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Subhornor bass horns only [message #18149]

Mon, 26 September 2005 08:04

adavis464
Messages: 64
Registered: May 2009

Viscount

Horn expansion is the volume of the expansion the important part.In other words when shape start to effect the response.I used Mcbean to calculate the expantion of a sub horn using JBL2240 I am limited to 21" in width and let the expansion from there.At what point if I made it lets say 18" would this be worst or no different.Its built Ijust need to make th back chamber and stand.It's 5'by5'21" wide regards Tim

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Re: Subhornor bass horns only [message #18150 is a reply to message #18149]

Mon, 26 September 2005 12:34

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

The truth is, when a segment expands with a straight-sided expansion on one side and no expansion on the other, it is really a parabolic expansion, not conical. Conical expansion requires linear expansion in both axis. Exponential or hyperbolic requires even more. But by using several sections, you can approximate the flare you want, even with straight side walls. Also, there will be a notch in output at the frequency where the side wall distance is 1/4 wavelength, so consider this when choosing a crossover frequency. If it's a basshorn, it probably won't be an issue, and may help increase rolloff above the passband.

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I didn't know about the parabolic expansion [message #18151 is a reply to message #18150]

Mon, 26 September 2005 18:50

adavis464
Messages: 64
Registered: May 2009

Viscount

That's very interesting.I have another question about covering the mouth of the sub see I have a cat and I think she's going to love it in there ;)So grill cloth it is.What effect will it have.I try to measure and post the data and pics.Regards Tim

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Re: I didn't know about the parabolic expansion [message #18152 is a reply to message #18151]

Mon, 26 September 2005 21:25

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

I think the grille cloth will probably be just fine. I've heard of people using a metal grille mesh to keep debris (beer bottles, cigarette butts and ashtrays) out of horns used in clubs. I think that's just fine too, but I think it must ultimately reduce mouth area. Some meshes have probably 50% of the area covered, so that's something to think about on horns with limited mouth area to begin with. But in a club, I think it's probably a good idea and boundary loading will help offset the impact of reduced mouth area. If the horn is designed for halfspace, indoor boundary conditions will probably more than offset the reduction of mouth area. Still, it's something to think about if you're looking at options.

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