Nice head unit / install. So all the factory speakers are still in place and you added subwoofer(s) / sub amp?
My C5 had the Delco CD head unit with the Bose speakers. (Front - 3" full range drivers w/ 8" powered bass / mid bass-woofers, Rear - 5.25" full range drivers) I have been contemplating taking out the OEM CD player, but wanted to keep the front speakers in place because the front Bose speakers can sound good under the right conditions. So, what I ended up doing was letting the head unit (internal 4-channel power amp) power the front 3" and rear 5.25" full range speakers. In order to interface properly to the Bose powered 8" woofers, I had to make an adapter so I could use the front RCA line output from the head unit. Most Bose amplifiers have an "unusual" input circuitry. After wiring everything up and turning it on, I discovered that there was not much bass response from the front doors although the 8" woofers were working.
After some poking around I discovered that I needed more gain from my front RCA line output. This is were the Audio Control EQL came into play and provided the gain I needed, plus equalization, which is always a bonus. After many listening tests and setting the Audio Control EQL to match the fullrange front / rear speakers I decided that I needed more "front stage". The 3" speakers in the door fire right into your leg. The imaging / staging seemed to be terrible. The high frequency response of the 3" speakers was crummy to boot. So I decided to add some tweeters for a little more high-end sizzle. As you can see, the tweeters were small enough to place at the base of the a-pillar panels.
In addition to some high frequency extension, the tweeters helped tremendously all around. Even when driving with the top down I still have good fullrange sound. Previously, with the OEM system, if the top was down it sounded horrible. The high frequencies literally went "out the window", but there was not much of them there to begin with.
CG
