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2 Mid-Side questions

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2 Mid-Side questions

Postby ManFromGlass » Fri Mar 27, 2020 1:26 pm

I’m about to try mid-side recording and have some fun with it. I have 2 questions -

If I use a ribbon mic for the side should I be concerned about the slight frequency difference between the back and front of the ribbon? It’s a Royer R-122 mkll.

I’ve had a quick play with the free MSED plugin on a normal stereo track. The presets change the sound, not in a bad way, just different. Could there be a time when this could be useful on a track? In case I’m buggering something up I would do a check in mono.

Thanks.
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Re: 2 Mid-Side questions

Postby Hugh Robjohns » Fri Mar 27, 2020 1:57 pm

ManFromGlass wrote:If I use a ribbon mic for the side should I be concerned about the slight frequency difference between the back and front of the ribbon? It’s a Royer R-122 mkll.

You're having fun, so no need for concern... use it as a learning experience.

Theoretically, having a different response front/back (or side/side as it will be) on the Sides mic means that the stereo imaging from the decoded MS array will be slightly non-linear and frequency-dependent across the full left-right width. In other words, the spatial positions of sources across the sound stage will be 'misreported', and sources on the darker side of the MS array will appear closer to the centre of the decoded stereo image than those on the brighter side.

Whether you can hear that depends on the bandwidths of the sources, the extent of the mic's frequency imbalance, and the precision of your stereo monitoring. In all likelihood, it will be in the range of not noticeable at all, down to noticeable but not really disturbing...

It would really only be a concern if the Side mic's response is significantly different front/back or if precise stereo imaging is critical.

Could there be a time when this could be useful on a track? In case I’m buggering something up I would do a check in mono.

Yes, if you have a stereo track that would benefit from some extra width or narrowing. The latter can be very useful in combination with the pan/balance control so you can narrow a stereo source and then move it around the sound stage -- eg. for positioning a stereo keyboard to occupy L-C rather than L-R.

The only real danger with MS processing is to widen the signal too much, which will result in an unpleasant phasey or 'hole in the middle' effect in stereo and a noticeably weakened contribution to the summed mono mix.
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Re: 2 Mid-Side questions

Postby blinddrew » Fri Mar 27, 2020 2:46 pm

Zukan / Eddie Bazil had an article on creative uses of mid-side in a recent issue. Maybe the February issue? Definitely worth a read if you fancy a play. :thumbup:
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Re: 2 Mid-Side questions

Postby ManFromGlass » Fri Mar 27, 2020 4:59 pm

That was next on my to-read list!
And Hugh has a double MS article from 2017.
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Re: 2 Mid-Side questions

Postby Hugh Robjohns » Fri Mar 27, 2020 5:07 pm

Double-MS is just an extension that's often used for simple surround sound recording in the field, but can be applied in some music-recording applications as that article explains...

But I'd get on top of basic MS first before doubling up on Mid mics and decoders!

Of course, once you've cracked MS and Double-MS, it's only a small step further to first-order Ambisonics... and then high-order Ambisonics... and then your PhD and Professorship... :ugeek:
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Re: 2 Mid-Side questions

Postby ManFromGlass » Fri Mar 27, 2020 10:18 pm

Heck, I’ll just jump ahead to Grand Imperial Wazoo of the 7th Dimension of Sound! :geek:

Do you think the pay is good? :think:
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Re: 2 Mid-Side questions

Postby Hugh Robjohns » Fri Mar 27, 2020 10:43 pm

Not right now... :lol:
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Re: 2 Mid-Side questions

Postby ManFromGlass » Sat Mar 28, 2020 1:26 pm

Update - great bloody fun!
I’m following Eddie’s article too. I might need to buy the Pro Q3 adaptive eq now. Brilliant how it lets one use mid or side as a sidechain trigger. I think that’s what it does, not being able to try it yet.
One quirk with Logic - panning the Side track (after creating 2 separate tracks - 1 for Mid, 1 for Side and sending the main file to no output ) moves the sound in the opposite direction of the pan knob.
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Re: 2 Mid-Side questions

Postby Hugh Robjohns » Sat Mar 28, 2020 2:31 pm

ManFromGlass wrote:One quirk with Logic - panning the Side track (after creating 2 separate tracks - 1 for Mid, 1 for Side and sending the main file to no output ) moves the sound in the opposite direction of the pan knob.

You're going to have to detail precisely what you've set up there if we are to stand a chance of figuring this out...

...but in genreal, things appearing to go the wrong way left-right is usually because there's a polarity inversion in one or other of the the original Mid or Side signals (or mics).
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Re: 2 Mid-Side questions

Postby ManFromGlass » Sun Mar 29, 2020 2:35 am

So after a bit of exploration I have may have found the issue but I don’t understand it.
As per the SOS article I ended up with 2 tracks in Logic, 1 for mid, 1 for side. In Logic there are 3 choices for your panner - Stereo Pan, Balance (the default) and Binaural Pan.

For some reason I switched the Side track to Stereo Pan and I was playing with narrowing the stereo field. In Stereo Pan the panning reverses - fully clockwise moves the sound to the left, but only on the Side track. Stereo Pan on the Mid track works in the expected direction, fully clockwise = panned right. The default choice of Balance works as to be expected on Mid and Side.

Both mic pres phases are set to normal. MSED correlometers show far right for the Mid track and far left for the Side track. Is there more information I can provide?
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Re: 2 Mid-Side questions

Postby John Willett » Sun Mar 29, 2020 9:41 am

The best read on MS is this article by Dooley and Streicher. :thumbup:

I found this invaluable when I started working with MS. :thumbup:
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Re: 2 Mid-Side questions

Postby Hugh Robjohns » Sun Mar 29, 2020 12:22 pm

ManFromGlass wrote:As per the SOS article I ended up with 2 tracks in Logic, 1 for mid, 1 for side. In Logic there are 3 choices for your panner - Stereo Pan, Balance (the default) and Binaural Pan.

I'm not a Logic user and so not familiar with the panning options and therefore I'm not sure what's going on here... But rule 1 of Mid-Sides processing is that panning is something that happens in the Left-Right domain, not the Mid-Sides domain.

So you need to run those Mid and Side source signals into a stereo track, and then drop an MS decoder into the insert of that stereo track -- the Voxengo MSED is very good, but I know Logic has its own simpler, native decoder -- before you do anything else at all. Messing about with panning the raw Mid/Side signals will just mess up the maths in the decoder and do all kinds of weird things to the imaging.

You can think of the MS decoder as creating a 'virtual XY stereo mic' from the MS source. As you change the ratio of Mid to Side you change the mutual angle of the XY mics. As you change the Mid polar pattern you also change the polar patterns of the XY mics.

But if you start panning the Mid mic (or Side Mic) the virtual XY mics have different sensitivities (so different sized polar patterns, in effect) or even different polar patternjs left/right, so the whole image becomes lop-sided in rather strange and unintuitive ways!
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Re: 2 Mid-Side questions

Postby ManFromGlass » Sun Mar 29, 2020 12:43 pm

Thanks All. I’m liking this rabbit hole - another cool tool in the toolbox!
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