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

Hurling a fully loaded Forte' off a loading dock is neat, but power testing a speaker to destruction...now that's cool!!! "If you wanna make a loudspeaker, you gotta blow a few woofers." Kerry

I'm sorry, I meant 10 and 12" woofers. But the comparison is still the same, a 12" woofer has approx. 50% more area than a 10. I have to be careful here because I'm making generalizations that can quickly fall apart as soon as other variables are added in. But here goes... The efficiency gain of the KLF 30 is essentially a combination of a larger magnet, and most importantly, a larger cone. In the case of the KLF 10 and 20, the 20 gets its additional efficiency from just a larger magnet. Both of these techniques try to accomplish the same thing, and that is to move more air. But at low frequencies the pressure build-up inside the cabinet will inhibit this and thus decrease low end performance relative to its midband efficiency. In other words, the cabinet is controlling the cones movement at low frequencies and therefore is the controlling factor of its cut-off frequency. As effiency increases there has to be a corresponding increase in cabinet volume in order to maintain the same cut-off frequency. With small 6 1/2 and 8" drivers, a proportional increase in cabinet volume is easily tolerable. But when you get up to the size of 12 and 15" woofers the proportional increse in cabinet volume makes a significant difference in cabinet size and only so much of that is tolerable. Kerry

boa12, Generally speaking, increasing efficiency by increasing the driver area requires the box volume to increase proportionally. The surface area of a 15" woofer is 50% larger than a 12 and therefore would ideally require an enclosure 50% larger than a KLF 20. An enclosure this large would probably not be accepted by "most" consumers and therefore some compromises had to be made. As a result, the KLF 30 is only about 25% larger than the 20. This circumstance is not unusual in the Klipsch line. The Forte' went lower than a Chorus for essentially the same reason. BTW, the Cornwall could be considered an example of an enclosure where this compromise was not made. Kerry

On a tanget, I honestly don't see the need for 6.1 surround (at least not with Klipsch drivers). My KG5.5s, just in stereo mode, setup such a good soundstage that it often sounds like I have a center channel playing! Yes, but only true along the axis of symmetry between the two loudspeakers. Move off to one side and this effect disappears (It also dimminishes with distance). For this reason, it has been said that stereo is an "antisocial" medium (only one person can really enjoy it). A center channel stabilizes the center image so that more than one person can enjoy an accurate sound field. This is also true of the surround speakers and is the primary force driving 6.1. A Multi-channel system simply provides more points from which sound can be made to appear. The stereo effect in multi-channel formats can, and is, still used effectively to position sounds at points other than the speakers. Kerry

Following up on Ray's point... A speaker's bass extension is only relavent with respect to that speakers overall sensitivity, and therefore it's overall tonality. The "quality" of bass is dependant on other parameters. A kg4 for example may be 3 dB down at 38 hz, but this is relative to a 94 dB sensitivity rating. On the other hand, the Cornwall is -3 dB at 38 Hz relative to 101 dB. This translate to a 7 dB difference in level, or about 5 times the efficiency (.8% versus about 4%). Although bass extension has a direct relation to the perceived tonal character of the loudspeaker, it gives us no information about the quality of the low frequency information itself. While a more efficient design my appear to have the same, or less, bass extension, the quality of that bass in almost all cases will be far superior. So...while the kg4 and Cornwall may have the same low frequency cut-off, the Cornwall clearly comes out on top when the quality of the bass is factored in. Kerry

HornEd, If I have interpreted your post correctly, then I don't think it's the speakers that are letting you down, but the quality of the source material. I'm sure I've probably raised some eyebrows, so let me explain... Our WDST technology is merely a way to "artificially embellish" a stereo surround signal and still provide good direct sound. Di-poles are another example which attempts to do this, but the main difference is they really don't provide any direct sound at all. This made some sense when all we had was Pro Logic with its mono surround channel, because you can't generate a sense of spaciousness with just a mono signal and some way of artificially doing this was necessary. The same is true for stereo surrounds but to a much lessor extent, hence our WDST technique. What's interesting though, is that as the number of surround channels increases, and as the the post production companies begin to utilize all available channels for creating the "surround effect", the need to "artificially embellish" the signal becomes unnecessary. In other words, in a 5.1, 6.1, or 10.2 system, all the speakers (minus the subs) can be used to create the proper surround effect, or they can all operate independantly in order to generate the correct discrete effect. It becomes the responsibility of production engineers to encode the proper effect into the signal itself. So...as multi-channel audio continues to evolve, the loudspeaker manufacturers at some point will probably begin to revert back to identical speakers at every location. Kerry

Although the C7 was not voiced with the epic series in mind, it does use basically the same drivers and horns. For this reason, I suspect it's a very reasonable choice (given the KV 4 is no longer in production) to use with your CF-2's. BTW: I just had to reply to a post so I could show off my new avatar. Cool, hugh! Kerry

I think I can help shed some light here... The Klipschorn, Belle and Heresy II are shipped with consecutive part numbers. The main reason for this is due to the fact that these products are "grain matched", and it is much easier to process them through the factory if they are kept together. The consecutive serial numbers only helps confirm matched pairs, since visually matching the grain would be a task you wouldn't wish on your worst enemy. The La Scala is built completely different from the above models. It is built from Birch plywood using a butt-joint construction (the reason for the exposed plys). The La Scala has never been manufactured in grain matched pairs. And it is for this reason the enclosures are not (necessarily) kept together through the manufacturing process. Grain matching is a very difficult process to keep under complete manufacturing control, because it requires a lot of skill to cut, assemble and finish a product without "goofing" something up. And if for some reason one of the enclosures is rejected, you have the decision of what to do with the good cabinet. There are many stories about exotic wood Klipschorns where one of the two cabinets was rejected. The still good cabinet, rather than be scrapped, would be converted to the theater version of the Klipschorn (TSCM) and painted with a heavy black texture paint. Interestingly enough, there are theaters out their somewhere with TSCM's made from Rosewood that's all covered up. Ya gotta love it! Kerry

After reading this thread I realized that there is some confusion over the difference between the dispersion characteristics of a loudspeaker and an individual's ability to localize where the sound is coming from. Almost all consumer loudspeakers are omnidirectional at frequencies below 100 Hz. All this means is that the loudspeaker can be pointed in any direction and the sound will still reach the listener ears equally well. A listener's ability to localize that sound is a psychoacoustic phenomenon, having more to do with the distance between ones ears. It is generally accepted that our ability to localize sounds significantly decreases below 250 Hz. Subwoofers are typically operated at 100 Hz or below, and therefore are omnidirectional sources. However, this does not means their position can not be localized. The reasons for this are twofold; First, subwoofers generate distortion components which are higher in frequency and therefore may fall in the frequency band where our ears are more sensitive. And second, low-pass filters in subwoofers are not brick-wall filters, therefore there is "some" output above the cutoff frequency of the sub. If the slope of the filter isn't high enough, our keen ears can detect the location of those sounds. The latter reason is generally not a problem with modern subs due to the fact that most filters use 24 db/oct slopes or higher. This is usually sufficient to prevent localization due to this effect. On the other hand, distortion in loudspeakers continues to be a big problem in loudspeakers and it manages to manifest itself in a variety of ways other than the one issue pointed out above. Kerry

It always seemed to me that the whole issue of electron flow in a electrical circuit really doesn't confuse things much unless your looking at a circuit that includes vacuum tubes. I guess it's because the operation of a vacuum tube forces you realize how the elecron are actually flowing. Just the fact that your applying a positive plate voltage in order to attract electrons, just seems counter-intuitive. There was an English guy that came in between Edison and DeForest who actually invented the first vacuum tube. It was called the Fleming valve and had the operation of a simple diode. DeForest took this idea and inserted the control grid which resulted in the first amplifying vacuum tube, or triode. Unfortunately, DeForest didn't understand how his invention worked. Later on, while DeForest was trying to keep himself out of jail, a guy by the name of Edwin Armstrong (who clearly understood how the triode worked) invented the first circuitry (employing feedback) that made the transmitting and receiving of radio signals truly possible. Armstrong later developed the Superhetrodyne receiver which is the basis for all radio receivers, even today. Interestingly enough, DeForest became known as the "Father of Radio", whereas Armstrong, later in life, leaped out of a third floor window. Kerry