What to Do With a Lot of Salvaged Speakers?

[Audioguru]

Correction to what I previously typed:
2) Connect two speakers (especially the same kind) in series to the output of a modern low output impedance amplifier and tap the cone of one. The resonance will be damped only a little.

 

[BobK]

I can see @Audioguru's point. Putting the speakers in series adds a resistance to the circuit between one speaker and the amplifier the same way adding a resistor would. What would happen to the damping factor of a modern amplifier if you added an 8Ω resistance in series with the speaker? It would become 1, no?

Bob

 

[Audioguru]

The impedance at resonance of many 8 ohm speakers is 40 ohms so having two in series produces no damping at resonance.
The damping factor of a modern amplifier is more than 400 so its output impedance is less than 8/400= 0.02 ohms. Then the speaker does exactly what the amplifier signal does. A loose undamped speaker "does its own thing".

 

[FuZZ1L0G1C]

Gluing springs to the cones to make bodge-it spring reverb with a piezo out is fun and surprisingly effective, especially if you find a way to vary the springs tension.

I did a similar experiment long ago, (1970's) using a diaphragm-ripped 80W 4" 4-ohm Pioneer car speaker.
The center-cone was epoxied to a small plastic tube, itself epoxied to a square of Paxolin (PCB).
Four springs from old 'Ding-dong' doorbells supported a salvaged voice-coil wired to a preamp via twisted-pair Litz wire. Salvaged center-magnet-on-rod formed the core. All enclosed in long box. Amplified guitar 'Spring-reverb' used to drive my parents nuts when practicing "Crimson & Clover" riffs.

 

[FuZZ1L0G1C]

but I have a carpentry hobby, so I might be able to make them using calculators online for the dimensions.

Maybe you could network several identical speakers to create a virtual "larger diaphragm" driver, feeding a wooden labyrinth enclosure. Books such as @Bobnoes mentioned have construction details.
As for surround, it depends on the source device.
Some amps have line outputs (usually RCA phono sockets), which would need amplification or attenuation.
If you don't yet have surround, there are circuits (and kits) for stereo>surround encoding.
Cabinet Dimensions: The 321 ratio is a good place to start.
3 x = height; 2 x = width; 1 x = depth.

 

[Audioguru]

One cheap speaker sounds like a cheap speaker:
1) A high resonant frequency with no deep bass.
2) A peak in the upper midrange with no highs.
A network of these speakers will sound the same but can be louder than just one speaker.
A large "super diaphragm" will be very directional.