Photo from 2004

"If you are always curious you will never be bored..."

This is all done externally with no internal hacking!

I would  imagine most theremin designers have tried to improve the sound of a simple theremin waveform using acoustics including spring reverbs.

"Acoustic methods are natural but often un-friendly."

Share Your Input at Theremin World

First Test Samples:  Some are a hit, more are a miss but reveal a direction to explore never the less.

ews-resonator5.mp3  9.21.13 This sample is created using a single 12" x 12"  1/8" piece of plywood with the speaker transducer mounted in the center. The Cherub Piezo pickup is secured by drilling a 1" hole for the clip to pass through to keep it closer to the speaker transducer. It can also mount of the edge of the plywood. A plastic card is placed between the pickup and and the plywood. This card known here as gift cards which is like a credit card without raised lettering. An extra trick was to add an open ended compression spring off the back of the pickup clip.

ews-resonator8.mp3  9.22.13 Pure acoustics, no reverb applied but the compression spring is epoxy glued to Cherub Pickup which presses against the plastic card on the plywood surface. An inline volume control is used to set input level.  See Photo

ews-resonator9.mp3  9.22.13 Pure acoustics, no reverb applied but the compression spring is epoxy glued to Cherub Pickup which presses against a rubber bucket.  See Photo   

The tape on the spring dampens the effect slightly or it sounds like an indoor swimming pool or inside a SewerPipe as a member of TW would say.

ews-resonator11.mp3  Same as resonator9 Lid closed.   <=  9.23.13 cello11.mp3

ews-resonator12.mp3    Using different bucket contact points See photo, against battery compartment, not using feet. No bucket lid and full spring resonance. Listen to the amount of acoustic reverb his method of pickup creates without damping the spring. No post reverb was added.

ews-resonator13.mp3  Same as above but a closed lid mounted.

ews-resonator14.mp3  No lid on bucket with a piece of tape dampening top two coils of spring and a grocery plastic bag loosely stuffed inside.   

$24.64 Amplified Speaker Transducer powers off automatically ~1 minute after the audio signal is "not" detected. This off action creates a slight mousey squeak, turning on is very clean.  The built in 1 watt power amplifier is what makes this acoustic resonator simple and practical.

There appears? to be a power jack on the amplifier mini pcb though it is not mentioned in the literature? At 3 volts I might add a dual D cell holder for years of lasting power if there is an issue of battery life.

From the EtherWave Standard output is a 1/4" phone plug adapter to 3.5mm stereo to TRS  Y adapter. One leg of the Y goes to an inline volume control to adjust the level driving the Amplified Speaker Transducer on the back of the bucket. The other Y end goes to the right channel of the Sound Card or Mixer input #1.

The Acoustic Chamber bucket uses a Cherub Pickup on the bucket, it's 1/4" phone plug goes to the Mixer input #2.   This will amplify the pickup signal to Line Level with Pot #2  fully clockwise.

To the Main Amplifier from the Mixer you need the proper length cable with the standard 1/4" phone plug going from the Mixer Output to the amp with the two channels that have been mixed. 

You also need a short cable with a mono 1/4" $3.88 ad-on phone plug for the Mixer input #1 and the other end a mono 3.5mm plug to go to the 3.5mm Y adapter at the EWS.

To your Sound Card is a  3.5mm stereo male plug with two RCA male on the other end. Order the proper cord length. $3.35  ad-on
Mixer Output: 1/4 plug to RCA female $2.95 (2 pack) ad-on  Mixer output to connect to the Acoustic left channel to sound card. 
EWS  Y:          3.5mm male mono to RCA female  $4.99 ad-on for the direct right channel Original sound to sound card.

Note: A 3.5mm mono plug works fine in a stereo jack . A 3.5mm stereo plug in a 3.5mm mono jack can create intermittent contact.

All components needed are listed in the table boxes above, a photo for the setup will be posted.

Optional: 

The speaker transducer manufacture recommends very high bond adhesive tapes like 3M-9473PC to bond to surfaces. I think using #6 screws and nuts on the four feet for what we are doing is better.

If only acoustic coupling is used it eliminates the need of a Ground Loop Filter but still giving a very clean sound.

Other pickups to be tested  Piezo Pickup    Piezo Pickup2   Piezo Pickup3

Four channel mixer 12 volt regulated power supply. Amazon  Guitar Center  $19.99 (12 volt wall-wart might be used for the Phoenix)

A stereo Eq-PreAmp might be useful by connecting the output from the EtherWave Standard through the Eq right channel to the resonant board speaker transducer and connecting the Eq left channel between the resonant board/bucket Piezo pickup to the Mixer or Main amp or Sound card.

A square wave audio signal through the speaker transducer might be a more effective sound. This should be ~.5 volts p-p

Compression Spring $3.19 Home Depot

1/4 plug to RCA female $2.95 for two ad-on