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Kef Coda II tweeter

Mr Pig

^'- -'^
Picked up a pair of these old Kefs with two dead tweeters. Looking to replace the tweets with cheap units rather than bin the speakers, which just seems wrong.

The fitted unit is the SP1081 but I can't find the sensitivity of it. Anyone know? I've found a cheap driver that will fit and look ok but I don't know how it will match up.

Thank you.
 
Don't think that's the right one!

The original unit is definitely made bu Audax rather than Kef and there's one on ebay with a picture.

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=274449411090

so it's a HD100D25

Hence either of these is an upgraded replacement

https://www.falconacoustics.co.uk/d...udax-tw025a0-hd12x9d25-hd12x8d25-tweeter.html

https://www.falconacoustics.co.uk/d...w025a0-appc2-hd12x9d25-hd12x8d25-tweeter.html

The only difference other than price is where the terminals are located.
 
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Strangely enough so did I and very good they were too, but the coda 2 uses completely different drive units so the 3's may not be a good indicator.

The OP presumably still has the dead ones so can see what's written on the back.

Trouble is that at the price point the coda 2's might be a bit beyond economic repair since the minimum spend of £80 is more than they'd be likely to fetch.

The Falcon site also mentions availability of voice coils so that might be worth checking out as a slightly cheaper option, but the saving doesn't really seem to be worth the amount of faff.

https://www.falconacoustics.co.uk/d...2-voice-coil-hd12x9d25-hd12x8d25-tweeter.html

They will probably know if that's likely to fit the old body or not.
 
Trouble is that at the price point the coda 2's might be a bit beyond economic repair...

Exactly. They're only worth £30 to £40 on a good day so I'm not putting much money into them. I've found tweeters that will fit, are 8ohm and have a 95db rating but I don't know the efficiency of the originals. I've tried googling it but I can't find it. There are several versions of the T33. These ones say 8ohm, SP1081 on the back but that's it.

The possible replacements are only £25 for a pair and I'm willing to spend that if it means keeping them out of landfill. They're 10mm bigger but they'll fit and look similar enough to the originals that it shouldn't look odd. While cheap, the magnets are actually bigger than the Kef/Audax ones so who knows, they might sound ok. I've seen them advertised as suitable replacements for the T27 in the LS3 5/A! Sounds like a stretch.

https://www.amazon.co.uk/dp/B000L9A4VK/?tag=pinkfishmedia-21
 
This site contains affiliate links for which pink fish media may be compensated.
Definitely Son Audax. I had a set way back. There are some large electrolytics actually in line with the bass driver to change the bass alignment which will need changing and could be awkward to get maybe... something like 680uF or 820uF IIRC but of course non polarised.
 
Exact unit is Audax HD 100 D 25 BA HR. Sensitivity is specified as 88.5dB (on axis for pink noise input of 1W).

From KEF, Coda 2 was rated 87dB.

hd100d25bahr.jpg
 
Exact unit is Audax HD 100 D 25 BA HR. Sensitivity is specified as 88.5dB

Perfect, thank you. The substitutes I'm looking at are 95db but I think I'll give them a shot. Can maybe get adjust the crossover if they're too bright, although I'm trying not to turn this into a project ;0)

Thank again.
 
You'll definitely need to pad the substitute tweeters down with a resistor in series. The only questions being, of what value and where in the circuit(?). Apparently, there are pros vs. cons to having the resistor before vs. after the high pass capacitor. I've no idea which would be superior here, but something to consider/look into.

Coda II crossovers are model SP2004/P100066. This PCB, with various components installed, was used for all of the KEF C-Series II 2-way models...
kef-coda-2-pair-of-crossover.jpg
 
Nope definitely Coda II. It wasn't on the crossover board but soldered to the bass driver terminals IIRC. I tried bypassing it so remember it well!
 
Nope definitely Coda II. It wasn't on the crossover board but soldered to the bass driver terminals IIRC. I tried bypassing it so remember it well!
Seems it's another case of; 'if all else fails, read the brochure'.

"Low-frequency output is maintained
nominally flat down to 65Hz with useful
output down to 50Hz. There is a higher
rate of attenuation below that frequency
to obviate the influence of unwanted
sub-sonic signals which are often
prevalent in simpler installations."​

I've never heard tell of rumble/warp filters being built into loudspeakers before. I suspect the large electrolytics you spoke of are in series with the bass/mid as 'after the fact' first-order 'high pass' filter, and perhaps could be usefully removed rather than replaced.

Come to think of it, with these being a fairly solid IB design, perhaps the bass extension was impinging upon that of the next model(s) up in the series.
 
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Seems it's another case of; 'if all else fails, read the brochure'.

"Low-frequency output is maintained
nominally flat down to 65Hz with useful
output down to 50Hz. There is a higher
rate of attenuation below that frequency
to obviate the influence of unwanted
sub-sonic signals which are often
prevalent in simpler installations."​

I've never heard tell of rumble/warp filters being built into loudspeakers before. I suspect the large electrolytics you spoke of are in series with the bass/mid as 'after the fact' first-order 'high pass' filter, and perhaps could be usefully removed rather than replaced.

Come to think of it, with these being a fairly solid IB design, perhaps the bass extension was impinging upon that of the next model(s) up in the series.

Another possibility is that it effects a bass alignment in which excess Q and bass output is countered by the 1st order roll off...
 
Thanks guys. I don't mind buying the tweets and adding a resistor if that's what it takes but I'm not interested in anything more involved. I'm not going to make any money on these, just saving them from the wheelie, but I'm not losing money on them or investing a lot of time. They're not worth it.
 
The large capacitor was there on the Coda 3 I had too. I also bypassed it, expecting to hear a massive improvement from getting a 'horrible bipolar electrolytic' out of the signal path. Blowed if I could hear any difference. Should have left it in circuit - I was using a Musical Fidelity A100 at the time - might have provided the necessary protection for the next time the amp blew up and went DC. Perhaps KEF, seeing the way the industry was going with all the hair-shirt designs, might have known better than a spotty teenager...
 
I got a substantial improvement in clarity and transparency by bypassing the big electrolytic, which I had originally presumed to there merely for some protection from people getting jiggy with the loudness control etc! It was a couple of years later when I realised there was method to their madness and so I unbypassed it and had another listen and found that although they did indeed become rather muddier the bass extension was somewhat improved.
 


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