Mounting subs outside of box?

Some of the sub manufacturers now are including air space requirements in the manual for reverse-mounted subs.  What speakers do you have, and have you looked through the manual for that info?  When a sub is inverted, it is not taking up air space in the enclosure.  You have to account for that when you build.  Also, there is some area in the cone that is added to the enclosure air space, and that, too, has to be accounted for.

If you want to use the same box you have now, you can add solid filler at the cubic inches of the sub displacement.  Glue a piece of 2 X 4, or use a brick, to take up air space that the woofer is now (inverted) not occupying.  Find the displacement of the sub from the manufacturer, and measure the items you use to amount to the same cubic inches.  Cubic feet times 1728 equals cubic inches.

Wire your subs normally, according to the proper diagram.  You can reverse polarity at the amp terminals or use the 180 switch on the amp.  If you reverse at the sub, it gets confusing and can lead to double-reversing (which accomplishes nothing).  In fact, as long as the two subs are wired the same as each other, you can experiment at the amp terminal as far as reversing goes.  It's not always going to sound best with polarity reversed.  Try it both ways and use the way that gives you the most bass response.

I have a pair of Volfenhag zx-4810 dvx subs.  I know a little about what all the specs mean, but I don't know if any of these is displacement or if I can figure it out with these.. here are the specs in the paperwork..

Fs- 27 Hz, Qts- 0.4448, Qes- 0.4745, Qms- 7.1149, Vas- 36 L, Sd- 0.0346m, Re- 3.2ohm, Nominal Impedance- dual 4ohm, Mounting depth- 152mm, mounting diameter- 235mm.   Can you tell me anything from that?

If you can't get information from the sub manufacturer on the displacement or on the recommended box volume, then that is clearly an indication that this maker does not consider sound quality a priority.  In that case, it takes experimentation.

And thanks, tbirdman, for your comment above.  I would have to say that my post above has to do only with this situation, though, and is not a general purpose response to wiring inverted speakers.  This thread is a situation where all the speakers are inverted.

In a lot of cases, installs are done where there is a combination.  Some are mounted normally and some are inverted.  In these situations, the wiring that connects the speakers is reversed on the inverted subs as compared to the normally mounted subs.