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Old 16th September 2011, 10:45 AM   #21
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lol-will get the tape measure out and do some maths on the weekend!
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Old 16th September 2011, 10:50 AM   #22
Salas is offline Salas  Greece
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Should be kinda short to KEF's by missing those curved side triangles between the two circles, we still got the ~350cm2 KEF spec. Its funny we even look in to it with interest when the two drivers have so wide a tolerance anyway. But inquiring minds wanna always know.
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Old 16th September 2011, 12:08 PM   #23
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I just want to be sure that what I am doing is right-if KEF can't do it right it's up to me to hold up the "British end"!
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Old 16th September 2011, 02:46 PM   #24
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Default Kef b139

I have used a Kef b139 as a subwoofer with both Quad esl 57 and martin Logan cls .They were very clean when not over driven, I don't know how low the went in my vented enclosure but organ pedals were heard. IMF used the b139 in their reference monitor and in its time had very good bass and could play fairly loud, Definitely not home theater loud. I owned a Morgan plus 4 for ten years in the sixties.I have very fond memories of the Morgan. My teeth still hurt.
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Old 16th September 2011, 02:58 PM   #25
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Hi BaronGroog,

Would you care to also do the T?S parameter etraction with Delta V(olume) method? Often the Delta Mass method results in lower Fs and larger Vas than the Delta Vol method. Of course it should not theoretically speaking, but in practice it often does.

BTW the difference between the samples conforms my own experience. So far I enjoy your journey into KEF land!

Eelco
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Old 16th September 2011, 07:16 PM   #26
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The area of the piston can be calulated as a circle with the diaphram width (including half the surround as Salas mentions) the diameter + the area of the rectangle left over when you slice off the semi-circles at either end.

Get those drivers on the breakk-in bench and get at least a couple hundred hours on them. One looks to be suffering fron SSS (stiff surround syndrome). Some Armour All or similar may be required if that doesn't help as much as you'd like. They will never return to as new thou -- one of the long term issues with rubber surrounds,

dave
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Old 17th September 2011, 01:08 PM   #27
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Soundalot, sounds good to me! ACn't wait to hook them up

Eelco-I will do at some point, need to make the box 1st Gonna do one with a removable baffle and make it large enough to accomodate a 15" (can't see me needing any larger)

Dave, as I have a small house and an "understanding, but not loving it" Missus I'll not really be able to do that-as the drivers are going into an isobaric clamshell config I can't see the difference being too huge a problem-anyone got any thoughts on that?
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Old 17th September 2011, 02:25 PM   #28
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To break-in the 139s, as you must, place them close to each other, working out of phase. Will not be to much noise. I have used them in the 70īs and 80īs, both the OS and newer, and they can vary in parameters rom sample to sample. No need to judge yours without break-in, so do as Dave told you. Itīs totally meaningless to measure them before.
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Old 19th September 2011, 08:14 AM   #29
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But the drivers are second hand so will have been "broken" in anyway. Playing them both for the same amount of time will surely just move them along the same amount-if any at all?
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Old 19th September 2011, 12:37 PM   #30
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Hey Baron,
If they have been stocked for a while you should run them in anyway, albeit for a shorter time. Run them until Fs doesnīt get any lower.

Last edited by revintage; 19th September 2011 at 12:40 PM.
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