Thanks Guys
These particular speakers have a very large diameter magnet and need at least 3 1/2 inches of mounting depth. The three things that I had to consider when trying to decide where to mount were:
1)Will the speakers fall within the recessed area of the plastic interior panel so that they will be on a flat mounting surface?
2)Is there room in one of the tailgate cavities for the speaker magnet?
3)Will all 4 speaker mounting screws tap into the metal tailgate structure? This is very important because the interior panel is very flimsy and only held on with snaps!
Taking these criteria into account and after a lot of measuring, the location you see is the ONLY place these speakers would fit. And they had to be mounted horizontally in order to achieve #3.
The 3/4" spacers provide just enough added clearance for the magnets and also prevent the plastic interior panel from bowing in when everything is tightened down.I used 2" screws to mount the speakers. They go through the speaker mounting flange, the plastic interior panel,the spacer and tap into the metal tailgate structure. This pulls everything down tight.
These babies vibrate everything, even the tag, so while you have the panel off, tap on everything in the tailgate looking for rattles and do the "Chuck thing"! When I have time, I want to go back in the tailgate and deaden the interior side of the sheetmetal with Stinger RoadKill spray to cut down on vibrations. Also I want to try and create 2 distinct enclosures within the tailgate. Maybe a couple of pieces of tubular pipe insulation placed vertically on each side of the square center hole where the latch is located? Another interesting experiment would be to cut some tuned ports in the lower right and left corners of the plastic interior panel and turn the tailgte into a bass reflex enclosure.
I don't know if the speaker selector switch was really necessary. You could just unplug the wires at the 4" speakers and extend them on back to the tailgate. I probably won't switch to the 4" speakers anyway. I don't think it would be a good idea to wire them in series with the 6X9's.
These speakers are very efficient (93db) but they are WAY back there and screaming for more power! I'm using the stock head unit but now I've got the hots for an after market unit with lots of clean power! That would really bring these speakers alive!
I installed these speakers mainly for sounds from the rear of the van when we are standing around behind it with the liftgate up. When driving I prefer the soundstage in front, but dialing these in just a little does wonders for the overall sonic effect!
With the third seat up, some of the highs are absorbed, but not to the extent I expected.
OK,one of you guys take this to the next level. Install a set and spend some time deadening and tuning the tailgate enclosure so that they go as deep as possible. Install an amp and a low pass filter, rolling off everything above say 200Hz thus creating a built in sub. Flip a switch to loose the low pass filter and, bingo, back to full range.