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The Linkwitz LX521.4 Dipole Loudspeaker Review

I first heard the Linkwitz 521.4 at Axpona 2023. After only a few minutes of listening, I knew this speaker was doing something different, and maybe better, than most other speakers on the market. After more than an hour of listening, I was pretty sure Linkwitz was on to something, so I requested a review sample. Under more familiar conditions, with more familiar musical choices, I wanted to explore the question: Is the Linkwitz 521.4 truly deserving of the term breakthrough? Because “this thing is a breakthrough” kept floating through my mind at Axpona.

How Would We Know A Breakthrough If It Hit Us In The Ears?

I first need to address what we really mean by “breakthrough” because it’s an overused word. In a click-oriented media world, superlatives have become more than slightly overused. There are “awesome socks” and “you won’t believe what this microprocessor offers” and “game-changing breakfast”. It’s more than little hard to believe the adjectives that people are throwing around. With that in mind, and to avoid insulting your intelligence, I’m going to give you a definition of breakthrough that I think you’ll say is reasonable. If not, I’ve saved you a bunch of reading.

What I mean by a breakthrough, and what I mean specifically in the context of this speaker, is something that is new, in the sense we haven’t heard it before or we haven’t heard it at this price point or we haven’t heard it nearly done as well. And a breakthrough must include a sonic difference that is musically meaningful or significant. So, it’s quite different and it’s musically beneficial. That’s what we mean by breakthrough.

I want to give you some examples of products, loudspeakers that I think historically have met this definition. Those of you who have been around for a while will know what I’m talking about. This may not be that meaningful to the rest of you. But here is a list of speakers that I have experience with that did things that other speakers didn’t do, by a longshot. This list isn’t comprehensive; I’m just pointing out that there are a whole bunch of speakers that I think could meet the definition that I just gave. Here are some “breakthroughs” of the last 60 years:

Quad ESL 57

IMF Reference Standard Pro Monitor

Magnepan Tympani 1D

Martin-Logan CLS

Avant Garde Trio

mbl 101e

Now, contrast sometimes helps us understand what we’re talking about. I want to contrast this list with a list of speakers that meet the definition of “good all-rounders”, particularly good all-rounders that deliver some notable incremental benefit. I don’t want to cast aspersions on those by implying that breakthroughs are better than balanced engineering. Not at all. Good all-rounders are the speakers you probably end up buying and it makes sense to buy because they’re good on many musical factors and you want to listen to music. You don’t want to have hi-fi that demonstrates some new approach or some new technology, but which is also annoying or distracting. You want music. Here’s another list and this is a list of speakers over that same period that meet the definition of a good all-rounder judged on musical criteria. Again, not a comprehensive list, just examples:

Large Advent

Spendor BC1

Vandersteen 2

Wilson Watt/Puppy

Revel Salon

Magico Q7

One of the things you’re going to notice, I think, is that a lot of the speakers that are on the breakthrough list use some different principle and very often that’s a different driver technology and a different driver layout. Also, and this will become important, but I’m going to point it out now, hopefully you can remember it. A lot of the speakers on the breakthough list are either dipole, omnidirectional or narrow dispersion. They’re really different from conventional box speakers; that is, different from woofer/mid-range/tweeter kind of speakers in terms of their radiation pattern.

But I want to caution here against technological determinism. What Linkwitz brings to the party to an unusual degree, is that Siegfried Linkwitz (the man) clearly defined a theory of how speakers reproduce a soundstage. Then the company that inherited his ideas (Linkwitz passed away in 2018) has built a speaker that conforms to that theory as best they can.

The Linkwitz Model

Siegfried Linkwitz wrote rather clearly about these matters. I am going to paraphrase what I believe he says, and I’ll try to do so in a simple way, by presenting the Linkwitz model. It is important to characterize this as a model because models usefully describe how things work, but they may not be a perfect representation of what actually happens. “Bake the apple pie for 45 minutes at 350 F” is a model, not an atomic or thermodynamic or chemical description of how the sugars change state. The latter would perhaps be interesting, but probably yield a lot of sad faces at Thanksgiving dinner. The former is usable and therefore helpful.

The Linkwitz model says:

  • The positioning of the performers in space is encoded in the recording process.
  • The speakers (and the ancillary equipment needed) send the encoded data to your ear/brain, which is naturally (think in evolutionary biology terms) capable of decoding the data stream and imagining the performers where they were as defined by the recording.
  • The key thing in audio reproduction is for the speakers not to add signals to the data stream that tell your ear/brain to stop suspending disbelief and start hearing the music as coming from the speakers themselves.

The more I think about it, the more I see this as a radically different model of stereo. Lots of people who have lots of experience thinking about these models or paradigms have noted that it is quite hard to move outside the established paradigm. But let’s note how the Linkwitz model is different:

  • In standard stereo, the performers are positioned between the speakers on a stage that runs from left to right and ends at about the centerline of each speaker. In the Linkwitz model, it would seem that a performer outside the leftmost mic (as an example) could be heard to the left of the left speaker. If and because the mic feed data captured that information.
  • In standard stereo thinking, the radiation pattern of the speakers and the resulting reflections are part of what creates a sense of space. In the Linkwitz model, the radiation pattern can easily create potential distortions that weaken the sense of space.
  • In standard stereo, the big thing is the low distortion of the driver/cabinet combination. In a way, this is a “speakers are like amplifiers” model. Much has been gained via this lens. But in the Linkwitz model adds the idea that acoustical distortions are highly significant especially to spatial perception by the brain.

Probably no manufacturer adheres perfectly to one model or another; the above is just meant to contrast how different Linkwitz’s ideas are from what most of us have in our heads.

In practical terms, the Linkwitz model prescribes a few goals for speaker design:

  • Speakers should have consistent directivity with frequency. The ear/brain can detect when directivity changes for a given source because generally that isn’t what happens with sound sources in the wild. The consistent polar pattern (directivity vs frequency) could be omni, dipole or narrow.
  • Speakers must be placed in the room so that reflections do not interfere with the data stream. In particular, all reflections must arrive at the ear more than ~6 or more milliseconds after the direct sound arrives. This allows the precedence effect (an ear/brain feature) to sort source from ambient sound. Practically, speakers must be 3+ feet from sidewalls and preferably more than 4 ft from the wall behind the speakers. The listener must be farther than 3 feet from the rear wall (which is ideally treated to minimize reflections). We comfortably adhered to these guidelines for our tests.

The Speaker Itself

Now, let’s take a look at the Linkwitz 521.4 with these ideas in mind. It is a four-way speaker with a tweeter, upper mid-range, lower mid-range, and two woofers. As you can see, it looks a little bit unconventional, so the fact that it sounds different might not come as a huge surprise when you just look at it.

What’s interesting about it is that it’s a full-range dipole, but one which uses dynamic drivers, so it’s not a planar like an electrostat or a planar magnetic would be. It uses conventional dynamic drivers, yet it is a dipole speaker. That means that the tweeter radiates front and rear (it actually has two tweeters so that the closed back tweeters can radiate front and rear). The upper mid-range radiates front and rear. The lower mid-range radiates front and rear, and the woofers radiate front and rear. So, it’s completely open, with no enclosure per se, just a structure to support the drivers. The dipole arrangement, plus the oddly shaped baffle is to create consistent directivity with frequency.

In addition, each channel, left and right, comes with a dedicated four-way crossover, with equalization for each channel, and five channels of amplification. Five channels because there are two woofers, and each woofer has its own amplifier. The tweeter amplifiers deliver 100 watts, the upper midrange gets 125 watts, the lower midrange gets 125 watts, and the woofer gets 500 watts, for a total of 850 watts per channel. The equalization is there not for user adjustment purposes, but because dipoles roll off at 6 db per octave below a frequency set by the baffle width. Linkwitz has to correct for that to get flat response.

So with the 521.4 you’re buying a mid-sized floor-standing speaker with big amplification, and the fact that the crossover is electronic is nifty, but you would get a crossover in pretty much any speaker you buy. The price point on this is 20,000 euros or $24,000 US, but then you remember you’re also getting left and right amplifiers, and the speaker for $24,000. So, it’s kind of like a $17,000 speaker and a $7,000 amplifier. What I want to impress on you is for something that’s a breakthrough, it’s not super expensive.

Now, if you think of it in speaker terms, it’s not cheap either. $17,000, just to use that number, is not a cheap speaker, but there are many, many, many, many speakers that are above that price point. So, value is part of this equation as well, and if the LX521.4 is a breakthrough that also is good in other conventional terms, I think we’re talking about potentially important value here.

Sound Quality

But so what? Why is the Linkwitz 521.4 a breakthrough when you listen to it? I’ll do my best to describe it, but I will tell you, I strongly encourage you, if you live in a location near an audio show or if you like flying on planes, to go to an audio show and hear a demonstration of this. It is different enough that hearing really helps explain it. Linkwitz also has Linkwitz Lounges, which are demo locations where you can hear the speaker. It’s really fun to hear a demo, I think you’ll enjoy it, and learn something, so I highly recommend it.

What I hear from the 521.4 is the ability to reproduce spatial depth, and spatial width, in a way that goes beyond almost any other speaker. I don’t have a perfect memory and I don’t have a perfect catalog of what every manufacturer makes, but the 521.4 is way up there in spatial reproduction, and I would say right now it delivers a better sense of depth and width than any speaker I remember hearing.

Another way to put this is that the Linkwitz 521.4 gets the image “off the box” to a distinctive degree. The soundstage is not confined to a miniature space between the speakers. The performers often seem to be playing behind the speakers on a stage. The performers sound closer to lifelike in size. And the speakers just seem to be on the stage as ancillary things like stage lights or curtains, rather than as part of the sound creation apparatus. Once you hear a good virtual reality rendition of performers in your room, it constitutes a major shift in your sense of realism and in your suspension of disbelief.

The Linkwitz 521.4 does something else that I don’t really ever remember being consistently done, and that is you can reproduce sound outside the locations of the left and the right speaker. So, the stage width can be wider than the speaker setup with performers almost outside the wall of the listening room. That sense of width can be a big deal. I think it’s particularly important on orchestral music. Robert Greene did a very nice piece recently in The Absolute Sound magazine where he measured the angles of the stage from various listening positions within a concert hall. And the width of the stage is just much bigger than what you would typically have in a stereo setup. But the 521.4 gives you some of that grandeur by presenting the image as wider than wherever you have the speakers located.

Note that this is not image bloat because the Linkwitz speakers can locate the performers more precisely than most other speakers I’ve heard. I wouldn’t say it’s breakthrough level in that regard, but it’s really good at performer placement, which is part of realism. If you imagine a jazz quartet in a club, you get this wonderful sense that the saxophonist is over there and the piano is over there and the drums are in the middle, and there’s a singer here, let’s say, up front. You clearly get the front-to-back depth of hearing performers behind performers, and the left and right performers and the center performers are quite precisely located, such that you get a feeling that they’re really there, like they’re standing in your room. That’s way more believable with a jazz quartet than it would be with a 100-piece symphony orchestra, which just can’t physically fit into your room. But a jazz quartet almost could fit into your room, and with the 521.4  it’s strikingly evocative of the real thing. I’m going to come back to that because that evocation of the real thing is very important to having your ear not overly concentrate on little frequency response errors in the recording or whatever it might be. You are, I think, less sensitive to that kind of thing with this level of soundstage management.

I’ll give you one more example of this very good stage width, good stage depth, and excellent placement of the players. I like to listen to the Mahler Symphony No. 1. The first movement has a really nice layering effect where more and more instruments are brought in. But if you know the layout of a symphony orchestra, when these instruments come in, you hear them pretty much where they should be. And the striking thing for me was that instruments that you know are farther back on the stage sound substantially farther back on the stage. The first violinist is right down next to the conductor, and the woodwinds are back there, and it sounds like that. Same thing with timpani. The timpani are back left in a typical symphony setup, and you hear them as being farther away and located on the left side. I mean, I can go on and on and on, but it’s quite exciting to hear this difference.

Now there is a “gotcha”. With the Linkwitz 521.4, you have to live with the fact that its accurate reproduction is going to accurately reproduce how the recording was done. Modern symphony recordings likely have the mics closer to the orchestra than you are when you go to a concert. And then we face the issue of how studio recordings are done with rock and jazz, and that’s another thing where you’re going to hear whether the recording was done with realism or something else in mind.  If the recording is not great, you’re going to hear that it’s just not a wonderful spatial recording, even though the playing might be phenomenal. At times, the Linkwitz 521.4 goes back to sounding like a normal speaker.  Which isn’t bad, but still…

Okay, so stage width and stage depth are, realistically, the best I have heard. But then I want to talk about a weird thing aspect of this: there are tracks where you can hear imaging far from the locations of the speakers. You can, for example, on a very few tracks, hear sounds from behind you. How can that be if Linkwitz’s theory is wrong? Meaning, Linkwitz says the recording encodes the location of performers relative to the microphones. And to present an image behind you, it kind of has to be a data stream going to your ear-brain combination that creates that effect because there is no speaker back there. I also could hear sounds in front of one of the speakers and to the side.

Now, I frankly don’t consider the ability to throw an image on the side walls or behind you to be particularly significant. Music is generally not played that way. So, it’s sort of a party trick, but I think it shows you what the speaker can give with the right data set. And these demos are a dramatic introduction to the basic message of “Oh, I’m listening to something different”. Then when you actually listen to it on great and well-recorded music, it presents the well-recorded music, in my view, properly, with width and depth that is appropriate to the kind of music and the recording.

Beyond Soundstaging

I want to get to the rest of the package because one of the problems with many of those speakers that I mentioned historically as being breakthroughs is they usually were great at something, and then the rest of the speaker had some flaws that made it a little hard to live with.

First of all, I really like the bass of the Linkwitz speakers. The exceptional thing I noticed was what I’m going to call bass color density. It’s just a rich, tuneful, not a sludgy or turgid or one-note, resonant kind of sound. It sounds like “instruments actually playing” more than a lot of speakers do. I think the dipole arrangement may be a little bit less affected by room resonances, so that could (and should) be a factor here. Another way to say this is bass detail is very good. It’s not the best I’ve ever heard, but it’s very, very good, and they go quite low. This is probably not the speaker for total organ music fanatics who, want to play the Widor 6th Symphony, recorded on an organ that has 16 Hz pipes, but the Linkwtz can go low-ish, and they have with some real power for much of what people actually listen to.

The next thing I really liked was the octave-to-octave balance, top to bottom. It felt just very nicely balanced. Recording after recording after recording the Linkwitz sets up relatively few of the distractions such as “Oh, it sounds kind of bright,” or, “Oh, it’s a little bit thin,” or, “Oh, there seems to be a midrange suckout,” or, “There’s this, there’s that”. The 521.4 is a really balanced speaker in terms of the frequency response. Now, that’s the, you know, sort of broad scale view. I do think there’s something in the upper midrange that’s a little bit strong. I wouldn’t say rough or peaky because it’s a very smooth-sounding speaker, but there may be a little elevation somewhere in the upper midrange. I didn’t particularly find it annoying, but it sounds a little bit not quite right in terms of that frequency balance. That also could be something that could be addressed, if I had a month to play with dialing in the exact positioning and ear height.

Another thing I really liked was the 521.4 is very dynamic. A lot of the great speakers that excel in terms of transparency aren’t that punchy. Then you get the punchy speakers that maybe aren’t great in terms of octave-to-octave balance. The Linkwitz speakers are balanced and really dynamic, especially on drum kit because you just get some power on snares and toms that it feels quite real. From other listening I’ve done, I think this could be a function of well executed dipole bass.

The 521.4s are, however, not the state-of-the-art in terms of the microdetail element of transparency. Some of what you hear when you listen to the really high-end speakers, I’m thinking of the great Magicos and the great Wilsons, is superb microdetail, which is how they produce a sense of air around the instruments. They do just seem to go down into the noise floor level of detail. And I didn’t quite get that feeling with the Linkwitz. I haven’t heard other $17,000 dynamic speakers that do this bit either, so maybe it’s a function of super advanced driver technology or amp combinations.

And finally, in terms of amplification, those of you who know how amps work will instantly know these are class D amplifiers. You can’t build a small box with five powerful amplifier channels in it and have it be really any other topology. But, the Linkwitz amps don’t have the class D hash. Not every class D amplifier has it, but some of them do, and people get worried about class D. But I wasn’t troubled at all by it in this case. Treble tonality sounds very nice here. They almost sound like MOSFET amps, if you know what that means. There’s just a smoothness to the high-frequency sound that I found quite enjoyable. So, the obvious downside of class D just doesn’t seem to be here. And because of the class D amps, for this kind of price point, we’ve got, I think, a lot of power on hand which may be necessary with the EQ required by a dipole.  You can buy the speaker, by the way, without the crossovers and without the amplification. But that, with a speaker like this, puts you into the engineering domain that seems a bit risky, but maybe fun for a few.

Why Now?

Besides the fact that Linkwitz (the man) was a brilliant engineer (co-inventor of the Linkwitz-Reilly crossover topology for example), and came up with an advanced theory of stereo, one wants to ask “why did it take until now to make this happen?”. One thing I want to point out is that the 521.4 probably couldn’t exist without DSP and class D amp modules. In 1980, if you had Linkwitz’s ideas, you might have been defeated in execution because you need heavy EQ to correct for the dipole effects and you need lots of power for each of the speakers. With traditional circuits, this would be very expensive. In addition, you would have needed to find drivers with the excursion capability to handle the EQ. I’m not saying this would have been impossible in 1980, just that it became easier as a commercial proposition with DSP and Class D.

With the Linkwitz 521.4, we have a speaker that can do imaging that’s unlike anything else I’ve ever heard, together with most of the other sound quality parameters we want and almost no drawbacks at a very reasonable price. As you can tell, I’m impressed. I think you should go hear these if you’re shopping in this price range, and really you should hear these if you’re shopping above this price range.  I believe the Linkwitz 521.4 can be considered a breakthrough in the sort of historical terms of breakthrough that I opened with: a speaker that does something that you really haven’t heard other speakers do, while having that special thing be musically valuable, not just a party trick.

Specifications

Linkwitz LX521.4 Loudspeaker

49” tall

16” wide

15” deep

101 lb.

2 x 10” woofers

8” lower midrange

4” upper midrange

2 x 1” tweeters (front/rear)

5 channels of amplification per speaker

Tweeters: 100 watts

Upper Midrange: 125 watts

Lower Midrange: 125 watts

Woofers: 250 watts per driver

Crossovers: 120 Hz, 1000 Hz, 7000 Hz

Max SPL: 109 db

 

System with amplifiers, crossovers and EQ: $24,000 (USA)

Tags: FLOORSTANDING LOUDSPEAKER VIDEO

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