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08_february_07
Introduction
The Frugel-Horn
(the name is a cross between flugelhorn & frugal) is an open-source DIY
project to develop a small, inexpensive, full-range rear-loaded corner horn. The
design has reached version 1.0 -- in a number of variations -- with a well developed
set of plans available. For those interested
in how we got to here, check the history
page.
Small & full-range horn are 2 words you don't really see together very often.
How low a horn* can go is determined by its mouth size. Low frequency cutoff of a
circular horn is the frequency with a wavelength the same size as the circumference
of the horn mouth -- converted to a square we are talking about a mouth 16 ft x 16
ft for true 20 Hz horn bass.
* (most "horns",
including the Frugel-Horn are actually hybrid TL/horns. Below a given frequency the
mouth is not large enough to damp the pipe resonances giving undamped TL action.
Above this frequency the mouth becomes large enough to provide the horn damping and
you transition to a horn loading.)
By using a smallish driver (Fostex FE126), setting realistic bass targets, and by
using a corner (which multiplies the effective mouth size by 8 times), just such
a beast has been created. This is not the 1st time this has been done -- little in
audio is and one of the more recent notable examples is Ed Schilling's justifiably
famous Hornshoppe
Horn. Its stellar
performance has earned it a Stereophile Class C ranking. The genesis of the
Frugel-Horn, arose from someone on an audio forum asking the question "DIY design similar to hornshoppe?". |
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The Frugel-Horn has
some features not often seen. It can be built to 4 different levels, in 5 basic configurations.
In its basic Level 0 trim it is a rectangular box a bit bigger than Ed's Horn. In
full Level 3 build, it is a decidedly non-rectangular box with a mouth-size that
gives theoretical potential of fully horn-loaded bass to 75 Hz (half an octave lower
than an L0 build) when properly loaded into a corner. The 3 elements that turn an
L0 into an L3 -- the curved exit, the deflector, and the supraBaffle ...borrowed
from Ron Clarke's designs -- Ron designed the rear of the Frugel-Horn. See the technical
page for more info.
Another intention of the design is to leave latitude for builders to impress their
own artistic vision on the finished product. As well as the different technical elements,
there are some elements that are more artistic in nature, most notably the opening
up of the voids. Already some very elegant & beautiful variations have been brought
to life.
Ignoring the builder's time, investment in tools, and cabinet finish, a pair of Frugel-Horns
can be built using with the Fostex FE126E for ~$250/pr. If you have the wood lying
around and a set of less expensive drivers you could have a pair of speakers for
much less. Based on results from recent experience with cabinet materials on other
designs, we would strongly recommend Baltic birch plywood for construction, but feel
free to experiment with any other sheet goods or even solid hardwoods.
Frugel-Horn Discussion Threads:
The Frugel-Horn is
open source. The continued involvement of the entire community in the development
of this design already has sonics that can rival any speaker in its niche: continual
development & exploration will only make it better.
You are free to build it for your own use or commercially. Builders are encouraged
to contribute at least feedback to help improve & fine-tune the Frugel-Horn.
Commercial builders are encouraged to contribute back to the community whether it
be support to keep this site running, to aid/contribute to a DIY/audio forum, to
help promote DIY audio (eg co-op with a school shop to teach kids speaker building)
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