# Box design, do these numbers look right?



## Hogger (Nov 25, 2009)

I'm playing around with different online calculators and found one at kbapps.com so I started punching in some numbers.
For a 6.5" woofer
Fs - 40Hz
Qms - 2.75
Qes - .30
Qts - .27
Vas - 17.4 liters

So the calculator is suggesting a 6.5 liter box, which looks about right to me. But, with a 3" dia. port that is 26" long??

Anyone used this site, do I have some numbers wrong?


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## Hogger (Nov 25, 2009)

Alright so I tried a different site. It gave be suggested box size of 7.3 liters and a 2" port that is 7.6" long.
Looks a little better to me.


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## lsiberian (Mar 24, 2009)

I'd just use winisd.


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## Hogger (Nov 25, 2009)

I've been playing with WinISD also, but I guess I need a little clarification to make sure I'm doing the conversions properly.
When it asks for Xmax, it ask for it in "m". Most speakers I see give it in "mm". So if a given Xmax is 3.5mm do I convert it to .0035m to input into WinISD?

It also asks for speaker diameter in "m" instead of the standard inches given. So I just convert from inches to meter.


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## Hogger (Nov 25, 2009)

In WinISD I'm not sure what goes in the "P" spot, are they asking for RMS or peak power?
The only way I could get port dimensions for a 6.5" woofer was to enter something into "P" so I entered the RMS wattage.
Now it says my port must be 1.85" x 19.4" for a 5.6 liter box tuned to 41.59Hz. Sounds a little excessive to me for a 6.5" woofer.

The woofer is an MCM 55-1860.


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## mosconiac (Jan 31, 2009)

To change units for any one parameter, just click on the letter itself to toggle thru the range of choices.


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## lsiberian (Mar 24, 2009)

Hogger said:


> In WinISD I'm not sure what goes in the "P" spot, are they asking for RMS or peak power?
> The only way I could get port dimensions for a 6.5" woofer was to enter something into "P" so I entered the RMS wattage.
> Now it says my port must be 1.85" x 19.4" for a 5.6 liter box tuned to 41.59Hz. Sounds a little excessive to me for a 6.5" woofer.
> 
> The woofer is an MCM 55-1860.


You can put whatever you like there. It really depends on what you want to measure. the RMS wattage has no effect on the baseline model. It only effects the needed cross section for your ports on a sub.


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