KEF LS50 Bookshelf Speaker Review

[Audio Monkey]

To me all box speakers sound like.... boxes. I'll take my Quad ESL-57 speakers or my tri-amped Magneplanar MG 3.6's over ANY monkey coffins. Open baffle GR research / Rhymik servo subs complete the boxless system.

Your subs aren't in boxes?

To date, I've heard electrostatic speakers and and planar headphones, but not planar speakers. Some day perhaps...

 

[Cahudson42]

There is bound to be a severe directivity mismatch between these two drivers and no amount of DSP or enclosure modification can fix that.

At $22 each, you can economically, per channel, DSP a stacked pair, a vertical or horizontal stacked pair with various polar orientations between them, a vertical side-by-side or horizontal side by side - again with various orientations between them.. ad nauseam

You need a miniDSP 2x8, and 8 amp channels maybe 4 $9 Kinters...
Kinter MA170 12V 2 Channel Mini Digital Audio Power Amplifier for Car or Mp3 https://www.amazon.com/dp/B007TUSXEY/

'Don't know until you try..'. and measure!

 

[LTig]

I must say I'm a bit disappointed regarding FR. First I thought we see the same drop in bass as with the KH80 due to (possibly intentional) compression but then I realized that it is a passive speaker, and it matches with other reviews.

Wasn't the LS50 marketed as the sucessor of the LS3/5a? Difficult to believe that someone who likes the sound of an LS3/5a would be happy with the LS50. Well, DI looks better than the Harbeth so a little EQ should help to smooth the high mids, but for the bass only a sub (or a clever position in the room) will help.

 

[617]

Not an especially impressive speaker but KEF did a hell of a job getting smooth treble out of that coaxial driver. No crazy cancellations or bullshit. I'd expect their larger speakers to be quite good if they prioritize neutrality.

Also, Amir, the directivity sonograms are the standard among diyers so thanks for continuing to include them; the one degree resolution is absolutely sumptuous.

 

[DeeJay]

Hi Amir,

CSD does not look correct.

Also, could you do linearity measurements please?

 

[NTK]

Well, the input signal is OK. But ideally you would want to conduct additional tests at higher output, I agree.

I was more curious at what point in space the Klippel derived the distortion measurements from. It doesn't look like it's as simple as "nearfield", it seems.

The perplexing thing is that the FR in the THD measurement results should mimic the on-axis FR. In the case of what Amir posted it does not. It looks more like the sound power (even though it obviously is not). You can see what I mean in this example (scroll down about halfway).
https://web.archive.org/web/20180209082123/http://medleysmusings.com/dyn-audio-esotar²-430-midrange/

View attachment 47804

Before anyone gets their panties in a bunch ... I AM NOT SAYING THE DATA IS WRONG. I am simply asking how it is measured. If we don't know that's fine. Just say so. I can email my contacts at Klippel directly and ask if necessary.

I don't know. Your guess is as good as mine. Asking Klippel will get us a definitive answer.

 

[MZKM]

I must say I'm a bit disappointed regarding FR. First I thought we see the same drop in bass as with the KH80 due to (possibly intentional) compression but then I realized that it is a passive speaker, and it matches with other reviews.

Wasn't the LS50 marketed as the sucessor of the LS3/5a? Difficult to believe that someone who likes the sound of an LS3/5a would be happy with the LS50. Well, DI looks better than the Harbeth so a little EQ should help to smooth the high mids, but for the bass only a sub (or a clever position in the room) will help.

The official name is KEF LS50 Mini Monitor.
So, they don’t outright say it, but that means you should be using a sub (or not if you are in an apartment/duplex, as to not annoy neighbors).

 

[MZKM]

Hi Amir,

CSD does not look correct.

Also, could you do linearity measurements please?

SoundStage/NRC did a linearity measurement (76dB to 96dB @1m anechoic):

 

[Sancus]

It seems somewhat notable that the LS50W improve bass significantly. It's still nothing to write home about, but at least the 50-100hz region is decent instead of poor.

They're quite a bit more expensive than the passive version in the US, unfortunately. Unusually, in Canada they're the better bargain(~2000 CAD or $1500 USD), I would say.

 

[Xyrium]

Amir, the bass was probably slightly present, but masked by that rising mid-high freq. response and the distortion that it produces below 100Hz. These are still very good for vocals, if that's your thing. For any music with a beat, Revel m106 is better in this price range...IMVHO.

What were they thinking, dropping the low frequencies that early? I have a hard enough time integrating a sub as it is, never mind having to run one up that high (above 5oHz), regardless of xover slope.

I may have missed it, what amplifier is used to test the passive speakers?

 

[NTK]

Amir, the bass was probably slightly present, but masked by that rising mid-high freq. response and the distortion that it produces below 100Hz. These are still very good for vocals, if that's your thing. For any music with a beat, Revel m106 is better in this price range...IMVHO.

What were they thinking, dropping the low frequencies that early? I have a hard enough time integrating a sub as it is, never mind having to run one up that high (above 5oHz), regardless of xover slope.

I may have missed it, what amplifier is used to test the passive speakers?

Please see this post.

 

[aarons915]

I must say I'm a bit disappointed regarding FR. First I thought we see the same drop in bass as with the KH80 due to (possibly intentional) compression but then I realized that it is a passive speaker, and it matches with other reviews.

Wasn't the LS50 marketed as the sucessor of the LS3/5a? Difficult to believe that someone who likes the sound of an LS3/5a would be happy with the LS50. Well, DI looks better than the Harbeth so a little EQ should help to smooth the high mids, but for the bass only a sub (or a clever position in the room) will help.

I've been using the LS50 for close to 2 years now and I've always thought they sound very good but they definitely need some EQ in the 2-5k region to smooth out the highs. As Amir stated earlier, the klippel measures the entire speaker in various increments so the listening window won't have the port output applied, in room I find the LS50 to have similar bass as other smallish speakers with a 5" woofer. They definitely still need subs though, I've never heard anything that sounds like IMD distortion out of them but I still try to minimize cone excursions since 2-way coaxials are more susceptible to it than other speakers.

I totally agree the Spin isn't very good, I can't explain why they sound so good to my ears and I've compared them level-matched and blind to the Revel M105, which has one of the best looking Spins I've seen.

 

[maxxevv]

The axis in 2-d Polar plot pointed up a few degrees at 20 kHz from what I recall.

This is not easy business. You have to align a microphone and poke it into the tweeter without going into the tweeter. One wrong move on axis control and instead of down, you have be going left and you go right into the driver! So I can only risk it so much for getting the microphone positioned right.

Then there is the business of pointing a speaker at 90 degrees to the microphone. With the odd shapes of speakers, there is no good way to do this. I try to center them but I am not accurate to one or two degrees, that's for sure.

Add to that. I noticed that some speakers look like (by eye observation, but they may be optical illusions if they are actually not) they have a tweeter plane that's not aligned as perpendicular to the base of the speakers. In that they are tilted to a marginal angle off the vertical front facing plane.

That makes it even trickier when you want to align the microphone to the axis of projection from the tweeter.

 

[MZKM]

distortion that it produces below 100Hz.

5% THD in the bass is not audible (oddly, SoundStage measurements show 10% THD @ 100Hz).

 

[Xyrium]

I've never heard anything that sounds like IMD distortion out of them but I still try to minimize cone excursions since 2-way coaxials are more susceptible to it than other speakers.

I was under the impression humans can't discern IMD or THD specifically. Are you literally able to discern when you are hearing IMD, meaning, what frequencies are being impacted by it and thus, what instruments?

5% THD in the bass is not audible (oddly, SoundStage measurements show 10% THD @ 100Hz).

Indeed, I have even seen studies that indicate higher percentages are "tolerable", but that 5dB drop after 100Hz can't be the only reason why most listeners (mags and otherwise, which I'm sure everyone has read repeatedly already) have reported this speaker to sound anemic, could it?

 

[aarons915]

I was under the impression humans can't discern IMD or THD specifically. Are you literally able to discern when you are hearing IMD, meaning, what frequencies are being impacted by it and thus, what instruments?



Indeed, I have even seen studies that indicate higher percentages are "tolerable", but that 5dB drop after 100Hz can't be the only reason why most listeners (mags and otherwise, which I'm sure everyone has read repeatedly already) have reported this speaker to sound anemic, could it?

No I've never heard anything that could resemble IMD distortion but I've always used 90-100Hz high passes on them with a 4th order slope and my max volume is like 85db at the listening position. IMD is supposed to be much more audible than THD from the few studies I've seen that compare them though.

 

[phoenixdogfan]

I have a pair of these. With a sub, they are awesome.

Have them with an SVS SB2000 and Dirac Live. I have a small room and listen in the near field along with a 165 WPC amp, and they are a very good performer under these circumstances,

 

[mitchco]

Thanks @amirm . The H and V contour (polar) plots look good and my ears agree KEF did a great job with the cabinet design and voicing. KEF has a nice design doc about these attached. My nearfield measures, with no gating, look similar too:

Confirm that they roll off pretty quickly at 100 Hz and down -10 dB by 40 Hz. This is in the same room where I can get down to -3 dB at 6 Hz with subs. A pair of (sub)woofers work well with these speakers, mind you 80 Hz XO point is pushing it as you may get a hole there as the LS50's struggle to make to 80 Hz. 100 Hz would make a better XO point (I have tried, 80, 90, 100 Hz), but need to keep the subs close to the LS50's. Rythmik L12's work really well with these, but I would love to hear a pair of Rythmik F8's paired with these and a much higher (woofer level) XO point, like 150Hz or even 200 Hz.

While the voicing is a little forward on axis, a wee bit of eq can straighten that out np. I personally love the voicing on these, but after I reviewed Purifi's PTT6.5" woofer in an eval kit, the Purifi woofer smokes the LS50 woofer/midrange driver with real extended response to 32 Hz, go considerably louder, with a lot less distortion. It is not even close when compared side by side and I own the LS50's. I hope you get a chance to measure one of Purifi's eval kits...

 

[laudio]

I've been waiting for this review.

"no bass to speak of" probably sums it up.

Bring on the good stuff!

 

[twofires]

Matches my experience of KEFs generally - light on bass (even my Q700 towers), boosted (but very clear) mids, and need a truck tonne of power to sound their best.

Based on this, I'm looking forward to seeing Dynaudios tested. I'm expecting a mid bass jump, flat everywhere else on axis, less good off axis.