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KEF Q100 Speaker Review

MZKM

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Just checked the spin data and indeed, around 20 degrees off-axis seems best, which is a pretty common "point them straight forward" angle. I also found this to be the case with the R3 and LS50W - well, 15 degrees, since I was using 15-degree increments back then - so at this point, I'm pretty sure that's just how KEF designs speakers.:)

View attachment 53778

If you don't toe them in and reduce some of that excess 1K energy, you have a much more linear speaker.

P.S. REW now lets you use dashed lines, so I'm a very happy camper.

EDIT: @MZKM if you get the chance, would you mind computing the score with 20 degrees as the on-axis? The ER/PIR would technically also change slightly but that's likely a much smaller difference.
I can change just the on-axis to 20°, but I’ll leave everything else alone (this is a discontinued speaker, so don’t feel the need to spend the time on it); I’ll see what I get when I get back to my computer.
 

Biblob

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I can change just the on-axis to 20°, but I’ll leave everything else alone (this is a discontinued speaker, so don’t feel the need to spend the time on it); I’ll see what I get when I get back to my computer.
Would that be fair in comparison to the other speakers, which are scored on the on-axis?
 

Tks

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KEF fans either biting their nails and sweating awaiting the newer model results. Or sweating so much after foaming at the mouth that bossman didn't enjoy the subjective listening, (and has no idea how to do measurements, as famously put by Emotiva fanboys in the recent past).
 

hardisj

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FWIW, I tested the raw Q100 and LS50 drivers years back. Seems folks around here often ask for this kind of info. So here you go:
https://www.erinsaudiocorner.com/driveunits/kef-q100-drive-unit/
https://www.erinsaudiocorner.com/driveunits/kef-ls50-drive-unit/

Note: The on-axis dip is caused by the driver not being flush-mounted. Again, the tests were of the raw driver on a large baffle. No crossover. No enclosure. Just raw drive unit. This is not the same as a driver mounted in an enclosure with crossovers.
Additionally, my distortion measurements are performed at the 90dB/1m and 96dB/1m equivalents; I'm still not sure what Amir's tests conditions were here... must be nearfield because he says they are gated but yet the result goes below 100hz which doesn't make sense in the far-field and if so the 95dB is much lower at a 1 meter equivalent.
So, anyway, these are NOT apples to apples comparisons with Amir's. However, it is intended to give you an idea of what the drive units themselves contribute to the overall result.

For the 'fun' stuff, scroll to the bottom of the Q100 test and look at my testing of what happens to the tweeter response when the woofer cone is at rest, out and in.


Before/after I tested the raw drive units I did spend some time listening to the Q100 speaker.
Subjectively, I didn’t notice any audible distortion in my listening test of the speaker back then.
I don’t remember any tonality-based comments. I’d have to dig through my notes.
The one thing I did remember was just how large the soundstage was and how precise it seemed the imaging was with the q100 compared to other speakers (non-coincident) I had listened to before.
 
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tuga

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"The coaxial driver looks great and caters to audiophile intuition of "point source being good."" Is this intuition incorrect?

"One of the benefits of a coaxial driver is..."

What are some of the inherent performance disadvantages? (IE: Not price, having to design it right, etc.)

A few potential disadvantages I've heard of:

1. Genelec Emails: On massive models, a coaxial driver cannot handle the SPLs their main monitors can. Have not found evidence to the contrary, as I don't see a coaxial model that can go to 120dB or more.

2. Kii & Buchardt Emails: Coaxials present the tweeter with an ever changing waveguide. Evidence against found on page three: https://assets.ctfassets.net/4zjnzn...3bb717fe31e/genelec_8260a_technical_paper.pdf

3. Forums: Coaxials have a small gap that causes diffraction. Evidence to the contrary in the same document above.

4. Can't remember, but I swear an email with Dutch & Dutch or someone else from a forum a year ago brought up another "disadvantage" that has been resolved for a decade or more. Maybe it was not being time aligned? (The Elac Navis, and KEF LS50, and all other speakers by both brands don't seem to have this issue... People sometimes think of coaxial car stereo drivers I think that might have wonky dispersion.)

Potential Advantages:

1. Easier to not have crossover cancellation. (Off topic PM: why no active crossovers at -999dB per tenth of an octave?)
2. Better vertical dispersion, similar to horizontal.
3. Point source instead of a voice sounding like it's coming from a six inch or foot wide mouth.
4. More compact, shorter speaker designs are possible. 3-way the size of a 2-way.

These measurements are appreciated, this was one of the earliest speakers I looked at buying when I decided to do the DIY HiVi 3.1. Haven't heard this, but would have guessed it sounded better... But that's marketing!


The Acoustic Design of Minimum Diffraction Coaxial Loudspeakers with Integrated Waveguides

Aki Mäkivirta, Jussi Väisänen, Ilpo Martikainen, Thomas Lund, Siamäk Naghian


Coaxial designs, where several transducers are on the same acoustical axis, do not suffer from the sound colour change problem, and have long been regarded as a potent solution to improve the quality of the loudspeaker as a sound radiator. The fundamental benefit of a coaxial design is that the geometry of the transducer distances to the listening location remains the same when the listener moves off-axis to any direction. Because the relative timing does not change or changes minimally, the magnitude response at the crossover transition remains flat also for the off-axis positions.
Another benefit of coaxial designs is that they can have stable frequency response also when the listener is close to the loudspeaker. This improves near field monitoring as the sound colour created by the loudspeaker remains stable with the changing distance to the loudspeaker.

Near field monitoring can reduce the influence of the room acoustics and improve the maximal SPL of the loudspeaker without evoking nonlinearities in transducers typically occurring at high excursions.

However, current coaxial transducers suffer from problems such as sound-colouring diffraction due to discontinuities between the coaxially located drivers. Particularly two-way coaxial designs can have problems with Doppler distortion, having to operate each transducer over a wide frequency band.

Although a two-way active loudspeaker is the ubiquitous reliable work horse of the industry, a three-way design offers the potential for improving performance in several ways including extended frequency range, better control of directivity, higher output capacity and lower distortion. Particularly for coaxial designs, a three-way construction can also significantly reduce the issue of Doppler distortion in the coaxial transducers.

(...)

Acoustic benefits of coaxial design

The coaxial transducer arrangement has acoustic benefits. A multiway loudspeaker has two transducers reproducing sound simultaneously across the crossover range of frequencies. Conventional multiway designs have transducer locations distributed across the front baffle. The summation of the outputs from any two transducers is usually designed to be in phase in the primary listening direction (acoustical axis). When the two outputs are in the phase the system output remains flat. For off-axis locations, the two transducers are not in phase because the distances to the transducers have changed from the design geometry (Figure 1). This can produce audio coloration which changes when the listener moves further off-axis. Placing transducers coaxially can reduce or eliminate such coloration.

Crossover performance is further improved by time- aligning the two coaxially constructed transducers at the crossover frequency, with the benefit of maintaining the time domain waveforms. This is particularly important for those transducer constructions where the physical height of the tweeter and midrange transducers are significantly different.

https://downloads.ctfassets.net/4zj...kivirta_et_al_paper_95_2017-04-03_v_1.0.2.pdf
 
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QMuse

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FWIW, I tested the raw Q100 and LS50 drivers years back. Seems folks around here often ask for this kind of info. So here you go:
https://www.erinsaudiocorner.com/driveunits/kef-q100-drive-unit/
https://www.erinsaudiocorner.com/driveunits/kef-ls50-drive-unit/

That tweeter certainly doesn't look to be optimised for on-axis response:

Kef-Q100-Drive-Unit-Tweeter-Only-0-30-60.png
 

maty

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With the original crossover.

10º-20º-30º, measured by Zvu

KEF-Q100-fabricka-10-20-30-zvu.png



30º-40º-50º, measured by Zvu

KEF-Q100-fabricka-30-40-50-zvu.png



60º-70º-80º, measured by Zvu

KEF-Q100-fabricka-60-70-80-zvu.png



0º-80º-90º, measured by Zvu

KEF-Q100-fabricka-0-80-90-zvu.png
 

Francis Vaughan

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Would that be fair in comparison to the other speakers, which are scored on the on-axis?
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. Insisting that any device be scored in a manner it was not intended to be used is not useful. The score formula does not require on physical axis. It uses the listening axis, whatever that might be. If the speaker is designed with a given listening axis, that is what should be used.
 

maty

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That tweeter certainly doesn't look to be optimised for on-axis response:

View attachment 53795

It is evident except for those who only look on-axis frequency. That is why I am very grateful to Erin for his two analyzes. I already had graphics but his work was final for purchase.

I already imagined that there would be a multitude of cost reduction compared to the much more expensive, then, KEF LS50.

For a room, closing the port with the foams and two subwoofers cut over 110-120 Hz we would have a good system. Q100, Q150 or R100.

It is also evident that KEF has had problems integrating the small coaxial with a woofer in R300. In the new R3 the integration is not yet perfect.
 
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Soniclife

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Of course I ignore it, but we shouldn't forget that many visitors to this website just come for quick buying decisions, read "science" in the title, see alot of measurements and then just decide on panthers. ;)
I doubt many casual visitors know what the panthers mean, they probably just skim down to the conclusion and read that, if they only get as far as the first image and base all their decisions on that then they are still getting more than they paid for.
 

Soniclife

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Regarding distortion, do coaxial drivers get to effectively game the measurements compared to playing music? Single tone Vs multitone differences.
 

Soniclife

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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. Insisting that any device be scored in a manner it was not intended to be used is not useful. The score formula does not require on physical axis. It uses the listening axis, whatever that might be. If the speaker is designed with a given listening axis, that is what should be used.
Ideally the calculation would work out the optimum 2D angle, and calculate based on that, for the maximum score for the speaker. And report the angle used. If the user chooses to use a different angle from that which the score was based on that's their business.
 

QMuse

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FWIW, I tested the raw Q100 and LS50 drivers years back. Seems folks around here often ask for this kind of info. So here you go:
https://www.erinsaudiocorner.com/driveunits/kef-q100-drive-unit/
https://www.erinsaudiocorner.com/driveunits/kef-ls50-drive-unit/


And a quick note:
Subjectively, I didn’t notice any audible distortion in my listening test of the speaker back then.

I don’t remember any tonality-based comments. I’d have to dig through my notes.

The one thing I did remember was just how large the soundstage was and how precise it seemed the imaging was with the q100 compared to other speakers (non-coincident) I had listened to before.

Distorion you measured for both dirvers seems to be higher than what Amir measured.
 

maty

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Prana Ferox

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dorirod

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Thank you so much @amirm ! I bought my pair for $245 in 2017 from Amazon. I'm pretty happy with how they sound (but I don't listen to them that loud), score doesn't seem bad for the price I paid.
 

maty

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KEF says: 86 dB and 8 Ohms nominal. True: 85 dB and 5 Ohms nominal -> you need amplifier with many watts at 4 Ohms if you want to listen to very good recordings with high/very high DR as me.

Logic (mine) dictates first to test the improvement of existing components, one by one, first in one box and then in the other in order to compare. And always the same two persons.

For a new crossover I will always be on time. The bypass Miflex KPCU-01 0.01uF capacitor can be reused, but not the Mills MRA 0.68 Ohms. The improvement produced is surprising / amazing, at least with my recordings.
 

hardisj

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That tweeter certainly doesn't look to be optimised for on-axis response:

View attachment 53795
Ugh. I thought I put the note in for that page like I did for the LS50…

The on-axis dip is caused by the driver not being flush-mounted. Again, the test was of the raw driver on a large baffle. That was a problem with my setup then; I didn't have the ability to flush mount. But now I do. Would be nice to re-test it just for the heck of it, but there's no point really.
 

hardisj

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Distorion you measured for both dirvers seems to be higher than what Amir measured.

Remember: 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.
 
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