Ok quick note on dual vs single boxes.
As i best remember it here is the answer:
1. To ask which sounds better is extremely subjective, and more determined by type of sub, size of sub power etc.
2. 2 subwoofers in a single box will be louder than 2 separate subs sitting next to each other. I believe the physical phenomenon is called sympathetic vibration. So you will get more output from 2 subs in the same box sharing the same airspace than 2 separate boxes. This is also why you often see passive radiators in both home and now occasionally in car boxes.
3. Having 2 subwoofers facing directly at each other will probably create some cancellation waves that will reduce your output, which is why we typically will pitch or angle the subs to the back a little when we do 2 separate boxes.
4. Aesthetics vs Sound. A single box with 2 subs will be louder but which looks better and do you care?
5. Other things can help improve sound quality as well for example, Dynaxorb is a very effective way to eliminate back or standing waves in a box
DynaXorb
It's a cheap way to get more and better sound out of your subs.
Bottom line: All other things being equal a single enclosure with 2 subs should be louder than 2 single sub enclosures. There are other factors that may be more significant to determining overall sound performance than just that, and aesthetics, type of product and other factors such as sound dampening are also major concerns.
On a side note, if you take a look at some of the project cars listed on the dynamat site you will find that dynamat alone can increase your system's significantly. Every 3db is twice the volume, so Dynamat alone can increase vol by more than double in many cases.
PERFORMANCE: Airaid intake, Gibson Exhaust, Royal Purple Oils
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