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Infinity Kappa polydome

thymanst

thymanst

Minnesota morning
I figured I would start this thread as a info/repair replacement thread on the Infinity Kappa polydomes that are in so many models (Polydome K, RS Series, Kappa Series, RS6000, RS6000a, RS6 Kappa, RS7 Kappa, RS8 Kappa, Kappa RS 6, Kappa RS 7, Kappa RS 8, Kappa RS 9, Kappa 6.1, Kappa 7.1, Kappa 6.1i, Kappa 7.1i, RS Kappa 6.1 Series II, Kappa 7.1 Series II, Kappa 8.1 Series II, Kappa 9.1 Series II, Kappa 6.2i, Kappa 7.2i, Kappa 8.2i, Kappa 9.2i, and many more.) -

The original Polydome part # 902-3075, 902-5793 and the 751-3257 replacement diaphragm are all no longer being produced by Infinity (and probably never will again).

There is a Vifa 3" dome midrange (part # D75MX41) that is sold as a "drop in replacemnt" by several speaker repair companies. The Vifa fits perfectly and is the same size as the polydome, but it is a 6 ohm driver, where the original polydome is a 4 ohm driver -another difference is the polydome is "vented " in the back of th driver. (Kappa 9's have a rear port for the midrange that fires backward so the back vented polydome would have more sound going backward) - it also is a fabric diaphram where the polydome is a plastic.

here are the specs of the Vifa:
Precoated fabric diaphragm
Low moving mass
Internal ferrite magnet
Very linear impedance
Flange 152m3m
Cutout 120.7mm
Depth 31.5mm
Znom 8 ohm
Re 5.9 ohm
fs 350 Hz
Mms 3.1 g
Sd 55 cm2
BL 4.7 Tm
VC Ø 76 mm
Sensitivity 2.83V / 1m 92 dB
Nom. Power DIN 80 W
Magnet weight 240 g

I cannot find the specs for the Polydome and hopefully somone will contribute those -

another possibility I saw (elsewhere on the forum) was the Vifa/polydome combo driver - it looks like Millersound of PA. can put the Vifa diaphram on a polydome body - I took apart a bad polydome and can see how it could be done, by glueing the Vifa diaphram to the voice coil of the polydome and reassembling - I would think this would result in a 4 ohm version of the Vifa/polydome - how else it would change the sound charactoristics I dont know.....
 
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After playing around all morning with the Kappa 9's I've found that the Vifas "brighten" up the speakers quite a bit (I install a Vifa on one speaker and left the polydome in the other, then adjusting balance to compare) - the vocals sound more "live", but not in a really good way - I tried turning the db controls on the speakers back and it works to some degree, but at the loss of some sparkle on the upper end - it does seem to throw the balance of the speaker out somewhat also..... I ordered two Mills non-inductive resistors (2 ohm,12 watt) that I'm going to wire parallel before the Vifa driver and see if it calms the Vifa down and brings back the balance to the speaker - I was looking at a pair of Polydomes on the 'bay, but they are up over $200 with hours to still go......The pair went for $400 which is ........:jawdrop:
 
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Orange County Speaker Repair sells the "exact" replacement diaphram and drop-in driver for the 3" Kappa Polydome.
 
The "exact" replacement they have is the Vifa 3" dome midrange - I have one in front of me as I write - where the Infinity diaphram is says it has been replaced with the Vifa Driver unless you see somthing I dont.........If they had original parts I'd be more than happy....
 
I was looking at a pair of Polydomes on the 'bay, but they are up over $200 with hours to still go......The pair went for $400 which is ........:jawdrop:[/QUOTE]

Most domes go about $175 per pair....The only reason those sold for so much is because they still looked clear....Someone probably put a hairdryer on them prior to posting to clear them up. Not bad he got $200.00 extra for making them look newer.
 
yeah, the second pair went for $350+ - what I did was buy a pair of Kappa 6's ($280) and the guy is taking out the drivers and shipping to me - I'll have the two polydomes, two woofers and two emit k's for that price - it seems like the way to go with the crazy polydome prices........
 
thymanst said:
yeah, the second pair went for $350+ - what I did was buy a pair of Kappa 6's ($280) and the guy is taking out the drivers and shipping to me - I'll have the two polydomes, two woofers and two emit k's for that price - it seems like the way to go with the crazy polydome prices........
Click to expand...

Way to go....Although you hate to have to part out a nice set, it is cheaper to buy the whole speaker rather than its parts. The woofers wont work for you though ( another project perhaps ).
 
ordered two Mills non-inductive resistors (2 ohm,12 watt) that I'm going to wire parallel before the Vifa driver and see if it calms the Vifa down and brings back the balance of the speaker [/QUOTE]

Did you try the the resistors? I am curious to know the results. Thanks
 
ScooterDude said:
Seems like the Vifa part has been discontinued also. Scan-Speak is now making a replacement called the Discovery D7608/9200-10. Looks like the same unit.

Here is the link from Madisound: https://www.madisound.com/store/product_info.php?cPath=45_234_264&products_id=1088
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That's what I got for Christmas. I don't know if they are exactly like the Vifas. They sure do look like it. The Vifas are 6 ohms, Scan Speaks are 8 ohms and the Infinity originals are 4 ohm. I ordered an 12 watt 8 ohm resistor I will be putting in the scan speaks in next week. Next up will be to refoam the 12s. Once I'm all done, I will report back with my findings.
 
I have Kappa 8's since new and trying to keep them alive please keep this going,. I need the orginal 12" woofers and an trying to score a complete set of speakers 7-8-9 to keep them going.
 
Those Polydomes can be rebuilt/repaired by a friend here in Hong Kong. He is a professional speaker restorer, who basically does nothing all day except fix drivers (and sell some rare/nice speakers and some amps in between), and has been doing so for years. He is REALLY good at it! One or two AKers (besides myself) have had these domes rebuilt by him before, and posted about it here. The guy's contact information is in the threads here; search and ye shall find.

I think he charges a little over a hundred dollars (IIRC) apiece, plus shipping, to re-do these; you send him the drivers, he fixes them, and returns them to you. He individually hand-makes the replacement domes (!) to the exact dimensions as the originals. The main difference is the color; his are dark grey and not pale like the originals, as that color material apparently isn't available any more. The replacements are a close sonic match to the originals; much closer than the Vifas, since ONLY the dome part is not original; impedance and other characteristics are not changed, and no crossover mods are necessary. I've had him work on a bunch of different Infinity and other drivers (including those picky tinsel repairs on the Quantum series domes), and have always found his work very satisfactory. Just giving y'all an option, here.


Ah, found it! Here is the thread: http://www.audiokarma.org/forums/showthread.php?t=308268

Somewhere I have his email address, too. I'll try to find it, and come back and post it here.
 
I have good polydomes on my Kappa 9's, they're still clear and flexible. Is there anything I can do to keep them that way? can I apply any type of oil, or cleaner, or something? or no matter what I do, they'll become yellow and breakable?
 
There is a whole thread on this here: http://www.audiokarma.org/forums/showthread.php?t=358331&highlight=polydome

But remember if yours a brittle etc... already, I would be very careful if I did it. I have the 9.1 Series II so the drivers are much newer, so mine were no problem to do as they were not in that bad of shape. I plan on doing mine once a year with some conditioner, just to keep them pliable etc... I believe this will prolong their life tremendously. You just have to be careful, especially if they are already in pretty bad shape...

In the end, it is your own decision on what to do...
 
Augy said:
I was looking at a pair of Polydomes on the 'bay, but they are up over $200 with hours to still go......The pair went for $400 which is ........:jawdrop:
Click to expand...

Most domes go about $175 per pair....The only reason those sold for so much is because they still looked clear....Someone probably put a hairdryer on them prior to posting to clear them up. Not bad he got $200.00 extra for making them look newer.[/QUOTE]
Try contacting miller sound and talk to Bill. He is the best to fix a kappa polydomes.
 
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