12" Khorn bass bins info wanted

[greg928gts]

Seems like I heard about someone building a pair of 12" Khorn bass bins. Anyone have information on these?

Greg

[Frzninvt]

Greg forum member Digjr built a scaled down set of Khorns with a 12" woofer. He lives here in VT, I can send you his email address if you like. Send me an email and I'll reply with it.

[WMcD]

I had built some smaller LaScalas which did not work very well. Could be my construction.

I did some cogitating on why a scaled down K-Horn or LS didn't become popular. Please note the K-Horn has a 48 Hz Fc flare and the LS has a 63 Hz Fc.

My observation is that the full sized K-Horn has a relatively small mouth for the application. Bass response falls off and mouth size is part of the problem. One of the reasons it works is that the room modes, in the low bass region, give it some boost.

The problem, MAYBE, is that room boost MAYBE doesn't exist at higher bass regions where a scaled down version would need it. If you make a 2/3 scale K-Horn, it might need a 2/3 scale room.

The initial thought is that we all have rooms of various sizes and finding a small room is not a problem. However, the ceiling height is part of the issue with modes. I've got an eight foot ceiling, and going to 2/3rd of that is not easy to live with.

On the other hand, look at the full sized LS. The Fc is in the ballpark of what a 2/3 scale K-Horn would be. But the mouth size is relatively larger than the K-Horn. Cranking some math, the mouth size for the full LS is just about optimal for a corner. So it may be less dependant on room modes for boost.

My conclusion is that the full sized LS and Belle are a better design of a scaled down K-Horn.

Gil

[ben.]

Yeah, if I recall, he wasn't too happy with the sonic results. I think he ended up eBaying them. They'd be a good movie prop for something like "Being John Malkovich".

[D-MAN]

The bottom line to scaled down horns is that the low frequency waveform being produced isn't scalable (40Hz is still 32 feet long). Mouth size still has to be a certain proportion to the throat area and the length of the horn (and its expansion rate vs. length) cannot scale down unless you WANT a higher low-frequency cutoff. So most people end up with folded midrange horns, which is not a good thing as they sound really quite bad.

The full-size Klipschorn has an approx. 4 sq. ft mouth area and features an expansion rate area doubling length of 21.75 inches. Placing it in a corner allows the mouth to "appear" to be 16 sq ft (radiating into a 2pi/r solid angle ), the main benefit of corner loading a horn. Scaling this down means that there is no way to "go as low", as the physics exclude it. Even increasing the cone excursion will still not propogate low frequencies through a smaller horn of reduced length in the fashion desired.

Also folding a smaller horn at higher frequencies (even lower midrange) causes unacceptable distortion to the waveform in what is known as severe "coloration", that is a muddling effect.

The laws of physics prevent small folded bass horns.

DM

[greg928gts]

What if I only wanted them to cover 90 - 400 hz?

Perhaps what I should be asking is, what is a good match to a Khorn bass bin that can cover 90 - 400 hz with the same efficiency, voicing, dispersion, etc...?

Greg

[D-MAN]

80-90Hz would be around 10" (I would have to look it up to be sure) range for an exponential expansion doubling area length. That would render a rather small scaled Khorn about 1/2 size.

As long as you don't attempt to crossover much above 400 Hz, I don't see a problem.

The full size Khorn has about 64 inches of folded horn from the throat to the outside mouth, center of channel.

You would be able to cut that in about half for 90Hz fc.

The efficiency would be about the same as a full sized horn provided that the fc of the driver is 96.5db to start with. The overall mouth area would be about 1/2 too or about 2 sq. feet overall area.

I would scale the Khorn dimensions to 50% of the full sized version, which should give you a 80Hz fc on the bass horn. The throat opening should be 39 sq. inches - which is what the full size horn uses as an OPENING, but it is smaller than optimum throat size (78sq") to lessen the passage of upper bass (the K33E has a peak at 400Hz). I would avoid that, as you won't be using a K33!.

This would render a Khorn 1/2 as tall (approx 20 in) and 1/2 as wide (15 in) and about 1/2 as deep. I would think that a good 8" or better yet a 10" driver would be in order.

DM