How much does xmax matter for SPL in a ported box?

  • Thread starter Thread starter cameron paterson
  • Start date Start date
C

cameron paterson

Audioholic Chief
Mar 7, 2018
907
0
18
48
How much does xmax matter for SPL in a ported box? What if 2 subs both handled 1000watts and used the same amp. But one had 33mm of xmax and the other had 22mm of xmax. Would the 33mm sub have more output in a ported box?
 
There is just not enough info for anyone to say it matters. There is a lot more to drivers than Xmax. What are your goals and what drivers are you looking at?
 
Im not looking at subs to purchase was just wondering how important xmax is.
 
Im not looking at subs to purchase was just wondering how important xmax is.
It's important if you are looking for long-throw subs. The reason why you would want a sub like that is for deep frequencies, so for that purpose, the more Xmax, the better. But Xmax alone still wouldn't tell the whole story there.
 
ok cool thanks.
 
IF all else is equal (it usually isn’t) more xmax = more displacement of air

More air displacement = More SPL

If you have the same Sd, assuming the motor is up to the task the driver with more Xmax will be louder.

33mm vs 22mm xmax is a 50% increase in movement. Theoretically the one with 33mm can play louder.

Lots of variables though so the answer is not always so simple.
 
What does Sd stand for?
 
Sd is surface are of the cone.
 
So a bigger surround can be a bad thing? It would limit the size of the cone area right?
 
So a bigger surround can be a bad thing? It would limit the size of the cone area right?

Depends on why it's larger- I have seen some large surrounds that were on drivers with low XMax- if it's wide and flat, it's probably going to be lacking in XMax but there's no absolute for that.

Think of a speaker cone as a piston- it displaces a certain amount of air, based on surface area and excursion but as mentioned, there's a lot more to a driver than XMax.

There's a lot of info about drivers online and in books- The Loudspeaker Design Cookbook by Vance Dickason is a good one, although don't know what has been added since I got my copy over 30 years ago.
 
Cool ill check that book out.
 
Loudspeaker Design Cookbook is a great resource. However, after the first couple chapters, it becomes very technical. If you are looking for something that serves as a great introduction to driver designs, Audioholics has this excellent article.
 
newsletter

  • RBHsound.com
  • BlueJeansCable.com
  • SVS Sound Subwoofers
  • Experience the Martin Logan Montis