How big a Khorn to reach 20Hz?

[D-MAN]

Found this... from Dinsdales Wireless World articles (2 of 3)...

The complete set is available for download from http://www.volvotreter.de/dl-section.htm

DM

[Benesesso]

This is what a pair of Universal Studios "Earthquake" (Sensurround) flare extensions look like, with wife standing inside. Note the Khorn in back.

If you feed them ice cream it's amazing what you can get away with!

Benesesso

[WMcD]

I was relying on the 1941 article, " A Low Frequency Horn of Small Dimensions." After the initial expansion, "The remainder of the area doubles every 16 inches so that the nominial cut-off is 47 cycles."

Granted there may have been changes to the design.

I'll agree that a fair reading of the Jubilee article is that both the K-Horn and Jubilee have a 38 Hz cut-off target. However, in my view, there are several data points one can use to calculate the cut-off in either design.

Gil

[formica]

Found this... from Dinsdales Wireless World articles (2 of 3)...

If those numbers are correct for 1/8 space, cornerhorn we can extrapolate the values for 20Hz seeing that the diameter doubles for every additional octave of extension.

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Freq (Hz)

Area (sq.ft.)

Dia (ft)

20

31.37

6.32

25

20.11

5.06

30

14.00

4.22

35

10.18

3.60

40

7.87

3.16

50

5.03

2.53

60

3.50

2.11

70

2.57

1.80

80

1.97

1.58

90

1.55

1.41

100

1.26

1.27

110

1.04

1.15

120

0.87

1.05

140

0.64

0.90

160

0.49

0.79

200

0.32

0.64

280

0.16

0.45

400

0.08

0.32

560

0.04

0.23

They seem smaller than I expected... but it does say those are minimums...

Rob

[Chris A]

I found this older thread while looking for something else. Just wanted to add the links to Danley's tapped horn (TH) designs and Bill Fitzmaurice's various DIY designs that address sub-32 Hz horn-loaded bass needs of the Klipsch full-range horn crowd. The tapped horns are more compact, but in general lower sensitivity designs than Fitzmaurice's designs:

http://www.diyaudio.com/forums/subwoofers/134369-dual-8-tapped-horn-th-spud-3.html?postid=1698483#post1698483

http://www.danleysoundlabs.com/tapped_horn.html

http://www.danleysoundlabs.com/pdf/danley_tapped.pdf

http://www.billfitzmaurice.com/

Chris

[jtkinney]

I found the whole Crabbe article for the concrete horn. Not likely to happen in the house,but there is that pesky neighbor[:@]

Jim

6711crabbe.pdf

[mustang guy]

here is my math on the horn length.

K Horn is a quarter horn, so the horn length is going to be 1/4 of the frequency wavelength.

Frequency wavelength of 30 Hz = 37.53'

Frequency wavelength for 20 Hz = 56.3'

20Hz wave 56.3 - 30Hz wave 37.53 = defference 18.77'

1/4th of 18.77' = 4.6925' or 4' 8 1/3"

Couple that with the horn area mentioned previously (Formica: 31.37 sq ft area, and 6.32' diameter), and you should have your horn extension. The horn will stick out into the room about 5' farther, and the mouth would be 5' tall by 6' wide roughly. As the Khorn is corner loaded, does that mean a couple more turns then shoot back toward wall?

[mustang guy]

I found this older thread while looking for something else. Just wanted to add the links to Danley's tapped horn (TH) designs and Bill Fitzmaurice's various DIY designs that address sub-32 Hz horn-loaded bass needs of the Klipsch full-range horn crowd. The tapped horns are more compact, but in general lower sensitivity designs than Fitzmaurice's designs:

http://www.diyaudio.com/forums/subwoofers/134369-dual-8-tapped-horn-th-spud-3.html?postid=1698483#post1698483

http://www.danleysoundlabs.com/tapped_horn.html

http://www.danleysoundlabs.com/pdf/danley_tapped.pdf

http://www.billfitzmaurice.com/

Chris

Also look into Infinite Baffle (IB) sub projects. They go even deaper than the Danley's.

[Chris A]

One of the issues that I see with this approach is that is becomes impractical using a Khorn bifurcated horn approach (even with its two axes of expansion). That's the rationale for posting links to other horn-loaded subs designs for that bottom octave below 32-40 Hz (i.e., 40 Hz is the Khorn's and Jubilee's design Fc mentioned from the Delgado/PWK article).

Some additional thoughts along this line of reasoning:

The TH designs (such as the SPUD and DTS-10) fit nicely behind Jubilees, allowing the Jubilees to move out into the room a little bit for better midrange imaging. Tapped horns produce the smallest footprint design of all due to their "reflex" loading of the drivers internally. You could also use this technique with 60th Anniversary Khorns, La Scalas or Belles (all having closed backs like the Jubilee bass bin), but you might want to use the smaller SPUD design in order to get enough hf extension from the subwoofer to cross with the LS or Belle around 90 Hz. I presently cross at 40 Hz from Jubilees to TH subs.

The Fitzmaurice designs would probably have to be placed elsewhere in the room, I would think, unless you have a very large and wide room that would allow the placing of one sub in each of the front corners behind the mains. The advantage of placing a sub in each corner is that you don't have the separate room mode cancellation issues that you have with separately located subs (see Floyd Toole articles and the Pi speakers article for an explanation of this phenomenon).

Chris

[Chris A]

Also look into Infinite Baffle (IB) sub projects. They go even deeper than the Danley's.

Yes, but they act like direct radiators with their 10-15 dB higher IMD (...mostly AM distortion with some FM distortion...according to PWK).

Chris

[garyrc]

In the best room I ever had my Khorns in, with Luxman amplification, there was actually a little, clean peak in the 31.5 Hz tone. Using another test recording, the Khorns sort of went down to 25 Hz, even put out some sound at 20, but both were distorted, very attenuated, and sounded frightening. In the other rooms I've had them in, it's more like 35 Hz with a little attenuation. A spooky thing is that in one house, the very deep bass sounded better two rooms away, with all the doors open.

[Chris A]

This seems to be a common theme of Khorns: "they sound even better in the next room"...but in this case it's about bass response. The distortion of Khorn bass bins is usually very small (unless boosted via EQ below Fc), and when you go into the next room, THD and IMD get attenuated below aural thresholds (IMHO).

One thing that I think would reduce the variability of Khorn performance is enclosing the backs, a.k.a., 60th Anniversary-style, or using good built-in false corners (TSCM-style). Then placing them into corners would definitely result in good, solid lf performance without requiring EQ boost below Fc.

Another big improvement would be tri-amping Khorns with a digital active crossover and time correcting for the midrange and bass bin delays (e.g., bypassing the passive crossover altogether). I believe that a many issues having to do with the small room performance of Khorns might disappear if this were done.

Chris

[Don Richard]

The main parameter that determines the cutoff freq of an exponential horn is the flare rate. The length of the horn can be no shorter than 1/4 wavelength or there will be no horn loading. At 1/4 wavelength the response will be rougher than a full length horn, but who makes a full length horn anyway these days? Mouth size can be reduced by corner placement.

Stacking two Khorn type bass cabinets would result in mutual coupling, a larger mouth, and more output. Two horns will go about 1/3 octave lower than one horn. Using EQ to reduce output from the upper bass range and to increase output below 35 Hz will allow a setup like that to go down to 25 Hz or so with low audible distortion and serious gut rumbling power, but that's about it if you want to use Khorns as a building block.

[JJkizak]

PWK was saying that he couldn't bend a 20HZ wave around the partitions within the horn as it exists today.

JJK

[T.H.E. Droid]

reading this thread, it's amazing how rediculous some of these gearhead conversations can get. Kind of like those guys with 2000 HP engines in street cars or the ultimate male fantasy, the 36-incher. Or 10,000 watt car stereos. All silly, all expensive to the point of the absurd, and all useless. Probably cheaper just to hire some homeless person to hit you in the side of the head in time to the music.[6]

[Islander]

This is what 30Hz straight horns look like:

[Islander]

Angle view of 30Hz horns:

[Islander]

reading this thread, it's amazing how rediculous some of these gearhead conversations can get. Kind of like those guys with 2000 HP engines in street cars or the ultimate male fantasy, the 36-incher. Or 10,000 watt car stereos. All silly, all expensive to the point of the absurd, and all useless.

Silly? Absurd? Useless? Not really. I'm really happy with the pair of 500Wpc power amps feeding my JubScalas. They weren't cheap, but the sound is clean and the headroom lets transients like drumbeats sound realistic, even at low volume. They're worth it to me.

For another example, here's a guy with a 2200bhp street legal car. He's got a lot of money into it, but it's expensive to go fast. Compared with high-end Italian machines, his car is a relative bargain.

Fastest street legal car:

Here's a high 6-second street car. Do you think the owner looks happy with it?

[mustang guy]

Don't leave out bikers.

and http://www.youtube.com/watch?NR=1&v=DDWqJe1dCgY

[Islander]

The quest for power can be hazardous: