B&W Vs KEF - And the Winner Is?

I wish it were that simple. I'll tell you this much, when pitting the B&W CDM 9NT against the KEF 105.2, I was forced to make a tough decision and admit some uncomfortable truths. First of all, if anyone of you has been following the KEF 105.2 sale on Audiogon, you may have noticed that I've raised the price to $1,500 for the pair. I've also pulled them from CraigsList. Why? Good question. It all came down to some critical listening tests I've done over the past few days.

The fist speaker comparison I performed was between the B&W CDM 9NT and my KEF Reference Two speakers that have been my, well, 'reference' for mid-priced quality loudspeakers for over two years. The result here was that, in almost every way, the B&W beat the KEF Reference Twos. Bass extension, midrange and treble clarity... the list goes on. Not that there was a "night and day" difference. That's why the comparison needed over a month to complete. Had this been a slam dunk, you would have been reading about it in early August. The result? I sold one of my pairs of KEF Reference Twos last night. Still have another pair, in rosewood, that's in my office. I'm keeping these for the time-being, but if you REALLY must have a pair in excellent condition - shoot me a line.

Now, on to the KEF 105.2 story. Posting these great speakers for sale was not an easy choice, but I simply needed the room. The addition of the B&W 801 S2 pair and the CDM 9NT was creating a clutter condition more akin to hording than collecting. After the KEF Reference Two had gone up against the CDM 9NT, I felt it only fair to give the 105.2 one last chance at saving itself. Turns out that the CDM 9NT got a run for its money.

The KEF 105.2 proved equal in the bass - both extension and overall "punch," and much more natural and more mellow in the mids and highs than the B&Ws. Where the Reference Two was lacking clarity in these two critical tonal areas, the 105.2 held onto clarity and brought a true-to-instrument naturalness that I had forgotten they possess. I'm so glad I took the time to listen carefully to these speakers again. After only an hour or so, I pulled the CL sales advert and adjusted the price up to "extreme gear enthusiast" level on Audiogon. If someone wants these for $1,500 - we'll talk, but it's gonna take that kinda scratch for me to consider letting them go.

How did the CDM 9NT compare to the 105.2? Pretty darn well, actually. The one characteristic that takes getting used to on the CDM 9NT is the forwardness (read: brightness) of the midrange. That 6.5" surround-less midrange driver packs a serious punch, and throws vocals right through your eardrums. This is fine for most purposes, and I suppose desirable for movie soundtracks where vocals often are lost, but for casual listening? Notsomuch.

I tested several vocal tracks, but kept coming back to Sade's Diamond Life album. "Your Love is King" sounded cool and natural on the KEF 105.2, but Sade's voice plowed right through me on the CDM 9NT. It actually was quite grating. Switching back to the 105.2, I realized that these KEF speakers offered the kind of "all-day-listening" that most people seek in quality loudspeakers. Listener fatigue can be caused by many things - muddy or sloppy bass is one I've experienced recently, but brightness in the mids and highs is another. Everyone is different though. Upon hearing the same Sade song on the B&W, a friend noted that the detail was amazing. His take was that the KEF's, although plenty good, sounded muted in comparison.

As I've noted before, when it comes to comparing speakers, it all comes down to personal taste. Specs mean nothing once you get past the Best Buy listening room speaker stock and on to more vintage or higher-end, specialty speakers. Whenever possible, take time to listen and compare speakers prior to making a purchasing decision. This is rarely an option, and I've bought plenty of speakers with only hearing a selected track or two, so I'm asking you to do as I say, not as I always do.

You can get speaker recommendations from a friend, an online blog (hello!), or someone who claims to have a golden ear, but the only ears that you have to satisfy are your own. If nothing else, remember this from this post: If a vocal or musical passage seems grating to your ears or even slightly unpleasant, regardless of how the speakers shine in other areas - beware! Remember that these speakers may, eventually, end up in a primary listening space, and all-day listening comfort will become a concern.

So now what? As soon as I hit "publish," I'm going back up to the loft to move the KEF 105.2 back into position and pump some tunes through them, enjoying every single natural, sweet note.

KEF 105.2 - Bass Unit (woofer) Replacement - The Full Story

UPDATE: You can purchase the recommended replacement woofer for the B300b discussed below HERE.

HiFiCollector Community member, Tony sent me some detailed, very well-written information on how he is replacing his KEF 105.2 bass units. I know this info will be very helpful to all of us who own these fine speakers. Enjoy!

The KEF 105.2 Bass Unit Replacement.

My Kef 105.2's suffered a damaged bass unit, which was also showing signs of a buzzing in the bass, which happens when the support of the heavy Bextrene cone sags over time, and is a known problem. Also the concave shape of the outer rubber ring was flattening and stretching. These 12" B300b KEF-built units are rare, but occasionally turn up on ebay, where they are either overpriced, or are in poor condition, judging by the accompanying pictures.

After a web search, I found Audio Components here in the UK, and asked if a repair was possible. They promptly replied, and confirmed the source of the problem;

"What you describe – the flattening of the rubber surround is caused  by the collapse of the inner suspension (the spider) which supports the voice-coil end of the cone. Once this weakens it sinks into the frame and pulls the cone downwards, stretching (flattening) the rubber surround – this makes the driver unusable. Even if you find secondhand replacements on eBay, it will only be a matter of time before these go the same way.These drivers can be re-coned but the cost of doing thisproperly (and with the correct cone and voice-coil assembly) can be as costly as replacing the driver – also the re-coned driver will behave differently to the driver in the other channel (which has an old cone and suspension). The most economic solution (and the one which will perform best) is to replace both the bass drivers with new drivers that match the original specification and closely as possible."

"The key parameters of the B300 are: Fs=23Hz; Qts = 0.46; BL = 12; Znom = 8; Sens = 90dB; EBP =50. It is important to find a driver that is a close match to these – the majority of 12 inch woofers manufactured today do not. The closest driver we have found is the Peerless SLS315: Fs 28Hz; Qts = 0.47; BL = 12.2; Znom = 8: Sens = 91dB; EBP = 60. That’s as close as makes little difference. Maybe some tuning of the damping material will be required. This unit has a different physical frame size and fixing arrangement so some cabinet work is required."

These units were £70 each, a very reasonable price. They also offered to fit the units for me, and to measure the speakers under anechoic conditions to achieve proper tuning. However, this would have cost another £300, which is approaching what the speakers are worth anyway, so I decided to do the work myself and tune by ear. I measured up the cabinets first, of course, and found that the new drivers would fit into the existing cut-outs. The extra cabinet work referred to simply means drilling some holes, as the new units have an eight-hole fixing arrangement, compared to the three-point fixing of the originals. The cones are coated paper, the coating appears to be rubber, latex or similar. It looks and feels lighter than the B300b cone, so I would anticipate no sagging problems with these units.

I have had the Peerless units on stand-by for a while until I can find the time to do a proper job of it. Simply putting one of the speaker cabinets on its back and sitting the new units in place shows that the new screw positions will be close to the edge of the circular cut-out of the cabinet, but with a little care the actual placement should be fine. This could be done with conventional wood screws, but something to consider is that KEF used a special screw fitting for their original units, in conjunction with a foam gasket at the back of the driver. As this was an integral part of the design, I don't want to just put the new units in and assume it will be ok. I think I'll try cavity-wall screws; the expanding wings would mean that the drive unit will be bolted through rather than having screws biting into the wooden cabinet.

I want to double-check everything, reinforce the cabinet around the cut-outs if necessary, and have a supply of  gaskets of various materials (soft foam, hard foam, rubber) on hand so I can fit the units and audition as I go to get the best results. The cavity wall screws will also enable me to remove and replace the units several times without damaging the cabinet, to change gaskets. I think the first step will be to simply fit them with any set of gaskets, connect to the amp, and run the units in before testing alternative materials.

Of course, an interesting project would be to build new cabinets, as the originals are not particularly sturdy by today's standards; a tap with the knuckles here and there shows several resonant spots. I gather that they were built to a particular price, otherwise the 105.2's would have been so expensive that KEF wouldn't have sold any. For now, I'll be content to get these wonderful speakers up and running again, and just sit back to enjoy the music.

So when refurbishing any speaker, you'll need the appropriate parameters to source replacement units. I freely admit to not knowing what all the above symbols or abbreviations mean, although free resonance (Fs) and nominal impedance (Zs) are familiar. I suspect Qts is the natural damping factor of the driver.

Replacing some units might be tricky - for example to replace the mid or treble units in the 105.2's, they each have to fit into a moulded rebate. Fortunately, I think these units will last a lifetime, but it's something to bear in mind if revitalising a cherished speaker.

If there's anyone else out there in the UK who needs any speaker repairs, here's the web address;

http://www.audio-components.co.uk/

I think there are similar suppliers in the USA who will doubtless be able to advise as well. I think Peerless are well-known across the pond.

I've attached a technical diagram and a picture, so you can see the more conventional appearance compared to the B300b.

So that's the KEF story so far - please feel free to edit the above if you think it necessary.

Of course, I now have one original B300b in good working order - so if one of your units shows signs of wear, then I have a spare!

Speakers - KEF 105.2

Next to my Vandersteen's, these are my favorite speakers. The KEF 105 Series 2 were way ahead of their time in regards to design. There is an inherent problem with these speakers, however, that should be mentioned. The woofer material is heavy and this, over years, causes the woofer to sag and for it to rub inside against the voice coil. This causes distortion and renders the speaker useless. BUT, as I found out from a forum post, there is a way to prolong the life of the speakers. Simply rotate the woofer each year. I've done this once already as the speaker, indeed, started to rub, and the pair is due again for another rotation. I have to wonder just how many rotations I'll get before the woofer material fatigues to the point of permanent sag. KEF doesn't support these any more and the only way I've found to get a replacement woofer is via eBay or private sellers.

How do they sound? Magnificent! These have fantastic dynamic range. The bass enclosre design provides tight, powerful bass, and the separate mid and tweeters are clean, crisp, non-fatigueing. These are wonderful speakers. You don't need a sub with these at all. The KEF 105.2 sound wonderful at low volume as well. That's how I usually play these as they are part of a "loft" system that I turn on during early weekend mornings. I have these paired with my McIntosh MC 2100 and an Adcom Pre-amp.

Update: HiFiCollector.com community member, Tony sent in this link to a KEF user forum - great info there - thanks Tony!

If you have any stories or photos of your KEF 105.2 speakers, please leave a comment or email me.

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KEF Audio's 105.2 official page.