alpinewhite

i went to a audio shop today (my friend wanted to install an alpine/pioneer nav deck to his car). so i asked him about the JL cleansweeper and he told me that the product was good, but there are other one out there that are better appearently. he told me about the Rockford Fosgate 360 and how it is so much better, blah, blah. just to let you know.

anyways, what was cool was he told me that hes going to install an alpine nav to a non nav e60.

sideeffects, i have question. does the bass of your subs travel to the cab really well or did you mod the back of your trunk? b/c the audio guy told me that i could mod my trunk by building a custom enclosure, dynamat the trunk, and cut the lining of the top of the rear windows so more bass of the sub could inside instead of bouncing off the trunk lid. total cost=1k . i would do this if i was a bass freak.

subterFUSE

There is a common problem with installing subwoofers in the trunk of many cars..... This problem is that the bass gets reduced dramatically when the trunklid is closed. Evidently, this this a huge problem with the E60. The problem is air pressure.

Ever notice that when you close the doors to a car with the windows and sunroof closed, that the air pressure makes it slightly harder to close the last door? But if the windows are cracked or open, the door closes easily. Well that is becuase the car is sealed so well that the air pressure builds when you close the doors, and the buildup in pressure acts against the action of closing the door.

Well, air pressure can affect stereo soeakers, too. In order for a speaker cone to be able to move back and forth, it must compete against the air which is pressing on it. Depending on your type of enclosure, the air pressure will play a bigger or smaller role. For example, a sealed enclosure typically has better response than a sealed or bandpass enclosure, because with a sealed box the air pressure inside the encosure acts as a damper to the subwoofer cone movement. This is why sealed enclosures require so much power.... because they must overcome the dampening effect of the air pressure.

When you port a box, you are cutting a hole which allows air to pass freely into and out of the box. This let's the cone move more freely, and therefore gives you higher volume with lower power. The tradeoff is on the accuracy of the bass response.

Bandpass boxes take this to another level, giving you even louder bass with less power than a ported design.

Air pressure inside a subwoofer box is only one factor. The pressure outside of the box matters, too. The cone must move in and out, so the air pressure inside the car can affect the volume. If you have ever been to a car stereo competition, and seen the Db Drag Racing... where they battle for the loudest stereo.... you will remember that the stereos get so loud that the air pressure builds inside these cars and the doors begin to buckle. People will stand outside the cars and literally press against the windows to keep them from bending outward from the force of the air pressure inside the car. Many of the cars have reinforced doors designed specifically to withstand this ultra-high pressure.

So air pressure has a major effect of the performance of subwoofers. When they suggested cutting the lining to the rear windows, this is an example of trying to release air pressure inside the car. (But not a method I would ever consider using) The idea is that when you let air escape the car, it will allow your subs to operate more freely.

The only thing you can do to get past this issue is to design a custom enclosure which can somehow vent the air pressure outside of the car. I think the best method would be to build an aperiodic enclosure where the membrane vents outside of the car. An example would be to remove the spare tire, cut a hole in the tire well to the outside of the car, stretch some gore-tex over the hole so that water doesn't get in the car, and then build a custom sub enclosure out of fiberglass with an aperiodic mat over the hole in the tire well. This will allow air to pass outside of the car, which lets the woofer breathe.

Aperiodic enclosures, in general, have the best sound quality of all types of enclosures. They can also be the smallest in size. In fact, the smaller they are the better they work. AP enclosures are difficult to build and tune, however.... so they are no seen very often except in ultra high-end sound quality competition cars. Finding a stereo installer who has A. Built one before, and B. Knows how to tune an AP enclosure is not easy. Only the best of the best should be considered.