Im thinking about facing my subs straight up at the glass as I have them currently facing straight out the back. Does anyone have any idea about if that I face the subs straight at the window would I gain SPL or not?

I did some testing on firing in the Festiva.. rear loaded, forward firing and firing straight into the glass (Festiva has a slopey back like the Seca).
Anyway to answer your question.. the difference in dB between rear loaded and firing into the hatch was exactly 0.0dB. Measured on the new CAA TermPro meter.

Mind you the enclosure is so big here's basically no boot space left, which will probably influences this.

[ March 28, 2003, 10:36: Message edited by: BlackIce ]

u may experience some gains if the box is built into the spare tyre well and facing up, this would be different than just turning the box on its side as there would be more space between your subs and the glass. SPL is all about testing tho.

The Seca shape is closer to the CRX shape, so going by that, try facing subs back, and ports up...

You mean subs up and ports back aka CRX box?