I came up with an idea a while back to take the speaker output of a amp and run it to 1 speaker as normal. But then also run it to another cab through some kind of device that can handle speaker level that would add a delay of about 30 to 60 ms. This would create more or less a "Stereo sound", from a mono source. Problem is, for the life of me I cannot find a device to do that. Obviously I could get a delay and set it to 30ms and run it to a second amp. But i feel like something has to exist to do this, or could be built. and should be cheap. I am quite good with electronics and soldering, just not with electronics design.
This could also be used for time delayed speakers, to compensate for distance, without having a separate amp.
I can think of 3 kinds of delay:
1. Speed of sound through air (speaker position or horn length)
2. Analog record/playback (record head -> tape -> repro head)
3. Digital record/playback (ADC -> DSP -> DAC)
Unfortunately none of these operate between the amplifier and speaker. Passive crossover components (inductors, capacitors, etc) do introduce artifacts that can be considered delay (nowhere near 30-60ms though), but they wreak so much havoc on the phase and frequency response that I wouldn't consider them for a straight delay.
Hate to be the bad guy, but creating stereo from mono through delay doesn't sound great anyway IMHO. How about a nice stereo reverb. With a stereo amp.