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KEF 104/2 B110 mids are "chassis-less"?

 
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centaurus
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Joined: 21 Apr 2006
Posts: 125
Location: Okland, CA

PostPosted: Sat Sep 09, 2006 1:21 am    Post subject: KEF 104/2 B110 mids are "chassis-less"? Reply with quote

i found this on google groups. guy says he used to work for KEF. sounds like he knows his stuff too:

Every 104/2 used a pair of chassis-less mid drivers - and these can come unstuck at the roll surround, where it meets the front of the cabinet. This might cause a "tizzing" sound, due to resonance (as the glue may have lost it's ability to hold the surround to the cabinet). UNDER NO CIRCUMSTANCES TRY TO REPAIR THIS YOURSELF. This is becasue you will probably make the driver unrepairable. And if that happens you will need a complete mid-range assembly (ie the whole front of the top half of the speaker must be changed...as the drivers cannot be replaced independantly).

so, there's no chassis for the mids? huh? what the heck hold the magnet in place? any body have pics of this? there's is an access panel on the back of each mid cavity. i ain't touchin' it though Wink

thanks,
Robby
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Mon Sep 18, 2006 2:53 pm    Post subject: Reply with quote

That's right. The magnets only had the spider (rear suspension) platform screwed to them and the magnet was screwed(?) to the back of the cabinet before being semi submerged, I think, in some quick setting cabinet damping goo.

The units were then built (two at a time) directly into the mid cab. This arrangement got round the problem of the std B110 steel chassis being a rather "acoustically closed" design. Specifically, if mounted from the front, the thickness of wood could often almost close off the chassis windows.

SG
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centaurus
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PostPosted: Mon Sep 18, 2006 5:50 pm    Post subject: Reply with quote

thanks for the info!

so, if one of the drivers blows, you are basically screwed?

Robby
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speakerguru
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PostPosted: Wed Sep 20, 2006 12:24 pm    Post subject: Reply with quote

centaurus wrote:
thanks for the info!

so, if one of the drivers blows, you are basically screwed?

Robby


Yes.

Chassis or no chassis, KEF don't make B110s any more.
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centaurus
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Joined: 21 Apr 2006
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Location: Okland, CA

PostPosted: Wed Sep 20, 2006 5:35 pm    Post subject: Reply with quote

no, i mean i can find B110's on ebay, but i figure even if i could get the ones out of my 104/2, you'll never see one like those for sale on ebay.

which begs the question (not that i plan on blowing them up). if i had to replace them, could i retrofit a "regular" B110?

Robby
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speakerguru
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PostPosted: Thu Sep 21, 2006 11:39 am    Post subject: Reply with quote

The 104|2 was a 4 Ohm "resistive" system so the B110s were probably both 8 Ohm units 'sort of' in parallel, so that you ended up with 4 Ohms after all the extra impedance compensation components. If so, then the moving part were basically the same as the SP1057 used in the 105, etc.

As for retrofit, do you mean hack out the mid cabinets to take conventional chassis units or attempt to transfer the moving parts only? Both very difficult and very risky. I don't even remember how the leadout braids were soldered (inside a closed box) so you're on your own there!

SG
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centaurus
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PostPosted: Fri Sep 22, 2006 3:18 am    Post subject: Reply with quote

i meant using the regular chassis B110. i'm just saying if something blew in the future. i'm only use 60 watt tube mcintosh amps so i don't plan on blowing anything up. just wondering what to do if something did happen.

see ya,
Robby
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greve
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Joined: 23 Oct 2006
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PostPosted: Sat Oct 28, 2006 8:08 pm    Post subject: Reply with quote

OK, I'm in this mess now. I bought a (very cheap) pair of 104/2 in which I knew most of the drivers were damaged (I think the owner let his kids loose near the speakers while he was away - for 3 days... Shocked ).

BUT, this was unfortunately before I read this post about the difficulties to change the midrange drivers Sad I've now taken them apart and I can clearly see the problem.

BUT (another but), KEF Support has said that they have replacement drivers for these, so I wonder what they're selling if the midrange/tweeter assembly as a whole needs to be replaced. This is what they quoted me:

Quote:

Parts are still available for 104/2.
All prices exclude VAT.

Tweeter R1548X 15.77 each
Mid range unit R1274X 121.06 each
Bass Units R1465X 68.62 each


So what do you experts suggest I do: Forget about the whole project and buy something else or is there hope for my 104/2s?
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centaurus
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PostPosted: Sat Oct 28, 2006 10:19 pm    Post subject: Reply with quote

those are NOT direct replacements. they are just whatever they have that will fit.

not recommended. they do not have anything, driver-wise (IMHO) that competes with the B110 mids and you can buy a pair of Vifa MG27-04 for $22.10/piece form madsound that might even actually sound better than the stock T33b. i have them in mine and they rock!

here's a mid/tweeter cavity that didn't sell on ebay: 140044276627

see ya,
Robby
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