ddriggers2 said:
There is no need for speakers in the back. All it does is make the soundstage worse. In fact, our trucks can image very well if you do not run speakers in the rear.
I have to disagree. With a good set of speakers in the rear the soundstage can be made to sound excellent. Some tricks that will help the imaging are first to stuff the rear compartments with some type of polyfill. This drastically improves the low end and helps eliminate the hollow metal sound.
Next, reverse the polarity on the tweeters. This will make the speakers sound farther away. With the tweeters in the rear 180 degrees out of phase you will hear the difference.
Another trick that works well is to shift the fader to the front. On my Alpine I have the fader shifted forward to 2. I had to do this to compensate for the extra low end stuffing the rear compartment provided until I could do the same with the front.
If you have the ability, you can also cross the front speakers over at lower frequency. This will also shift the emphasis of the soundstage to the front speakers. I tinkered for a bit until I settled at crossing the rears over at 80Hz and the fronts over at 65Hz.
Last but not least is the front speakers. Their location in the door is not the best but it's not a bad spot to work with. The first thing I did was spray the inside of the door with some rubberized undercoating. You have to be careful doing this not to plug up the drain holes in the bottom of the door. This eliminates the hollow metal sound the mid bass seems to produce at high volumes.
After than I put some strips of thick foam slong all the corners inside the door. This did wonders for the bass and eliminated the need to shift the fader to the front.
Currently, I'm within 3dB from 400hz to 18khz on the RTA. I still need to add my sub and then my Eq's to finish balancing the system. I might go do the IASCA thing for a year if I ever get it finished. RTA time is expensive if you don't own one.