Infinity Kappa 7 restoration...

[lgreen]

After many years, I've finally acquired a pair of Kappa 7. Yeah!

-Cabinets look brand new/ like the day they shipped.

- Woofers are in great shape/ have been replaced with original Infinity replacements.

-polydomes are awful, one is cracked.

-EMITs look new. Sound great.

First task- replace polydomes.

I could buy these on ebay but they would still be old and of unknown longetivity. So that does not seem like a good option.
Another option is a drop in new replacement/ substitute. But I am not sure that the substitute/ "replacements" are actually good. What's the general consensus on what to do about bad polydomes?

By substitute/ replacements I am referring to the 3" domes at Orange County Speaker Repair claimed to be drop in replacements-

http://www.speakerrepair.com/mm5/merchant.mvc?Screen=PROD&Store_Code=genem&Product_Code=02-239

Also, is the German site incorrect? The Technical Sheet on this page of Infinity-Classics.de shows that the Kappa 7 has a polygraph mid bass coupler 902-3068 (but also says it has a polydome). The the speaker actually has a polydome (right?). What is the part number? So it adds to the confusion on how to restore this part.

2nd task- EMITs- Is there any way to measure or test the EMITs to see if they are still up to spec?

Also, the Infinity web site appears to indicate that EMITs are still available.
Harmon Service Web Link. But the ordering system is messed up. Are these still available?

-thanks

 

[Tedrick]

After many years, I've finally acquired a pair of Kappa 7. Yeah!

-Cabinets look brand new/ like the day they shipped.

- Woofers are in great shape/ have been replaced with original Infinity replacements.

-polydomes are awful, one is cracked.

-EMITs look new. Sound great.

First task- replace polydomes.

I could buy these on ebay but they would still be old and of unknown longetivity. So that does not seem like a good option.
Another option is a drop in new replacement/ substitute. But I am not sure that the substitute/ "replacements" are actually good. What's the general consensus on what to do about bad polydomes?

By substitute/ replacements I am referring to the 3" domes at Orange County Speaker Repair claimed to be drop in replacements-

http://www.speakerrepair.com/mm5/merchant.mvc?Screen=PROD&Store_Code=genem&Product_Code=02-239

Also, is the German site incorrect? The Technical Sheet on this page of Infinity-Classics.de shows that the Kappa 7 has a polygraph mid bass coupler 902-3068 (but also says it has a polydome). The the speaker actually has a polydome (right?). What is the part number? So it adds to the confusion on how to restore this part.

2nd task- EMITs- Is there any way to measure or test the EMITs to see if they are still up to spec?

Also, the Infinity web site appears to indicate that EMITs are still available.
Harmon Service Web Link. But the ordering system is messed up. Are these still available?

-thanks

First, congrats on your acquisition, and welcome to the world of vintage Infinity's.

Now, to your questions:

1) The K7 uses the 3" Kappa Polydome, which is not the same as the original 2" Polydome used in the earlier RS series speakers (RS-IIIa/b, RS-4b, RS-5, RS-5b and RS-6b). The PN should be 902-3075. It is not a Polygraph mid-bass coupler (PN 902-3068).

2) If you plan to keep the speakers, I'd personally go with the Orange County Speaker Works replacement for the Kappa Polydome. It is a drop-in replacement, will work perfectly without any crossover modifications, and by all accounts is better sounding than the original. And you'll never have to worry about the diaphragm getting brittle and breaking.

3) To test the EMITs (or any other speaker) for funtionality, use a multimeter to check the impedance. The EMITs should test out between 3.4 to 3.7 ohms, but anything between about 2.9 and 4.5 ohms is okay.

4) There are no new EMITs available anywhere. You're only source is to buy them used off eBay. Just be sure to ask the seller to check the impedance. If they won't (or can't) and won't guarantee working condition, keep looking. There are tons of them out there, and most of them (except for the very early models, the supertweeters, and the High-energy models used in some of the IRS speakers) use the exact same tweeter diaphragm.

 

[lgreen]

Kappa 7 pictures

Thanks for the information.
I've ordered the pair OC polydome drop-in replacements.
Which by the way cost far more than the speakers themselves.

Here are the speakers with the polys somewhat unscrewed in preparation for replacement.

Left

Right

 

[lgreen]

Polydome replacements.

You would think a drop in part would be easy but it was a little tricky (first time I ever worked on a speaker). So here is what I did to replace the polydomes with the OC replacement domes.

Part 1:
-Put speaker flat on floor or table as you cannot work on it if it is upright (found out the hard way).
-Remove bolts holding in yellowed and cracked polydomes
-(Attempt to unsolder wires, but this just breaks the connectors.) So cut lead wires noting which is to the red (+) and to the other (-) terminal.
-Reterminate wires (solder) and lable with + and -

"drop" in speakers do not drop in (physically).

-Drill out the holes on the OC dome replacements with large drill bit (I used 7/32") because the hole pattern is right but the holes are too far towards the center of the part.

-Place a nail or small screw in each screw hole. The holes are impossible to see when the new black part is put onto the black felt so do this now and it will align the new part.

It looks like this. (Wow! That cabinet is THICK!)

 

[lgreen]

part 2

part 2:
- connect wire terminations to new speaker dome (red is +); solder in place
- insert new part over the nails/ screws.

 

[lgreen]

Part 3

Part 3: replace nails/ screws with original bolts. Just like a car tire, turn the opposite screws a little at at time till it is in there tightly.

Done!

 

[Sir.Byrd]

Nice work! How old are those woofers? You might want to check the foam surrounds on them just in case they are close to the point of decay. If they are less than 10 years old, crank them up and enjoy!

 

[Tedrick]

Looking good :yes:. And now to the fun part...how do they sound???

 

[lgreen]

Nice work! How old are those woofers? You might want to check the foam surrounds on them just in case they are close to the point of decay. If they are less than 10 years old, crank them up and enjoy!

The woofers were recently replaced with OEM woofers back when they were still available. They and the surrounds are absolutely pristine. And photos do not do justice to the cabinets and felt on the front face- I cannot find a blemish.

I've got a few DIY amplfiers over here (including Krell KSA50 clone), so I'm trying them out slowly with the different amps at various volume levels to get a handle on how tough of a load they present and which amp works best. If there is a way to measure impedance vs. frequency I'd like to hear it (have FG and scope).

I wish I could biamp them but they have only 1 set of terminals and its probably best to leave them as close to original as possible. I also wish I had room for them- too much gear!

The speakers sound very good; the bass is not as deep as I expected but it is solid and does not compress with volume; and the highs are crisp and airy. I am going to focus on the EMITs next and check their resistance, but they appear to have no problems- they can pull of delicate highs as well as screaming guitar. The new domes do sound very nice and I'm glad they were available. The speakers are true high end quality from a construction/ engineering and sound standpoint. The have quirks, right, but that is another characteristic of a high end product. I can confirm that a high current amp is the way to go, and toe-in is also important.

Because these are so old and the drivers do deterioate with time, these are available very cheaply now and will be cheaper in the future. They are vitually being given away. But they are so good and fixes are so available that you, as I did, have to pick them up when you see a pair.

If the EMITs hold up these should go another 20 years without a problem.

 

[bastek]

Great work for a 1st timer. So, which of the two pairs you prefer and why? Your other pair looks like a Dayton DIY to me.

 

[lgreen]

"Dayton DIY"???? what? Where? How?

The other pair in the photos are modern high end. I sold my WP 5.1 and bought these used when I "downgraded" from Goldmund/ BAT/ Cary/ Wilson/ SF. Fantastic speakers. They are Von Schweikert VR 4 Jr. Great in every way with good extension, high end and impact. Small footprint and easy impedance. Good looks matched woofer/tweeter extensions; look how the woodgrain extends from the woofer modules seamlessly to the tweeters. The Kappa's look retro in comparison.

Review 1, Review 2, Review 3

Without being snooty (and vastly overpriced) these go high and deep and are a relatively easy impedance. Amazing separation and imaging.

But to answer the question, I have not compared them yet, still listening to the Kappas, and loving it.

 

[bastek]

My mistake, these looked like Dayton woofers to me (nothing wrong with Dayton, many high end brands use them), and many diyers have speaker finishes that many mfgrs would envy.
So, how are the 7s coming along?

 

[lgreen]

Sorry, I read my post and it came across as snobbish. Didn't mean it that way and I totally lack the skills to make something looking like that! Anyway, we are at the same place- diy and classic components all the way.

 

[Mecca1953]

First, congrats on your acquisition, and welcome to the world of vintage Infinity's.

Now, to your questions:

1) The K7 uses the 3" Kappa Polydome, which is not the same as the original 2" Polydome used in the earlier RS series speakers (RS-IIIa/b, RS-4b, RS-5, RS-5b and RS-6b). The PN should be 902-3075. It is not a Polygraph mid-bass coupler (PN 902-3068).

2) If you plan to keep the speakers, I'd personally go with the Orange County Speaker Works replacement for the Kappa Polydome. It is a drop-in replacement, will work perfectly without any crossover modifications, and by all accounts is better sounding than the original. And you'll never have to worry about the diaphragm getting brittle and breaking.

3) To test the EMITs (or any other speaker) for funtionality, use a multimeter to check the impedance. The EMITs should test out between 3.4 to 3.7 ohms, but anything between about 2.9 and 4.5 ohms is okay.

4) There are no new EMITs available anywhere. You're only source is to buy them used off eBay. Just be sure to ask the seller to check the impedance. If they won't (or can't) and won't guarantee working condition, keep looking. There are tons of them out there, and most of them (except for the very early models, the supertweeters, and the High-energy models used in some of the IRS speakers) use the exact same tweeter diaphragm.

Hello Tedrick. I'm responding to a very old post. I just thought it might be interesting to note for future reference. I'm not sure what crossover schematic you are referring to, but attached is the actual Infinity schematic showing that they indeed used a Polygraph K dome mid bass coupler #902-3068. Now this is according to Rev A so it may be possible that during the run they could have changed the driver as mine have been replaced with reconditioned polydome k's. This is the only version of the schematic that I have found.

 

[seifreit]

Hello Tedrick. I'm responding to a very old post. I just thought it might be interesting to note for future reference. I'm not sure what crossover schematic you are referring to, but attached is the actual Infinity schematic showing that they indeed used a Polygraph K dome mid bass coupler #902-3068. Now this is according to Rev A so it may be possible that during the run they could have changed the driver as mine have been replaced with reconditioned polydome k's. This is the only version of the schematic that I have found.

This is one of the infamous, well documented "typos" that are riddled throughout the various Infinity Tech Sheets/Manuals. The RS 7 Kappa was never produced with a polygraph K driver. Most of the Tech Sheets/manuals were produced long after the referenced speakers were out of production.