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Author Topic: M/S Processing for non m/s sources  (Read 2913 times)

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Offline kuba e

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Re: M/S Processing for non m/s sources
« Reply #15 on: October 19, 2018, 03:54:49 AM »
Not sure I follow. Is this something you notice this when doing Left/Right equalization?  If not, it's not something you will notice when doing Mid/Side (sum/difference) equalization.

Gutbucket, thanks for the answers. I am sorry I asked inaccurately. Just to be sure. E.g.: if we have spaced pair of mics and we sum both channels to mono track, phase cancellation will happen in the resulting mono track (you explained why in the second paragraph).  If I do some Mid/Side manipulation for spaced pair mics, there will be no phase cancellation in the resulting Left/Right tracks?

^If I’m understanding that correctly, that explains why my first attempts at pseudo-MS processing showed peaks of around +3 dB from the low end (maybe to around 200 Hz) and the side around 0 dB (though now that I'm writing this I'm not sure what the reference dB is).

Ycoop, I think it means that the bass is placed in the center of stereo playback. If you try to amplify the bass in the Side channel and weaken bass in the Mid channel, the recording may be more spacious and maybe even clearer. But I do not have experience with it, it will be better for others to advise you.
« Last Edit: October 19, 2018, 03:57:53 AM by kuba e »

Offline ycoop

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Re: M/S Processing for non m/s sources
« Reply #16 on: October 19, 2018, 05:48:48 AM »
Not sure I follow. Is this something you notice this when doing Left/Right equalization?  If not, it's not something you will notice when doing Mid/Side (sum/difference) equalization.  The best practical answer I can give is to listen carefully when you make the adjustment to determine if it is doing anything other than what you want.

Standard (minimum-phase) EQ causes some degree of phase shift which is confined to the EQ'd region.  And as I understand it, the amount of phase shift depends on the gain and Q of the filter.  However, you are unlikely to hear that as cancellation per se.


With regards to spaced microphones and the phase-relationship between channels-
For direct sound arriving along the plane perpendicular to an imaginary line between the microphones, the content in both channels will be coherent and in-phase across the full frequency range. For direct sound arriving from off-axis, and for diffuse/reverberant sound which arrives essentially from all directions equally, the content is in-phase at the lowest frequencies and transitions to increasing degrees phase shift as frequency increases, becoming essentially randomized once the degree of phase shift exceeds 180 degrees.  The frequency at which this trend begins to occur is determined by the spacing between the microphones and the angle of arrival.  This applies to any spaced pair, a near-spaced directional pair of microphones as well as a wide-spaced pair of omnis, the difference between the two being the corner frequency at which that begins to occur, which will be lower for wide-spaced omnis, and considerably higher for a near-spaced pair.  Either way, the sum of the two channels (Mid) favors the in-phase components and the difference of the two channels (Side) favors the randomized phase components.

Looking back at this last paragraph again and trying to apply it to the EQ and mixing of the pseudo-MS channels that I made for a recent recording of mine that came out with muddy bass and distant sounding mids. Did all this in Reaper. Duplicated the original track and applied the Voxengo MSED plugin to each channel. One channel I set at -24 dB for Mid and the other channel I set as -24 dB side to create individual tracks for mid and side. I then applied the "mud free" preset from the RealEQ plugin on the side channel (which is essentially a high pass set around 150 Hz and band filters at around 300 and 600 Hz with a slight but wide band filter at around 6000 Hz). I further increased the Side track by 2 dB. I think the end result maintains spaciousness and the low end while still bringing out the mids, overall making the recording sound less like there's a thick blanket on top of it.

Doing a lot of work right now trying to wrap my mind around this. Am I correct in thinking that the lower frequency sound that makes it to either channel and is processed as "side" would be more reverberant? So while there's less bass present in the side component, the bass that is present is muddier.
Mics: Avantone CK-1s, CA-14 omnis
Pres: CA9100
Recorders: DR-60d mkII, DR-22wl, DR-07

Offline noahbickart

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Re: M/S Processing for non m/s sources
« Reply #17 on: October 19, 2018, 09:21:45 AM »
Duplicated the original track and applied the Voxengo MSED plugin to each channel. One channel I set at -24 dB for Mid and the other channel I set as -24 dB side to create individual tracks for mid and side. I then applied the "mud free" preset from the RealEQ plugin on the side channel (which is essentially a high pass set around 150 Hz and band filters at around 300 and 600 Hz with a slight but wide band filter at around 6000 Hz). I further increased the Side track by 2 dB. I think the end result maintains spaciousness and the low end while still bringing out the mids, overall making the recording sound less like there's a thick blanket on top of it.

Can I suggest an easier workflow?

Use MSED in the "thru" mode- you can adjust M/S on the fly.

For different eq on M and S, just use an EQ plugin which allow for different curves for M and S.

Here's a good free parametric:
https://www.ikmultimedia.com/products/trclasseq/

If you prefer a free graphic, the same folks who do MSED make this:
https://www.voxengo.com/product/marvelgeq/

I find the toneboosters eq to be really easy to work with and is only ~$35:
https://www.toneboosters.com/tb_equalizer_v4.html
« Last Edit: October 19, 2018, 09:56:14 AM by noahbickart »
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Schoeps VMS 02iub, Naiant Littlebox, Naiant IPA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10

Home Playback: Mytek DSD 192> McIntosh MC162> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-4XX / Beyerdynamic DT880

Office Playback: Grace m903> AKG k701 / Hifiman HE-400

Offline Gutbucket

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Re: M/S Processing for non m/s sources
« Reply #18 on: October 19, 2018, 10:20:18 AM »
Am I correct in thinking that the lower frequency sound that makes it to either channel and is processed as "side" would be more reverberant? So while there's less bass present in the side component, the bass that is present is muddier.

Yes, the Side channel will contain more reverberant content.  Not just at low frequencies but across all frequencies.  The Mid channel has reverberant content as well, yet has a higher proportion of direct sound so it will usually sound less reverberant.  And yes there will usually be less very low frequency content in the Side channel

I like approaching each aspect separately, using a tool like MSED in "tru" mode for overall stereo width adjustment, and using a Mid/Side EQ for adjusting the timbre of the direct center-image sound versus the more ambient wide sound.

But a Mid/Side EQ can also be used to adjust width (and to some degree reverberance) by frequency range without changing the overall tone by applying inverse (mirror image) EQ curves to Mid and Side, boosting where the other cuts and vice-versa.  The EQ plugins Noah points to can be used to do that, although you'll probably need to dial in both the original curve on one channel and its inverse on the other yourself.   No unlikely that you might want to adjust both width and tone, but this approach allows you to separate the two.

Does anyone know of a Mid/Side EQ that has an "inverse curve" mode which automatically creates an inverse curve in the second channel?  That would be very useful for this as one could adjust width by frequency with gain being automatically compensated, separating the width/rebererance adjustments from the tonal adjustments.
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Offline Gutbucket

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Re: M/S Processing for non m/s sources
« Reply #19 on: October 19, 2018, 10:40:29 AM »
if we have spaced pair of mics and we sum both channels to mono track, phase cancellation will happen in the resulting mono track (you explained why in the second paragraph).  If I do some Mid/Side manipulation for spaced pair mics, there will be no phase cancellation in the resulting Left/Right tracks?

Might be, but I don't worry about it much unless it presents an obvious problem.

There is no cancellation from simply converting from L/R to M/S and back to L/R again (that's is how FM radio works), but there will be some if you manipulate the M/S ratio in the middle before converting back to L/R again as we are talking about here.  Does it matter?  Your ears will tell you if it does or not.  Usually we're making minor width tweaks which won't stir this kind of thing up too much.  Also, consider that any spaced-microphone configuration will already have phase cancellation combing stuff going on as described above, and doing this mostly serves to shift the combining which is already present around, as much or more so than making it stronger or weaker.  In a way, it's sort of like re-adjusting the distance between the microphones.  Technically it is not the same, but practically it is similar.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline kuba e

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Re: M/S Processing for non m/s sources
« Reply #20 on: October 20, 2018, 06:26:03 AM »
Thanks GB. I understand. And thanks to all specially to Noah for pointing out this. Mid/Side eq or stereo manipulation looks like good tool for tapers. It helped me with one of my recording. The recording needed a lot of boost of bass. When I did standard eq, it started to sound muddy. So I used only limited bass gain. Now I added additional bass gain only to Mid. It works great, the recording has the required bass and still sounds clear.
« Last Edit: October 20, 2018, 06:31:59 AM by kuba e »

Offline kuba e

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Re: M/S Processing for non m/s sources
« Reply #21 on: October 20, 2018, 07:00:28 AM »
Ycoop, I think it means that the bass is placed in the center of stereo playback. If you try to amplify the bass in the Side channel and weaken bass in the Mid channel, the recording may be more spacious and maybe even clearer. But I do not have experience with it, it will be better for others to advise you.

I wrote this probably wrong. If the Mid channel is high it should mean that the sound is narrow in stereo playback. But it does not have to be placed in the middle of the stereo playback, it can be on the left or on the right side. On the other hand. If the Side channel is high it should mean that the sound is wide in stereo playback. And it does not mean the placement in stereo playback.
« Last Edit: October 20, 2018, 07:45:13 AM by kuba e »

Offline wforwumbo

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Re: M/S Processing for non m/s sources
« Reply #22 on: October 20, 2018, 02:38:11 PM »
Just to follow up on this thread...

After Noah mentioned to me his m/s processing on Tuesday’s Phish show (Albany n1), I experimented with it a little bit pre-show Wednesday. I arrived at the conclusion that using MSED and dropping the side just a touch (depending on what I wanted to listen for, I’d vary from -1.5 to -4.5 dB) really helped to strengthen the overall tape. I lost some immersion even just by raw m/s encoding and phase interactions, but I gained a bit of soundstage and image stability, plus I was able to clear out some of the fairly overwhelming room reverberance (TUC is a highly echoic and boomy room). I found this really helped the tape, and actually I applied it to my 16/44.1 masters that I uploaded after Wednesday’s show - I will leave my 24/96 masters untouched re: m/s, but for 16-bit that I knew was going to be first to the draw (and thus widely listened to) I thought it would sound better to the masses listening on their iPhone earbuds and on streaming services.

This has admittedly gotten me to totally rethink how I tape, and what possible coincident and spaced pairs I want to eventually build my rig with...
2x Schoeps mk21 (matched pair) -> nbob KCY -> Naiant PFA -> Sound Devices Mixpre 6

Offline noahbickart

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Re: M/S Processing for non m/s sources
« Reply #23 on: October 21, 2018, 02:10:33 AM »
I can't recommend the Klanghelm VUMT deluxe enough.

https://klanghelm.com/contents/products/VUMTdeluxe/VUMTdeluxe.php

I find it much more precise than the MSED. The metering and gain options are really useful for lots of other applications as well. It's only 22 Euro for the deluxe.
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Schoeps VMS 02iub, Naiant Littlebox, Naiant IPA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10

Home Playback: Mytek DSD 192> McIntosh MC162> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-4XX / Beyerdynamic DT880

Office Playback: Grace m903> AKG k701 / Hifiman HE-400

Offline Ronmac

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Re: M/S Processing for non m/s sources
« Reply #24 on: October 21, 2018, 06:44:52 AM »
^^^ +1

VUMT sits as the first plugin on each track in my studio projects to insure proper levels prior to any processing.

Simple, elegant and extremely useful. Oh, and it is dirt cheap, as well.

I use the Brainworx  BX Digital EQ3 for my deep-dive EQ and MS needs.

https://www.brainworx.audio/products/brainworx/bx-digital-v3.html

Offline kuba e

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Re: M/S Processing for non m/s sources
« Reply #25 on: October 23, 2018, 12:41:33 PM »
Maybe it's also worth trying a linear eq when doing M/S eq. I played with one recording and the linear eq was little better. It could bring a less phase smearing.
« Last Edit: October 23, 2018, 12:46:30 PM by kuba e »

Offline Gutbucket

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Re: M/S Processing for non m/s sources
« Reply #26 on: October 23, 2018, 03:09:31 PM »
Makes sense.  Similarity, for recordings that are made with a Mid/Side microphone arrangement, tweaking time alignment of the Mid channel against the Side channel by a few samples either way can correct for less than perfect microphone coincidence and make an audible improvement.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline noahbickart

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Re: M/S Processing for non m/s sources
« Reply #27 on: October 23, 2018, 03:35:54 PM »
Similarity, for recordings that are made with a Mid/Side microphone arrangement, tweaking time alignment of the Mid channel against the Side channel by a few samples either way can correct for less than perfect microphone coincidence and make an audible improvement.

How, if at all, does adjusting the time affect phase?

This is one of those philosophical audio questions I've been pondering for years. wforwumbo tries to answer this with equations and logical QED style proofs that lose me. I'm a religion professor after all....
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Schoeps VMS 02iub, Naiant Littlebox, Naiant IPA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10

Home Playback: Mytek DSD 192> McIntosh MC162> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-4XX / Beyerdynamic DT880

Office Playback: Grace m903> AKG k701 / Hifiman HE-400

Offline Gutbucket

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Re: M/S Processing for non m/s sources
« Reply #28 on: October 23, 2018, 04:49:15 PM »
Easiest way to think of it is like aligning an AUD and SBD, just to a much finer degree.  By shifting the timing of one channel against the other you shift the alignment of one waveform against the other.  We enter the phase-alignment realm rather than the time-of-arrival realm when such a shift gets things closer than one wavelength at the frequency in question.

In the case of an AUD + SBD mics which are a number of meters distant from each other, the alignment difference is one of milliseconds and therefore in the time-of-arrival perceptual realm.  In the case of a Mid/Side pair of microphones which has an imperfect coincidence better measured in millimeters, the difference is going to be one of microseconds (µs), which is probably a few hundred samples either way.

Sound travels approximately 1 mm in 300µs.  The time difference between samples at 44.1kHz is 22.7µs.  So 13 samples (at 44.1kHz) ~= 1mm.  A misalignment of say 1cm would equate to about 130 samples.

That gives you an idea of the scope of it, but since we probably don't know exactly how far the capsules might have been be out of misalignment, just listen very carefully if adjusting and see if it makes any audible difference.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline noahbickart

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Re: M/S Processing for non m/s sources
« Reply #29 on: October 24, 2018, 03:25:46 PM »
this might be interesting to people looking for an all in one M/S EQ:

https://www.soundonsound.com/news/internet-co-release-free-ms-eq-comp-plug
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Schoeps VMS 02iub, Naiant Littlebox, Naiant IPA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10

Home Playback: Mytek DSD 192> McIntosh MC162> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-4XX / Beyerdynamic DT880

Office Playback: Grace m903> AKG k701 / Hifiman HE-400

 

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