push pull
 

inspired by xmax_br i'm wondering how this woofer may work in a push pull.
http://www.madisound.com/cgi-bin/ind....4610&pid=1809

i have one in a sealed box and it's a great sounding sub-very musical.but it does not have enought xmax for movies.thus buying 3 more.i was going to put 2 per 2.8 cubicft box with each woofer have it own chamber.

wondering i should be considering a push pull configuration?what are the advantages of this set-up?

When you say push pull, do you mean turning one woofer around to show its back, and reversing it's connections (it's still in it's own box), or do you mean backing one onto the other.

Generally speaking, using two woofers where they pump air together, but one is reversed, can reduce even order harmonic distortion that might be produced by the drivers if their motor system doesn't have a symmetrical travel.

Or did you mean Isobaric arrangement?

And do you want a sealed or vented box?

in a sealed box.not isoberic.one facing in and one facing out in the same box

If the cones move in the same direction, you will need a box of twice the volume, you will get a sensitivity increase of up to 6dB, the impedance will halve, and you will get a higher maximum SPL.

If the cones move in opposite directions, they will cancel each other. In an ideal world, there would be no sound from such a setup. However, I once knew someone who liked to run two 12" drivers out of phase with each other, and swore he preferred it that way. ;)

Your design seems OK as long as you wire the magnet-out driver with opposite polarity.

like this?
 

this is a kind of push-pull design.

Yes that is an isobaric push-pull. It works by doubling cone mass so Vas is halved.

Just note that the isobaric arrangemet will not give you 3 dB gain as wired in paralel convetional design. Thus you will get half the volume of single driver construction. Thast` the trade-off.