KEF LS50 Meta Review (Speaker)

[diablo]

> you need to have a beefy amplifier to drive them.

@amirm how did you come to that conclusion when you say that there's 100% distortion at even 96db. They're 85db sensitive at 2.83v. Wouldn't that mean at ~20w you'd be hitting those distortion levels?

KEF doesn't even recommend more than 100w so I'm sort of confused.

I've noticed that Amir often says that when the impedance dips below 4 ohms at some point. So that may cause a problem with some amplifiers or AVRs.

 

[Dennis_FL]

Yikes

Well, my information was wrong. It was the entire driver. And it was slighly damaged in shipping and I'm waiting for another one.

 

[Mike_Trueman]

My new KEF LS50 Meta speakers arrived yesterday. This is my first experience with KEF and i owned a lot of bookshelfs speakers.
The listening room is 42m2 which is perfect for these speakers. I am using them at nearfield @ 1m on my PC desktop most of the time but also listening 3 or 4 meter away further in to the room.
I never believed in the KEF hype but wow these speakers are so good for me that they are going to stay. I regret not buying them sooner...

Here is what i like about them:

• Studio monitor sound
• Music sounds lively and engaging
• Lots of detail and good treble
• Brings emotion in voices that i never heard before.
• Tight and clean base

I am using the high pass filter on my amplifier set @ 90hz which seems to be perfect. Also i am not even using Dirac (full license) because i am enjoying the music so much, maybe later. They sound best with a subwoofer and a HPF set between 80hz and 100hz. They even sound good when put close to a wall (7"). I never go over 90dB when listening to music, normaly around 85dB max.

(These are not speakers for people who love warm laidback sound)

Edit: uploaded a test video of my setup with subwoofer OFF. Speakers are 7" inch off the wall

 

[Punchy_Power_Cat]

how did you come to that conclusion when you say that there's 100% distortion at even 96db

The distortion in the LS50Meta at high volume is originating from the woofer. How? Because it is a coax design. The tweeter is a circle embedded into another bigger circle, the woofer. As the woofer starts to "bounce" out of his socket it pushes/shovels the soundwaves that originate from the tweeter with its own soundwaves sort of away. It basically creates ripples as it pushes/hits the tweeter soundwaves each time the base knocks. This is what those diamonds-shaped engravings in the woofers baffle are for to counter. Those diamonds are supposed to keep the harmonics of the ripple those base knocks produce as clean as possible. While this may do something it is not sufficient. The solution is as simple as Amir already suggested in the review. Do not let that woofer visibly bounce!

This practically means that you need to run the LS50 Meta with a high pass crossover if you want to a)play them clean loudly and/or b)unleash their full potential even at low vol. Kef has them layed out for 80Hz HP but some even drive them from 100-120hz which allows them to play even louder. 80Hz should be fine up to ~96db tho which is the maximum 96% of people listen music to.

Why b)?
I always wondered why KEF has a crazy subwoofer-esque in room response of 26hz in the specs with the LS50 Metas. They do not seem to bother applying a low cut on their own. You need to apply a cut off at about 47Hz which is the lowest they should attempt to play. If you send them a full range signal they will even at low volume somehow distort due to their drivers being somehow "shattered" of the very low frequencies they cannot handle. My pair sounded much more open after a cut @50hz without loosing a hair of base. In fact the base got a lot more refined, layered and enjoyable. I thought they sounded great before I realized all of this, but the truth is that they were "boomy" the opposite of layered but the boomyness was quite pleasant because they do have some sincere hammer-knock. But now knowing what they can really do I must declare a sincere recommendation:

DO NOT EVER GIVE THE LS50 META A FULL RANGE SIGNAL !

-The least and minimal effort thing you should do is to use software EQ in the music player of your choice to cut all frequencies below 50Hz with a steep slope. You will thank me.
-The best you can do is to High Pass Filter them at 80Hz or even higher. Of course you will need a sub to supplement. This will allow them not only to unleash the full potential of their drivers but will also free them up to play very loud, maybe even close to a 100db@1m with low distortion.

Some final remarks:
Amirs review has shown a perfect, I mean like 98,3% or something accurate "in room response" for the following frequency window:

• ~150Hz - 650Hz (perfection! ~98%)

from there it is still very impressive

• ~650Hz - 1000Hz (very good ~88%)

with some not very profound and EQ-able problems from

• ~1000Hz - 7000Hz (still quite good overall but some dips ~75-85%)

and again ending in close to perfection

• ~7000Hz - 20000Hz (close to perfection ~95%)

Human vocals (male and female) are @95% of tracks within the first row, therefore being perfectly represented by the LS50 Meta. Maybe except for those rare female singers who can break glasses with their voices. Just in case you would want to hear those they can reach up to 900Hz and would in their absolute highest pitch be slightly distorted by the Metas (how sad ).

Well, and this is it. How much more do you want? There are two things exciting about music. The vocals and the base. For the latter you will have to look for a sub, but for the former you will not find a speaker up to around 99db@1m that beats the fifties (high passed). Even with internal DSP it is very hard, actually close to impossible to beat them.

edit: Almost forgot. There is another thing. You can screw and fasten them onto a plate! What this means is that you can add "stiffness" to their enclosure depending on the heftyness of the stand you mount them on. They are already quite stiff and heavy but you can turn them into concrete corpus-vibrations-wise. Of course this will affect their performance positively even further.

 

[MNMLSM]

Maybe not exactly the right spot for the question. Does anybody know why the KEF KC62 subwoofer (Location Germany) got so expensive in the last months?
I want to add the sub to my KEF LS50 Metas, when I was looking for the sub, like half a year ago, the price was about 1200€ or am I missing something?

 

[CJH]

Can anyone recommend an ultra low noise HP analogue crossover (80-200Hz) to use for my LS50 Metas in my current system of LA 90s in mono, Cyan 2 (DSD) and Rythmik L12 subs. Tried a DBX 234x and it simply does too much sonic damage for consideration.)
CJH

 

[sapphari]

Maybe not exactly the right spot for the question. Does anybody know why the KEF KC62 subwoofer (Location Germany) got so expensive in the last months?
I want to add the sub to my KEF LS50 Metas, when I was looking for the sub, like half a year ago, the price was about 1200€ or am I missing something?

This is the price history in the US. It does look like it jumped up a bit recently. Don't know why, but I could guess....

I've been considering it lately but am probably going to go with the SVS 3000 micro. To me the price difference isn't worth it.

 

[digitalfrost]

And here is germany. It was indeed available for 1200€ a couple of times, sometimes even cheaper. Probably tariffs + inflation.

@MNMLSM If I were you I'd set an alarm on mydealz.de and wait for a deal - if you can wait.

 

[Mike_Trueman]

Ok, i finally i moved my tower PC under the desk to get more space.
The sound is much better now that the LS50 Meta's have more distance from eachother and from my ears.
Not much more i can improve i think? Maybe some sound isolation panels ... but i do not listen to loud volume levels.

Before and after picture:

 

[digitalfrost]

Ok, i finally i moved my tower PC under the desk to get more space.
The sound is much better now that the LS50 Meta's have more distance from eachother and from my ears.
Not much more i can improve i think? Maybe some sound isolation panels ... but i do not listen to loud volume levels.

Before and after picture:

You need to raise the tweeter to ear height. It's easy to test. Play some music, and lower you head, you will notice significant changes. I see you already have the IsoAcoustic stands. Why do you not use the higher version? I believe they come with two different heights.

 

[Mike_Trueman]

You need to raise the tweeter to ear height. It's easy to test. Play some music, and lower you head, you will notice significant changes. I see you already have the IsoAcoustic stands. Why do you not use the higher version? I believe they come with two different heights.

The isoacoustics aperta's are on an angle, if you zoom in on the picture you can see it better. They are on ear level

 

[kyuu]

Also, given you have plus or minus 50-degrees to work with vertically before you get significant differences in the response, it's almost certainly fine as-is even if your ears aren't quite on-axis.

 

[Punchy_Power_Cat]

Maybe not exactly the right spot for the question. Does anybody know why the KEF KC62 subwoofer (Location Germany) got so expensive in the last months?

Support our french neighbours and buy the Focal Sub One instead. If you don't need super high output, it should be as clean as the KC62.

 

[phoenixdogfan]

You should look into SVS subs, the OG SB 2000 in particular. Though discontinued I see it on sale in the warehouse for $600-650 from time to time. That's for a brand new 12" powered sub that comes equipped with both a high and low pass filter that's capable to playing 25 hz at 100 db with standard accepted distortion measures. With 2 of them, you'll easily be getting 20 hz at 100 db in most listening rooms for the price on one EP-62 on sale (if you can find it).

 

[MNMLSM]

Thanks for the responses!

To be completely honest, I love the design of the KC62 in white. It was always my dream to own a pair of LS50s and the KC62, saw the marketing picture when it launched and I was like "I have to get this trio one day".
The time has finally come but I'm patient I will wait for the right deal!

 

[Punchy_Power_Cat]

Ok, i finally i moved my tower PC under the desk to get more space.

Please at least put the foam inlays into the openings. This is a nightmare setup bass wise with them so close to the wall and even in a corner. Give them a high pass @90Hz or higher and in addition lower bass volume with an EQ beginning from -3db@110Hz down to -9db@60Hz to -12db@32Hz. Those numbers are somewhat researched in a comparable setting, however without that nasty corner. You might have to go even lower than this.

 

[Mike_Trueman]

Please at least put the foam inlays into the openings. This is a nightmare setup bass wise with them so close to the wall and even in a corner. Give them a high pass @90Hz or higher and in addition lower bass volume with an EQ beginning from -3db@110Hz down to -9db@60Hz to -12db@32Hz. Those numbers are somewhat researched in a comparable setting, however without that nasty corner. You might have to go even lower than this.

Thanks for the feedback!
I already have the high pass filter on 90hz and the speakers are 6" or 15cm from the wall. Also the foam plugs do not do much if you use the HPF. (see graph)
I listen every day and enjoying the music. I have a full license for Dirac but not using it atm because for now i am happy, maybe later.

 

[Mike_Trueman]

No I didn't misunderstand you. I explained that by the time the woofer is moving that much, the distortion it generates is much of a concern than whatever tweeter is doing. This was certainly the case in my listening tests. Once you see the cone moving any appreciable amount -- which is easy to observe given its shiny surface -- the bass is already getting distorted.

Is this movement to much? This is how far i go max.

I removed the audio from the test video.

 

[Punchy_Power_Cat]

Your listening position is an acoustic nightmare anyway, I would invest into thick carpet, a thick fabric to cover that nasty window and maybe close the nasty corner with some round shaped foam (if you really can't move the entire spot). You would need to a)DSP/dirac heavily and reduce the base of the LS50 heavily to get some decent tunes out of there. The amout of woofer movement posted in the video is already too much.

This is how I tuned them in addition to the HP@90Hz. Yes, they will loose a good amount of base but this is what you have a good subwoofer for.

 

[Heinrich]

> you need to have a beefy amplifier to drive them.

@amirm how did you come to that conclusion when you say that there's 100% distortion at even 96db. They're 85db sensitive at 2.83v. Wouldn't that mean at ~20w you'd be hitting those distortion levels?

KEF doesn't even recommend more than 100w so I'm sort of confused.

This can be remedied. The statement about distortion relates to the case that the all input power is at the specified frequency. This results in quite high values for bass. When listening to music, the input power is distributed over many frequencies, leaving less for the worse bass.

e.g. 6 watts at 50Hz, and another 50 watts between 200 and 20kHz - Mostly it is the other way round, though.

However, with such small speakers it is also important to bear in mind that the bass is quite thin, so the distortion starts much earlier than the average measurement level would suggest. The measurement method doesn't reflect the actual capabilities.

The whole thing is a bit more complicated, but it's not rocket science. As a result, you are regularly in an extraordinarily bad position with such tiny boxes. It wasn't worth it for me, it was really daunting.