I've just been to your site, it does make more sense now I've seen the pics.cowanaudio said:
I'm almost ready to start cutting the wood but I want to be sure I've got everything right before I start. 
I was planning on building the older version with the 100mm throat, but still having the magnet facing out, due to the 100mm version appearing to give a better response in hornresp with my Eminence Magnum 12HO driver. Am I right in assuming the 100mm version has a lower compression ratio also due to the larger throat?
I noticed you used 25mm ply, which is really strong stuff so I'm guessing you used no bracing (I see no bracing is mentioned on your website)?
I couldn't get 25mm ply but I did buy some 18mm Baltic birch ply instead, so I'm tempted to add bracing... Is it worth increasing the volume of the box slightly in order to compensate for the volume filled by the bracing or is the volume of the bracing so small that it's not worth worrying about?
G'day again Mike
The last few boxes I've built have used bracing, and have benefited from them. The braces are easy to make in these boxes, measure or calculate the angle of the internal baffle and set the miter guide on your table saw to this angle. Now make a cut through the center of a piece of ply that is 18mm smaller than your internal front-back dimension of your tapped horn. This will give you a brace that fits perfectly. I usually put two or three pairs of short braces along the path of the horn. If you are using a hand held saw, straight edge and clamps to cut your sheets, a similar method works. Just lay out your dimensions on your sheet, clamp up your straight edge and run your cut.
Bracing really is beneficial in a permanent box.
Cheers
William Cowan
The last few boxes I've built have used bracing, and have benefited from them. The braces are easy to make in these boxes, measure or calculate the angle of the internal baffle and set the miter guide on your table saw to this angle. Now make a cut through the center of a piece of ply that is 18mm smaller than your internal front-back dimension of your tapped horn. This will give you a brace that fits perfectly. I usually put two or three pairs of short braces along the path of the horn. If you are using a hand held saw, straight edge and clamps to cut your sheets, a similar method works. Just lay out your dimensions on your sheet, clamp up your straight edge and run your cut.
Bracing really is beneficial in a permanent box.
Cheers
William Cowan
^
Thanks for the angle cutting tip, that is sounds a lot easier than cutting each brace on it's own which is what I had to do when building my autotuba. This will be a permanent box, I'll definitely go for bracing. I'm guessing the main benefit is strength but are there any other benefits?
Here is where I intend to put the braces, one every 500mm, each one is 160mm long:
I found my wood was actually 16mm thick after measuring it, so Sketchup turned out to be pretty useful in working out what size wood to cut while keeping the same internal dimensions. I've also modelled both versions of the horn (again) in hornresp and found actually the 4.8mm throat version gives better results with my driver after all so I'm going for the new version of the enclosure. If can post the sketchup file is anybody needs it?
I really can't wait to get started now, hopefully my next post should have some pictures...
Thanks for the angle cutting tip, that is sounds a lot easier than cutting each brace on it's own which is what I had to do when building my autotuba. This will be a permanent box, I'll definitely go for bracing. I'm guessing the main benefit is strength but are there any other benefits?
Here is where I intend to put the braces, one every 500mm, each one is 160mm long:
An externally hosted image should be here but it was not working when we last tested it.
I found my wood was actually 16mm thick after measuring it, so Sketchup turned out to be pretty useful in working out what size wood to cut while keeping the same internal dimensions. I've also modelled both versions of the horn (again) in hornresp and found actually the 4.8mm throat version gives better results with my driver after all so I'm going for the new version of the enclosure. If can post the sketchup file is anybody needs it?
I really can't wait to get started now, hopefully my next post should have some pictures...
Question, William: Did you have a problem with any of your boxes buzzing?
It's not hard to visualize where the weak areas are. The left-most brace supports the speaker edge and the edge of the mouth, and the right-most brace supports the flare edge. A center brace wasn't needed.
I cut my braces on my table saw using a sled, and all four fit first-time. I cut all the 16 inch wide pieces in one setup, and the box went together with TiteBond II only, no leaks. I thought about putting a cross-brace in the mouth, but wanted to be able to remove the driver. It hasn't proven to be a problem.
The goal is to build a stiff box with good damping. If it's stiff, it'll be strong enough. If it vibrates well above passband, no one will ever know.
It's not hard to visualize where the weak areas are. The left-most brace supports the speaker edge and the edge of the mouth, and the right-most brace supports the flare edge. A center brace wasn't needed.
I cut my braces on my table saw using a sled, and all four fit first-time. I cut all the 16 inch wide pieces in one setup, and the box went together with TiteBond II only, no leaks. I thought about putting a cross-brace in the mouth, but wanted to be able to remove the driver. It hasn't proven to be a problem.
The goal is to build a stiff box with good damping. If it's stiff, it'll be strong enough. If it vibrates well above passband, no one will ever know.
Attachments
G'day Don
That picture that Mike attached to his last post is exactly how I brace my tapped horns. No problems with buzzing, even in the unbraced versions. The unbraced cabinets do flex a bit, and I think this reduces output a bit, perhaps also increasing THD a little. Not sure if it's all in my head, but I like the sound of the braced versions better.
BTW I have BAD problems with my house buzzing with some of these tapped horns
Maybe I need to brace that too
Cheers
William Cowan
That picture that Mike attached to his last post is exactly how I brace my tapped horns. No problems with buzzing, even in the unbraced versions. The unbraced cabinets do flex a bit, and I think this reduces output a bit, perhaps also increasing THD a little. Not sure if it's all in my head, but I like the sound of the braced versions better.
BTW I have BAD problems with my house buzzing with some of these tapped horns
Maybe I need to brace that too Cheers
William Cowan
I spent 30 years in aerospace, designing gear that had to go thru Shake-N-Bake (vibration & thermal cycling). We would take a piece of gear in to test, and the technician would tell us what part would fail first. They were almost always right. Sometimes, I wish I had one of those techs around.
I said, "A center brace wasn't needed" as my box is only 1.5 meters (60") long. I wouldn't build a seven foot box without two more braces.
After your box is assembled, take a small hammer and tap on it. Any place that sounds hollow or rings should have had a brace. Another trick that helps, is to lay it down, and sprinkle salt on the plywood while it's playing. The areas where the salt won't stay put is where you needed more bracing.
I said, "A center brace wasn't needed" as my box is only 1.5 meters (60") long. I wouldn't build a seven foot box without two more braces.
After your box is assembled, take a small hammer and tap on it. Any place that sounds hollow or rings should have had a brace. Another trick that helps, is to lay it down, and sprinkle salt on the plywood while it's playing. The areas where the salt won't stay put is where you needed more bracing.
having read the whole thread, still some questions and unsettled thoughts...
about hornresp, if 2 drivers used, what values to double?
thinking about upwards opening horn with drivers symmetrically left and right of the "throat area".. then the horn splitting into two and opening again downwards.. (like most here, but take mirror image and attach, forming a double sized one with shared first half of the horn.)
is there any reason to assume any cancellation over the high frequency erm.. resonances with that design -if both ends shared same airspace before exiting cabinet? also possibility here to make horns differ a bit in lenght. hmmm.. just ficured that last one out, might actually do something
and is it that the tapped horn works with quite of delay? i mean, cone begins to move forward -air rushes through the horn - somewhat cancelling with the opposing - and finally joins at the exit with whatever is then coming out of the driver with the delay of "L23"? is this the very reason for desing needing most xmax with those impulses, as there is no futher back wave loading yet?
then how about the level of the first "impulse" (sorry, can't seem to find exact word here, beginning wave or just one impulse) how attenuated compared to longer lasting? and how about that excursion aspect, how much more in the beginning and less continuosly, compared to simulation that is? anyone measured these matters or even just have guesstimates to throw here?
oh, and any measurements of Don's project? been planning with same drivers some time now.. the Kappalite 3015lf. also a midbass with Governor quitar drivers that i actually also have. with latter and their minimalistic excursion capabilities the required peak would be even more interesting to know. (peak, in the sense of what driver has to handle with those forementioned impulses in tapped horn)
these governors also make me wonder -the efficiency (in the sense of voltage in, spl out) don't really seem improved over casual reflex cabinet, even as the driver seems to simulate very well in ~60-80hz tuned tapped horn, just a couple of desibels more at max.
so, the main question was: if somebody has anything to tell about what is the actual excursion in impulses and longer waves, compared to simulated, then be my guest perhaps even some sort of guideline could be done here -a correcting factor.
thanks.
-Samuli
about hornresp, if 2 drivers used, what values to double?
thinking about upwards opening horn with drivers symmetrically left and right of the "throat area".. then the horn splitting into two and opening again downwards.. (like most here, but take mirror image and attach, forming a double sized one with shared first half of the horn.)
is there any reason to assume any cancellation over the high frequency erm.. resonances with that design -if both ends shared same airspace before exiting cabinet? also possibility here to make horns differ a bit in lenght. hmmm.. just ficured that last one out, might actually do something
and is it that the tapped horn works with quite of delay? i mean, cone begins to move forward -air rushes through the horn - somewhat cancelling with the opposing - and finally joins at the exit with whatever is then coming out of the driver with the delay of "L23"? is this the very reason for desing needing most xmax with those impulses, as there is no futher back wave loading yet?
then how about the level of the first "impulse" (sorry, can't seem to find exact word here, beginning wave or just one impulse) how attenuated compared to longer lasting? and how about that excursion aspect, how much more in the beginning and less continuosly, compared to simulation that is? anyone measured these matters or even just have guesstimates to throw here?
oh, and any measurements of Don's project? been planning with same drivers some time now.. the Kappalite 3015lf. also a midbass with Governor quitar drivers that i actually also have. with latter and their minimalistic excursion capabilities the required peak would be even more interesting to know. (peak, in the sense of what driver has to handle with those forementioned impulses in tapped horn)
these governors also make me wonder -the efficiency (in the sense of voltage in, spl out) don't really seem improved over casual reflex cabinet, even as the driver seems to simulate very well in ~60-80hz tuned tapped horn, just a couple of desibels more at max.
so, the main question was: if somebody has anything to tell about what is the actual excursion in impulses and longer waves, compared to simulated, then be my guest
perhaps even some sort of guideline could be done here -a correcting factor.thanks.
-Samuli
mike hunt, do u have msn? add me, pfb_sharpy@hotmail.co.uk
i liked the sims for the lab 12 driver in the horn i tried to design, but i had the same problem as you, not knowing how to convert the horn response inputs to a real life design...
but anyway i suppose i could go with the 30hz horn as its still usable down to 25hz
yer so add me if u like and we can see what we can come up with
i liked the sims for the lab 12 driver in the horn i tried to design, but i had the same problem as you, not knowing how to convert the horn response inputs to a real life design...
but anyway i suppose i could go with the 30hz horn as its still usable down to 25hz
yer so add me if u like and we can see what we can come up with
If you're ever near the south west, you're more then welcome to hear the horn once it's built.Naudio said:
I'm at work right now so I have access to these files at the moment - I'll post them when I get home. I do have MSN but I'm not on there very much as I'd rather be cutting wood than clicking a mouse.
I'll add you next time I'm on tho.Your Lab12 driver is quite a different beast to my Magnum 12HO, and it may not work too well in William Cowan's 30Hz enclosure. Maybe try it out in hornresp?
I think there has already been a good enclosure posted in this thread for the Lab12 driver, have a look back a page or two and I think there may even be a complete box design waiting to be built.
In fact I suggest you go thru the whole thread (and the hornresp helpfile). I didn't have a clue about hornresp before I read this thread, but now I've got to grips with the basics at least.As far as construction goes, a tapped horn is pretty simple when compared to something like the Lab Horn, so even if it doesn't turn out perfect the first time, it's not hours and hours of work down the drain...
EDIT: I have have a rat shack meter also, how do you calibrate it?
As promised, hornresp parameters and I've done a mega high res shot of the model with as many measurements as possible.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
help folding this one
hey
I wondering if I could get some help folding this design. It is not a linear taper.
I also had a question about the throat. I have noticed that a few of the example designs show the speaker completely exposed. Is this because they are using the cross-sectional area as the throat? I ask because as I wait for my other 9515's and of corse some more money for the wood I wannted to get it cleared up because of the compensation for the 9515 25 mm xmax.
thanks
the 8 inch design (for folding) is attached
hey
I wondering if I could get some help folding this design. It is not a linear taper.
I also had a question about the throat. I have noticed that a few of the example designs show the speaker completely exposed. Is this because they are using the cross-sectional area as the throat? I ask because as I wait for my other 9515's and of corse some more money for the wood I wannted to get it cleared up because of the compensation for the 9515 25 mm xmax.
thanks
the 8 inch design (for folding) is attached
