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Calling SpeakerGuru: KEF Reference 103.4 - cooked B160's

 
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slimecity
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Joined: 18 Mar 2018
Posts: 2
Location: New Zealand

PostPosted: Mon Mar 19, 2018 5:10 am    Post subject: Calling SpeakerGuru: KEF Reference 103.4 - cooked B160's Reply with quote

Hi - won a pair of KEF 103.4's at auction and the tweeter and mid are fine however I knew the surrounds of the bass drivers were likely to be shot. I also knew if the last owner had driven them with perished surrounds the bass drivers could be shot. The bass drivers are B160 (SP1275), 6.5” inch paper cone drivers.

All four of the drivers had rubbing and two were OC. All had been subjected to overdriving & heat to the point that the plastic guide in the centre for 2 of them had melted.

I managed to knock the price down as half the speaker is working fine. As I got them so cheap - Im happy to tolerate a "close enough" approach for bass repair. It doesnt seem like I can get a recone kit for these drivers. Sending them to and from KEF (from NZ) isnt an option due to weight.

Anyone know of a potential replacement driver for these. I know that the xover etc will be tight spec however as I say above, “close enough” will be fine. I have found online specs for this B160 driver (there is more than one B160, however this is described as a “bass” driver, which is what these are):

KEF B 160 / 8 Ohm, 8 Ohm, 50 W, woofer

thiele-small data:

Re 7.4 Ohms
Le 0.61 mH
fs 40 Hz
Qms 5.45
Qts 0.30
Qts (8Ohm) 0.33
Sd 131 cm3
Vas 42 Liter
Cms 1.75 mm/N
Mms 9 g
B*l 7.3 N/A
SPL 91
I have found a probable replacement driver which has a lot of specs looking favourable (The Vas is close, the resonant freq is close, the only issue is the spl is 86db, compared to the former 91. This is disappointing but its been very difficultly trying to find a driver with close vas).

parts-express.c0m/visat...eated-paper-cone-8-ohm--292-568#lblProductQ&A

I have also emailed KEF in the UK and US however don’t expect too much help from that channel.
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speakerguru
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Joined: 18 Nov 2005
Posts: 990
Location: Green Hut, Tovil

PostPosted: Thu Mar 22, 2018 10:45 pm    Post subject: Re: Calling SpeakerGuru: KEF Reference 103.4 - cooked B160's Reply with quote

slimecity wrote:
All four of the drivers had rubbing and two were OC. All had been subjected to overdriving & heat to the point that the plastic guide in the centre for 2 of them had melted.


Same thing happened to the pair I loaned to our local Am-Dram group. The surrounds perished; no one noticed until overdriven, two bass units went o/c. Then someone noticed lack of bass!

I repaired them by last resort rebuilding as described elsewhere on this forum. Had to lose a turn on the bottom of each o/c voice coil when splicing the broken ends together. Didn't have melted plastic to contend with though.

If you can't go my route, you'll have to try out different alternative woofers. With coupled cavity designs, as long as the suspension is not too stiff, the only parameter worth worrying about is the moving mass. Get it within 5-10% of the originals and everything else will be close enough (~1dB).
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slimecity
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Joined: 18 Mar 2018
Posts: 2
Location: New Zealand

PostPosted: Thu Mar 22, 2018 11:19 pm    Post subject: Reply with quote

Awesome thanks for that Guru! I will make some inquiries now.

I am looking at getting new drivers. Not ideal I know.

Thanks for confirming the most important parameters.

A question - if the Vas exceeds the specs of the original driver, is this OK?

Also - if the moving mass exceeds the specs of the driver by say 4-5g, is this also OK?


Simon
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Fri Mar 23, 2018 12:09 pm    Post subject: Reply with quote

slimecity wrote:
A question - if the Vas exceeds the specs of the original driver, is this OK?
Large Vas is no problem. The actual box volume, which appears in parallel with Vas in the equivalent circuit, would then dominate the alignment.
slimecity wrote:
Also - if the moving mass exceeds the specs of the driver by say 4-5g, is this also OK?
Mass should be not more than +/-10% from the original.
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SaSi
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Joined: 24 Aug 2008
Posts: 235

PostPosted: Tue Mar 27, 2018 4:59 pm    Post subject: Reply with quote

Just to bring an example, I re-created a pair of 107s only having the domes and original crossovers. I didn't have the boxes as the previous owner threw them away after a flood. Sad

I created drawings of the couple cavity boxes as best I could from pictures, cross-sections and measurements given to me from various forums and then tried several B200 versions I had.

Did actual response measurements by placing a mic close to the front vent and covering everything with a stack of sound absorbing material and a blanket on top (mostly to keep the foams from flying around).

I quickly discarded the SP1022, SP1039 and SP1054 variants because they gave nasty peaks which I attributed to the large magnet.
I also tried SP1063, SP1069 (paper cone but 16Ohms), SP1070 (again paper cone) SP1075 (5 Ohms) and SP1014 and the SP1014 was giving a very good and smooth response, especially when combining the B110 output and having the KUBE connected. The SP1070 was not bad as well, but I didn't have 4 of them on hand.

I understand that the original B250 in the 107s have paper cones and the B200 SP1014 is Bextrene but the measurements were ok and they now sound awesome.
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Notthatclever
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Joined: 05 Apr 2018
Posts: 6

PostPosted: Sat Apr 07, 2018 2:16 pm    Post subject: Reply with quote

I have 2 x B160 sp1203, 6 ohm which are going spare
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