Wiring a 3-way switch into a speaker cabinet?

[Morganhop]

Hi. First off, I'm new to this so forgive me for my ignorance. I'm sure this is a stupid question but please indulge me.

I started building speaker cabinets for guitar amps last year. I've got the woodworking part down pat - no problems there. However, I'm totally new to all things electrical. The cabs I've built so far were wired the old fashioned way - 1/4" jack to the speakers. That's it, nothing fancy.

I'm building a 2x12 cab for a buddy of mine to use in his studio. He wants to mix two different speakers. This may be a dumb idea in the first place, but if was wondering if I could wire in a signal switch so he can have the signal go to one speaker, or the other, or both simultaneously. I play a telecaster with two pickups - bridge and neck. The pickup switch allows me to play through one or the other, or both. Is it possible to wire speakers the same way, and if so, how difficult? Also, would running the signal through a switch like that weaken or degrade the signal from the amp in any way.

I think for studio applications, being able to switch up the speaker configurations would give a cabinet a lot of versatility with just one little mod.

[Mick Bailey]

Mixing two speakers each with different characteristics is sometimes done (e.g., Bogner Alchemist) but mainly they're not switched due to the impedance being matched to a particular amp. With solid-state this becomes less of an issue, though you drop some output power when switching from lower to higher impedance say, from 4 Ohms to 8 Ohms.

Running through a switch won't degrade the signal unless the switch is defective.

There are more involved approaches to keep the impedance constant, but in terms of simple switching you need to consider that the amp will see either the standalone impedance of whichever speaker is switched in singly, or the combined impedance of both speakers in series or in parallel. For an amp where there's an impedance selector on the back this won't be a problem so long as the amp is switched at the same time the speaker is switched.

It's also not a good idea to switch the output of a tube amp while it's operating.

[sgelectric]

I've heard that when mixing speakers it is a good idea to select speakers with similar sensitivity (efficiency).
Otherwise the speaker with the higher efficiency will appear louder for a given signal.
This assumes of course that you are looking for a balanced output from each speaker.
Just a thought. YMMV
SG

[Enzo]

That is on paper, but when the difference is only a couple of decibels, you will never notice that one voice is slightly lower than the other. And when mixing speakers, one may have a higher efficiency rating, but the tonal differences across its response band wash that difference away. Efficiencies are done at one freq, not full range. Efficiencies are also straight out front, so any beamyness will not be considered.

So if you combine a tone tubby and a vintage 30, you are more likely to notice the difference in tones between them than the fact one is a decibel louder.

[g1]

You will want a good quality switch capable of high current. In case the cab is connected to a tube amp you do not want the risk of an open circuit due to a bad switch contact.

[Mick Bailey]

You will want a good quality switch capable of high current. In case the cab is connected to a tube amp you do not want the risk of an open circuit due to a bad switch contact.

Agreed. A make-before-break switch would be best. Usually toggle switches break as they switch. If I were doing this I'd go for a switching arrangement that needs to be deliberate - such as a good rotary switch. A toggle switch can be accidentally flipped too easily. You could also run two inputs to give you stereo as an option.

You'd have;

A or B mono
A and B stereo
A+B series
A+B parallel.