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Only Incremental Improvements: KEF LS50 to LS50 Meta

To Doug Schneider,

It was with a great deal of curiosity and interest that I read your review of the new KEF LS50 Meta loudspeaker.

I have five of the original LS50s in my theater and, having read the sales pitch, I was most curious how the Meta would measure. Pulling up the old SoundStage! Network measurements for the LS50 to compare, it looked as though you were just measuring another LS50. The differences, for the most part, could be put down to standard production variations as much as to any new refinements.

It was interesting that they really couldn’t improve the cabinets at this price point, but not altogether surprising.

The biggest difference I can see in KEF’s literature is that their Metamaterial Absorption Technology virtually eliminates the back wave of the tweeter and reduces total harmonic distortion (THD) by around 0.03%. So that’s, maybe, a 4dB reduction. I’d consider that to be no more than an incremental improvement.

The LS50 has as close to the ideal temporal response as you can get with a passive speaker. That being said, it’s not perfect -- it can be improved by forgoing the passive crossover and biamping the speaker with a digital speaker processor. Using FIR and steep IIR filters, you can tweak these speakers to be as close to perfect as they can be. Add in some serious digital signal processing (DSP) like Dirac or DEQX and you will have perfect group-delay response.

In other words, the improvement in sound quality from the slight reduction in THD afforded by the Meta can easily be matched by using room correction and an effective DSP crossover with the original LS50s. Yes, this is a more expensive way to go, but it does offer greater control than you can get with the wireless version of the Meta. Whether the sound would be drastically better is another story.

One thing that does suck is that KEF doesn’t offer a single LS50 Wireless II to use as a center speaker, so that model is out for me.

So, as it stands, I’m only three stereo Purifi Audio Eigentakt amps (for left, center, and right) and a couple of DSP units away from having as great a surround system as you can get with my LS50s. I’m good with that! And no, I won’t be going the active route with the surround speakers, either.

So, Doug, thanks for another very informative review.

All the best,
Jeff Henning
United States

Thanks for reading and responding. It’s true the differences between the LS50 and LS50 Meta are small, so there probably are other ways to improve the sound of a system rather than swapping out the older model for the newer one. Still, I think fans of the original will be pleased by the small improvements and, in many cases, will want to make the move. . . . Doug Schneider

KEF LS50 Metas with a Sub

To Doug Schneider,

I enjoyed the KEF LS50 Meta review.

It would be interesting if someone matched them with a quality subwoofer and then compared them to more expensive speakers with better bass. Would such a setup be better for less money?


I agree that matching the new LS50 Metas with a topflight subwoofer would be a good thing to do. In fact, I hope someone who has writes in. But time permitting, it might also be something I do. . . . Doug Schneider

Taking the Fun Out?

To Doug Schneider,

You are taking all the fun out of home audio by deviating from faith-based, subjective audio reviewing.

Just tell everyone that the item being reviewed is fantastic in every way and it’s the best thing you’ve ever heard -- with the possible exception of something similar you reviewed 18 months ago that was just slightly better. Now that’s audio reviewing.

Your scientific approach is ridiculous. What does science have to do with audio?

As for the IsoAcoustics zaZen I isolation platform, I’m not surprised that its performance was marginal. I have IsoAcoustics Aperta speaker platforms under my KEF LS50s, which are stacked on Rythmik Audio subwoofers on the left and right channels in my home theater. I wasn’t worried about the speakers vibrating on the subs, but rather, the vibration of the subs modulating the sound from the speakers. While the Apertas helped, their efficacy was not what I’d hoped for. To improve their performance, I then added Sorbothane hemispheres to the top and bottom of the platforms and, voilà, they work great! If I turn the mains amp off and crank up the subs, the LS50s hardly vibrate to the touch.

I already knew that such issues are highly dependent upon the mass of the item that’s being isolated and the frequencies to be damped, but your review really drove it home. Too light or too heavy an item and it works poorly or not at all. Also, that several damping layers are better than just one. Honestly, a platform made from a piece of Corian or a 1/4″ carbon-fiber plate sitting on Sorbothane hemispheres could work way better and be much cheaper. Or even 3/4″ plywood. And also, what is the platform standing on? How sturdy is that and how much is it vibrating? A turntable on a magnetically levitated concrete slab that’s next to a subwoofer is still going to get the crap vibrated out of it through the air when you turn up the volume.

This product isn’t exactly snake oil, but one size does not fit all. That is its failing.

I haven’t played a record in over 15 years, but my turntable sat on the concrete mantle of a huge stone fireplace throughout the 1990s until 2004. That is acoustic isolation -- unless there’s an earthquake!

All the best,
Jeff Henning
United States

I can appreciate a little sarcasm from time to time! However, I’m glad you pointed out that the IsoAcoustics zaZen I platform isn’t “snake oil.” It’s not. But as you pointed out, the effectiveness of the zaZen platform will have a lot to do with what’s placed on it and what it’s sitting on. I still think it’s a good product for the price. . . . Doug Schneider

Thanks for the Purifi Eigentakt Measurements

To Doug Schneider,

I am writing to thank you for your most recent article on the measurements of the Purifi Audio Eigentakt amplifier. I found it so enlightening and revealing that I’m seriously considering the purchase of the NAD Masters M33 integrated amp, even though some of its measurements are not quite as good as the Eigentakt itself.

I am a blind person and your article was most useful because of the written descriptions of what was shown by the graphs -- very useful for those who can’t see.

May I make a suggestion? I realize that this might be a bit more work, but providing brief explanatory notes on the highlights of speaker measurements you publish would be a huge help. At the moment, only the graphs are shown, with the exception of the sensitivity ratings.

Again, a whole lot of thanks!

Yvon Provencher

Thank you for the feedback. You make a good point about the speaker-measurement graphs -- let me see what we can do going forward. . . . Doug Schneider

Perfect Amplifiers for Under $3000?

To Doug Schneider,

What a great job with your Purifi Audio Eigentakt measurements review.

Purifi Audio’s Bruno Putzeys has stated something to the effect that audio amps are becoming commodities in so much that, at this level of performance, they have no sound signature; so, the only consideration for the consumer is the output power needed. Seeing these measurements, he’s right.

Given that most listening rooms have a background noise of 25 to 30dB and that it’s really not healthy to regularly listen to music at levels higher than 105dB, we have, at best, a range of 80dB to enjoy our music. The human auditory system can discern sounds 20 to 30dB into background noise. So, this means that we have a total range of 100 to 110dB for listening.

Considering all of this, distortion and noise are inaudible with an amp like the Eigentakt or Benchmark’s AHB2.

As long as an amp is load invariant driving a passive speaker with a crossover, it is considered to be perfect. Of course, passive crossovers are the muck stirred up in the water. Their reactive nature is problematic, but a DSP can negate the specific variations caused by a passive speaker’s impedance. Going fully active with DSP correction and FIR crossovers will negate all of the passive problems. So, with these amps in an active system, the amp is no longer a factor in the sound quality at all.

You can get a Nord Acoustics stereo Purifi amp with all its options for about $2400. For a triamped system that uses powered subs, two amps to drive the mains would cost less than $5000. Used in this way, the Eigentakt would be as perfect as an amp can be. To our hearing, it would be perfect.

So that’s it. Amps, now, perform better than we can hear and the two best stereo amps on the planet cost $3000 or less.

While the world runs toward self-destruction, we are making some fantastic audio equipment.

Jeffrey Henning
United States

Let’s hope the world gets better and more people can appreciate these wonderful amplifiers. Thanks for your feedback. . . . Doug Schneider

Does Purifi Represent a Turning Point?

To Doug Schneider,

I have been involved with audio/hi-fi for many years and it really seems to me that there are more and more manufacturers and importer-distributers who are solely trying to grab the brass ring. They are not at all interested in introducing the next generation to quality audio reproduction. It appears to me that there is a never-ending number of these industry people who want to sell higher- and higher-priced gear to a shrinking customer base. There is no big picture, and, as a result, they will be responsible for their own demise.

My interest in audio/hi-fi began as a young consumer, developed later as a partner in a specialty audio shop for six years, and continued as an informed consumer for many years. In actuality, few, if any, improvements have been made since the ’70s to mid-’80s. I recently listened to a system belonging to one of our old customers, consisting of Rogers LS3/5A speakers, a Dynaco ST-70 amplifier, a passive ladder control, and an early Burr-Brown-based multibit DAC. I listen to most of what is offered today and it in no way approaches this system. It’s fantastic. I heard a pair of Dynaco A-25s about a year ago and they were really nice. No wonder they were the all-time best-selling loudspeakers. Yes, there are fine examples made today; however, on a price and general availability perspective the consumer is at a loss. We simply do not need audio jewelry that costs as much as or more than our car or our home.

I believe that we are at a turning point and technology will assist in bringing the experience of quality audio reproduction to a wider audience. I was hopeful about the Tripath-based amps a few years ago as they were inexpensive and very good. Then Texas Instruments bought out Tripath for their patents and disposed of the company and its products. So, with all of that, I believe the likes of Benchmark Media Systems and Purifi Audio are on the right track. Original thought and more affordable applications will hopefully expose quality playback to a larger audience. I would really like to see a review of the entire Benchmark stack of the basic DAC3 B, the LA4 line amp, and AHB2 stereo amp rather than a random sample of each component. This might be an interesting project for you guys to take on. Another product line to look at is the PSI Audio brand of professional powered monitors. They are very good; they have been around for more than 35 years and started as an OEM for Studer monitors before Harman bought out Studer. This is a unique line of high-quality speakers utilizing class-G amplification.

I found your article and review of the Purifi amplifier and monitors very interesting. I am curious as to which of the Hypex switching power supplies was used in the prototype amplifier. In reviewing the Hypex DIY parts site, it seems that there are three power supplies that look similar to the one used in the amplifier that you reviewed: SMPS1200A180, SMPS1200A400, and SMPS1200A700. Do you know which of these is the unit used in the amplifier you wrote about?

I do believe that this is the future of audio/hi-fi. Primarily, I have used push-pull directly heated triode amplifiers. With the eventual demise of NOS power tubes and the importance of energy efficiency going forward, it is important to find alternatives that can perform to expectations. It was only a matter of time until switching amplifiers matured to a high standard. This benefits everyone and will make the hobby more accessible to more people. This can only be a good thing as the current entrance fee is simply out of reach for many.

Thank you for the article and bringing this information forward. I find the work in this area to be eye-opening and of great interest.

Best regards,
John Shepherd
United States

What you wrote really struck a chord with me -- I mostly agree. But does Purifi amplifier technology represent a turning point for hi-fi? I believe it does, but we’ll have to see what the marketplace says. By the way, the Hypex power supply used in their evaluation amplifier is the SMPS1200A400. As a rough estimate, then, combining that power supply with two Purifi 1ET400A amp modules and the Purifi gain board -- which they sell as a package called Eval1 -- plus wiring and case should cost less than $1500 USD. That represents incredible value for such high performance. . . . Doug Schneider

Purifi, Pass Labs, or Hegel -- In Search of an Amplifier for Magico A5s

To Doug Schneider,

I read your review of the Purifi Audio 1ET400A amplifier and wanted to reach out to ask a question.

First of all, I am not an audiophile -- I have had to Google what a source, a DAC, an amplifier, and so on, are. I ended up investing in a pair of Magico A5 speakers, and my challenge now is to build a setup around the A5s while entering this (confusing) hi-fi world.

My first thought was to go with a high-end integrated amp, such as Hegel’s H590 or Pass Labs’ INT-250 -- both apparently used by Magico themselves. A more hi-fi–savvy friend of mine described these amps as “mustangs -- raw power but not very modern" and recommended looking into the latest Purifi amps and a decent source like Lumin.

As a technology person, I am attracted by the story of Purifi Audio and their goals, but I lack the reference point and experience to judge whether this is a good fit. Could a Purifi setup drive the A5s, and how would it differ from high-end integrated amps like Hegel and Pass Labs?

Best regards,

You certainly have a great set of speakers to partner with a fine amplifier! The trouble is obviously figuring out what to choose. In that regard, I agree with you that the world of hi-fi can be confusing -- mostly because there are so many choices, but also because everyone out there seems to have a different opinion. Obviously, this response reflects my own opinion on what you should do.

Because you’re new to hi-fi, I think the fewer components there are in your system, the better off you’ll be. Therefore, you’re on the right track considering an integrated amp for your speakers. An integrated amplifier has, at minimum, preamplifier and power amplifier sections all in one case. Going at it this way will give you great sound without a lot of complexity or fuss.

But before I get into what I’d recommend, please understand that the Purifi Audio amplifier that I’ve been writing about isn’t a commercial product -- it’s an engineering sample that uses their 1ET400A amplifier modules, which they supply to other companies to implement in their amplifiers. As a result, no one can buy this unit at a store. But even if you could, it’s only a power amplifier, so you’d need a source, such as a digital-to-analog converter (DAC) with a volume control, which is what your friend is recommending (a Lumin product), or you’d need to marry up the source with a preamplifier so you can adjust the volume. But I have some good news if you want to go the Purifi route . . .

The first company to license Purifi’s 1ET400A amp technology was NAD, with their Masters M33 integrated amplifier. Roger Kanno just reviewed the M33 for us and absolutely loved it, and he pointed out it has more features than most integrated amplifiers do. Not only does it have preamplifier and power amplifier sections, it also has a built-in DAC, a moving-magnet/moving-coil phono stage, Dirac Live room correction, and streaming capability based on the excellent BluOS software platform (developed by Lenbrook Industries, NAD’s parent company), among other functions. The M33 also puts out a decent amount of power -- it’s rated at up to 200Wpc into 8 ohms, which is plenty for typical setups.

The Pass Labs INT-250 and Hegel Music Systems H590 integrated amps you mentioned are also good options, with both providing more power than the M33 -- the INT-250 is said to deliver 250Wpc into 8 ohms, while the H590 is claimed to output 301Wpc into 8 ohms. Magico speakers tend to like quite a bit of power, so the INT-250 and the H590 might be better options than the M33. However, that will depend a lot on the size of your room and the volume levels you listen at.

The main downside of the INT-250 is that it is a barebones integrated amplifier -- there are no additional features beyond its preamplifier and power amplifier sections. As a result, you’ll need an external DAC if you plan to play digital music (which is likely since that’s what most people listen to these days), as well as an external phono stage if you’re planning to use it with a turntable -- something you might want to get into later. Therefore, for you, the better choice between these two is probably the more powerful H590. In addition to being an integrated amplifier, the H590 has an excellent built-in DAC and provides streaming capability via UPnP, which isn’t as full-featured as BluOS but still gets the job done. The H590 doesn’t have a phono stage, mind you, or the other features of the M33 I mentioned, so you’ll have to determine what your exact needs are to know if it’s right for you. Chances are, it has enough features.

All told, for your situation, I’d go with the NAD Masters M33 or the Hegel Music Systems H590, with the latter having more power and a decent set of features and the former having a plethora of features and less power -- though the power it delivers is based on Purifi’s cutting-edge amplifier tech, which seemed to intrigue you. I have little doubt one of those products will fit your needs perfectly. You make the final call. . . . Doug Schneider

Bryston and the Summer of 1978

To Doug Schneider,

Back in 1978, I was a very fortunate college student in that I found a way to purchase a pair of Rogers LS3/5a loudspeakers. In 1980, my roommates and I were robbed twice, which, along with momma’s State Farm insurance plan, led to a backup record player -- a Harman Kardon “twenty” complete with factory-aligned (and correctly aligned) Ortofon Concorde pickup.

One evening, courtesy of a classmate’s uncle, I hooked up a loaner set of electronics -- an Audio Research SP-3 preamplifier and a Bryston 4B amplifier (and now you know the connection). THAT created some magic to my then unjaded ears. Rickie Lee was singing when a roommate walked in -- he stopped, listened, and said, “It sounds like she’s in the room!”

(Indeed, it did.)

Later that year, one of my other roommates blamed me for turning him into an audiophile -- I blame those BBC monitors.

Thanks for your article.

Best regards,
Jim Susky
United States

P.S. Thanks also for the photo of an “original” 4B -- a plain Jane that really “put out” for a few hours.

That’s a great story! . . . Doug Schneider

Taming the Triangle Borea BR03 Speakers' Treble

To Doug Schneider,

I enjoyed reading your review of the Triangle Borea BR03 speakers. I recently ordered a pair and have found them very enjoyable aside from some occasional brightness. I’m just using an Emotiva BasX A-100 amp, so I’m wondering if that’s what may be causing the brightness. Do you think it would make sense to try a different amplifier, or am I just coming up against the nature of these speakers? If the former, I would be very grateful for a sub-$500 power amp recommendation that would smooth out the sound.

Thank you very much.

United States

I wouldn’t blame the amplifier for the brightness -- it’s, to use your words, “the nature of these speakers.” If you look at our acoustical measurements of the BR03, you’ll see the tweeter’s output is fairly high at around 5kHz and 10kHz, particularly on-axis (i.e., directly in front), which is the cause of that brightness.

While some tubed amplifiers do roll off the highs, using an amplifier to tame brightness isn’t a good idea -- no good amp is likely going to diminish the highs all that much unless it has a tone control for the treble or some sort of equalization to let you turn the treble down. And don’t think about changing the cables or other electronics in your system because replacing them won’t do that much to reduce the highs, either.

I suggest working with speaker placement and room acoustics. Let’s start with speaker placement. Definitely don’t have the speakers toed in so they’re pointing straight at you. Instead, start with no toe-in at all, meaning the speakers are firing straight into the room. Set up that way, the tweeters’ on-axis output won’t be coming straight for your ears (I’m assuming you’re positioned several feet from the speakers and between them). This way, you’ll be hearing more of the off-axis response of both speakers, which isn’t as bright.

As far as room acoustics go, soft materials help to absorb high frequencies. I don’t know if your floor is hard or carpeted, but if it’s hard, consider throwing an area rug down large enough to fill up most if not all of the space between the speakers and your listening position. The rug will help to soak up some of the highs as well as reduce reflections from the floor. Similarly, soft materials on sidewalls (some people hang area rugs on them) can help too. . . . Doug Schneider

KEF R11 vs. Reference 1

To Diego Estan,

I appreciated your review of the KEF R11 from last summer, and I was wondering if you had any thoughts about how it compares to the bookshelf Reference 1 mounted on a floor stand. I’m debating the two for my room, which measures 20’ deep by 25’ wide.

I have heard the R11s live and loved them. The Reference 1 wasn’t available in the listening room.

Thanks for any thoughts you might provide.

P.S. I’m willing to entertain the use of subwoofers with the Reference 1s.

United States

Thanks for your kind feedback. I haven’t had the opportunity to listen to any model from the KEF Reference series in my home, but I’ve reached out to my esteemed SoundStage! colleague Hans Wetzel, who owns Reference 3s and is quite familiar with the R11. He describes the R11’s style as “utterly coherent from top to bottom” and says that it is well-built and well-appointed and that it offers nearly full-range sound.” He considered making the R11 his reference speaker, but his space is too small.

Instead, Hans picked up a pair of Reference 3s, which he highly recommends. The Reference 1 is voiced almost identically to the Reference 3, according to our measurements. You might make some sacrifices in terms of extension below 40-50Hz and ultimate output, but they are more than made up for by the improvements in nearly every other performance parameter.

Personally, if I had to choose between the R11 and Reference 1 (without subs), I’d go with the R11. Bass performance is just too important to me, and in a room as big as yours I fear the Reference 1s would leave me wanting more. If paired with one or, ideally, two subs, I’d pick the Reference 1. First, a good sub will output deeper, more powerful bass compared to all but the most expensive full-range speaker/amp combos. Dollar for dollar, in terms of bass performance, subs win. Second, you can place the sub(s) in the room for optimal bass response, which you can’t really do with towers since they must be placed for optimal imaging. These differences become more significant the more work you put into dialing in the subs -- e.g., placement, volume setting, bass management and crossover point, and, for greater performance, measurements and EQ.

Best of luck! Please let me know what you end up with. I know you’ll be pleased with the sound either way. . . . Diego Estan

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