question about port sizes

[nas786 10+ year member]

I'm pretty new to this, I've tried searching google and this forum, but can't seem to get an answer. I've been messing with a couple diff programs to help me build a ported box. I've noticed that if you have a real small port, the tuning goes much lower. Since (it seems) most boxes are shooting to be tuned in high 20's, low 30's, why would someone opt for let's say a 4" aero port vs a 2" ? As the 2" seems much more manageable (for getting lower tuning frequency) and shorter rather than doing a 4" which would require a much longer port, so what is the benefit of using a bigger diameter port?

Also, why would someone make a box with multiple ports rather than just one, as that seems to dramatically increase the tuning frequency? What's the benefit of multiple ports?

Sorry if this is common knowledge, but I really gave it an honest shot and couldn't find any answers.

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[frogcase2002 10+ year member]

Usually bigger ports if there is port noise

 

[Buck 5,000+ posts]

I'm pretty new to this, I've tried searching google and this forum, but can't seem to get an answer. I've been messing with a couple diff programs to help me build a ported box. I've noticed that if you have a real small port, the tuning goes much lower. Since (it seems) most boxes are shooting to be tuned in high 20's, low 30's, why would someone opt for let's say a 4" aero port vs a 2" ? As the 2" seems much more manageable (for getting lower tuning frequency) and shorter rather than doing a 4" which would require a much longer port, so what is the benefit of using a bigger diameter port?
Also, why would someone make a box with multiple ports rather than just one, as that seems to dramatically increase the tuning frequency? What's the benefit of multiple ports?

Sorry if this is common knowledge, but I really gave it an honest shot and couldn't find any answers.

The reason is, as subs and power increase, you need a larger port area to avoid port noise as well as maintain efficiency to some extent. You don't tuning by square inches of the port, you tune by the length of it.

 

[nas786 10+ year member]

ok, that makes sense. So basically if I have a half inch port, although it will easily tune my box to a low volume with a short length, it will create unwanted noise, right?

^^yea, I understood that the length will change the tuning freq, it was just that I noticed smaller ports always required a shorter length for a given freq when compared to a larger port, so I was wondering why go large port with longer length.

thanks guys

 

[Buck 5,000+ posts]

General rules of thumb, square/slot/rect. port = 10-16 in^2 per cube (usually more towards 14-16), round port = 5-11 (usually 6-8).