unfolded length of Khorn

[Horatio]

This should be easy to find, but I have not been able to nail it down.

I am looking for the path length of the Klipschorn corner horn unit. I am going active, and want to adjust the delay(s) as I move through the drivers. Anyone know this path length?

Thanks!

[PrestonTom]

IIRC, the Heyser review article of the K-Horn provided those numbers. The article has been posted on this forum before, so it should be searchable.

[Colin]

From "A Low Frequency Horn of Small Dimensions", Journal of the Acoustical Society of America, vol. 13, pp. 137-144(1941 Oct.):

"…With
a frequency response down to 40 Hz, corresponding to a wavelength of
340 inches, comparable to the performance of the typical theater woofer,
this unit measures only 39 inches high, about the same width across the
'wings,' and only 28 inches deep from the front panel back to the
corner…

To
reproduce this wavelength [i.e., 340 inches] with the same degree of
smoothness of throat impedance and the same efficiency [as a typical
theater woofer], a conventional horn in free space would require a mouth
area of about 4500 square inches. If operated close to a floor or wall, 2300 square inches would be required, corresponding to a circular mouth 53 inches in diameter. The horn length required to match a 15-inch diaphragm would be over 80 inches. The horn of Fig. I [i.e, the Klipschorn bass bin] has an actual mouth opening of 570 square inches and a horn length of approximately 40 inches, representing a saving in volume of over 75 percent and a corresponding saving in material for its construction. A further saving in material results from using the room walls for part of the horn structure."

Chris

http://forums.klipsch.com/forums/p/121214/1222030.aspx#1222030

[Colin]

long thread here:

http://forums.klipsch.com/forums/p/121214/1222030.aspx#1222030

[Horatio]

Thanks- like most things Khorn, you get a variety of answers. It appears to lie somewhere between 1 and 2.2 meters or so!

I am messing around with a MiniDSP setup, and I have an EV HR6040/ EV DH1012 fitted to the top side. So, I am beginning to get it dialed in.

Thanks,

M

[Captn Bob]

I believe they used to say it was about 4 feet long before it entered the room.

[JJkizak]

I recollect that PWK said the horn dimension would be somewhere around 66.6 feet x something. He might have said 66 square feet.

JJK

[djk]

Heyser measured a delay of 7.4mS on the woofer with respect to the tweeter, this suggests about a 100" effective acoustic length of the bass horn in the room, and implies an Fc of around 34hz~35hz.

[Don Richard]

Heyser's numbers are not good for determining path lengths because of delays caused by inductors and caps in the xover.

[djk]

True, but it's a starting point, and the electronic crossover will have its own delays as well.

[Rivernuggets]

I recollect that PWK said the horn dimension would be somewhere around 66.6 feet x something

66.6 gets my vote [6]

[Chris A]

Heyser measured a delay of 7.4mS on the woofer with respect to the tweeter

I believe Heyser reported 8.4 ms for the tweeter-bass bin delay (top of pg. 68 in the article). He also measured a ~1.68 ms delay from the tweeter to the midrange. EDIT (15 Aug 2012): Greg Oshiro independently measured 6 ms delay (bass bin to tweeter) and 1.6 ms delay (midrange to tweeter) and checked his results re: Heyser's...I believe Greg's measurements.

If you are using an active digital crossover that bypasses the Khorn's internal passive crossover, I'd start with about 6.1 ms of delay for the tweeter wrt to the bass bin.

However, the more critical delay setting is between the tweeter and midrange: correcting for this 1.68 ms delay will strongly affect the Khorn's soundstage/ imaging. For example, if you use 6.1 ms of delay for the tweeter relative to the bass bin, that would mean the midrange would need 4.42 ms delay.

Chris

[Horatio]

Folks:

I have appreciated the comments and will take these into consideration as I tune this system. Right now, I am converting from the original three-way based K400/T35 type tophat to a two-way using a large format compression driver behind an EV HR6040 CD horn (one of the type that Keele designed in the 1970's). So, the delay I must dial in is that between the bass and the HR6040.

The procedure I'm inclined to follow is the one outlined by Jim Long in Sound Practices #13: Set SPL of bass and tweeter (in this two way system) to be equal at the crossover frequency, then, invert the polarity of one driver and begin advancing the delay until the sound level at the listener begins to drop and then increases again. At null, the signals are exactly 180 degrees out of phase and cancel. So, once you are there, flip the polarity back, and viola, you have it. I will report the number I find, together with the length of the HR9040, so that was can deduce the effective bass horn length.

-M

[PrestonTom]

That sounds like a great project.

For others who follow the proceedure outlined above, keep in mind that you still need an approximate delay (or distance). The proceedure can be off by the period(s) of the waveform. That is, 360+180 deg or 720+180 deg etc.

I hope it works out for you. I use the little brother of the horn you are referring to (EV HP640) with great success.

[Edgar]

Jim and I used that technique in this demo. The surprising thing was that the actual delay was not especially close to what was predicted by the measured distances -- has to do with acoustic centers, propagation velocities, etc. But the technique worked.

Greg

[Don Richard]

the electronic crossover will have its own delays as well.

Correct for an analog unit, but most digital processors use FIR filters for the xover functions with no phase shift, or only a few degrees of shift. Some fancy ($$$$$) processors allow independent control of phase, raised cosine EQ, and all sorts of fancy tricks.

[Horatio]

Greg:

Thanks for the link- those HR9040A's are lovely, aren't they? I have a pair of those, too, and think they are just fabulous. Problem is, they are enormous! I could not find a way to integrate them into the top section of a Khorn- just too wide. The HR6040's I have fit just perfect, width-wise, are are of the saem overall height at the HR9040's. They are a bit deeper than than HR9040's, and so fitting the driver and ensuring this will tuck into the corner can be a bit a of a trick- the DH1012 will make it, but I am not sure if say, a 488 would!

I think Jim's advice on setting the delay makes the most sense, anyway, because one does it empirically, to ear, and the adjustment ought to be fairly sensitive. In the end, we want the result to sound good, not just be tuned to theory.

[Edgar]

Thanks for the link- those HR9040A's are lovely, aren't they?

Lovely sound, horrible shape! I have a pair myself (the ones shown in the link belong to John Stronczer), and I have spent many long hours trying to design a cabinet that houses them in an aesthetically pleasing manner. But the curved fronts make it very difficult.

I could not find a way to integrate them into the top section of a Khorn- just too wide.

They can be made to match a Jubilee bottom, as they are almost exactly the same width as the K402.

They are a bit deeper than than HR9040's, and so fitting the driver and ensuring this will tuck into the corner can be a bit a of a trick- the DH1012 will make it, but I am not sure if say, a 488 would!

I don't know about the 488. I have a pair of Altec 288. If I remember correctly, they are something like 6½" deep. So that will just make a bad situation worse.

I think Jim's advice on setting the delay makes the most sense, anyway, because one does it empirically, to ear, and the adjustment ought to be fairly sensitive. In the end, we want the result to sound good, not just be tuned to theory.

Be aware that the measurement microphone needs to be as near the listening height as possible. For typical crossover frequencies in the neighborhood of 500 Hz (wavelength ~2'), an off-axis path length difference can be significant.

Greg

[Horatio]

288 indeed. Had a bit of a synaptic failure there!

Thanks for the tip on the microphone height- I am using REW to make the measurements, and I am finding the room sensitivities part of this quite interesting. The microphone I'm using (basic RS SPL meter, which seems credible enough for low end work) will limit decent upper end measurements, but we'll see how it goes.

The shape of the HR9040/series was their undoing, almost for sure. Who can deal with the shape? I found that I could incorporate the HR6040 into a tophat that looks like it actually fits the Khorn, in terms of styling. But, it's alot like the 1950's klipschorn design, except for the size differences in the tweeter horns.

-M

[Guest " "]

I would accept the 66 inches. I get 57 inches by adding the part lenths. Keep in mind that there are two exit paths so I came up with 57 for one and 57 for the other. They wouldn't be added together. And you would probally have to apply some spooky math because each path is 45 degrees off axis from the mid driver and tweeter center line.

klipschorn.pdf