KEF LS60 Wireless loudspeaker

I became interested in hi-fi well before the stereo era, at a time when DIY was a significant part of the hobby. In store catalogs of the time, as much or more space was devoted to raw speaker drivers and enclosures than to complete speaker systems. Those of us who wanted or needed to save some money built our own speaker enclosures from kits or plans or from articles in magazines like Radio-Electronics, Audiocraft, and Audio.

In those early days, the popular choices were corner horns and bass reflex speakers, but everyone was welcome to put drivers into any box they would fit in. Then, in 1956, came Ed Villchur's patent (footnote 1) for acoustic-suspension loudspeaker systems, marketed under the brand name Acoustic Research, and then, in 1961, the groundbreaking study by A. N. Thiele, "Loudspeakers in Vented Boxes" (footnote 2), which defined a series of sealed-box and vented alignments that related low-frequency performance characteristics (frequency response, power handling, cone excursion, and so on) to enclosure design and electromechanical driver parameters.

In a well-known corollary, known as Hofmann's Iron Law, Josef Anton Hofmann (an audio engineer who worked at Acoustic Research—the H in KLH) posited that three parameters cannot all be had at the same time: low bass, small (enclosure) size, and high sensitivity. You can have any two of these, but not all three. These seminal works underlie most mainstream loudspeaker design to this day.

Most, but not all. Neither Hofmann, Thiele, nor Villchur anticipated KEF's employment of active digital signal processing (DSP) to mate the driver, its enclosure, and the room. The KEF LS60 Wireless loudspeaker system ($6999.98/pair) is an end run around Hofmann's Iron Law.

Planned for KEF's 60th anniversary, much as the LS50 was planned for the company's 50th, the LS60 Wireless is a statement product that encompasses the premise of company founder Raymond Cooke that loudspeaker performance could be improved through the application of new materials and new technologies. Improvements in recent KEF designs include the refinement of the Uni-Q coaxial driver, Metamaterial Absorption Technology (MAT), force-canceling Uni-Core woofers with P-Flex surrounds, cabinets shaped to reduce diffraction, and the configuration and arrangement of drivers to create what KEF calls a Single Apparent Source.

All those features except Uni-Core and P-Flex were incorporated in the Blade Two Meta, whichStereophile's editors selected as the 2022 Loudspeaker of the Year. The LS60 goes a few steps further, adding built-in amplification and electronics for wired or wireless streaming and, as already noted, DSP. That's also true of the LS60's smaller wireless siblings, the LS50 Wireless and the LSX, the latter reviewed in 2019 by Herb Reichert. KEF's successful integration of these technologies in a trim, attractive, high-performance floorstanding loudspeaker makes the LS60 a landmark product.

KEF delivers
The team from KEF in New Jersey delivered and installed the LS60s, just as they did last year with the Blade Two Metas. Locating the speakers in the room progressed just as swiftly as before, but extra time was needed to link them to my local network so that I could control them and stream music to them. Ben Hagens, KEF's product training manager, got me up and running in a few minutes. All seemed well, and the guys picked up the shipping cartons and departed.

The LS60's matte-finished MDF cabinets are striking in appearance: Clean rectangular columns with radiused vertical edges, they are a petite 41" high, 5.1" wide, and 12.6" deep. Each cabinet has three internal compartments. The lower compartment holds the electronics; the port on the back above the connection panel is a hot-air exhaust and serves no acoustical purpose; a small opening at the bottom of the cabinet is the cool air intake. An upper compartment holds the transducers, within which the Uni-Q has its own subcompartment. The upper compartments are sealed. The cabinets sit on flat bases that, though only slightly larger, are heavier and provide stability. Even in striking Royal Blue with bright copper Uni-Q drivers, they blended well with our mixed traditional/contemporary decor.

The 4" Uni-Q driver is mounted to the 5"-wide front. The cabinet's curve begins at the edge of its Shadowed Flare surround, which also acts as a waveguide for the tweeter. The cabinet's curved edge minimizes diffraction. The Uni-Q is positioned a considerable distance from the top edge of the cabinet, so the impact of that transition on the radiated sound is minimal. The four low-frequency drivers are positioned in pairs on the cabinet's sides, symmetrically just above and below the Uni-Q driver. The members of each pair share a common magnetic structure, their individual voice-coils mounted coaxially. Electrically, they operate in phase, their cones facing the world in opposite directions. This force-canceling configuration, which KEF calls a Uni-Core LF, permits—indeed, requires—the LS60 to maintain a narrow profile, which is key to the speaker's operation as a Single Apparent Source.

While the above describes both speakers, the two speakers differ in that one, the "Primary" speaker, manages inputs and outputs and serves as the user interface. Starting at the bottom of this speaker's back panel are five rows of connectors, from top to bottom, reset, speaker pairing, and Bluetooth pairing buttons; HDMI, TosLink, and RCA S/PDIF connectors; analog inputs on RCA, USB service port, and a subwoofer connection; RJ45 jacks for wired internet and interspeaker linkage; and a connector for AC power. The Secondary speaker has five rows, too, but each row has just one item: a button for pairing to the primary speaker, a USB service port, a subwoofer connection, an RJ45 jack for pairing, and an IEC connector for AC power.

After connecting both speakers to power, basic setup consists of loading the KEF Connect app from the Apple Store or (for Android devices) Google Play to a smartphone or tablet, pairing the app and tablet to the Primary speaker via Bluetooth, and following the onscreen instructions to connect the LS60 to your LAN. Then you pair the Primary speaker with the Secondary speaker and access your choice of an impressive array of music sources.

As is obvious from its name, the LS60 Wireless is designed to stream via Wi-Fi, and that includes the interspeaker link. My apartment does have Wi-Fi, but coverage dwindles at the speaker end of my living room. Consequently, upon setting the system up wirelessly, I quickly found myself dealing with dropouts and disconnections. There were two possible cures: to wire the LS60s to my LAN with an Ethernet cable or add a Wi-Fi extender. I did both. I have since encountered no problems with the system with either the wireless or wired connections.


Footnote 1: US Patent 2,775,309.

Footnote 2: Thiele, A. Neville (1961). "Loudspeakers in Vented Boxes," Proceedings of the Institute of Radio Engineers, Australia, 22 (8), pp. 487–508.

COMMENTS
georgehifi's picture

Interesting Kef's on the ball and used Class-D amps everywhere but for the highs, where they used Class-A/B

I've always said in the past Class-D's Achilles heel is the highs because of the phase shift caused by the low order output filter to get rid of the class-d switching noise.
As you can see, Class-D output impedance rises in the highs because of the switching noise output filter.(blue trace)

And the worst thing is the phase shift increases right down into the upper mids because of that low order output filter for switching noise elimination (red trace)

https://ibb.co/vvhDLSn

Cheers George

Prof Speaker's picture

You don't really believe that the phase shift of only about 60° has an audible effect? There is not the slightest indication that phase shifts of such a small magnitude are audible. Also the lower damping factor has no meaning at higher frequencies (clearly above the resonance frequency of the transducer), because in this frequency range the mass character of the transducer dominates and the damping only has a meaning in the range of the resonance frequency. By the way, the damping in the high frequency range is primarily provided by the damping of the mechanical system and not by the electrical damping of the amplifier.

Glotz's picture

George rules.

georgehifi's picture

"You don't really believe that the phase shift of only about 60°has an audible effect?"

Maybe, when it starts down in the upper mids then all the way up. Why would Kef use "A/B" for the highs and "D" for the rest. And if there's complaints of Class-D it always centers around the HF performance.

Technics bought out the mega dollar SE-R1 with 4 x higher switching frequency and therefore 4 x higher output filter for it, which also raises that -phase shift way out of the audio band. It's said to have the best top end of any amp, even pure Class-A.

Cheers George

benleo's picture

Dear Kalman,
I have for the past few to several years closely followed the development of active/integrated streaming speakers. (For short "integrated active speakers".) I followed the D&D, Buchardt, KEF, Genelec, and others I am forgetting. I have three DACs and find each has its own sound signature. DAC selection is important to sound quality. Are there any integrated active speakers that allow for a DAC of your choice to be incorporated into the integrated active speaker? (The option to disable the integrated DAC and put your exterior DAC into the sound stream before amplified?) Wouldn't that be a fantastic add? How difficult and/or expensive would it be to add that feature? It would let you tailor the sound not just by DSP, but also be selecting the DAC used in the integrated active speaker. Your thoughts?

funambulistic's picture

... series of active speakers operate in the analog domain (i.e., no ADC).
https://www.elac.com/category/powered-speakers/navis-arb-51/
There may be other manufacturers, but this one comes first to mind.

Kal Rubinson's picture
Quote:

Are there any integrated active speakers that allow for a DAC of your choice to be incorporated into the integrated active speaker? (The option to disable the integrated DAC and put your exterior DAC into the sound stream before amplified?)

Not unless you build it yourself.

Quote:

Wouldn't that be a fantastic add?

Frankly, no. It defeats the integration of the DSP, amplification and DAC(s) in which the designer has invested so much effort.

Quote:

How difficult and/or expensive would it be to add that feature? It would let you tailor the sound not just by DSP, but also be selecting the DAC used in the integrated active speaker.

IMHO, the difficulty would greatly outweigh its value. The principle of such integrated products is that the choice and implementation of the DAC(s) (and everything else) is essential. If you want to tailor the sound, buy a different product or use DSP.

liquidsun's picture

You can still use the RCA inputs of the LS60 and do the Digital to Analog conversation in external DAC. Right?

Kal Rubinson's picture

That means a signal chain from external D/A to internal A/D to DSP to internal D/A. If that's OK with you, you can.

MichaelVictor's picture

"If you're in the market for speakers or even a complete system for just over $5000, the KEF LS60 demands your consideration."

With all due respect Is $7,000 just over $5,000?

sophie234's picture

In the review you state the sub setting of -9db. Is this the setting in the SVS app, or is it something in the LS60W app? I ask as I also use a pair of SB3000s, and I have their level set at between -20 and -28 depending on which speakers I'm using. Thanks.

Kal Rubinson's picture
Quote:

In the review you state the sub setting of -9db. Is this the setting in the SVS app, or is it something in the LS60W app?

That was a setting in the LS60W app and so it was relative to the output of the LS60Ws. The SVS attenuator was left where it was for other use. From memory, it was probably around -10 to -15dB.

sophie234's picture

thank you

georgehifi's picture

"You don't really believe that the phase shift of only about 60° has an audible effect?"

Yes, when it starts down in the upper mids then all the way up. Why would Kef use "A/B" for the highs and "D" for the rest.
If there's any consistent complaints of Class-D it always centers around the HF performance.

Technics bought out the mega dollar SE-R1 with 4 x higher switching frequency and therefore 4 x higher output filter for it, which also raises that -phase shift way out of the audio band. It's said to have the best top end of any amp, even pure Class-A.

Cheers George

Scintilla's picture

I recommend the LSX to my non-audiphile friends as a great one-stop system solution. I have the LS50Ws myself in my bedroom. Love them. But like you, Kal, I haven't been able to leave behind my Studio2s for anything else and I watch your reviews waiting for the one that captures your heart and wallet. I was immediately interested in this one when it was released. I am sure one will eventually come along, ut I still have a hard time imagining that I will find a system that sings like the Holo May with the Revels. I thought Revel was actually working on a DSP-based integrated speaker to replace the Ultima line? Do we have a confimration that they are still pursuing that or if it has ben dropped?

Kal Rubinson's picture
Quote:

But like you, Kal, I haven't been able to leave behind my Studio2s for anything else and I watch your reviews waiting for the one that captures your heart and wallet.

Actually, I have moved on from my Studio2s to KEF Blade Two Metas.

Quote:

I thought Revel was actually working on a DSP-based integrated speaker to replace the Ultima line?

I don't think we ever had any real evidence of that. When I visited Harman back in 2018, I raised the issue of an DSP-based integrated speaker with Kevin Voecks who was, at that time, Sr. Manager, Acoustic Technologies. He smiled and responded like a politician saying that it would be the logical direction. That is all I know.

avanti1960's picture

cabinet resonance control. That is off the charts phenomenal.

Benny Patana's picture

'My apartment does have Wi-Fi, but coverage dwindles at the speaker end of my living room. Consequently, upon setting the system up wirelessly, I quickly found myself dealing with dropouts and disconnections'

Ok, so KEF markets the LS60s as "wireless' speakers' but immediately Kal finds the speakers don't actually operate satisfactorily as wireless speakers in his living room, which has wireless coverage? How large is the living room?! I find this somewhat troubling to say the least ... surely this finding is something of an orange flag for those of us who might want to use the speakers as marketed? You need to be a little more rigorous in these reviews guys! Disclosure: I own the smaller LS50 wireless 2s and have been very disappointed in their wireless performance, which is glitchy to say the least.

Scintilla's picture

I own the LS50Ws. In my loft, they haven't worked well with wireless; like at all. But they also don't do 24/192 without a wired connection. So, is wireless limitations really a deal-breaker for this level of speaker? I wired my whole place up and don't use wireless for anything but phone. I think that 's a better way to manage your privacy too. But this is merely my opinion. Still, if you are seriously looking at a $7000 speaker and think wireless is the best way to connect them, then you should probably look elsewhere.

israndy's picture

You just have to have WiFi in the room you are gonna use them, like any other WiFi device. It's moving a LOTTA data so you can't have marginal reception like you could with a phone you are texting with.

I also use it from my Apple TV via the TV I often watch for any real highres stuff I wanna hear. Cannot believe how good these speakers are, and I got them for my 60th Birthday to really make them my favorite things ever. Ended up getting a clearance LG 77" C2 to complete the package, pure heaven.

Kal Rubinson's picture
Quote:

Ok, so KEF markets the LS60s as "wireless' speakers' but immediately Kal finds the speakers don't actually operate satisfactorily as wireless speakers in his living room, which has wireless coverage? How large is the living room?!

It's not the size of my living room but that the living room itself is 2 rooms away from the WiFi Router with intervening (steelframe and concrete) walls. In addition, the WiFi router is, probably, ~5 years old. So, the WiFi at that end of the room has always been useless as revealed by laptop/iPad/phone drop-outs there. In other words, it was a known problem.

Quote:

I find this somewhat troubling to say the least ... surely this finding is something of an orange flag for those of us who might want to use the speakers as marketed?

I did use them as marketed. After the described disappointment, I updated my WiFi setup and, then, the LS60s worked satisfactorily wired or WiFi.

james3895's picture

Mr. Rubinson, could you maybe elaborate on "satisfactorily" as used above? There are many who suffer from PTSD re: KEF wireless LS50s not working correctly on WIFI and would be plenty curious if satisfactorily meant zero drop outs, a drop out a day, etc. Any further color would be appreciated.

Kal Rubinson's picture

After I updated the WiFi in my home, as described above, I had no problems with drop-outs with it at all.

I will offer a caveat, however, in that I did use wired LAN for most of my listening out of habit.

LenM's picture

Kal: How would you use the LS60 in an immersive playback system?

Could you use six or eight of them in a ring?

What wireless speakers would you use above and below the azimuth ring?

Kal Rubinson's picture

I was just riffing.

You could use 5 or 7 of them at floor level if you had a way of providing them all with synch-ed digital signals using, say, a prepro with multiple digital outputs. Subs should not be a problem if you ran them off the LS60s.

I have no idea about what to use for top/above. LS50s?

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