Originally Posted by rabident
Can you walk me through how that is an absolute? Where does +10db get clipped? Wouldn't the volume I am listening at matter, as well as the headroom available in the amps & speakers at that point?
If L-R contains the same bass, but down 10db, and I can turn L-R up by 10db without clipping, why couldn't I turn it back down -10db and have room for +10db LFE mixed in?
Also, since LFE is just 1 channel, if it was spread over LCR, wouldn't that mean less than 10db per speaker since all 3 are working to reproduce the bass? More than normal, but each speaker wouldn't have to do +10db on its own.
I have a sub, but it doesn't look nice in the living room. I feel like the speakers are capable of reasonable amounts of bass for my listening level. Trying to understand if this is an Oppo / Dolby specs limitation that might be handled better with a dedicated pre-pro, or some inherient technical limitation that I'm not understanding that will make it impossible for any other pre-amp / processor as well.
Here's the deal: Full scale on an Analog output is designed around the bulk of the sound -- the mid-ranges. There's headroom for peak sounds, but not that much. The problem is that impactful bass needs higher volume than that. If you put that bass into the normal speaker channels you will clip the pre-amp because the effects bass is so much louder than the bulk of the sound the preamp is designed to handle.
So instead, you make a special channel just for effects bass, and you record it 10dB down compared to everything else. That lets you put 10dB more bass in the channel without clipping a preamp. But it means you need to add 10dB boost to that bass to get it back up to the desired effects volume. That's done in the amp (in the Subwoofer).
Now, suppose you want, instead, to mix the effects bass and the normal speaker channel together. You can't do that simply by mixing them unaltered because the effects bass is recorded to a different standard (10dB down), and once mixed you can't separate them again so you can't boost JUST the effects bass.
Instead you have to LOWER the normal speaker channel down to the same standard -- 10dB down, and then mix them. But even that is not enough, because the effects bass full scale (loud bass recorded 10dB down) is designed to max out what the preamp can accept. So you have to reduce the combo EVEN MORE. What's done is that the effects bass gets reduced 5dB and the normal speaker content gets reduced 15dB (which makes them match) and then THOSE two are mixed. So now you need 15dB boost to get the desired volume for the combo.
OK, that's doable but when you do that you are now boosting the noise floor of the normal speaker content as well. I.e., when you reduce it 15dB the noise floor doesn't also get reduced -- it's still the same floor. So when you boost it back 15dB the normal speaker content now has 15dB more noise in it as well -- you've amped up the noise floor.
So why doesn't that apply to effects bass as a separate channel? It does! But the effects bass channel is filtered so that it only has bass in it and bass noise is essentially inconsequential -- or much more so than mid-range and treble noise.
The point is, you really don't want to lower the normal speaker content and then boost it back up again. Do that only with bass.