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Old 28th January 2009, 09:33 PM   #1
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Hi Folks,

An interesting project has come my way, and I wanted to garner some opinions. My father-in-law has asked me to repair (at his cost ) some speakers that have been languishing in the basement after being damaged. They are a pair of Infinity "Reference Standard 7 Kappa", a 3 way design with a ribbon/quasi ribbon tweeter (Emit K), 3" midrange "Polydome" and a 12" carbon composite woofer, mounted in a large sealed cabinet.

Unfortunately, one tweeter and one midrange driver are open circuit. I have been able to source replacement parts, albeit at quite a price, but my "customer" is insistant on repair. Further, the foam surrounds for the woofer have disintegrated, but I have located a repair kit to address this problem.

The question is, what can we expect from these speakers when I get them repaired? Do we have a classic or a clunker on our hands? The design, general construction and parts seem to be of high quality - in particular I hear very good things about the ribbon tweeter, but also that it is susceptible to damage from amp clipping - we have one blown tweeter already....

I'm looking forward to the first audition, but would love to know if anyone else has experience & views about this series of speakers,

Cheers,

Ed
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Old 28th January 2009, 11:26 PM   #2
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If your blowing drivers in this quantity then perhaps its time to buy something that will take more power.

It could be you do the repair then blow them up again.
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Old 28th January 2009, 11:57 PM   #3
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nigelwright7557 - there is no recurring problem here! I've never actually used these speakers and do not know much about them. They belong to my father in law who loaned them to a friend some years ago and were returned with damaged drivers. He knows my practical interest in audio equipment and asked if they could be repaired - I offered to take a look, find parts etc.

I explained the most likely cause of the damage and it's most unlikely that there will be any future abuses (or lending!) after the repair.

Cheers,

Ed
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Old 28th January 2009, 11:58 PM   #4
pjpoes is offline pjpoes  United States
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The emit tweeters are known to frequently need rebuilding. I rebuilt a pair of Infinity Quantum II's, which were what evolved into the Reference series.
Infinity vintage
As far as how good they were in their day, they were a decent speaker. Are they going to give you that vintage sound that make vintage JBL's, Klipsch, and Tannoy's so sought after? No, these were the beginning of a new way of building large reference speakers, and simply are not up to what many modern speakers could do. The Emit tweeter, while well thought of in it's day, is not really a great tweeter by today's standards.

The watkins woofer is ok, and I would recomend repairing it. I would recomend against replacing the drivers with anything but originals or rebuilt originals. You won't hear what these speakers were designed to do otherwise. You also won't end up with an Infinity speaker anymore, and chances are, your own concoction won't be very good either.

Be very careful in rebuilding the woofers. Small woofers are pretty easy to rebuild. Larger woofers like those Watkins woofers need to be very carefully centered. More than likely you won't be able to center the woofer with spacers, as I'm guessing removing the center cap would be too difficult without damaging the woofer. keep it as centered as possible while the glue drys, as this will cause major problems.

Replace the caps in the crossover with new ones. Given there age, they have likely drifted, and weren't that great of quality to begin with. The inductors are fine, I would leave them. Resistors are a mixed bag. I would look at those carefully and consider replacing them, but if they appear ok, then leave them. If it has a potentiometer for level adjustment I would replace this with a modern piece as well, as those frequently wear out and become noisy. The ones in mine were selector switches and discrete switches, this is a much better design, and I changed the resistors with new ones as the old ones had cracks in the ceramic.

Don't expect too much from these. If they were the Quantum line source, reference, or IRS I would think they would be cool, but the off shoot lower end reference models like the 7 just weren't quite as exciting. I do think they are worth repairing though.

Oh almost forgot, the tweeters can be rebuilt. Since not all EMIT tweeters were the same, I recomend rebuilding them, not replacing them. Unless you know the replacement emit's are from the exact same model, you may end up with a different tweeter that superficially looks the same.
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Old 29th January 2009, 12:27 AM   #5
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pjpoes,

Thanks for the in-depth reply - that is some very helpful info.

So far I have managed to source original parts for the tweeters but settled for Infinity's newer 3" dome midrange - a recommended replacement. That is something of a compromise, but the newer parts are said to be of very high quality. I chased some original midranges on Ebay, but they ran above my maximum.

The level potentiometers need attention, as you say, but might respond to cleaning, these things often do.

The woofers do give me the most concern, though I'm prepared to remove the dust caps (replacements on order, just in case) as this should be easy enough if I'm careful. I've read quite a few different methods to achieve accurate centering of the voicecoil and will try a few "dry runs" to see what works best.

I think at the end of it we'll recover a pretty good set of speakers for my father in-law's system. As for me, I'm sticking to the Maggies I just rebuilt

Cheers,

Ed
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Old 29th January 2009, 12:33 AM   #6
pjpoes is offline pjpoes  United States
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I get nervous replacing drivers with different drivers without changing the crossover. If you can take measurements, that helps. My ATB rig wasn't very expensive, and if all you need is a response, you can get that with some inexpensive RTA software or FFT software and a cheap measurement mic.

If you remove the dustcap, then use the recommended voicecoil spacers. Nothing works as well as a few carefully placed spacers.
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Old 2nd February 2009, 10:02 PM   #7
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Quick update:

Work is complete and the speakers are up and running again. Replacing the woofer surrounds was the most time consuming and labour intensive task, mostly due to the prep work involved in removing the old surrounds and glue residue. There were also instructions to glue the surrounds in two stages, meaning an overnight wait for glue to cure. Otherwise, some carefully arranged & sized card shims took care of voice coil centering without a hint of a problem. Replacing the other drivers was just a matter of fixing bolts and soldering.

Result - pretty good sounding speakers on first impression, and my father in law is happy again, which is the main thing. The substitute drivers do not seem out of place, but I don't yet have the means to make accurate response measurements.

All in all, a nice tidy project!

Cheers,

Ed
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