Upgrading R50 KEF TL

[soongsc]

Originally posted by pinkmouse
For me, the B110 has always been the weak link in those big old TLs and Kefs. If you can get to hear the new Richard Allen versions to see if they are worth the money, then that may well be the way to go. Get that midrange sorted and you will have very nice speakers indeed.

Is the difference just audible or is it measurable?

[ericallan]

Try www.falconacoustics.com . They have the replacement crossovers as new or in kit form - just checked ; £22 each. The owner worked on a lot of the early KEF units and has a wealth of experience. Nice guy and sensible prices too. They sell Coles as well at £18 each.

[essence]

Originally posted by pinkmouse
For me, the B110 has always been the weak link in those big old TLs and Kefs.

I have read somewhere recently about the 'quack' in the B110, and now it has been mentioned I can hear it clearly and I hate it! Or else my mid range box is not sufficiently damped (on reflexion - sic - and looking again at my reprint copy, I cut a lot of corners building these beasts - I certainly didn't put enough wadding at the lower back of the TL.).

I bought my wife for Christmas a Teac H350 (Cd, DAB, amplifier, I paid too much but wanted it in time) and TDL KV1 bookshelf speakers (only TDL because of the brand and history, yes I got dupped, I realised they are nothing to do with old company, but didn;t realise richer now own the brand) and it sounds very good for what it is (at least compared to her old ?ASDA AIWA system which was driving me mad), and made me realise the limitations of my high end system.

Good news - Concerto xover has clearly marked specs (caps all say ecap, so i assume they are electrolytics and need replacing, which is simple), and I have full specs of the R50/HiFiAnswers.

I'll keep y'all informed if and when I progress.

[jerryb]

I'm just starting renovating a pair of R50's and can endorse what ericallen says - the best place for the crossover and the Coles 4001G's is Falcon Acoustics who have been extremely helpful.

Replacement KEF drive units are generally pretty easily found on eBay, although it's usually cheaper to buy an old pair of Concerto's and keep the units for spares rather than buy the units individually.

Being TL, they may not be the most efficent speaker around but when you hear the overall soundstage they produce with effortless deep bass in a decent sized room the design is still outstanding even after 30 years in my opinion.

There's also a vast amount of information on the KEF units etc. on hifiloudspeakers.info

Hope this helps, I'll be very interested to hear how you get on!

[Andy G]

I am looking at doing the 4-way using the old Kef B139, Vifa C13, Kef T15 and Foster ribbon. I got the Kef's for nothing, the Vifa at a sellout and the Foster ribbon was acquired cheaply because I felt the Kef T15 didn't have much top end. (is actually a 35mm dome with Fs=500, which explains the problem)

Note the shape of the Vifa C13 is very similar to the old Kef B110

I've attached plans. The reason for the height of the tweeter is that these are aimed as being my main HT speakers, and 1050cm is the mid height of my screen.
(the second hand nature of the drivers will make them near impossible to sell, so I may as well design them for a specific duty for myself.)

This is a prelim sketch only, so if there are any comments that might help,... thanks

I have also linked to a speculative 4-way series x-o layout which might interest some of you.

http://users.tpg.com.au/users/gradds...ed%204-way.jpg

http://users.tpg.com.au/users/gradds...ries%20x-o.jpg

[wmeyer57]

Hi,

your 4way speaker arrangement was also used in the first IMF speakers. Later they were replaced by speakers of the "same" specifications, but done with modern materials by TDL (Transducer Developements Limited).

I have a complete kit of this speakers, that means:

oval bass speaker: TDL 128
midrange: B110 lookalike
treble: 25mm aluminium dome tweeter with ferrofluid damping
supertweeter: 19mm softdome.

These are speakers originally used in the TDL Monitor TL

I've also got a fitting crossover, which is done by Falcon Acoustics.

Shame on me, I've never built up this kit (didn't have any time) , but I think, these speakers should perfectly fit into your cabinet. So..., if I can give you any further help, please send me an email.

Thank's and have a nice time

Wolfgang

[essence]

It's been a long time, but I've been busy, now I'm thinking of a project over the Christmas break...

My big problem remains what to do with the B139. I don't really want to replace with second hand or anything - I don't quite see the point of using something which may have ended their shelf life - eg. how good is the rubber surround?

So, I have a choice of maybe dual Vifa P17WJ (or equivalent Peerless PL18), in some push push arrangement, or else..

I've noticed the Tang Band 8x12 which might be ideal, but have seen nothing about them here, I can buy them in US or distributors in Germany (no UK distributor).

B139 details

fs 25Hz
Effective area Sd 354 cm2
Effective moving mass 43.5 g, 1.53 oz
Damping:
mechanical 5.5
electrical 0.4
total 0.37

Vas 164 litres

sensitivity pink noise input for 96 dB SPL at 1 m on axis 11V RMS
force factor BL 12.3 N/A


W8Q details

fs 27Hz
effective piston area 460 cm2
moving mass 115 g
Qms 4.21
Qts 0.29
Qes 0.31
sensitivity 1W/1m 89db
Vas 89 litres
force factor BL 14.15 TM (what unit is that?)



Anybody know anything about them? Although I'm a physicist I don't know what these parameters are in detail, or which are important for speaker design. But at first glance there is a lot of similarity. I would use them only for low frequencies, crossing over to a mid range unit.

Remember, I want to keep the existing boxes, just replace units and front panel.

Let me measure if two PL1's can fit...probably not.

[essence]

On further investigation, maybe the TB is not quality I am after, frequency response not exactly flat.

Looking at others with similar fs to B139, I find Peerless XXLS 830843

Parameters are:

fs 25 Hz
Sd 352 cm2
MM 79.9 g
Qms 9.03
Qe 0.47
Qt 0.44
sensitivy 87.2 dB
Vas 86.7 ltrs

fs and Sd are similar to B139, so at first glance my existing TL cabinet will do the job. How important are the other parameters, eg Vas, for a TL?

I looked at Peerless 830452 but it had a uch lower fs, which I am beginning to understand would mean a much longer line.

[essence]

OK, doing a bit more investigation, looked at

http://www.t-linespeakers.org/design...ies/index.html

and I'm comparing 830843 with B139.

Qts. 830843 is 0.44, B139 is 0.37. Not too different. Above the limit mentioned of 0.3 for TL's.

fs is 25 for both.

Vas is 86.7 and 164 ltrs respectively.

Sd is 352 and 354 respectively.

BL is 12.5 Tm and 12.3 N/a respectively. On http://www.thielesmall.com the B139 is give as BL of 10.6 Tm

So is this a close enough match to use the same TL box?

[pinkmouse]

If there's nothing wrong with the B139s I wouldn't worry. If the surrounds show no sign of splitting or perishing, you should be good to go for at least another 5 years. They are very robust.