Adding a sub to bedroom setup? Sorry for long post!

Splitting will get you twice the signal (but not double the signal strength, so you’ll lose some power there). And if you use only one half of the split to power one sub, that will give you some signal mismatch on the tops.

More importantly, splitting does NOT split frequencies. You’ll be feeding high end frequencies into your sub (not a big problem if it has it’s own cross-over filter, but that is not a given). You will also still be feeding low end frequencies to your all-range speakers (tops), which is partly defeating the purpose of a subwoofer.

General note: Adding a subwoofer to your setup allows it to take over the lowest frequencies from your tops and take on some frequencies that are lower than your tops can handle.

Example: You have 5″ tops that cover 53Hz and up. Since they are 5″ and can only displace so much air, they will struggle getting the low end powerful. Also they take a lot of available amp energy to make that large air displacement happen.
Add a subwoofer which plays sounds as low as 25Hz to about 200Hz. It also has a cross-over you can set at 125Hz. The subwoofer has a 10″ speaker in it, which can displace much more air, i.e. handle those lower frequencies better. It also has a more powerful amplifier that only has to use it’s power for the limited frequency range of (in this example) 25-125Hz. Since the subwoofer cuts off frequencies under 125Hz from going to your tops, your tops no longer have to work the 53-125Hz spectrum. This frees up a lot of amp energy that can now go into the low-mids and mids. Together this makes for a balanced sound where the tops will perform better (since they don’t have to struggle reproducing low frequencies they are not suited for) and the sub gets to shine by putting all it’s effort into only a small low end frequency-band. And it will give you that additional really low bit between 25-53Hz for that extra bit of umph. The bass you feel rather than hear.

As for hooking it up, a good sub with a built-in cross-over will accept stereo inputs (balanced, unbalanced or both) and have high pass outputs to connect to your tops. Because they are high pass they will only pass the frequencies above what you set the cross-over frequency to. Also it will usually have a seperate volume control so you can balance the low end vs the tops so it all sounds just right. So in your setup: stereo RCA into the sub and single balanced outs to L and R tops.

I am a big fan of buying matching gear in this case. Why? Because the manufacturer will have built the system to be in balance with the other components. I would seriously advise against (new or used) subs from surround systems. Those are fine for living room surround sound, but not ment for monitoring use. Also they will probably have very few of the desired features I talked about earlier. They are made to work well in a matched system with the rest of the surround speakers, with usually very little by way of settings. Often the cross-over is in the entertainment system with the amps.

What you need to do is realize that in order for a sub to be a real asset to your current system it needs to be the right sub. And subs don’t come cheap, expect a matching sub to be 3-4 times the amount of money of a single top. As with everything PA/Speaker related, you get what you pay for. Since you already own M-Audio monitors, I’d strongly suggest getting the matching 10″ subwoofer.

It’s my personal belief that there is no cheaper alternative. If there were, it would have been turned into a commercial product already.

Hope that helps some.

Glad to help. Word of warning. M-Audio is already on the low end of acceptable monitor quality, imho. And the quality difference becomes only bigger when moving to subwoofers. So I’d save up rather than spend less money on a lesser quality sub.

A cheap/bad sub will actually do your setup more harm and you will, most likely, notice the difference sooner with a sub.

An alternative is to move up to a pair of 6″ (8″ even more, but they are really big for near field monitors) that will give you a bit more and bit deeper low, if not quite the same as a sub. But two of those will cost you the same as a sub, so no real profit there.

No, you want an overlap. Usual frequencies are between 75Hz (if you have bigger tops) to 125Hz. I’d experiment with settings between 100-125. There might be text in the manual about the preferred setting if using M-Audio with M-Audio.