Phase issue questions

[TBman]

1. How can you identify a phase issue. Can you actually hear it or does it just show up in your tools (which plug ins clearly identify the phase issue ?)

2. How can you fix a phase issue post recording?

3. Does the average listener even notice a phase issue? Does fixing it really make a difference? Can you provide examples?

[jim1960]

Originally Posted by TBman

1. How can you identify a phase issue. Can you actually hear it or does it just show up in your tools (which plug ins clearly identify the phase issue ?)

To my ears, phase issues do one of two things depending upon the severity of the phase issue... they'll make the recording sound thin or they'll impart a sort of flanger effect.

Originally Posted by TBman

2. How can you fix a phase issue post recording?

There are two plugins that address it very well. For solo guitar, there's no reason to buy the more expensive Pi. Auto-Align is excellent and the improvement will usually have you scratching your head wondering why you didn't hear how weak it sounded before.
SoundRadix Auto-Align
SoundRadix Pi
You can try both of these for free before deciding to purchase.

Originally Posted by TBman

3. Does the average listener even notice a phase issue? Does fixing it really make a difference? Can you provide examples?

That depends on the severity of the misalignment and the ears of the listener. To those who don't know about such things, they may hear it but not know they're hearing a problem in the audio. But the bottom line is that when your audio is out of phase, no one is hearing the best version of it (unless you're intentionally creating a phase issue for artistic purposes.).

[RRuskin]

Originally Posted by TBman

1. How can you identify a phase issue. Can you actually hear it or does it just show up in your tools (which plug ins clearly identify the phase issue ?)

2. How can you fix a phase issue post recording?

3. Does the average listener even notice a phase issue? Does fixing it really make a difference? Can you provide examples?

It can be heard, especially when you sum to mono. The sound will become hollow and in severe cases, almost disappear. Case in point, I heard a stereo pressing of Hendrix's "Are You Experienced" where Jimi's vocal went away when it was summed to mono. All that was left of it was the echo return.

One can rarely fix a mix that contains severely out of phase material. If however, one side is a full 180 degrees reversed from the other, reversing one of the sides will correct things. Otherwise, going back to the multitrack is the only way to go.

[KevWind]

Besides what Jim has said----- first understand it is a pretty complex subject

But in somewhat simplistic terms Here goes

The term Phase Issue essentially means a sound wave/s time alignment differences causing issues which can have different level of effect depending on how severe the misalignment is
Also understanding that time alignment differences can small enough to not really be an "issue"

Here are three examples

Here are two sound waves that are in phase



Here are two that have phase differences



And here are two that are 180 degrees out phase alignment and will cancel each other creating no sound





That said what we deal with in recording can be basically divided into two main categories

#1 Time differences when using two microphones on one source (recording stereo guitar with two or more mics for example )

#2 Reflections causing comb filtering issues (which is also a time difference issue

As far as #1 most common stereo mic'ing techniques done correctly will not cause severe "issues" because the are close enough to bing the same distance from the source that they simply create the stereo effect... But if you start increasing the any difference in their respective distances to the source (like say one mic @ 6 inches and one @ 12 inches you can start to encounter issues

#2 has to with the mic/s (mono or stereo) position/distance to the source AND the rooms reflection properties ( and why close mic'ing is often a suggestion ) AND why many here sound like broken records on suggestions of acoustic treatment.

For one fairly good example of how comb filtering sounds

Scroll down on this page to the soundcloud examples of "What comb filtering sounds like'

https://www.dpamicrophones.com/mic-u...ow-to-avoid-it

[jklotz]

I like this guys explanation and fix. It's in Logic Pro, but should be easily transferable to what ever DAW you are using:

[Doug Young]

Here's a quick demo for you Barry. I just faked this by manipulating an existing recording.

Here's 5 passes at the same little lick:

1. My initial spaced pair recording.

2. Flipping the polarity, aka 180 degrees out of phase on one channel - hear the sort of overly-dramatic stereo image?

3. Same as #2, but when summed to mono. Thin, muffled and quiet.

4. A lesser degree, a 90 degree phase shift on one channel. Doesn't sound so bad in stereo, kind of sounds "bigger", but with a slightly odd sound to it.

5. The 90 degree shift when summed to mono. Not as bad as #3, but you hear a muffled lifeless sound. This is the sort of sound I often notice when people post examples that were recorded with spaced pairs, but then panned inward, resulting in some phase cancellation.




BTW, here's what Blue Cat's stereo Scope looks like for these examples: (With this tool, the Y axis is volume, X axis is place in the stereo field, from far left to far right)

Spaced Pair stereo, Correlation around 0.7. (mono would be 1.0) This is a pretty wide stereo to start with, as you can see from the curves and correlation

Stereo OK.jpg

The flipped polarity. Notice how the sides are higher in level than the mid. correlation is -0.6

Polarity Inverted.jpg

and the 90 degrees off. Very wide stereo image, sides are as strong as the center. Correlation is a around -0.4

Stereo - 90 degrees out of phase.jpg

[TBman]

Thanks for the info everyone!

[AcousticDreams]

Originally Posted by Doug Young

Here's a quick demo for you Barry. I just faked this by manipulating an existing recording.

Here's 5 passes at the same little lick:

1. My initial spaced pair recording.

2. Flipping the polarity, aka 180 degrees out of phase on one channel - hear the sort of overly-dramatic stereo image?

3. Same as #2, but when summed to mono. Thin, muffled and quiet.

4. A lesser degree, a 90 degree phase shift on one channel. Doesn't sound so bad in stereo, kind of sounds "bigger", but with a slightly odd sound to it.

5. The 90 degree shift when summed to mono. Not as bad as #3, but you hear a muffled lifeless sound. This is the sort of sound I often notice when people post examples that were recorded with spaced pairs, but then panned inward, resulting in some phase cancellation.




BTW, here's what Blue Cat's stereo Scope looks like for these examples: (With this tool, the Y axis is volume, X axis is place in the stereo field, from far left to far right)

Spaced Pair stereo, Correlation around 0.7. (mono would be 1.0) This is a pretty wide stereo to start with, as you can see from the curves and correlation

Attachment 71373

The flipped polarity. Notice how the sides are higher in level than the mid. correlation is -0.6

Attachment 71374

and the 90 degrees off. Very wide stereo image, sides are as strong as the center. Correlation is a around -0.4

Attachment 71375

Really enjoyed your demos & explanations Doug! Big Help.

Nothing like having real time examples.

[SprintBob]

Based on Doug’s postings I bought the Blue Cat Stereo Scope plug-in and it’s a great tool that’s pretty straight forward to use.

[Rudy4]

Back in the "old days" the quick double-check for phasing issues was to simply push your monitors close together, facing each other.

This sounds rather simplistic, but nothing highlights phasing issues as quickly as that test. Bass can literally disappear, and a wide variety of other problems can instantly be ascertained. Of course, all the technical processes can verify and/or correct the causes, but nothing works as fast and reliably as the old "mechanical sum to mono" of listening to those closely positioned monitors!

[Doug Young]

Originally Posted by Rudy4

Back in the "old days" the quick double-check for phasing issues was to simply push your monitors close together, facing each other.

This sounds rather simplistic, but nothing highlights phasing issues as quickly as that test. Bass can literally disappear, and a wide variety of other problems can instantly be ascertained. Of course, all the technical processes can verify and/or correct the causes, but nothing works as fast and reliably as the old "mechanical sum to mono" of listening to those closely positioned monitors!

I think my monitors weight about 70 lbs :-) I'd learn about phase, but have my back in traction for a week!

[rick-slo]

For typical stereo mike positions the degree of out of phase goes from generally almost zip for low frequencies to significant amounts at various high
frequencies. Looking at a correlation meter keep that in mind. For me the most likely problem frequencies (harshness) are in the 4 to 7 kilohertz range.
The harshness is probably not really a correlation issue per se nevertheless using a tiny bit of track delay and/or a small decrease in volume of a problem
frequency using an equalizer is worth exploring.

[Rudy4]

Originally Posted by Doug Young

I think my monitors weight about 70 lbs :-) I'd learn about phase, but have my back in traction for a week!

I hear that!

The older I get the more I go for lighter weight stuff. It's nice to see many manufacturers moving to sound reinforcement, combo amps, and even instruments that feature a kinder, gentler form factor for we users who are moving towards "lower muscle mass", whether we want to or not!.

My desk monitors have gradually moved from 8" KEFs to Presonus Eris 5s. I've found that my hearing losses generally match my loss of muscle, so I'm just as happy with the compromise in fidelity as I am with the corresponding reduction in size and weight.

"Pushing them together facing each other" was more a possibility for us NS-10 users...

[Doug Young]

I'n dreading the day I have to move these monitors :-) Fortunately my interface has a mono button right on front, so I can do mono checks with no lifting!

[shufflebeat]

This is my favourite "what does comb filtering sound like?" vid.

Vid