Single Driver with Rear-Loaded Bass and Super tweeter by Rick Hudak I built a pair of horns last fall using an Eminence 10-inch musical instrument speaker that I found in the Parts Express catalog Item# 290-098, $35.80 each. I also bought a little bi-radial styled "Constant Directivity Horn", Item# 270-049 for $10.90 each. Crossover is a 5.6uf cap. on the tweeters and a 1.0 or 1.5mh coil on the woofer. So these speakers were VERY low budget. I chose the woofer because for it's 96dB sensitivity rating, and knowing that it wouldn't have much output at the lower frequencies I decided to rear horn load it to give it some solid bass. The result is incredible to say the least. My 10 watt tube amp (Audio Note kit 4) will part your hair through these speakers, yet all the little nuances come through as well. The sensitivity on the tweeter is rated at 99dB and several people have told me that by horn loading the woofer I have probably got the two drivers putting out about the same SPL. Crossover is a very basic coil on the woofer and cap. on the tweeter. Initial listening revealed way too much midrange output so I experimented with high value capacitors to roll the tweeter in at a higher frequency. I am also going to try a cap. on the woofer to get a 12dB slope since the current 6dB doesn't seem to be enough. Those 10-inchers really put out a lot of lower mid-range. In designing the horn itself I went with NO type of curve or mathematical formula. I know that sounds crude but I wouldn't have a clue about where to start if I was going to use any formula. (Editor's Note: you can use my Tractrix Contour Calculator applet to do this). I had studied enough horns to know that I wanted a long, gradual flare, and that all seams and curves inside had to be smooth. Interestingly I had initially opted for a very small, high compression chamber directly behind the woofer (like the Mau horns for Lowthers) but test listening to the two enclosures, one with the original small rear driver chamber, the other without the piece of wood installed to make the chamber real small, revealed that the larger rear chamber behind the woofer allowed a much deeper, more natural bass to come out. So I ended up cutting out the piece of wood from the first box. It was a pain in the ass because the glue had already had several days to cure. The wood was veneered particle board purchased from Home Depot. I really wished I had used plywood though, these suckers are HEAVY. The intent is to try and finish them up real pretty...someday. They stand around 40-42 inches tall, are 12 inches wide, and 24 inches deep. You really need a table saw to do it right, although if you were real careful, and had a good blade, you could probably use a circular saw. I started out with one of the sides on the floor, first attaching the top, baffle piece, and back panel. Next were the "mouth" pieces of the horn and the little corner reflectors. Then the larger inner reflectors were glued in and the wire was strung through. Then take pictures 'cause you'll never see the inside again. The last part involves setting the other side on this mess and gluing the hell out of everything. Before you seal it all up make sure that all the joints are smooth and that there are no irregularities in the horn path since they'll hurt performance. The only thing you need to make sure of in the design is that at no point in the length of the horn should it get smaller, it should always be expanding. Even in the U-turns. I am guessing that this horn is 10-11 feet in length. Anyway, I still need to put a finish on them and the crossovers will still need some tweaking, but they are probably about 90% "there". My total investment for wood, glue, drivers, etc. was less than $250 so they are quite a bargain. And boy do they reproduce bass! I have a couple of photos taken before I put the final side piece on, permanently sealing them up. Otherwise my next project is to build some enclosures for the vintage Altec Duplex drivers that I just bought. Horns rule! p.s. I am not an engineer, or math whizz, or anything. Just an enthusiast who wanted to tackle a pair of horns. Without much to compare then to, other than other speaker I have owned, I can only say that they have exceeded my expectations by a large margin. Top