Infinity RS 7 Kappa restoration

[leesonic]

I finally started working on my Infinity RS 7 Kappa speakers last week, and thought I would post some pictures of my progress.

Here they are when I first bought them, three years ago. The first picture was taken in the Goodwill shopping cart. The second picture was when I got them home, next to some equally ropey Cerwin Vega speakers with car subwoofers.

 

[leesonic]

Cabinets

The cabinets are in pretty good shape, except for a bad water stain on one side, I wonder how I will be able to remove this? There is a thread on here somewhere about removing water rings from the top of speakers, maybe the same technique would work here? The particleboard risers on the bottom are pretty rough, but I will probably take these off anyway when I refinish the cabinets. Those type risers make it hard to slide the cabinets across carpet, with just a flat bottom base, it's easier. I will probably use some short stands to get them to the correct height again.



One thing I found with the cabinets though. If you rapped you knuckle on the side (and not just the water damaged side), the noise sounds different. If you put your hand inside and feel the join, you can almost feel it flexing, as the glue has probably let go. I glued in some pieces of quarter round molding, just like I did with my KEF 104aBs. This is a view inside the cabinet.

 

[leesonic]

Woofers

I LOVE working with these Infinity IMG woofers. I've never restored any Pioneer graphite woofers, but I know there are supposed to be super fragile. If you so much as breathe on them wrong, the cones crack and you're screwed. Not so with these IMG woofers. You can bend the cones almost any way you want, and you can use Goof-Off to remove the old glue residue.

The dust caps were squashed and disintegrating, so I took them off and shimmed the voice coils. Maybe that was for the best, because the gap is really small. The Infinity dust caps I got from Tom at my audio addiction are double layed, cloth mesh on the inside and foam on the outside.

 

[leesonic]

Dust caps on

 

[leesonic]

Abortive Polydome Repair

Rather than describe each picture in turn, since this didn't work out, I'm just going to describe what I did.

I carefully desoldered the lead-out wires from the terminals, although maybe not as carefully as I thought. The four screws were removed, which lets you separate the magnet, the sub assembly with the coil and dome remains on, and the front plate. I removed the surround and the remains of the dome from the sub assembly plate, then removed the remains of the surround from the voice coil. Once the coil was clean, I inserted it back into the magnet gap, and shimmed it to keep it aligned. Next, I took a small foam surround, and after cutting it to the correct internal diameter, glued this on the voice coil, making sure I didn't use too much glue. When the surround had dried, I removed the shims, and glued a cut down poly dust cap on the the surround. The result was, it looks beautiful, but measures 40 ohms now, and you can barely hear anything coming out of it...

 

[leesonic]

HiVi dome midranges

@swechsler has an excellent thread here on replacements for the Infinity Polydome Midranges. I decided to order a pair of the HiVi DMB-A 2" fabric dome midranges from Parts Express. If I hadn't wrecked one of my Polydomes, I could have got them rebuilt professionally. It's an expensive option, but seeing how it took me about 4 hours to do the mess in the thread above, it seems worth every penny because it's very time consuming.

The dimensions for the HiVi domes are on the web site, but nothing prepares you for when you actually get them. The domes are smaller, true, but these drivers are heavy and very nicely made. Here they are compared to the Polydomes.

 

[swechsler]

I think your mistake may have been desoldering the voice coil leads from the frame. I don't think that's technically necessary for this sort of work. I started sizing up doing something similar, and I took some pictures of the potential foam surround to use (I think I posted the pics here, but I don't remember the thread title). I may order some foam dust caps and try again, though.

 

[jazzmans]

Dust caps on

View attachment 1940389

View attachment 1940390

Is that the same dust cap Millersound uses for the polydome repair?

Looks good.

 

[BrianLW]

Is that the same dust cap Millersound uses for the polydome repair?

Looks good.

Looks like the same source, but the other size.

Pic is my woofer with SimplySpeakers large dust cap, along with my Millersound rebuilt polydome.

 

[leesonic]

I think I got mine from Tom at myaudioaddition. They are nicely made, cloth on the inside, and foam on the outsite.

 

[leesonic]

Crossovers

These crossovers have pretty big terminal plates, and you can sort of see why. A big circuit board and two L-pads.





Getting to the backs of the boards is relatively easy. Just remove the four retaining screws, desolder the wires from the 3.0mH inductor and the terminal posts, bend the tabs up on that inductor, and carefully lift the board up.



Recapped with Erse Audio electrolytics

 

[leesonic]

Got these back together today. I must have measured the new midranges about 10 times before drilling to make sure I got the holes lined up and symmetrical. I didn't want my speakers to make a guest appearance on the "speakers with questionable upgrades thread". I also agonized over the placement of the dust caps on the woofers. So many of these Infinity refoams where the dust caps are replaced, the Infinity logo is put on "flat". But if you compare it to the tweeter, or indeed how Infinity have their logo in the advertisements and brochures, you'll see that the logo is rotated. Maybe that's how the Infinity symbol is supposed to be after all?

 

[swechsler]

OK, I'm dying to know, how did the HiVi midranges work out?

 

[Bkphoto]

Usually not very well....no one has found a replacement that is as good as the original redone by Millersound....

 

[swechsler]

Usually not very well....no one has found a replacement that is as good as the original redone by Millersound....

That's why I asked, to my knowledge, @leesonic is the first to try those in the Kappas.

 

[Bkphoto]

Many people have tried the bigger ones....no one has seemed to stay with them unless the were purchased already swapped....then you don’t have any way to test without spending a good chunk of change...they are expensive...

 

[swechsler]

Yes, I know.

 

[Bkphoto]

Haha haha, I see that....

 

[leesonic]

Preliminary listening they sound good. "Preliminary listening" was me listening to my one song with a saxophone solo** to see if the midrange sounded harsh, before going to do other things in my house leaving the music playing in the background. I have the two level controls set midway, which isn't the normal position as indicated on the crossovers.

It's easy for people to say "they won't sound as good" without even hearing them. Will they sound as good as the original Polydomes, who knows? I chose a driver and drilled holes in the cabinet in such as way so as in the future, the Infinity polydomes will still fit.

 

[swechsler]

@leesonic I assume you don't have any other Kappas to compare with? I'll wait for a more comprehensive review from you, if they still sound good I may buy a pair to compare with my intact Polydomes.

ETA: if they're rotated correctly, can you get two holes in the HiVi frames to line up with two original holes from the Polydomes?