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

[Cosmik]

FWIW, here is the off-axis response of the passive LS50.

On a general point regarding these sorts of graph, what do we think about the idea that it doesn't show phase fluctuations i.e. what might happen to phase at the crossover and/or the port?

The standard audiophile assumption is that phase doesn't matter - this is vigorously defended whenever brought up in forums. But there is also a standard assumption in speaker design that steep phase fluctuations at crossovers are bad, and it is one of the things that passive speaker designers wrestle with.

In other words, there is a conflict: does the frequency response curve tell you how a speaker will sound, or doesn't it?

 

[Thomas savage]

Ideally the speaker should have no sound of its own, the closer to that goal the better. How that then translates when all the sound waves are crashing about your listening room and indeed all about your body is another matter.

As always there's acidemic advantage but how relevant those are to what we really expirance is beyond by understanding, well and truly.

 

[watchnerd]

On a general point regarding these sorts of graph, what do we think about the idea that it doesn't show phase fluctuations i.e. what might happen to phase at the crossover and/or the port?

The standard audiophile assumption is that phase doesn't matter - this is vigorously defended whenever brought up in forums. But there is also a standard assumption in speaker design that steep phase fluctuations at crossovers are bad, and it is one of the things that passive speaker designers wrestle with.

In other words, there is a conflict: does the frequency response curve tell you how a speaker will sound, or doesn't it?

The DSP crossover crowd seems to think phase matters as they often talk of the ability of DSP crossovers to handle phase better.

Apparently the LS50 has a switch to turn phase optimization on and off.

That being said, I've rarely seen a graph of it as you point out.

 

[watchnerd]

I'm just surprised nobody has yet objected to the coincident / coaxial driver, claiming it to be a compromised solution where the juice isn't worth the squeeze.

 

[Cosmik]

Apparently the LS50 has a switch to turn phase optimization on and off.

The Kii three has a low latency mode that turns off the phase compensation. In the SOS review the reviewer says:

"... the change of phase response is clearly audible. The monitor loses a little of its imaging ability and overall precision in low-latency mode so that things sound a little less ‘together’. "

So this suggests that a frequency response curve alone cannot tell you how a speaker will sound. It even suggests that for any two speakers, better phase response might outweigh defects in the frequency response flatness department.

I mention it purely because there is usually a demand for measurements before anyone will consider claims regarding new wonder-speakers. In my case, I am prepared to accept a company like KEF's assurances that their speakers will always measure pretty well in the frequency response department. However, phase might be where it gets interesting.

We can split audiophiles into two groups: those who believe point blank that phase doesn't matter, and those who think it just might (implying that the historical "phase doesn't matter" listening experiments have always been defective in their methodology or scope e.g. only mono). I am in the second category...

 

[watchnerd]

The Kii three has a low latency mode that turns off the phase compensation. In the SOS review the reviewer says:

So this suggests that a frequency response curve alone cannot tell you how a speaker will sound. It even suggests that for any two speakers, better phase response might outweigh defects in the frequency response flatness department.

I'm going to go completely out on a limb here and give a personal anecdote. Feel free to discard as being a single data point with no statistical significance. But...

When I've used moderate DRC at home, I've often turned it off after a week or so. Why? Even though the RTA measured flatter at the listening position with DRC on, the imaging got worse and some other undefinable attributes (I hate to use terms like PRAT) felt worse to the extent that I enjoyed the music less. My completely untested hypothesis was that the DRC was messing with the phase in some way that I found subliminally unsettling or at least less convincing / enjoyable.

Heavy grains of salt to be taken with.

 

[RayDunzl]

My possibly faulty observation here is that my panels can throw sound with measurably good phase all the way to the listener, whereas my little JBLs do well on a nearfield measurement but the result is insane when measured at the listening position.

That occurs with or without AcourateDRC's modifications to the sound.

Red - wrapped phase of JBL LSR 308 at listening position.
Blue - JBL nearfield - at a meter or less, I forget
Gold - Martin Logan reQuest at listening position (10 feet)

Red - Showing a segment of as much as will fit on the display of the JBL at listening position (10 feet) unwrapped

I don't know what to blame for that, but think it is related to wide-dispersion design and room reflections.

 

[watchnerd]

My possibly faulty observation here is that my panels can throw sound with measurably good phase all the way to the listener, whereas my little JBLs do well on a nearfield measurement but the result is insane when measured at the listening position.

That occurs with or without AcourateDRC's modifications to the sound.

Red - wrapped phase of JBL LSR 308 at listening position.
Blue - JBL nearfield - at a meter or less, I forget
Gold - Martin Logan reQuest at listening position (10 feet)

View attachment 4189

Red - Showing a segment of as much as will fit on the display of the JBL at listening position (10 feet) unwrapped

View attachment 4190


I don't know what to blame for that, but think it is related to wide-dispersion design and room reflections.

I assume 300 Hz on up the ReQuest is all panel and almost no woofer?

I can't make any sense of what's going on with the LSR308 phase at the listening positioning or how that's even possible in any normal setting that isn't the inside of a garbage dumpster....

Confusing.

 

[RayDunzl]

I assume 300 Hz on up the ReQuest is all panel and almost no woofer?

The panel crosses to a 12" sealed woofer at a specified 180Hz.

 

[watchnerd]

The panel crosses to a 12" sealed woofer at a specified 180Hz.

Thanks, what did you use to measure it? REW + Umik?

I should measure my 2 ML's...

 

[RayDunzl]

what did you use to measure it? REW + Umik?

Yes.

I should measure my 2 ML's...

Oh, please do. This site is relatively devoid of objective "here's what I have happening" measurements to argue about.

 

[Blumlein 88]

My possibly faulty observation here is that my panels can throw sound with measurably good phase all the way to the listener, whereas my little JBLs do well on a nearfield measurement but the result is insane when measured at the listening position.

That occurs with or without AcourateDRC's modifications to the sound.

Red - wrapped phase of JBL LSR 308 at listening position.
Blue - JBL nearfield - at a meter or less, I forget
Gold - Martin Logan reQuest at listening position (10 feet)

View attachment 4189

Red - Showing a segment of as much as will fit on the display of the JBL at listening position (10 feet) unwrapped

View attachment 4190


I don't know what to blame for that, but think it is related to wide-dispersion design and room reflections.

Measuring 305s or Revel F12s in my video setup I get nearly identical phase results as you show Ray. I don't have them in the same room, but panels show less. My measurements are from about 11 feet. I am not posting them as they look so similar to yours as to be pointless to repeat. When looking at the phase if you let REW estimate the delay what sort of value do you get back? Also are you taking measures with a loopback timing reference or no reference. I have been not using a timing reference.

 

[Cosmik]

My possibly faulty observation here is that my panels can throw sound with measurably good phase all the way to the listener, whereas my little JBLs do well on a nearfield measurement but the result is insane when measured at the listening position.

I don't know what to blame for that, but think it is related to wide-dispersion design and room reflections.

The way I see it, if we believe that the speaker should project an anechoic rendition of the signal to our eardums, then yes, we would hope for a flat phase response there. A panel speaker does beam tightly at higher frequencies.

If, however, we believe (as I do) that the speaker should have a flat phase response, but that it is desirable for the room to make its own contribution at the listener's ear, then a phase measurement (and unsmoothed frequency response) is going to look arbitrarily chaotic at the listening position. The human listener won't hear it that way, though.

The KEF presumably has a controlled dispersion because of its concentric woofer/tweeter thingy, but not as tight as a panel speaker..?

 

[watchnerd]

The KEF presumably has a controlled dispersion because of its concentric woofer/tweeter thingy, but not as tight as a panel speaker..?

Some pretty nice dispersion measurements of the passive LS50 here.

Some samples:

 

[watchnerd]

Dammit, I might just have to buy these after seeing these graphs, even though there are a few things I don't like about them...

 

[fas42]

The real world experience is that if the drivers produce high quality, low noise acoustic energy then frequency response, phase, dispersion, room effects effectively disappear as being relevant ...

 

[watchnerd]

The real world experience is that if the drivers produce high quality, low noise acoustic energy then frequency response, phase, dispersion, room effects effectively disappear as being relevant ...

So you're saying I can make a really awesome driver that covers just one octave perfectly, say 512 Hz to 1024 Hz, and then all the other frequency response that it doesn't have will "effectively disappear as being relevant"?

 

[Cosmik]

The real world experience is that if the drivers produce high quality, low noise acoustic energy then frequency response, phase, dispersion, room effects effectively disappear as being relevant ...

A system that met that description could actually be emitting a completely different piece of music from the one being fed into it, or, say, a constant high quality, low noise sine wave.

 

[RayDunzl]

Are you taking measures with a loopback timing reference or no reference. I have been not using a timing reference.

I use the (newish) Acoustic Timing Reference in REW. It puts out a short high frequency pulse to one speaker, calls that return to the mic zero delay, and (apparently) quite accurately resolves the time/distance difference (within .02ms / 7 mm or so) to the other speaker or speakers.

If the speaker distances to the mic are not equal, there will be phase wraps and FR upset when measuring both speakers at the same time (which is my preference for in-room stuff).

MartinLogans with unequal distance (0.1ms/35mm timing offset):

 

[fas42]

So you're saying I can make a really awesome driver that covers just one octave perfectly, say 512 Hz to 1024 Hz, and then all the other frequency response that it doesn't have will "effectively disappear as being relevant"?

I was using the term "acoustic energy" as a playful way of saying, the normal signal - the drivers are just doing their job as normal - think of them being the highest quality headphones you have ever experienced, which just happen to be able to go much louder.

Why the effects that people normally worry about disappear is because your brain is reacting in a different way to what it's being fed. I'll use an analogy in a completely different sphere: you're getting a relaxation massage, once from a person who doesn't know what they're doing - you're aware of every movement of the hands, you're irritated by the level of pressure, he's spending too much time in the wrong spot; and then from someone who really knows his stuff - you're taken to another place, you feel like you're having, yes, a magical experience. Both are nominally doing the same thing, but the expertise, "quality" makes a huge difference, subjectively.