It makes a big difference as to whether you are talking about active (powered) monitors or passive (unpowered) monitors.

For active monitors (or passive monitors with separate external drive amplifiers), there are several solutions, one of which is the SM Pro Audio [="http://www.smproaudio.com/index.php/en/products/monitor-controllers/m-patch-v2"]M-Patch series[/]="http://www.smproaud…"]M-Patch series[/] of boxes. These have not only a passive level control but also push-switches that send the line-level signals to any combination of two outputs. If you need the choice of more than two sets of monitors, you should look at something like the Mackie [[url=http://="http://www.mackie.c…"]Big Knob[/]="http://www.mackie.c…"]Big Knob[/].

If, on the other hand, you have passive monitors and only one power amp, then you should consider heavy-duty rotary or heavy-duty push-button switching of the speaker leads. The flimsy type of loudspeaker switch commonly peddled in audio hardware stores is not really up to the demands of studio use. Note that it's much more difficult to match acoustic levels between the different sets of monitors when it's the power amp outputs that are switched.

Boswell has made some very good recommendations of which I also agree with. But there are also other less expensive solutions than that.

Let's just say, this scenario would assume something like a pair of passive monitors and a single amplifier feeding those monitors. A pair of powered smaller monitors or just another pair. And a pair of average crappy external computer speakers that also have their own built-in amplifier.

You'll find at Radio Shaft, Best By and others, a simple RCA in with three pairs of RCA outs and three front panel switches on the $10 switcher box. And this will be something of a juggling act. Now you already must realize, that no computer speakers are going to play like a fine pair of monitors at the same volume levels, SPL capabilities. But that doesn't mean that you cannot match all of the levels independently on the amplifier feeding the speakers, the powered monitors and the computer speakers that have their own amplifiers built in.

So on your computer audio interface device and/or software, you pop in a commercial CD. One in which you value the engineering and sound of. Not your own product that's for sure. And you turn up your computer audio output to a level in which it is not clipping the outputs of the computer audio interface device.

You select position 1 on your switcher. You turn on your power amplifier and adjusts its level on your monitors to what you believe would be your most desirable monitoring level. Not too loud and certainly not too soft. We're not going for absolute loudness right now.

Now switched the switcher box to position 2. Turn on your powered monitors and adjust their levels to effect a similar loudness level to the previous monitors.

Now switch the switcher box to position 3 and turn on those awful powered computer speakers. And attempt to match level with the previous powered monitors. Which should match level to the passive monitors with the power amp. And you should be good to go for under $10. Will it have perfect cross talk specifications on the $10 Radio Shaft box? Hell no but it won't make any difference for you.

You really don't want to be switching the physical output of speakers because each and every individual speaker has a different efficiency rating meaning that it will play at different loudness levels than other speakers even with identical match power level inputs going to them. The high fidelity speaker demonstrations of yesteryear in the hi-fi shops switched the speakers through a special high-powered speaker switcher box, of which, efficiency differences in speakers could be matched between a pair you might be auditioning and thinking about purchasing. But doing those things on the output of power amplifier is connected to speakers does not really present an accurate reference judgment to be made. And those speakers at the hi-fi shops never sound the same when ya get them home. And that was based on the acoustical surroundings and not the speakers.

So without a properly designed acoustically engineered control room and no budget, that's your option. And pretty much your only option, without a budget.

Those external control room monitor devices that offer independent switchable outputs, talkback/studio address and monitor dimming still all run a couple of hundred buck's US. Which may or may not be within your budget? They are certainly more accurate but they are also not passive. And a simple line level passive switcher box will add no influence or coloration of its own. And with which, you will only be hearing the active electronics within your computer audio interface and not another amplification stage in between that that those nice monitoring devices all do. And as straight wire is better than any transistor you could possibly go through much less a chip with 50 of them. So a straight line level passive switcher box is really the way to go. And it's also the cheapest thing to do. In fact it's the exact way I do it with my own home built passive switching box. And with which works well from my 36 input Neve desk that only has one monitoring output. And I have three pairs of monitors both passive and active ones in the control room. And it works great.

That's a rudimentary nonlife changing function.
Mx. Remy Ann David