Logic 9 Busses Clip With No Audible Sound Difference

[MarkyC]

Hi guys

I have a question, and its really freaking me out in a way and I'm wondering if any of you guys have noticed/experienced it and that there's a answer.

Im currently mixing a song for my friend, i have a nice all round level on the drums and I've bussed all the tracks. Now during playback on logic it shows that my drum bus has clipped 'gone into the red' by over 2.8dB! And its the same with my Master output track. However there is no audible 'clipping' heard.

None of my drum tracks clip and I don't have a compressor or limiter on my drum bus.

is there an 'under the hood' limiter or something taking effect?

I previously used sonar 8 and it always clipped when a bus went into the red and so i pulled it down and then lost the drums presence,

It just really confused me and I want to know if its ok if it happens and if any of you have experienced it.


Regards
MarkyC

 

[mattr]

Most DAWs have audio engines based on 32-bit floating point samples (or 64-bit float in the case of some, including Sonar)...

Floating point essentially means that the location of the decimal point in the sample's value is not fixed and hence it can be scaled up an down to huge or tiny values that could not be stored using the same number of bits as a fixed-point integer. Think of it as having everything in standard form to a certain number of significant figures... the number 3.45x10^9 is no longer to write in that kind of notation as 1.23x10^2, but they have vastly different values if you right them out fully. This is kind of analogous to floating point integers.

OK, it might not be that simple but that's the general idea! Anyway, an offshoot of this is that the calculations within a DAW can handle with rolling into huge values (that represent going over 0dbfs) without clipping. +2.8dbfs in the red is nothing for this kind of audio engine... you can do some ridiculous tests with an extreme series of gain changes and still get a perfect null test at the end. If the audio engine was, for example, running on 24-bit fixed-point math (where 0dbfs is represented by the largest value able to be stored as a 24-bit fixed point integer) then anything over 0dbfs would clip, as the value would not be able to be stored.

So long as the signal does not clip by the time it is pulled back into the fixed-point domain (i.e. during a mixdown, going through a hardware output, etc) then you can honestly screw gain structure within your DAW if you really want to I'd be surprised if there really was a difference between Logic and Sonar. Maybe you were using a plugin within Sonar that could be clipped, or was designed to sound different when 'driven hard' (some of the analog emulation plugins do this)... or maybe your ears just perceived a loss in presence due to the drop in volume... Fletcher-Munson curves, etc... ears just like loudness.

 

[MarkyC]

Thats an amazing relief! I kind of understand the whole integer thing, I'll definitely do some research on it. So basically if doesn't sound like its clipping, it isn't? Even though the DAW on-screen is 'saying' its gone over 0dB?

 

[mattr]

Internally, no. By definition the signal is not being clipped - the peaks that exceed 0dbfs are not being 'clipped' off.

If you so wish to you can let individual tracks and busses 'clip' as much as you like, though there is really no need to mix like this and if you often find yourself running out of headroom when mixing then it might indicate you are tracking too hot, etc. One or two tracks being pushed up for convenience is no problem, but if you find yourself with everything up high then you have no excuse not to just pull everything down.

But you mustn't let the master bus peak over 0dbfs (or any send to a hardware output / source being used for a mixdown... e.g. Sonar lets you mixdown individual tracks busses) as anything over 0dbfs will clip once expressed as fixed-point values.

 

[RAMI]

Thats an amazing relief! I kind of understand the whole integer thing, I'll definitely do some research on it. So basically if doesn't sound like its clipping, it isn't? Even though the DAW on-screen is 'saying' its gone over 0dB?

I'll let Mattr or someone else that knows more than me on that particular question answer it.

But, just as a side-note; To not even have to worry about it, why don't you just turn the buss down so it's not peaking over -3db ( or -6db, or even -10db for that matter)? Of course you'll then have to turn everything else down, too. But, so what?

 

[SouthSIDE Glen]

The problem with counting on floating point to save your butt with clipping is that chances are your final product - e.g. CD or MP3 - is not going to have the luxury of floating point math to save you from clipping, so you'd still need to throttle back that 2mix buss to save yourself from clipping downstream.

Additionally, there is another factor potentially involved here. The "clip" indicator does not mean exactly the same thing from editor to editor. Some software will light up the clip indicator if you have only one sample that clips. Others require anywhere from 3 to 8 consecutive clipped samples before thy light up the clip indicator. The reason for this is because of of a lack of standard agreement as to which it's more important to show. The basis of that disagreement is the fact that most human ears can't hear a clipped transient that is only one or two or perhaps even three samples long.

When you consider that even if you're working at 44.1k - the slowest standard digital sample rate - one sample represents a total elapsed time of about 0.00002 of one second, a length of time for which even severe clipping would likely be inaudible.

In fact - technically speaking - one cannot even verify that a waveform has been clipped unless/until it's at least 3 samples in length (that's the only way to draw a confirmed "flattiop" clipped peak.) But even then, we're only talking a transient that is about 0.00007 seconds long, which is still very hard to hear.

I don't know how Logic 9's clip indicator is programmed in that regard, but the explanation should indicate that just because one has clipping doesn't always mean that by necessity that one can hear it. But just like with the floating point thang, that doesn't mean that one can or should ignore clipping. Because first of all, even if you can't hear it, someone else might, and secondly, your analog gear (e.g. your amplifiers and speakers) may not be as tolerant of it as you are.

G.

 

[MarkyC]

I'll let Mattr or someone else that knows more than me on that particular question answer it.

But, just as a side-note; To not even have to worry about it, why don't you just turn the buss down so it's not peaking over -3db ( or -6db, or even -10db for that matter)? Of course you'll then have to turn everything else down, too. But, so what?

I understand where your coming from, but for me it feels like it loses presence, Of course after that it will go to mastering; normalising, more compression, limiting etc. I can easily find that the song is too quite or isn't and has lost its dynamic qualities.

I understand what your saying, and its partly my ignorance and moving to a new DAW. I always used to use Sonar 8, my busses always clipped so i re-balanced the levels so it didn't, but not hearing that the busses clipped on logic, even tho it said it did confused me and i thought id double check

 

[Waltz Mastering]

I understand where your coming from, but for me it feels like it loses presence, Of course after that it will go to mastering; normalising, more compression, limiting etc. I can easily find that the song is too quite or isn't and has lost its dynamic qualities.

I understand what your saying, and its partly my ignorance and moving to a new DAW. I always used to use Sonar 8, my busses always clipped so i re-balanced the levels so it didn't, but not hearing that the busses clipped on logic, even tho it said it did confused me and i thought id double check

Clipping is also cumulative, meaning every step down stream will magnify the original clip. It sounds worse the farther down the line you go.