OK so my ICE is all installed and sounding sweet...
now i wanna know what difference its going to make if i install some sound deadedning in the doors? what does it do to the sound??

also what exactly does a cap do (i know it provides current on heavy bass beats etc) and i understand the electrical principles, but in real life is it gonna give me more bass or louder bass? i have noticed once or twice with the car idling if i have put on a cd with heavy bass that is close together the amp will cut out, until i reset it again.. will a cap fix this?

Thanks,
GuRu

Ben.....definitely get sound deadening! less rattles=better quality sound

im also curious to know what effect a cap will make as i have one sitting in my room awaiting fitment

Sound deadener stops the reflection of waves from the speaker as it hits the door and reflects back onto the speaker. If you could think of it this way, when the speaker pushes back it throws air back towards the door, but if this air then reflects back to the speaker it tries to push the speaker out when it wants to go in. It destroys mid bass and you end up with a speaker that is not running efficiently. Use deadener behind the speaker to start with and you will notice a huge difference, deaden the whole door and the sound improves again. Though not as much as if you just deaden straight behind the speaker. Focal say their deadener which is about $120 bucks for both doors improves sound by 20%, I little bit of a exaggeration if you ask me but should give you a idea that you will notice a difference

Sound deadening say a particular panel for example, also decreases it's resonant frequency. For example a thin metal door skin may vibrate at 50Hz, but if you sound deaden it you may reduce the resonant frequency to say 40Hz which greatly reduces it's tendency to vibrate during common musical notes.

Most people tend to use sound deadener more for the above purpose than to reduce the incidence of wavelength cancellation (as funky_fresian_cows explained). Oh, and also to generally make the car sound a lot better in terms of reducing NVH levels (luxury cars often have a good 50kg of sound deadener in the whole car).

OK so would something as simple as carpet underlay in the doors do anything or should u get proper deadening material? as long as it was thick shouldnt it be ok?

I think the key is Dense... not Thick!
You want it to absorb the waves not reflect them.. So but some "Dark matter" on the inside of the doors and your sterao should crank.... (mind you With all that dark matter on the car who knoews what strange happenings will be going on... :shock:

Haydn