Since this thread has reignited the audiophile in me....I can't seem to stop the persuit to spread knowledge.
We talked about box designs, but we didn't talk about box materials. The typically "ideal" material is 3/4" MDF (medium density fiberboard). I has good acoustic properties, and holds up well to the stress of vastly fluctuating pressures. Since this is such a common material for sub enclosures, chances are, if you have one made or purchase one, it will already be 3/4" MDF....BUT check anyway. If someone is building the box for you, ask them what material they are using.
Now, despite the fact that MDF has good acoustic properties, having sound waves rattle and bounce around inside an open space (ie, the inside of your box) still isn't preferrable. This is where a little product known as POLYFILL comes into play. This is a relatively ubiquitous filling material, used for all sorts of things from pillow stuffing, to stuffed animal innards. It is cheap, and you can buy it in big bags from craft or fabric stores (like Michael's or JoAnne's Fabrics). What does it do? It essentially absorbs the sound waves that are bouncing around inside your sub box, and prevents them from having any chance of escaping and interfering with the sound waves you WANT to hear (the ones coming from the front of the speaker). If you have a box built, your install guy might not use polyfill......he might just make a box, and stick your speakers in. If so, buy some.....and fill up the box yourself. Don't be stingy with it either. You really want to load up the inside of the box with the stuff.
I bought my subs and box together as a package. They certainly didn't come w/ polyfill......so I bought my own and loaded it up.
But now.....let's say you've followed everything I've said to a T. You've got good components, you've got a proper amp install with good heavy duty wiring and a big fat capacitor, you matched your sub/amp ohm ratings and bridged properly, your box is well made w/ MDF to the ideal internal airspace for your subs and it's loaded with polyfill. But, your system STILL sounds like crap and you don't know why.
Keep this in mind: When it comes to a good sounding system, the only audio frequencies you want to be hearing are the ones coming from your system.
Herein lies the rub. Most of us aren't putting bangin' systems in a Rolls Royce. Our cars are generally more on the budget side (or at least, not super luxury cars). Most of th cars that fall into this category have parts in them that will rattle when hit with a slamming bass line. Sometimes, it is easy to identify the fact that we have a rattle issue, and where the rattle is coming from.
Other times, it's not so obvious. All we can tell is that the system doesn't sound right, and we can't figure out why. This is when it's a good time to crank up your system, close up your car......and take a walk around the outside and see if we can identify a source.
I had this problem with my Scion xB. I had everything set up ideally, but the bass sounded like hell. Was it because the frequencies and bass coming out of my subs were crappy? No...it's because there were other sound frequencies interfering that were making it seem that way. From the inside of the car, I didn't hear any rattles.....just a nasty sounding system.
So, I took a walk outside my ride. This is when I detected TWO culprits. The first was the rear wiper blade. The rear window was so close to my subs that the bass was making the wiper blade rattle uncontrollably against the glass. This translated into a frequency inside the cab that interfered with what SHOULD have been nice sounding bass. So....what did I do? I removed the wiper blade......I never use a damn rear wiper for cryin' out loud.....but I do use my expensive sound system all the time. Easy choice. THAT problem solved......but still, something else was amiss.
The second offender was my rear license plate. It was rattling against the plate holder. Now obviously, I can't get rid of my license plate....so I needed something to absorb and prevent the rattling. I decided the perfect solution was to put a few strips of 1/4" foam weather stripping across the back of my license plate. The foam absorbed the movement of the license plate, and prevented any metal against metal contact.
After performing these two simple modifications, I could not believe the sound difference. It was day and night, and I went from being disappointed with my car audio to being highly satisfied.
Now, granted, depending on your vehicle you might find that there are some rattles that are less easily addressed. If we are looking for the ideal sound system, I'd recommend lining the entire stripped interior of your car with Dynamat. Dynamat is a material that absorbs and prevents unfavorabe soundwaves. However, for most people, this is not practical because of cost (to have a whole car Dynamatted is very expensive), and because of the extra weight it adds to your vehicle. So you can expect a car that is loaded with Dynamat to lose some performance due to the added weight.
Anyhow.....that's all for this installment.
KiL