Ken B

Chris, thanks for your thoughtful and informative posts on multi-amping, active crossovers, time and phase alignment, and other techniques of horn rescue. Your comments are enjoyable, intelligent, and intelligible to a non-engineer. I have a pair of vintage KHorns, of which only the bass bin remains, refitted with Crites 1526C woofers. After 20 years’ listening, for my purposes the KHorns had two fundamental problems – ringing, shrillness, honking, and and smearing in the upper treble from the mid-range horn, and a general murkiness - a lack of precision, definition, and placement that I get from my linear-response Snell Bs. One of the most striking characteristics of the KHorns has been the next-room effect – from the next room, the music sounds LIVE, but disintegrates when sitting in front of the speakers. This seemed most likely a result of time/phase misalignment of the three drivers, which are widely separated, and possibly interference or distortion associated with the crossovers. I replaced the midrange horns with Eliptrac 400s and 2-inch BMS 4592ND drivers. This cured the first problem, and transformed the speakers, as well as providing sunny mornings on the porch sanding, smoothing and lacquering the horn kit, which I highly recommend. Instead of replacing the crossover and tweeters, I bought a pair of “great” Heil AMT drivers, which are essentially flat from 1700-20K Hz, and being essentially massless, have virtually instantaneous response times, and sound that may well be as clear as light. I had always wondered whether they could be harnessed, after the spectacular sonic failure of the ESS AMT-1s of my college days. The only path to this hybrid solution was by tri-amping, since the efficiency of the AMTs is said to be 99 dB, the BMSs are rated at 118 dB (in mystery 300 Hz horns), and from other forum posts the bass bin and Crites drivers appear to crank out about 102-104 dB (1W/1M??) in a solid corner. An apparent advantage of tri-amping the system was the ability to use different low-power amps selected for the three drivers and ranges, avoiding phase inversion and distortion, and other benefits (such as 24 dB/octave crossovers) discussed in this forum. I started with Nelson Pass’s First Watt JFET J2 amp (25W into 8 ohms, 2-gain stage, class A, balanced) and F3 (single gain stage, 15W, class A), and an Adcom relic for the bass. The combination of the J2 and the BMS/Eliptrac midrange is transcendental, and the transition from the bass is seamless at 400-450 Hz. The F3 has enough power for the AMTs, and varying the crossover from 1700-2200 Hz reveals the subtle coloration introduced by the horn, and the impact of the harmonics and transients conveyed by the AMT. IM initial HO, the sound from the mid-horn is so good that the AMT is not a big advantage in the 1700-4K Hz range, even if its reproduction is more perfect on a scan, but I need to spend more time with Pink Floyd, Don Ross and UMIK-1 exploring that question. Thanks Chris for this valuable insight. For proof-of-concept, the Behringer DCX is inexpensive and easy to set up and use, but somewhat noisy despite its balanced outputs. Its huge and compelling advantage is the ability to time and phase align the three drivers, and to adjust the output for disparate amplifiers. With the DCX, it’s simple to manually adjust the delay in millisecond amounts, along with crossover points and slopes, and to compare the difference. I agree with other posters. Once you have heard the KHorns in time and phase alignment, you will never go back. Instruments pop into place in the soundstage and stay there, with every nuance, floating in a sound hologram envelope. I would appreciate any comments from experience on the power requirements for a tri-amped KHorn system, assuming that half or more of the power in the crossover system goes to the bass, and that there are significant losses in the passive crossovers. The 15-inch woofers are big even if the bass bin is efficient, but for driving them directly from an amp, without resistors or inductors, shouldn’t 25W be enough? The First Watt class A amps are noiseless, and the DCX is not a realistic long-term option in a system including the Berkeley Alpha USB interface and a comparable balanced DAC/preamp/crossover. I’m somewhat surprised to hear that posters haven’t been happy with the DEQX, and would appreciate any feedback on the HDP-4, which is supposed to be made with high quality components. thanks, Ken

I'n new to the forum, new to crossovers, and have a question about changing the tweeter crossover frequency on a Crites rebuilt AK-3. The board does not have an autotransformer. I want to change the crossover from the squawker to about 1700 Hz, to drive a driver having a flat impedance of 5.6 ohms from 1500-22000 Hz. Could this be done by changing the caps or inductors? May sound crazy, but it's the facts. Thanks for any comments.