. So far so good but I've got my fingers crossed.

I built some piezo pickups yesterday and ran some tests using an auratone speaker as the driver. I moved the speaker in as close as I could without touching the plate and then cranked up the volume. It's not bad. There isn't a ton of high end but what's there sounds pretty decent with a little pre and post eq. The issue might be the driver (I have a ghost on the way) and I'm sure some of it is tension related.

I just picked up some supplies to build a few moving coil pick ups. We'll see if they're any better (or worse).

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Post by The Scum » Wed May 12, 2010 4:54 pm

The high end gets better as you add tension...there comes a point that it starts to choke, but that's up in stripped screws & broken nuts territory.

My frame is welded heavy duty unistrut. I've proven that it's solid enough to rip the plate apart.

I'd be concerned that yours might bend or skew as the tension goes up. Might be safety goggles time.

It's also a good exercise to feed it a pulse train, and listen on headphones while tensioning, so you can hear the influence tension has.

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