Can the KEF LS50 rock?


Hi,

Right now my setup includes a Rel T5 sub and a pair of Wharfedale 10.1s. I just got a peachtree nova 125se which should be coming soon. For the longest time I have been looking at buying a pair of KEF LS50s. My room size is medium and I rarely get to play my music loud. All that being said if I bought the Kefs and paired it with my sub how would they do when I occasionally feel the desire to rock out? Any other monitor suggestions would be helpful. I live in a small town so there isn't much chance to test drive speakers but maybe I can take a roadtrip to Denver in the future.

Thanks!
Convert?fit=crop&h=128&rotate=exif&w=128brimel1974
I heard them with rock at a dealer. Acoustic rock sounded pretty good. Electric rock not so much. Heavy Metal sounded jangly and thin. Every Dynaudio monitor I have heard has done well with rock. IMO Merlin TSMs do very well for any kind of music if your room is not too big. They are fast and tight and don't emphasize anything. Had them in a 16x22 room 8ft ceilings and loved them! Moved them to larger room with 12ft ceilings and they didn't do so well but I guess may be too big for most monitors.
It's not obvious to me what OP means by rock out, but I have been amazed by the ability of the LS50s to play loud.  Two distinct cases in point:  The Blu-rays of Legends of Jazz and the large orchestration of the Decca recording of Aida.  I'm using a Sony XA5400ES through a Cary Cinema 12 to a Parasound A 23 amp, and a pair of Velodyne HGS-10s with SMS-1 bass manager to supplement the LS50s below 80 Hz.  The LS50s are impressive.  Will they crash and bang like an Altec A7 VOT? Probably not, but they'll sound a lot better with everything else.
imo speakers are genre biased to some extent. Imo if the op was not thinking of classical or jazz by the term rocking out but with rock music I would say they are not too impressive with this style of music.
Since your sub is a REL and I assume you are running the speakers full range, the sub will have no impact on how the LS50 handles high volumes in the bass region. I've posted this many times before, the LS50 is a serious distortion generator.
http://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=941:nrc-measurements-kef-ls50-loudspeakers&catid=77:loudspeaker-measurements&Itemid=153

The LS50 begs to be high passed.

Sorry bob but these measurements mean nothing to me. I am already running a 2.1 system and the sub definitely makes a difference so you are going to have to explain further. 

I would like to know how they perform with rock music and if any deficiencies would be cured by pairing a sub. I think you are trying to answer that question but I would like it put into layman's terms.

Also, if you could suggest an alternative that would be cool. I prefer a more treble forward sound if that helps. 
Bob, your contention that LS50s are serious distortion generators doesn't comport well with the many rave reviews and observations of those who have listened to the speakers.  I don't understand why the OP's use of a REL sub would dictate running the LS50s full range and obviate an 80 Hz crossover to the subs.

Brimel1974,

The relevant chart is the total harmonic distortion. The graph at the top is the frequency response. The graph at the bottom is the response of the THD. As the bottom graph approaches the top graph, it indicates the THD is increasing. If the bottom graph reaches the top graph, you have 100% THD. You see that the bottom graph begins to rise rather steeply just below 500 Hz. This isn't bad until 100 Hz as the frequency response (the top graph) is beginning to fall off. At 50 Hz, the THD is approx. 31% (-10 dB down from FR). For comparison, look at the NHT Classic Three.

I'm a big fan of subs, but IMO to take full advantage of them you should high pass the main speakers. This takes the bass load off of the main speakers and amps (since you are truly biamping with the amp in the sub). Doing this reduces THD of the entire speaker system, as well as, IMD. This also increases the chances of improving bass response.

REL subs are designed as "sub-bass" systems. They are intended to be used with full range speakers; to augment the bass of the main speakers.

I don't doubt that adding the REL sub to your current speakers yields an improvement in bass and, thus, your perception of the entire system. My contention is that as you increase SPL, which was mentioned in your original post, the distortion produced by the main speakers will increase greatly since the bass load is not being completely handled by the sub. Again, I am assuming that you are using the REL in its typical configuration using speaker connections and running the main speakers full range.

I think, as the FR charts clearly show, the LS50 is a great speaker and paired with a sub, when high passed, will yield a great speaker system.

Regardless of the particular sub, the critical issue is removing the bass load from the LS50. You do that by using a high pass filter in front of the LS50. You can buy external bass management controllers (HSU Research has such a device); mini DSP has a digital device; some subs contain high pass filters (like SVS); using an AV pre/pro and doing everything in the digital domain (also gives you room mode correction).

I hope this helps some.

-- Bob 

Dbphd, it's not surprising that objective and subjective opinions don't agree. A lot of music doesn't contain a lot of low bass and depending on SPL, the THD measurements look much worse than they are in practice (though they do measure at 2 m). But this being a perfectionist hobby I think it makes sense to avoid obvious limitations. Thus, my suggestion to high pass the LS50. One shouldn't expect clean bass at relatively high SPL from a tiny speaker.

Re the REL. I was commenting based on the assumption that it was being used as REL suggests. There's no reason it can't be used in bass replacement mode.


I totally agree with Bob's excellent response.

"I would like to know how they perform with rock music and if any deficiencies would be cured by pairing a sub."

Yes, the deficiencies would be cured by pairing a sub, but only with a high pass crossover as Bob described. Your Rel T5 has a low pass crossover for its input signal, but this has no effect on the main speakers. They would still be playing full range. Also, with the Peachtree Nova 125se, there is no way to use a line level (RCA connection) high pass crossover, separate box or built into a different sub. With the current equipment, your only option would be a speaker level high pass crossover.

Keep in mind that this is not just an issue with the LS50, but any small speaker.

Hi,

I am using a speaker level connection as per Rel's recommendation. 

From the manual:

  The HIGH LEVEL, unbalanced, dual-channel (stereo) input is via a Neutrik Speakon connector which is connected to the power amplifier’s left and right channel speaker terminals. This has the advantage of ensuring that the REL receives exactly the same signal as the main speakers. This means that the character of the bass from the main system is carried forward into the sub-bass. This is a very important point and together with the REL’s Active Bass Controller (ABC) ensures far superior system integration of the sub-bass with the main system.

This is how I have connected the sub.

brimel1974,

I'm sure the recommended connection from Rel is the best for the T5, however this has no effect on the main speakers. They are still playing full range and the issue remains. As I previously stated, with the current equipment, your only option would be a speaker level high pass crossover inline between amp and main speaker to solve the issue.

brimel1974.

This has the advantage of ensuring that the REL receives exactly the same signal as the main speakers. This means that the character of the bass from the main system is carried forward into the sub-bass. 

As your quote states, REL subs are designed as "sub bass" speakers. They are intended to be used with full range speakers.

Now, the quote above that I copied from yours, is simply marketing hype. If the REL sub was a passive speaker, then I'd agree with their comment. However, there is an amp inside the REL sub that receives the signal from the main amps. The driver in the sub does NOT receive the same signal as the main speakers and it does NOT have the character of the main system.

Are we really to believe that the inexpensive amp in the sub does not impart its own sonics on the sub bass?

Also, logically if speaker level connections were all that REL's marketing department would like us to believe, every sub manufacturer would be suggesting it. I think it's more likely that Richard Lord designed a sub for use with integrated amps that were/are so common in the UK. The vast majority of integrated amps do not have preamp outputs, much less, main amp inputs (that are necessary for inserting a bass management controller). 

I believe that if you review the serious sub products on the market you won't find many that provide speaker level connections. 

On the positive side, REL makes a fine product (though over priced for its performance) and can be a nice addition to a music system. 
The signal from the speaker terminals to a REL is replete with whatever crap is on that line, primarily back-EMF. Thus the sub is seeing the same signal as the speakers especially given the 100k+ input impedance of the REL's high level inputs. I have owned five RELs over the years. They work as advertised. I have no connection whatsoever to the company (or any AV company for that matter). They simply work, and in ways you wouldn't think a sub would work. They RAWK!
I'll try one more time...

Yes, it's true the REL speaker level connections see the same signal as the main speakers (though I don't understand how their impedance would impact this mystery "character"). But, the DRIVER in the REL sub is being driven by a relatively inexpensive amp. Whatever "character" is emitted into your room will NOT be the character of the main amp, but some mix of the main amp and the amp in the sub.

As I said earlier, if the sub was passive, then REL's argument would be rational. The sub is active, so their argument is simply marketing hype. Amazingly, it appears to be working -- kudos to the marketing department.

REL subs are distinguished by having a low group delay, but it's unclear whether it being much lower than one cycle offers any audible advantage.

REL makes a fine product. There are many fine subs on the market that are much better values.

brimel1974, if you enjoy the sound of Wharfedale speakers, you might consider their Jade series, specifically the Jade 3.

http://www.stereophile.com/content/wharfedale-jade-3-loudspeaker#wPAi8d1hzpgls7h7.97

They would be my pick over the LS50. You don't see many 3-way stand mount speakers on the market.
KEF LS50 is overrated and overpriced. The implementation distorts the sound quite a bit when compared to accurate speakers. Go with the ELAC floorstanders instead. (Another option is the JBL LSR305/8 + 310s sub in a 2.1 setup, that's what I have now, super accurate, super awesome, super value)

The LS50 got great resale value though, I sold it in one day for about the same price I bought it at.
Hi there Brimel
My son has the LS 50s with a nova 65 SE. In a medium size basement room - it plays plenty loud. Adding an REL T9 added some serious bass which can definitely be overdone. But yes they can rock, just not at deafening leveIs. I set up a system for friends consisting of Peachtree 200 separates and a pair of LS 50s with a T7 sub and they Absolutely love the system in a big living room with 8-9 foot ceilings and have no interest in upgrading anything. I set up another friend with the same Peachtree separates in a huge room with cathedral ceilings and selected Vandersteens 3s because the room was simply too big for LS 50s. He absolutely loves the set up. No interest in upgrading. I also have LS 50s paired with a Sprout that sound fantastic in a 14 x 12 bedroom. Sooo. In a medium sized room where you don't often play music very loud a 125 SE
paired with LS 50s should work really really well for you. Add the T5 you already have and you will get more bass that will be a welcome addition if you don't ask it to play at rock concert levels. REL subs don't relieve the load on either the Peachtree amp or the LS50s as the others have pointed out. But they will simply add more bass - which is a very satisfying addition to an already fantastically well reviewed and in my opinion wonderful speaker. 
The UltraFidelis website has a great explanation under the heading why everyone needs a good sub. But what they are talking about and the other gentleman here is talking about is adding filters between the pre and power amps which you cannot do with the 125 and is what Vandersteens subs and their higher dollar speakers do. Better?absolutely, but way more money. I'm guessing you will absolutely love the 125 with the LS 50 T5 combo for 95% of your listening. We have used anticables with bananas on each end with great success. Don't overthink it and enjoy the music!
FYI Main system is CJ PR12s PR16LS 2 Ayre QB9 DSD GYRO SE SME V Benz Ebony PR15
and B&W Signature 30s. 


I have had a ton of monitors through my system in the past 10 years and the LS50's were my least favorite, notwithstanding their fine reviews.  I found them to be harsh and very hard to drive.  I have fallen in love with Dali monitors, very neutral in their sound.  I have a REL T7 sub that fills out the LF very well with my current OB speakers.  I think some of the best monitors around are offered by Fritz Audio and would suggest you consider a demo of them.  No question that ELAC floor standers ought to be on your radar, particularly at their price point. 
Good luck, Whitestix
Go with the ELAC floorstanders instead. (Another option is the JBL LSR305/8 + 310s sub in a 2.1 setup, that’s what I have now, super accurate, super awesome, super value)

The LS50 got great resale value though, I sold it in one day for about the same price I bought it at.

I was thinking in the same direction. The Elac Uni-Fi UF5 Tower has a concentric midrange/tweeter (similar to the LS50) but augmented by three small, fast (5-1/2") woofers in a larger enclosure. Their dimensions are very compact, however at 7.87"w x 38"h x 10.75"d. They should match well with your REL even if you don’t high-pass to the Elac towers. They were designed by Andrew Jones and are only $999/pair, meaning you could sell your KEFs and have money left over. They have far more radiating surface than the LS50s, meaning they should be able to "rock out".

http://www.musicdirect.com/p-438083-elac-uni-fi-uf5-tower-speakers-pr.aspx
Hey johnnyb53. I know the Elacs are getting great reviews but I don't know if I want to invest in a pair of speakers featuring "luxurious textured vinyl finish."

Music Direct is also selling the Wharfedale Jade 5s for about 600 more. I do like wharfedales.
To me, Bob made the really relevant comment early on:

"The LS50 begs to be high passed" (maybe low-cut would be clearer).

The speaker looks great with smooth (and very gently falling off-axis) frequency response.  However, it can't produce really clean output below 200hz and is a mess at 100hz - provided that the power in/SPL in the test is reflective of that in actual use - which is, in turn, dependent on any individual listener's preference in a given installation.

IMO, if you're using this speaker for listening to wide-bandwidth program material at real world SPL, a high quality, actively crossed sub-woofer will almost certainly produce a tremendous improvement in bass response.  I'm not sure whether I'd cross at 100hz, 200hz, or somewhere in-between, but I'd definitely add a subwoofer (or two in stereo) for this type of listening with the LS50.


In a brief in house audition I did with ls50s a while back,   I found bass performance was very amp and room dependent.


Sounded great in smaller room with high current high power (500w/ch 8 ohm) low output impedance Class D amp (Bel Canto ref1000m),  was very underwhelming in a larger room with lower current, higher output impendence, 180 w/ch 8 OHM SS amp (TAD Hibachi), much more so than other similar size smaller monitors I have tried.

The Pioneer FS52 floorstanders, also designed by Andrew Jones and was on sale for like $75 each. They sound so damn good, definitely more enjoyable for music than the LS50. The ELAC is Andrew Jones’s latest creation at twice the price point using 2015/6 technology, it’s a no brainer really unless you want to learn things the hard way via your wallet. Been there done that.

If you search around, you’ll find Andrew Jones on diy forum personally explaining distortions from concentric designs and how he overcomes it with 3 way by minimizing the movement of the mid cone/guide to the woofer. This is something the LS50 lacks and is very noticeable if you A/B it.
Interesting. So far in this forum I am hearing a lot of negative feedback. Only one person has actually tried the Rel sub and Kef combo and was very positive about it. Kudos to you man. 

Problem for me is I live in a small town so I don't have the opportunity to listen before I buy. I'm going off of reviews mostly. The LS50's have received tons of superlatives.

I have also thought about going the sub monitor combo with the Dynaudio Excite X14's or Wharfedale Jade 3's or ditching the monitors altogether and getting a pair of the Zu Soul's or Zu Omens. Maybe even the Monitor Audio Silver 6? 

Again I am just going by reviews that seem to feature the sound I like and looks. I want whatever I buy to look good because it is going to be in my living room and I look at them as long term investments.

Thoughts?
When earthquake hits, everything and everybody ROCKs!
You might want to read this article.. You can save a lot of money by purchasing the Elac's and maybe even come out with better sound.. I heard them and they can play loud but at a reasonable level.. Meaning if you're sitting in front of the speakers and turn up the volume you'll rock!.. If you mean turn up the volume while you're at the other end of the house then who knows or cares.. You can purchase these on line and send them back if you're disappointed.. I hear Elac has great customer service as well..

http://www.stereophile.com/content/elac-debut-b6-loudspeaker#LsRJvJZjy67IiHi6.97
Regardless of Andrew Jones' rep and the ELAC reviews (I'm sure they offer a great value), the reality is that the cabinet of a floor standing speaker has a greater potential to sing on its own than a stand mount speaker; it's simply a matter of surface area.

You probably need to spend upwards of $3K on floor standing speakers for the cabinet to not be a liability and then there's no guarantee. Plus, since many floor standing speakers aren't really full range, a sub will almost always be a benefit. For a given price point stand mount speakers will likely have better drivers and crossover components than floor standing speakers, since less of the budget is going into the cabinet.

So, IMO stand mount speakers offer the best value. A 3-way will almost always play louder and cleaner than a comparably sized 2-way. 

Again, I think the Wharfedale Jade 3 is a gem in the market today. If you had to avoid a sub, then the Jade 7 would be my pick. I could argue for Revel speakers as well.

Whatever little speaker you decide on, it will sound much better by, as others have already said, putting a high-pass filter on the amp powering them. That will remove the bass frequencies (depending on the corner frequency of the filter) from that amp and the monitor, greatly reducing the distortion the speaker produces. All the filter needs to be is (usually) a capacitor soldered onto the power amp's input jacks (on the inside of the amp). The formula for determining the value of the capacitor needed is:

C = 1 / 6.3 x f x z, where C = capacitance in uF, f = the corner frequency of the filter desired, and z = your power amp's input resistance figure.

This will NOT be possible if you hook up your sub to the same power amp as the speakers, obviously.

You probably need to spend upwards of $3K on floor standing speakers for the cabinet to not be a liability and then there's no guarantee.
Generally true, except for Magnepan. I've had some 1.7s for 2-1/2 years and love them. They combine the vibration-free delivery of a mini-monitor with the natural ease and room-filling advantage of large dipole radiating surfaces. 

The .7s are only $1400/pair.

Thanks bob_reynolds. I am definitely leaning towards the Jade 3s and trying to blend in my sub. They are a bit cheaper to. Do you think they will have a forward treble on them? I usually turn up the treble on my av receiver because I like that extra sparkle. Or maybe I am just hard of hearing and have trouble picking up vocals. The new peachtree does not have tone controls.
A note on REL subs...I have 2 of an older generation of these, a Q150e and a Q108 II, and upon taking them apart to tighten stuff and look around, I've noticed they are very well built torroidal transformer based amps assembled to a very high standard, and they sound great…exactly as designed. Nothing "cheap" about them. The REL's high level input of course does take the speaker signal and reproduce at least the lower range that the power amp is sending out (tube in my case) regardless of what the mains are doing, and small driver mains like the LS50 aren't expected to create earth shattering bass anyway…I use mains with 2 powerful small drivers (plus single tweeters) in each that naturally roll off below a certain point (you have to drive the crap out of them to get them to give up, so they don't get over driven unless subjected to accidental drunken "knob turner" abuse) and that's how it should work. Leaving the mains full range utilizes the speaker designer's mojo, and the RELs job is simply to energize the room and provide the lower octaves if you want 'em. I defy anyone to detect tonal aspects in RELs that aren't from the amp, as hey…it's all low range of course and to my (working professional sound tech, pro guitar and bass player) ears seemingly neutral…they might have a tone of their own but my 2 RELs, albeit with a different output and driver size, are absolutely identical tonally, and they don't seem to noticeably add anything to whatever tone character the amp sends to them.
brimel1974,

Looking at the frequency response in JA's measurements from the Stereophile review, the treble is peaked up several dB. So, yes, the Jade 3 should sound brighter than the 10.1 which has a flatter response through the treble.

Though I wouldn't expect that to impact vocals, per se, since human voice is lower in frequency. The Jade 3 having a dedicated midrange driver should be an advantage for vocals.

You might experiment with toe-in and especially vertical height to see what impact that has on vocals in your system & room.
Thanks bob!