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

[cameron paterson]

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?

 

[shadyJ]

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?

 

[cameron paterson]

Im not looking at subs to purchase was just wondering how important xmax is.

 

[shadyJ]

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.

 

[cameron paterson]

ok cool thanks.

 

[annunaki]

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.

 

[cameron paterson]

What does Sd stand for?

 

[shadyJ]

Sd is surface are of the cone.

 

[cameron paterson]

So a bigger surround can be a bad thing? It would limit the size of the cone area right?

 

[highfigh]

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.

 

[cameron paterson]

Cool ill check that book out.

 

[shadyJ]

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.