Monday, November 10, 2008

KEF C-75 review

Introduction: From my review of the PSB Stratus Bronze:
After the creation of my single ended EL156 amplifiers, I needed to buy a pair of speakers that would work well with a minimal of wattage. Sure I own a pair of UREI 813A loudspeakers that would do the job, but the 813As are massive and fragile with their exposed drivers. They were meant to be mounted high in a mixing room, not to be used in a residential situation with cats, children and klutzy owners like myself.

So I searched around and found a pair of KEF C-75s on Ebay. The KEF C-75 appeared to have everything I needed - high efficiency, a time aligned (or near enough) coaxial drive unit (Uni-Q) and a low profile. I put in a bid and won them from a seller with a 100% feedback rating. Well the speaker gods have never looked kindly down on me - when I received the speakers and plugged them in I found that one of the Uni-Q drivers was already blown with a fried voice coil. This C series of yore was never exactly a popular speaker, so finding a replacement was going to be hard to do. So with great disappointment the C-75s went under the stairs until I could find a driver
So there the C-75s sat as I searched through Ebay and Audiogon looking for a suitable Uni-Q driver replacement. A few weeks later, I finally found a pair of C-35s that appear to be a mini-monitor version of the C-75 - only using just a single Uni-Q driver in a smaller box. Information on these early versions of the Uni-Q is sketchy at best so I had to go on looks alone. I won the auction and waited impatiently for the C-35s to arrive.

Well nothing ever seems to go as planned - though the C-35 driver has exactly the same 8" diameter as the C-75 driver, upon closer inspection the C-35 has a slightly smaller tweeter. Pulling out the driver, the C-35 version also has a smaller magnet. I'm not sure why KEF bothered to make two versions of the same driver, but I decided to go ahead and make the swap. I had to desolder the tweeter connections to the crossover boards and swap everything on over to the new drivers. Let the Franken-C75 awake! With some trepidation I plugged everything in and decided to give 'em a listen.

System: RAKK DAC and/or Sony SCD-CD595 SACD player, DIY 6N6P linestage and DIY EL156 monoblocks. Various Cardas and Canare cabling.

Review: I setup the KEF C-75s in the same location st the PSBs once sat. I did not bi-wire as the KEFs only have a single set of banana jacks. I wired them up with an old pair of Canare 4s11 speaker cables that I used back in the day with my Adire HE10.1s.

Initial impressions were very good with surprisingly deep bass, a very nice laid-back midrange and a treble that was non-fatiguing. Because the crossovers use electrolytic capacitors, I let the speakers play a bit more before trying to draw any conclusions. However, I was immediately struck in the differences between this and the PSB. The PSBs try to be neutral while the KEFs decided to err on the side of warmth.

Richard Hawley's "Darlin' Wait For Me" on Cole's Corner is a extremely well record track. The KEFs made a big wide soundstage that really seemed to fill the room. While the PSBs kept the sound behind the speakers, the KEFs seemed to be more forward and captivating. Treble was warm and well-rounded as the recording intended. The drum kit however seemed a touch smaller than the PSBs, but still had a great sense of depth - sounding as if it was ten feet behind Hawley's dark vocals.

Nickel Creek - s/t is well recorded and highlights some great post-modern bluegrass. The recording captures Chris Thile's mandolin's attack and percussive sounds just right. The violin (or viola) never sounded etched, highlighting the natural beauty these instruments can have if the recording engineer does their job right. The KEFs captured the recording rather well, not hiding any of the blemishes or multi-tracking done with some of the vocals.

Earth Wind & Fire - "That's the Way of the World" (Mobile Fidelity) started to show some weakness of the speakers. Imaging sounded a little strange at higher output levels and the speakers definitely began to strain as the volume went up. An 8" woofer in a small cabinet can only move so much air and the dynamics became constricted at even decent output levels. Bass on some tracks was a little sloppy and uncontrolled.

Conclusion: Imaging is very good with the speakers nearly 'disappearing' into the room. The sound never seems to emanate from them, but the KEFs just create a pleasant soundfield. Driver integration is excellent with the three drivers combining into one seemingly single-source. Treble is clean with a touch of a roll-off, but you can still hear the differences between recordings. The midrange errs on the side of warmth which is a good thing in these hotly recorded digital days. Listening fatigue is very low and this leads to extended music listening sessions.

Weaknesses? Bass is a little uncontrolled, leading to a fatter warm sound than neutral. The overall sound can get a little grainy if pushed too hard. So don't expect clean sound if you're cranking up AC/DC to ear-shattering levels. They are also not the ultimate in definition but they make up for it with sheer musicality.

I also ran through plenty of different music listening to these speakers and like anything else, they have their limitations. For the money on the used market they are a bargain - pure and simple. Efficient enough to use with lower wattage amplifiers, the 4-ohm impedance doesn't appear to be a hard load even for a tube amplifier to drive. In the future I will be trying the speakers out with some higher powered tube and solid-state amplification.

12/15/08 Update: Using a 250WPC Threshold S/500 (500WPC into 4 ohms!) definitely made a change for the better. Bass is deeper and soundstaging opened up even more. The speakers really shined and to my ears outclassed the PSBs on several levels. There was a real sense of the musicians being there and playing together. Recording after recording revealed how musical the KEFs are. Ultra low bass on some recordings could be a bit uncontrolled, but I'm not expecting perfection for this kind of price.