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using a sealed enclosure (IF your Qts allows for it) you'll need twice the power to have equal output to the same sub in a ported box, since both sealed-to-ported and doubling the power give ~+3dB gain.

If you're using a 15" sub, it's going to sound bad no matter what you do if you want it to play above about 80Hz at most. It's a large sub, and the higher the frequency you try to make it handle, the more you're going to get cone flutter and that'll lead to a boomy sounding enclosure with poor performance for SQ. The impedance of the driver is also going to rise as the frequency rises. Remember that cone has a lot of mass to it, and the faster you try to make it move back and forth, the more control that motor is going to have to have to do so effectively. A large sub is made to play low frequencies. usually 60Hz and below. The most common mistake people make with a large 15" or 18" sub is trying to cross it over too high.

If you want to build an ideal sealed box, use this math to do it:
Optimum volume for sealed enclosure (cubic ft ):

You may substitute any Qtc between 0.50 and 1.50 in place of 0.70 in both equations (both must have same value) to experiment with enclosure size. Qtc of 0.70 is generally considered an optimum alignment, with very good transient response, low cut-off frequency, and flattest response to the cut-off - See Qtc.

Note: You must always choose a Qtc higher than the driver's Qts!

Find alpha: X = (0.70 / Qts)^2 - 1

Then calculate enclosure volume: Vb = Vas / X

System resonant frequency: Fcb = 0.70 / Qts ( Fs)

To find the theoretical cut-off frequency, use the following chart to find the F3 factor:

Qtc F3 Factor
0.50 = 1.55
0.60 = 1.21
0.70 = 1.00
0.80 = 0.90
0.90 = 0.83
1.00 = 0.79
1.10 = 0.76
1.20 = 0.74
1.30 = 0.72
1.40 = 0.71

Then: F3 = Fc x (F3 Factor)

"My subs are crossed at 250."

ok those aren't subs then. those are woofers. subwoofers cover the bottom two octaves only. that's 80Hz and below.

boomy defined. go find a ported enclosure tuned to 45Hz. you'll see exactly what boomy is. explaining sound with text is a lot like trying to explain a color to a blind person. It's difficult at best.

I like the midbass my subs are able to produce now, if one set of 6 1/2s will give me the same mid bass then thats fine. My subs are crossed at 250.

Ok so its basically what I thought, a large sealed box would just make it easier for the sub to produce low notes making it more "boomy" or what do you mean exactly by boomy, not distorted, do you mean not as dense for lack of a better word and sort of spread out. like a drum beat is tight and a rap bass note would be boomy?

Is there a specific reason you want to go sealed and not ported?

I used to always want to go sealed as well until i built a ported box for my L7. Anywayz, generally a large sealed box gives u a "boomier" sound whereas a small sealed box gives a tighter bass sound.

other wise id need to have 8 6 1/2s mid basses or like 4 8" adire koda midbass speakers.

Why would you need that many midbass's? Just have a good set of midbass or components in your doors (or kicks) and a good rear fill speaker.

TEDD

yeah but he has a ported box, i wanna run mine sealed so it will need significantly more power to be as loud correct? and kiki I want to find subs that will handle my midbass part too because other wise id need to have 8 6 1/2s mid basses or like 4 8" adire koda midbass speakers.

Can someone explain about making a large sealed box, some people said my subs will sound crappy, if I make a large sealed box (bigger the box, less power needed correct?) My cousin has a huge sealed box, id say atleast 2.5 cubic feet per chamber and has 2 sony xplode 12s in it, they have a huge amount of midbass but dont sound too good compared to my infinities, but they arent horrible.

roughly 145 or so... (in the current box)

I wonder what bill's brahma is capable of with the full RMS thrown at it...

working frequency range is pretty pointless.
any sub in a good enclosure will reach 20Hz, and you'll have them crossed over at 80Hz or lower for subs. midbass should handle above 80Hz.

ridr4lif wrote: Consider this, the Adire Audio Brahma 15" has an RMS rating of 1600 RMS, and William from Nola is running 600 watts to his and he's hitting in the low 140's.

I like being your example :)

Remember...RMS is only a thermal rating. It expresses how much heat the voice coil can handle in watts.

SO...in a properly made enclosure, the SX's should sound very good. Consider this, the Adire Audio Brahma 15" has an RMS rating of 1600 RMS, and William from Nola is running 600 watts to his and he's hitting in the low 140's.

Hope this helps a little.

TEDD

the thing is i would go with 2 sx's but thats 400 watts under the rated power Id be giving them, and 3 se's would only be 200 plus id also gain a little from another drive :) thats the reason im thinkin about that. I cant find the working frequencies for the RE drivers anywhere, some drivers can play 20-200 hz some like the sonys play 20 - 1000 hz, what kind of sub plays at 1000 hz lol. Id be very happy with a a setup where I can hit around 135-140 dbs, i dont think ill ever need anything higher.