Al Klappenberger

I built a network for such a situation several years ago. The entire high end of the LaScala, without any bass driver at all, was mounted in the center. The network simply provided a dummy load resistor in place of the woofer. For a center, you simply don't need a woofer at all! Bass is so non-directive that the flank speakers or sub-woofer will do the job completely. AL K.

Nat, I have the old Klipsch bibliography of articles published by PWK. I think the test he did by moving the high section around is described somewhere in there. I just need to dig it out and look for it. That requires getting the lead out of my butt though. That's a tall order! The experiments you suggest all assume that even 48 dB / octave is a high slope. That's still rather gradual for what I'm thinking would be needed to really isolate "double exposure" from complex component overlap between drivers (phase errors BETWEEN components). The extreme-slope networks that have had the reactions of truly opening the stereo image are zero-placed filters which have slopes of over 100 dB / octave down to about 20 dB attenuation increase more gradually slowly beyond that. Crossover frequency should be where we normally cross to the tweeter, about 6000 Hz. I think an experiment where a tweeter connected to such a filter is moved to and from the listener by a second person might be valid. I believe the listener should be blindfolded during the test so that he is relying on his hearing, not visual clues though. The program material used is an open question in my thinking however. I suspect it should be something with a lot of high frequency content. A female vocal, or maybe a violin solo. I generally try to think up some sort of continuous instrument generated sound for tests like this, but in this case I don't know what that would be. Whatever the choice of program, it would need to of short duration and repeated from the beginning each time the tweeters (both of them) were moved. My obviously biased expectation here is that the listner will be hard-pressed to hear any difference except for more highs as the tweeter is moved closer. They should get louder. This sort of testing is not simple! Al K.

RATS! I thought I could finally cash in! [:'(] Al K.

Mark, I was not involved in the decision about what high crossover to use. I would have suggested the high crossover be extreme-slope also. One good reason to go with what he did is because I have not made the ES squawker / tweeter network designs public. The inductor placement is too critical for DIY builders. I think what he used was his only choice. Al K.

HOT DOG! Now Dave and I have an excuse to raise our prices! [] Al K.

"So, are you saying that physical alignment isn't acceptable and audible but using delays to accomplish the same thing is ok?" No.. What I am saying is that moving the drivers is not acceptable to most loudspeaker owners. The WAF and all that! Stereo fanatics like us will do anything! That's part of the fun. "you still haven't tried this, then Dennis is correct. and you shouldn't be commenting on it."When I have a point of view based on facts I have insight into I have a right to comment as I please. Do you have a point of view on mercy-killing for example? Should you try it before you comment if that were the subject of discussion? I won't try something I believe is not conclusive when I believe there is a better way to accomplish the same thing. Maybe he should not have commented about time aliment until he tried extreme-slope crossovers.He was talking from within his experience as am I. I say he should not have suggested that I should shut up! Fact is, I considered it offensive. "For me, moving the tweeters was a no brainer. The cost was zip, so my only investment was time." ABSOLUTELY! I agree totally! Oh yeah.. One other point. Your tweeter, sitting back like that, is only time aligned horizontally. You still have error in the vertical plane. That causes trouble too. I doubt it's as big a deal as direct path timing though. It will still cause comb effects if both drivers are making the same sounds. Al K.

Fritz, Thank you! That is exactly what I was referring to in my last post. My memory wasn't fooling me. The implication is that it is importnat to fix the timing problem between a tweeter and a mid-range but maybe not between a woofer and mid-range. Maybe becasue of the wavelength relation to the speed of propagation. Maybe it's just human ear / brain comprehension too! Al k.

Ok.. Here's what I am getting at.. The fact is that I hear this exact conclusion from people who have installed extreme-slope tweeter / squawker networks. The stereo image improves and the sound is clearer. I believe there are two factors here. The fact is that not many of us are willing to mount the tweeter a foot on top of the cabinet and to the rear. And what do you do to align the midrange to the woofer? You drill a hole in the wall! RIGHT! When a tweeter is closer to you than the mid-range using a gentle slope crossover you are getting sounds meant for the mid-range into the tweeter and tweeter energy in the mid-range. If your tweeter is closer to you, as most are, you get energy on both sides of the crossover first from the tweeter than you get it again from the mid-range. This is perceived by the brain as an echo. It screws up the stereo image and it causes a smearing and comb efects. This I can hear with my own ears. It went away when I installed a crossover that let only the correct driver make the sound it was intended to. In this case each driver is making only one sound. The only alignment you do by lining up the drivers in this situation is to align the high set to the low set of components of a complex waveform. Until these are so out of time that you hear them a separate entities there is nothing to align! My experiments with multiple generators proved to me that I can not hear phase misalignment between complex components even if they are continuously changing on a fixed tone. This is all that is left when you have only a single source generating each component (harmonic). Moving a driver while using a gradual slope crossover does not tell you what is important. Is it the double occurrence of everything, or the phase errors becoming individual entities to your perception? Moving drives like that will not answer the question, You are moving both at once. Another point: I read someplace where PWK did a similar test moving the high end of a Khorn to establish if alignment between the woofer and high section was important. His conclusion was that it was NOT! This is what he WANTED to conclude though. Preconceived notions are very important here. If you believe a sugar pill will relieve your pain, it probably will! Assuming he was right. At what frequency does this time alignment become important? I believe the only way to determine how much time misalignment is acceptable between components of a complex waveform is to use a ACTIVE extreme-slope crossover with a variable delay in one channel of a 2-way system having a high crossover frequency. That's a tall order! One person listens while another moves the delay. Note that there must be NO OVERLAP of energy between the drivers, If there is, you are back to the double exposure thing you will have by just moving a driver! A third point: When I hear comments like "wow" and "boom" and "within 1/2 inch" my red flag goes up. Audio just isn't like that, but preconceived notions are. PLEASE MAKE NO MISTAKE ON THIS POINT. It is not an insult or an attack on anyone's integrity or honesty. It is human nature! This is why double-blind trials exist. A single persons opinion is valuable as just that, a single opinion! I really would like to know what amount of delay the ear can tolerate between "harmonics" before each become individual entities but I can not accept sliding a tweeter at you is conclusive of anything but that there is SOMETHING important going on. There have been enough single persons observations to convince me of that point. The question that I want answered is exactly what! Al k.

Dave, What network where you using when you did that? I really want to get to the bottom this, but moving the drivers around is NOT conclusive to spite how obvoius it might seem. Al k.

Marvel, What networks in in your LaScalas? AL K.

Here's what the bandpass through the mid-range looks like. This shows the contrast between the extreme-slope 600 Hz crossover performance compared to the 12 dB / octave 6000 Hz crossover. Al K.

I have never built this network myself. I designed it for JC just for the fun of it. It is an extreme-slope network. The 10 dB driver interference window is only about 40 Hz wide at 600 Hz. The impedance dip at 600 Hz to about 3 Ohms is intentional to compensate for component losses. The design impedance is 4.8 Ohms. The 12 Ohm swamping resistor at the output of the highpass allows any 8 Ohm high section to be used and still properly terminate it. 12 Ohms in parallel with 8 Ohms is 4.8 Ohms. As Dean said, the high section is simply the 6000 Hz crossover section of the "Universal". Here's the computer analysis of just the 600 Hz crossover section. Al K.

Dennis, "Why don't you try it before commenting" Very simple: I'm not about to start removing drivers from my speakers and running back and forth moving each driver 1/2 inch at a time on both speaker while resetting the test program each time. Even with help from another person. It's silly! A study like that should be double-blind anyhow. In short, I don't beleive the test that came up with the 1/2 in number was conclusive. Al K.

It would seem that this question should be resolvable, but moving drivers back and fourth by hand seems a bit crude. The "1/2 inch" thing seems a bit to simplistic, You can change the path length from two things to you that are sitting 6 inches apart horizontally by a half inch just by taking a single step to one side! I think there has to be more to it that that. One thing I think is for sure though. Perfect time alignment is obviously better, if you can do it without compromising other factors. Digital delay equipment is the way to do it. That means bi-amping or tri-amping. That can be a bag of worms. I think it's the way to go if your are up to handling the worms! Most people are not. Al K.

Mark, That 1 mSec number would have to be explained more as to what it really means. It's out of context. It could be that the difference you heard with the time aligned system was the difference in damping factor gained by removing all the losses involved with the passive crossover. This is what bi-amping is all about. Like with the 1 Msec number. It's hard to pin down what the actual change you heard is really the result of. Testing for the delay time that would be required for the different components of a waveform to be perceived as separate sounds is difficult considering a short "pip" type of sound is constructed of may components itself, so it's becomes difficult to identify what "harmonic" is what! I think such a sound would be required just to identify it over another sound. That's one reason I say the 1 mSec number is out of context. That stuff gets sticky! Remember the classic tap dancer thing from years ago. Two taps were clearly being heard in their entirety twice. The complaint was not a thud followed by a snap assuming a "tap" consisted of thud+snap at the same instant. Using the same analogy, what was heard was thud+snap followed by another thud+snap, not thud, then, the snap an instant later. Confusing isn't it? Taking it even further, What delay is requited between the thud and the snap before you hear each separately? That is what I don't know!! [:S] I think THAT is time alignment. The snap twice is driver overlap.

Mark, I think what most people miss on the time alignment thing is that "time" and "phase" are related. If only a single driver is making each "harmonic", than the only relationship that is misaligned is phase. I believe you ear is totally deaf to the phase relationships of harmonics to the fundamental. I experimented with this by using three different sine wave generators to simulate the harmonics of a square wave (1 Khz, 3 Khz and 5 Khz sumed together with levels 1/1 1/3 and 1/5.). This simulates each harmonic reproduced by a different driver. Only in this case the phase is continually changing, not just knocked out of phase to a fixed degree. I listened to the sum through headphones while looking at the signal on an oscilloscope. The waveform crawled like a worm through all sorts of shapes. To spite looking at the scope as a clue, the sound was a continuous raspy tone, just like the crude square wave it would represent if the phases were fixed and aligned properly. I conclude that YOU CAN NOT HEAR THE PHASE ERRORS BETWEEN COMPONENTS OF A COMPLEX WAVEFORM, even if they are continuously changing let alone if they are fixed! What you CAN hear is if each component comes to you twice or if they are so far out they become separate sounds resolvable by your brain. Your brain can't sum up unrelated tones in real time. It's just not fast enough. Only an oscilloscope can do that! It can compare phases of the same tone if they come to both ears at once. That's the stereo image. The only question becomes: how far out of time do the components have to be before the brain can resolve them as separate sounds. I don't know! Al k.

Mike, I tend to agree. The driver used in the test was a coaxial B&C DCX50. It's the same type driver as l istend to a week or so ago, just a different one. The polar response above the crossover (about 9 - 10 Khz) acted squirley. The bottom line for me is that nothing beats a good 3-way system with extremely steep crossovers between them. The killer is overlap, not delay or phase errors! Lee set me vertical polar plots a while ago too. They show as smooth transition to a narrowing pattern as frequency went up. Again, this went squirly as the tweeter section cut in. Al K

Jc, "I wonder if the upper frequency coverage would be better with a non coaxial 2 way driver? Like say a JBL 2446 or something else?" I am no expert, but I think the performance of the horn is separate from the driver once the anomalies involved with the crossover are factored out. I would like to see test to be sure of that, but a driver that will go from 400 Hz to tweeter frequencies is rather hard to come by! Al k. BTW: I have the JBL 2426h (a 1-inch driver) and have tested them on several horns. It makes it flat to 6KHz but drops quickly above that. If the 2446 is similar it would require major EQing to use it seriously for a 2-way system. I have done that with the 2426 and it sounded fine though. It is a possibility.

Here's the mid-range polar plots separated. Al k.

Here's another way to look at the directivity. Real egg-head stuff!! Lee sent me the raw dat and the software to organize it all sorts of ways. It will display the polar plots one frequency at a time. Doing that shows the beanwidth just starts to narrow up a t 4000 Hz and only drops ab it to 6000 Hz. That says the 4000 - 6000 Hz Crossovers we have been using is perfect for a 3-way system. I'll post those next. Al K.

Here's the polar plots on the Eliptrac 400 horn using the B&C DCX50 driver. It's the same horn as in the picture of it sitting on top my Belle Klipsch. With thanks to Lee Clinton. I am no expert on this sort of thing, but I think this is typical of using a big horn to go wide range. It's going to beam the highs. I suppose I just like 3-way systems! The dispersion is very smooth at 8000 Hz and not too bad at 12K. I don't think there is much doubt it will make a super mid-range horn with a separate tweeter. Al K.

Well, I beleive vacuum tubes can have them.. That's as far as I will go! Caps, wires and crossover, NAH! Al k.

No matter how far out an idea can go, even in fun, somebody will take it seriously! No matter how obvious it is that a product is just snake-oil, somebody will buy it and think it's wonderful! When it's plausible, like the microphonic network myth, then the arguments start. B.S. has a big advantage, it has no restraints placed on it by truth. It only needs to be composed to sound believable! Human nature sure can get interesting! Al K.

Coytee, Sorry to differ, but it depends on the wavelength! distance = wavelength / pi * sqrt(speed of sound in coffee) / time of high tide. (Velocity is in furlongs / fortnight) Oh yeah, one other important thing. The must be of Styrofoam so they will float when the tide comes in! The paint color is optional though. Al k.

I have been following this thread. I have to say that this is one of the best home-built speakers I have seen. All except for those crumby looking crossovers, that is! Who did those things anyhow? Who painted them black? YUCK! [] Al K.