Need help calculating the encloser size (Sphere)

[sledox]

Hi there,

I'm calculating a case size for the first time and I haven't quite understood a couple of things yet. I also included a photo.

I have a sphere with a diameter of 50cm. Corresponds to a total volume of 65L.

I would like to install a 12 inch woofer there.
Now I have found such a table on the Internet:

Woofer Size Enclosure Volume
4 ".25 - .39 cubic feet
6 ".35 - .54 cubic feet
8 ".54 - .96 cubic feet
10 ".96 - 1.8 cubic feet
12 "1.8 - 3.5 cubic feet
15 "3.5 - 8 cubic feet

According to my calculation, with a volume of 65L I come to 2.3 cubic feet. A 12 inch driver would fit.


Now we come to the second part in the photo. Because I somehow have to build the drivers into my sphere, I have to make sure that one part has a flat surface.
My 12 inch driver would now come in there.

Now I only have a remaining volume of 39L or 1.3 cubic feet. If I go according to the table, would a 50cm diameter case still be too small for a 12 inch driver, or am I getting that wrong?

 

[GM]

Well, the driver itself will further reduce its net volume [Vb], so the driver's T/S specs will determine just how too small it is, though with today's DSP it can be frequency shaped to basically whatever its specs indicate it's capable of, but in speaker design we're always trading efficiency for BW when making less than optimum size cabs, so it will probably wind up being very inefficient [low average/peak SPL].

 

[sledox]

Ok and how big would my enclosure have to be in this case if a 50cm diameter is not enough?

 

[AllenB]

What can you tell us about the driver?

 

[GM]

Ok and how big would my enclosure have to be in this case if a 50cm diameter is not enough?

Again, without driver specs, I have to fall back to the chart's largest net volume [Vb] = 3.5 ft^3 and even then only for sealed, with ~5 ft^3 minimum for vented.

 

[sledox]

Well, the driver itself will further reduce its net volume [Vb], so the driver's T/S specs will determine just how too small it is, though with today's DSP it can be frequency shaped to basically whatever its specs indicate it's capable of, but in speaker design we're always trading efficiency for BW when making less than optimum size cabs, so it will probably wind up being very inefficient [low average/peak SPL].

I have not yet selected a specific 12 inch driver, so I can't give you any data. I just wanted to see whether I can basically build a 12 inch driver into a 50 diamenter Sphere.

Do you think it would be possible with enough DSP to build a 12 inch driver into this case and it would sound good?

 

[GM]

Physically, yes if your calcs are correct.

Don't know for sure without driver specs and what's available range wise with current [inexpensive] DSPs [no clue], but will be a fairly quiet speaker from at least below its upper mass corner [2*Fs/Qts'] where T/S theory peters out and the driver is just mass controlled and maybe even higher depending on its XO point/slope.

Spec wise, you ideally want a driver with an [Fs] at whatever low frequency you want to produce with the lowest [Qts] and [Vas] as small as can be found in your price range to maximize efficiency with the understanding that this will be a relatively expensive driver by design, i.e. a prosound horn woofer designed to have a relatively tiny rear chamber and powerful enough motor to drive a wide BW compression horn.