Why do subs need a box while other speakers do not?

 

Depends on the sub you get and the type of sound you want. There are even different types of sub boxes: ported, unported, bandpass, etc. Most regular speakers are just considered "free air" and are able to move freely in open air.

 

While the "other speakers" dont need a "box" they always sound much better in a baffle and not freeair. When you install a speaker in your door, which is a baffle, you are seperating the sound waves that come off the front and rear of the cone. When you hold a speaker freeair and then install it in your door you'll notice that the midbass sounds much better. This is because the front and rear waves arent canceling one another. SO even tho your not technically putting them in a box they still arent running freeair and work best in some kind of baffle.

 

Subwoofers need boxes because they need a certain amount of pressure to give sound properly....it is the way most subwoofers are designed....if you PM Lonley Raven, I'm sure he will be able to help clarify the technicalities.....

 

hehe, I'm not sure if that's a compliment or a slam! LOL

But yeah, all speakers need to keep the waves coming off
the front of the speaker from bumping into the waves coming
off the back of the speaker. You have a positive wave + on
one side, bumping into a negative wave - on the other side,
then you have ZERO wave.

Subs specifically need to be in a box not only for that reason,
but for "suspension". A sub is throwing around a lot of material,
I mean, look at a 10" sub with that big foam surround. That's
pretty heavy considering nothing but electricity is pushing it!
So the sub is put in a box so that not only does it keep the
positive waves from bumping into the negative waves and
canceling the sound out, but the air behind the sub in the box
helps support and tune it. A Sub sitting by itself on a table
not only will be really weak sounding (because of the sound
cancellation) but it would sound loose and sloppy.

That's why sub manufacturers "recommend" a specific box
size for a sub. That's to help tune the air suspension to work
with the design (weight) of the sub and what material it's made
out of to "tune" it to work well at a specific frequency.

The speakers in your doors are technicaly in sort of a box, the rear side is seperate
from the front side...but because they don't push air like a sub, they don't need to be
sealed.

 

Raven: it's definitely not a slam....like I've said before, I've got quite a bit of general knowledge about most things. But the things I know enough about to suffice, you can write a page and a half paper on.....I actually enjoy it because then I don't have to do any research for myself....just wait for you to chime in...hehe....

 

so subs that are left out in the open are a no-no, like for example to 10" subs facing up or facing out ?? it would be better if they were ecnlosed in a sub box ??

 

HAVE to be enclosed in a sub box!!

There is an exception called "infinite baffle" which means
you can mount the sub on a panel like you might find 6X9
speakers mounted on the rear deck of a car, but they can't
perform like a sub in a good "tuned" box.

 

Raven, I believe the question was referring to invert mounting (the magnets on the outside) right before your last response. The box is still acting upon the woofer, even with the dustcap side facing into it. You still have a "baffle" of sorts, the opposite waves are inside and out of the box is the only difference. That can even be corrected(to an extent of the word corrected) with the phase **** on your amp.

IB enclosures are still sealed away from the rest of the vehicle. A good IB setup will have the rear deck glassed shut with at least 6 layers of glass then the baffle board glassed to that. The entire trunk acts as your sub box in an IB setup. They're not free air.

As for back wave distortion (the condition that raven described a tad), I'll go into a bit more detail here.
First: Here is a science explaination of waves, and their functions:
http://www.school-for-champions.com/science/waves.htm

Back wave distortion, a common problem with every speaker, occurs when your speaker sends the same sound out the back as it does out the front. If this rear sound wave energy is allowed to bounce back and return to the speaker, it interferes with the speaker’s ability to operate properly causing back-wave speaker distortion.

To try to enclose the space as best as possible. Its impossibe to seal the space fully, but by using AP (aperiodic)enclosures and by using deadener to lay across the holes, we can can seal it up best as we possibly can.
Saran wont work becuase it wont keep in pressure or air, it'll let waves through as if there were nothing there.
But, if you can think of any cheap alternative to a sheet deadener that WILL block the back wave (fiberglass comes to mind) go for it! Sound deadener is definitely by far not the only potential solution!

AP stands for aperiodic. Using a foam XTC baffle is a form of aperiodic enclosure, which merely refers to restricting the backwave of the speaker.
Analogy: Inhale and exhale 2 or 3 times real quick, then do the same with your shirt covering your mouth. Feel the resistance? Thats an AP membrane at work! So, not as sealed as a sealed box, but not totally open. Less backwave gets out to cancel with the front, just like using those those aluminum plates to better seal off the door chamber. Better seal off that backwave.

There is lots of info in Audionutz (at Elite Car Stereo.com) article located here:
http://www.elitecaraudio.com/article.php?sid=21

There is more technical information here:
(lots of the information is repeated, but there are a few new things...)
http://www.elitecaraudio.com/article.php?sid=19

Sorry,this is what came to mind as I was trying to hurry through an answer I probably skipped a lot of things that I shouldn't have, but I'm late for a hair cut right now... I'll be back later to fix it.

 

You might wnat to get a baffle for your door speakers even though they don't 'need' it because the inside of the door has a resonant frequency and it might not be one you like. I discovered this the hard way when a sarah mclachlan song came on and I went ARRRGH as the howling started.

 

there are free air subs..as an example the old MTX Terminator was a free air sub......