Nat Denkin

According to Leo Beranek's book, Acoustics, eqn (9.33), the percent 2nd harmonic distortion for an infinite horn is given by 1.73(f/fc)*It^(.5)*10^(-2) where It is the power/square meter at the throat. Thus, if a horn cut off is 200 Hz with an extreme slope crossover at that frequency, and we want the horn to cover up to 3200 Hz for 4 octives, we have to consider how much distortion we would accept. Assuming a 2" throat and a 1 watt acoustical 3200 Hz signal, that equates to It = 493 w/sq m so that the 2nd harmonic distortion would be about 6.1%. I recall that about 50% of music power is below 350 Hz and that the power drops off quickly above 1000 Hz. With "large" horn systems capable of handling over 100 watts (electrical), it would appear that distortion is a design factor. Comparing a 2" diameter throat with a 1" diameter throat, we note (assuming both dimensions are exact) the smaller throat causes twice the distortion. Thanks, nat

I have been using the ALK trachorn for about two years and it is wonderful. The tractrix in one form or another has been around for about the last 80 years, whether square, round, or rectangular cross section. Limiting to the tophat dimensions is going to impose a lot of similarity as well as having to mate with standard drivers. In the meantime, does anyone have current recommendations for currently available dirviers for a DIY Jubilee base section? Thanks, nat

The 1978 Speakerlab K plans describe parts "D" and "F" as made of "clear fir or pine." "D" has a 4 3/4 base of the triangle and a 2 3/8 height. I built a pair of the Speakerlab K's in the early 80's and last year updated them with new woofers (the ones with the heavy cast frame) from Bob Crites. I did not include the damping material that Speakerlab recommended when you used their woofer. I also use the Atlas Sound PD-5VH Midrange Horn Driver with Al Klappenberger's Trachorn 400 and built his universal crossover network. A Beyma CP25 provides the high end. I would be concerned about changing the dimensions of "D" because if you don't like the result, it is very hard to replace (especially if you use glue and nails). The resulting system has great sound and I like it the way it is. On the other hand, with a DIY project you are free to experiment. nat

nat I built DIY clones 25 years ago and last year decided it was time to update. I am using the Atlas PD-5VH driving ALK's trachorn along with the Beyma CP25 and Bob Crites heavier woofer and the ALK universal.crossover network. I am very pleased with the results. The drivers, electronics, and horns seem well matched to me.

If I recall correctly, distortion is proportional to the square of the pressure in the throat. As the pressure of the air varies, so does the speed of the sounds going through it. That's one of the reasons speakers use multiple drivers to keep the mid and higher frequencies away from the varying presssure of the lower frequencies. Effieciency does matter for a given design, but horns are not the only way. AR-3's sounded pretty good in a dorm room decades ago. It can be fun to "improve" the sound of speakers changing the drivers, horns, and crossovers. The result is a personal choice. There will always be many claims of the absolutely best design--and they are all correct. People who build their own speakers are more passionate about the results--and they should be. nat

On Ebay, Bob Crites sells two speakers modeled on the K33. One is modeled on the pre-1985 Klipsch K-33E woofer and fits the LaScala. The other has a heavier frame, more powerful magnet but requires some modification of LaScala.

Several people on these forums offer crossovers and upgrade kits. Following their choices, you will have a reasonable balance of cost and performance. Matching values is desirable for both channels to sound the same (not to be confused with tolerance). While 10% tolerance may be adequate for low order crossovers, steeper slope designs may require either 5% or 1% to retain the proper filter shape and transient response.

The woofer inductor should be 1.3 mH, not 0.13 mH.

While the instructions are a little confusing at times, the photos are clear how everything is connected. The instructions are very detailed so that the crossovers are exactly the same for the two channels. The results are worth the effort.

That's for the pair.

The ALK Universal is available as a kit for a mere $290. It uses several less expensive capacitors than the wired and tested version, but is a great choice for the budget minded. The improvement in my system is INCREDIBLE. It is a work of art for both the eyes and ears.

The difference in melting points may be affected by the amount of lead in the solder. WBT sells a lead-free 4% silver solder that melts at the same temperature as the Dayton solder.