KEF 101 restoration, plus comparison to Wharfedale Diamond 3 and Pioneer SP-B522-LR

[leesonic]

I actually had the pleasure of working on a pair of KEF Reference 101 speakers over the last few weeks. Usually, I only get sent the crossovers, but the owner of these @TAS1970 sent me the complete speakers. I was able to finally see and hear a pair of these in action, and even compare them to some of their contemporaries. But more of that later...

In the past, when people have asked me how to remove the crossovers, I just say "take out the center nut, and cut the sticky pads in the corners". Well, actually working on a pair, this is more difficult than it looks. First of, that center nut, you have to remove the nut, you can't remove the screw from the bottom. The reason being, it has a machine thread most of it's length, but a reverse thread that bites into the wood towards the head of the screw. The reason for this is so that the screw will not turn as you tighten the nut inside, a rather ingenious solution. This screw has a Posidriv head, as do most screws on vintage KEF speakers, so you would be advised to get a correct Posidriv bit, these are identified as PZ1, PZ2 etc.



Once the center nut is removed from the crossover, then you must break the sticky pads loose. I found the easiest way to do this was with one of those orange handled pry tools. Mine aren't a fancy brand, I can't even remember where I got them from, probably the Dollar Store. But the 90 degree one, if you drag it under the pads a few times, you should be able to lift the crossover board up and out. Don't force it, and if it feels like the board is bending, drag the pry tool under the pads some more.

Here are the crossovers removed from the speakers. On the second picture, you can see how the caps for the protection circuit have leaked, and corroded through the PCB tracks. I started removing the caps from the top board before I remembered to take pictures.





As you can see, the 400uF cap for the woofer circuit is made up of a 300uF and 100uF cap in parallel. Earlier boards have four 100uF caps, plus a different layout. Make sure you check what board you have before ordering caps, like I didn't. The picture below shows the 4 x 100uF cap board.

Here is a closeup of the damaged area on one of the boards. Notice how I have completly removed the corroded tracks using nothing more than a wire brush and a small flat screwdriver. You must scrape all of the corroded track away, there no point leaving any of it there, as it will just spread again and get worse. Clean the board with acetone once you are done scraping and brushing.



Fitting the new caps is always a squeeze, kind of like trying to get a quart in a pint pot. But they should go on, using hot melt glue to glue them to other components for rigidity helps, but avoid gluing to any of the resistors, as these might get hot. The big 15uF Dayton cap here has to be mounted with as little overhang as possible, otherwise the crossover won't pass back through the woofer hole and into the cabinet. Of course, if you use electrolytic caps throughout, this won't be a problem, film caps are bigger. Trial fitting the caps and seeing if they will fit will help.





Close ups of the repaired areas show just how much work is needed to fix these PCB tracks.





Squeezing the crossovers back in through the woofer hole can be difficult with the new caps installed. I upgraded the wiring to the terminal plate and to the woofer with some thicker wire. The tweeter wires are soldered right up to the voice coil, so I didn't mess with these.

Add some 3D printed terminal plates holding some new binding posts, and the job is complete. Note the PZ1 screws for the terminal plates.

Lee.

 

[leesonic]

Comparison to other small speakers

The KEF Reference 101 speakers were produced from 1979 to 1986 approximately. They use a B110 5-1/4" woofer and a T27 3/4" tweeter. The cabinet measures 13-5/8" high x 7-1/16" wide x 7-1/16" deep, and weighs in at 12lb 2oz without grills, 12lb 7oz with grills. They are a closed box design, with an impedance of 8 ohms.





The Wharfedale Diamond was introduced in 1982, and the Diamond name lives on today. The Diamond, Diamond II and Diamond III model pictured here were all very similar. The III features a 4" woofer and a 3/4" tweeter. The cabinet measures 9-3/8" high x 7-1/4" wide x 7-1/2" deep, and weigh 6lb 9oz without grills, 61b 12oz with. They are a vented design with a rear facing port, impedance 8 ohms.







The Pioneer SP-B522-LR was introduced in 1992. It is listed as using a 4" woofer, but this barely measures 3-3/4 across the outside of it's surround, and a 1" tweeter with a large faceplate with an almost waveguide effect. The cabinets have curved sides, measuring 12-1/2" high x 6-3/4" wide (measured across the baffle) x 8" deep. At the widest point on the curved sides, they measure 7" wide. They weigh 8lb 6oz without grills, 8lb 9oz will. They have a rear facing port, and the impedance this time is lower at 6 ohms.







Brief listening impressions

Listening to the KEFs first, they have a very clear treble and midrange, especially on female vocals. Bass is lacking as it is on larger speakers, but it still goes low. On a track like Jill Scott's "Getting in the way", the lowest of the bass notes can still be heard. This is one of the characteristics of a closed box design, while the low frequency response rolls off sooner, it does so more gradually. Bass guitar notes, you can hear the buzz of the string, whereas on speakers with more bass, this might get hidden.

Switching over to the Pioneers, they are louder with more apparent bass, certainly more impressive upon first hearing. This could be because they are 6 ohm and not 8 ohm. But the real deep bass note in the track mentioned above is pretty much non-existent on these. Almost if the enclosure was tuned to provide impressive upper bass frequencies at the expense of the real low ones. Vocals seem less "breathy" and recessed compared to the KEFs. Turning up the volume, bass drums quickly became a thud as the driver bottoms out. The KEFs, I got the impression could handle more power, but I didn't want to push them as they aren't my speakers.

Changing to the Wharfedale Diamonds, some of the up front bass of the Pioneers is lost, but they do sound bassier than the KEFs. The low bass note mentioned before is there, not totally lost like the Pioneers, but not as surprising as the KEFs. Treble is less sparkly compared to the KEFs, but doesn't seem as recessed as the Pioneers. Midrange is detailed, and as with the KEFs, I could find myself hearing little nuances in music that I had never heard before, despite being songs I've known for years. I would probably say these had the most natural balance of the three.

Like I said, brief listening impressions. All of these would be great for a small apartment, where keeping peace with your neighbors is paramount. The apparent lack of deep bass is made up for the details you can hear in the bass. I would rank them in order of how I presented them here : KEFs > Wharfedales > Pioneers.

Both the Wharfedales and the KEFs could be had with these same drivers plus some additions which might be worth further investigation. Wharfedale had the Double Diamond which featured two of these drivers in larger cabinet. There was also the similar TSR102.2 speakers. The KEF B110/T27 combo has been used with the B139 woofer in the KEF Concerto, the Constructor Series CS7, and some transmission line IMF speakers like the TLS-80. But there was also an active speaker called the Merdian M2 which used two B110s and a T52 tweeter in a much larger cabinet. That would be a cool speaker to find!

Lee.

 

[TAS1970]

Thanks for the assist. And nice to see clear pictures of the boards -- it's remarkable how much magic goes into making good sound come out of little boxes.

Also, thanks for the comparative reviews. I'm really looking forward to hearing these again (it's been a few years) and it's nice to have my memory validated. They'll be sitting in a pretty small listening space (about 11x13) so I don't think I'm too worried about being able to push them super hard. Not quite apartment living, but close. Come to think of it, Dad likely bought these while living in Manhattan, so the apartment calculus was probably a factor. When he moved out to the burbs, he ended up with a pair of Mangepans, which is why these ended up in a closet for a few years...

 

[homebrew]

Good way to work on your speakers while drinking a bottle of Dom Perignon. Sante'

 

[dualhead]

Thanks for the info and review!

 

[TAS1970]

I just got these set up and I want to compliment Leesonic for the excellent refurb work and to KEF designer Ray Cooke for the excellent sound. These are beautiful. Very precise, they pull out details from Weather Report "Night Passage" that I was just not hearing at all with my Boston Acoustic A70s.

 

[Bassman79]

Thanks for your review.
If one like a highly detailed and open midrang than the Kef's are amazing. Ive yet to hear a small size speaker that has such a balance and 'oempf' as the 101's.

 

[Sniffers]

Hi. I have picked up a pair of Kef 101, late models with the banana plugs. I have bought a set of caps from Falcon and finally got around to starting the project. My question for leesonic and others is does the crossover have to come out through the woofer cut out. I read the Kef 101 service manual and it said that the bottom comes off with the crossover. The bottom of mine is not moving and I will have to pry the 2 sided tape from the cabinet to get the crossover out. Thanks to leesonic for his instructions on removing the nut on the board to be able to remove the pozidriv bottom screw, threaded counterclockwise. My boards are the 110005A version and the serial numbers are in the 12xxx. Thanks for any help you might give.

 

[leesonic]

Hi. I have picked up a pair of Kef 101, late models with the banana plugs. I have bought a set of caps from Falcon and finally got around to starting the project. My question for leesonic and others is does the crossover have to come out through the woofer cut out.

Yes. Use some pry tools and drags them under the sticky pads in the corners of the board, loosening their grip.

 

[Sniffers]

Thank you leesonic. Got it out. C5 has leaked. Looks like c4 leaked at some point too. Solder bridges installed. Glad i pulled it. A couple of traces danaged by acid.

David

 

[Sniffers]

Finally finished recap. Fixed wiring error of previous repair. A resistor had drifted. Fired them up and right away could tell there was a huge improvement. Thank you leesonic. The cap set from Falcon did the trick.

 

[scottdavis08]

I scored some of the Kef reference 101off of ebay, because the guy had a corroded crossover that kept cutting out. I sprayed it with deoxit and so far everything has worked out. These are some of the finest speakers I've ever listened to. I own a couple of much more expensive brands, but feel these are better, and with the right amount of amp/power are simply exquisite/beautiful in their Ls3/5a way. I believe these are 81/82 db., and need some power to sound their best.

 

[leesonic]

I scored some of the Kef reference 101off of ebay, because the guy had a corroded crossover that kept cutting out. I sprayed it with deoxit and so far everything has worked out. These are some of the finest speakers I've ever listened to. I own a couple of much more expensive brands, but feel these are better, and with the right amount of amp/power are simply exquisite/beautiful in their Ls3/5a way. I believe these are 81/82 db., and need some power to sound their best.

Keep an eye on that crossover, or an ear. They don't get better with age, and sooner or later, it might start cutting out. I can fix those if you need me to, and there are several options available for caps.