speaker parameters testing

[dallaire]

I was wondering "again" Is there a curtian "formula" for determining the correct enclouser size that is used for testing for the Vas of the driver. You know how they say if you are testing an eight inch driver use "this" cubic in size test box, etc., etc. I have also heard that the test box should be large enough to raise the resonant frequency of the driver at least ten percent or so when put in the test box vs. free air. Is there a formula to use so one could find the correct test box volume for a given driver based off of the free air resonance. I am trying to find the correct test box internal volume for the Peerless four inch woofer that I intend to be using for midrange duties.

Anyone know of an easy formula for this???

[Ron E]

A formula that would work as well as any other would be to square the diameter in inches and divide by ~ 100 to 150. This would give the test box volume in cubic feet.

This gives (roughly):
12" ----- ~1 - 1.5 cubic foot
10" ----- ~.7 - 1
8" ------- ~ 0.5
6" ------- ~ .25-.35
5" ------- ~ .15-.25
4" ------- ~ .1-.15

[dallaire]

Great!, that is what I was looking for.
Thanks,
dallaire

[AndrewT]

Hi Dallaire,
can I suggest that your mid range may sound better overall if you do not box load it.

You have a choice of open baffle, open ended short tube, horn, transmission line, sealed box, vented box. I suspect they are listed in my order of preference. Each of these could be tuned with various amounts of long haired wool for damping.

[dallaire]

Yes Andrew, I think I'm going to experiment a little with this. Tonight I made a "mock" up baffle and mounted one mid in design position and affixed capped tube enclouser to back of baffle so mid "is" in enclouser. I will listen and measure this, then remove cap at end and test and listen again. You are the second person to suggest this, so I am looking forward to hearing and measuring tomm. I can't say I have ever seen a open back mid in any boutique or consumer electrinics outlet. I guess it would be hard to sell to most people with a hole in the back of a speaker But to "me" sound good I'll build it that way!!! I'll let you know how it goes, thanks for the info, it's allways nice to get other opinions on the subject!
Regards,
dallaire