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Hornresp question

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julienb34 View Drop Down
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    Posted: 22 August 2006 at 9:30am
Why Hornresp seems to cut the highs in the SPL response?

The same design in AJhorn demo (exponential) doesn't cut the high as Hornresp. Is there something to do in hornresp?

Thank.
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Mircea Bartic View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mircea Bartic Quote  Post ReplyReply Direct Link To This Post Posted: 22 August 2006 at 9:57am
I believe that hornresp does not take into acount tha response of the driver in direct radiator mode.
The plot represents the bandpass response (theoretical)

Hornresp was initially designed for basshorns
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tb_mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 23 August 2006 at 7:47pm
I Guess you could sum the driver frequency response as measured in 2pi from the manufacturer. Note that strong drivers with low Qes have a nice rising response for a higher frequency F3
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ceharden View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 24 August 2006 at 4:23am
Might this also be to do with Hornresp plotting the power response ie averaged across all radiation angles.  Try looking at the on-axis response? (Tools -> Directivity -> 0deg)

I might be completely wrong....
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Centauri View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2006 at 11:38am
I believe Hornresp's maths includes the mass-rolloff equations, which some now doubt as being correct.  The directivity tool seems to exaggerate the top end, most likely because it models round horns with curved sides, which will have poor dispersion characteristics.  If you are building square straight-sided horns, then build-and-measure is the order of the day.

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Graeme
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james folkes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote james folkes Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2006 at 3:42am
Originally posted by ceharden ceharden wrote:

Might this also be to do with Hornresp plotting the power response ie averaged across all radiation angles.  Try looking at the on-axis response? (Tools -> Directivity -> 0deg)

ok, tried that... right, now this confused me significantly. what i really wasn't expecting was the 12dB incease over the previous plots, 12 frickin' dB man! i'm fiddling up some 12", 8" + 1" top boxes to accompany the project firewood bass bins and to try two ideas that might be relevant to the mid top project, what's good is that brought the output level of the 8" back in line with the 12" at full power (much higher actually), which is what i was expecting, other than that i'm just confused.

question for both you and greame, fast initial expansion to assist in top end response of horn... i've seen the phrase written down a few times, but i'm having difficulty equating it to my hornresp furtlings. could you please talk about this slightly more?

james.
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tb_mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 30 August 2006 at 11:29pm
James - You can use the autocalc thingie,and hornresp calculates the cutoff for each segment. Have you got MSN?
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james folkes View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote james folkes Quote  Post ReplyReply Direct Link To This Post Posted: 31 August 2006 at 4:44am
i thought that was the lower cut-off...

anyway, jamesatinddotst "at" hotmail.com is my msn thingumy, looking forward to having a natter!

james.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 02 September 2006 at 8:51am
Originally posted by james, ind.st james, ind.st wrote:

fast initial expansion to assist in top end response of horn... i've seen the phrase written down a few times, but i'm having difficulty equating it to my hornresp furtlings. could you please talk about this slightly more?

james.


This is a trick Bill Fitzmaurice uses to get a wider bandwidth from his horns.  If you have an exponential horn with a lower cutoff of say 200Hz, you will get a lot of gain at the lower frequencies but not much at the top end.  If you break the horn into 2 sections with the first exponential section with a cutoff of around 500Hz or more, then follow it with the second exponential section at 200Hz, you can get a bit more out of the top end.  The trick is juggling the frequencies and lengths of the two sections to get a reasonably smooth response.  Due to Hornresp's top end innacuracies, and the fact it does not take into account the measured response of the driver used, a lot of experimenting can be expected to get good results.

When looking at the directivity results from Hornresp, the high gains will only appear on axis, and the top end will fall off rapidly at off-axis angles.  If you are using a straight-sided horn for controlled directivity, these results will not mean anything.

Cheers
Graeme
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2006 at 3:54am
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