Originally Posted by
mostapha
Actually, you can figure it out. Find any subtractive synth plugin and generate a sine wave that does not clip when rendered. Aim for it to be as loud as possible without intersample modulation distortion or clipping, or about -3dB as a general guide if you don't know how to test for that. It doesn't really matter what frequency you use, but I'd make separate ones at 110Hz, 440Hz, and 7040Hz if I knew nothing else and wanted to be thorough.
Burn a couple minutes of it to a CD or put it into traktor or whatever. Set up your sound system the way you normally would with the channel gain all the way down and the EQ flat. Then start playing them with every feature off: 0% pitch, keylock off not gridded, all limiters off, etc.. Have somebody watching the amp level to make it loud enough to hear clearly but not loud enough to hurt, and don't let the amp clip, because that will defeat the purpose of the test.
Then just start turning things up. You'll hear it start clipping, though if your ears are shot, you might have questions about where it starts.
It doesn't take more than about 2 or 3dB of clipping to become painfully obvious if it's a digital mixer with no soft-clipping protections. With analog stuff that's made to clip in a pleasing way, it might take a bit more gain overlap to make it painfully obvious, though you should still be able to hear only a couple dB.
When you figure out where the mixer starts clipping, take off another dB or two as a safety margin…put a sticker on the level meters that caused it (all channel meters and the master meter are good places for them) and never peak above that level. If you need it to be louder, get more powerful amps or turn them up more (also, never clip them…though you can probably trust their lights if you've read the manual and know what they actually mean).
That way, you'll get all the dynamic range out of your system that you can without squashing the hell out of your signals, wearing the speakers, or fatiguing people's ears.
Just a quick note and something most of us are familiar with…Traktor clips sound card outputs if it peaks above about -0.2dB. The apparently negative headroom is probably the result of intersample modulation distortion, but it sounds like crap if you let it clip at the output…and its limiter doesn't sound much better. Based on my tests, the highest Traktor's master output should ever be set is about -14dB, though if you have enough quiet (as in noseless) gain on your DJ mixer (or whatever gain stage is after your master output if you're using a controller) and you're using 16-bit files, you can run it down to about -40dB before you lose any dynamic range. That number (-40) is based on the assumption that Traktor works similarly to most of the popular audio processing stuff out there and some basic testing that showed me it was at least that value if not even lower. But -14ish dB works fine.
How much does it matter?
Well, I think it matters a lot, but…I also haven't been in a club without earplugs since 2004 to protect my hearing. Despite owning very good musician's earplugs, I almost always wear $15 hearos earplugs because they roll off the highs more. I have yet to go see more than 2 or 3 DJs that didn't clip the shit out of the mixer. A couple weeks ago, I had an interesting conversation with a promoter wondering why the sound system sounded weird…the reason was because he'd never heard what dance bass sounds like if you're not clipping the DJ mixer by running it into the red and turning up the bass EQ, eliminating any semblance of dynamic range on the low end. Apparently, he'd never heard a subwoofer not distort before.
So, obviously it doesn't matter that much if you're okay with fatiguing everyone's ears, costing venues and promoters money in damaged cones, and sounding no less like crap than everyone else. It's not a huge degradation in sound quality for most people who've already damaged their hearing anyway. But if you understand it well enough to explain it, there's not really a reason not to unless you're going to get fired for doing things right…which I could see happening if the promoter is really dumb.
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