Beginner's Guide to Subs and Boxes

This seems to be a common question, so I'm going to attempt to give you guys somewhat of an idea of how to go about getting the right setup.

First off, before anything else, consider the type of music you listen to.  Do you listen to mostly Rock?  Rap? Country? How about Polka?  All of these can determine the type and size of subwoofer you'd be best suited for.  If you want punchier, quicker and clearer sounding bass, go with a smaller subwoofer, such as an 8" or a 10".  For mid-type bass that isn't quite as boomy as a 15", but not as punchy as a 10".  It is considered to be one of the most common types of subs used, for the fact that it can be well ranged if you pair it with the right box.  Last, you have your big subs.  These are the 15" and the 18".  Bigger subs then this exist(21", 25", 30"), but for all practical purposes, 18" is the biggest you will EVER need.  Kicker makes an 18" SoloX that's just ridiculously loud when used right.

So now that you've started to get an idea of what you'll be listening to, there's a few more variables to consider.  Boxes.  There are three main types of boxes you will use: Sealed, Ported, and Bandpass.  A sealed box is generally a smaller box(uses less airspace in it's design, therefore smaller in size), and is generally used to deliver a punchier bass.  Most rockers find that they are quite happy with the sound delivered by a 10" in a sealed box.  A ported box has a port that allows air to flow in and out of the box.  These boxes are generally louder then their sealed counterparts, but they can deliver a muddy sounding bass if not tuned right.  The ports have to be tuned to a certain roll-off frequency(where the sound response level diminishes as the bass gets lower), so you want to make sure you don't shortcut yourself on that.  The last and final type of box(for the purpose of this brief introduction), is known as the Bandpass.  It's pretty popular with most dB draggers(it can usually squeeze a few extra dB's from a sub).  It is a combinated of a ported and a sealed box.  It has two chambers, and the subwoofer is mounted between the two.  One of the chambers is ported, the other is sealed.  I've never used one of these before, and I've been told that they will tear your sub up pretty quickly.  They also run the risk of sounding like a one-note system, due to the narrow response band of frequencies that the sub will play.  There are more types of boxes that are out there, as well as variations(called orders) of the same box.  I could get into the physics of the soundwaves propagating through the box and the different designs you can use to maximize them, but that would more then likely bore the average reader.  If you are interested, there are several excellent books out there that will help you out in that particular area.

There are two main types of qualities you look for in a subwoofer setup.  They are commonly referred to as "SQ", or "SPL".  Generally, SQ(Sound Quality), is sought after by the more discriminating listener.  These subs have a quicker response, generally put out less bass, but they match the levels of the other components of your system(such as tweets and mids) and they won't usually tick off the people in the car next to you.  SPL(Sound Pressure Level), as you may have guessed, is the opposite of what SQ is.  It is generally referred to as "bone crushing, booming and frequently annoying bass levels."  This is what dB drags are all about.  Most people think they can just find the biggest amp, the biggest sub, and slap them to a bandpass box, and they've got it all.  Those people are wrong.  You need to carefully design out your box and figure out what frequencies you'll be listening to, the type of music you want, and the quality you're after.

Finally, you want to always consider your amp.  This can easily be the most expensive part of your subwoofer setup.  You want to make sure you buy an appropriate power of amp to match your subwoofers.  You don't want to crank too much wattage to them, or they'll burn up.  Generally speaking, a sealed box is more forgiving to subwoofers that are stressed by the amps, because of the fact that the air sealed in the box behind the subwoofer acts as a spring so that it is harder for the woofer to exert itself.  Downside to that, is you will lose some dB's.  There's so many things to consider in a setup if you want quality.

Sorry for making this so long, but there's just some important things that everyone should know about making a proper choice for subwoofers and the system that powers them.  I realize how scary all these choices can be, so I've went ahead and made a little table for you to refer to as sort of a cheatsheet. =)

TYPE OF SUB                     BOX                       TYPE OF SOUND                       MUSIC

8"                                          Sealed                   SQ                                                Rock

10"                                        Sealed                   SQ                                                Rock

12"                                        Sealed                   SQ                                                Rock/Rap

15"                                        Sealed                   SPL                                               Rap

8"                                          Ported                    SQ                                                  Rock

10"                                       Ported                    SQ/SPL                                          Rock/Rap

12"                                       Ported                    SPL                                                 Rock/Rap

15"                                       Ported                    SPL                                                 Rap

8"                                         Bandpass             SPL                                                  Rock/Rap

10"                                       Bandpass             SPL                                                  Rock/Rap

12"                                       Bandpass             SPL                                                   Rap

15"                                       Bandpass             SPL                                                    Rap

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To find out more about box design, refer to the page on box design on the12volt's diagrams page.  Just look on your left. =)  And as always, I'll be more then happy to assist you with any questions you might have as well.  Just PM me, and I'll give you my email address so you can get ahold of me anytime.  Sorry if any of this information seems to be incorrect, just tell me and I'll make the proper changes!  You can feel free to make this topic sticky or whatever, I don't care.  I just hope this helps out some of you newbies make the right choice when searching for the right subwoofer setup.

Hope this helps you out...

--mindctrl

It's a great write up and I don't doubt your experience. I agree with your general philosophy regarding the sound engineering involved.

What I don't agree with is the generalizations of what music will sound better with what subs/boxes. It's not you I disagree with, I've heard this before and I've never believed it.

I don't argue the fact these sub/box combos will produce and entirely different sound from one another, I know they do. I believe it is an induvidual preference as to how one prefers to listen to thier music.

I can only speak for myself here, but I like my music to sound just like I'm seeing it live.

One person can build a ported subwoofer and get it just right...and typically listen to Steely Dan on his commutes.  Someone else can have a system with a sealed box and typically listen to Chemical Brothers.  And vise versa.

It's a monumental effort to sort the characteristics of "sealed vs. ported" and lay it out here as textbook, but it really doesn't work when summarized so briefly.  But it is a worthwhile start for those who are just beginning, and it doesn't hurt that it has some controversial opinion because we all know that controversy sparks debate...and arguments lead to further research.  As example, the classification list of speaker sizes-type of system-type of music that was listed. 

In life, we tend to try to duplicate what we have experienced.  When we are wowed by a system that is ported, we try to make one similar for ourselves.  If we are entranced by a sub system that is in a sealed enclosure, we regard that as the pinnacle of proper sound and establish the concept in our heads that sealed is the way to do it.  I, personally, think that I can get the sound I want from either sealed or ported, as long as the driver will work in either type. (I'll leave bandpass out of this because it is very specialized).  It's a matter of getting perfection out of the project.  The final results cannot be qualified, because sound is always a matter of individual opinion.  And I can't change my subs because I've switched tracks from one genre of music to another...

It takes time and homework to get anything down right...and anyone who puts in the time and effort, even if just on this website alone, is going to come out of it with a sense of direction, and a clearer purpose of how he can achieve the sound he wants in car audio.  Anyone who is considering building a system...highs and lows...for his car has to put the time into the theory of it all before buying and building.  He need to understand what a ported enclosure actually does, and what a sealed enclosure actually does...and it takes time and effort.  Those who put in the effort are the ones who come away winners...not winners of contests, but winners because they have put together a sound system that they are proud to show off to their friends.  And they can spend long satisfying hours driving while listening to music that sounds just right.

Hmmmm, I'll not pick on you to much.  There are just so many variables to consider.   One I think you overlooked is the size of the vehicle.  The sound of a 8 inch sub, in the same box will sound different depending on the vehicle it is placed in:  My suburban, Subaru legacy, Honda civic, K10 regular cab Chevy truck.  Considering you have optimal placement in each situation.

What I consider the most important factor (correct enclosure design excluded) is the driver itself.  The driver (enclosure aside) will have the biggest impact on the product.  I've seen 8" that could fool you into thinking they were a good 10" and 15's that would not pass for a decent 10.

It is not a single factor formula:  Driver + Amp + Enclosure = great sound.  All other things being optimal.  Take one of those things in the formula away, replace them with something of significantly lesser quality and you have:  Cheap Driver + Great amp + Great enclosure = crappy sound, or Great Driver + Great Amp + sh*te Enclosure =  Absolute sh*te.  Hard to get around it.  Things should be balanced, dont get the 99 dollar subwoofer and mate it to the 699 dollar amp.

To me, when choosing a subwoofer, take into account the following:  Budget, size of vehicle, type of music listened to, amount of space to give up, other factors (do they already own some of the equipment they want to use, are they being realistic, do they plan to do future upgrades like adding another sub).

Personally, I switch music allot.  The mp3 in my head-unit right now is a mix of Oasis, Phil Collins, 50cent (half a dollar), Affroman, John Mellencamp, Credence, Good Charlet, some acoustic and live Oasis and Billy Joel, other sh*t.  A good sub can reproduce almost anything with a pleasing fidelity.  I always say:  Get the best you can afford and you will not be sorry.

Thanks for all your replies :)  I didn't mean to by any stretch of the imagination provide a strict guideline for designing boxes.  I do realize that there are many variables you have to take into account.  I merely provided some starter information for the new people to look at and derive some information as to what to decide on in the design process.  By no means did I try to pretend I know everything!!  :D

Anyway, just keep those comments flowing.  It helps to have my work commented on and criticized, so that I may learn something new myself and hopefully add to my knowledge :)

Later,

--mindctrl