should I build this one?

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

front loaded 1segment horn, for 150hz 1000hz use.
loaded with b&c 12mh32 (i will use 4 of them for each colum).

25kg each circa to be lift at 1,9mt circa....

Its my very first horn building so id like to understand howto not waste time,
these are the sims result:

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
_Natty_ Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 01 April 2007 Status: Offline Points: 644	Post Options Post Reply Quote _Natty_ Report Post Thanks(0) Quote Reply Topic: should I build this one? Posted: 03 September 2018 at 2:26pm
	front loaded 1segment horn, for 150hz 1000hz use. loaded with b&c 12mh32 (i will use 4 of them for each colum). 25kg each circa to be lift at 1,9mt circa.... Its my very first horn building so id like to understand howto not waste time, these are the sims result:

Keen Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 30 May 2011 Location: Brisbane, Aus Status: Offline Points: 1198	Post Options Post Reply Quote Keen Report Post Thanks(0) Quote Reply Posted: 03 September 2018 at 11:46pm
	smaller rear chamber will smooth out response. Also go into options and choose directivity plot to see on axis response. Changes quite a bit in good way, go 20 off axis

fatfreddiescat Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1061	Post Options Post Reply Quote fatfreddiescat Report Post Thanks(0) Quote Reply Posted: 04 September 2018 at 9:09am
	Very similar to the TDA MT121 and half of the speakerplans MT122

_Natty_ Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 01 April 2007 Status: Offline Points: 644	Post Options Post Reply Quote _Natty_ Report Post Thanks(0) Quote Reply Posted: 04 September 2018 at 9:34am
	you are right...the inspiration start from smtp tda version, but big moods on every part. the question is for people that have build horns of this size, and if they found more problems than db or long trow.... Im afraid by the tiny troath, and if is good to put or not a one more expansion at 3/4 lenght of the horn path.. even im curios about the back chamber that is not so little but seems to have best result over this simulation!

Keen Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 30 May 2011 Location: Brisbane, Aus Status: Offline Points: 1198	Post Options Post Reply Quote Keen Report Post Thanks(0) Quote Reply Posted: 05 September 2018 at 6:01am
	can you show us the input data?

_Natty_ Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 01 April 2007 Status: Offline Points: 644	Post Options Post Reply Quote _Natty_ Report Post Thanks(0) Quote Reply Posted: 05 September 2018 at 11:00am
	not so complicated back chamber 22l circa back panel 19 cm circa s1 under 200sq cm s2 around 1500sq cm circa con 52cm circa

Keen Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 30 May 2011 Location: Brisbane, Aus Status: Offline Points: 1198	Post Options Post Reply Quote Keen Report Post Thanks(0) Quote Reply Posted: 06 September 2018 at 7:27am
	s1 200 is fine don't worry about the second expansion at 3/4 length. but give the mouth termination a lip

_Natty_ Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 01 April 2007 Status: Offline Points: 644	Post Options Post Reply Quote _Natty_ Report Post Thanks(0) Quote Reply Posted: 06 September 2018 at 9:13am
	what you mean by "but give the mouth termination a lip" the horn lenght is based in: -cuttoff -back chamber lenght + horn lenght < 75cm (is the es18bph lenght so to be fit best to stay under this lenght) some one suggest me to give a second expansion at 3/4 of the horn lenght like you said, but to me there is no such help in the lower part of the response (under 400hz) that justify the big works to do a second expansion... the carpenter was very happy when I show him just a straight horn instead of many expansion style... even to me expansion helps directivity that is not such needs for a horn like this one that is cutted at 1khz. For s1 better result is under 200, from 80 to 170cm^2, so very small, and for that reason maybe design a troath reduction could be good... but I've no idea if I simply cover the mouth with planar reduction or a phase plug... where I can find some reads about that? The s2 is designed like that because is the area of the back chamber too, so less wood, less problem to fit the horn in the box... and ive seen that again due the low upper cutoff there is not such advantage to make it larger. final step is the back chamber, many said small volume, but mine sims give me best result with something around 20l, and is even simpler to build! it will be an expensive project for me, so before cutting id like to be confident in what i project on paper. many thanks

snowflake Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3097	Post Options Post Reply Quote snowflake Report Post Thanks(0) Quote Reply Posted: 06 September 2018 at 3:14pm
	if you want to avoid beaming and fingering in the off axis resonse you need to double the flare rate in the last section of the horn. I think it was Keele who did a good paper about this. It does take up more volume to do this. you might want to consider how you are arraying them and how that will work. On some of my boxes I had more expansio in the vertical axis but not on the horizontal. I thought I could get rid of the fingering by using the right splay angle to get the fingers to fill in the gaps of the neighbouring box. I didn't get it quite right but I think it's an approach that might work if tweaked.

_Natty_ Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 01 April 2007 Status: Offline Points: 644	Post Options Post Reply Quote _Natty_ Report Post Thanks(0) Quote Reply Posted: 07 September 2018 at 8:23am
	please can you link me this paper, thanks!

odc04r Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5483	Post Options Post Reply Quote odc04r Report Post Thanks(0) Quote Reply Posted: 07 September 2018 at 9:17am
	I think the paper in question was probably Keele - "What's so sacred about exponential horns". Towards the end of it he proposed a dual flare horn from exponential to conical. Haven't read it in a while but was probably about a smoother termination to free air and less reflections at the air/mouth abrupt boundary. http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1975-05%20AES%20Preprint)%20-%20Whats%20So%20Sacred%20Exp%20Horns.pdf