Kef IQ Series Speakers and HTBSE-W Wireless Subwoofer


KEF is the venerable British-based loudspeaker company founded in 1961 by former BBC electrical engineer Raymond Cooke. The company first became famous for its monitors and Reference series speakers. In 1988, KEF introduced the revolutionary Uni-Q system, which mounted a neodymium-based tweeter in the center of the woofer voice coil. Since then, KEF has expanded its product line to include the ultra high-end Muon down to the entry level C Series speakers. The subject of this review, KEF’s Q Series speakers, is the next step up from the C Series. As the name implies, it offers the Uni-Q technology in each of the five main speakers.

KEF also provided its new HTB2SE-W wireless subwoofer, which won the design and engineering showcase honors at last month’s CES. The HTB2SE-W is a radical departure from the standard rectangular box design, and as Secrets’ resident bass-head, I was excited to check it out.


  • iQ 90 Main Front Speakers
  • Design: Three-way, Ported
  • Drivers: One 0.75″ Aluminum Dome Tweeter, Two 6.5″ Woofers Units: 2 x 165mm (6.5in.) LF, 165mm (6.5in.) Uni-Q, 19mm (0.75in.) aluminum dome HF Crossover Frequencies: 180Hz, 2.5kHz
  • MFR: 33 Hz – 40 kHz
  • Sensitivity: (2.83V/1m)
  • Crossover Frequencies: 180 Hz, 2.5 kHz
  • Nominal Impedance: 8 Ohms
  • Dimensions: 37″ H x 8.7″ W x 12.9″ D
  • Weight: 36 Pounds/each
  • Finishes: Black Ash, Dark Apple, American Walnut
  • MSRP: $750/each USA
  • iQ60c Center Channel Speaker
  • Design: Three-way, Ported
  • Drivers: One 0.75″ Aluminum Dome Tweeter, One 5.25″ Midrange, Two 5.25″ Woofersencies: 280Hz, 2.8kHz
  • MFR: 65 Hz – 40 kHz
  • Sensitivity (2.83V/1m): 90dB
  • Crossover Frequencies: 280 Hz, 2.8 kHz
  • Nominal Impedance: 8 Ohms
  • Dimensions: 6.5″ H x 20.1″ W x 10″ D
  • Weight: 19.4 Pounds
  • Finishes: Black Ash, Dark Apple, American Walnut
  • MSRP: $550 USA
  • iQ30 Rear Surrounds
  • Design: Two-way, Ported
  • Drivers: One 0.75″ Aluminum Dome Tweeter, One 6.5″ Woofer
  • MFR: 45 Hz – 40 kHz
  • Sensitivity: (2.83V/1m) 89 dB
  • Crossover Frequency: 2.5 kHz
  • Impedance: 8 Ohms
  • Dimensions: 14.4″ H x 8.7″ W x 12.9″ D
  • Weight: 14.2 Pounds
  • Finishes: Black Ash, Dark Apple, American Walnut
  • MSRP: $600/pair USA
  • HTB2SE-W Subwoofer
  • Design: Passive Radiator
  • Drivers: One 10″ Active, One 10″ Passive Radiator
  • Amplifier: 250 Watts RMS Class D
  • MFR: 30 Hz – 150 Hz
  • Dimensions: 15.4″ H x 17.3″ W x 7.7″ D
  • Weight: 26.2 Pounds
  • Wireless Transmitter: Frequency Band: 2.4-2.4835 GHz (ISM Band
  • Transmitter Module Dimensions: 5.8″ H x 3.1″ W x 3.1″ D
  • MSRP: $1,200 USA


Let’s talk subs, shall we? One look tells you that the HTB2SE-W is not your father’s subwoofer. The HTB2SE-W has a ten-inch driver set opposite a matching passive radiator. The driver and passive radiator are housed in an open flying saucer-shaped shell. The sub can be mounted on its side, with the driver in a down-firing position, or attached to a supplied stand in a side-firing configuration. If you use the side-firing configuration (as I did), the control panel is located somewhat inconveniently at the bottom of the unit.

The panel has a power button (which is “standby” rather than always-on), detachable power cord and a single line-level input. There are also three switches: One switch flips phase from zero to 180 degrees; a second contains a three-stage “bass boost” that provides an EQ boost at 40Hz (I left it off), and a third switch to run the sub wired or wireless (hence the “W” designation).

Wireless subs are becoming more popular, as they allow for flexible placement without worrying about running a line-level cable between the sub and the receiver (or processor). KEF’s wireless transmitter operates at the ISM-band spectrum (2.4-2.4835GHz). Like other wireless sub solutions, KEF’s transmitter connects from the subwoofer-out jack of the receiver/processor to the base unit via RCA cable, powered by its own wall wart. Setting the sub to operate on wireless is a simple process: Set the switch on the sub to “wireless,” plug in the base unit, connect the RCA cable to the receiver, then turn the base unit so that faces the subwoofer and displays a solid blue light.

Regular readers know that subwoofer output is the primarily dictated by three factors: Amplifier power, speaker size/excursion, and cabinet volume. Judging by those criteria, one would think that KEF had modest expectations for the HTB2SE-W. The KEF sub has a 250 watt Class D amp, which sounds like a lot of power, but the last two subs in my listening room had 1,000 and 3,000 watts RMS, respectively. Moreover, the KEF’s ten-inch driver and matching passive radiator are housed in a smallish housing that has minimal internal cabinet volume (15 liters). Nonetheless, KEF’s specifications state that the HTB2SE-W has a frequency range down to 30Hz, and maximum SPL of 110 dB. Really? Spoiler Alert!: Towards the end of this review is a graph from my bench tests, showing the KEF’s maximum output is over 112dB at 31.5 Hz. They weren’t kidding, were they?


But enough about subs. The iQ Series consists of three different floor-standers, the iQ 50, 70 and iQ 90. The iQ 90 reviewed here is a three-way bass reflex design, with the Uni-Q .75″ aluminum dome tweeter located in the center of a 6.5″ mid-range driver, below which are two 6.5″ low frequency drivers rated down to 33 Hz. There are two front-loaded ports, both of which can be plugged with foam bungs. The bookshelf-sized iQ 30 speakers, used here as surround speakers, contain the Uni-Q driver and a single port.

The curved wedge-shaped iQ 60C center channel speaker is a three-way vented design, containing a slightly smaller (5.25″) Uni-Q driver, flanked by two 5.25″ low frequency drivers. The iQ 60 has a single, small rear-firing port. All the speakers in the iQ Series have a teardrop shape, which is both visually appealing and helps reduce internal standing waves within the cabinet. Moreover, the iQ Series speakers contain two sets of heavy-duty binding posts for bi-wiring, and have removable grilles. Overall, the iQ Series look like much more expensive speakers than the $2,650 combined list price for five speakers.

In Use

My first experience with KEF speakers was about 20 years, listening to an early version of the Uni-Q system. The two things I remembered about those earlier KEF’s were the clear trebles and the wide sweet spot they produced. It’s funny how certain attributes get hard-wired into a company’s DNA, because my first impression of the new iQ Series were the clear upper end and good off-axis response from the Uni-Q drivers.

Dave Matthews and Tim Reynolds: Live at Radio City Music Hall (Blu-ray) is considered a reference audio recording. The Dolby TrueHD mix of Crash Into Me, with nothing but twin acoustic guitars and Dave Matthew’s vocal, is a great piece that emphasizes a speakers’ midrange and treble response, and was right in the KEF’s wheelhouse. Guitar picks strumming and breaths into the microphone were all there, right out front. The flip-side was that lower quality recordings, especially highly compressed modern music, came across as somewhat bright and fatiguing on the iQ 90’s. I generally dislike the phrase “unforgiving” when describing a speaker’s upper-end response because it’s an inherently subjective description, but it seemed appropriate in this case.

The iQ 60C center channel speaker did a fine job with the South African-accented English in District 9. District 9 is part sci-fi, part social allegory, and part action-adventure, so it also gave the iQ 30 surrounds and HTB2SE-W a good workout. The iQ 30’s, being monopole speakers, did a surprisingly good job of conveying ambience without calling attention to their location. Likewise, the HTB2SE-W created a good low-end jolt when the scene called for it, but never seemed boomy or overbearing.

On The Bench


All measurements were taken in the middle of the listening room, to avoid interaction with corners or walls. Except as noted below, measurements were taken from 1 foot at a height equal to the center of the driver.

Even though KEF listed the usable frequency response of the HTB2SE-W at 30 Hz, I measured only 3.65% distortion with a 20 Hz sine wave at 100 dB.

At 31.5 Hz (third-octave), maximum output was over 112 decibels!

THD+N vs. frequency. Distortion is below 4% from 20Hz through the entire frequency range, other than a spike from around 60 to 68 Hz.

Frequency response at 1 foot (white), 1 meter (red) and two meters (blue).

The iQ 90, at 50 Hz, produces an amazingly low 0.14% THD+N.

At 1hHz, distortion is 0.486%.

And at 10kHz, 0.483% THD+N.

White noise at one foot, one meter, and two meters (in-room response)



The Q Series speakers continue KEF’s rich heritage of clean sound combined with an attractive appearance. The HTB2SE-W subwoofer is all that plus has the added flexibility of wireless set-up. As is always the case with speakers, you should listen before you purchase. But if the $3,850 MSRP is within your price range, you’ll want to include the KEF’s in your audition list.