Installing a pair of Second Hand Infinity Kappa 7A Loudspeakers.

Some may consider that the publication of this article comes quite late and should have been done some 25 years ago, in 1987, the year when the Kappa 7s were introduced or a year or two later after they had evolved to 7 A. Although I was publishing a critical audio magazine at the time, I never had the chance to review Infinity loudspeaker systems despite the fact that I had heard big IRS systems.
I am only writing about my experiences now, October 2011, about my thoughts and analysis of the Kappa 7A. Why? Because I bought a second hand pair in April of 2011 and would not have written anything if, after connecting and positioning the cabinets everything was Ok. But it was clear that "just connecting" did not suffice.

Trouble in the House!

The pair was bought from a firm in Germany from whom I had bought equipment in the past and those purchases were without complication. After the Kappas had arrived and the packaging of cardboard and all sorts of fillers to prevent damage were removed, I gave them a few days rest in the small and narrow hall so they could relax and adept to the new climate. After a week I was in the mood to move my old cabinets and connect the 7 A speaker systems. Now was the big moment to enjoy the sound as I remembered hearing it in a shop in 1995.

Ill Performance

Alas! The sound was not at all what I had expected it to be and certainly was not what I should have been hearing. In fact it was a big disappointment! The mids sounded edgy, the highs were fierce, and the woofers did not perform well.
First, it was immediately evident that the voice coil of the woofer of the cabinet which I had placed at left, was not well centered and scratched inside the gap of pole plate and magnet. The advertisement of the seller had stated "new roll surround". Probably the company that sold the speakers to me had ordered an inexperienced worker to glue the surrounds and the boss did not check the result of his work adequately. When I contacted the German firm in a polite manner and explained what was the case, the only thing they could do was holler! So that was a dead end. Furthermore the wooden pannels of the cabinets vibrated. Not just slightly, but excessively. That meant that there was fundamentally someththing wrong. The heavy vibration meant that the woofer did not "use" the entire volume of the compartment and the excursion was obstructed. This vibration interfered with the functioning of the Polydome and the EMIT naturally.

Further Discoveries

Careful listening made it clear that the woofer in the left cabinet had quite a different sound if compared to the woofer in the other system. It appeared that the woofer of the system with the repaired woofer had been connected out of phase, the polarity had been reversed. In order to confirm this, I connected a 1,5 Volt C battery to the binding posts. The woofer of the left system exerted out of phase. The battery made the cone move inwards, let it inhale so to speak, while the piston action had to be forward. The woofer of the other system was connected correctly, in phase.

In order to use the scratching woofer, I needed a new foam roll surround. When it arrived I followed the instructions found on YouTube. Also the dustcap did not look well centered. So I cut it out. Under the dustcap was a circuit used in case the woofer was mounted in an active Motional Feedback system. Of course the circuit was not used in the Kappa 7 A.

I wanted to replace that woofer and fortunately a seller on www.eBay.de sold a single woofer of the same design (902 3054A 391) and for an affordable amount. A few days later the woofer arrived and was installed, in phase naturally, and it performed as it should, without the scratching of the voice coil.

New 12 inch Woofer

But there was more. While checking the systems for polarity and replacing the woofer, I had noticed that the way the dampening material (Bonded Acetate Fiber - BAF) was arranged in the cabinets differed from speaker to speaker. The left cabinet had room behind the woofer while in the right cabinet the BAF was closer to the basket of the woofer. Checking www.infinity-classics.de once more I saw a picture showing that the B.A.F. should be as close to the basket as posxsible. It was originally separated by a mesh fabric (netting). The assistant of the German firm from which I bought the Kappas, obviously had pressed the BAF to the back of the cabinet with a firm hand in order to easily handle the internal wires leading from the filter to the woofer with the new roll surround that wanted tgo instal. But his arrangement gave incorrect results. It affected the frequency characteristic drastically. There was no correct transition between woofer and Polydome. There obviously was a gap. The first thing to do was to pull the BAF towards the opening. Hopefully this meant that the performance of both woofers became identical again.