Front or Down Firing Sub

I would never add any sub to "ideal perfect speaker". That's what subwoofers are for - to be added to inadequate speakers.

I agree that the bass my be more directional with a forward design. But not all forward firing subs are front ported. So the chaffing would not be an issue if the front firing sub was with rear porting. Also, one has to take in consideration the frequecy setting of the sub. If you set the sub at 40hz the location would be a mute point. Omni directional either front firing or down firing.
One also has to take in consideration of carpet, tile or hardwood flooring when using a down firing sub.
Either one can produce bass but there are plus and minuses to both.

(((I never thought that down firing is a good idea anyway.))
The advantage of downward firing woofers....
Imagine the ideal perfect speaker
and then you added a big forward firing port chuffing mess.
what do you think would happen to your perception of our perfect speaker?
If a woofer is properly designed, downward firing simply makes sense as there is less attension drawn to these chuffing artifacts.
Our awearness of a woofer in a system provokes a feeling
of chosing which one do I listen to?
is it compeateing for your attension?
A clean transition can happen if using a properly designed
main speaker and downward firing sub.
cheers Johnnyr

I never thought that down firing is a good idea anyway.

Sure it will work. Just attach a piece of 3/4" plywood to it's feet.

Try it out and fill us in on the results.

The best test is to try it and decide for yourself. The engineers clearly did not intend this way to use the subwoofer but that by itself does not preclude any other use. It may be louder than it was downfiring but the sub can be adjusted to accomodate this change.