A-290 Wood Horn


Death Valley, CA USA (Photo by Yuichi)

A-290S Specifications

= Horn Type : Hyperbolic horn
= Cut-off frequency : 290Hz
= Frequency range : 600Hz to 20KHz
= Driver : 2 in or 5 cm throat (Pioneer TAD 400x or JBL 244x or
equivalent)
= Size : W 635mm, H 230mm, D 434mm (incl. 50mm throat adapter)
= Material : Chinese quince laminated lumbers (3.0cm thickness)
= Finish : Two coats of oil based clear polyurethane varnish

= Color : Not applied
= Others
- Four fins inside of the horn

.
.August 1990 issue, MJ Magazine

Since the A-290 contains two curved surfaces joints in its structure, building process is a little hard to adjust these joints by hand tools. The A-290-S (S stands for "Strait") is intended to be build more easily without loosing performance of the A-290.
Instead of two curved joints, strait joints are adopted in this horn. However, it still looks like curved horn by forming of mouth area and addition of half fins inner of the side walls. The angle of both side walls is 90 degree which also gives us better productivity for cutting, building and assembly process.

Building and assembly process


Cutting out from the
lumber by a hand circular
saw.
Rounding process by a
circular saw and a sander
Fixing of three lumber
pieces to make upper /
lower horn components
Provisioning process of
strait joints for the side
walls
Confirmation of the joint
between the side wall
and the lower horn
component
Temporary assembly of
four horn components for
making sure the fitness
Curving process of upper
and lower components by
a planar, a rotary sander
or a belt sander
Confirmation of four
assembly components and
making screw holes from
the side walls
Forming process of the
side walls in its mouth
area.
Cutting and forming of the
fins and the 1/2 thick
fines for side walls
Setting up of the fins and
the 1/2 fines inside the
horn area
Bonding, filling of Epoxy
/ wood powder and
polishing process for surface finalization.
Cutting out of the horn
throat hole in horn
adapter
Forming of horn section
( circle to square conversion ) in the horn
adapter
Application of the varnish
coating (twice)
The adapter is attached
to the horn body with
four nuts and bolts

(6.5mm)


Measurement and Data


The data in the left is a frequency response curve when TAD 4001, 2 in throat, driver is mounted. The response shows very flat sound pressure level from 400Hz to almost 20KHz.

This horn with TAD 4001 or JBL 2441 or equivalent driver covers mid to high frequency range in 2 way or 3 way configuration.
However, very high frequency response depends upon the driver capability.

To set the crossover frequency as 300 or 400Hz is a little risky. Therefore, 600Hz (300Hz x 2) above is safe to use. Since TAD 4001 has very good high frequency response, we can use this as tweeter in the 2 way system.
This data is a impedance curve when TAD-4001 is mounted.

It shows that the horn load is added on the diaphragm starting from 320Hz.

Therefore, it is a good idea to use this horn from 600Hz with enough guard band.
The data in the left column is a frequency response curve when JBL 2441, 2 in throat, driver is mounted. The response shows very flat sound pressure level from 380Hz to almost 10KHz. Above 10KHz response depends upon driver response.

However, setting the lower side of crossover frequency as 300 or 400Hz is a little risky. Therefore, 600Hz (300Hz x 2) to 8KHz bandwidth may be reasonable for A-290S and JBL-2441 combination. In this case a super tweeter may be needed to cover higher than 8KHz band. So, 3 way configuration is highly recommended.
This data is a impedance curve when JBL-2441 is mounted.

It shows that the horn load is added on the diaphragm starting from 320Hz.

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