Yeah, a bad analogy. The problem with your analogy is that your people
are *in* the room, and the subwoofers act *on* a room from the outside.

One of my favorite activities, even to this day, is to go to fairs and
get in the bounce houses with the kids. If you spend enough time in
these things, you'll quickly note that if everyone jumps up and down at
the exact same time, you'll get a lot higher because there really isn't
much of a place for the displaced air to go, so it compresses--which
takes quite a bit of energy to do. If everyone jumps at the same time
and with the same force, your pushing down will push up someone else
who is pushing down (and visa versa) and so the floor seems fairly
stiff.

Now, if half of the people stop jump altogether and just kinda go along
for the ride, you'll notice that the floor of the bounce house is a
*lot* spongier...when you attempt to jump, your feet sink further into
the cushion until the internal pressure balances or exceeds that of
your upward thrust. If you're really big like me (7'0", 270lbs), and if
you try hard enough, you can even hit the ground under the bounce house
if you're the only one making any attempt to jump--and that's painful.
Unlike a loudspeaker, I don't have a surround and a spider to
mechanically limit my travel, so I'm at the mercy of the springy air
mass below me.

The bounce house analogy also exaplains why you don't ever put two
drivers of a different size in an enclosure. Let's say there's me, at
270 lbs., and my 3-year-old boy who weighs about 60 lbs. or so and
we're both in the bounce house. Caleb can jump up and down all he wants
and as hard as he wants for as long he wants and it's barely going to
affect me--I'll just stand there, relatively close to the hard ground
beneath me and just bob up and down a tiny bit. Then if, while he
continues to jump, I start making large, slow movements, I'll start
"modulating" his jumps...and if he is at the bottom while I'm hitting
the cushion, I'm going to send him through the roof (and then he'll run
out of the bounce house crying and seeking hugs from his mommy :-).

Get it now?

-dan

*EDIT*

I mean to say "Round vents" not "Ported vents".

But back to the issue at hand.  The original poster's dimensions won't
work for application he's trying to use.  Sounds like he has limited
space to work with.  Using round ports vs. slotted vents makes more
sense.

E

I'm sorry..did I somehow suggest it would? My point was that it's
easier to *make* that well-constructed box well constructed when it's
broken up into discrete chambers.

I'd be willing to bet that the 10" box would be less lossy than your
3/4" MDF box. Unless, of course, you're talking about a spherical
subwoofer enclosure...in which case the thickness of the wall isn't as
important as the tensile and compressive strength of the material used
to create the enclosure. :-)

I'd rather run around for a month and not realize I had a blown driver
than to have one fail and wind up *having* to purchase two. As your
emoticon suggests, this is a pretty silly argument.

As I said...I was just being thorough. USENET is a great forum for
getting shredded for omitting obscure edge cases.

I've seen 'em with two drivers
(http://mobile.jlaudio.com/products_enclosures_pages.php?menu=8&page_id=25).
It's been a *long* time, but if memory serves, I think I actually
designed one for three JL Audio W6 drivers that used three slotted
ports.

You get lots of problems with anything if it's not done right. I get
chafing on my inner thigh if I don't put my underwear on right, but
that doesn't mean I get up in the morning and decide to "give us us
free."

-dan