tractrix horn spreadsheet wanted please

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   It looks likely that I will be buying a house in the near future; it is therefore vitally important that I start designing a tractrix horn on which to mount a BMS coaxial compression driver.  If there’s only one piece of furniture in my living room I want it to be a pair of large circular tractrix horns like those on the tannoy VQ mid-tops. 

Does anyone have a spreadsheet for calculation the area of a tractrix horn with varying distance from the throat so that I can start designing a horn?

Something much like centauri’s spreadsheet for bass horns would be great but for tractrix instead. If no one has one does anyone have the formulas for calculating the expansion myself?

I will no doubt be making them out of rings of MDF and sanding them smooth.

Thanks,

Nick

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biotec Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 07 June 2004 Location: United Kingdom Status: Offline Points: 2867	Post Options Post Reply Quote biotec Report Post Thanks(0) Quote Reply Topic: tractrix horn spreadsheet wanted please Posted: 05 December 2008 at 5:48pm
	It looks likely that I will be buying a house in the near future; it is therefore vitally important that I start designing a tractrix horn on which to mount a BMS coaxial compression driver. If there’s only one piece of furniture in my living room I want it to be a pair of large circular tractrix horns like those on the tannoy VQ mid-tops. Does anyone have a spreadsheet for calculation the area of a tractrix horn with varying distance from the throat so that I can start designing a horn? Something much like centauri’s spreadsheet for bass horns would be great but for tractrix instead. If no one has one does anyone have the formulas for calculating the expansion myself? I will no doubt be making them out of rings of MDF and sanding them smooth. Thanks, Nick
	me so horny, me love you long throw.

S DeXter Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 12 May 2008 Location: Moon Status: Offline Points: 1262	Post Options Post Reply Quote S DeXter Report Post Thanks(0) Quote Reply Posted: 05 December 2008 at 7:38pm
	Is the tannoy a tractrix for sure? What about Oblate spheroid, i can get you the formula for that....

S DeXter Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 12 May 2008 Location: Moon Status: Offline Points: 1262	Post Options Post Reply Quote S DeXter Report Post Thanks(0) Quote Reply Posted: 05 December 2008 at 7:43pm
	Heh good old google.... http://www.geocities.com/agalavotti/tractrix.htm i think the tractrix looks a bit more curved than the tannoy, i may be wrong tho....

Deadbeat Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Old Croc Joined: 12 March 2008 Location: Singularity Status: Offline Points: 3162	Post Options Post Reply Quote Deadbeat Report Post Thanks(0) Quote Reply Posted: 05 December 2008 at 7:59pm
	Tannoy is definitely OS... Tractrix would look a bit different. If you want OS, I believe S DeXter and I have spreadsheets on the computer. I use the Melhuish calculator for tractrix, it is available at rocketsciencecanada.com If you want any help, give us a shout, I've made round horns before.
	Away on extended leave.

minaximal Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Old Croc Joined: 26 September 2004 Location: United Kingdom Status: Offline Points: 1552	Post Options Post Reply Quote minaximal Report Post Thanks(0) Quote Reply Posted: 08 December 2008 at 11:35pm
	i would go for the os option if you can as a bit more fun for a home hifi project, but horn response will do tractrix, you just need to dump the the numbers as a .scr into solidworks or autocad, i could also do the same with aj horn.
	'My only law is the river breeze, That takes me to the open seas, If I could choose the life I please, Then I would be a boatman' http://www.metaacoustics.com

Paulo Duto Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 06 January 2005 Location: Brazil Status: Offline Points: 116	Post Options Post Reply Quote Paulo Duto Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 1:19am
	Hi Volvotreter site in the download section has what you are looking for. Also reproduces some Bruce Edgar articles on tractrix subject... Regards,
	Paulo Duto

mykey Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 18 August 2005 Location: UK/Indonesia Status: Offline Points: 9672	Post Options Post Reply Quote mykey Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 7:19am
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biotec Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 07 June 2004 Location: United Kingdom Status: Offline Points: 2867	Post Options Post Reply Quote biotec Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 9:22am
	cheers for all the help. Deadbeat or Dexter can you link me up with the OS spreadsheet? I'll PM you my email address if you cans end it over. What are the basic differences in dispersion, cut-off and response between OS and tractrix horns and what makes one more suitable than the other for hi-fi use?
	me so horny, me love you long throw.

Deadbeat Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Old Croc Joined: 12 March 2008 Location: Singularity Status: Offline Points: 3162	Post Options Post Reply Quote Deadbeat Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 10:43am
	Will do. PMs now empty. Tractrix was used to create a hemispherical wavefront at the mouth (in comparison to exponential, etc) and so reduce reflections. This only happens in round horns really, mind. You don't really have directivity control in a round horn. Look at polars. You can superimpose it onto a radial horn or diffraction slot, or Mantaray, but it's a bit pointless imo - you lose the no reflection effect to gain a bit of nominal dispersion (in the biradial case). This is a part of old school horns which were primarily designed to load the compression driver, to couple it with the air. Will post again on OS and conical horns, have to go.
	Away on extended leave.

darkmatter Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 26 February 2005 Location: LDN Status: Offline Points: 2183	Post Options Post Reply Quote darkmatter Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 1:21pm
	If you're making OS waveguides for a BMS coaxial gimme a shout, especially if you're getting anything machined, cos getting another pair might reduce costs and I reeeaally want some!! Don't know of any proper OS waveguides in this country so I've never heard them, but I'm curious. An OS waveguide would supposedly suffer from less distortion and plugged with foam you can reduce high order modes. Make it nice and big to get a 1K crossover with polar response matching the horn / driver below it and you're on to a winner apparently. So does anyone know what the exit angle on the BMS co-axs is? As a rough guide, a 15" waveguide on a 1" exit CD will give a 900Hz x-over. At this size it matches the polar response of a direct radiating 15". http://www.gedlee.com/downloads/Cum%20laude.pdf

davey t Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Registered User Joined: 11 March 2004 Location: Bristol UK Status: Offline Points: 1298	Post Options Post Reply Quote davey t Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 1:30pm
	it was nice hearing those tannoys at plaza. The guy was really sound too - gave us free beer and t-shirts! It definately wasn't tractrix, looked almost conical but probably OS as you say. I thought about looking into the bms coax drivers but read a few off-putting reviews on psw or diy audio forum. But then again it all depends on the waveguide and crossover etc. Good luck, i can't wait to see some of these diy.
	Minirig portable soundsystem movement

Deadbeat Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Old Croc Joined: 12 March 2008 Location: Singularity Status: Offline Points: 3162	Post Options Post Reply Quote Deadbeat Report Post Thanks(0) Quote Reply Posted: 09 December 2008 at 2:38pm
	Waveguides. They aren't as much concerned with loading - but directivity. The main difference between a WG and a conical horn is that the conical one does not alter the wavefront. Other WGs like the OS turn the planar wavefront into a round one, then continue roughly conically. I suggest you read the geddes' summary linked as well. It summarizes HOM and his approach. Basically: 1) The room is the reason you want CD (in his paper) 2) HOM contributes to the horn sound, these are waves that don't propagate down the horn. 3) The OS Waveguide is the best way to get a planar wave to a round one without much HOM 4) the plug attenuates HOM generated by the comp and the WG The only thing is that...while a lot of comps are designed to give a planar wave...some don't. For example, I think Danley use a BMS that gives a pretty round wavefront in one of their conical horns. Still the benefit of lessened HOM. You can also see the new celestions with their 'curved wavefronts' which may be good for a conical, no? The reason why Geddes' doesn't like the BMS coaxes is because they have the xover frequency in the wrong place. Edited by Deadbeat - 09 December 2008 at 2:39pm
	Away on extended leave.