Is xmax directly related to port area?

[amartin_72]

I have come to the conclusion from all my building expirience that when I have a low xmax sub they seem to like alot less port area than the high xmax ones. So hence would my proposed theory of using xmax in mm * .75 for inches of port area per cubic foot be a good starting point for my future builds? Thanks jw what some guys who really know the effect and requirments of port area are.

Ex: An FI SSD 15. 21mm xmax, 4ft @ 34hz = 63 in port area

ehqs12 9mm xmax, 2.5ft @ 33hz = 17in port area

I dont really know about this it doesnt seem to work out too well, but then what about a speaker really determines how much port area you should give it?

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[bonesninja 5,000+ posts]

short answer = yes

 

[amartin_72]

So is there a general rule of thumb that we can use or what?

 

[JimJ 5,000+ posts]

short answer = yes

How so? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[mjf 10+ year member]

atleast compare two subs of the same size........................

 

[bonesninja 5,000+ posts]

my guess is that it has something to do with the larger amount or air displaced with the larger excursion.

 

[MyFartsStink 10+ year member]

Not to thread jack, but I think I might have this problem. I got an mt 15, and the port is less than 5" deep port area is 12". Is this kind of like what he is saying? Would this cause a problem?

 

[bonesninja 5,000+ posts]

12" of port for an MT? you might as well have a sealed box that leaks real bad

 

[amartin_72]

haha yeah i was looking at your avatar and hoping that was done in MS paint or photoshopped

 

[Tehgregzor 10+ year member]

MyFartsStink....you could SERIOUSLY increase the output of your MT by constructing a new box. How much space does your box have?

 

[MyFartsStink 10+ year member]

12" of port for an MT? you might as well have a sealed box that leaks real bad

I did the math to tune it to 34 hz. Checked online calc, it said its tuned to 33. So i dont know. Is it easy to knock that other port out and put a new one in?

 

[MyFartsStink 10+ year member]

MyFartsStink....you could SERIOUSLY increase the output of your MT by constructing a new box. How much space does your box have?

4 cu ft. And I was instructed to do the porting this way, I was not sure about it, but I want to know how it sounds first.

 

[MyFartsStink 10+ year member]

haha yeah i was looking at your avatar and hoping that was done in MS paint or photoshopped

vinal wrapped

 

[amartin_72]

wow this is an emergency man that looks like a decent box you built there except for the major problem with the port, sorry to say but you need a new one.

 

[bonesninja 5,000+ posts]

try like 80-100 of port and see what sounds like...and no, its not that easy to just change the port on an already constructed box