You will often see a lot of people using 6x9?s and subs and boasting about there systems loudness, this is all very well if you just want sheer volume and no quality. What they don?t know is that having the combination of 6x9?s and subs is not only playing games with the sound staging in your car but could also damage the units themselves!
Point 1 Max Excursion Limits vs Air Pressure!
This is probably the most important point out the two.
Have you ever put your head in someone?s boot whilst they have the sub banging out some tunes? You can feel the air moving around and the pressure of the subs is normally pretty large!
This is as the sub creates a band pass box using the air inside a closed boot, hence why most cars without 6x9's sound better inside the car then with the boot open!
Now 6x9's have what is called a maximum excursion limit this is how far the cone can move up and down.
With them in the shelf and the sub in the boot you can imagine the amount of air pressure being put on the 6x9s. With the sub moving so much air it will push and pull the cone of the 6x9's causing them to not sound right but also moving them past there excursion limits and can cause them to break.
Point 2 Sound Stage
Sound stage is very important in the car as to be honest you don?t want to be able to hear which direction the sound is actually coming from, you will want it to sound like the car is filled with volume.
You sit in the front of the car? correct? Yes! So why would you want to have all this lovely sound in the front of your car only to install 6x9's and have the sound dragged into the back of the car?!
I normally give this example to try and prove me point: When you go to music concert you don?t stand there with your back to the stage do you?!
You want to try and have the music in front of you so it?s like a mini band playing on your dash board.
In larger cars then some rear fill maybe required so a pair of coaxial speakers in the rear door cards can help. But if your fronts are good enough then they should be able to fill the car!
not my own explanation, but it saves me typing it all out