Head Room

Hello people

I am trying to grasp the " true " meaning to this terminology but a lot of what i read is confusing me and would just like some one to explain it with out confusing me even more.

Here are my problems understanding this:

Must the audio within the mix have head room or is it the sum of all the audio channels in the mix and the head room should be taken into account at the master channel ?

Is head room in the mix the same with a digital signal as with analog and i don't mean the bit rate, just the signal its self ?

and if i am using digital fx processes with analog audio will this have any effect on the total amount of head room i can physically achieve in a final mix or on the master ?

As i am sure you can see i don't really understand the concept of head room and i really would like to understand it better to get more volume out of the final mix.

Thanks
peter

[MASSIVE Master]

The "True meaning" of headroom is the space between the nominal (or "normal") operating level and the point of failure.

With digital, it's simple -- "Fine, fine, fine, fine, fine, CLIP!"

With analog, it's a completely different story -- "Fine, a little questionable, spectrally skewed, wholly distorted, CLIP!"

You'll notice that converters are calibrated to a point of line level... Let's say that a particular unit is at -18dBFS (=0dBVU). A signal riding around -18dB(FS)RMS is going to be at the "normal" operating level in that case. Depending on what you're recording, you might have peaks as high as -8 or -6dBFS here and there, but the "meat" of the signal will be riding around -18dBFS.

That's your "built in" digital headroom --

The analog side gets more complicated with "actual" headroom and "USABLE" headroom -- With a lot of gear, those are two completely different things. I have some gear that sounds fine when you're "overdriving" it 12dB hotter than it was designed to work. I have some gear that starts to sound like complete crap above nominal also - but technically, the circuit hasn't failed completely yet - So on paper, it's still considered "headroom."

The REALLY important part is to make sure you're TRACKING with a good amount of headroom. Personally? I rarely, RARELY if ever peak above -12dBFS at any time on any track if my converters are calibrated to -18dBFS. Usually lower. I'd rather have a clean signal peaking at -24dBFS than a compromised signal at -10dBFS.

Once you're "in the box" those analog rules go out the window (assuming you're STAYING in the box) as with your digital signal, as long as you're not approaching the clip point (-0dBFS) you're in reasonable shape.

Sure, there are exceptions -- You can "overdrive" a digital signal into a digital compressor and then turn it down at a buss or something. But I hope that cleared it up a little...

[fooman]

I'm also trying to wrap my head around the ways ppl work here with metering and headroom. It's starting to click a lot more lately, so I'll try to explain what helped me. If I'm off at all, feel free to virtually punch me.

One thing that really helped me personally was to set my DAW to meter in PEAK-RMS, so I can see both in my digital meter. That is when I learned the difference between PEAK and RMS metering, and why you have to really read the advice given here. John, above, stated that -18dBfs RMS is nominal... but you would surely see transients of, say, a snare drum peaking around -6db or -3db if you are watching Peak-RMS meters in your DAW. If you don't have a VU meter handy then using your DAW's RMS meter is a must in my opinion. The two types of metering are vastly different.

Go do a search for a thread about ppl using limiters on their master buss in their DAW's. A reason for this is because although your master buss might be around -18dBfs RMS, it's peak meter could get around 0dBfs. There are other reasons, but that's one of them.

I'm ashamed to admit this, but I used to mix really really quietly because I didn't know the difference between the two meter types... and my mastering engineer told me I could probably send in louder mixes. I found that it was because I was metering in Peak.... -18dbfs in peak is very quiet in RMS...
=\

live and learn.

[MASSIVE Master]

I think (at least for me) that after a while you find that you can use the peak meters just fine also...

Tracking, I just try to make sure that transient signals peak somewhere below -10dBFS or so (better to be safe than sorry) and sustained signals somewhere below -18dBFS.

During mixing, most of that goes out the window and it's more or less a matter of bring "reasonable" -- Don't clip, maybe a few dB of headroom, no problem.

Although of course, I'd rather have VU meters everywhere, I'm still going to be running short of 0dBVU 90% of the time.

I like to think of myself as a GearSlut -- But first and foremost, I'm a Headroom*****.

(EDIT) Whoa! I can't say the word *****?

(Edit again) Evidently not... Okay, it's a word that sounds like "door" but with a "H" sound at the beginning.

Thanks Guys

Really good food for thought and i have a lot to learn.

Back to the books for me

peter

[Keldog]

*****...

[Keldog]

Not that I didn't trust ya, John...

[Jason Poulin]

ahhh ok I guessed it now



*****?


(edit) **** yea!!!


(edit again) my word... sounds like duck but with an F intsead


ps: sorry for the highjack... carry on!

[jamsmith]

Headroom is really an electronics issue. I sincerely believe anyone who truly wants to be involved in audio engineering should have a strong grasp of the basics of electronics. However, the concepts themselves can be grasped purely in context of audio work. I suggest the Yamaha Sound Reinforcment Handbook. This tome deals exclusively with live sound, but it does an excellent jobs of covering the basics that apply to all of audio.

Originally Posted by jamsmith

Headroom is really an electronics issue. I sincerely believe anyone who truly wants to be involved in audio engineering should have a strong grasp of the basics of electronics. However, the concepts themselves can be grasped purely in context of audio work. I suggest the Yamaha Sound Reinforcment Handbook. This tome deals exclusively with live sound, but it does an excellent jobs of covering the basics that apply to all of audio.

Just started reading it yesterday, Section 3 is nice but heavy reading ! I think this is also available on DVD ( i could be wrong ) but it would be nice to have the part on signal processing equipment explained visually or maybe i am just too lazy