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High-level. Even crossovered at 160 Hz to a subwoofer, the sound of the Kef is degraded at high level: it becomes aggressive, and the frequency response is not linear anymore.
But they are incredibly good at low, normal and normal-to-high level, they collapse only at very high level in a large room.
Not only the image is rock solid, like for all coincident speakers I listened to (Tannoy, Seas, Kef), but the clarity and detail are outstanding. I finally understand the words of songs on CDs I own for 20+ years!!!
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to expect anything else is absurd.
I doubt that speaker was designed to play at "very high level in a large room."
Bet KEF makes speakers that do that quite well.
Get back to us on that.
"Once this was all Black Plasma and Imagination" - Michael McClure
You can't fool mother nature. The LS50 is essentially a small cube. It will have rather obvious SPL limitations.
I mean if we just look at the construction of the coaxial .. it is really something
They could stick with the design and give bigger size coaxials (like 8" and even a 10" )
They could be a serious threat for the Tannoy brand.
Regards,
beppe
That's a non-starter for me.
Hello !
are you referring to the lower efficiency of the Kef ?
You are right.
Still the design of the kef driver is very nice and worthy further developments i think.
I like it.
Kind regards,
beppe
'efficiency'....you means sensitivity, right? has little to do with it.....though combinations of low power, large rooms and low sensitivity speakers don't necessarily work well together especially if higher levels are expected....but IMO, the REAL problem may be phase angle.
For example, the LS3/5 series .... especially the original which was what? 16 ohm? 11 ohm? was indeed low sensitivity but fine with tubes because of mild phase properties.
IF the LS50....which the demo guy said were 'spiritual descendents of the LS design'....(parapharase) I'd expect them to behave with tubes.....even if Not Necessarily with the lowest powered among them or in larger rooms.
I think some testing is in order.....under reasonable conditions where it can be seen just how much power of quality you need for the LS speakers.
At THE Newport, they were very nice, indeed....but I don't know how much power was behind them.
Too much is never enough
You're gonna need a bigger SET.
:)
Hello,
in the picture you can see the max output level obtainable from the speaker at 1 meter with less than 5% distortion
It seems quite clear to me
It is taken from an Italian magazine, Audioreview
A very telling test
Less subjective i mean
Kind regards,
beppe
Thanks!
You are welcome ! stolen from internet
But in general it would be nice to see more tests on distortion
I am still so naive to think that distortion is a bad thing
Not only. If i am not wrong is a sign of stress from the drivers that can be even damaged in the long term i think.
I am pretty sure that small speakers would sound better with a high pass filter set at 60-80 Hz
Regards,
beppe
Edits: 10/28/13
Check out Sterophile's Impulse test measurements. The vast majority of speaker designs incorporate drivers with inverted polarities, many of which are frightfully expensive (Wilson's for example).
In real life, sound comes at you in one polarity. I can NOT see why designers design speakers where one driver is moving in one direction and an adjacent one is moving in the opposite direction. That simply is NOT accuracy, nor is it sonic truth.
Truth be told, after being in the business for 3+ decades, this kind of inaccuracy is very good for business, though. No matter how much you spend or what you buy, nothing is quite accurate and, sooner or later, you will uncover an issue created by the drivers being out of polarity.
Of course YMMV
Hello !
i find all the issue very interesting but i would like to ask you some questions.
In Stereophile they state " Turning to the time domain, the LS50's step response on its tweeter axis (fig.8) indicates that the tweeter is connected in positive acoustic polarity, the woofer in negative polarity "
I have not understood why they do this.
What is the advantage ?
Connecting the woofer with the same polarity of the tweeter could give a perfect step response ?
I mean just reversing the cables at the woofer would make the trick ?
By the way your explanation makes perfect sense to me
Maybe it is one of the very advantage of single membrane drivers
I would like, on principle, to have a speaker with a good time alignment and same polarity between the drivers
Thanks a lot and kind regards,
beppe
Any second order (12 db/octave) filter, Butterworth, Linkwitz-Riley, Bessel will create an 'infinite' hole at the crossover frequency if the two drivers are hooked up with the same polarity.
If you reverse the polarity of one of the drivers, you get a 'bump' of 3 db with a Butterworth filter, a flat response with a Linkwitz-Riley. When your ears are at the same distance from each driver.
I really like the results with a second-order L-R, when the woofer and the tweeter, as well as the choice of the crossover frequency, are adequate.
Thank you very much indeed.
I think i have understood.
By the way if there is a type of x-over that can give a flat response and a good step response for me it looks like the right one.
To keep same polarity for tweeter and woofer it seems to me a valid objective.
Kind regards,
beppe
Only a 6 db/octave crossover can reproduce well a step response.
And I mean an ACOUSTIC (drivers + crossover response)6 db/octave filter.
Very difficult to achieve: you need drivers with a very flat response on 2-3 octave on each side of the Fx frequency, the frequency response of the loudspeakers changes a lot in the vertical plane, the tweeter is more likely to distord or even fail at high level.
I do know a few good examples, though: B&W DM6 (30 years ago!), Dynaudio Focus 140, Vandersteen 2CE. Thiel, B&W Diamonds should be good too, but I didn't listen to them.
Thank you very much again for the very interesting explanation.
Personally i do not understand why the use the step response
I prefer the impulse response test because it is easier to see any unwanted tail in the driver response
I strongly believe in fast drivers, with high rise time e high damping after the impulse.
I understand that the x-over issue is a very tricky one ... not easy to achieve very good results. But also fascinating.
I would give active crossing a try anyway.
It is so easy to set cut freqs and even slopes in the digital ones.
The idea of using a driver only in the range where it can give its best
it sounds very good to me.
But it is not very popular i am afraid at least in home listening system.
Almost no one is using electronic x-overs.
There must be reasons.
Thanks again,
Kind regards,
beppe
Edits: 11/01/13 11/01/13
With a fourth order acoustical Linkwitz XO, the drivers sum flat AND are in the same polarity at crossover frequency. Reversing the polarity of one driver will then produce a deep null, which is a pretty good test as it indicates excellent phase tracking in the correct polarity.
There will inevitably be a dip at crossover frequency in the horizontal off-axis response, and various dips and peaks as you go off-axis vertically, but this is the case with most crossover topographies. LR4 is somewhat more forgiving than most on the vertical off-axis. If you listen on the correct axis, in a reasonably damped room, there should be no problem.
Did you just use "fourth order crossover" and "excellent phase" in the same sentence?
The 'vast majority' of speakers having one driver in reversed polarity seems to be around 40%.
Anyway, an inverse polarity is required for speakers using second-order filters, and the Linkwitz-Riley second order is my favorite filter when properly implemented.
You could imagine a large distance (in depth) between drivers to preclude the necessity to reverse the polarity of one of the drivers, but it would also be a 'reversed polarity', geometric instead of electric.
Siegfried Linkwitz himself considers that the absolute phase is audible in the low frequencies, a lot less or not at all in the highs (which makes the polarity of the tweeter irrelevant, except for the response in the crossover region). The problem there is that there are large delays (phase changes) created by inertia, friction, 360° 'out-of-phase' vents in bass-reflex enclosures, etc.
The only valid reasons for one driver being inverted polarity is to avoid the 'infinite' gap created by a second-order filter, or to correct for a different distance between the listener's hears and different drivers.
I don't believe that absolute polarity do matter; not only the Kef LS50, but also for example the Focal 1007Be, the Harbeth P3ESR, The Sonus Faber Cremona have one driver working in reversed polarity, and these are among the best-sounding loudspeakers in their category.....
Do you really understand what I am stating? The issue with the KEF , like many others including Wilson's as I mentioned , is that the drivers on each cabinet are not in correct polarity relative with each other: So one driver is moving in one direction while the other is moving in the opposite direction.
Reversing absolute polarity will yield better highs in one orientation and better lows in another, not a universal improvement in any case.
This does NOT happen in nature with any acoustical instrument ( it can happen with amplified music and sound, however). For me, it is simply unnatural and wrong.
YOU may not hear it but I do. It is very easy to hear with a full range recordings, almost any one. It seems to me that if sonic neutrality and accuracy is your goal, such mixed polarity systems would not fit the bill.
That being said, you know your taste better than any one else can. If you're happy, then so be it: case closed. But do not tell me that the speaker is in any way accurate, though, because it simply is not. And do not tell me I can not hear polarity issues when I can and do. Just because you obviously can not hear it, doesn't mean that no one else can
The designers did make some remarkable compromises, though. Knowing that the typical male audiophile enjoys female vocals, they made the upper frequencies very seductive and appealing. It probably makes most males swoon over the sound and to the neglect of the lower frequencies.
But then listening to a piano with sweeping glissandos, from lows to highs, will reveal that the speaker will present the piano like it was two different instrument.
But then again if you don't listen to piano music, that is not an issue, is it?
Of course YMMV.
I also found that, unlike the LS3/5A, this speaker is not very tube friendly due to low impedance in the low mid-range. Whereas the original LS3/5A and some others (Stirling, for example) work wonderfully well with 300B amps, this one didn't...even on the 4 Ohm taps.
Silly me, i should have read the measurements section in the Stereophile review. With a 70W SS integrated, it sounded very nice, but that is more power than I care to have lying around the house.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
Yeah -- IDK about 300Bs but I've been demoing these again with a UR Simply Italy (15 or so) and a Rogue Cronus Magnum KT120 and both work beautifully with the '50s. I prefer the Rogue -- more grunt, of course, but also remarkable presence and tone -- but don't feel I'm missing much with either, except for that last bit of bass/occasional bass bloom on some recordings.
I've been much more impressed with these the 2nd time round. Not my first choice for a large room but in a small (10 x 12) room with weird windows and other placement issues, they can generate some genuinely sublime musical encounters.
Hardening up at high vols -- absolutely. But I'd say their threshold is at least as high if not higher than some other well-regarded competitors from ProAc, Harbeth, Dynaudio, Totem, etc. No biggie, given their design brief and intended uses IMO.
n
"Not tube friendly" is a rather silly and general statement. I have heard them driven with absolutely no issues with 50, 75, and 100 watt tube amps.
Flea watt and most 300B amps will not be a good match, I agree...
But that does not cover the entire category.
My Cayin A-50T sounds incredible on them.
"Lock up when you're done and don't touch the piano."
-Dr. Greg House
I don't find that surprising at all. I wonder why some would make guesses as to how the speaker works with tubes without even hearing the combo.
that "real" LS3/5A's sound very good, driven by 300B amps. 8-9W isn't exactly flea power. I'd reserve that for anything below 4-5W.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
That may have been in the past. I owned LS3/5As and I drove them with 50 watts or so, but I never tried them with tubes.The LS50 almost has nothing in common with older designs. Composite enclosure, coaxial driver, port...etc...
8-9 watts IS flea power IMO.
Edits: 10/27/13 10/27/13 10/27/13
played the LS-50 with a 300B Cary. Didn't play it really loud but on the 80 to 90 dB range with absolutely NO issues. Sounded better than a ss 100 watter.
Interesting. Since the majority of musical information is in the midrange/lower midrange, at modest volumes, at 300B should do fine. One just
has to be reasonble.
I think that it depends mostly on the woofer size because i saw a quite similar behavior for woofers of the same size.
For instance to get 125 Hz/1m/110 dB usually a 8" woofer is needed, or one high quality 7"
Then i looked at the 3 ways speakers by Wilson Audio, a reference for me
They cross at about 150Hz and used 7" mid of high quality to get high undistorted level across the band
Regards,
beppeP.S. it is all in the graph. Problem is to get the graph maybe and not only listening testing impressions
Edits: 10/27/13
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