My.... what big horns you have.

[ooteedee]

Why are Klipsh mid range horns so much longer than the horn lenses you often see nowadays?

[Colin]

like what?

[djk]

To go lower.

The Fc on a K400 is about 240hz.

[WMcD]

Well, I think Fc for the K-400 is around 271.2 Hz. That is based on the Lamed of 2.75 inches. Lamed is the distance in which the area doubles. But not to quibble.

The K-Horn bass unit stops working well at about 400 Hz on the high end, so you need a midrange horn which will go down that far. Frequency response in low Hz requires larger horns even in the midrange.

OTOH, it is not difficult to get a direct driver bass bins to go up to 800 or 1600 Hz. If you need a midrange to take over from there, it can be much smaller.

The killer here is that horns do "scale". But for every octave of bass response, most dimensions have to double. 1600 Hz is one size, going to 800, you double linear size, then at 400 you have to double again, meaning four times linear size.

Those Hz numbers are octaves.

Consider that bulk (volume) goes up as the cube of a linear dimension.

There is an exception to the scaling rule. The driver/throat size doesn't have to scale. Generally this means that if you are not trying to squeeze the bass response of the midrange horn down to the very lowest possible, you do wind up with a more compact midrange horn.

There is some math to this. Essentially if you shrink the horn and not the driver, then the horn can be shorter because you don't have to "grow" the area of the horn quite a much from the small end. It is already, relatively, "large" because of the non-scaled driver.

Suffice to say that if you're under the gun of getting even another half octave of bass out of horn, the numbers regarding linear size start running up quickly. Bulk goes up even faster.

Gil

[djk]

"Well, I think Fc for the K-400 is around 271.2 Hz. That is based on the Lamed of 2.75 inches. Lamed is the distance in which the area doubles. But not to quibble."

While this is true based on taper alone, PWK pointed out that when attached to a large flat surface (a Klipschorn) the added air mass lowered the cut-off to 240hz. This was his reasoning behind the truncated mouth areas on all the K400, 500, 600, and 700 series horns. This is also why the LB-76 had wings (and even the massive Altec VOTT A4 and A2).

[D-MAN]

The true exponential vs. the modern hybrid and tractrix types. The K400 has an very low fc compared to most modern horns. Most newer horns are quite a ways above that which reduces the overall length. The dispersion characteristics also play into the overall size and length. Most modern midrange horns also tend to "squeeze" the throat channel (or somewhat near the throat) for enhanced dispersion characteristics and controllability.

For instance a 400Hz fc hybrid or tractrix variant can be as short as 8"+ or so in length. Dimensions are application specific, of course.

DM

[Guest Anonymous]

i have a question

since the horns scale and the demensions double from ie 1600 to 800 hz and the linear size is doubled, what exactly are you doubling? i am not completly grasping this concept and if its 4 times the size what does that mean and knowing this how does that affect the k-horn for example

[D-MAN]

The throat cross-sectional area doubles at a specified linear length according to the frequency (wavelength) chosen to the fc (frequency cutoff) of the horn.

The overall length is determined by the resulting flare rate and the size of the mouth appropriate for the fc of the horn in question. Different flares rates (exponential, conical, hyperbolic, catenoid and tractrix) determine the area doubling points along the path of the respective horn and the mouth size and configuration.

DM

[Guest Anonymous]

i think i got it now, that is interesting that things work out like that