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KEF LS50 Wireless - DAR's Product of the Year 2016

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watchnerd

watchnerd

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All available data is we aren't that sensitive to phase at higher frequencies (above 1500 hz to be arbitrary). If we are, then minimum phase filters will mess with phase in the treble more than conventional digital filters. Though the audio press gives one the opposite impression it is just one more case where audiophile conventional wisdom doesn't add up with the facts.

Right, but I think part of @Cosmik 's underlying question is asking if the available data on phase sensitivity is wrong.
 

RayDunzl

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My experiments say:

Phase is very important for localization - that's the main reason there is a sweetspot. More important than SPL.

But steady state phase is ignored to the perception of steady-state timbre, at least to my deaf ears, in the cases I have created. Maybe a very subtle difference in A/B switches that could just as well be the "effect" of an A/B switch.

Changing phase is another story.
 

fas42

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My experiments say:

'Wrong' phase can make things sound a bit weird, but if the quality in the sound is there the brain compensates - in no time at all. Phase probably is very necessary for the normal sweetspot behaviour, and it's what most likely is that which causes a mono source to "track" your position in the room. I've actually tried an almost 100% mismatch between left and right channels, in that the speaker, the amplifier, and the location of the amplifier are completely different between the two - and this produced sound which still 'worked' - people listened, and didn't pick anything out of the ordinary ... :p.
 

fas42

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I don't think you will be blown away. Now the 305s are good, amazingly so considering price for an active speaker. Evenness of the FR, and everything else is and sounds nicely done. I do think compared to some electrostats and even say monitor sized Harbeths or Spendors they lack something. They actually seem better balanced top to bottom than those yet while nothing to complain about it feels as if something is missing. This speaking from a purely subjective audiophool perspective. It isn't much and might not be missed except in a direct side by side comparison. And yes I have heard the 305s sitting on stands dead center of some Soundlabs so we could switch between them.

What seems missing is fine detail and apparent speed. Yes I know real speed isn't a thing other than frequency response. But subjectively the 305s sound not slow, but less fast. As if on acoustic guitar plucks they just miss the initial edge of the pluck. And they aren't bad in this sense the way bad boxes were way back when. The 305s are subtly slow on the uptake. Also while I don't really hear the box, the entity of being a speaker doesn't quite disappear the way highest quality speakers do. Plus this disappearing is less an issue used as monitors nearfield as they were intended to be used. .
This is the area I work in. "It feels like something is missing" which is "fine detail and apparent speed", "slow on the uptake" and "doesn't quite disappear the way highest quality speakers do" are equivalent to saying, audible low level artifacts are degrading the sound. No phase measurements are harmed :), but all the little shortcomings that drag the quality down are sorted out.
 

Blumlein 88

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Right, but I think part of @Cosmik 's underlying question is asking if the available data on phase sensitivity is wrong.

I doubt it is wrong. Available data may not tell the entire story. It doesn't make sense that phase at higher frequencies would be audible. Once the wavelength of the sound is shorter than the distance between ears phase is less useful. When several wavelengths fit in that space minor phase differences couldn't be used for location as it would point to multiple locations. Does a phase difference of 10 degrees mean the angle is 10 degrees or 370 degrees or 730 degrees. All would get perceived the same way from phasing.
 

RayDunzl

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It doesn't make sense that phase at higher frequencies would be audible.

Does a phase difference of 10 degrees mean the angle is 10 degrees or 370 degrees or 730 degrees. All would get perceived the same way from phasing.

Ok, so I made a little test here.

A second of stereo silence, with 10 cycles of 1000Hz in the middle of it, with the right channel delayed by 1 ms, endless repeat playback.

It sounded sort of like a click, located only in the left channel when listening from the sweet spot.

Hmm. Increased the length of the tone to 100 and then 300 ms to see if it would move back to center once the initial transient had passed. Didn't seem to.

Hmm. Maybe the "click" of the tone starting abruptly overwhelmed my hearing the tone or something like that, so made each track fade in over 3 cycles and fade out over three cycles.

Still locates to me as being in the left channel and remains there with 1 cycle delay on the right channel despite having 298 cycles that are in phase.

Hmm... Sleepy, so will have to pick this up again later.

Early simple-minded conclusion: The relative timing (phase) of the "attack" audibly locates the tone left/right of center in the soundstage, even though the body of the tone is identical in both channels, i.e., in-phase and equal amplitude sine. Not sure if the timing of the release contributes spatially yet - untested.

300ms 1kHz test tone, one cycle delay in right channel, 3 cycle fade-in and fade-out:

upload_2017-1-1_4-52-38.png
 
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watchnerd

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The relative timing (phase) of the "attack" audibly locates the tone left/right of center in the soundstage, even though the body of the tone is identical in both channels, i.e., in-phase and equal amplitude sine.

View attachment 4211

This is consistent with studies I participated in that study impulse response and location perception.

Basically, our sensory system is very sensitive to impulse response and using it to determine location. So sensitive, in fact, that it completely bypasses our high cognitive functions. It's very 'lower brain / lizard brain', hard-wired to our reflexes.

The evolutionary hypothesis is that being able to hear and react to a twig snapping behind you goes waaaay back...
 

Blumlein 88

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Ok, so I made a little test here.

A second of stereo silence, with 10 cycles of 1000Hz in the middle of it, with the right channel delayed by 1 ms, endless repeat playback.

It sounded sort of like a click, located only in the left channel when listening from the sweet spot.

Hmm. Increased the length of the tone to 100 and then 300 ms to see if it would move back to center once the initial transient had passed. Didn't seem to.

Hmm. Maybe the "click" of the tone starting abruptly overwhelmed my hearing the tone or something like that, so made each track fade in over 3 cycles and fade out over three cycles.

Still locates to me as being in the left channel and remains there with 1 cycle delay on the right channel despite having 298 cycles that are in phase.

Hmm... Sleepy, so will have to pick this up again later.

Early simple-minded conclusion: The relative timing (phase) of the "attack" audibly locates the tone left/right of center in the soundstage, even though the body of the tone is identical in both channels, i.e., in-phase and equal amplitude sine. Not sure if the timing of the release contributes spatially yet - untested.

300ms 1kHz test tone, one cycle delay in right channel, 3 cycle fade-in and fade-out:

View attachment 4211

Okay good test. Our max acuity to phase is around 800 hz. Try the same thing at 4 khz.

EDIT to add:

I have read that when synchronized pulses trains are heard at higher frequencies the timing of the initial part of the transient is used in localization. So I repeated your experiment getting the same results at 1 khz even up to half second bits of the tone. I repeated it at 4 khz and that too localizes toward the side that starts first in time if the difference is 1 millisecond. Of course that is 4 cycles of a 4 khz tone. As such it would represent a greater phase difference though both channels are synched in phase. At only one cycle you don't notice much difference. While delaying the 1 khz signal the same small time amount of 1/4 millisecond (which is a smaller phase amount) the sound still localizes to one side. Of course the two channels are not synched on the waveform in such a case.

Now if I go back to the 4 khz signal, delay one channel by 1 millisecond or 4 cycles the tone localizes to the initial side. If you reduce the signal level to the initial or leading channel by 6 db then the sound jumps over to localizing on the other side. Which fits with the idea at higher frequencies level differences are how sound is localized. Reducing the 1 khz leading channel by 6 db also causes a shift. Rather than jumping to the opposite side however it ends up just about centered in the middle.

BTW, I did this with headphones to keep everything cleaner.
 
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