Pickups
All the commercial units use Piezoelectric pickups or accelerometers.
These are basically contact mic/pickups and are available from several
manufacturers. As a matter of fact, you probably already own one,
or at least know someone who does. Some examples of available units
are those from Barcus-Berry, Fishman, and Frap. Some pickups need
no preamp and can be plugged into the echo return(s) on your board.
You can also return the output of the pickups through two mic inputs
on your mixer, using a tube, discrete class A, transformer or transformerless
(differential), FET, IC DI. These are some of the variables that
you must work out depending on the console you own, and the pickups
you use. Try as many pickups as you can borrow until you find one
that you like and that easily interfaces with your mixer. For a
mono reverb, place the pickup near one of the side frame reinforcements.
Experiment by moving the pickup up around, and down, on both sides
of the reinforcement, until you find the spot you like. Then secure
the pickup by epoxy, wax, putty, or whatever the pickup manufacturer
recommends. Run the pickup wire down the reinforcement, again using
"ty--raps" or tape. For a stereo unit, do the same thing
on the other side (Figure 8). *[After much research
and development, we have found the pickups, and preamps that work
best, and are the most cost effective.] *
Figure 8. The finished reverberation
system, with driver and pickup(s) in place.
Tuning the Plate
With the pickups in place, the plate itself now comes into focus
for tuning. In theory, think of the plate as similar to a drum head.
Also, correct tuning means all the lugs are equally tensioned. So,
start by holding the hooks suspending the plate in the frame with
a pair of "vice grips" or similar pliers, and tighten
the nut on that hook with a ratchet wrench. Do this evenly around
all eight hooks. How do you know when the plate is tuned? Good question.
You don't, really, because every manufacturer used their own method
for tuning. EMT shipped units pre-tuned except for four nuts, which
were supposed to be tightened by exactly 1/4 turn when installed.
Most independent EMT servicemen will tell you to tighten each one
until a spring suspension clip breaks, and then replace it and tighten
until 1/8 of a turn before it breaks again! Lawson and Audi-ence
shipped their units pre--tuned, no adjustment necessary. Ecoplate
supplied a spring gauge and specified pushing the gauge against
the plate at all eight plate tensioning points, until there was
approximately 150 pounds of pressure at each point. As a total contrast,
Stocktronics used no tuning at all, claiming the steel was pre-stretched/tuned
during manufacturing. In fact, their plate was simply suspended
by six springs in a very light aluminum frame.
Which method is correct? Any/all/none, depending on your point
of view. One thing is certain, though. If you like the way it sounds,
it's right. So I suggest tuning by ear. Remember, the tighter the
plate, the tighter the bottom. It is usually better to over-tension
than under-tension. Also, listen for "flutters" or "beats"
(like two slightly out-of-tune guitar strings) on the decay of the
reverb, and even-out the tension until they disappear. EMT warned
about the "oil can effect," a very metallic sound that
is heard on an obviously out-of-tune plate. What I suggest is to
find an existing plate you like in a studio near where you live.
Rent an hour of time, and bring along a tape of various tracks-snare
alone, drum kit, congas, tambourine, voices, piano, and run it through
the plate. Record the reverb return on one track of a two -track
or cassette, and your original dry signal on the other. Bring it
back to your place and pan the dry signal to the center of your
monitors, and the reverb send from their plate on the right. Send
the dry signal to your plate, return it to your mixer, and pan it
to the left. Now you can directly compare your plate to theirs,
and tune and equalize until the sound of yours equals or betters
theirs (subjectively)! A CD like this is available, made using both
an EMT 140 ST tube unit-the "classic plate" sound, and
a plate made utilizing the techniques and parts described in this
article. To hear what the finished product will sound like, listen
to some MP3s of the one we built using the components we found sounded
best. Go to this link www.errico-associates.com
and click on the picture of the plate.
Notice the deep, smooth bass, and crisp, sparkling highs-as well
as smooth decay. Sends chills up your spine, huh?) Use your ears
and you can't go wrong.
Talk Plate Reverb with Bob
Buontempo in his PSW Rec Pit forum.
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