Hmm, there's no context provided. I'm just a newbie but here's what I think the gurus would say. To build a BLH you ultimately need:
1. the driver and specs
2. your target for low-end response (e.g., 50Hz?)
3. whether the horn is front-firing or rear-firing
4. size of the chamber
5. size of the throat
6. size of the mouth
7. length of the path
8. the flare rate (exponential?)
Here's a simplistic attempt at an explanation. (In reality, the gurus wouldn't do it quite this way but it's just an example.)
Imagine you have a little bass reflex box. And attached to the BR's vent is a gigantic horn. How long? How big? What shape? Let's find out.
First figure out the tuning of the BR. Let's say the box is tuned to 200Hz. So simplistically, we're going to "feed" the horn with 200Hz and below. Down to what frequency? You have to choose that. Let's say 50hz. That means the vent will feed the horn with 200Hz and below.
Now you are committing to the mouth's size and length (dictated by the size of the 50Hz wavelength). There's so much more as well, e.g., the quarter-wave action (additional low frequency resonance below the horn's proper tuning).
So really, you have to design it on paper, then use MJK for testing purposes. MJK will tell you whether it's any good. I would ignore those graphs until you have really fleshed out your design with many, many iterations on paper and in MJK.
1. the driver and specs
2. your target for low-end response (e.g., 50Hz?)
3. whether the horn is front-firing or rear-firing
4. size of the chamber
5. size of the throat
6. size of the mouth
7. length of the path
8. the flare rate (exponential?)
Here's a simplistic attempt at an explanation. (In reality, the gurus wouldn't do it quite this way but it's just an example.)
Imagine you have a little bass reflex box. And attached to the BR's vent is a gigantic horn. How long? How big? What shape? Let's find out.
First figure out the tuning of the BR. Let's say the box is tuned to 200Hz. So simplistically, we're going to "feed" the horn with 200Hz and below. Down to what frequency? You have to choose that. Let's say 50hz. That means the vent will feed the horn with 200Hz and below.
Now you are committing to the mouth's size and length (dictated by the size of the 50Hz wavelength). There's so much more as well, e.g., the quarter-wave action (additional low frequency resonance below the horn's proper tuning).
So really, you have to design it on paper, then use MJK for testing purposes. MJK will tell you whether it's any good. I would ignore those graphs until you have really fleshed out your design with many, many iterations on paper and in MJK.
He was busily posting on the main loudspeakers section a little while ago asking if anyone could provide him with the old sheets, claiming he could not afford $25 to buy them off Martin due to the poor exchange rate. And while I sympathise about duff exchange rates generally, that's not a justification for not paying. If you can't afford it, you can't afford it. Tough. There are lots of things that I would like that I can't afford, so, oddly enough, I live without them.
As Mr Bigcatdiary doesn't seem the least bit willing to do any background reading on horn design either, not even of free material on the 'net (God forbid he should consider buying a book), I for one, have decided to ignore him, on the basis that I have little inclination to help people who don't make an attempt at helping themselves. The fact that he's now somehow aquired Martin's worksheets without coughing up the required sum only increases my less-than-charitable sentiments.
As Mr Bigcatdiary doesn't seem the least bit willing to do any background reading on horn design either, not even of free material on the 'net (God forbid he should consider buying a book), I for one, have decided to ignore him, on the basis that I have little inclination to help people who don't make an attempt at helping themselves. The fact that he's now somehow aquired Martin's worksheets without coughing up the required sum only increases my less-than-charitable sentiments.
Scottmoose said:
when i said i can't afford it? just meant very inconvenient to transfer. dunno y u said so,as i just liked to get it anyway to save some bucks. ****!
and the original old sheet was free, i just got the old sheet from sb else, i did't break any rule. on the other hand, he didn't say to transfer old sheet is prohibited. if he emphersise so, i promise to delete it. big deal~
so, if everybody thought i was wrong, ok,now i promse to pay him anyway .
stop distorting my mean!! thx!
MJK said:
yes, just got the old sheet from another person from this forum, that y on my post just ask for old sheet. thx for understanding.
what a pity that u stopped. like to ask y if u dont mind~
next month i'll go back to china, i hope that i can get a new sheet from u, money can transfer freely there. bcoz i found ur work sheet is more understandable for me.
Hi Martin, I really appreciate your models. And I appreciate that you did this for knowledge, not for the very small sums involved. I also imagine that your free time was probably sorely taxed due to the time spent managing the licensing.
Thank you for everything. I have had much more fun than I ever hoped, and have learned more than I could have imagined.
Thank you for everything. I have had much more fun than I ever hoped, and have learned more than I could have imagined.
rjbond3rd said:
For almost two years I did not complete a single set of speakers. I started a bunch of stuff but never had the time or energy to finish anything. Continuously upgrading the worksheets and answering question took most of my free time. I probably spent an hour or two a day, seven days a week, trying ot stay on top of the e-mail and forum questions.
Thank you, learning was always the ultimate goal. The worksheets and my methods worked for some people but unfortunatley did not work for others. I don't think it had anything to do with experience or technical background, it either clicked or did not click.
Just because I have discontinued the worksheets does not mean I have stopped working on new ideas and designs. I hopefully now have more time to pursue and document whatever I dream up.
rjbond3rd said:
1 fs=64Hz, Vas=6.09, Qts=0.956, Bl=3.15, Sd=86.6cm^2
Sthroat=1.0Sd, Smouth=10.9Sd.
Lhorn=60in, linear horn shape.
2 low freq response as low as can get.
3 planning to make rear firing.
made a sample of carton, with small driver, due to any reasons, nothing evidently can be found except enlargement in spl.
MJK said:
what i pity for that, or can buy permanent licence for personal use?
Hi bigcatdairy,
To wrap this up, here are some links that I've found useful. The first two are equations, the rest are for software:
http://ldsg.snippets.org/HORNS/design.html
http://rocketsciencecanada.com/rocketsciencecanada/Sound/Horns/Info_SizeShape.asp
http://mywebsite.bigpond.com/dmcbean/
http://www.randteam.de/AkAbak/Index.html
http://www.aj-systems.de/indexe.htm
Best of luck! Post pictures when you can.
To wrap this up, here are some links that I've found useful. The first two are equations, the rest are for software:
http://ldsg.snippets.org/HORNS/design.html
http://rocketsciencecanada.com/rocketsciencecanada/Sound/Horns/Info_SizeShape.asp
http://mywebsite.bigpond.com/dmcbean/
http://www.randteam.de/AkAbak/Index.html
http://www.aj-systems.de/indexe.htm
Best of luck! Post pictures when you can.
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