The Ribshack

"Honey, you need to go to the other end of the trailer, I'm fixin to shoot up the kitchen."
.................................................................................................... overheard at my bar last night

Ok, real naked plate reverb.

I started looking at this over a year ago and decided to forgo watching Craigslist for a couple of years waiting for a used one to come up for sale and spending 2-3000 bucks to get one of my own and then another year to figure out why it didn't work.

I stumbled across a fairly detailed drawing of the original and discovered that aside from the electronics it was a pretty simple concept;
a big ole chunk of sheetmetal with a driver and 2 pickups. Well, shit I says, I can do that out of Home Depot!

Almost. I had to go to a metal shop to get the plate. And Banjo Center for the pickups. Oh well.

Before I go further, I have to point out that I did all this with a minor impediment. I was dog sitting for Rosie and had an ankle biting loud mouth terrorist helping along the way.

Terrorist

So I began by gathering all the materials. I decided to use 1 5/8" Unistrut for the frame. This is a building system I worked with in a former lifetime and I know it to be quite sturdy, long lasting and completely customizable. The corners of the plate needed to be reinforced so I chose Simpson flat 90's to sandwich each corner. Steel baby.

frame hardwarestrut and sheet

I'll spare you the details of using a Sawzall to cut the frame down to size allowing a 2" gap all around the 4x8 plate. Do yer own damn math. You can see in the pic the tools needed for the task. Also note that I used red Loctite on all the bolts.

strut assembly

frame assembled

I used the vise grips to hold the corner pieces together while I sunk 2 Tek screws, drilled through the plate and pulled 8 pop rivets through. I pulled the Teks out and riveted those holes last, then I drilled out the 2 holes for the eyebolts.

corner 1

corner 2

I laid it all out on the ground and attached the plate into the frame, snugged it up enough that it didn't get all wobbly when I stood it up.

corner detailplate assembled

I bolted the 2 upper L brackets into studs with 2 3/8" lags about 4 inches long. I used a tape measure to approximate level.

wall bracket

Ann and I carried it into the shop and hung it on the top brackets and got 2 bolts in place, then I put the bottom brackets on.

Those of you who have seen this corner of my shop before can appreciate the mountain of shit that I snookered Leester into moving so I could even see that wall...I had to get him drunk first.

onto the wall

At this point I spent a little time going around with the wrench making sure everything was as tight as Roy.

One more mechanical step coming up.

Some years ago I thought I'd blown a speaker on my bagger, so I went out and bought a new replacement, spent a day pulling the faring apart only to find a wire had fallen off the speaker, so I dug that new speaker out of a box and gave it a new job. After careful consideration and some convoluted thinking I couldn't begin to describe, I engineered a method of attaching this driver with a minimum of fuss and bother. I glued a bit of soft plastic tubing to the edges of the speaker leaving gaps so the cone could maintain free excursion yet have full contact with the plate with a small bit of pressure that I could adjust with a 10-24 nut on each side mounted to a pair of 1 inch aluminum angles that are attached to the frame at the top and bottom with #10 Tek screws. Yes, I gave thought to just drilling a couple of holes in the plate and mounting it directly and that may happen yet. I notice that the current method tends to shorten the decay to a tasty length so it may stay the way it is now.

driver detail 1driver detail 2strut detaildriver strutsdriver installed

Ok. That took care of getting signal onto the plate. To return it I chose Dean Markley's acoustic guitar pickup, the Artist model since it was a robust piezo with a frequency range of 1-100K which pretty much covers everything I could throw at this thing. The pickup attaches to guitars with a little gob of goo so it doesn't mar the finish, but here I have a couple of small clips holding them in place in case I wanted to move them. I put them on the edges as far from the driver as possible, centered top to bottom.
After hearing it, that's probably where they'll stay, so I'll use something like a dab of Liquid Nails to permanently mount them.

Dada Gooweinerschnitzel

Along the way I soldered up a speaker wire and 2 balanced extension cables that I pulled through the wall and routed into the CR behind the board.

pro wiring

So there it is.

finished

Behind the board I chose this little box to power the driver. It's an old Moviola that's been reworked as a 3W guitar tube amp. I'm sure it will get replaced with something more appropriate but it's what I had laying around. Coulda used a Marshall head I guess.... but for the power requirement I'm guessing even an old stereo amp would suffice.
Also I'm not certain that having a tube in front of this thing is better than a clean ss signal.

peetcher

I ran the piezo's to this old TL dual valve and from there into a couple of channels on the board so I could do some serious eq shaping. As you can see it's all gain staged at about 50%. There's room for fudge, push and pull.
the catcher

It sounds like God's own shower stall.

There's a sample at the bottom of the page on something we're familiar with.

I may build another and just throw out these honking little reverb boxes because they can't touch this.

Caveats:

If I do it again, I'll get the metal shop to roll the sheetmetal up and tape the hell out of it for transport. I tried like hell to keep it flat but it got a couple minor kinks in the process. It was a lot more flimsy than I expected. A larger table to work it on would have helped too.

Also, I may at some point re-borrow my welder back and tack some gussets on the corners of the frame. As stiff as it is I think that may reduce the frequency of retightening everything.

Also the eyebolts are a weak point. I'm noticing they can open up and lose tension over time so I may replace those with a welded eye and a threaded chain link. That may run another 10 bucks.

I looked at the cute little homemade torque wrench that someone posted and saw the little tensioning bolts on the original and decided.......to tighten the piss out of the eyebolts. The big clue was the comment made about tuning to taste after torquing it down, so I used my torque wrist and set it to tight as piss.

I also notice a bit of line noise if I crank the gain. A better piece of wire with better shielding would probably fix that. 30 ft is a long run for a piezo.

Now the interesting part:

Unistrut-$54
Sheetmetal-$50
Misc hardware items-<$50
Pickups-$32 ea
Driver-$20

So about 200 bucks and change to scratch one of these together. Bring your own amplification.

total build time: about 4 hours over 4 days.

Yes, I know, the plate needs to be polished out and oiled so it doesn't just sit there and rust the hell up. I'll get to that.

For the finishing touch I'll go out to the woodpile and build a simple box to cover it up, isolate the ambient noise a bit and keep it clean, but you prolly don't want to watch me in the woodpile. Bet this thing would sound incredible if I started a Harley out there.

You may now bask in the 5W glow of my awesomosity. hehe

notes, thoughts and references:

The classic EMT plate was 2.4m x 1.2m and 0.5mm thick ------ 7.87ft x 3.93 4x8, close enough

25ga 7/320 = .021875 = .555625 mm

24 ga cold rolled is what we're after, 25 is hard to find------26 would sound more trebly....hm.....stainless steel is a little harsher sounding....original was cold rolled

rust. gah. pick up beer who borrowed my polisher? dog till Thursday

linkies

http://recforums.prosoundweb.com/index.php/m/0/20649/208/0/

http://malcolm.bignoisybug.com/rsdp/chamber.txt

http://revolutionrecording.com/NewsOld.html

http://danalexanderaudio.com/emt.html

http://www.platereverb.com/www.platereverb.com/manuals/Plate%20Construct...