This is to be taken as a basic, beginners guide to “what bass actually is, how its reproduced, and how to get it sounding great in your car stereo system”.

Its long, yes, but each stage gives you knowledge you'll need to understand the
next step, so its worth a read.

If you’re a beginner, you may encounter some new terms in this article.
Read the whole thing first, and if you have any questions theres plenty of other tutorials to look at. Use the search funtion, theres plenty of information in the past…but if you cant find what your looking for, or you just don’t get it, please feel more than welcome to ask on these forums, or message me personally.

This explanation assumes your using 6” or 6.5” splits, and a subwoofer.
This sort of system provides whats commonly agreed as the best range/coverage, and ease of setup.

This is a set of splits, pictured with their crossover unit.
You can see a big woofer (one with a grill on), small tweeters, and the crossovers.


A subwoofer. Note the massive magnet on the back. Its designed for bass.



Frequently, people ask these questions about bass.

“Do I need a subwoofer?”
“A subwoofer makes all the bass, right?”
“What do I need for good sounding bass”?
“I listen to jazz, classical, do I need a subwoofer for good SQ?”
“I don’t need a subwoofer if I have 6x9”s, do i?”

First of all, I’d like you to think about why we buy splits/coaxials.
Different size speakers, of different constructions and materials, are better at different things, right?
You all know, for instance, that tweeters are given the task of reproducing high frequency sounds. Cymbal clashes, for instance. They are designed for it, and they do it well.
They don’t play lower. They don’t put out that deep bass.
They aren’t designed to.

Similarly, the 6 or 6.5” woofer component of these speakers, has a purpose, a design.
Playing mid-bass, and mid-range sound. From around 100hz upwards.
They can play lower, but they wont put out that deep bass. Generally.
They aren’t designed to.

A subwoofer is used to reproduce, accurately, all the frequencies below around 80-100hz that splits/coaxials aren’t designed for.
This is called “sub-bass”, and this frequency range covers two entire octaves of music.

Think about that for a moment.

“Do I need a subwoofer”.
Its ultimately up to you, but theres two whole octaves of music you may be missing out on without a subwoofer.
But wait…bass has more than two octaves, right?
Theres surely a bigger gap than that between those gut wrenching low club beats, and the rich tenor of a bass clarinet?

Absolutely.

“A subwoofer makes all the bass, right?”.
As we just learned, no, not quite.
Heres a little more info for you.

“What is bass?“.
Once you know this, you can figure out how to get “good sounding bass”.
I’m going to arm you with some technical information now.
With it, you’ll be able to easily understand how our audio systems reproduce the lower range of frequencies.

For our purposes, bass can be split up into a few frequency ranges.

Sub-bass
Sub-bass is low. Its responsible for that “whump”. That pressure in the back, that body reverberating driving bass. That low low resonance from a wind instrument, or a timpani. The rumble of thunder, or the smooth flowing harmonies of a orchestra.
The funky jive of a bass guitar. You name it.

20hz (lower limit of human hearing) up to 80-100hz is commonly referred to as “sub-bass”. This is bass that you can hear, perhaps feel.
Due to the way we have evolved, humans cannot tell the location from which such low frequency sound originates. It is emanating. Its omnidirectional.
This is why a well set up sub in the boot of a car may not sound like its in the boot, the
Bass may surround you.
Higher frequencies become more and more locational, anything above 100hz, and you can tell where the sound is emanating from. You can test this. I’ll tell you how later.

Mid-bass
Mid bass is a bit higher. 80-400hz. Its responsible for the rythym, the detailed harmonies.
More importantly, its where most of the “kick” happens. When a bass drum beat happens, you get the low thud, but also that sharp “kick”…
The smaller woofers, the 6” – 6.5” ones, specialise from 100hz up to at least 1000hz, and hence, mid-bass is entirely their domain. When you feel that body shaking rumble, that’s the subwoofers. When you get that clear, sharp, punch in the chest “kick”, that’s mid-bass, in all its glory.

Mid bass speakers (the big ones, pictured with tweeters).
Anything higher than mid-bass we don’t need to worry about here.
We know high end frequencies are handled by the tweeter.
The tweeter can suprisingly make a difference to how your “bass SQ” will sound.
More on that later.

Now, mid-bass is directional. Your brain can tell what direction sounds are coming from when they are between about 100hz and something stupidly high. 12khz....or somesuch. Anything below 100hz, like a subwoofer, and your brain doesnt know which direction the bass is coming from. This is one reason why a subwoofer mounted in the boot can sound fine in the cabin, your brain doesnt really know the sounds coming from behind.
In fact, a well setup car can make the sub-bass sound like its coming from the front of you. I’ll explain how soon.

Crossover points.
Lets say you have a crossover point (Theres actually two types, but more on that later).
Lets say you set a crossover point at 100hz.
You can make it so that all music below 100hz goes to the subwoofer, and nowhere else.
Hence, all music above 100hz would go to the front speakers.
In this way, you can make sure that directional frequencies are not played by your sub.
You can test this directional theory, by the way.
Its simple. Just set a crossover to about 80hz, and listen to a system.
The set the crossover to 400hz, and see what happens. You’ll immediately feel the sound coming from behind you. You will definently feel as though theres a muffled speaker in your boot, because your now playing directional sounds through the sub. You don’t want that. You want all the music up front, where you are.
(there are two types of crossover, low pass (all frequencies below this filter pass) and high pass (only frequencies above this filter pass))

Think about it.

“What do I need for good sounding bass”?
“I listen to jazz, classical, do I need a subwoofer for good SQ?”

Would a bass drum beat sound crap if it was muffled?
Yes. You'd only hear low frequencies.
Low frequencies are what your sub makes!

Would a bass drum beat sound crap if there was no bass, but just the holllow kick?
Yes, you'd only hear that sharp, detailed kick, no low bass.
Wait, kick, midbass, that’s what your front speakers do!

Get any great sounding bassy system, and turn of the front speakers. It will sound muddy, not detailed.
Get that same system, and turn off just the subwoofer. It will kick you in the chest, you’ll hear the detail, but it may sound a little…hollow.
Can you imagine hearing a cello, minus that deep, smooth, reverberating bass?
Can you imagine a phat club track, without that body rocking pressure wall of bass backing the beat?

So. What do you want?
Why, of course, you want these two components to blend together, don’t you? You want the deep bass, but you want the kick.

Bang. There you go. [B]“Do I need a subwoofer?”[/B]
You just found out that a subwoofer by itself is simply not going to cut the mustard when it comes to bringing the detail out in that music, but it will fill it out.
You also found out that the front component speakers just cant produce the full range of rich sound by themselves either!

So again. “What do I need for good sounding bass”?

For SQ, you want all your speakers to blend together naturally.
In a properly setup SQ system, you shouldnt really be able to hear the subwoofer as a seperate, overpowering speaker. It blends in, and fills out those lower 2 octaves of music, and because those octaves aren’t directional, somebody with less knowledge shouldn’t even spot theres a subwoofer in the system.
They’d just be wowed by a smooth, even range of music that happens to extend deep down into the bass, naturally.
Of course, you can always turn the sub up when your playing that club song, and let everybody for a block know that yes, indeed, you have a sub In the boot 

For SQ, its all about making them blend nicely together.
So, congratulations, you just found out the basics of good bass, and why you really do need a subwoofer.

Sub-bass and mid-bass are very different creatures, and each are equally important.

“I don’t need a subwoofer if I have 6x9”s, do i?”

Heres a picture of 6x9”S. Note the oval shape.


Some people choose to use 6x9”s to get “big bass”. 6x9”s are commonly sold relatively cheaply, and are advertised as being able to play “deep bass and crystal high notes”.
Not so. Most 6x9”s, while having large surface area and being able to play low, simply wont sound nearly as clear, go as loud, or quite as low as a subwoofer.
Also, because they are trying to play the entire spectrum of sound, they won’t do it all very well. In regards to bass, it will sound muddy, compared to a dedicated subwoofer, and because they are usually mounted behind you and playing directional frequencies, they will drag the sound backwards, not what you want.

If you use 6x9”s WITH a subwoofer, any frequencies that both speakers make, will interefere with each other. You’ll get cancellation, which means by a trick of physics, you wont even HEAR some bass frequencies. The 6x9”s and the sub will generally interfere with each other, and reduce your overall SQ.
Given musics composed of so many frequencies playing at once, your more likely to hear cancellation as "muddy and/or boomy" sound.

Then again, there are some 6x9”s out there that are very good quality, but as we’ve learned, using a few speakers, each dedicated to producing a certain frequency range (sub-bass, mid-bass) will yield better results for SQ.

Also, an oval speaker by its construction does not flex evenly. Slow down a bass-heavy speaker enough, and you'll see the cone is not quite rigid.
It "flaps" a little. A oval speaker, doesnt flex evenly, which leads again to distortion.

That said, heres another opinion about 6x9"s.
Either of the two methods would allow 6x9"s to be used with minimal interference.
In reality, you can observe 6x9"s on a parcel shelf moving, even if they are turned off, on big bass beats. The sub does interfere with their movement.


Installation – How to get it sounding awesome.
A very, very basic guide.
Now, some information about installation.
The theory is only part of a good system.
The money spent on speakers, is only part of making a system sound good.
Installation is frequently the key.

I will make this bold statement with full confidence.
Both the performance of a subwoofer, and that of the front speakers, will ultimately be entirely dependent upon installation.

A set of $600 speakers, mounted craply with one screw to your doors, leaking air all around the edges, will not have nearly as much SQ (midbass "kick", overall richness to the sound) as a $150 pair of speakers that are well installed. That are sealed to the door, with no air leaking around that will steal away your bass/SQ.
Of course, $600 speakers mounted well should shine.

You can get “pods” made for your doors. Think of these as holders that attach to your door, and hold the speaker. Theres an few images of a “pod” here.



These let you angle the speakers up and towards you which, given that these speakers put out directional frequencies, can really help your SQ.

Now, you may know that playing around with the position of a tweeter can change where you think a stereo’s sound is coming from. If you covered the tweeters, things would seem muffled, if you put them up near the glass, they might reflect off it and sound harsh. A tweeter will affect to a large extent how you percieve sound from the mid-bass speakers, and the mid-bass speakers will hugely effect how you percieve the sub-bass.
Not to worry, because your mids are up front, and the detail is therefore up front, so your brain (not knowing where the sub-bass is coming from) will assume its coming from…you guessed it…up front. BASICALLY. There are various ways to enhance this sensation, but you get the drift.

Sealing and sound deadening are two major factors in front speaker, and hence, midbass, performance. Theres a lot of information on these concepts around the forums. Search.
Pic of sound deadening on doors.


Most subwoofers are designed to be run in a box. There are two major different types of box design. Sealed (simply, a sealed box with a hole your sub slots into) and ported (same as sealed, but theres a very specially made hole in the box with a port in it, a port which is specially designed to work with that particular subwoofer,).

It's all about the box

As subwoofers are generally made to be run in a box (there are a few exceptions), the strength, and internal volume of the box, are very, very important. Most of the pre-made boxes you see around stores probably wont be the right size for your sub, or strong enough

Secondly, nearly every single type of sub is different, requiring different volumes of box.
Subs have different masses, different maximum excursions, different "suspension" stiffness.
Hence, each sub suits a certain size sealed and/or vented box. Sealed means sealed. vented means, ported...theres a specific size/shape hole in the box.
For a vented box, both the volume and the port construction affects the overall sound. they are *much* more complex than sealed, but offer higher volume output.

A $800 subwoofer in a box totally unsuited to it will get its shiny ass creamed by a $300 one in a built-for-the-sub, $200 custom box. I may be exaggerating slightly, but only slightly.

So. Lets say you have well installed front speakers.
Lets say you have well installed subwoofers.
Now you get to play around with crossovers.
See how low your front speakers can go, clearly.
See how far you can bring your sub up, before you can tell its behind you.

Eventually you can get into advanced tuning, like EQ’s, Time alignment, and other funky features…go. Learn. This is just a starting guide.

You will eventaully learn how placing the subwoofer box in different places in your boot can give you a free volume increase, or can cause cancellation. Theres another concept you should research, cancellation.


Other methods people use

Many people choose to mount small woofers/subwoofers directly in their doors. One per side. In such a case, you could easily make your subwoofer play higher than normal...it doesnt matter if you get directional frequencies from sub's in the front doors, does it? You want all the sound up front anyway!
BUT
A door mounted sub still probably wont play midbass as clearly as a smaller speaker dedicated to doing this, and there are differences between door mounted subwoofers, and door mounted midbass drivers. The speakers may be the same size, but again, different designs are for meant for different purposes.

Other people use 4” component speakers, with a 12” subwoofer.
4” wont play below 200hz easily, and sub’s playing of to 200hz will be a little muddy and, again, directional, so you have a big hole in the mid-bass between 100-200hz where things either don’t exist, or aren’t clear. Badd bass sq.

Some people have been known to run EVERY speaker in their car full range, and take out a competition with it. Its all about experimenting.

So, there you go. That’s a very basic beginners guide to what constitutes good sounding bass in your car, focusing on only one type of system (6.5” splits and a subwoofer).

If you decide to use a ported box, you should REALLY learn about subsonic filters.
I did a basic overview of their operation and usage, you can find it at
http://www.caraudioaustralia.com/forums/in...showtopic=63228

Research these if you want to learn more
Adjustable crossovers. Db/oct slopes.
Sound deadening and door sealing.
Cancellation.
Cabin loading (reflecting the sub off the back wall of your boot to get a boost in volume).

Props to FHRX studios, Pioneer australia, www.mmxpress.com for permission to use images hosted on their site.

Last but not least, this is a work in progress, so comment if you disagree on something or have suggestions (image resising, frequencies i've quoted, etc).

A little note:
Just as a bad front stage will make your bass sound muddy and crap, so will a bad sub-setup. A laggy, "muddy" or "boomy" sub setup will drag your whole bass SQ down, which is why we recommend getting a custom box built to suit the sub, to let it shine and play clearly and accurately.

can u verify what the 'sub sonic filter' is used for?

Sure thing
Answered in detail in

http://www.caraudioaustralia.com/forums/in...showtopic=63228

just a little thing to add onto this last post. subsonic filters normally have quite steep slopes such as 3rd or 4th order(18 or 24dB/Oct) this is so u can set it nice and close to ur tuning freq or 20hz(sealed) without loosing volume in the freqs near by, again this is proably better explained else where(x-overs, slopes, etc)