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Milkduds 18th September 2012 04:16 PM

Help with FUN science fair project
I'm helping two sons with a science fair project (7th/9th grade) this fall. We've decided (ok... I've decided) to do a simple project that answers 2 questions. What cabinet design plays the loudest (most efficient) and has the best bass response. The dependant variable will be the MCM 55-2421 driver (only because I need to buy one!). I need help coming up with as many cabinets as I can, within reason. We will build simple, not pretty, cabinets and test outdoors. I'd like 6 or 7 designs, maybe one or two that are a little odd. Maybe a long piece of PVC, cardboard box, or something. I already know the winners but I want my sons to learn for themselves. Here's my list so far.
Air suspension
Bass reflex (one, maybe two alignments)
Infinite baffle
Front loaded horn (already have an autotuba I built that needs a new driver)
Tapped horn

What is top end frequency you would suggest for the test?

Please help a dad out!

Jim D.

m R g S r 18th September 2012 05:37 PM

Is this going to be a single driver full range project?

NEO Dan 18th September 2012 06:35 PM

The 55-2421 is not what I would call a flexible driver. How did you kill the one you had?

Milkduds 18th September 2012 07:37 PM

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The 55-2421 is not what I would call a flexible driver. How did you kill the one you had?
The surround on the first one separated from the cone after much use in the autotube in my older son's 4 runner.. and one month after the warranty ran out.

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Is this going to be a single driver full range project?
No, defnitely not a full range project. This is more of a bass/subwoofer project so I'm thinking of 250 hz and lower although I know some of the designs will roll off well below 250 hz. It will not hurt to plot some higher frequency points just to teach.

Jim D.

Milkduds 18th September 2012 07:42 PM

On second thought, I also have a pair of the smaller FR(WR)-125S drivers made by Creative Sound I could use. I cant remember the exact model number. Would this be a more "flexible" driver? The cabinets would be smaller :-).


Milkduds 18th September 2012 08:41 PM

One more driver I just though of that I have in house and already have a tapped horn for this one - TangBand 1139SI, 6.5" subwoofer.

NEO Dan 18th September 2012 08:54 PM

Looks like the makings of a decent 2.1 system. I would recommend that you start by learning to measure the TSP's of the TangBand woofer using something like REW as it will allow you to also take the acoustic measurements for your project.

jbell 18th September 2012 10:35 PM

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