distortion without clipping

Dr Shock

New member
I was involved in a mastering session with a reputable
engineer whom I have worked with on many occasions He is a 20 year pro and has done a lot of good work.

The tracks involved were 2 electric guitars, blues harp and vocals. Nice bluesy kind of material.

We used Pro Tools with all the plug ins inclucing Waves L2
Monitored mostly on Yamaha NS 10's but had Genelecs,
and boom box speakers for reference. He likes the NS 10's
because he feels they transfer best, and is also used to them. We monitored the session at about 80-85 db for the most part. At times he would use the phones briefly .

One of the 2 guitars was carrying the bottom, whether it be low chords with single note bass runs, or upright bass type walking lines. Very deep and dark.

Everything sounded fantastic in the mastering suite, but when I got in my car to drive home...with a Burn of the session, I noticed that as I increased the gain , it started to distort...in fact when I cranked my car system up fairly
but not overly loud, it was really distorting. We never really cranked it up in the mastering suite. The music is such that the listener would probably not push the volume too much, but none the less , the desire to have it sound clean at all levels is the ultimate goal.

I checked out the waveforms in Cool Edit pro and they were on the hot side, but not clipping anywhere. Does anyone have any thoughts as to how or why this situation occurred.

He used a multi band compressor to clean up some of the lower frequencies, but the original tracks were already nice and warm. the compression used was very gentle...the original tracks did not really need too much work. The EQ used was very subtle.

As it ends up I have a mastered product that sounds good at below 90 -95 db , but above that , it starts getting harsh and distorted. Any thoughts on how this happened would be greatly appreciated

Dr Shock
 
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Just a guess but I'm wondering if you got bit by the digital summing distortion that crops up if you mix down to high audio levels. For whatever reason most digital systems absolutely suck when mixing down.

Maybe its not that, but I've had that happen before.

Really common if you over normalize tracks prior to mixdown or use way too much hard limiting during the master.
 
Cloneboy Studio said:
Just a guess but I'm wondering if you got bit by the digital summing distortion that crops up if you mix down to high audio levels. For whatever reason most digital systems absolutely suck when mixing down.

Maybe its not that, but I've had that happen before.

Really common if you over normalize tracks prior to mixdown or use way too much hard limiting during the master.

This should only happen if you're not observing proper gain staging.

For example, if the ME was boosting a frequency in one of the Wave EQs that caused overs, but then reduced the volume later in the L2 (or track) to be below 0dBFS. The clipping/distortion already happened before you would get an indication in the final stage (or summing bus).

What do you mean by "he used the L2 to clean up the lower frequncies"? Was it the L2 or a multi-band compressor?
 
he used a multi band compressor for the low EQ frequencies. The original tracks were recorded on a blackface ADAT ..... compression was not used during tracking and as a result, conservative levels were used to avoid any chance of digital clipping. During the digital
mixdown ( in Cool Edit Pro ) , as much as 7 db of gain
was used on the stereo bus in order to get the mixdown
to a level of where he said was good to master. He wanted the mix between -3 to -5 db. Would the increase of gain to the stereo bus right before the digital mix create this problem

thanks
 
Dr Shock said:
he used a multi band compressor for the low EQ frequencies. The original tracks were recorded on a blackface ADAT ..... compression was not used during tracking and as a result, conservative levels were used to avoid any chance of digital clipping. During the digital
mixdown ( in Cool Edit Pro ) , as much as 7 db of gain
was used on the stereo bus in order to get the mixdown
to a level of where he said was good to master. He wanted the mix between -3 to -5 db. Would the increase of gain to the stereo bus right before the digital mix create this problem

thanks

I'm assuming you mean -3 to -5 db peak? If this represents an RMS level then it definitely could cause distortion.

If all you had done to the mix was raise the level of the main bus, why couldn't the ME do this? In fact it would be better if did so that the audio only went through this processing once, rather than on your end, and a second time when he was adjusting levels from the output of the EQ, compressors, or any other type of processing.

Thinking through this process, if you recorded the ADATs at conservative levels (no overs) then there should not be any distortion from there. How were the tracks brought into cool edit for mixing, or did you mix to cool edit from the ADATs and an analog board?
 
You are assuming correctly...-3 to-5 db Peak

The original ADAT levels which peaked around -15db were brought into Cool Edit Pro via lightpipe into
RME Hammerfall 96/52 soundcard.

I then did the mixdown in Cool Edit Pro at those lower levels...the mix sounded good . It was at that point that I raised the levels on the stereo buss and did the digital stereo mixdown

thanks for your insight Tom
 
Dr Shock said:
You are assuming correctly...-3 to-5 db Peak

The original ADAT levels which peaked around -15db were brought into Cool Edit Pro via lightpipe into
RME Hammerfall 96/52 soundcard.

I then did the mixdown in Cool Edit Pro at those lower levels...the mix sounded good . It was at that point that I raised the levels on the stereo buss and did the digital stereo mixdown

thanks for your insight Tom

It doesn't sound like there would have been any issue with distortion on your end due to gain. In fact more the opposite, recording to the ADATs a bit hotter wouldn't hurt, but I understand your reasons.

It would help to hear a sample of the material before/after mastering. Or if you would like to contact me off the board feel free.
 
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