Tractrix Posted August 26, 2011 Share Posted August 26, 2011 Well, I'm impressed! I tried playing with the speed of sound in Erik's spreadsheet and it didn't change the length of the horn very much. It's the difference in length that has me scratching my head. Erik gives 67cm whereas the others are more like 160cm or so. I'm thinking of just sticking with a 100Hz hyp-ex that is 105cm long and admitting that I can't live without a direct radiator subwoofer. At least in this case, both Erik's spreadsheet and Hornresp give the same results. The last time I designed a horn was 20 years ago, when I had a Mac computer with MathCad on it. I used the formula's from Bruce Edgar's Speaker Builder articles.I paid someone to build a 1/4 size 70Hz hyp-ex straight horn using the EVM-15L lead guitar driver. I was happy with it and stopped designing horns. I now think almost 4 feet (including rear chamber) is kind of excessive for horn length in a normal size living room. Quote Link to comment Share on other sites More sharing options...
Tractrix Posted August 26, 2011 Share Posted August 26, 2011 Having the mouth cut off is less correct, so in that instance Erik's spreadsheet is better as you will get less edge diffraction. Or something like that... That sounds right to me, but the folks working with Hornresp seem to think just hacking off the horn is the proper way. Erik's spreadsheet seem to make a miniature horn with the same final 90 degree flare of a typical tractrix. I just can't believe the length since it is so different from everything else I've used. This thread talks about how different people truncate or miniaturize a tractrix horn from full size to something smaller: http://www.diyaudio.com/forums/multi-way/194184-tractrix-1-pi-2-pi.html Quote Link to comment Share on other sites More sharing options...
Invidiosulus Posted August 26, 2011 Share Posted August 26, 2011 I may have missed it but what frequency are you aiming for? Quote Link to comment Share on other sites More sharing options...
Tractrix Posted August 27, 2011 Share Posted August 27, 2011 Well, I found that the B&C 12PE32 is an excellent driver for a horn, so I bought 2 of them. I only had Erik's spreadsheet at the time, and saw that a 60Hz tractrix 1/4 size could be only 67cm long. So, I got excited and ordered the drivers. Then I used Hornresp and saw that there was a big difference using that program, where the length was something like 160cm! So, I've been trying to figure out which program is the correct one, double checking my numbers over and over again and scratching my head. I used another program and it said something like 158cm for that horn, so I guess Erik's spreadsheet has an error in it. So, I designed a 100 Hz hyp-ex, 1/4 size, that is 105cm long. It seems like a waste to use this driver for that, since the Fs is 51Hz, but without an accurate way to design a tractrix horn, I'm left with the hyp-ex, which isn't a bad thing really. Most people use hyp-ex for bass horns since they easily extend to the horn's Fc. Tractrix bass horns a known for not really extending to the horn's design Fc. So, I thought I'd ask the horn experts here about this and see what everyone had to say. I was just told on another message board that Erik made a mistake in his spreadsheet. The formula for the mouth radius has the speed of sound @ 340m/s. That needs to be changed to 344m/s and then it agrees with the other software! Quote Link to comment Share on other sites More sharing options...
T.H.E. Droid Posted August 27, 2011 Share Posted August 27, 2011 Takes me back to the good old days. I built a dance club and the owner wanted a really impressive bass system, so I hung a CL&S Liviathon straight bass horn with twin gauss 15" drivers over the bar pointing into the center of the dance floor. That unit had to come through the door in pieces, too. If I remember the mouth was a bit over 7' diagonally. Crossed it over at 200 hz into 12" dual bass bins over the dance floor, and pushing everything with 800 wpc QSC amps. Since the dance floor could hold about 500 people, it actually sounded pretty good. The first plan called for 8 LaScalas distributed around the floor (hung from the ceiling) but there's nothing like a straight bass horn. It was lit, of course, with lights that followed the bass. I always wondered what happened to that horn. Quote Link to comment Share on other sites More sharing options...
atilsley Posted May 27, 2012 Share Posted May 27, 2012 Hi folks. I'm wondering if there's any further updates to this great thread...and congratulations to JC. I've not seen too many horns like this...and I'm keen to build this...as I believe the 80/90 to 300Hz range to be so critical for a good lisetning experience. THIS link shows a 'similar' horn. May I ask some questions...? 1. was there consensus on the size of the driver chamber? 2. Because of room restrictions, I plan on having the horns placed 'portrait', not landscape. Will this have much bearing on the bass response? 3. Is the driver fitted at the 14cm depth mark? Regards Andrew Quote Link to comment Share on other sites More sharing options...
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