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Phase correlation question

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Phase correlation question

Postby Demious » Thu Jul 30, 2020 2:40 pm

I was taught to always make sure I don't have any phase correlation issues on tracks, or in a mix, so there won't be any issues when switching to mono. I know quite a few mixers that switch between mono and stereo during mixing, to check if all sounds have enough space in the frequency spectrum and aren't fighting each other, as well as for the purpose of being compatible with mono devices people use to listen to music, like small radios, phones, or tablets. I remember several videos that were posted quite recently, where was said that there still are plenty of mono devices in use, to not neglect this principle.
However, I was having trouble with a virtual instrument that shows some serious phase correlation issues, when I measure the produced sound, but the publisher told me this is normal, because mono is something from the past and is not at all relevant anymore. They claim that there are no more devices in use that are mono. I don't know anything about phones and tablets, but I was under the impression there are still models that have only one speaker. And the first thing that came to mind about the use of a phone with 2 speakers, people amplify the sound by putting the phone in a glass, or something comparable and I'd think that the result of the sound in the room would be turned into mono as well.

Is it really so that mono is not in use anymore? That would make me wonder about mono monitoring functions on loads of mixing tools. So many plugin still have mono monitoring functions, monitor controllers have, and let's not forget about the DAW itself.

Is it really so that there are no mono listening devices around? Is there a reason that checking your mix in mono isn't relevant anymore? Is it really so that we can ignore phase correlation completely, because mono is not of this time?

Could someone please shine some light on this matter for me?
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Re: Phase correlation question

Postby Hugh Robjohns » Thu Jul 30, 2020 2:50 pm

Demious wrote:I was taught to always make sure I don't have any phase correlation issues on tracks...

Quite right!

Although it's more about being aware of any phase correlation issues, and making informed decisions about any compromises necessary in optimising the sound for mono and stereo listeners. Phase correlations 'issues' are an inherent part of most stereo recordings... it's whether or not they cause problems that's important!

Demious wrote:, I was having trouble with a virtual instrument that shows some serious phase correlation issues, when I measure the produced sound, but the publisher told me this is normal, because mono is something from the past and is not at all relevant anymore. They claim that there are no more devices in use that are mono.

Shows how much he/she knows, then! :roll:

Some phones and tablets only have a single speaker, and many people listen to their phones via the glass trick, as you say, or from a distance so they are heard in mono anyway.

The world's best selling (allegedly!) DAB radio only has a single mono speaker. All FM stereo radios switch to mono automatically if the signal gets weak or there's interference -- often quite noticeable in a moving car! Many large PA systems are run in mono...

If he/she claims that mono isn't relevant, then there's an (equally feeble and erroneous) argument to say that stereo is no longer relevant either and he/she should be producing instruments with multichannel outputs instead!

But my advice is, whatever format you're using: Ignore downmix compatibility at your peril!

As for the virtual instrument thing, it is very common for the designers of instrument patches and presets to use lots of width-enhancing effects because they make the sound seem more exciting and big and spacious when auditioned on its own...

But in reality this kind of over-the-top sound design actually makes it so much harder to use those sounds in a mix as they tend to overpower other instruments. Consequently, you often end up having to switch off the effects or just take one channel and then process the sound more appropriately to make it fit in and sit nicely alongside everything else.
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Re: Phase correlation question

Postby Sam Spoons » Thu Jul 30, 2020 2:52 pm

I have several mono devices, iPhone 6S, Amazon Alexa, Bose Soundlink Revolve +, Bose S1 Pro, Pure DAB radio. Clearly this dev does not live in the real world if he thinks that mono is dead....
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Re: Phase correlation question

Postby Hugh Robjohns » Thu Jul 30, 2020 2:55 pm

It's also worth noting that a lot of stage keyboards are now provided with mono presets specifically because summing some of the stereo ones to mono on a big PA sounds terrible! The manufacturers wouldn't bother to go to the trouble of creating bespoke mono presets if mono was obsolete...
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Re: Phase correlation question

Postby Zukan » Thu Jul 30, 2020 3:23 pm

Let's not forget clubs....
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Re: Phase correlation question

Postby Demious » Thu Jul 30, 2020 4:04 pm

Thanks a whole bunch for all the info, guys! :)

This is pretty much the picture I had, but when someone is putting pressure on you, it sometimes is easy to start doubting yourself, at moments you don't have all the details at hand. But Im back on track, thanks!
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Re: Phase correlation question

Postby Hugh Robjohns » Thu Jul 30, 2020 4:13 pm

:thumbup:
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Re: Phase correlation question

Postby Hugh Robjohns » Thu Jul 30, 2020 4:19 pm

The bottom line is that if you take a stereo track and sum it to mono, it will always sound slightly different. That's inevitable. The balance between central and edge sounds will alter, and reverberation dries up a bit, for example.

So it is necessary to arrive at a compromise where the mono sounds acceptable, and the stereo sounds better. (Exactly the same principles apply to mixing in surround, too: the mono needs to sound acceptable, the stereo better, and the surround fantastic! ;-) )

What you don't want is for something to sound nasty and unpleasant, or drawing unwanted attention to itself when summed to mono -- as becoming heavily coloured or phasey, or obviously missing a lot of high end etc. That's not a compromise that most would be willing to accept, and in that situation a more radical solution would be required, such as finding a better-sounding stereo mic array, a different instrument preset or even a different instrument entirely, alternative effects settings or whatever...
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Re: Phase correlation question

Postby The Elf » Thu Jul 30, 2020 6:02 pm

A majority of family and friends now listen on 'smart speakers' - most of these are mono from what I can see.
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Re: Phase correlation question

Postby Hugh Robjohns » Thu Jul 30, 2020 9:07 pm

That's a very good point, and you're quite right. Everyone I know with Siri or Cortana smart speakers have just one in each area. Some of my friends with Sonos systems just have one in some rooms too...

So mono is very much alive and well and a lot more common than some want to admit! :D
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Re: Phase correlation question

Postby Rich Hanson » Fri Jul 31, 2020 10:59 am

Indeed. I am sat here at my work desk right now with my phone tethered to a mono bluetooth speaker. Obviously not my ideal listening environment, but I'm (supposed to be) working anyway.
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