Port Size question with multiple speakers

[DeuceLee 10+ year member]

newb question ALERT!!!

Say ONE Sub has factory recommendations of and requires a port size of 2 inches wide by 12 inches high, total of 24 square inches area...(lenght will be determinded by the tuned frequency so that doesn't matter in this situation)

say if you have 2 of the same sub, i know if you keep the orginal port area of 24 inches and orginal tuning frequency, the lenght would reduced by about half (once again the lenght is not relevent here) but you should probably add more area because you have 2 subs breathing now and no just one...

the question is would you double the width to 4 inches to get 4x12 (total of 48 sq inches area) or is it going to be 1.5x the orginal width to 3 inches for a total of 3x12 (36 square inches area)???

i guess i could probably call the manufacturer for their suggestion but just wondering if any of you wizards know any general rule of thumbs...

Click to read more...

 

[dkguitarist 5,000+ posts]

if you had 2 subs in the same box, you could give each it's own chamber and give each it's recommended port size. same thing if you have a single chamber box with 2 subs. put a port on each side to specs. don't double the port area, or it'll creat port noise and have problems.

 

[DeuceLee 10+ year member]

if you had 2 subs in the same box, you could give each it's own chamber and give each it's recommended port size. same thing if you have a single chamber box with 2 subs. put a port on each side to specs. don't double the port area, or it'll creat port noise and have problems.

if i put a port in each side to specs and its a single chamber, that won't work because i would actually have to double the orginal lenght...

example:

orginal recommendation = 2x12x20 inches,

putting both subs in a single chamber, with two ports, one on each end will require a port size of 2x12x40 approximately EACH...right? i'm pretty positive on this but i could be wrong...

otherwise i could put each in its own chamber and its own recommended port size and lenght but would putting both of them in 1 chamber get a lower response? (just pure assumption here)

so how would one go about keeping it single chamber, single port for port area?

 

[helotaxi 5,000+ posts]

You should increase port area when you increase the number of drivers. You've got twice as much air trying to move through the port so if you don't increase the area of the port, you will have problems with compressibility and the port noise that results from it.

Doing a single box with both subs or doing each sub in its own box won't make a huge difference in response. If you are running them off the same amp, there theoretically wont be a difference at all.