Experimental design (mini A-7)

[pizzazz]

Hi

I am new to this forum and I do not know if it
is the correct forum.....

I want to build a mini version of the A7 cabinet.
Same layout, but instead of a 15 inch woofer, I
want to use a 10 inch. (must make wife happy
with size).

Anyone ever create a mini version of the A7? I
predict a 1/3 loss of overall size.

suggestions?

Mike

[Mr. Widget]

The A-7 is limited in it's bass output to begin with because of it's rather small bass horn... making it smaller will further restrict your bass response. You could probably scale the drawings down and give it a whirl... I'd expect you'll need a helper woofer too. I doubt that a true sub will suffice as you may want to cross over around 120Hz to 150Hz instead of the typical <80Hz for a true sub.


Widget

[john tyler]

I built a pair many years ago.....using a 10" (or may have been an 8" LF driver)....the coolest thing about them was using an 800hz horn instead of the 500hz...that made the whole thing look so "scale".........this was for a small PA so extended bass response was not necessary....just like its big brother ! they were cute...........have fun

[whgeiger]

Hi

I am new to this forum and I do not know if it
is the correct forum.....

I want to build a mini version of the A7 cabinet.
Same layout, but instead of a 15 inch woofer, I
want to use a 10 inch. (must make wife happy
with size).

Anyone ever create a mini version of the A7? I
predict a 1/3 loss of overall size.

suggestions?

Mike
Hi Mike,

Intuitively your wife knows more about acoustics and loudspeaker design than you do! The A7 is intended for use in a large theater. Do you have one?

The purpose of the horn load on the front of the driver is to emphasize mid-base and higher frequencies. For a smaller driver the horn gets longer, not smaller. For the reflex back load, the required volume and port dimensions may be smaller. In any case the enclosure design will be driven by the TSP's of the driver used not just its diameter. Scaling enclosure size by driver size alone, for this particular enclosure, is simply an exercise in serendipity. You may want to consider constructing a pair of Altec 816 enclosures and use the 15” driver recommended. See http://www.wmeckle.com/ALTEC/Index.htm (http://www.wmeckle.com/ALTEC/Index.htm) for an example construction project.

Otherwise you are into a very long R & D project to redesign the A7 for a particular 10” driver. If you pursue this tack, use of the JBL 2251J should be considered. And a higher c/o (say 800-1200 Hz.) may be used. TSP’s for this driver follow:

Model: 2251J
[Fs]: 61 Hz.
[Qts]: 0.20
[Qms]: 4.0
[Qes]: 0.21
[Vas]: 1.011 m^3
[Eff]: 2.89 %
[Pe]: 388 watts
[xmax]: 5.7 mm
[re]: 12.65 Ohms
[Sd]: 0.031 m^2
[Bl]: 26.77 T*m
[Mms]: 0.032 kg

A smaller compression driver and HF horn may be used to cover the top end if the higher c/o frequency is used.

Regards,

WHG