I building a box for a friend for one 12" it is a honda accord, he want the most possible bass and is will to get a ported box for that. I"VE never heard a side by side comparison of a port to sealed How much more bass are we talking? thanks

It depends completely on the specific application. There's no golden rule that says you'll get 3 more dB from a ported box. If the sub performs better in a sealed box, you may get no gain.

Plus, it's going to vary with frequency. Ported boxes tend to have a strong boost around the port frequency, but below it the response drops off like a rock. You may gain 3dB at 50hz and lose 10dB at 30 hz.

And then there's the actual design. For SPL competitions, people who choose to run ported boxes tend to tune the port frequency to create a response that compliments the transfer function of that particular car. The result is strong output at 1 narrow window, and reduced output above and below it. It sounds like total ***, but does good in the SLP lines.

I totally agree. If designd well a ported box can be a good option, but takes up a lot of space and can sound bad at some frequencies. I've had a nice ported system that sounded awesome from 30-55 Hz but started to drop at 60 and completely cut out at 70. It's hard to make something like that blend with your mids, but on the other hand it was a lot louder between 30 and 50 than a sealed box would have been.

Refer to Jim's letter above for the tech stuff, it is all very accurate, especially the part about being sure if the driver was designed for a ported box in the first place. Some drivers are designed to use the cusion of air and back pressure a sealed enclosure provides, and if installed in anything but that, they will sound horrible, and probably bottom out the voice coil. I have never been a fan of ported enclosures; they are much more difficult to build, and as Jim observed, they tend to center their output on a narrow frequency band.

A good 12" sub powered by a decent amp in a sealed enclosure will provide more than enough tight accurate bass, especially in something small, like an Accord.

I agree, ported isn't always the best way to run subs. I put two 12" sub in a divided sealed box in my friends accord sedan. it's responsive and not overdone. another friend of mine has two 12"s in a ported box which poun nicely,but,it's not so clear unless it's on that one "magic frequency" .