Insight

What you read on these 5 pages may give you some insight in the design if you are not a Kappa user, and in case you own similar Kappas, it may confirm your experiences. To others it can be of help to get more out of the systems. Only of course if the systems you bought do show significant irregularities. And only of course if you suspect that they have been tampered with. This write-up may also contain suggestions how to adjust the levels of mid range and high frequency drivers in the 7-A and also in other Infinity vintage systems like the larger Kappa 8 and Kappa 9, and maybe the arrays of drivers of an IRS.

Complexity

There is talk about Infinity Kappa 7 loudspeakers on the net. Most owners seem to love these speakers. Yet there are a few who are not satisfied with the performance. In fora people write that they do not have the right power amplifier. Or that the mid band is insufficient and not open. There is never talk about addressing the main problem, namely the adjustments of mid and high frequency units in relation to each other and in relation to the 12 inch woofer housed in the closed, damped cabinet. Yes, I have found too that the adjustments are related to the power amplifier you use. The importance of the power amp is real. But it becomes less urgent if the damping of the cabinet and the levels have been optimized. There is reason to believe that a few owners are not aware of how to make the best out of the design. Well, as many certainly know, it is possible to make them sound right if they do not. But you really have to work on them and take your time.

Normalcy

Normalcy is that you buy a loudspeaker system which has a frequency characteristic, a dynamic behaviour, and a certain level of efficiency, all determined by the designer. He has chosen the size and shape of the cabinet, the volume of the compartment for the woofer and the dampening of it, and how the woofer should be followed by the mid range and tweeter drivers. Normalcy is that there is no possibility to adjust the system by means of variable resistors, potentiometers or L-pads. With most speakers the only parameters that can be changed are those of the position in the listening room and the acoustic properties of the listening environment which can be altered in relation to the speaker systems. Yes, the designer may take various room characteristics into account and calculate the behaviour accordingly. He will most certainly test his design in a reverberant room and in a sufficiently damped room as well. He has to be aware of reflective walls and take rooms with different shapes and sizes into account. His aim is that his design shall function in as many rooms as possible. He wants to sell numbers! Not just a few speakers. Only in rare cases there may be an L-Pad or potentiometer for adjusting the level of the tweeter, or - like in the Yamaha NS-1000 and similar speakers - by means of a level switch with teo or three positions. Being able to adjust the levels has its drawback. By changing levels not only the crossover frequency changes, but also there is an influence on the phase of the system.

Lower Register

Although the designer will aim at a natural sound and if possible at a linear frequency curve, every "fixed system" will have its own particular character.
Fact is that the way the low frequencies are being reproduced will determine the behaviour of the mid and high frequency units. And since rooms differ, the behaviour of the woofer will hardly ever be predictable. Moreso, a closed box, a horn loaded cabinet, a ported system and a labyrinth, all do perform differently. Because of the different techniques applied, they all give different low frequency reproduction as regards to linearity, sound pressure, and detail, but most of all in relation to phase.
A labyrinth will give a more mellow lower register and therefore the mids and highs tend to be smooth too. The advantage of a ported system is that it is fast, much faster than a closed box and of course faster than a labyrinth. A ported system can provide a solid base for the rest of the spectrum only if the cabinet will have a carefully calculated volume which will be as small as possibly can be, and only then a lumpy bass will be avoided. The nasty thing about a ported system and a labyinth is that they easily show a phase shift somewhere in the region of 60 to 70 Hz. The best designed ported and labyrinth systems show the least audible phase shift. A horn like the Klipschorn and also a closed cabinet will provide the basis for the best low frequency characteristic. Of course the dimensions of the horn have to be calculated carefully. And the volume of a closed cabinet needs to be calculated in order to attain a perfect Q.

Closed Box

The drawback of a closed box is that the woofer should have a powerful magnet in the first place. Depending on the efficiency of the unit, and the size of the cone, you do need a powerful amplifier to drive such a woofer as much of the energy will be absorbed in the damped box. It is therefore easier to configure a nice sounding reflex loudspeaker system. There is less need for quality components. Even small and cheap units in little boxes will do the trick.

Three Units in Phase

What I found attractive about the Kappa 7 A, and what was my main reason for purchasing, was the closed woofer cabinet. That promised good phase in the lower register and this would certainly be repeated by the mid and high frequency units.
Both the true hobbyist and the avid seaker for the perfect reproduction has heard many systems during demonstrations in high end shops and at audio fairs. You may remember an instance when you were struck by a perfect demonstration. That must have been a pivotal experience. As a kid in fifth grade I heard the Philips 9710M. They were housed in the famous corner enclosure of the nineteen fifties, complemented by two mid high units hanging on the wall on the left and the right of the large cabinet. The system was fed by a valve amplifier. The records were played on a luxurious Philips record changer. It was the audio set of one of my teachers. In fact the box had the 9710AM, the 800 Ohm version, fed by the Philips OTL amplifier which was later picked up by Futterman. Like the 9710M, the 9710AM was a wide range unit with a whizzer (small center cone). I myself had at one time small wide range Philips units driven by a tube amplifier. These AD3800M speakers performed so very well, that, when I heard early Goodmans boxes with 12 inch woofers topped by a small midrange and tweeter, I found that the sound was not right. I was used to coherent phase even if the linearity of the 9710AM and the AD3800M in their respective cabinets were not flawless, yet the phase was correct! I discovered that perfect phase (coherency) is far more important than a straight frequency curve.