Motorola console reverb tank?

[elitopus]

I picked up this motorola sk-71 console recently. Im trying to figure out what this long box is. Is it a reverb tank and how does that work?

The box has a single RCA output so does it send signal to the center 15" driver only? This console is a 3 channel amp with a pair of two way speakers and a center 15"
I need to do some research and get the schematic for this console too

 

[Tom Bavis]

Input is a sum signal from R and L channels, output goes to the center channel amp (after the low-pass crossover). So center is bass and reverb channel.

 

[gadget73]

sure looks like a reverb tank. They have long springs in there that vibrate with the music. They have pickups at one end sort of like what you'd find in a guitar to create the output. The springs cause a slight mechanical delay between when the speaker makes the noise and when the pickup turns it back into signal.

 

[elitopus]

Thats interesting that it only goes to the center bass speaker. So the xover must be active because there is no network on or near the center speaker.

 

[gadget73]

I believe its actually passive, but its at low levels in the preamp. If you have a look at the schematic, you'll see several capacitors off the input jacks. I can't recall how it works precisely without looking at the schematic but the L and R jacks sum together through some resistors and feed into the bass amp. I seem to remember a couple caps to ground to serve as a low pass filter. The L and R treble amps have caps in series with the amp input to work as a high pass filter. Its not a hugely elaborate setup, but it works.

 

[tom3]

Nice long can too. Might take that output to a separate amp and a rear speaker, very nice effect with the reverb as a back channel. High quality stuff in that console back in the day.

 

[Victrolaman]

Yes that's exactly what that is. I have a 1961 Drexel Motorola and it has one. You should have a control that cays Vibrasonic on it. it adds a hall or echo sound to the music or what your listening to. Sounds great on live performances. mines very sensitive though I can only have it between 2 and 3 if that, anymore and its to much. It has its own speaker for that.