KGeist

Spider124, Off-hand, I don't know the sensitivities of the K-105 or K-1038, but I probably can add some clarity to this issue. First, the way we measure loudspeaker sensitivity is not as you suggest. We measure the speaker at 3 meters, full space, in our anechoic chamber. We measure at 3 meter because this gets into the far field of the loudspeaker. Generally, we use bandlimited pink noise to make the measurement, but in our experience, this isn't always necessary to get an accurate result. The 3 meter measurement is converted to a 1 meter rating using the inverse square law (in other words, add about 9 db). From here we add a 4 dB for "room gain". This is a figure we add that represents the output gained from a typical listening environment. It is an approximation, but it does reflect a more accurate sensitivity measurement of the loudspeaker/room combination. Therefore, this measurement reflects a value that the average consumer "might" measure at one meter in their own listening room. From this information, if the RF-3 is spec'd at 98 dB, then the spec without "room gain" would be 94. One woofer, as you suggest, would be 6 dB less, or 88 dB. However you must remember that this is with a passive network, and that the raw driver output may be 1 or 2 dB higher. In any case, 89 or 90 dB would be a good figure of merit to use. The horn sensitivity is much harder to determine. This is because horn loaded tweeters do not have flat pass-band responses. They are resistance controlled devices, and do not play by the same rules as direct radiators. Typically they have a 6 dB/Oct roll-off above the mass break point of the diaphragm, and as a result, one sensitivity figure is hard to establish. This characteristic of horns is taken care of in the design of the passive crossover, but in order to design it properly you have to be able to measure it. This isn't going to be easy in your situation, so I don't know what to tell you. Lastly, loudspeaker sensitivity and efficiency are only "loosely" associated with one another. They are NOT the same thing. I'm pointing this out because at some points in this thread the two were being clearly confused. For example, at low frequencies, adding a second woofer, in parallel, increases the sensitivity 6 dB, but the efficiency actually only increases by 3 dB. This is because when you place two woofer in parallel, you halve the impedance, and the amplifier delivers twice as much power, or 3 dB. So, the sensitivity at constant voltage would go up 6 dB (2 watts), but the sensitivity at "1 watt" would only increase by 3. Hope this help. Kerry

With regard to the 180 degree phase difference from second order crossovers... When designing crossovers for speakers such as the Cornwall, you must also take into consideration the phase characteristics of the drivers themselves. In the case of the Cornwall, you have a mass controlled woofer and a resistance controlled midrange horn, therefore, there exist a 90 degree difference between the two. When coupled to a second order network, this results in a net 90 degree phase relationship. This is a really simplified example since the phase characteristics of the individual drivers is quite a bit more complex than this. But it should at least help illustrate the point that the phase characteristics of the drivers must be considered when designing networks. Kerry

Shock-Late, There is nothing necessarily wrong with the LF horns arranged as you have them. You have essentially replaced a wall with another loudspeaker...a fairly even trade. One concern worth noting is that the subwoofer, as shown in your drawing, is located in the center of the room. This isn't the most ideal position for a subwoofer. Another option would be to place the two subwoofers laterally (stage monitor like) at the junction of the floor and back wall. We have used the LF horn in this position with good results. BTW, a corner has two different functions as applied to the Klipschorn. First, it provides a surface that is required to complete the low frequency horn itself. This is basically what is being provided with a false corner. And second, a corner provides the most efficient means to radiate sound, and is the boundary condition in which the Klipschorn was designed around in order to maximize its operation. You don't have to put it in a corner if maximum performance isn't desired, but it is essential that the LF horn is complete through the use of a false corner (or equivalent). Kerry

Gil, Volume scales with the cube of linear dimension, therefore a 34% (66% scale) reduction in linear dimension translates to 71% reduction in internal volume (.66x.66x.66=.29). This, most importantly, applies to back air chambers and would suggests that an appropriate woofer would have approximately 1/4 the Vas of the La Scala woofer (K-33-E). BTW, area scales with the square of linear dimension, In this case, areas such as horn throat and mouth area are reduced by 56% (.66x.66=.44). Kerry

I could be mistaken, but I believe that (horn) flare rate scales with linear dimension. Therefore a 20% reduction in size would translate to a 20% higher cut-off. Assuming that the La Scala flare is around 55 Hz (I'm guessing, but this should be about right), a 20% smaller enclosure would be about 69 Hz. Kerry

Tony, I've tested prototype La Scala's with wedges positioned as you suggest. It does increase the bandwidth of the speaker by a couple of hundred Hertz, but the amplitude response above 400 Hz was pretty choppy (very narrow 6-10 dB dips if I remember correctly). I believe we tried more than one size wedge, but I don't remember the difference it made. We abandoned the idea after we realized the response wasn't as smooth as we would like. However, we were also concerned about the bass-horns dispersion characteristics above 400 Hz. At these frequencies, the horn is beginning to get fairly narrow. I suspect some of this is due to the bifurcated horn section. I don't want to discourage you from trying this because we probably didn't explore it as thoroughly as we should have. Extending the bandwidth of the bass-horn in order to relieve some of the burden on the midrange may more than offset some of the problems I describe above.

Regarding the Karlson enclosure reference, you might be interested to know that it was the Karlson design that was primarily responsible for giving Klipsch its company motto. I'm sure most of you know what that is, right? You wouldn't be diehard Klipsch fans if you didn't.