from reading your gain structure applet i assume that recording @ 24-bit will provide a lot more headroom. is that correct?
Yes it is. Think of it this way: when you're recording to digital, the total amount of dynamic range you have to work with - i.e. the size of the digital "canvas" on which you can paint your musical picture - can be roughly calculated as the number of bits times 6dB, then subtract 6dB from that result.
This means that 16bits gives you a total of (16x6)-6 dBs, or 90dB to record witin. 24bits would be (24x6)-6, or 138dB of total range to record within. That means that 24bits actually gives you an extra 48dB to work with. Or to put it another way, you can push your signal down lower in 24bit without having to worry about hitting the floor, in turn giving yourself just that much more headroom to play with without haing to worry about clipping.
This is what I mean when I say it's damn hard to record "too low" in 24bit. You have a lot of room to push the signal down without having to worry about bottoming out, giving you just that much more headroom to play with in turn.
But the thing to remember though is that RMS level does not mean peak level. When I say RMS at -18dBFS (for example), that means the average overall signal level. the peaks will easily fly above that Which brings us to...
so if i can maintain an RMS level around -18dbFS, +/- 4db. anything that peaks above that could be corraled by compression, provided it doesn't squash all the dynamics i need to maintain in the final mix.
While it is possible that you may approach clipping when you RMS at -18dBFS, it's pretty rare to find signals that are quite that dynamic. 8 times out of 10 you should be safe. However, if your input signal *is* that dynamic (technically speaking, it has a crest factor of 18dB or greater), I'd personally just turn the record level down instead of compressing or limiting the peaks.
The difference is that compression will change the nature of the signal, and therefore the actual sound. If it's a change you want, ten it's fine, of course. But f you'd rather just record the clean signal and wait until you mix until you make compression decisions (which is what I personally prefer), the just turning the record level down is the way to go. It will not change the sound at all, it will simply only record at a safer record level.
An exception to that that happens a lot for me is when you get a vocalist who is inexperienced in studio technique and tends to wander all over the place in relation to the microphone, unintentionally causing their levels to also wander all over the place. It can be really hard to keep sensible recording levels that way, and often limiting or compressing on the way in is needed just to keep things under control. But the catch there is, depending upon your DAW, your limiting plug-ins may or may not work while recording. You'd have to research that for your DAW. I avoid that by using an outboard analog compressor or limiter before the signal gets to my DAW, but if you don;t have that ger available that may not be an option for you.
G.