Home Test: Kef LS50 vs B&W CM

[niceshoes]

I've had an opportunity to do a side by side comparison of the LS50 and CM8 (s1) at home for a while. These are popular speakers so I thought I'd share my thoughts

It may seem odd comparing a 3-way floorstander with a 2 -way monitor, but they actually have a lot in common. They both have an unusually high -3db point, followed by an especially gradual roll off in bass to the -6db point. They're both very clear and precise speakers with solid cabinets, and are reputed for reproducing vocal music. And actually they sound unexpectedly similar. Switching between them it was surprisingly possible to forget which pair was playing.

Equipment was a rotel ra-11 being fed digitally over AirPlay. A combination of 256kb/s AAC and 1411kb/s ALAC. I have a subwoofer but I'm not using it here.

Here's how I would describe the differences (slight as they were):

CM8: clear and precise, yet warmer and fuller, more bass extension, more laid back, slightly more relaxed in the treble. Wider sound stage.

LS50: very clear and precise. Amazingly sharp imaging. More revealing. More analytical and less "colour". More restrained but also more detailed bass. More emphasised treble. Forward, fast and at times harsher or more fatiguing (especially with string instruments). A fraction less sensitive/loud.

I'm also tempted to say that the ALAC files sounded great on both pairs, while the lower bitrate AAC were very slightly less enjoyable on the LS50, but I need more listening time to be certain of this point.

I actually bought the ls50 for late night bedroom listening while i go to sleep, but they're so forward and revealing it's not the most relaxing speaker to listen to, and the cm8 might be better for this purpose. On the other hand floor standing speakers look quite odd in the bedroom.

It's possible a more powerful amp might address the occasional harshness in the ls50 compared to the cm8. Or perhaps this is simply an inherent difference in the speakers?

 

[Ricardojoa]

Maybe some acoustics panels can address some of the harshness by reducing the refective sound.

 

[niceshoes]

Yes the listening room was mostly hard mdf/plasterboard walls with solid timber floor. 4m x 7m. So there is no doubt a lot of room gain here.

That said, both pairs of speakers were in the same position in the same room so for the sake of comparison it's level playing field. If harshness was an artefact of the listening room you would expect it to be present more or less with any speaker.

 

[tyhjaarpa]

I have not directly compared those speakers, but what I have heard LS50 they are really accurate and nice sounding speakers all around and I would pick them over those B&W, not saying those B&W are bad but I prefer the LS50.

 

[niceshoes]

I have not directly compared those speakers, but what I have heard LS50 they are really accurate and nice sounding speakers all around and I would pick them over those B&W, not saying those B&W are bad but I prefer the LS50.

Yes, the LS50 are extremely accurate speakers. Unlike anything else at this price point that I've heard.

When I described them as harsh I didn't mean to say they were distorting. Only that compared to the CM they are more forward, fast and immediate.

It amazes me that even though the cm8 has an excellent FST mid driver, it still doesn't quite much the accuracy of the human voice of the LS50 2 way design.

 

[tyhjaarpa]

Yes, the LS50 are extremely accurate speakers. Unlike anything else at this price point that I've heard.

When I described them as harsh I didn't mean to say they were distorting. Only that compared to the CM they are more forward, fast and immediate.

It amazes me that even though the cm8 has an excellent FST mid driver, it still doesn't quite much the accuracy of the human voice of the LS50 2 way design.

I think you need some room treatment with the LS50 then. I have heard them in big demo room that had huge curtains with fitted carpet floor and they filled the big room with no problems at all, I was actually surprised how well they filled the big room as the speakers itself are so small. Even tho they played really loud to fill that big space they sounded really nice and clear with no fatigue, it was really pleasing to listen to them.

 

[Ponzio]

I fall asleep to my LS50's every night in my bedroom and can't detect any harshness whatsoever. For that matter I don't know anyone who be able to detect any harshness at that lower volume level besides a dog. Even when I crank them up to -6 dB on my Yamaha RX-V2600 they're still as clean & uncolored as a whistle. I'd have to agree with tyhjaarpa sentiments.

 

[niceshoes]

I fall asleep to my LS50's every night in my bedroom and can't detect any harshness whatsoever. For that matter I don't know anyone who be able to detect any harshness at that lower volume level besides a dog. Even when I crank them up to -6 dB on my Yamaha RX-V2600 they're still as clean & uncolored as a whistle. I'd have to agree with tyhjaarpa sentiments.

I should clarify that by harshness I don't mean distortion. I only meant that compared to the B&W CM the LS50 is more forward, detailed and revealing, and this makes it a slightly more fatiguing listen in comparison.

But this shouldn't surprise as the LS50 is designed in the spirit of a studio monitor which is supposed to be revealing and detailed. So I'd say it's a design choice rather than a flaw.

 

[tyhjaarpa]

I should clarify that by harshness I don't mean distortion. I only meant that compared to the B&W CM the LS50 is more forward, detailed and revealing, and this makes it a slightly more fatiguing listen in comparison.

But this shouldn't surprise as the LS50 is designed in the spirit of a studio monitor which is supposed to be revealing and detailed. So I'd say it's a design choice rather than a flaw.

I referred to fatigue in my last post and I haven't experienced any with LS50. Room treatment can round the highs as well and reduce the fatigue. Also using room correction from receiver can help to flatten the response and help with fatigue. To get distortion from LS50 you would have drive them really hard, in small room your ears would most likely hurt before distortion in my experience as they can fill such big spaces without issues.

 

[PENG]

That said, both pairs of speakers were in the same position in the same room so for the sake of comparison it's level playing field. If harshness was an artefact of the listening room you would expect it to be present more or less with any speaker.

Sorry but I have to ask, how can they be in the same position if they are side by side? I have plotted frequency response curves many times and I can assure you that even a few inches or a few degrees of toe in could made quite a difference from a fixed listening position. Also keep in mind that the two speakers likely need different placemence for them to sound the best from your listening position so ideally you really need to find the best position for each of them in order to do a fair comparison. Now if you are talking about major audible difference then I would not have asked any questions. You seem to be saying that the two speakers sound more similar than not, so even little details could become important factors that might have affected the outcome.

People put a lot of emphasis on subwoofer placements, to the extent that they would crawl them to find the sweet spot. From my experience, even little ones like the LS50 are also affected by placement, just to much lesser extent.

 

[niceshoes]

I referred to fatigue in my last post and I haven't experienced any with LS50. Room treatment can round the highs as well and reduce the fatigue. Also using room correction from receiver can help to flatten the response and help with fatigue. To get distortion from LS50 you would have drive them really hard, in small room your ears would most likely hurt before distortion in my experience as they can fill such big spaces without issues.

Fatigue is definitely a subjective measurement.
What I meant is that the LS50 is very detailed and analytical, and that this abundance of detail for me can be a sensory overload (especially with guitars and violins) which is more fatiguing than the B&W. Others may not feel at all fatigued by this amount of detail.

Agree that room correction would make a big difference, especially with my hardwood floors.

 

[niceshoes]

Sorry but I have to ask, how can they be in the same position if they are side by side? I have plotted frequency response curves many times and I can assure you that even a few inches or a few degrees of toe in could made quite a difference from a fixed listening position.

Ok you got me - the CM8's were positioned an inch outside the LS50's, so that may help the CM8's with sound stage and perhaps help the ls50 with imaging.

They were both positioned well away from walls though, and the kefs are on heavy steel stands filled with sand, decoupled from the stand with blu tack.

 

[PENG]

I fall asleep to my LS50's every night in my bedroom and can't detect any harshness whatsoever. For that matter I don't know anyone who be able to detect any harshness at that lower volume level besides a dog. Even when I crank them up to -6 dB on my Yamaha RX-V2600 they're still as clean & uncolored as a whistle. I'd have to agree with tyhjaarpa sentiments.

Ok you got me - the CM8's were positioned an inch outside the LS50's, so that may help the CM8's with sound stage and perhaps help the ls50 with imaging.

They were both positioned well away from walls though, and the kefs are on heavy steel stands filled with sand, decoupled from the stand with blu tack.

Again, I did not mean to challenge your findings as I was fully aware of what you said "And actually they sound unexpectedly similar. Switching between them it was surprisingly possible to forget which pair was playing."

The LS50s are probably more neutral, whereas the B&W may be more lay back in the frequency range you are sensitive to. We all have our own preference, so accurate does not always equal better sound quality to a lot of people. It is only the "harshness" that you described got me wondering what was actually happening. Did they sound harsh even at lower listening level?

 

[Ponzio]

Obviously some people are more sensitive to higher frequency than others and u may fall in that category. I have a friend that claims his old Boston bookshelves are more "natural" than my LS50's. No amount of room treatments will change ur tonal preferences. I can't speak to the B&W CM-8's but it sounds like u would prefer more laid back speakers. Quite a few British brands fit that bill, besides the B&W's, like Wharfdale, modern day Epos models, etc. good luck whatever u choose.

 

[PENG]

Subjective reviews are just all over the place, here's what a professional reviewer said about the CM8:

"Imaging while being ruthlessly precise and accurate, is also fairly narrow. I've owned many pairs of B&W speakers over the years and this seems to be a consistent trait. The sweet spot is fairly narrow and suitable to just one listener. Moving one's head eight or more inches away from center results in a near complete collapse of the stereo image. When in the sweet spot you will be treated to one of the most accurate and realistic imaging at this price. Instruments are anchored in space with a crystal clear picture of where every sound is emanating."

By the way, the OP's room is 4MX7M, that's quite large for the LS50. The CM8 is 3 dB more sensitive, both speakers dip to around 3 ohms according to specs.

The RA-11 is rated 40WPC into 8 ohm, that seems a little under power for the room size especially for the LS50 that in theory may need twice as much power than the CM8 for a fair comparison. I suspect if the OP would do another comparison at lower SPL, the result may change.

 

[niceshoes]

Subjective reviews are just all over the place, here's what a professional reviewer said about the CM8:

"Imaging while being ruthlessly precise and accurate, is also fairly narrow. I've owned many pairs of B&W speakers over the years and this seems to be a consistent trait. The sweet spot is fairly narrow and suitable to just one listener. Moving one's head eight or more inches away from center results in a near complete collapse of the stereo image. When in the sweet spot you will be treated to one of the most accurate and realistic imaging at this price. Instruments are anchored in space with a crystal clear picture of where every sound is emanating."

By the way, the OP's room is 4MX7M, that's quite large for the LS50. The CM8 is 3 dB more sensitive, both speakers dip to around 3 ohms according to specs.

The RA-11 is rated 40WPC into 8 ohm, that seems a little under power for the room size especially for the LS50 that in theory may need twice as much power than the CM8 for a fair comparison. I suspect if the OP would do another comparison at lower SPL, the result may change.

I would agree with the observation that the cm8 has a narrower sweet spot. The LS50 has a very wide sweet spot... You can just about walk around the room and the stereo image is good anywhere.

I also acknowledge the ra-11 is a bit light for the LS50. I have a marantz receiver sr6007 which claims 110wpc in stereo mode so will experiment with that and see what difference there is.

4mx7m is large, but the speakers are backed up 0.5m in from the longer wall, so only have about 3m to the listening position by the opposite wall.

 

[PENG]

I would agree with the observation that the cm8 has a narrower sweet spot. The LS50 has a very wide sweet spot... You can just about walk around the room and the stereo image is good anywhere.

I also acknowledge the ra-11 is a bit light for the LS50. I have a marantz receiver sr6007 which claims 110wpc in stereo mode so will experiment with that and see what difference there is.

4mx7m is large, but the speakers are backed up 0.5m in from the longer wall, so only have about 3m to the listening position by the opposite wall.

The 6007 should give you about 2 to 3 dB more. If you listen at average spl of around 75 to 78 dB then you should be okay with either one. In that case then I guess you can try fine tuning the sweet spot for the LS50, or it could still be that you just prefer some roll off in the frequency range you are sensitive to. I hope you don't give up on them too soon.

 

[niceshoes]

The 6007 should give you about 2 to 3 dB more. If you listen at average spl of around 75 to 78 dB then you should be okay with either one. In that case then I guess you can try fine tuning the sweet spot for the LS50, or it could still be that you just prefer some roll off in the frequency range you are sensitive to. I hope you don't give up on them too soon.

I certainly won't give up on them. Perhaps my OP sounded overly critical of the LS50 but overall I think they're incredible speakers. There's nothing else quite like it (that I'm aware of) in the price point.
Over the next few days I'll try both in a different room, with a different amp and with a subwoofer and see how that goes.

 

[niceshoes]

A quick follow up on this.

I have now tried the LS50 with my SVS NSD-12 subwoofer. I tried crossing over at various points around 50 - 80hz, and with a few different volume levels. The LS50's were running full range. While the subwoofer added some fun bass to the music I was never able to fully integrate the subwoofer in a way that didn't detract from the Kef's level of bass detail. After 1 hour of trying I gave up on the subwoofer.

Regarding the LS50 vs the CM series, I saw stereophile has already written on this subject. Anyone reading this thread might be interested so I'll copy what they said here. Largely I would say it agrees with my observations on the CM being more laid back in the treble and with better bass extension:

"Next up was the identically priced but somewhat larger Bowers & Wilkins CM5 (reviewed by Robert J. Reina elsewhere in this issue). The CM5 was noticeably more sensitive than the LS50, and had a lighter, airier balance, but was also slightly laid-back in the treble. Both speakers had very clean upper-frequency presentations, though the CM5 was less forgiving of ticks on LPs. However, the B&W's bass was usefully more extended than the KEF's.

Which speaker you will prefer will depend very much on your tastes in sound and music. Classical orchestral, solo piano, and vocal recordings were better suited to the more neutrally balanced KEF, and rock to the B&W, with its more laid-back low treble and more extended low frequencies. On balance, I preferred the LS50."


Read more at http://www.stereophile.com/content/kef-ls50-anniversary-model-loudspeaker-page-2#TqkJTUvzyGiJ91hJ.99

 

[TheWarrior]

A quick follow up on this.

I have now tried the LS50 with my SVS NSD-12 subwoofer. I tried crossing over at various points around 50 - 80hz, and with a few different volume levels. The LS50's were running full range. While the subwoofer added some fun bass to the music I was never able to fully integrate the subwoofer in a way that didn't detract from the Kef's level of bass detail. After 1 hour of trying I gave up on the subwoofer.

Regarding the subwoofer, this may be a situation of having loudspeakers that are performing at such a level, that only a well built, low distortion subwoofer will suffice. Its a matter of how quickly that woofer stops moving!

If I could offer the suggestion of playing some specific male and female voices, and really try and listen to when the song reaches a chorus line, and the voice goes in to crescendo. This is a great way to listen for audible break up, or compression, that is repeatable! If something sounds very strange, repeat and see if that 'strange thing' happens twice.