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Cross Sectional Port Area?

580 Views 2 Replies 3 Participants Last post by  Jack Gilvey, 
Q
Can anyone tell me the benefit of increasing the cross sectional port area by using multiple ports or larger ports? There isn't any increase in SPL, is there? This concept of multiple ports seems to be pretty popular. I was just wondering why companies like SVS and HSU were doing it. I see that they state that you can vary the tuning of the box by plugging one or more ports. Is this the only reason they use multiple ports?
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It reduces the air speed coming out of the port, which makes it less audible. Prevents "chuffing."


This also lowers your first port resonance and requires a longer port for the same tuning as opposed to a smaller diameter port...so there's a happy medium to find.


I believe that with multiple ports, you can have shorter and smaller ports, though I'm not sure how exactly those calculations work (I would assume you just add together your total port length and total port area, to get the equivalent tuning of one longer and larger port. Maybe this would increase your port resonance frequency? Sorry...I'm out of my element when it comes to this part. Interesting to look into though!
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Quote:
I see that they state that you can vary the tuning of the box by plugging one or more ports. Is this the only reason they use multiple ports?
Also, they use commercially-available ports, cheaper than tooling your own. Technically, achieving a desired cross-sectional port area with one port is better than with multiples due to less surface friction, but I haven't seen this shown in measurements.

Quote:
Can anyone tell me the benefit of increasing the cross sectional port area by using multiple ports or larger ports? There isn't any increase in SPL, is there?
Potentially. Less compression/noise from the greater airflow.
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