one 18" XXX compared to two 15" SE

[bangincaraudio 10+ year member]

i don't know about large margin

These are vary basic, hardly ever true "perfect world" generalizations.

Ported Box = 3dB gain

Doubling Cone Area = 3dB gain

So, two subs sealed is like one sub ported. And I've witnessed this.

XXX 18 has an SD of 1210 cm^2

SE 15 has an SD of 810 cm^2

So, if both are sealed, the pair of SE 15s would be 50% Louder

If you port the 18, you gain 3dB, and the XXX would be 50% Louder.

If you want to look at it in terms of displacement...

Two SE 15s displace about 25% less air than the XXX 18.

I dunno, only testing it can give you a true answer, everything else is speculaton.

 

[Randy Savage 5,000+ posts]

2 SE 15"s- 5.8L displacement

1 18" XXX- 7.7L displacement

Just to clarify

 

[bangincaraudio 10+ year member]

^ Yep

Edit, how much excursion linear does the SE have? I couldn't remember and used 19 in my calculations.