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KEF LS50 Bookshelf Speaker Review

BYRTT

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I have found my LS50's work best with the crossover to the subs a little higher than 100 hz. Another forum member running a very similar system also uses 100 hz and he is considered to be an expert around here.
Thanks, should you ever stumple over whatever quality woofer that can cover 200Hz area and down situated right below LS50 then will imagine LS50 performance as satelite will really improve because band coverage get lifted above free air and combined enclosure impedance resonance area, problem often real world is get a clean symetric Linkwitz Riley cut out in acoustic domain at those frequency in a indoor enviroment, slopes seen below is of 2nd/4th/8th order Linkwitz Riley and even the 2nd order one is within bandwidth reach of LS50 coverage.

Ron_Texas.png
 

aarons915

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@QMuse I would be curious to see your 5 filter PEQ for the LS50, similar to what you did for the Sony. Starting the correction from high enough to get iut of the room impact.
Not Qmuse but I've compared PEQs based on the ASR and Soundstage listening windows and I prefer the Soundstage as it seems to emphasize the 2k resonance, which my speakers show in room. I use a modified listening window which consists of 2 15 degree curves and the 30 degree curve as it approximates my listening position better since I use no toe-in. These sound better to my ear than PEQ based on any other anechoic or in-room measurement I've done.

LS50_filters.JPG
 

Jon AA

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Thanks, should you ever stumple over whatever quality woofer that can cover 200Hz area and down situated right below LS50 then will imagine LS50 performance as satelite will really improve
Unfortunately they aren't very popular on the commercial market, but the LS50s seem to be a prime candidate for addition of a "Mid Bass Module" to turn them into excellent towers. It requires a few clamps and a bottle of glue, but these could turn the LS50 into an excellent tower for low cost: https://www.diysoundgroup.com/home-theater-speaker-kits/home-theater-extras/midbass-modules.html

Unlike subs (which often sound like garbage at higher frequencies) these are designed to work well in that frequency range--even the 15" is crossed at 350 Hz when used in a tower, providing high sensitivity, low distortion and great sound at those frequencies. With a single 2-channel amp and a miniDSP integration would be a breeze. No more need for speaker stands as a bonus. ;)
 

dc655321

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Unfortunately they aren't very popular on the commercial market, but the LS50s seem to be a prime candidate for addition of a "Mid Bass Module" to turn them into excellent towers. It requires a few clamps and a bottle of glue, but these could turn the LS50 into an excellent tower for low cost: https://www.diysoundgroup.com/home-theater-speaker-kits/home-theater-extras/midbass-modules.html

Unlike subs (which often sound like garbage at higher frequencies) these are designed to work well in that frequency range--even the 15" is crossed at 350 Hz when used in a tower, providing high sensitivity, low distortion and great sound at those frequencies. With a single 2-channel amp and a miniDSP integration would be a breeze. No more need for speaker stands as a bonus. ;)
Along similar lines, I've often thought a pair of LS50 (or similar) could be great, each perched atop a Rhythmik FM8, crossed at ~200Hz.
Even the height of the FM8 works out well for this scenario...
 

Ron Texas

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Along similar lines, I've often thought a pair of LS50 (or similar) could be great, each perched atop a Rhythmik FM8, crossed at ~200Hz.
Even the height of the FM8 works out well for this scenario...
There are a few members around here which have FM8's. One used them with Tad stand mounts, the other with M2's. My experience tells me a crossover a bit over 100 hz goes a long way toward eliminating bottoming of the mid/low driver in the LS50. Tracks which produced large excursions don't anymore. Rythmik says one can to up to 120 hz with their subs.
 

QMuse

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@QMuse I would be curious to see your 5 filter PEQ for the LS50, similar to what you did for the Sony. Starting the correction from high enough to get iut of the room impact.
Here is how corrected LW (blue) and corrected PIR (red) would look.

Capture.JPG


And here's the filter. This one requires 1dB of attenuation.

Capture1.JPG
 

stren

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Unfortunately they aren't very popular on the commercial market, but the LS50s seem to be a prime candidate for addition of a "Mid Bass Module" to turn them into excellent towers. It requires a few clamps and a bottle of glue, but these could turn the LS50 into an excellent tower for low cost: https://www.diysoundgroup.com/home-theater-speaker-kits/home-theater-extras/midbass-modules.html

Unlike subs (which often sound like garbage at higher frequencies) these are designed to work well in that frequency range--even the 15" is crossed at 350 Hz when used in a tower, providing high sensitivity, low distortion and great sound at those frequencies. With a single 2-channel amp and a miniDSP integration would be a breeze. No more need for speaker stands as a bonus. ;)
Yeah I hear you and as a fellow LS50 I've thought the same- but everytime I think along these lines, I think just trade it in and get the R3/R5/R7 etc instead. I seem to remember the R3 crossover is at 400Hz, so that also implies that any sub stretched up to 200Hz crossover may not be high enough. Once you're considering a MBM maybe at that point maybe it's better to consider a speaker designed with your goals in mind first before cobbling together multiple systems to solve something that's already solved by KEF on the R3. It would be different if the R3 didn't exist or if the measurements had shown it was a faulty design, but Amir's measured it as one of the best speakers so far (even if he wasn't a fan).
 

73hadd

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I have the same thought of trying the R3, but I don't read articles (in stereophile) whey they are (yet) using the R3 to evaluate amplifiers, like they are using the LS50 to do so. I wonder if the best properties of the LS50 were retained in the later models? I heard the R7 in a really big room, and expected to like them, but they sounded "boxy" to me.
 
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I have a pair of these in my study as a rotating pair in a lifestyle system. The room is absolutely terrible, being a near cube at 12' 3" x 12' 4" x 10' 6". I have completed round one of treating it with homemade broadband absorbers (varying between 2, 3, and 4" thick with open edges), which has eliminated the terrible flutter echo and brought the RT down from about 800ms to about 250ms across much of the spectrum. The bass modes are still "interesting" in that I can control perceived bass response by moving my head a few inches in any direction. Solving that will take more thought in treatment round 2. I obviously still have the classic room modes problem below 300Hz in the measurement shown below, even after treatment.

Anyway, these speakers actually work pretty well in my environment. I have them toed in only 1/4", sitting 10" from the back wall and 36" from the side walls, and the large doughnut port plug installed or not depending upon music selection. As my main source is FLAC files played from Foobar or Amazon Music HD, it is simple to run a PEQ like EQ APO, but these manual interventions sound better to me, and I leave it turned off.

In short, the 2K to 5K is mostly solved by pointing them almost straight ahead and the necessary sound absorbing panels installed in this room. The limited bass is solved by leveraging the rear wall boundary effect and room modes.








 
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Ron Texas

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What are the forum thoughts on a pair of new passive LS50’s for $799?

I have a pair of Q150’s I am very happy with in another room that I paid $350 for..
$799 is cheap. Is that new or refurbished. Bashing LS50's is a pastime around here and the preference score only made it worse. Remember these were the most talked about speakers when they came out and many paid reviewers still use them for comparison. With properly integrated subs and some EQ they are amazing. Remember, they have great dispersion which is something which can't be fixed and some frequency response misses which can be easily be fixed. You can always run with the herd and get whatever.
 

maty

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If you listen to very good recordings with high / very high dynamic range (DR):

KEF LS50: true sensitivity is only 83 dB. They love watts, much more than 100 watts at 4 Ohms. KEF LS50w has a class D amp to the woofer of 200 watts and a class AB to the tweeter of 30 watts.

KEF Q100, and probably Q150, only true 85 dB. Q100 loves amplifier with at least 100 watts at 4 Ohms.
 
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I have a pair of LS50s.

What are the forum thoughts on a pair of new passive LS50’s for $799?

I have a pair of Q150’s I am very happy with in another room that I paid $350 for..
If you look at the post above yours, I talk some about my experience with them.

I paid $800 shipped for mine a few years ago on sale. It is a great price; it is actually the typical refurbished price.

Mine are powered by a Cambridge CXA60, which is rated for 60W RMS at 8 Ohms and 90W RMS at 4 Ohms. (It once measured significantly stronger at ~75 / 105W, but I can't seem to find that article again.) I find it to be plenty for a room my size and at my listening distance. I rarely set the volume control higher than 9:00 and listen at an average of ~75dB, with peaks on dynamic music occasionally reaching the 85dB range.

I also have a Peachtree Nova 150 (150 / 250W) that I have used with them, but I do not hear any benefit to the extra power in that room. (I need to send that Nova 150 to Amir for measurements, since none of the new Peachtree stuff has been reviewed here.)

I do not have Q150s, but I do have Q100s in my living room. The LS50s are very different speakers in terms of frequency response and quality of construction.

LS50s are leaner in the bass octaves and have more of a BBC curve overall. You can easily see this in the measurements on page 1. This can actually work to your advantage in some rooms like mine. In other rooms, it is easily overcome by careful integration with 1 or more subs.

LS50s have much better built cabinets and do not exhibit much in the way of cabinet resonances, which has been a "problem" with Q Series speakers.

LS50s do not have any audible port noise, whereas Q100s (front ported) do: midrange leakage at all levels, chuffing at high levels.

Both speakers have excellent dispersion and are very forgiving with seating position relative to the tweeter.

In summary, the LS50 is a much better built speaker that is tuned differently. That tuning works well in some applications and less well in other applications. And, they do require a decent amount of power to sound their best.
 
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Karu

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Looking for an opinion on power here. I am running the LS50 in my second system and the sound is fine but I hate the number of boxes and associated wall warts, etc this involves.

Setup now: Allo Digione sig streamer -> Mytek 192 dac/preamp -> minidsp 2x4 balanced -> wyred4sound mAmps -> LS 50 + 2x rhythmic f12G subs.

I am thinking of Minidsp SHD Power -> LS50 & subs.

Is the ~120 watts in the SHD too little for the KEFs? About 2.5m listening distance mid size room.
 

Soundstage

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$799 is cheap. Is that new or refurbished. Bashing LS50's is a pastime around here and the preference score only made it worse. Remember these were the most talked about speakers when they came out and many paid reviewers still use them for comparison. With properly integrated subs and some EQ they are amazing. Remember, they have great dispersion which is something which can't be fixed and some frequency response misses which can be easily be fixed. You can always run with the herd and get whatever.
A comparison was made here with the Revel M106:
https://www.stereophile.com/content/tale-two-speakers
and the KEF did not disappoint
 

whazzup

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Noob 2-part question. Amir mentioned:
Lowest impedance above 20 Hz is at 216 Hz. Phase angle is high at the same time so that is a difficult load although music energy is also rather low there.

1. I understood the impedance part. But how does the phase angle of ~-6 degrees @216 Hz make the load more difficult (the way I understand this 2nd sentence)? I thought a phase angle close to 0 is better? Or does it mean a lower phase angle value is always better?

2. Frequently heard LS50 is 'difficult to drive'. I initially thought that could be seen from the measured 4 ohms lowest impedance. But if that's the case, shouldn't any amp that's rated for driving 4 ohm speakers be fine for driving LS50? Like some of the older Denon mini hifi amplifiers that comes with 4 ohm small speakers rated at 20-30W. I see people recommending way more expensive amps though (Hegel, Peachtree and others), is it because they anticipate people wanting to drive LS50 at much louder volumes and hence require higher wattage?
 
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^ I am really here to read the expert answers to your questions, but I'll throw in some anecdotes anyway.

1. I can't answer the phase angle questions, but the frequency of 216Hz is near 200Hz, which i think of as the "mud" frequency. Too much information here makes a mix sound muddy to me, so I don't mind if a speaker is light at ~200 Hz for whatever reason. In any case, this is not where anything punchy happens, so an amplifier does not need to be ready to supply high current.

2. "Difficult to drive" depends on your application: room size, desired SPL, desired level of punch, with our without a sub, etc. Mine are in a 12x12x10.5' room with an average listening level of 75dB. I drive them with a 60W RMS @ 8 Ohms / 90W RMS at 4 Ohms amp with no problem. I find the amp (CXA60) has plenty of reserve power to provide more than adequate dynamics. I think 20 to 30W RMS might be on the shy side, but I have not tried it. A little lifestyle amp like the Denon you describe is not designed for high current and would probably suffice only for background music.

IMHO, YMMV
 
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stren

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Noob 2-part question. Amir mentioned:
Lowest impedance above 20 Hz is at 216 Hz. Phase angle is high at the same time so that is a difficult load although music energy is also rather low there.

1. I understood the impedance part. But how does the phase angle of ~-6 degrees @216 Hz make the load more difficult (the way I understand this 2nd sentence)? I thought a phase angle close to 0 is better? Or does it mean a lower phase angle value is always better?

2. Frequently heard LS50 is 'difficult to drive'. I initially thought that could be seen from the measured 4 ohms lowest impedance. But if that's the case, shouldn't any amp that's rated for driving 4 ohm speakers be fine for driving LS50? Like some of the older Denon mini hifi amplifiers that comes with 4 ohm small speakers rated at 20-30W. I see people recommending way more expensive amps though (Hegel, Peachtree and others), is it because they anticipate people wanting to drive LS50 at much louder volumes and hence require higher wattage?
My understanding is that yes 0 phase like an ideal resistor is easier to drive. I think it's not that it's -6 at 216Hz but that a little lower frequency than that it's coming up from -50 degrees. 4 ohms minimum is fairly common for bookshelf speakers and that phase transfer around 200Hz is almost identical to the revel m106 that amir also said wasn't super easy to drive.

I think a lot of the reputation about the LS50's amplifier needs comes from a lot of the fluff in this industry. There have been a lot of recommendations of the LS50 as a great speaker that punches way above it's weight/price and therefore the idea is that it can make use of a better amplifier. There has been a typical idea that you must break your budget up equally between source, amp and speakers for example. If you were a typical audiophile that didn't know about the great value hypex amps then you might think you need to pay significantly more than $1500 to get a good amp. I think it also helps to deflect negative criticism from people who didn't like the ls50 - for example "you didn't feed it with a proper amp". Then couple those thoughts and ideas floating around with the ls50W version using 200W for the woofer. That then means Kef confirmed it - you *need* at least 200W to get the most out of them. However the LS50W is also using DSP to push the bass response of the driver out lower then the passive would.

So do you need a ton of power - like Steve said - well how big is your room? I drive mine with an amp rated for 80W into 4 ohm. They are obnoxiously loud in my apartment with the volume set at 1/3 (whatever that means). That equates to say 85-90dB at the listening point. However I do use a sub and room correction which could make things easier. Would the sound improve with a better amplifier? Who knows - maybe? I'm somewhat skeptical that I'd notice though. But do I still have an itch to try a hypex or purifi amp? Oh yes...
 

Kw6

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I use to own these speakers had an accurate midrange. Very present. But the speaker sounded small and treble wasn't airy.
 

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