KEF LS50 disappointment :(

[shkumar4963]

...

 

[jackocleebrown]

The majority of coaxial speakers that I've heard have seemed good in some areas but tend to be quite compromised in other areas. My experience of KEF speakers is quite limited but what I've heard has been very good. You certainly seem to be leading the field where coaxial speakers are concerned as the compromises that I've noticed in most them seem to be much less present in the KEF's.

You mentioned the region around the tweeter that doesn't move and the smooth trim ring that covers the basket area around the edge of the mid/woofer where it meets the enclosure. Was this easy to develop as it looks like a relatively simple idea in concept? I know how these sort of things often tend to get very complicated once you start looking at the details required to put it into practice.

Also what are your thoughts on the Genelec 8260A speakers? They seem to be the only other company that are pushing forward with development in these areas. They seem to have similar ideas to yours but have taken it a step further by effectively having an almost perfectly smooth acoustic wave guide that goes all the way from the edge of the tweeter, across the mid-range cone (which barely has any movement on the 8260A) and right to the edge of the enclosure. The results are the best that I've ever heard from a coaxial driver.

You're right, those two features are more or less obvious . I mentioned them in particular because they are key in reducing modulation of the HF by movement of the MF cone. (Incidentally, I was talking about the MF surround itself rather than the smooth trim ring, like the surround on the LS50 for example. This is quite a complex thing and took a long time to develop).

Less specifically to the modulation issue, the real key development for the Uni-Q was finding the right geometry for the tweeter dome and surrounding waveguide to get a good wide bandwidth response. Most of the work for this was done my my colleague Mark Dodd. There is an AES paper on it from 2006: http://www.aes.org/e-lib/browse.cfm?elib=13720 Before this work the axial tweeter response was pretty compromised on concentric drivers of this type. At the same time as this development a lot of work was done on getting a dome structure that was as rigid as possible.

Following that we've done a lot of work on the midrange to get the driver breakup above crossover. Again, there is an AES paper from 2009 that describes how this was done for the Concept Blade Uni-Q: http://www.aes.org/e-lib/browse.cfm?elib=15041 Incidentally, this driver included a flexible seal between the tweeter and the midrange cone.

Then came the Z-flex style surround I mentioned above, primarily for Uni-Qs intended for 2-way operation. And then the tangerine waveguide to improve the dispersion at the very top end of the driver, which again took a huge amount of design and research time.

All in all it has taken a number of different developments to get where we are at the moment.

The Genelec 8260A was launched in around 2010. I've only ever heard the speaker at shows so I can't really comment much on the sound. Just looking at what they did with the driver arrangement I have to say I'm quite impressed, they have done a good job and there are some neat touches. There are also some clear differences between their approach and ours, which is a good thing I think. You might have missed this by the way: http://www.genelec.com/documents/other/Genelec%20GP%20Partnership%20PR.pdf

For the production version of the Blade we dropped the inner air seal because we found that it restricted the MF cone movement too much. It might be a different case in the 8260a depending on their output requirement and LF/MF crossover frequency. With careful design of the geometry of the tweeter/mid gap (and the area behind) we can get a ripple free tweeter response without the seal.

For instance below is the MF/HF section of the Blade measured at 1m on axis with the tweeter. Keep in mind that this in the final loudspeaker so includes everything (crossover, cabinet diffraction etc.)

Kind regards, Jack.

 

[steve_1979]

Thanks for your replies and the interesting web links (some light hearted Christmas reading to get through there).

All the best to you and your family over the holidays.

 

[Vladimir]

A new video from my favorite loudspeaker designer, Laurence Dickie.

 

[shkumar4963]

Here are some thoughts from someone (not me) who used to test amplifiers at NRC Canada.

The bottom line would be how the amp compared to any number of expensive and low-cost alternatives.

The way to do this would be to pick up an A/B switchbox. Radio Shack used to offer a multi-input line-level switcher for adding additional components to a simple audio rig, and something like that could be adapted for use in a dual-amp face off. (An ABX comparator would be better, but it costs a lot more than a simple line-level switch box.) One of the amps being compared, of course, would have to have level controls so that the levels could be precisely matched before doing the comparing. I suggest using random pink or white noise as a source for doing this level matching.

I did this kind of comparing both with the Radio Shack device and also with a comparator that Tom loaned to me. I did a lot of comparing and in ALL of those faceoffs but one I simply NEVER could hear differences between a variety of power amplifiers, integrated amplifiers, and the amp sections of receivers. (The one time I did hear a difference happened just before a "used and very cheap" amp being evaluated started to visibly smoke.) This series of comparisons included both rather expensive and powerful amps and some rather cheap ones like the AudioSource Amp-One I had on hand for comparing work. The AudioSource amp always worked like a charm.

Yes, super amps MIGHT have some advantages, especially if one likes accurate meters. Most have way more power than cheaper versions (although the Crown XLS units I got from Parts Express were relatively cheap at $300 each and they had 350 wpc into 4 ohms and over 500 into 2 ohms), and some (not all, by any means) are built to last longer than budget types. However, in terms of audible advantages, the super-duper and overkill components used to build some of the things mean not much at all. They might last longer (100 years instead of just 20), but in terms of practical and audible performance they are just amps. Amps is amps, as they say.

I am not saying that it makes sense to go cheap when it comes to amps (although that is what I have done), but, beyond the power required if the speakers are very inefficient and the listening room is huge, if one is expecting better soundstaging, more realistic depth, more detail, etc. when upgrading to a super amp from a more mundane version they are wrong.

Bottom line, go test amplifiers using ABX switch and equalize volume using Pink noise before starting the test. Keep the change over time less than one second. If you don't hear the difference don't buy the amplifier.

 

[Vladimir]

Most amps don't make an audible difference regarding sound refinement, resolution, musicality, but they sure do have differences at their primary job, amplifying a signal . And we certanly shouldn't ignore the psychological appeal from how the industrial design makes you feel, the 'tribe' you join when you buy into a hi-fi concept and the brand heritage etc.

Anyways, let's stick to the topic about speakers. *biggrin*

 

[shkumar4963]

Most amps don't make an audible difference regarding sound refinement, resolution, musicality, but they sure do have differences at their primary job, amplifying a signal . And we certanly shouldn't ignore the psychological appeal from how the industrial design makes you feel, the 'tribe' you join when you buy into a hi-fi concept and the brand heritage etc.

Anyways, let's stick to the topic about speakers. *biggrin*

This is hard to believe as there is a healthy hifi amplifier industry ( manufacturers, dealers, reviewers and forums) and it is hard to sustain it without any "hearable" differences. What am I missing?

My dealer does not allow use of A/B switch so hard to tell a difference since he takes about 10 minutes to change amplifier and my audio memory is not that good.

 

[shkumar4963]

Most amps don't make an audible difference regarding sound refinement, resolution, musicality, but they sure do have differences at their primary job, amplifying a signal . And we certanly shouldn't ignore the psychological appeal from how the industrial design makes you feel, the 'tribe' you join when you buy into a hi-fi concept and the brand heritage etc.

Anyways, let's stick to the topic about speakers. *biggrin*

This is hard to believe as there is a healthy hifi amplifier industry ( manufacturers, dealers, reviewers, forums and most importantly customers) and it is hard to sustain it without any "hearable" differences. What am I missing?

 

[Vladimir]

My dealer does not allow use of A/B switch so hard to tell a difference since he takes about 10 minutes to change amplifier and my audio memory is not that good.

The big revolution in Hi-Fi happened in the 60s and 70s. The gear that was always stacked on shelves and demonstrated via a switch, became a proper customer demo experience where the dealer sets a system of components customized depending on the customer's wallet, needs, preferences... Every neighbourhood and town got a hi-fi shop and as it happens in any lifestyle industry, some interesting ideas were created. In Hi-Fi those were audiophile cables, burning in, qualitative differences in amps and digital sources, musicality, PRaT etc.

And now 50 years later ironically some want the switch demo back. *biggrin*

 

[Jota180]

Most popular does not mean correct. Of course in general tech has moved on in terms of sound quality. But this applies to a very small percentage. I would confidently say about only 5% the rest are just nice looking HIFI with horrible sound. To me the sound the HIFI industry promotes sounds hard, bright & disjointed.

You may have a large sensitivity mismatch between digital player output and amplifier input. That's not too unusual.

 

[Vladimir]

The Future

If you relax and take a mental journey to the 22nd Century, it is easy to imagine the perfect loudspeaker. It would made of an immense number of tiny point sources that would create a true acoustic wavefront (or soundfield). Resonances due to massive drivers and cabinets would be a thing of the distant past. A host of distortions (harmonic, intermodulation, crossmodulation, frequency, phase, and group delay) would be utterly absent ... the sound would be literally as clear as air itself.

This perfect loudspeaker would be made of millions of microscopic coherent light and sound emitters, integrated with signal processing circuits all operating in parallel. (Similar in principle to present-day military phased-array radars, with tens of thousands of tiny antennas with individual electronics subsystems.)

It would be "grown" by nanotechnology and operate at the molecular level, appearing simply as a transparent film when not in operation. Let your imagination roam free ... this device also has access to all sounds and images ever recorded, and an instantaneous link to billions of similar devices. The primitive 20th Century technologies of telephones, movies, radio, television, hi-fi stereo, and the World Wide Web converge into an apparently simple technology that is transparent and invisible.

The Past

Contemporary speakers, for all of their faults, are better than most speakers of the Fifties. Very few "hi-fi nuts" had full-size Altec "Voice of the Theatre" A-7 systems, Bozak B-305's, 15" Tannoys, or Klipschorns. The typical enthusiast had to endure University, Jensen, or Electro-Voice 12" coaxial drivers in large resonant plywood boxes with a single layer of fiberglass on the rear wall. A large cutout served as the vent, resulting in boomy, resonant boxes tuned much too high, with a 6 to 12 dB peak in the 80 to 150 Hz region. (Have you ever heard a restored jukebox?)

The coax, or worse, triax drivers went into paper cone breakup at 300 Hz and above, cavity resonances (due to the horn element mounted in the cone driver) at 800 Hz and above, horn breakup throughout the working range of the short horn, and phenolic diaphragm breakup at 8 kHz and above. A "good" driver of this type usually had a plus/minus tolerance of 4 to 8 dB, and it took a lot of judicious pen damping to get it to measure that well.

It wasn’t for nothing that early hi-fi systems acquired a "boom-and-tweet" reputation. The sound quality was closer to an old neighborhood theatre, or amusement park skating rink, than a modern speaker. The tube electronics helped sweeten much of the coarseness, but they couldn't rescue the really bad loudspeakers of the day. True, the first-generation Quad, the RCA LC-1A, the Tannoy, and the Lowther compare well with modern systems ... but they were rare, and very expensive, at the time. How expensive? The classic speakers cost as much as a new Volkswagen or the down payment on a house!

Peering through the looking-glass of time, we can see that the old designers had no consistent way of modeling or predicting the bass response, and the materials available for tweeters were very poor by modern standards. Today, accurate, design-by-the-numbers bass is taken for granted, and modern tweeters really are superb.

Where modern systems fall down is midrange performance, which doesn’t lend itself to the computer design tools that are so convenient in the bass and treble range. The sparkle and dynamism of the best classic speakers is in the midrange, the most important, and yet the most challenging, part of the entire spectrum. Progress in the midrange region has been slow for many reasons.

...

The Art of Speaker Design - Part 1

The Art of Speaker Design - Part 2

 

[Frank Harvey]

I miss Tomorrow's World as well.

 

[Vladimir]

 

[Native_bon]

Most popular does not mean correct. Of course in general tech has moved on in terms of sound quality. But this applies to a very small percentage. I would confidently say about only 5% the rest are just nice looking HIFI with horrible sound. To me the sound the HIFI industry promotes sounds hard, bright & disjointed.

You may have a large sensitivity mismatch between digital player output and amplifier input. That's not too unusual.

My system is fine. Cannot be happier. Got my input trim of the AVR450 set to 4V RMS.

 

[shkumar4963]

Where is everyone. ...

 

[Vladimir]

It's the holidays dude. Chat will ramp up after NY night.

 

[DocG]

It's the holidays dude. Chat will ramp up after NY night.

Clicky

 

[shkumar4963]

Loved that Clicky link.

Happy Holidays.

 

[shkumar4963]

We tend to do the majority of our testing on large amps that we know well. We do this so that we focus on maximising the speaker performance in an absolute sense. The danger of using a lower performance amp is that you start to tune the speaker to compensate for the character of the amp. We generally always will then do some final testing on typical partnering equipment to check there are no nasty suprises.

Kind regards, Jack.

Thanks Jack. What "typical parterning equipment" have you used to test LS50. I know that you may not want to reccomend an amplifier. So, I am just asking for names of amplifiers that you have used in the past that were OK with LS50. I am assuming that these typical partnering amplifiers are in the range of US$500 to US$1000. Any lower priced amp that sounded OK?

 

[Jota180]

Most popular does not mean correct. Of course in general tech has moved on in terms of sound quality. But this applies to a very small percentage. I would confidently say about only 5% the rest are just nice looking HIFI with horrible sound. To me the sound the HIFI industry promotes sounds hard, bright & disjointed.

You may have a large sensitivity mismatch between digital player output and amplifier input. That's not too unusual.

My system is fine. Cannot be happier. Got my input trim of the AVR450 set to 4V RMS.

What we can say with absolute precision is you're now decades older and decades more decrepit! lol

Your ears have gotten pregressively worse year on year. If you work in loud environments, like concerts, ride motorcycles then even more so. You ability to hear higher frequencies is probably closer to a 90 year olds than an 11 year olds.

You'll probably come back now and tell me science is astounded by your bat like ears!

 

[Vladimir]

You'll probably come back now and tell me science is astounded by your bat like ears!

Bats typically hear 15 kHz to 90 kHz. Golden ear audiophiles with beryllium dome tweeters are superior.

 

[Native_bon]

Most popular does not mean correct. Of course in general tech has moved on in terms of sound quality. But this applies to a very small percentage. I would confidently say about only 5% the rest are just nice looking HIFI with horrible sound. To me the sound the HIFI industry promotes sounds hard, bright & disjointed.

You may have a large sensitivity mismatch between digital player output and amplifier input. That's not too unusual.

My system is fine. Cannot be happier. Got my input trim of the AVR450 set to 4V RMS.

What we can say with absolute precision is you're now decades older and decades more decrepit! lol

Your ears have gotten pregressively worse year on year. If you work in loud environments, like concerts, ride motorcycles then even more so. You ability to hear higher frequencies is probably closer to a 90 year olds than an 11 year olds.

You'll probably come back now and tell me science is astounded by your bat like ears!

Well will let others decide from your post.

 

[shkumar4963]

I have seen that when any speaker is reviewed the first thing they do is to show you its anechoic frequency response curve. We also know that using an active equalization, one can adjust the frequency response curve upto +-6 dB or even more. There are many DSP based EQ available that can do that and there are many older passive EQ also available. Besides in room frequency response curve is much different in any case where most peorple listen to their speakers.

In this case, why so much attention to flat anechoic frequency response curve?

I had read a paper by Harmon Kardon that showed that in large listener testing the speaker with flatest anechoic frequency response curve was preferred even though all listening tests were conducted in non-anechoic conditions. What could be the reasons? I am assuming that no EQ was used in that study.

Does a speaker with a flat anechoic FR curve sound better than a speaker with poor anechoic FR curve but adjusted using active or passive EQ?

Is there a difference? Why?

 

[steve_1979]

I have seen that when any speaker is reviewed the first thing they do is to show you its anechoic frequency response curve. We also know that using an active equalization, one can adjust the frequency response curve upto +-6 dB or even more. There are many DSP based EQ available that can do that and there are many older passive EQ also available. Besides in room frequency response curve is much different in any case where most peorple listen to their speakers.

In this case, why so much attention to flat anechoic frequency response curve?

I had read a paper by Harmon Kardon that showed that in large listener testing the speaker with flatest anechoic frequency response curve was preferred even though all listening tests were conducted in non-anechoic conditions. What could be the reasons? I am assuming that no EQ was used in that study.

Does a speaker with a flat anechoic FR curve sound better than a speaker with poor anechoic FR curve but adjusted using active or passive EQ?

Is there a difference? Why?

I've read (although my understanding is limited) that while equalisation can be used flatten the frequency response but in doing so it will also effect the phase which as far as the sound quality is concerned it is a big trade off.

 

[davedotco]

I have seen that when any speaker is reviewed the first thing they do is to show you its anechoic frequency response curve. We also know that using an active equalization, one can adjust the frequency response curve upto +-6 dB or even more. There are many DSP based EQ available that can do that and there are many older passive EQ also available. Besides in room frequency response curve is much different in any case where most peorple listen to their speakers.

In this case, why so much attention to flat anechoic frequency response curve?

I had read a paper by Harmon Kardon that showed that in large listener testing the speaker with flatest anechoic frequency response curve was preferred even though all listening tests were conducted in non-anechoic conditions. What could be the reasons? I am assuming that no EQ was used in that study.

Does a speaker with a flat anechoic FR curve sound better than a speaker with poor anechoic FR curve but adjusted using active or passive EQ?

Is there a difference? Why?

I've read (although my understanding is limited) that while equalisation can be used flatten the frequency response but in doing so it will also effect the phase which as far as the sound quality is concerned it is a big trade off.

I'm not sure that is the case using DSP, doing the eq in passive crossovers will clearly screw up the phase, extra inductors, capacitors etc.

Need to look that up.