Al Klappenberger

such a deal! I UNDERSTAND THEY ARE EVEN GOING TO LET YOU PAY SHIPPING! JW, Any opinions yet on how it sounds? Al K.

PrestonTom: The second problem with this thread is that it is actually a thinly veiled infomercial. If you beleive that, read my "Signature" below and take it to Amy. I DON"T WANT TO HEAR IT! Al K.

Here's some more good dope on the HF200 + Eliptrac combination. On-axis response and distortion plots. Again with thanks to Lee Clinton! Al K.

Rudy, I'm not sure what you mean by "try the two way down to 1", The mid-range output of any of my networks will operate the HF200 without any mods. ES400, ES500, ES600. AP12-350, AP12-AK3 ... etc. All will work without modification. So like I said. If you want to try 2-way, GO FOR IT! Al K

Guys, .A little dose of reality here. Here's the rub... Like I have said before, good engineering is always a balance of trade-offs. If you want at 2-way system you will be stuck with collapsing distribution as frequency goes up. This is what a CD horn is all about. I personally have never heard a full-range one, so I can't say what the down side is myself, but I have heard people say they sound like a frying pan. This is the up-side of a 3-way system. A little tweeter can distribute the highs far better than a big horn like the Eliptrac designed to load a driver to below the Khorn's 400 Hz crossover needs. The Eliptrac will still make a beautiful mid-range horn. Let's not loose sight of the fact that it's the Faital Pro HF200 driver that is letting us do a 2-way system, not just this horn. I still believe in 3-way systems especially when an extreme-slope crossover to a tweeter can make the time alignment issue restricted to just a small window of frequency right at the crossover. If the tweeter section of the coaxial B&C DCX50 had a high frequency distribution that was better, the phase coherent crossover idea would not be obsolete, but since it's no better than the HF200 on the same horn, why bother with a coaxial? This is what we have accomplished here. Personally, I will take a good tractrix horn like the Eliptrac in a 3-way system with an extreme-slope crossover to a good tweeter over a time-aligned 2-way where the highs come at you like a flashlight beam or the high end sounds like a frying pan any day! THAT folks, is your trade-off. For me, the decision is if I will make a step forward in my own system by replacing my Martinelli Edgar type 1-inch Trachorns with the Elliptrac horn or not. Now that Dave has come up with a 'correct" 2-inch down to 1-inch adapter, this is a possibility. I still do not believe a 2-inch driver is needed in a set of Belle Klipsch (or a set of LaScalas). I don't have to cross over at 400 Hz where only a 2-inch driver can operate cleanly. I can cross over to a mid-range at 500 Hz where my 1-inch JBL 2426h drivers can function without distortion. I have already modified the Khorn frames Dave built into the first prototypes of the Elliptrac to fit by Belles. All I need to do is add the 1-inch converter, staple on the grill cloth and install them. SHOULD I DO IT? Al K.

"Basically you have a horn/driver that collaspes it's polars in both the Horizontal and Vertical planes." I think that's exactly what you would expect from anything but a constant-directivity horn. It's one of the criteria used to pick the crossover frequency. You pick it where the directivity patterns are similar between the two horns and drivers being crossed if you can. AL K.

Here's the crossovers he is using in the Jubes. I'm sure it's a simple gentle slope thing. I have no way to know if it's designed right or not. Al K.

Lee just sent me some photos of this test setup for the polar plots. Here's two of them. Al K.

Well folks, It seems the coaxial B&C DCX50 plus the 9KHz Linkwitz-Riley crossover idea that started this thread is already obsolete! With a HUGE thank you to Lee Clinton (Arkytype), we have both horizontal and vertical polar plots of the Faital pro HF200 driver on the Eliptrac 400 prototype horn. It looks like we have what we have all been waiting for, a good two-way Khorn! Here is the polar plots all overlaid for direct comparison. BTW: Bob Crites has the HF200 drivers in stock at what looks to be a very good price. Al K.

"Please look at this and calculate the delay on the tweeter at the crossover point (the acoustic center of the tweeter is in front of the woofer in this model)." Group delay comes to a peak at around the 2 dB point down the slope of most filters. A group dealt peak is NOT TIME DELAY because it is not flat over the area. This represents phase non-linearity which is inaudible and attempts to correct for it in any way is detrimental! Al K.

"If you can't, I WILL and show what it would take to do it and why it's not practical!" OOPS, I forgot, I already did half of that already. Sounds travels 13500 feet / sec. The K400 is 22 Inch long and the K77 sits back about 2 inch. That says we need to dealy the tweeter by 20 Inches. 20 / 13500 = 1.48 mSec. The example earlier used four 2-nd order all-pass sections for an equal ripple delay of about .266 mSec. So.. all we need is 1.48 / .266 = 5.56 times as many sections. We had 4, so all we need is 22 sections. That's just plain DUMB! Al K.

"I'm sure you will find a way to improve on B&Ws method and share it with us" Yes.. Get the lossy all-pass equalizers out and position the direct radiators they use equi-distant from the listener. Oh, that's right, they already do that! Now.. show me a buildable network of all-pass filters that will delay a K77 enough in time to equal a K55 on a K400 horn. If you can't, I WILL and show what it would take to do it and why it's not practical! OR -- Design a network for me that has sharp enough skirts that there is nothing to time align. That is, Go to a catalog of singly-terminated normalized elliptic filters and scale them into a 6000 Hz diplexer. When you are done you will have something that will make it sound better. BTW: have fun finding the 3 dB point on an elliptic filter normalized to last-ripple at 1 radian! All-pass equalizers cause for more trouble than they solve. Al K.

Differ all you like. They are all-pass GROUP DELAY equalizers. To try to use them in passive loudspeaker networks is DUMB. Al K.

The only difference between the AK-2 and AK-3 inside the woofer hatch is the two caps. The AK-2 has 140 Uf and the AK-3 has 100 Uf. 94 uF is good enough. Replace the two caps with two 47 uF mylar caps. Solen Bennic is what I use in the AP12-350, which is the same thing. Al K.

Here is what is required to generate 1/4 of a millisecond group delay from 6 to 15 Khz for a tweeter. 4 2nd order sections requiring 8 inductor and 12 capacitors. Notice the increasing loss as frequency goes up. This is assuming an inductor "Q" of about 40. That means Litz wire, Al k.

The "T" and Lattice circuits above are 1st order group delay equalizers. They are NOT time delay equalizers. They will not function to equalize time in a crossover. Group delay is a measure of phase linearity, not TIME DELAY! The two are equal ONLY of the group delay is perfectly flat over the frequency range of interest. All-pass networks are NOT! Here is an example if a "T" section equalizer designed to produce 1 mSec delay at 20 Hz. Note that it generates that group delay (not time delay) at only a single point. The group delay increases rapidly as you go down in frequency. To generate a flat equal-ripple group delay requires many SECOND order sections in series. This generates major component losses. As you go up to tweeter or mid-range frequency the amount of delay possible becomes lower requiring even more sections. Note that the group delay at higher frequency drops to zero quickly. The inductor required must have extremely tight coupling and be center tapped. It should also be bi-filer wound. Have done may equalizers like this at high frequency I have found the usual requirement is a single 1st order equalizer low in frequency followed by two or more 2nd order sections to equalize a lowpass filter. Narrower frequency ranges require only 2nd order networks that require 3 caps and two inductors for high delay. These display a sharp peak dropping off on either side. FORGET THIS! Al K.

Both the AP12 and ES series are designed for the K33 woofer. The difference is the crossover frequency and the steepness of the skirts. The 350-400 Hz networks are for the Khorn. The 500 Hz networks are for the Belle or Lacala. The Cornwall is best crossed at 600 Hz. The AP12 sereis is 12 dB / active. The ES networks are about 120 dB / octave down to about 25 dB. Extreme-slope networks give you a better stereo image and lower distortion. Al K.

Rudy, On the round tractrix, GO FOR IT! They have a good reputation. Al K.

Well folks .. This is embarrassing, but I just had to try out my hair-brained acoustic tweeter delay line pipe idea! I made one out of layers of particle board squares with a 1 inch hole in each. The total length is 9 3/4 inches. I stuck it between a B&C DE10 driver and ME10 horn. I measured the frequency response with and without the delay pipe keeping the driver 1 Meter from the mike. Now I know why nobody has mentioned this idea before. It louses up the high frequency response. Oh well, it was a fun project! Al K.

Rudy. Now you are getting into an area I know very little about. The "common wisdom" seems to imply that wide horizontal dispersion is good. I really don't know why and "common wisdom" is often wrong! Al k.

"Sounds like every option is some sort of compromise." This is the very root of all good engineering. It's picking the best balance of compromises. AL K.

Rudy, " Is my understanding correct that a round horn would be optimum?" Actually no! A round horn is only optimum for reflections off the mouth and probably diffraction too. BUT: It has no dispersion control. It has the same directivity pattern horizontally and vertically. You would like the horizontal dispersion to be wider than the vertical. I think the Elliptic is the best compromise. Lee Clinton said he would be doing both horizontal and vertical polar plots on the first Eliptrac 400 prototype and HF200 driver next week. That should illustrate the point. Al K.

And, just for laughs: Al K.

Rudy, No, but I would think a 2-inch round Tractrix should be easy to find. I would be surprised if they are not available, but I never looked. I'm quite sure Dave Harris (Gothover) could make you a set though. The computer program I wrote to design the Eliptrac horn will do round horns too. Sample below. It would be 13 diameter mouth. 10 1.4 Inch long and cut off at about 328 Hz. AlK.

Bernie, You have it exactly right. two 70 Uf caps can be replace with 50 uF caps of any brand or type you like. The frequency is so low here (400 Hz max) that any type is ok. I use mylar in the AP12-350 which is the same exact filter. I use 47uF + 47uF Bennic mylar (polyester) for 94 uF, which is close enough. Don't wast money or fancy brands like AuriCaps here. That would be a huge wast of money. However: I don't suggest the AP12-AK3 option for the AK-2 network because the object is to not have to open the woofer hatch at all. If you have to open it to change the caps from 70+70 to 47+47 you might as well just bypass the entire thing and go for the AP12-350. That has the AK-3 woofer filter built right on it plus a slightly better inductor too. AL K.