True Anechoic Kef LS50 measurements..

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ra7

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2009-02-07 6:47 am
Davis, CA
Thanks for this!

This confirms my suspicions about Stereophile's measurements. Whenever Stereophile posts on-axis curves, they are usually averaged over a 30 degree window. This means that on-axis is going to be a rising response. This is clearly seen the pure on-axis measurements of Soundstage.

I cannot understand how a company as big as KEF can put out a product with such a glaring flaw in the response. Some say that these are to be listened off-axis. They will still sound bright. The power response is going to be much too flat with that on-axis response and the waveguide action. The correct way is to have a flat on-axis response or even slightly drooping on-axis response and let the off-axis fall off. That is the only way to get tonal balance right.

As for the LS50, not sure about the value. You can find much better value in Jeff Bagby's designs, or Joachim Gerrard's new design on this website. And if you can buy the raw drivers, then you can design a more linear speaker than KEF.
 

ra7

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2009-02-07 6:47 am
Davis, CA
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I believe the LS50 was "voiced" in the BBC LS3/5a tradition
KEF Reference 201/2 loudspeaker Measurements | Stereophile.com
(All the critics are going totally gaga over it's sound quality, regardless of overall accuracy), while the 201/2 was purely an exercise in creating a laboratory quality reference(And a beautiful one at that).

Sorry, wrong link. Here's the right one..
BBC LS3/5a loudspeaker Harbeth Measurements | Stereophile.com
You can see a definite similarity in the FR between the two speakers.
 
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ra7

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2009-02-07 6:47 am
Davis, CA
Don't let them fool you with their words. That speaker will sound bright. Besides, what is the intent behind making it sound like a 25-year old speaker? Do have any interest if it sounds that way? Or are you interested in fidelity?

Look at the measurements. That's what they are there for. I learned the hard way. I bought a pair of Q900 based on Stereophile's measurements and it's recommendation. When I measured them, I got a completely different picture, which agreed with my listening. They measured hot in the treble and sounded that way. That's when I realized that Stereophile was sneakily publishing averaged measurements for the on-axis response.

Just audition them before you buy'em.
 
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Don't let them fool you with their words. That speaker will sound bright. Besides, what is the intent behind making it sound like a 25-year old speaker? Do have any interest if it sounds that way? Or are you interested in fidelity?

Look at the measurements. That's what they are there for. I learned the hard way. I bought a pair of Q900 based on Stereophile's measurements and it's recommendation. When I measured them, I got a completely different picture, which agreed with my listening. They measured hot in the treble and sounded that way. That's when I realized that Stereophile was sneakily publishing averaged measurements for the on-axis response.

Just audition them before you buy'em.

Totally agree, but I have to ask, do you really think this is a flat measured response? Really?
http://www.stereophile.com/content/kef-q900-loudspeaker-measurements
 
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ra7

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2009-02-07 6:47 am
Davis, CA
Haha... you are right. It looks quite terrible now. I don't know how I was swayed then. The scale is quite small, about 50db, with 5 db/div, which makes it look bad overall. But there is no rise in the graph from 1 kHz to 20 kHz, which is present on axis. There is also the issue of a 2 kHz woofer peak, but they mentioned that in the review.

I swear it looked better on paper :)

The subtlety of what Stereophile is doing is clearly visible in the "on-axis" measurement that is presented as representative of the linearity of the speaker.
http://www.stereophile.com/content/kef-ls50-anniversary-model-loudspeaker-measurements
 
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mayhem13

Member
2008-09-22 4:37 am
I dunno, the measurements on paper don't look that bad to me. IMO, you have to consider the tradeoffs with any coax/coincident driver and what they bring to the table. But on the topic of the LS50, i didn't like it at all and IMO the enclosure size is part of the problem...it's too small.
 
Not surprising. Like most commercial products, accuracy is not the goal, the design is intended to jump out at you and impress for a demo session. Kef, like any big brand, could easily design a ruler flat speaker. They dont want to....

I've been going to audio shows for almost two decades now, and one thing that I notice is that a lot of commercial products are half baked. Basically the loudspeaker designer is in a rush to get the design finished, and the product has some glaring flaws.

And these same designers seem to come back to the audio shows, year after year, with another new design.

I don't fault the designers for this; my own projects exhibit the same issues. Basically I jump into a project with great enthusiasm, but I lose patience quickly and I don't want to work on the details that make a good product great.

Out of hundreds of audio brands, there are only a handful that don't fall victim to this. Brands that take a good solid design, and just refine it year after year, decade after decade. These are the Porsches of the audio world, the brands that take a good car, like the 911, and polish it like a diamond until it's world class.

Kef is one of those companies, and the LS50 is one of the best loudspeakers I have ever had the pleasure to listen to. I think that it's a higher achievment than the Blade, because the LS50s sonics far outweigh it's price.

I've heard speakers that cost ten times more and don't sound half as good. It's incredible.


If anyone's curious why there's a rise in the treble, it's not an attempt to 'fleece' people or 'wow' them in a showroom. It's because the cone of the LS50 acts like a waveguide for the tweeter. Due to this, the power response will make the speaker sound 'dull' to some people. It's something I've noticed with my own reference speakers (Gedlee Summas) and I've messed around with EQ to 'tip up' the top end as well. Whether you prefer it that way is a matter of taste (I don't) but I can see the reason why they would do it. I have a set of Kef coaxes and I tip up the treble on those too; it sounds better that way. If anyone's curious I can post the technical details on why the LS50 may be more receptive to a boost in the treble than most conventional waveguides are.
 
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ra7

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2009-02-07 6:47 am
Davis, CA
I'm sorry to be a party pooper, but surely, we, as a group here on diyaudio, cannot be applauding this speaker. There are some glaring frequency response errors that just should not be there from a company of KEF's capabilities. Look at their Reference 201/2 model's response. They know what makes a good speaker and yet choose to introduce non-linearities in their lessor models. Why should we accept such disingenuity and call it incredible?

The audiophile press might go gaga over them because they may be better than other crap that's offered for $1500, but why should we judge them by the same scale?

Have you guys seen the Kairos or the Satori monitor designs?
 
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I'm sorry to be a party pooper, but surely, we, as a group here on diyaudio, cannot be applauding this speaker. There are some glaring frequency response errors that just should not be there from a company of KEF's capabilities. Look at their Reference 201/2 model's response. They know what makes a good speaker and yet choose to introduce non-linearities in their lessor models. Why should we accept such disingenuity and call it incredible?

The audiophile press might go gaga over them because they may be better than other crap that's offered for $1500, but why should we judge them by the same scale?

Have you guys seen the Kairos or the Satori monitor designs?

fr_456075.gif

fr_456075.gif


I've heard them, and I believe that I understand why the on-axis treble is 'tipped up.'
As noted in my last post, Kef is tipping up the treble to improve the in-room power response.

Above are a couple measurements done by the same lab. The first is of the Kef LS50. The second is of a Chorus 836W.

See how the second graph has a dip at 3750hz, a peak at 7500hz, and another dip at 15khz? Whereas the Kef has a slowly decaying response, but lacks the peaks and dips of the Focal?

I believe these graphs explain why the on-axis response is tipped up, and why the reviews are so good. If they didn't 'tip up' the on-axis response, the power response would make them sound 'dull'. And the review are spectacular because reviewers are nothing the fact that Kef has hit a home run here, plus the power response is very very good. These are as good as anything out there in their price range, and better than a lot that's more expensive.
 
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