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Old 13th February 2009, 08:29 AM   #1
tsnell is offline tsnell  Australia
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Default Please Help me Identify and Build 1980’s KEF Speaker Kit

Hi Everybody,

My best mate’s dad passed away a while ago. Recently we were cleaning out his old place and found a KEF speaker kit. The receipt is still in the box, purchased at the Stereo HiFi Centre in Melbourne for $400 in 1980 – it predates me by 4 years! Despite its age, everything is in absolutely immaculate condition. The crossover networks and drivers all appear absolutely perfect.

While I wouldn’t even feel qualified to call myself a novice in this field, I am the closest thing to an expert my mate knows, and I have been given the task of determining the fate of this kit. His Dad was always into HiFi, some other gear included a Yamaha A-700 amp, Wharfedale Laser 150 speakers, Yamaha HP-1 headphones… the list goes on. I would really love to complete this kit for him as a permanent, happy memory of his Dad. And I would really like to make it the best that it could be. I will be forever grateful for any help anyone can provide.

It looks like the speakers are kits to make KEF Concerto loudspeakers. But, there are some hand drawn cut sheets in the box, that my mate’s Dad had obviously intended to use and they look nothing like the concertos. I do not believe he planned to make them as per the kit design. There is an article from “HiFi News & Record Review” from May 174 entitled “A Folded Column Loudspeaker”. It seems to use the same drivers as the concerto and the cut sheet seems to match this design more closely.

So my questions are:
1. Has anybody ever seen these speakers/kits before, either the concerto or the folded horn?
2. Are they any good?
3. Should I build the concerto, or the folded column design?
4. Everything looks great, but is the age of everything likely to cause huge problems? I.e. are the caps in the crossover likely to fail and should I substitute them?

Everyone on here has been so helpful in the past and I thank you all in advance for any help you can provide me.

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Old 13th February 2009, 01:35 PM   #2
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Hi There;

Sorry about your Dad's friend. You have really found something though. The KEF B139 is a classic transmission line loudspeaker. Used drivers are being sold today for a pretty sum. The rubber surround likely has survived without rotting out.

Do the speaker plans look like this?

http://www.t-linespeakers.org/projects/jakob/index.html

If it were me I'd build the transmission line (folded column) as I am a fan of those types of speaker. Of course it depends on how much room you have in your house for speakers and certainly on your woodworking skills. These look like a lot of work.

Good luck

Matt
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Old 13th February 2009, 03:48 PM   #3
mjf is offline mjf  Austria
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hello.
i have found a simple closed box for this kef's.
greetings...............
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File Type: jpg kefbox.jpg (49.9 KB, 533 views)
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Old 13th February 2009, 04:23 PM   #4
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If we tell you about this website, will you tell us how you get on?

Check out the photo on the home page. Familiar?

Check out the forum.

http://www.hifiloudspeakers.info/
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Old 13th February 2009, 04:53 PM   #5
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What a wonderful score... I sold a ton of these in the late 70s, early 80s.

hese deserve to be in a transmission line... there are many clasic designs (diy projects & commercial), but Scott & i recently did up a TL using modern modeling techniques -- i would suggest a variation on that. We'll be happy to help configure it to be suitable for your needs... not really small thou. I also have copies of many of the classic diy articles.

There are a number of ways it could be configured... my 1st suggestion would be a small sattelie for the B110/T27 & a single common TL or a pair of TLs for the B139s (ie like the Fried HFried H or Fried M configurations

The weak point of this is the XO, so best to keep it where it is accessible if you ever decide it is worthwhile to start tweaking things. I know what i'd do (involves biamping, and the borrowing from the Fried mid/tweeter XO in the link above)

Here is a visualization of one of the possible TL configurations:

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dave
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Old 13th February 2009, 09:32 PM   #6
tsnell is offline tsnell  Australia
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Thanks for the responses everybody!

Great so it sounds like a transmission line is the way to go. I’ve attached a photo of the folded horn article (sorry I don’t have a scanner, I can scan it on Monday at work if anybody wants a better look) and some photos of the drivers themselves. There is some discolouration on the B139s, not sure if this will have an effect on sound, the rubber surrounds and everything look in great condition though.

The folded horn (TL?) in the article is interesting looking. It has the B139 mounted on the top of the enclosure. I am completely open to suggestions though and the satellite and TL woofer enclosure does sound very interesting (I may be biased though; my speakers are Edgar eve-II f in a similar configuration). Bi-amping will also be an option, we have a few old amps floating around now, the Yamaha A-700 and a Teac BX-300 are sitting in front of me right now.

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Old 13th February 2009, 09:46 PM   #7
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Yes, Sorry to hear of your mates Dads passing but great kit.
I sold all my B139's, but follow Daves advice and use them in a TL.
'
If the discolouration bothers you just glue some stiff dense paper on top, I used black paper I got from Officeworks 200GSM
Bi-amping is the way to go with these IMO, tweeters have got a lot better since the T-27 if I was to recommend changing anything ( I don't ) it would be the tweeter

Look at the last of the IMF studio reference monitors, they had the mid and tweeter set on top in a separate enclosure
Regards
Ted
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Old 13th February 2009, 10:02 PM   #8
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Those articles are the 2 Bailey articles that got things rolling, spawning Radford, IMF and TDL.

Modern TL simulation software lets us get closer to optimum, althou ny the time the later lines came along, so many had been prototyped they were getting pretty good.

If you can go active, a 100-250 Hz XO between the B139 & the B110 is suggested. Depends on the filam configuration.

dave

PS: i have both those articles (and the letters to the editor) already scanned & pdfed.
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Old 13th February 2009, 10:45 PM   #9
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Quote:
Originally posted by planet10
What a wonderful score... I sold a ton of these in the late 70s, early 80s.
Holey flashbacks batman! Did I ever have fun building those monsters, 90 lbs each!. They did sound pretty good, considering the stock crossovers.

Thanks for the nostalgia.

Jeff
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Old 13th February 2009, 11:36 PM   #10
tsnell is offline tsnell  Australia
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Is this http://www.marklev.com/IMF/SACM/index.html the monitor you are talking about moondog?

This article http://www.linkwitzlab.com/sb80-3wy.htm looks like the concept everybody is talking about.

But like you say planet10 I am sure TL and enclosure modelling in general has come a long way. Here are two other TLs I have found:
http://homepage.mac.com/planet10/TLS...map-100707.pdf
http://www.t-linespeakers.org/classi...fin/index.html

I also have a failed 41 Hz Amp 9 Basic attempt, from a recent Boominator project, that I could fix up for bi-amping these (It wouldn’t feel quite right using a chip amp with such retro speakers though). With the three drivers would bi-amping be the way to go, or would it be worth considering tri-amping?
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