Does Phase Distortion/Shift Matter in Audio? (no*)

[restorer-john]

Kudos for your candour.

 

[Blumlein 88]

That totally explains it. There is nothing more frustrating than reading, or typing anything remotely technical on a phone screen. I refuse to do it.

It's a mush of predictive text, corrections I didn't ask for, big man fingers, missing characters, etc. Even a laptop keyboard is bad enough.

Go retro, get yourself an IBM 'clicky'!

View attachment 135507

In a similar vein, did you know you can connect a normal bluetooth keyboard to your phone and type like an absolute boss? A member here told me that.

I spilled a drink on my cheap Logitech keyboard, and unlike previous times it wouldn't come back to life.

After some looking around, I replaced it with this Logitech clicky keyboard. It has the good mechanical switches and is excellent to type on. Only $59 in the USA. I selected the brown switches as they are optimized for typing while most of the others are optimized for gaming. It also is lighted. A really good choice without having to dig up old IBMs or pay for some of the modern super expensive clickety keyboards.

https://www.amazon.com/gp/product/B089YFHYYS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

[Francis Vaughan]

Is phase shift part of the reason why there isn't currently a way of testing audio gear with arbitrary signals?

Not really.
If you take the Fourier Transform of any appropriate signal you get the phase information. An FT delivers a real and an imaginary part, and the imaginary part contains the phase information. You can do what you like with it. Mostly it just gets thrown away when doing distortion analysis. It is useful and I keep wishing that Amir could find a way of getting hold of it, as it allows reconstruction of the full transfer function of the device. Having this we could apply a couple of metrics that take into account the human ear's performance, and get something closer to a meaningful figure of merit to understand the distortion numbers.
A FT delivers a term with a wave number of zero. This is the time offset. Typically we just throw that term away, and everything remaining has no dependance on a constant time delay. (It is a neat trick that is sometimes useful to do just this, and the inverse FT can get you back the signal without the offset.) There is a bit of handwaving here to do with what constitutes a suitable signal, windowing, and the like.

However, if you want to test with an arbitrary signal, you can't use the AP's party trick, which is its ability to null the test signal. It is this ability when testing with a pure tone that allows the AP to dig so very deep into the residuals. Without that you are constrained by the intrinsic capability of the ADC when handling full amplitude signals.

 

[Hayabusa]

If we assume that stereo image is 3D and contains distance information, then distance information may be distorted due to different phase at different frequencies.

It may be difficult or impossible to hear at the high frequencies where amp roll-off is occurring, but when I was designing cross-over filters (long time ago, though), I was using the test signal of a sweep frequency fixed point source that I recorded myself. If the sound source moved (and it often did) I was assuming speaker had a problem, as point was relatively static when played back through the single driver speakers.
Without any scientific proof, I was assuming this was caused by phase shift in the filter. Or is it all wrong?

More likely the perceived position change is because of frequency dependant directivity combined with the room.
I assume you tested this with one speaker?

 

[restorer-john]

After some looking around, I replaced it with this Logitech clicky keyboard. It has the good mechanical switches and is excellent to type on. Only $59 in the USA. I selected the brown switches as they are optimized for typing while most of the others are optimized for gaming. It also is lighted.

You're only one step away from a full RGB gaming keyboard.

 

[Blumlein 88]

You're only one step away from a full RGB gaming keyboard.

Yes which is what I was trying to avoid, and did so successfully.

I do use an inexpensive gaming mouse. One they last much better. Two their better resolution make them very nice for editing photos. Three they are shaped and weighted to have a nice feel in your hand.

 

[restorer-john]

Two their better resolution make them very nice for editing photos

All those instagram selfies huh?

 

[andivax]

I didn't check the 2 videos yet (call and responce LOL) but John Oram uses phase shift in his EQ's (with capacitors and resistors) to decrease harmonic distortion.

 

[richard12511]

As Amir explained in his video, the effects of phase shift is audible during certain circumstances, e.g. with test signals. I provided test signal as well as music example from of a Diana Krall record where an all-pass filter at 150 Hz causes audible effects. These phenomena are known already and notably far from those claims made in the original video from Paul.

Using a headphone, the shift in timbre is quite evident:

https://www.dropbox.com/s/qaeme17ovkved9a/all pass.wav?dl=0

I only see one file there?

 

[richard12511]

Unfortunately not a solution if the dominant source for content is streaming.

Many AVRs can do this also, which might be a solution for the streaming problem, depending on one's setup.

 

[Thomas_A]

I only see one file there?

Yes, same bass note repeated. Every second was all passed. Here is another one flipped every 2nd with more repeats to hear the change in timbre more easily.

https://www.dropbox.com/s/4xi36h10alrhkbt/allpass2.wav?dl=0

 

[markus]

Many AVRs can do this also, which might be a solution for the streaming problem, depending on one's setup.

I don't know of any AVR that would let the users upload their custom designed FIR filters. Furthermore, at 65k/130k taps delay is north of a second. Not feasible for anything but music.

 

[ernestcarl]

I don't know of any AVR that would let the users upload their custom designed FIR filters. Furthermore, at 65k/130k taps delay is north of a second. Not feasible for anything but music.

Maybe not... Don't have any experience with AVRs myself, but aren't there any that can delay (or forward) the picture/video fixing any lip sync issues like JRiver (software player) does?

 

[Francis Vaughan]

Something needs to either buffer up the video, which means lots of memory - and modern AVRs only do basic HDMI switching, or you need to negotiate with the media source to offset production of the video and audio. Buffering audio to cope with a few frames of video delay is easy, the converse is a pain.

It seems that the Apple TV can be convinced to provide offsets in either direction to cope with latency. However so far as I can see there isn't a control, rather you use your iPhone (you do have one don't you) to listen to test tones and it negotiates with the Apple TV to set the delay needed.

 

[ernestcarl]

rather you use your iPhone (you do have one don't you) to listen to test tones and it negotiates with the Apple TV to set the delay needed.

Huh. I've been torturing myself with trying to match sound and video by playing a karaoke-like music video of Rex Smith lip-syncing to this song (imperfectly, I should add):

 

[MRC01]

... Go retro, get yourself an IBM 'clicky'!
...
did you know you can connect a normal bluetooth keyboard to your phone and type like an absolute boss? A member here told me that.

Unicomp still makes those with true stainless steel buckling spring switches. The best keyboard EVER.
The problem with BT keyboards is the delay. It is tiny, but noticeable and incredibly frustrating for those who are fast touch typists. Even a hard-wired USB keyboard has a slight delay compared to the old PS2 keyboard connectors.

... It has the good mechanical switches and is excellent to type on. ... I selected the brown switches as they are optimized for typing while most of the others are optimized for gaming. ...

Nice to meet another mechanical keyboard lover. Once you use mechanical switches, nothing else will do. If "brown" refers to Cherry Brown, they are very light. Too light for me, I accidentally press them when feeling for the home keys. I prefer the heavier stroke and stronger tactile feedback of true buckling spring switches. That is the best keyboard for typing ever created by mankind. And it sounds fantastic, going "tock tock" instead of "click click". Cherry Blues are the best approximation I have found, a bit heavier and more clicky than the browns, but they are still only a pale imitation.

 

[richard12511]

I don't know of any AVR that would let the users upload their custom designed FIR filters. Furthermore, at 65k/130k taps delay is north of a second. Not feasible for anything but music.

I just meant they will let you delay the video by a user defined amount. They won't take FIR filters or do any automatic calculation, but you can get the video synced for all sources by manually entering the delay that you know you need. I actually didn't know how much to add, as I was going through 3 EQs at the time(Dirac, Audyssey, and GLM), but with trial and error I was able to get the audio and video perfectly synced(tested with gaming). Took maybe 2-3 minutes of trial and error .

 

[Wes]

as we have now reached p. 14, I offer this relating to phazer distortion and audiophile advertising claims ...

 

[Thomas_A]

I just took a test to check my brain.

 

[markus]

I just meant they will let you delay the video by a user defined amount. They won't take FIR filters or do any automatic calculation, but you can get the video synced for all sources by manually entering the delay that you know you need. I actually didn't know how much to add, as I was going through 3 EQs at the time(Dirac, Audyssey, and GLM), but with trial and error I was able to get the audio and video perfectly synced(tested with gaming). Took maybe 2-3 minutes of trial and error .

Again, not feasible with that many taps and resulting delays >1000ms. SSPs usually let you delay audio but not video.