• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

KEF Reference 1 META Bookshelf Speaker Review by Erin's Audio Corner

Mnyb

Major Contributor
Forum Donor
Joined
Aug 14, 2019
Messages
1,329
Likes
1,719
Location
Sweden, Västerås
Very nice speaker indeed :) hopefully i can listen to it in shop nearby .

Price is a bit much , but thats how the high end market seems to work .

They could probably build an equally good speaker with the same mfg tech as R3 and not hand built with high end finish .
But it would fall in an in between price brackets with no customers ? to expensive and to cheap at the same time .

So from a commercial company the top shelf products will be in exclusive price bracket and exclusively made with a story to go , but there will be an used market ? they seems built to last .

Over all amazing engineering.
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
5,941
Likes
5,875
Location
Brussels, Belgium
@pierre

do you mind calculating the score on the LS50 meta Audioexpress spinorama?

Just want to see how close you can get with an LS50 meta with a subwoofer compared to this.
 

Vacceo

Addicted to Fun and Learning
Joined
Mar 9, 2022
Messages
690
Likes
569
Very nice speaker indeed :) hopefully i can listen to it in shop nearby .

Price is a bit much , but thats how the high end market seems to work .

They could probably build an equally good speaker with the same mfg tech as R3 and not hand built with high end finish .
But it would fall in an in between price brackets with no customers ? to expensive and to cheap at the same time .

So from a commercial company the top shelf products will be in exclusive price bracket and exclusively made with a story to go , but there will be an used market ? they seems built to last .

Over all amazing engineering.
I think that is what we´ll see at some point in the near future, perhaps by the end of the year or next year. R series typically tickles down the advancements of the Reference series for a more affordable price.
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
1,751
Likes
2,663
Location
Germany
Would you not call "the sound emitted to that side which gets reflected back to the membrane" distortion?
No, i would call "the sound emitted to that side which gets reflected back to the membrane" exactly "the sound emitted to that side which gets reflected back to the membrane".

If i want to say "distortion", i say "distortion".
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
5,941
Likes
5,875
Location
Brussels, Belgium
No, i would call "the sound emitted to that side which gets reflected back to the membrane" exactly "the sound emitted to that side which gets reflected back to the membrane".

If i want to say "distortion", i say "distortion".
Distortion literally means ‘not good’

It’s the most umbrella term in existence. Everything is distortion.
 

Vacceo

Addicted to Fun and Learning
Joined
Mar 9, 2022
Messages
690
Likes
569
Distortion literally means ‘not good’

It’s the most umbrella term in existence. Everything is distortion.
I assumed that distortion means any change in the wave, from the source, at any point of the signal chain. And I guess it is inevitable no matter what. Audible or not, is a different matter.
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
5,941
Likes
5,875
Location
Brussels, Belgium
I assumed that distortion means any change in the wave, from the source, at any point of the signal chain. And I guess it is inevitable no matter what. Audible or not, is a different matter.
yes but your view of reality can be distorted too. so it's just a more fluent way of saying 'not accurate' or 'not good'.
 

Vacceo

Addicted to Fun and Learning
Joined
Mar 9, 2022
Messages
690
Likes
569
yes but your view of reality can be distorted too. so it's just a more fluent way of saying 'not accurate' or 'not good'.
We can get philosophical and consider that reality itself is unattaineable, hence, distortion in a baseline.

Luckily for soundwaves, it is something we can measure against a clearly defined scale.
 

Tangband

Major Contributor
Joined
Sep 3, 2019
Messages
1,143
Likes
1,054
This box is certainly just a box, and it introduces diffraction as every other. There is diffraction, not only the usual around baffled width that was already identified, you can even see it in reference axis measurement. You must not look at PIR for this, where diffraction ripple is averaged out. Cabinet depth can lessen the big dip introduced by the baffle, but no miracles. The rather calm ripple is probably due to the three way.
Also, bringing the waveguide to the edge is not enough, in a two way, there is a huge area below. And the wavefront is not one horizontal, another vertical. It is one wavefront and what happens on the vertical will leave traces in the horizontal response too.
The diffraction you can see probably (?) dont come from the box edges in this case .

In Kef R1 Meta the crossover of the midrange is way below the wavelengt of the wideness of the cabinet , at 450 Hz , - You dont need rounded sides in this construction.
The wavelength of 1 kHz is 34,3 cm . 500 Hz is the double - 68,6 cm.

My own experience building speakers with waveguides ( Hybrid active ) and active mod on jbl 530, is that using a waveguide brings much less sensitivity for diffraction , because its mainly a problem from 1,5 KHz and up . The waveguide solves this problem, and brings good directivity as well.
 
Last edited:

HeadDoc12

Member
Joined
Apr 12, 2021
Messages
30
Likes
47
Note, I am a Revel owner. I wasn't talking about sound quality. When I said product design I meant a mix of aesthetics and products that create or capture new markets. KEF is positioning itself as a quasi lifestyle brand with real HiFi credentials and killing it. In contrast, Revel doesn't have anything in the desktop, wireless, or active space. And that's where the innovations are happening.
Well, now we are talking about issues outside Revel's control. Revel is owned by Harman International, which is owned by Samsung. So, not only do you have JBL (and even Harmon/Kardan) for the categories you mentioned (though I am not a fan of JBL's loudspeakers' aesthetics compared to KEF), you also have a MASSIVE corporation that sells everything from smart toilet seats to helicopter parts (and speakers!) making all the decisions at the top.
 

changer

Active Member
Joined
Dec 4, 2020
Messages
276
Likes
207
In Kef R1 Meta the crossover of the midrange is way below the wavelengt of the wideness of the cabinet , at 450 Hz , - You dont need rounded sides in this construction.
The wavelength of 1 kHz is 34,3 cm . 500 Hz is the double - 68,6 cm.
Huh? This really appears nonsensical to me. Either a proposition of yours went missing or you have not thought this through. When the midrange driver plays a frequency spectrum from 450 Hz upwards, this band includes frequencies that are both longer and shorter than baffle width: the cause of baffle edge diffraction. Its cleary happening, as always, in the passband of the midrange, this is no exception.

With some driver topologies, where spacing is wide and summation happens late / further away from sources, the effect of diffraction on tweeter frequency response might be limited. In this case however, a coincidental drive, the effects of diffraction on the wavefront is already effecting the tweeter when the summed wavefront is building up. It is one wavefront from the very beginning, and diffraction that is leaving its traces in the lower registers also influences the response of the other, higher playing tweeter.
 

Tangband

Major Contributor
Joined
Sep 3, 2019
Messages
1,143
Likes
1,054
Huh? This really appears nonsensical to me. Either a proposition of yours went missing or you have not thought this through. When the midrange driver plays a frequency spectrum from 450 Hz upwards, this band includes frequencies that are both longer and shorter than baffle width: the cause of baffle edge diffraction. Its cleary happening, as always, in the passband of the midrange, this is no exception.

With some driver topologies, where spacing is wide and summation happens late / further away from sources, the effect of diffraction on tweeter frequency response might be limited. In this case however, a coincidental drive, the effects of diffraction on the wavefront is already effecting the tweeter when the summed wavefront is building up. It is one wavefront from the very beginning, and diffraction that is leaving its traces in the lower registers also influences the response of the other, higher playing tweeter.
The uni-Q element with midrange and tweeter are still in its own waveguide down to the crossover at 450 Hz , depending on the construction, thus lessens the risk for serious diffraction from 450 - 20000 Hz . Below the rooms schroeder freq, the soundwaves starts to behave in a completely different way anyway, and stops beaming sound forward as it does with sound- frequencies thats higher.

Below 450 Hz you also gonna start having problems with the floor bounce, SBIR and wall reflections thats probably gonna be much more audible than the baffle diffractions from this speaker in a normal listening room.

I wouldnt lose any sleep worrying about diffractions in this construction. There are other potential problems that might be audible, like the uni-Q element acting as a variable waveguide for the tweeter . This problem is much less though in this speaker because of the crossing at 450 Hz . Maybe it will move less than +-2 mm at higher spl:s ?

The crossover in this speaker is also passive, and if the coil in series with the bass unit is an ironcoil, there is a potential risk its gonna distort several % if its saturated during high spl levels in the bass. No such problems with aircoils of course and this loudspeaker might have that.

This is a good video expaining this.
 
Last edited:

changer

Active Member
Joined
Dec 4, 2020
Messages
276
Likes
207
I like your thinking, but it does not hold true. The understanding that a baffle-mounted waveguide (or horn) would isolate the particular band from the baffle is incorrect. In the case that the crossover is a fair bit higher than where diffraction has its strongest impact, as in the case of a PA speaker that has a rather wide baffle and usually a crossover closing in to 2 kHz, and where summation only is realized after a meter or so into far field, this might be a thing, and I figure this is where the idea originates from.

This is a simulation of a baffle-mounted waveguide, only showing the tweeter. Note the vertical plot is flipped upside down. The cabinet has 25 mm edge rounding, this is a significant improvement over the speaker we are talking about, the waveguide is 265 by 200 mm, a much more powerful device than the Uni-Q. Diffraction clearly occurs around baffle width (the well known peak-dip pattern that shifts location with angles,) and ripple is transmitted into higher frequencies response as a result. You must have two separate wavefronts, of which one is only established beyond baffle diffraction frequency, and that sum later to a unified wavefront, to reduce the impact of edge diffraction.

C5F4B85E-572F-4919-9C93-E33867EF3DC3.png

A2A25BF1-FA2E-4D5E-89BA-282E20BEBDB9.png

B0DCE177-A00F-4DA2-AC7F-6AA44599E67D.png
 
Last edited:

Tangband

Major Contributor
Joined
Sep 3, 2019
Messages
1,143
Likes
1,054
I like your thinking, but it does not hold true. The understanding that a baffle-mounted waveguide (or horn) would isolate the particular band from the baffle is incorrect. In the case that the crossover is a fair bit higher than where diffraction has its strongest impact, as in the case of a PA speaker that has a rather wide baffle and usually a crossover closing in to 2 kHz, and where summation only is realized after a meter or so into far field, this might be a thing, and I figure this is where the idea originates from.

This is a simulation of a baffle-mounted waveguide, only showing the tweeter. Note the vertical plot is flipped upside down. The cabinet has 25 mm edge rounding, this is a significant improvement over the speaker we are talking about, the waveguide is 265 by 200 mm, a much more powerful device than the Uni-Q. Diffraction clearly occurs around baffle width (the well known peak-dip pattern that shifts location with angles,) and ripple is transmitted into higher frequencies response as a result. You must have to separate wavefronts, of which one is only established beyond baffle diffraction frequency, and that sum later to a unified wavefront, to reduce the impact of edge diffraction.

View attachment 205163

View attachment 205164

View attachment 205165
Ok, if what youre writing is true, and if it makes sense and is audible, why didnt Kef do something about it ?
 

Zvu

Addicted to Fun and Learning
Joined
May 1, 2020
Messages
675
Likes
1,112
Location
Serbia
Kef did something about it - that's why there is Blade which practically has no front baffle but a large radius. Diffraction is always there, you just have to disperse it as much as you can until its influence on any given measured axis is so low that it becomes irrelevant.
 

mtg90

Member
Joined
May 24, 2021
Messages
40
Likes
110
Location
Illinois
The crossover in this speaker is also passive, and if the coil in series with the bass unit is an ironcoil, there is a potential risk its gonna distort several % if its saturated during high spl levels in the bass. No such problems with aircoils of course and this loudspeaker might have that.

I was recently testing various iron core inductors, it's true that once they begin to saturate distortion starts to increase and the frequency response also changes. However I was surprised how much power was really needed to saturate the coils I tested, most of them I could not get to saturate with the amp I was using sending ~400w @ 4 ohms through them. Only the smallest few iron core coils I had saturated at power levels lower then that. If they use an iron core coil and it's properly sized the woofer will run out of xmax or reach its thermal limits before any saturation occurs.
 

gags11

Senior Member
Forum Donor
Joined
Feb 8, 2019
Messages
320
Likes
472
Does any one know if the meta uni-q driver is the same in the reference and lower tier meta models?

I would like to know if this new driver can be ordered from KEF as a part. If any one knows part number for this driver, please share.

The distortion and compression profile looks great. If the price of the drivers is not ridiculous, I entertain the idea of swapping the drivers on my R11s.
 

HarmonicTHD

Addicted to Fun and Learning
Forum Donor
Joined
Mar 18, 2022
Messages
528
Likes
544
Does any one know if the meta uni-q driver is the same in the reference and lower tier meta models?

I would like to know if this new driver can be ordered from KEF as a part. If any one knows part number for this driver, please share.

The distortion and compression profile looks great. If the price of the drivers is not ridiculous, I entertain the idea of swapping the drivers on my R11s.
Contact KEF directly, probably quickest way to get a definitive answer including a price, I suppose.
 
Top Bottom