vented box calculations

[Scott L]

I asking for a volunteer to double check my math. I do not have one of those box similation programmes, so I always do vent calculations via long math.

Given: Box volume (net) 1.8 ft^3
2 each ducted ports @ 4" i.d tuned to 56 Hz

I get 3.88 inches. Seems too short to me? thanks in advance.

 

[weltersys]

I asking for a volunteer to double check my math. I do not have one of those box similation programmes, so I always do vent calculations via long math.

Given: Box volume (net) 1.8 ft^3
2 each ducted ports @ 4" i.d tuned to 56 Hz

I get 3.88 inches. Seems too short to me? thanks in advance.

Scott,
Try all these, and take an average :^)

 

[revboden]

1.8ft^3 vol. with two 4" non flared ports... i get ~9.5" for 56hz

I think you did the calc for a single 4" port, which is about 3.5"

What end correction (k) are you using?

 

[Scott L]

The mysterious (k)

I'm sorry, not familiar with that (k). I do remember seeing it listed somewhere, but have no idea what it means?

Please enlighten if you so wish !

 

[revboden]

vent tuning

Ported Vented Box Equations Formulas Design Calculator k End Correction Factor

 

[Scott L]

We appreciate ya !

Thanks kindly !

Based on years of experience I had already decided to do external vents, such that, different lenghts could be adapted rather easily. One end flanged, one end free. Gota love it! Thanks again.

 

[weltersys]

Thanks kindly !

Based on years of experience I had already decided to do external vents, such that, different lenghts could be adapted rather easily. One end flanged, one end free. Gota love it! Thanks again.

External ports tune lower than the same port inside.

 

[Don Hills]

External ports tune lower than the same port inside.

It would be helpful if you explained why.

For example, "because the enclosure volume increases by the volume of the port when you move it from inside to outside. Larger enclosure = lower resonant frequency."