Home » Sponsored » Pi Speakers » Can you guess horn cut-off by dimension only?
Can you guess horn cut-off by dimension only? [message #53245] Sun, 22 February 2009 21:28 Go to next message
Chris R. is currently offline  Chris R.
Messages: 82
Registered: May 2009
Viscount
Wayne,
If all you know about a horn is it's dimensions, can you make a decent guess as to it's lower cut-off freq? I'm looking for some
bargin horns (Goldwood from PE) to cover 800Hz-5KHz. I picked up a pair of empty Cornwall cabinets and already have
everything except mid-horns to get them going.
Thx, Chris


Re: Can you guess horn cut-off by dimension only? [message #53248 is a reply to message #53245] Mon, 23 February 2009 11:17 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

When horn length = 1/4λ, you can expect output to drop off rapidly under that frequency. The smoothness of response above that frequency, directivity, efficiency, etc. is determined by the rest of the horn's features.


Re: Can you guess horn cut-off by dimension only? [message #53252 is a reply to message #53248] Mon, 23 February 2009 12:30 Go to previous messageGo to next message
Chris R is currently offline  Chris R
Messages: 133
Registered: May 2009
Master
Thanks Wayne,

So, for a JBL 2370A, they are claiming a cut-off of 630Hz with a depth (length) of ~7". So... 630Hs is a wavelength of 21.6",
so this horn is ~.31 of the wavelength at spec, right? Can I conclude that other horns with similar depths and dimensions
will have similar specs? I realize there's a *lot* of generalization in that statement.

90 x 40 dispersion
Full horn loading to 630 Hz
Dimensions: 6-7/8" H x 17-1/2" W x 6-7/8" D

Thx, Chris


Re: Can you guess horn cut-off by dimension only? [message #53254 is a reply to message #53252] Mon, 23 February 2009 13:13 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

1/3λ is a fairly safe cutoff frequency estimate. 1/4λ would be a drop dead value, one that I would not expect any acoustic loading below. 1/2λ is where efficiency gains are seen, with the highest efficiency range above that frequency. Between 1/4λ and 1/2λ, there are usually some ripples in response, sometimes mitigated by other horn features like flare profile and rear chamber size.


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