Bought a pair of these on ebay and have finally gotten round to pulling the TS parameters off them using WT3 using the added mass method. Forgot to bring the TS spec in to work with me-doh, but did notice a few oddities:
One's impedence was about 15% higher than the other
The surround on both seemed to be a bit hit and miss where it was glued to the chassis-all glued solidly, just not uniformly, so the "bulge" of the suround is glued to the frame in some places-is this normal? If so I wouldn't say it spoke well of their construction quality!
Both of them ring like a bell if knocked with your knuckle-fundamental at about 250Hz, well out of the range I'll use them at but concerning none the less-anyone else noticed this? I'll proably just deaden them with some dynamat for peace of mind
I'm looking at running them isobarically so will build a baffle to go between them-wire the coils in parallel (as the drivers will be hooked to my amp) and re-measure to get the T/S as "one driver"-couldn't do this last night.
Anyone any ideas on whether it's worth trying to remove the souround and re-glue it? Looks like a bit of a PITA due to the deep outer flange on the basket.
One's impedence was about 15% higher than the other
The surround on both seemed to be a bit hit and miss where it was glued to the chassis-all glued solidly, just not uniformly, so the "bulge" of the suround is glued to the frame in some places-is this normal? If so I wouldn't say it spoke well of their construction quality!
Both of them ring like a bell if knocked with your knuckle-fundamental at about 250Hz, well out of the range I'll use them at but concerning none the less-anyone else noticed this? I'll proably just deaden them with some dynamat for peace of mind
I'm looking at running them isobarically so will build a baffle to go between them-wire the coils in parallel (as the drivers will be hooked to my amp) and re-measure to get the T/S as "one driver"-couldn't do this last night.
Anyone any ideas on whether it's worth trying to remove the souround and re-glue it? Looks like a bit of a PITA due to the deep outer flange on the basket.
I'll check them tonight, I'm not sure they are the SP1044-I've had them close to a year and did try finding the specs when I got them and couldn't so purchased the woofertester in PE's Thanksgiving sale.
Looking at this link:
http://www.kef.com/Resources/KEFUnits/A History of Kef Drive Units - Issue 2.pdf
I'm pretty sure my drivers are the earlier, unpictured, model. The have a round motor with the brass screws seen in the B110 type 6362 picture futher up the article.
I'll publish the specs I've pulled off them tomorrow
Looking at this link:
http://www.kef.com/Resources/KEFUnits/A History of Kef Drive Units - Issue 2.pdf
I'm pretty sure my drivers are the earlier, unpictured, model. The have a round motor with the brass screws seen in the B110 type 6362 picture futher up the article.
I'll publish the specs I've pulled off them tomorrow
TL Links
Typically taken with very low voltage they'll be different than factory (that typically use higher drive levels), you end up with another point on the T/S curve.
dave
Cheers, not the driver pictured there, mine has all round motor structure.
As I can't find sepcs on mine I'll just have to go with WT3's results
Thanx for that doc, haven't seen it before.
Both major types of B139 are pictured in the doc. The older ones have the non-sdonized racetrack frame. Newer ones have the black shaped frame.
dave
Welcome to the wonderful world of KEF in de late seventies/early eighties. QC either absent or on sick leave.
I owned a number of B 139 's with Fs around 36 and 40 Hz (!) and rubbing VC's at any level over 2-3 Volts driving voltage. Cones were not flatly glued in place..
They worked reasonably well in my Chris Rogers' Practical Hifi ' PRO 9 TL, but in terms of build quality, power handling plus specs they were definitely not something to write home about.
Hope you have more luck with your samples.
Regards,
Eelco
I owned a number of B 139 's with Fs around 36 and 40 Hz (!) and rubbing VC's at any level over 2-3 Volts driving voltage. Cones were not flatly glued in place..
They worked reasonably well in my Chris Rogers' Practical Hifi ' PRO 9 TL, but in terms of build quality, power handling plus specs they were definitely not something to write home about.
Hope you have more luck with your samples.
Regards,
Eelco
Lol-British "build quality" in the 70s was bloody awful on cars-so shouldn't have expected much better on drive units! My old boss used to run a body shop and found welding rods tacked into B-pillars with nuts welded on so they'd rattle round bends in numerous Rovers-no wonder we no longer make much of anything!
Mine do seem ok, though haven't really tested them much other than visual and pushing the cone in and out-no rubbing I can find-but trying to recall the Fs of my drivers I'm sure they were well out from each other!
Dave, you wouldn't have any ZMA and FRD files for the SP1044 as well as the SP1003/B110 and SP1032/T27 would you? I'm trying to learn Speaker Workshop and am having trouble creating my own ZMA and FRD files from the frequency and impedance graphs I've been able to find (including ones you've posted
). I haven't the fascilities to measure my speakers and there seems to be a paucity of raw files and graphs on the net for these classic drivers, which surprises me.
). I haven't the fascilities to measure my speakers and there seems to be a paucity of raw files and graphs on the net for these classic drivers, which surprises me.
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Sorry, forgot to take pics (old school friend came round last night-too much curry and beer) but did remember to email myself the T/S I pulled off the two drivers:
As you can see there are some quite large variences! Speakers had been stored in the same place, same test conditions, I made 5 measurements on each driver and will average them-but they were all close to those above.
How do you insert an excel page? I keep trying, looks ok when I do it but as soon as I save the post it jumbles it all up
As you can see there are some quite large variences! Speakers had been stored in the same place, same test conditions, I made 5 measurements on each driver and will average them-but they were all close to those above.
How do you insert an excel page? I keep trying, looks ok when I do it but as soon as I save the post it jumbles it all up
Attachments
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Ellipse Surface Area - Engineers Edge After finding the elliptical driver's surface (354cm2 ?), you can assign a diameter for same circular surface in the program.
It should near it, but lets accept KEF's 55sqin or 354cm2, that would include half way to surround, and it would be 212.35mm D if circular. There is also the later paper with FR charts that states 349cm2, still very near. Do the pure ellipse A=piAB on the B139 including half surround in either direction to see if it yields near what KEF gives, just for fun.
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