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Horn for X15
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Phil.2008 View Drop Down
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Points: 331 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil.2008 Quote  Post ReplyReply Direct Link To This Post Posted: 04 February 2009 at 8:27pm
Do you mean that because the port's against the cab wall it effectively has the properties that a longer port would have that's mounted away from the wall and joined solely to the baffle? And what does telling WinISD that the ports are flanged actually mean to it?

Thx

Edit... don't worry I've found a tutorial on it now...


Edited by Phil.2008 - 04 February 2009 at 9:03pm
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ceharden View Drop Down
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Points: 11851 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 04 February 2009 at 11:26pm
Good good, probably a better explanation than I'd give anyway!
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Phil.2008 View Drop Down
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Points: 331 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil.2008 Quote  Post ReplyReply Direct Link To This Post Posted: 05 February 2009 at 8:36am
Maybe you'd like a read? http://mobile.jlaudio.com/support_pages.php?page_id=165

Based on this I think if I specify one flared end in WinISD and put the port depth in as "plus half h" I should be OK.  What do you think?

Loved the comment about external port tubes :)
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Tony Wilkes View Drop Down
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Points: 4835 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 05 February 2009 at 8:42am
Also do not forget that if the box is to be used in free space or not within say 300mm of a rear wall that the ports can just as easily go on the back.

Tony
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ceharden View Drop Down
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Points: 11851 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 12:08am
Yup, that's a good tutorial, not one I've seen before.

That calculation should work but from my experience I would still recommend that you err on the high side with the tuning.
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Phil.2008 View Drop Down
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Points: 331 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil.2008 Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 8:58am
I've been reminded about the low crossover point possible (1.3k) with the BMS 4544 1" and the more I think about it the more sense it seems to make.  It's gonna work out cheaper, i can use a nice 18sound horn (XT1086) and I don't have to redesign the box.

My only reservation is that the 18sound website states that the horn has a "usable frequency range" of above 800Hz and a lowest-recommended crossover of 1200Hz.  This runs contrary to what I've learned about horns in that you should only crossover at least 1 octave above the horn's -3dB cutoff. 

The question is, is 800Hz the horn's -3dB cutoff or are they quoting something different?  Will the xt1086 happily cross at 1.3k?  Isn't there some way you can work out a horn's lowest usable frequency from its depth or something?

Thanks
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ceharden View Drop Down
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Points: 11851 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2009 at 9:37pm
Well I actually cross from my 15" to the 1.4" at 1.5kHz.  So you don't necessarily need to go right down to 1.3kHz.   I used to run a pair of DE250's down to 1.6kHz on the XT1086 above an SN15MB.  While that sounded ok, going to a larger diaphragm compression driver was a big improvement even though the crossover point didn't change much.  The difference was most noticable at higher volumes where the larger CD had more headroom.

It's a tough one to call.  The 1" CD + XT1086 is definitely the easier option.
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Tony Wilkes View Drop Down
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Points: 4835 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 09 February 2009 at 4:01pm
Originally posted by ceharden ceharden wrote:

Well I actually cross from my 15" to the 1.4" at 1.5kHz.  So you don't necessarily need to go right down to 1.3kHz.   I used to run a pair of DE250's down to 1.6kHz on the XT1086 above an SN15MB.  While that sounded ok, going to a larger diaphragm compression driver was a big improvement even though the crossover point didn't change much.  The difference was most noticable at higher volumes where the larger CD had more headroom.

It's a tough one to call.  The 1" CD + XT1086 is definitely the easier option.



Th big difference with the BMS drivers is that they actually have an Xmax, that is that the surround allows real movement of the cone unlike the sort of "quiver" type movement that you get on conventional comps. This also gives them a very high peak rating compared to other types.

Tony
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