Rumble filter + limiter used AFTER mastering?

[Axon]

I have a bit of a forensic question for y'all.

Has anybody ever heard of taking an already-finished (and already-clipped!) digital master, highpassing at ~20hz, and then re-clipping the waveform to make a new master? Not even applying any more gain - just a highpass and a clip?

Are there any reasons somebody would want to do that? Or are there plausible situations where that would wind up happening for a reissue, like say if the master had to go through another analog stage, which happened to have a DC rolloff?

[Edward_Vinatea]

Originally Posted by Axon

Are there any reasons somebody would want to do that?

IME the only reason you may want to do this to a master is when there is too much density at the bottom end. I realize that sounds too simple. And, the chances that the low cut filter needs to be exactly at 20Hz are kind of small as settings are not usually done arbitrarily.

Regards,

[Axon]

Here's the punchline to my question, FWIW.

Despite no documentation, there are at least two separate masterings of Pearl Jam's LP "Vs." floating around... One of the masters was highpassed at around 40hz, with the resulting digital overs clipped, to generate the new master. Such a master suffers from both reduced bass and greater amounts of clipping.

I still don't know why anybody would do this deliberately. Or for that matter, how it could be done be accident.

[Edward_Vinatea]

Originally Posted by Axon

Here's the punchline to my question, FWIW.


I still don't know why anybody would do this deliberately. Or for that matter, how it could be done be accident.

First of all, I don't see on "pic 1" the statement: "At 20hz the masterings differ by 12db". The pic actually shows almost no difference between A and B at what appears to be the 20 Hz freq. position. The most I see is a clear 6dB difference at around 3 maybe 5Hz, which is ridiculous in itself because is way at the bottom of the range. Regardless, that particular 60 sec snapshot of the A/B is way too subliminal, you'd need dead accurate speakers and a good room to listen..erhm...feel it (if it's even possible to be heard). As far as clipping goes {Pic 2} it's NOT uncommon and it's actually found more often than not in many commercial releases. Again, it's not that important if the sound is good and the clip is not correlating to the sound of distortion.

Regards,

[Axon]

Sorry - pic 1 is a ratio of frequency spectrum (an estimated transfer function) - not a plot of spectrum plots of separate samples. The two plots shown in the pic are for the L+R and L-R channels. So the fact that the plots at 20hz are at -12db means that one master is 12db down from the other at 20hz.

I'm not disputing that the added clipping may not be audible - I didn't even try to ABX it. But the fact that it's even happening - for such a strange reason - is worth noting.

[Edward_Vinatea]

Originally Posted by Axon

Sorry - pic 1 is a ratio of frequency spectrum (an estimated transfer function) - not a plot of spectrum plots of separate samples. .

Ok, no problem. But then, shouldn't both masters' spectrums be shown?

[Axon]

I computed the plot with some hand-rolled code that averages the ratio of the windowed spectrum responses. So the original spectra of each master doesn't actually exist as a final output - only the ratio.

[Adam Dempsey]

The horizontal axis of graph 1 is labeled "Time" (with no units given) not, as you've said, "frequency in hz" (sic).
And are you saying now that channel "A" (black) = L+R and "B" (red) = L-R?

Also, graph 2 seems to contradict your contention: the final version appears less clipped than the original.

In any case, a reissue could be from a new master perhaps imported to a workstation with a default DC filter in the background, hence also some clipping. You've implied that there's no extra gain... Is the reissue noticeably (ie, audibly) different?

[Axon]

Originally Posted by Boomshanka

The horizontal axis of graph 1 is labeled "Time" (with no units given) not, as you've said, "frequency in hz" (sic).
And are you saying now that channel "A" (black) = L+R and "B" (red) = L-R?

Doh. I had adapted this analysis code from another program and forgot to correct the axes etc. Yes, for the first pic, the black plot = L+R and the red plot = L-R. But in pic 2, both plots are the left channel only (just between the two masters). In hindsight the sum/diff work was unnecessary and should be removed.

I'll redo the pics sometime soon with better axis descriptions and captions.

Also, graph 2 seems to contradict your contention: the final version appears less clipped than the original.

Well, as per the update, neither greynol nor I really know anymore which master is which: all we know is that some masters have different levels of bass energy and different levels of clipping than others. Again, "Orig" and "Final" are probably not good axis descriptors here and they should be changed. Just think of them as A/B.

In any case, a reissue could be from a new master perhaps imported to a workstation with a default DC filter in the background, hence also some clipping. You've implied that there's no extra gain... Is the reissue noticeably (ie, audibly) different?

Nobody's tried to find out yet.

[jayfrigo]

Originally Posted by Axon

I have a bit of a forensic question for y'all.

Has anybody ever heard of taking an already-finished (and already-clipped!) digital master, highpassing at ~20hz, and then re-clipping the waveform to make a new master? Not even applying any more gain - just a highpass and a clip?

Are there any reasons somebody would want to do that? Or are there plausible situations where that would wind up happening for a reissue, like say if the master had to go through another analog stage, which happened to have a DC rolloff?

Filter side-effects like ripple can cause overs if you high-pass something that is already reaching full scale. That said, I haven't personally heard of this being done for a reissue.

[scraggs]

i checked out my copy and it looks like the first one, straight flat tops. doesn't sound lacking in low end at all. i was surprised to see how loud it was. pretty cranked for 1993! no mastering credit, anyone know who did it? i am going to go out on a limb and guess bob ludwig...because his name seems to turn up on almost everything...