headroom and bit question

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guhlenn

guhlenn

Oh REALLY????
hi,

so i posated this question in a thread but haven't got an answer yet. it'lll probably be an extremly dumb question but here it goes anyway:

is having 20 bit A/d conversion and 105 db headroom the same as 24 bit A/D conversion and 105 db headroom?

is headroom the final value i should look at or has a larger bit depth another advantage?

thanks guhlenn;)
 
Not the same, 24-bit card will handle more of the math that audio becomes in the digital domain, resulting in increased harmonic content and dynamic range. Stats have there place, but your ears are the best judge.
 
105 dB headroom doesn't make any sense to me. Headroom's the difference in dB between the signal level and the point at which clipping occurs. Say that digital recording clips at 0 dB. Say your average signal level is about - 6 dB. That gives you a headroom of 6 dB.

But more bits gives you more headroom, in that the dynamic range of 24-bit is greater than anything lower, so you don't have to track so hot, which means you stand much less chance of clipping, which means studio life is much more relaxed and productive. :)
 
are dB arithmetic or geometric?

say you have two sources recorded at -12dB. when you combine those, they should in effect be louder. but how much? im sure this is a problem while mixing in digital, you have to know when the output stereo file will no longer be anything more then a garble of cracks and distortion. or am i completely wrong?
 
ok, i read this in prorec.com haven't got a link for you but do a search there on "what's your dB IQ"" or something like that. and the answer is (if i remember correctly): 3 dB. but it could be 6 dB. i forgot goddamnit. i 'll check on it...

thanks BTW. but bbal, something doesn't make sense to me either. you say that 24 bit will handle more math (that i can understand) but headroom is a resultant right? when better components are used then headroom goes up (or down depending how you look at it).
so assuming that each product has honest specs(i know i know) then a good 20 bit card should be able to deliver the same headroom as a somewhat poorer 24 bit card.

it's not that important i know but i'm curious.

thanks Guhlenn
 
kristian - when you play two digital tracks back, yeah, the level is always higher than either of the two tracks individually, but only slightly. Guhlenn might have found it, because it seems to be about 3 dB. If that's the case, then the question now is: what happens if you sum 3 tracks? And four tracks? Does each additional track add about 3 dB to the overall level?
 
Due to physical limitations (internally generated thermal noise), most 24-bit converters are actually limited to about 20 bits of resolution.
 
Yea, that is my whole point. say you take 16 tracks of audio which average at about -12dB but all peak around -3dB, at one point in time, the end file could be all distortion.

Question: while listening back in say Vegas will you know if you are mixing to hot while previewing your mix, will the meters read 'clip'? or does that only work on the stereo file once you i dont know what the term is, but i gues compile all 16 tracks to 2 stereo tracks. ie. would you know to turn the levels down before wasting time mixing and exporting the file?
 
kristian - in playback, the meters aren't as important as your ears - if it's distorting, then it's clipping. But since I record more than one track simultaneously, I never know if the distortion comes from one of the tracks only, or if it comes from the summing effect. So I mute everything but one track at a time, and listen again. If the individual tracks are clean, I save the take, and make level adjustments later on in the mix - either cutting the level of individual tracks, or cutting the level of the whole mix.
 
hi,

doubling the sound source causes a 3db increase. but i don't know if this is true for multitracking, somehow i don't think so.

but is it fair to say that a 20 bit converter can sound just as good as a 24 bit? or is there always a difference?

greetz guhlenn
 
er... yes and no...

I think you would be hard pressed to hear a difference in high end 20 bit converters (Apogee for example) and the 24 bit converters in a pro-sumer card (like my Gadgetlabs 496)
It has as much to do with design as it does bit depth. With 24 your odds are just a little better...

kristian,
The odd thing about Vegas is that there is no master fader or meter when running multiple busses. This can leave you blind. But, when you mixdown in Vegas, it seems everything gets dropped like 6 db. If you take a single track, mix that down to another track, assign the two tracks to different busses, you'll have to boost the volume 6db (usually at least) to get the second at the same level as the original. Why? I dunno. that's just how it is. It's not really a good thing at all. Vegas is quirky like that. Vegas does sound good though. You can have the busses peaking all over the place and still when you mix it all down to stereo not get a single over. Vegas is for dummies. You don't have to be so carefull, they built a litte extra room in there. Still, you have to be willing to do a lot of trail and error. ANd you have to use your ears more than anything else, which is a GOOD thing.

-jhe
 
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