Trying to figure how to test the power and frequency bandwidth on a stock 07' Subaru Impreza radio? The car came with 5 1/4" front speakers that I added the factory tweeters to, and 4" rear's. Both are in the bottom of the doors. The rear 4" speakers didn't sound full range, but figured that could be the speakers(size) and location. I don't need ear splitting sound, so just want to tweak the factory system. I tried putting an 8" DVC woofer to the rear, disconnecting the 4"ers, and since I like bass that moves air, not booms or thumps, and being a compact station wagon, I didn't want a box, so I built a flat baffle attached to the rear shock towers. It sounded no better, so I started to enclose it, first with an empty cardboard box I could easily remove, and could reposition the speaker baffle if I had to carry something big. I stuffed the box, and it still doesn't sound any better. I think the rear ch's of radio amp might not be full range. On a Subaru forum I get replies that it is, or to get a new radio. Being a DIY'er That would be giving up.))
The freq res of the 8"ers is about 33-4Khz, but it sounds no better than the stock 4"ers. I tried some 6x9" ers I have in a sedan, that has great bass, and fairly wide range, that I had planned to put in the Subaru, but hate to loose what I have in that car. They are in the rear shelf so isolated from the interior, but I should be able to get better sound with the 2 speakers I tried than 4"ers, even in a crude box.
I have a test CD that I could use to play frequencies through the system, and thinking I should be able to use a DVM to see what the output is across the range.
The front speakers aren't bad, though I still want to tweak them, but want to fill the cabin more, and I tend to like sound coming from the rear for some reason. The front tweeters are high on the door panel so the highs are not buried.