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Old 6th February 2012, 02:32 AM   #31
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Originally Posted by system7 View Post
My own experience of bextrene bass/mid units is when they got hot at parties, they turned to jelly. Dull sounding too.
And by then, the T27's are just a distant memory.

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Old 6th February 2012, 03:03 AM   #32
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Planet10 I found specs for the Kef B200G SP 1075 used in the CS3 and CS5 it is the 3 holed triangular version not the driver specs you requested but all I could find in my archives. Mmd 24.3 Grams Fs 27hz, .Vas 121 liters , Re 4.7ohms , Z min 5.3 ohms at 160 hz, Bl 6.82, Qms3.03 , Qes..42, Qts. .37, xmas 6mm peak to peak, voice coil diameter 32.6mm. 18 oz. ceramic magnet, Efficency 90db 1watt 1 mete,r Frequency response 25-3500hz. It also has box alignmensts In old Madisound catalog.
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Old 6th February 2012, 07:24 AM   #33
system7 is offline system7  United Kingdom
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Couldn't quite follow all that, bjorno, but 3.29 mH makes no sense where it is in michelino's schematic, eh? I wasn't completely guessing in suggesting 0.6mH.

Dug up a couple of crossovers from the KEF 104 and KEF 104ab (later acoustic butterworth) speakers which had that ABR thingie. Here with the B200 SP 1039 which is 0.25mH Le and a bit higher Qts @ 0.4 or so. The tapped inductor is an acoustic contour switch with three positions. Gives +/_ 2dB @ 1.5 kHz.

KEF seemed to do some quite odd things with those B200 units. I expect the rising impedance makes the lowpass crossover point quite vague. The T27 seems to get a more exact treatment. The Calinda seems to exactly inherit the KEF 104ab highpass which is very near 3.5 kHz on 8 ohms when I checked it.
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File Type: jpg KEF_104ab_crossover.JPG (42.8 KB, 287 views)
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Old 6th February 2012, 07:42 AM   #34
system7 is offline system7  United Kingdom
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Oh, just so you can more easily follow what we are scratching our heads over, it is this strange schematic for the KEF CALINDA and KEF B200 SP1054, which makes no sense at low frequencies.

Click the image to open in full size.
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Old 6th February 2012, 08:09 AM   #35
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Thanx, i've grabbed that

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Old 6th February 2012, 08:03 PM   #36
DrBoar is offline DrBoar  Sweden
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The lower half of the Xover for the T27. A 18 db/octave highpass filer and then some EQ filter on top seem pretty standard KEF style.
The LCR filter for the B200 might be OK my problem is that 5MicroFarad cap in front of the inducer? The large coil is not impossible the Calinda had a narrow baffle and to correct the 6 dB baffle step it is quite common to have about twise as large coil as classical calculations would predict. As there is not RC link across the B200 terminal the effect of the coil will be affected by the rising impedance of the B 200. But what the heck is the cap doing in front of the coil??
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Old 6th February 2012, 08:31 PM   #37
system7 is offline system7  United Kingdom
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Yes, DrBoar, it may just be in the wrong place. I saw a photo of the Calinda crossover, and there WAS a large ferrite-core inductor there.

I was looking at the little KEF R101, which had the B110 unit in a BBC LS3/5A monitor type arrangement.

LO, the inductor is in front of the capacitor with a similar LCR trap! Don't have modelling software to look at that though...FWIW, KEF were kinda rough and ready with bass rolloff on the B200. Often nearer 2.5 kHz on the component values into 8 ohm.
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File Type: jpg KEF_R101_crossover.jpg (44.2 KB, 234 views)
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Old 7th February 2012, 09:08 PM   #38
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Ok, thanks another time .... the strange Calinda XO is not a problem to me: maybe a 2nd order at 2-2.5-3kHz could be enough in my design...
Now, the big question is: how much should i spend to buy a mid-woofer that sounds better than SP1054? I have no experience, I'm only 21 and I can't afford expensive toys ... I only know that Sp1054 requires big enclosures (I have max 30-35liters...) and was mounted in Kef Calinda... 1970's speakers
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Old 7th February 2012, 10:27 PM   #39
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I'd incline to stick with that B200 for now. 18L is alright if you stuff a sock in the reflex. I was really trying to figure out a crossover for you. I'd think you won't have much difficulty matching it to a 89dB or better tweeter with a third order crossover, like a Seas Prestige 27TFFC or Morel Classic CAT298. But you could even just buy a cheapie dome and run it off a single 2.2uF.

As it goes, I reckon 1.5-3mH and 5uF 2nd. order, with or without the trap, can't be very far wrong for that B200. I do think the coils go before the capacitor in the crossover, and looking at it confirms it. Red is woofer hot. Blue is tweeter hot and white is hot of input. Black is earth. The capacitor top right is the 5uF.

Enjoy the pictures of your B200 in it's youth!
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File Type: jpg KEF_Calinda.jpg (57.5 KB, 224 views)
File Type: jpg KEF_Calinda_crossover_1.JPG (90.5 KB, 83 views)
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Old 8th February 2012, 07:40 PM   #40
RDLewis is online now RDLewis  United Kingdom
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Many years ago I aquired A B200 from a friend, who used it as the bass unit in a three way TL. I decided to try it in one of the 2 way designs common then using the above (largely Kef type), but using an Audax tweeter, I could not stand the T27. Anyway, the results were pretty poor, undynamic, flat, coloured. I could not understand why it was held in high regard.

A few days latter I deceided to try it out with a simpler Crossover, namily a single inductor, I think it was 1mH, and second order tweeter section. The differance was amazing. It showed me that the B200 was a much better driver than I thought. I have heard similar improvements from those who did similar things with the B110. The old Kef crossovers just sapped the life out of those drivers, all with aim to get the flatest response.
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