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Kef Concerto Kit - enclosure question

 
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KefHeir
Intermediate Contributor 25+


Joined: 24 Jun 2019
Posts: 25
Location: London

PostPosted: Fri Nov 20, 2020 9:57 am    Post subject: Kef Concerto Kit - enclosure question Reply with quote

Hi there
I was wondering if anyone could advise me concerning some homemade speaker enclosures I've inherited, based on the Kef Concerto. The units have a sub-enclosure for the B110, but it's very small - internal dimensions are 21cm x 14cm x 14cm (which I calculate to be about 240 cubic inches). This is correct according to the original spec from Kef which I also still have, remarkably.

The sub enclosures have no acoustic foam damping so I wanted to add some, but of course this would reduce the already fairly small volume of free air. So my question is: what's more critical, preserving the free air volume or adding some acoustic foam? Any thoughts would be much appreciated, including on why Kef would have stipulated such a small enclosure for the B110? Maybe it's normal, I'm not sure, but most of what I've read suggests a bigger enclosure would be more appropriate for a 5-6" drive unit.

Thanks, and I hope people are finding ways to survive the pandemic, wherever you are in the world

(I would have included an image of the enclosure design drawings by Kef but I can't figure out how to insert an image here!)

Darren
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speakerguru
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Joined: 18 Nov 2005
Posts: 1192
Location: Green Hut, Tovil

PostPosted: Fri Nov 20, 2020 12:01 pm    Post subject: Reply with quote

Fill away as much as you like. The box volume has little effect on a MF unit whose LF output has been cut off by the crossover filter.
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KefHeir
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Joined: 24 Jun 2019
Posts: 25
Location: London

PostPosted: Fri Nov 20, 2020 12:15 pm    Post subject: Reply with quote

@Speakerguru

Thanks so much for the reply. Ive just got some brand new B110s to refresh the old 80s ones (though still working) so very good to have some reassurance on this.
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SaSi
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Joined: 24 Aug 2008
Posts: 256

PostPosted: Fri Nov 20, 2020 4:19 pm    Post subject: Reply with quote

Actually, filling a sealed enclosure with acoustically transparent material (like poly-fil, actually increases the effective enclosure size for the performance since the filling material slows down the speed of sound waves.

In fact, the B110, in midrange tasks, doesn't need all that space for loading.
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KefHeir
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Joined: 24 Jun 2019
Posts: 25
Location: London

PostPosted: Fri Nov 20, 2020 5:28 pm    Post subject: Reply with quote

@SaSi - Thanks very much for the reply; very interesting (if counter-intuitive). It's difficult to get authoritative information on this (elsewhere I read it's the free air that matters) so really great to have found this online community (Kef themselves directed me here).

With that peace of mind I'll go ahead and fit the new B110s this weekend. Thanks again
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SaSi
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Joined: 24 Aug 2008
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PostPosted: Fri Nov 20, 2020 8:51 pm    Post subject: Reply with quote

If you would like to get a concise, all-in-one, reference on loudspeaker design and construction, I highly recommend Vance Dickason's "Loudspeaker Design Cookbook". Currently in it's 7th edition.

You can learn how loudspeakers, drivers and crossovers function, even if you don't plan on building any.
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KefHeir
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Joined: 24 Jun 2019
Posts: 25
Location: London

PostPosted: Sun Nov 22, 2020 3:39 pm    Post subject: Reply with quote

Thanks @SaSi for the book reference; sounds like a must-have. I've just refreshed all the drivers with new ones from Falcon Acoustics so that improvement will keep me going for a while but sounds like crossovers are interesting territory for future tinkering. I'm using one designed by Wilmslow Audio specifically for these three Kef drivers, but seems like there are many ways to go with crossover design.
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