KEF Q100 Speaker Review

[QMuse]

Raw driver. So no benefit of the enclosure. Plus, I still don't have a clear understanding of what SPL level Amir is testing at. Sometimes the y-axis seems like it can be trusted; other times it does not. But I did distortion testing at 90dB and 96dB.

Please note that I didn't say your measurement is in no way lessa accurate ,I simply noted they differ by quite a lot.

 

[hardisj]

Please note that I didn't say your measurement is in no way lessa accurate ,I simply noted they differ by quite a lot.

I understand. I didn't take it that way. I just wanted to stress the two measurements are intended to be different; one is a speaker system and one is a component of the speaker system (raw driver). I edited my original post to make that clear just in case there might be any future confusion.

 

[QMuse]

I understand. I didn't take it that way. I just wanted to stress the two measurements are intended to be different; one is a speaker system and one is a component of the speaker system (raw driver). I edited my original post to make that clear just in case there might be any future confusion.

I was expecting some difference, but not that much. But I can easilly be wrong on this as I haven't studied drivers measurements much.

 

[hardisj]

I was expecting some difference, but not that much. But I can easilly be wrong on this as I haven't studied drivers measurements much.

Well, you can ignore the on-axis tweeter response of the raw driver because of the non-flush mounting. Sucks. But that's just the flaw in my old measurement setup. In future tests all drivers will be flush mounted. But even still, coaxial drivers are a funny thing because they need as smooth a transition and ideally one that matches the profile of the midwoofer cone as well (that's why you'll notice the new Kef Reference series don't have just a little ring around the driver; they have a whole disc matched to the midrange profile).

I can't look at the HD right now (ironically, my site is blocked at work). So I can't compare directly. But I can say that the enclosure of the speaker itself will help boost the low end response which will increase the delta between the fundamental and the distortion components, thus lessening the % difference compared to a raw driver on a flat baffle. So keep that in mind.

 

[pierre]

Spin data enclosed.

Nice to have added a license that allows to play with the data.

 

[QMuse]

I can't look at the HD right now (ironically, my site is blocked at work). So I can't compare directly.

LOL

But I can say that the enclosure of the speaker itself will help boost the low end response which will increase the delta between the fundamental and the distortion components, thus lessening the % difference compared to a raw driver on a flat baffle. So keep that in mind.

I'm aware of that, but it is a difference in tweeter's THD measurement that actually bothers me.

 

[hardisj]

LOL



I'm aware of that, but it is a difference in tweeter's THD measurement that actually bothers me.

View attachment 53804

Easy: no crossover on raw driver measurements

 

[anmpr1]

Speaker Listening Tests I used the KEF Q100 in my main system, playing in mono (provides best discrimination)...

You probably answered this in other threads, so sorry for asking again if so. But when you listen 'in mono' is that with one speaker playing a mono (summed channel) source, one speaker playing half a stereo channel, or two speakers set up as a stereo pair playing a mono (summed) source?

 

[Soundstage]

This wouldn’t be official.
I calculate a listening window score (replaces on-axis) for all speakers in the preference score database.

Could you please also calculate the score of the KEF LS50 Off axis? Thanks

 

[maty]

BTW, Zvu made measurements of KEF Q100, KEF LS50 and KEF R300. And has modified crossover for the three, flattening the axis frequency response. In Diyaudio.com and HTguide.com.

A picture, optimized, with KEF LS50:

http://www.htguide.com/forum/showthread.php?44315-Measurements-of-Kef-LS50

 

[jhaider]

I was referring to Amir's comments from the listening tests "There was also some distortion which seemed to be constant throughout everything I played. A buzzing type of secondary tones. "

My guess is IMD from pushing a small cone full range. A trained listener can hear that pretty easily.

I've owned a few of these speakers. Overall I think that they're excellent in a bass managed system, albeit not the most pleasant listen with sibilant recordings. The extraordinary polars and low price make them ideal candidates for someone who wants to practice DSP EQ'ing.

The primary midrange/treble improvement in the Soundfield Audio Monitor 1 (a cult classic that used this coax along with an 8" powered woofer) was reduced emphasis on sibilants.

 

[QMuse]

My guess is IMD from pushing a small cone full range. A trained listener can hear that pretty easily.

That sounds logical, but wouldn't that also show with single tone measurement (THD)?

Are you saying that SPL of 95dB at 1m is this tweeters full range?

 

[617]

One point we need to keep in mind here:

Distortion measurements from different sources and made at different times cannot be compared.

Also @hardisj did you measure xmax for this driver?

 

[QMuse]

One point we need to keep in mind here:
Distortion measurements from different sources and made at different times cannot be compared.

Do you care to explain why? Is THD larger in the morning vs the evening or in the winter vs the summer?

Everybody uses the same THD formula, so as long as harmonic levels were measured accurately with calibrated mic which itself doesn't introduce significant THD I see no reason why frequency response could be compared but THD couldn't.

 

[thewas]

Due to their smooth directivity the Q100 can be EQed to even higher perfection, so equalizing the listening window smoothes thus also the predicted in-room response nicely:

(upper curves are LW and PIR without and the graphically offsetted by -10 dB curves are LW and PIR with my 10 PEQ).

Please feel free to contact me if you need the filter coefficients.

 

[617]

Do you care to explain why? Is THD larger in the morning vs the evening or in the winter vs the summer?

Everybody uses the same THD formula, so as long as harmonic levels were measured accurately with calibrated mic which itself doesn't introduce significant THD I see no reason why frequency response could be compared but THD couldn't.

When you make distortion measurements there are a huge number of variables in the set-up which dramatically influence the results. If everything is kept constant, useful comparisons can be made, but this is not the case between different people at different times. Here are some things which can completely change the measurements:

• Drive level of speaker
• Distance from microphone to DUT
• Sensitivity of microphone
• Amount of gain from mic preamp
• Type of distortion measurement being made - continuous vs. stepped sine
• Use of different or no protection capacitors on HF sources
• Intrinsic distortion of microphone - mics that don't contribute distortion at high SPL are $$
• Presence or absence of room effects

Distortion measurements are used by designers to analyze trends in drivers to see if a certain application is straining them. They are not reliable for comparison between different units measured at different times by different people. I don't even think Amir's distortion measurements can be reliably compared, unless he settles on a method which keeps all these things constant.

I'd encourage people discussing distortion to take a quick look at this thread:
https://www.audiosciencereview.com/...ds/speaker-equivalent-sinad-discussion.10818/
Which has a good discussion on why THD is not a meaningful factor in sound quality. Toole's quote sums it up well:

"In loudspeakers it is fortunate that distortion is something that normally
does not become obvious until devices are driven close to or into some limiting
condition. In large-venue professional devices, this is a situation that can occur
frequently. In the general population of consumer loudspeakers, it has been very
rare for distortion to be identifi ed as a factor in the overall subjective ratings.
This is not because distortion is not there or is not measurable, but it is low
enough that it is not an obvious factor in judgments of sound quality at normal
foreground listening levels."

I would add that even in 'large-venue professional devices' THD does not correlate to sound quality unless, as he mentions, things are going seriously wrong.

 

[QMuse]

When you make distortion measurements there are a huge number of variables in the set-up which dramatically influence the results. If everything is kept constant, useful comparisons can be made, but this is not the case between different people at different times. Here are some things which can completely change the measurements:

• Drive level of speaker
• Distance from microphone to DUT
• Sensitivity of microphone
• Amount of gain from mic preamp
• Type of distortion measurement being made - continuous vs. stepped sine
• Use of different or no protection capacitors on HF sources
• Intrinsic distortion of microphone - mics that don't contribute distortion at high SPL are $$
• Presence or absence of room effects

Distortion measurements are used by designers to analyze trends in drivers to see if a certain application is straining them. They are not reliable for comparison between different units measured at different times by different people. I don't even think Amir's distortion measurements can be reliably compared, unless he settles on a method which keeps all these things constant.

I'd encourage people discussing distortion to take a quick look at this thread:
https://www.audiosciencereview.com/...ds/speaker-equivalent-sinad-discussion.10818/
Which has a good discussion on why THD is not a meaningful factor in sound quality. Toole's quote sums it up well:

"In loudspeakers it is fortunate that distortion is something that normally
does not become obvious until devices are driven close to or into some limiting
condition. In large-venue professional devices, this is a situation that can occur
frequently. In the general population of consumer loudspeakers, it has been very
rare for distortion to be identifi ed as a factor in the overall subjective ratings.
This is not because distortion is not there or is not measurable, but it is low
enough that it is not an obvious factor in judgments of sound quality at normal
foreground listening levels."

I would add that even in 'large-venue professional devices' THD does not correlate to sound quality unless, as he mentions, things are going seriously wrong.

Everything you said is true and it does to some extent affect precision of THD measurement. Unfortunately all that in the same manner also affect frequency response measurements but I don't remember anybody complaining. In fact there have been many comparisons of various FRs made by different sources and in totally different venues.

P.S. Don't you think quoting Toole has become kind of obsolete as pretty much all of us have read the book?

 

[edechamps]

I think one would argue that it makes the score fairer all round. There are some other speakers that arguably should also be re-scored with an off axis response.

It's technically impossible to do that accurately from the data @amirm currently provides, as I explained in a separate thread. It looks like @MZKM might try to regenerate a score just by replacing On-Axis with a different angle, which, strictly speaking, is not a valid use of the score formula (because one would need to recalculate PIR as well). The alternative is to recalculate PIR by interpolating the missing diagonal angles, which is not trivial and comes with associated interpolation error, the magnitude of which is unknowable without access to ground truth. So, in the end, you end up with a calculated score that's highly suspect. Not particularly useful, IMHO.

 

[QMuse]

It's technically impossible to do that accurately from the data @amirm currently provides, as I explained in a separate thread. It looks like @MZKM might try to regenerate a score just by replacing On-Axis with a different angle, which, strictly speaking, is not a valid use of the score formula (because one would need to recalculate PIR as well). The alternative is to recalculate PIR by interpolating the missing diagonal angles, which is not trivial and comes with associated interpolation error, the magnitude of which is unknowable without access to ground truth. So, in the end, you end up with a calculated score that's highly suspect. Not particularly useful, IMHO.

Using On-axis with different angle with original PIR seems more wrong than using that same On-axis with PIR recalculated using inpterolated data. First pair is IMO meaningless because, well, it is not a pair at all.

 

[Rockfella]

I always say speaker business is 80% about marketing and KEF has mastered that art.
- amirm

Only JBL 305II has shined so far I guess. The Genelics too.