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Old 4th December 2013, 04:19 PM   #1
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Default Infinity 8 Kappa Rescue Project

I just picked up a pair of 8 Kappa speakers from my local consignment shop for $50.00. Cabinets and grilles in great shape.

All voice coils check good, but the Polydome mids need need new domes and the 12" woofers are non standard cheepos. All tweeters and mids are very clean.

Anyone know where I can source suitable replacement domes(plastic only)? I fancy my hand at trying to rebuild them before replacing them with non-standard drivers.
I thought maybe a voice coil dust cap if nothing else, might work.

Cheers
Peter
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Old 4th December 2013, 07:02 PM   #2
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Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
In your instance it would seem you really have just two ways you can go here. 1) Rebuild/Restore you Infinities to original condition.....there are drivers popping up on Ebay all the time to bring your Kappas back to original......however these Infinities and other models are NOTORIOUS for eating amplifiers....drawing immense amounts of current & melting down amps.....even when bi-amped. The funky plastic mid-domes seem to suffer from 'exposure', decompose & crack...there are no simple common or easy repairs possible. The entire units need to be replaced with one that is NOT cracked...but could crack on you two weeks after you spent six months chasing one down..The second choice would be to design a nice three-way within your fixed cabinet volume....it can be done, rather straightforward.


__________________________________________________ ___Rick......

Last edited by Richard Ellis; 4th December 2013 at 07:03 PM. Reason: typos
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Old 4th December 2013, 09:42 PM   #3
halo71 is offline halo71  United States
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I would only replace drivers with what are supposed to be there if I were you. Kappa's are great speakers! Known to be amp killers though, although the later .1 series (Kappa 8.1) are easier on amps.

I am not 100% positive but I think those Polydomes are fairly rare these days and hard to come by. Check the Infinity forum at Audiokarma.com. I believe there is a thread somewhere there about a guy, I think in China, that sells replacement diaphragms for that mid.
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Old 4th December 2013, 10:39 PM   #4
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I have never heard an Infinity Kappa and I bought these to play with and to hear why they are highly regarded(at least, by some). All of my speakers are DIY jobbbies, and this one may wind up having alternative drivers installed, since I have small supply of woofers, etc.
I assume the amp melting problem is associated with the woofer circuit, and I am thinking of bypassing that circuit and use a couple of subwoofer plate amps with Dayton drivers that I already have- just to get them up and running.
The poly midrange replacement may be a problem. I have one Dayton 2" mid to try, but have no idea how it compares sonically to the original polydome- and that is where the essence of the music lies.
Next step - check out the crossovers.
Thanks for the comments.
Peter
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Old 5th December 2013, 12:06 AM   #5
msb64 is offline msb64  Canada
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The Kappa 8s and 9s as well as any of the higher Infinity models were hard on amps that couldn't handle low impedances (as low as 2 ohms).
I personally have powered them with various Haflers, Thresholds and even a Class D amp, and my buddy has Parasound amps that also work well with those.
I still have a set of 8s in Santos, instead of the usual Oak, and they are one of my all time favorite speakers, even more than the 9s (buddy has 8s and 9s).
If you can get oem replacement drivers for them, it would be worth it as they are nice speakers.
Good deal on those, I paid over $3000 Cdn for mine back in the late 80s.
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Old 9th December 2013, 06:04 PM   #6
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Default Kappa 8 midrange

Anyone know the sensitivity rating of the 3" polydome?
I have a couple of 3 " drivers in my collection to try out to evaluate the Kappas.
One is the Tang Band bamboo cone 86db- the other is Dayton 2" dome 89db.
Still evaluating polydome repair or replacement.
Santa is bringing me the proper woofers.
Peter
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Old 9th December 2013, 06:46 PM   #7
msb64 is offline msb64  Canada
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Hi Peter, not sure if you have seen this or not, but here it is in case you haven't.
http://www.infinity-classics.de/tech...ical_sheet.pdf
The site has lots of good Infinity speaker specs, photos, schematics etc.
It is German, but it has a lot of english content on it, for everything else, you can use an online German to English translator.
Good Infinity pics as well on (late) Bobby Shreds site and Davids Audio.
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Old 9th December 2013, 06:46 PM   #8
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Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Problem is, with the bamboo cone, you would have to build a sub-enclosure & you'll wind up butchering the larger enclosure to "install" the sub-enclosure. so that's a non-starter. The two inch dome might not reach down far enough (roll off) to match-up with the woofer. There is an exact replacement thru Orange County Speaker for the dome...at $130, then there is the Tang-band 3" mid dome..at $135.....that TB dome runs at 90Db....I'd bet that is a high enough sensitivity.
Try your 2"....listen carefully for any frequency drop-outs, esp on the bottom end as it crosses to your woofer/s.

Thank-you Santa!

__________________________________________________ __Rick....

Last edited by Richard Ellis; 9th December 2013 at 06:47 PM. Reason: typo
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Old 9th December 2013, 07:18 PM   #9
msb64 is offline msb64  Canada
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If you click on the Kappa 8 link, it shows the model in Oak & Santos:
Infinity Kappa Serie
There is a 2 page testing results and review from Hirsch-Houck Labs at the bottom of the page, that may have some information you can use.
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Old 9th December 2013, 08:27 PM   #10
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Thank you Guys....
Some good info there.
Richard, the midrange drivers have separate enclosures already, so the 3" TB may work.
I really like the presentation of them, so I'll give them a try. This to me, is the fun part of DIY. I only wish that I had a decent polydome to compare.
I certainly don't intend to butcher the cabinets.
Peter
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