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
Wayne Parham Messages: 18686 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.
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
Wayne Parham Messages: 18686 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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