Al Klappenberger

Dennis, Here's what I'm thinking on the high dispersion thing. The curve is the exact curve of the K2 horn, well, half of it anyway, looking down at the flat curved sides. It's the correct curve because it was drawn by a CADD program from a macro generated by my Trachorn.exe program used to design the K2 horn. The other lines were done by the seat of my pants trying to make the incidence and reflection angle equal as a sound might bounce off the curved side. I think the driver might be farther back than I have it shown though. What do you think? Hair-brained? Al K.

Dennis, "Yes, the BMS on First Octave Audio wood horns. These horns are really too big for a standard Klipschorn, Octave research sells a cornerhorn based on an 18 that has a 300hz crossover point to the Mid and HF" Yes, I think the B&C DCX50 was "inspired" by the BMS coaxial. The 300 Hz low end is what I don't like about it. It is for larger systems than the Khorn. It just doesn't need respons down to 300 Hz and below. The B&C mid-ranges were designed for the 400 Hz of the Khorn. ---------------- " Large Tractrix (or exponential) horns have very limited dispersion in the top octave. The rule-of-thumb for these types of horns is cross one octave above Fc, and cross again into the tweeter at one decade above this. This works out to a 500hz crossover for a 250hz Fc horn, and bring the tweeter in above 5Khz." This dispersion of highs is why I was so surprised to see the nice 30 deg off axis response the DCX50 tweeter was showing on Dave's horn. I expected the highs to come straight out like a flashlight beam! The crossover choice at 9 KHz is where B&C suggests it should be on its spec sheets. It looks like the right spot by the overlap in the responses of the two driver too. ------------------ "The initial expansion just off the throat is what controls the VHF dispersion. If you look at the K402 you will find this initial e"xpansion looks to be conical, only changing to Tractrix near the mouth. " This is out of my area of expertise! Someone earlier mentioned the conical throat issue. All I can say is the horn is purely Tractrix expansion but it has a rectangular cross section. Could the conical thing have something to do with the cross-section being rectangular versus round? My UNeducated thought was of the JBL "Paragon" where the mid-range horns were aimed sideways at a curved front. The highs may be bouncing off the curved vertical sides of the horn in a similar fashion. ???? What do you think? I really have no other idea! ----------------- Nat, I had thought about doing distortion plots, but didn't. I did distortion testing on the DCM50 driver that is at the heart of the DCX50 and it was very clean. Only the tweeter would be in question. I found that the small round aperture in the Beyma CP25 caused distortion when you ran it up to unrealistic levels. The throat of the tweeter in the DCX50 is right small too. RATS, Now I guess I gotta go measure that! Al K. BTW: The Sonicaps came in for the network yesterday. I think the inductors are going to take a while yet. I need them to determine how I am going to handle one inductor that is less then the 0.1 mHy smallest inductor Solen makes of Litz wire. I am going to try gluing two .1 mHy inductors together, connecting them in parallel and using mutual inductance to adjust for the value. It's going to be fun to determine the correct spacing!

Roberts, I sure wasn't YOUR new idea! Now let's see you do a Linzwitz-Riley phase coherent network for it. You can bet I won't do it for you. You can just shove my Universal network in it being you have the remainder of the 10 sets you made under license from me sitting around. You lucked out since it's at 6 KHz. What are you going to do when those run out? Guess who will have to supply them then? Where do you put the attenuator? Does it need one? What impedance? I am not going to do that research for you either! Fritz, When you say "horns inside horns" I assume you mean mounting a tweeter like the T35 inside the mid-range horn mouth. The CDX50 is different. The two drivers are actually mounted such that the two diaphragms are the same distance from you, That means virtually the same propagation distance. I suspect you know that though. I just figured I would clarify the difference. Al K

Dennis, LOVE your avatar! [Y] Al K.

Mark, All the plots are withOUT any network. There are two drivers in the DCX50. I am just plotting them separately but sometimes on the same graph. I have the parts on order for the new network but it's going to be while before they come in. Al K.

All of this sort of thing is subjective. Whatever you hear and like is all that counts for you. I my case though, I have to make things flexible so others can set them to their taste. Setting things the way I like them would only be right for me! That's also part of why I seldom say how something "sounds". I just make instrument tests. AL K.

be36, I figured a dB or two would never be noticed, but there sure does seem to be a lot of people who do. It's why I had to start putting the #4 transformer tap on my universal networks. It gave it an intermediate setting that wound up as the "normal" setting (X - 4). I was setting them at 2 - 5. That's only a 1.7 dB difference! That is on the mid-range though. AL K.

Boom, I just don't like passive equalizers. They generate too much loss and screw up the impedance flatness unless they are very involved constant impedance types. Those make even more loss because they require twice the parts count. I count on the drivers being good quality. I believe small variations should be dealt with using active equalizers instead. At the level of quality of these drivers all you are doing is guiding the lily. A good active equalizer can deal with those little corrections and your room too! In this case especially, I am trying to make a Linkwitz-Riley phase-coherent network. Amplitude equalizer also shift phase! Al k.

JC, The xo will be at 9000 Hz, The plot is 0 - 20 KHz with each division being 2 Khz. It's a linear scale. You should be able to find any frequency easily be interpolation. Al K.

One more time! This is on-axis and 30 degrees done very carefully on the carpeted floor. 1 meter away centered vertically. Al K.

I just did the 30 Deg off axis curve again. This time I set the horn on the carpet and positioned the mike very carefully 1 meter away and 30 deg off axis from the front (mouth axis) of the horn and centered vertically. It still looks good! Al K.

JC, No conical sections. Dave used the TRACHORN.EXE program I post on here a while ago to design the K2. It is a clone of the Trachorn 420 that Martinelli made for me which was also designed by the same program. I really have no explanation for the good off axis response other than it's bouncing off the curved side. I suppose some insight might be gained by testing a wide range 2-inch driver and similar horn that can go up to 15 KHz. Most of these Edgar type horns are only used for mid-range use and data on their performance at tweeter frequencies isn't common knowledge to Klipsch fans. I just don't know! SS.., I don't know about the pope. Could you accuse him of using his postion to sell bibles? That's the kind of fine line I walk! Al K

JC, I did a series of plots using the Martinelli Trachorn 420. It's the only other 2-inch horn I have here. The on-axis plots looked exactly the same. I think it's the driver. The plots are done using a 2-channel analyzer with a reference attenuator in channel A equal to the mikes output at 100 dB SPL. This means ZERO dB on the plot represents 100 dB SPL at the mike. The mike is exactly 1-meter from the mouth of the horn. That means the top line marked 30 dB is actually 130 dB SPL at 1-meter. It looks like the entire response at 30 degrees drops about 5 dB and smooths out. It's normal to drop like that but the fact that it smooths out surprises me! At 45 degrees the curve side of the horn obscures the driver throat from the view of the mike. The picture below is looking at the horn as the mike sees it. The blur in the foreground is the mike itself. The other side of the horn must be acting like a reflector to disperse the highs. I don't know much about acoustics so I really don't know. Something is bending the sound to make it fan out horizontally. Listening to the sound of white noise through the horn as I slowly move off axis clearly tells me the dispersion is far better that I expected. I'm impressed! Al K.

Please change the subject! I would rather argue religion or politics than this sales abuse thing! BE36, The main thing here is the coaxial driver and phase-coherent network. The DCX50 driver would fit on any 2-inch horn. The Fastrac K2 is larger than the Fastrac Lascala that I think you have. I think it's a 1-ich horn. You would probably need to cut the cabinet, The Fastrac K2 has the same mounting as the original Martinelli 1-inch Trachorn 400 which had a larger mouth than the Klipsch K400. Al k.

It's about people who accuse me of abusing the forum by allegedly using it as a sales tool. It was written word-for-word by Amy Unger. AL K.

No. They are mounted one inside the other, or have I misunderstood the question? Here's a view down it's throat lit with a flashlight. Al K.

Jc, Here are tweeter plots off-axis horizontally by roughly 30 Deg and 45 Deg. I'm surprised. The off axis plots are flatter than on axis! Al K.

JC, I will be doing at least one set of the LR24-9000 networks. How many I make depends on the amount of interest there is in it! The horn will be Dave's product. The one I am using for testing is simply a loaner. If there is any interest in the combination, I might offer it as a package deal along with the DCX50 driver. Dkalsi, I had never heard of the Oris speaker. I suppose I'll have to look for it. ........... Update: I take it back.. I have seen the Oris. They use the large round Tractrix horns in the midrange. That is had to beat. You got to like that look though! There might be a WAF issue to those to consdier! Al K.

Here's the B&C dcx50 driver. Notice the tweeter mounted right in the middle of the throat. Until the parts get here to build the prototype network there isn't much I can add. It will probably take about 2 weeks to get everything together. Stay tuned! Al K.

The frequency response. The mid-range response is nice and flat. The tweeter is not quite as nice, but still flat enough though. It's about 4-5 dB hotter than the mid-range. The sensitivity of the mid-range is about 110 dB SPL at 1 meter. That level will be cut down to the 99 to 100 dB of the Khorn by the woofer to squawker network. The the AP12-350 or ES400 strapped for 2-way operation will do that easily.

The impedance of the DCx50 midrange is close enough to 11 Ohm resistive that a simple 12 Ohm swamping resistor will transform it to the needed 6 Ohms for the network.

The impedance of the new network will be determined by the lowest impedance of the two drivers. In this case, that turned out to be the tweeter. At 9 KHz, the resistive part of the complex impedance is 5.8 Ohms. That is in series with about 0.03 mHy of voice coil inductance. I normally don't use a Zobel on tweeters, but since 4-5 dB of attenuation will be needed and the netwrok will be dedicated to a single driver, a transformer attenuator modified for 6 Ohms will be part of the network. The Zobel can be built right on the network as well. The values for the Zobel turned out to be 6.8 Ohms in series with a 0.68 uF capacitor. That transforms the load to a nice 6 Ohms resistive impedance for the attenuator and network tweeter channel.

I have always maintained that there is no good reason to go to a 2-inch horn to replace the K400 in the Khorn. A 1-inch horn is by far the best bang for the buck. 2-inch horns are for movie theaters but there is some advantages to upgrading the K55 driver. The problem with that is there is simply no 1-inch driver in current production that will operate cleanly down to 400 Hz where the Khorn must be crossed over. Evan the 1-inch JBL 2426h will start making distortion at 450 Hz let alone down at the 400 Hz required by the upper limit of the Khorn woofer. It was designed to be crossed over at 800 Hz but JBL says that it will operate down to 500 at reduced power. That's fine for the Belle or LaScala, but not the Khorn. Only a 2-inch driver will go down to 400 Hz. If you are ready to make the leap to a 2-inch horn and driver you might as well go a step further and make it really worth doing. B&C Speakers makes a coaxial version of their DCm50 driver, which is exactly what the doctor ordered for the Khorn squawker, a design specifically for a 400 Hz crossover. It's the DCx50. It uses the same midrange "guts" as the DCm50 but has a tweeter built right into the throat that extends the frequency range to 16 KHz. That's the same upper limit as the K77 tweeter that most of us have been listening to for years. A response that extends above that is nice but chances are only your dog is going to appreciate it! The big plus with a coaxial is that it's as close as you can get to having the midrange and tweeter occupy the same place at the same time. That means the propagation time from both drivers to you ears is virtually equal! That's TIME ALIGNMENT! Time aligned drivers let you use a far less aggressive crossover than the extreme-slope networks needed to eliminate the driver interference caused by two sources of sound located in two different places. The interference between drivers is significantly reduced. Another advantage here is that the DCx50 requires a crossover at 9 KHz rather than the 6 KHz required by the K55. This adds up to a far less aggressive network with fewer parts of smaller size. It will cost less than an extreme-slope network. Another advantage of the time alignment is the opportunity to use a phase-coherent type of network called a 4Th order Linkwitz-Riley. This type of network is usually only appropriate for sub-woofers as active filters where the wavelength is extremely long. Dave Harris (Gethover) and I have worked together to develop a 2-inch horn of comparable quality to the Martinelli Trachorn 420 that is no longer available. Dave calls it the Fastrac K2. I have posted a paste-up of pictures of the Fastrac K2 side-by-side with the Martinelli Trachorn 420. The two are identical in all the important ways. The one with the nicer paint job and all the screws down the edges is Dave's Fastrac K2. I have used the K2 horn to take frequency response and impedance measurements on the B&C DCx50 to develop the 4th order Linkwitz-Riley network at 9 KHz specifically for this driver. The new network will be designated the LR24-9000. The design is complete and the parts are on order to build the prototype. Until the parts come in, I'll share the measurements.

The way the lead wires come off the voice coil at an angle implies it's the wrong diaphragm. I once got a group of solder-post K55V drivers that were buzzing. The leads came off at an angle like that. It turned out that they had K55M diaphragms in them! The lead of the correct diaphragms came straight off at a right angle. The picture shows the correct diaphragm but an open connection at the voice coil on this particular one. Al K.

wsd, I think that should be ok. I think that foam is transparent to low woofer frequency. It just there to upset higher frequencies that might get past the woofer filter. I'm no woofer expert though. I am still surprised that the network will fit there! Al K.