KGeist

Sensitivity measurements are typically made at three meters and then converted to a one meter measurement (add 9.5 dB). You want to be in the farfield of the loudspeaker in order to be sure the drivers are aligned properly. The one meter measurement is simply a more convenient way to state sensitivity. Sensitivity in a "powered" subwoofer doesn't mean a lot in the traditional sense because the input is fed through the internal power amplifier. Subwoofer amplifiers are generally highly equalized and therefore one number doesn't easily apply. On the other hand, stating subwoofer output for a given line input does make some amount of sense. For example, for a 100 mV input at 40 Hz, the subwoofer will generate 90 dB under 1/2 space conditions. The only problem with this approach is that it doesn't reflect the efficiency of the loudspeaker because the amplifiers voltage gain (amplifier sensitivity) is now included in the measurement. Kerry

I don't believe I've ever seen a mathmatical solution for the resistance and reactance of a Tractrix horn (although I'm sure one exists). I've always "assumed" it was similiar to a Hyperbolic horn, given that the two curves are "somewhat" similiar. I have also seen actual acoustic resistance measurements on a Tractrix horn that supports this. BTW, our typical horn designs use a modified Tractrix horn curve. The mid-section of the horn is modified in order to give/maintain the desired horizontal and vertical coverage pattern (90X60 etc...). Pure Tractrix, Exponential and Hyperbolic horns become increasingly more directional with increasing frequency, and therefore are not suitable in systems that require good even coverage throughout its operating band. Kerry

If I'm not mistaken, I believe one of the problems with Alnico was that it is prone to demagnification. Kerry

Although I don't see any practical reason for doing it, you can lower the impedance of a loudspeaker by simply adding a step-up transformer. Transformers are used all the time in commercial loudspeakers. In these applications the impedance is raised such that multiple speakers (in parallel) can be driven by one amplifier. The technique works quite well for this purpose, but it does degrade the sound quality. Kerry

Boa, In a room, any measured dips in amplitude response are almost always due to some sort of cancellation and therefore it is not wise to try and EQ them out. Adding more energy at the problem frequency doesn't change anything except make your amplifier work a lot harder. With an equalizer, you can EQ the peaks, but its best to leave the dips alone. Kerry

A 70 Hz notch would correspond to the first null of a vertical standing wave where the ceiling height is approximately 8 Ft. Although this could be the source of the problem, it is probablity more likely to be due to interference effects between the speaker/receiver and subwoofer crossovers. In other words, the two crossover alignments are not "in sync" with one another throughout the crossover band. The exercise of moving the speakers around the room is probably helpful, and may be the only practicl option you have other than setting the speakers to full range. Kerry

I believe it is March 9th. Kerry BTW, you might want to check out http://www.mrspaulwklipsch.com/

This question has been covered in the past, so I'm not going to go in much detail here... Your problem is due to the fact that with the electronics "OFF", the main loudspeakers are acting like a microphone and feeding signal (noise) to the speaker level inputs on the subwoofer. This can cause feedback if the subwoofer is located to close to one of the main loudspeakers. There are two solutions. One is to simply position the subwoofer further away from the main speakers. The other is to use the line level inputs on the subwoofer. This takes the subwoofer out of the same signal path as the mains. Kerry

Although I would consider the midrange autoformer on the Khorn network board a form of "equalization", other than that, there are no circuits which are purely intended for that function. On the other hand, it must be remembered that filters come in an infinite variety of alignments (Butterworth, Bessel, etc...) and therefore can be used to equalize a system. About the only disadvantage of using equalization in this fashion it that the only areas where you have the latitude to equalize is confined to a relatively narrow band (about 1 octave) centered around the crossover point. Surprisingly enough though, this is also the area where drivers usually need the most help because they are typically at the extent of there usable bandwidth. The problem with using an electronic crossover is that although you may have different alignments programmed in the processor, it is very difficult, without exhaustive testing and listening, to determine which one to use. Kerry

The Kg3, Chorus and Forte do not have the Polyswitch. The Kg4 does, but I'm not sure if it had been added by 1986, or not. Kerry

Yes. The Polyswitch was used in many Klipsch designs starting in the mid 80's (I believe the Kg 4 was the first). It was used primarily with our standard one inch tweeter driver, but only in applications were more power demands would be placed on the tweeter. For example, the tweeter in the Kg 5.5 (with two 10" woofers) has to work harder than the tweeter in a Kg 1.5. Therefore some amount of tweeter protection is probably necessary on the 5.5, while the 1.5 gets along fine without it. The transition into ferrofluid in the early 90's lessoned the risk of tweeter damage, therefore, almost all our current consumer products (but probably not all) do not use it. Kerry

The Tangent series all have a tweeter protection device called a Polyswitch. The Polyswitch is placed in series with the tweeter and the resistance goes high, essentially shutting down the tweeter, when the average current reaches a certain level. This is a thermally activated device, therefore it resets itself once it has had a chance to cool-off. This would also explain why it is easier to activate the second time. I can't explain why it appears to be shutting down prematurely. I'm guessing, but it may be that the polyswitch is simply wearing out from multliple use. The best bet is to contact Klipsch Technical Support. Kerry

Believe it or not, you do have to be careful about lifting the woofer out of the circuit. Most Klipsch networks have 12 dB per octave slopes, or higher. This puts at least one inductor in series, and one capacitor to ground. If this circuit is not terminated properly, or is left open (no woofer connected), then it's a resonant circuit, resulting in a dead short somewhere in its passband. It will almost certainly trip the amplifier's protection circuit and could damage the amplifier. The easiest solution would be to remove the capacitor going to ground. It is usually the largest capacitor on the board (40 uf or higher/ 100 volt or higher) and therefore shouldn't be hard to identify. Kerry

I'm certainly no expert on vintage loudspeakers, but I remember when Klipsch first got this speaker. Some of these details may be a little shaky (give me a break, it was a long time ago), but here goes... The loudspeaker is an RCA cornerhorn that Klipsch obtained about 1987. I believe the horn is a cast multi-cellular horn with an RCA compression driver attached. I don't recall many details about the basshorn or its driver. When we first took possession of the loudspeaker we measured it in our anechoic chamber, but before that, we listened to it. I remember the power supply and amplifier that came with the speaker was still in good condition, and as I recall, we at least used the power supply to energize the field coils of the drivers. While we were setting up the speaker for the listening test, Paul Klipsch walked in, and as usual, was curious what we were doing. Of course, he recognized the loudspeaker and immediately became interested. During the listening test, Paul Klipsch took out a sheet of graph paper that we used to plot frequency response (this was before we made computer measurements), and with a pencil, drew the frequency response of the loudspeaker based on what he had heard. After a few minutes, we placed the louspeaker in the chamber, took the measurement, and I'll be damned if PWK hadn't nailed the shape of the frequency response curve. I still remember the frequency response to this day, huge suckout at 500 Hz, rolled off response above 4 KHz. Frankly, I thought the speaker sounded really bad. But to be fair, there's no assurance the loudspeaker was "in spec", and the rolled-off response above 4 KHz was typical of motion picture loudspeakers of that time. Kerry

0 dB is considered to be the threshold of hearing. However, it is an arbitrary value that, by itself, doesn't mean a whole lot. The reason for this is because the term decibel is used to describe a power "ratio" and therefore doesn't have any meaning unless it is referenced to something. For example, 10 dB doesn't tell you much other than the magnitude of diffence between two unknown quantites. OTOH, 10 dB referenced to 1 watt, is 10 watts. I point this out is because 0 dB Sound Pressure Level is referenced to .0002 dyn/cm2. But again, this is an arbitrary value that is considered, more or less, to be the threshold of hearing. However, it is interesting to note, under some circumstances and at some frequencies, very good ears (no doubt young ears) can hear negative levels of dB. Kerry