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KEF C80 Bass issue
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willem-57
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Joined: 18 Jul 2014
Posts: 218
Location: Netherlands

PostPosted: Sun Oct 12, 2014 1:49 pm    Post subject: Reply with quote

I came across this topic and have another question about the limited bass response of the C80 that i've been reading on different forems.
As most of you already know i've had a CS7 with the 8 ohm version of the B139B for the bass. The bass chamber of the CS7 is 70 litres, but with the C80 (B139B 4ohm) is it only 47 liters.
Maybe stupid question, but when you increase the C80 baschamber, say with 8 litres, what would be the result? Floppy or too mutch bas ,or just deeper, witch would be nice.
Who knows Question

And is there a Datasheet of the B139 bass unit (SP1212)?
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audiolabtower
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Joined: 06 Jan 2009
Posts: 544

PostPosted: Sun Oct 12, 2014 7:29 pm    Post subject: Reply with quote

I don't think 8 litres would give any noticeable difference on its own. The standard BBC type mid size box (eg Spendor BC1) was around 44 litres. To get another octave in the bass, more importantly with more power handling, you had to go to a 12in unit in 70 or 80 litres like a Kef105. To get even more you had to go coupled cavity in a 107 and "cheat" on the power input by going to 4 ohms. So 10% difference in volume will not do much when you already have a pretty much full range system, as opposed to a mini like the 3/5a or 101.
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willem-57
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Joined: 18 Jul 2014
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Location: Netherlands

PostPosted: Mon Oct 13, 2014 7:51 am    Post subject: Reply with quote

But still i find it a bit odd that the older B39's in the concerto, CS7 and other designs had mostly 70 liters or more and the B139 in the C80 only 47 liters. Why did Kef did this? Is the 4 ohm version so mutch different from the older 8 ohm versions?
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proffski
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Joined: 22 Aug 2003
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Location: Tewkesbury UK

PostPosted: Mon Oct 13, 2014 9:21 am    Post subject: Reply with quote

The Concerto was a reflex designm the C80 is a sealed box.
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willem-57
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Joined: 18 Jul 2014
Posts: 218
Location: Netherlands

PostPosted: Mon Oct 13, 2014 4:14 pm    Post subject: Reply with quote

Thx, the same confusion i found on another topic on this forum: http://www.hifiloudspeakers.info/speakertalk/viewtopic.php?t=1466&sid=b4357a95eabe80c908c939bec6b4d67d
If you read that the author have the same confusion that i have, in a closed box model (cs7) 70 liters, another one (cantata) 60 and in the C80 only 47, all with the same woofer.
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proffski
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Location: Tewkesbury UK

PostPosted: Mon Oct 13, 2014 4:21 pm    Post subject: Reply with quote

I'll check if the Thiele / Smal parameters are the same for all bass drivers some weekend then run the simulation software...
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willem-57
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PostPosted: Mon Oct 13, 2014 4:29 pm    Post subject: Reply with quote

Thx Very Happy
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darkmatter
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Joined: 26 Aug 2010
Posts: 9
Location: Eastern England

PostPosted: Thu Nov 27, 2014 11:59 pm    Post subject: Reply with quote

Good to see some comments about the C80

I picked up a nice pair recently and am happy to say that I will be keeping them Smile They are in my second system having been searching for a good pair for a number of years.
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