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[Don Snyder]

The spreadsheet from Peter's website is almost exactly the same data as Tom D's early information. Unless you want a different minimum frequency, or want to change the throat area, there's nothing that should be changed. A more interesting question is "how close does the LABhorn match the spreadsheet?"

As it turns out, the hardware doesn't have to be a very close match to the spreadsheet to be within 1 dB of the theoretical values. Corners don't have to be rounded, curves don't have to be "fair" and the flare can even be negative at times.

If you look at the spreadsheet for the flare at 0, 5 & 10 inches, the areas are computed to be 78, 83 & 89 sq in. But the as-built horn has a measured area at 5 inches of 107 sq in. This means that the air passes thru the throat, expands entirely too fast, and then CONTRACTS. Clearly NOT what the spreadsheet says it should do.

The throat area is important, the mouth area is important, and the distance between them is important. Leaks are important, and front & Rear speaker chamber volumes are important. Beyond that, you can usually get away with murder!

Four LABhorns work GREAT together! A single horn with a mouth of 30" x 120" will work almost as good. There will be no "power alley" and no beaming problems, because this "small" mouth will look like a point source to 90-100 Hz waves, and everything above 100 Hz will be comming from your top boxes.

The spreadsheet is available at:
http://home.comcast.net/~labhorn/extension/

Questions?
Don

[[x]]

You should just build an alcove under the stage, in the very center, where four LAB Horns can be placed, and you could put them on a rolling platform that could be pulled out for servicing, if it ever becomes necessary.

[Alan Searchwell]

Why not fold a half wave or full wave length horn under the stage as shown in my attached sketch? It's about as rough a sketch as you can get but I hope you can get the idea. I can see a couple of advantages to this concept

1) Depending on the dimensions of your stage, this horn can end up seriously long.

2) Access to the drivers can be arranged through panels at each side of the mouth opening.

I also did a sketch for a single driver where the horn follows the perimeter of the stage that would give you an even longer horn path using a similar arrangement. The only catch is, can we come up with a design that can use the given possibilities for mouth area and horn length with a practical throat area that uses a readily available driver?

[fernand]

This idea has quite some advantages.
If the horn is not folded, then you can consider going up to maybe 200 Hz, which seriously simplifies the top requirements. After all, a top that runs down to 100 Hz without phase/timing problems from the reflex is a major problem if you want to avoid 4-way systems.

However, I have no idea how to calculate the usable upper frequency of a long horn.

[Don Snyder]

[Jani Koskelainen]

Not that i know really much about speaker designing..just out of pure curiosity..

How on earth would you time-delay players on stage to align with foh?  

-Jani-

[Don Snyder]

Digital Signal Processing (DSP) is the answer. Once a signal is digitized, delay is easy, as are crossovers, compression and notch filters. The trick is to know how much delay, filtering, etc to apply. A sound engineer with a laptop, microphone and the proper software can do what would have required miracles 20 years ago.

http://www.siasoft.com/
http://www.driverack.com/

[Jani Koskelainen]

Yup! Delaying foh to align with subs should be rather easy with dsp, but if i've understood right, the horn will be nearly 5m long. I think dsp won't align your players 5m behind the edge of the stage to align with foh..  

Jani

[Don Snyder]

Hi Jani!  You're right, all this digital magic won't work on the kick drum. That's why you often see him behind plexiglas.  If the other performers are loud enough to be a problem, you turn their amps around like monitors. If the back of the stage is "hard", the monitors will reflect off it and arrive at the front of the stage even later than the bass horn. Then the bass horn will need 15 ms of delay and the stack will need 30 ms of delay. All this gets complicated, but it can usually be made to work.