Kappa's are awesome speakers, especially the Kappa 8 and 9. They definitely qualify as audiophile (whatever that is
).
The K8 is the original model. It is a 4-way sealed-box (acoustic suspension) design with a rear-firing EMIT tweeter. Specs are as follows:
Introduced: 1987
Dimensions: 120 x 51 x 20 cm
Bass: 1 x 30 cm
Mids: 1 x Kappa-Polygraph, 1 x Kappa-Polydome
Highs: 2 x EMIT (one on the back)
Suggested for amplifiers with: 50-250 Watts per channel
Frequency range: 33 Hz - 45 kHz
Crossover frequencies: 90 Hz, 700 Hz, 5000 Hz
Suggested price (pair): 1998 $
Here's a photo:
The K8 is one of Infinity's famous 'amp killers' due to its sealed box design and crossover architecture, which resulted in a very difficult impedance curve that dips down to 2 ohms in some regions. These speakers are very demanding, and require a serious amp that is capable of producing prodigious quantities of current into that 2-ohm load. Amps with these capabilities are usually heavy, hot, and quite expensive.
The K8.1 was the next generation of the Kappa speakers. It is also a 4-way design, but is quite different from the original K8 in most other aspects. The cabinet for the K8.1 has a very different profile and is a tuned-port design (the port is on the rear). The K8.1's tweeters are the newer round EMIT (EMIT-r). The K8.1 also eliminates the rear-firing tweeter, and uses a cone mid-bass coupler in place of the original's Polygraph dome driver. Here's some specs for the K8.1:
Introduced: 1992
Dimensions: 123 x 43 x 30 cm
Bass: 1 x 30 cm
Mids: 1 x Midbass Coupler, 1 x Polydome
Highs: 1 x EMIT-R
Suggested for amplifiers with: 40-300 Watts per channel
Frequency range: 32Hz - 35 kHz
Crossover frequencies: 180 Hz, 700 Hz, 4700 Hz
Suggested price (pair): $ 2200
Here's a photo of the K8.1
Due to the ported design, the K8.1 is MUCH easier to drive than the original, so one need not spend quite as much on amplification (though these speakers will still benefit from using good quality gear).
Sound-wise, both are very good speakers that image well. Some feel that the bass from the tuned port K8.1 is not quite as fast,tight, articulate, or visceral (that kick-in-the-stomach feeling) as the original K8. The improved cabinet profile of the 8.1 probably reduced some cabinet-related distortion and improved imaging, which may offset the removal of the rear-firing tweeter. I think either speaker would be very enjoyable, but as always, if you can listen first with familiar program material and make your own judgements, you will come out ahead. Just be aware that if you go with the K8, you can't skimp on amplification.
