beginers guide to car audio...

[sidle]

Re: beginers guide to car audio...

The advantages of a sealed Subwoofer enclosure for the new Car Audio enthusiast:

A Sealed box will have a flatter frequency response, all things being equal. This makes it more versatile.
A Sealed box is smaller. A big ported sub box for a 12” sub may comfortably fill the boot volume of your car. I don’t know about you, but I like to have some boot space left.
A sealed box will point you in the direction of what you like. If those big wobbly lows get you going, you’ll know it’s time to investigate ported enclosures and a 12” sub with a high power amplifier. If you find you’re addicted to 180 Bpm Rave music, then you might start looking at a pair of sealed 10’s to give you volume, pace and control… But how will know know if the first box you bought was a cheap 12” active ported box that did nothing but rattle you panels and annoy your neighbours?
A Sealed enclosure tends to run well (sub-woofer choice depending) from lower power delivery of a bridged amplifier output. 100W and up will be enough to get a 12” sub with decent efficiency moving. It won’t be a ground pounder or an eyeball rattler, but it will be useful and quite possibly surprisingly powerful.



The disadvantages of a Ported Sub Woofer Enclosure for the newbie:

They may be tuned to a frequency unsuitable for your tastes.
They must be properly designed and constructed. A cheap or poor box will be a misery.
They range in size from “Bigger than a sealed box” to “Absolutely farking mahoosive”
They tend to require higher amplifier power output, which means a dedicated mono amp and increased system complexity.
We’re keeping it simple, right?



So, for 90% of applications, we’ve settled on either a 10” or 12” Sealed subwoofer.
"What should I buy?"

A Reputable brand, but to be honest you can’t go far wrong with most of what’s commercially available. A sub adds less colour to music than the speakers, and I would always move money in a tight budget away from a sub-woofer and towards the front end.
Voice Coil Configuration is paramount: Subs come in a variety of voice coil configurations. Some voice coil configurations may mean that a sub is incompatible with your amplifier! It’s important to know the specs of your amplifier, and in particular what loads, in Ohms, it is stable driving.
For most applications, a Sub with a single 4 ohm voice coil is almost universally compatible, especially when being driven by a bridged amplifier. However, you may not be getting the best from your amp if the amp can also drive a 2 ohm load.
Many amps are “2 Ohm Stable” (but not bridged! – this is rare!) and in this case, showing the amp a 2 ohm load will increase the power output. If your amp is 2 ohm stable, then you should be looking to show it a 2 ohm load. You can either buy a Single voice Coil 2 ohm Subwoofer, or else a Dual Voice Coil 4 ohm Subwoofer. You then connect these voice coils up in parallel, showing a 2 ohm load.
As we move up the power ladder, we come to amps and subs that are 1 ohm loadings. Here we usually see Sub woofers with dual 2ohm voice coils which can be wired to show either a 4 ohm load, or a 1 ohm load if wired in parallel.
Try not to be too tempted by the all in one box solution of a “1000 Watt!!! Active Subwoofer!” They do have their place, and if you really can’t be bothered to install separate subs and amps then fine, but they have several disadvantages: They’re not modular. You want to try a new sub? You’re back to square one. In the system we’re building, the amp, sub and enclosure can all be changed individually to tune your system to your needs.
They tend to lie about their numbers as well. 1000W will be peak power output on a good day with the wind behind it. A high quality amp giving a good 12” sub 200W will kick any and all of these active enclosures in the teeth all day long. They also require nearly as much work to install as a dedicated amp. You still have to feed them power and a signal to amplify, which means running cables from the battery and head unit to them. If you’re going to do that, you might as well go the whole hog and give the front speakers the benefit of amplification from a dedicated high quality amplifier.



Enclosure: It’s just a box, right?
Well sort of. But it needs to be a strong, airtight box and it needs to be the correct volume for the subwoofer. In a sealed subwoofer system the air in the box acts as a spring which supports the subwoofer cone. If you’re handy with a jig saw you can easily make your own enclosure, in fact it’s recommended because it’s so simple, and what costs £20 in materials will cost £100 to buy pre-made. Ensure the box is made of MDF or dense Ply and not Chipboard. Heavy thick fiberglass is acceptable for curved box designs or complex shapes, but weight for weight and where flat panels are involved MDF or Ply will be stronger. A strong box will be a heavy box, and there’s not much getting around this. If we’re talking about a Lotus Elise, you might want to omit the Sub-woofer and rely on getting your front end extending as low towards sub-bass as physically possible…

The final note on Subwoofers is really a car specific one. If you have a hatchback or an estate, then just plonk your sub box in your boot and you’re good to go. If you have a saloon, a coupe or a convertible, then you may need to give a bit more thought to positioning and installation of a subwoofer. You want to be sharing the same air enclosure with it. You feel sub bass as much as hear it, and it’s unfair to subject everyone to your bass just to get it from your boot to your ears, via the outside world. Give consideration in saloons and coupes to firing a sub forwards through the opening behind the rear seats if available, or else using the parcel shelf speaker holes as vents to allow the sub bass into the cabin. In coupes you may be able to use the rear ¾ panel as a subwoofer enclosure, locating the sub right in the cabin with you. Indeed, I did this with some success in my first ever proper install. In convertibles, you may struggle as they tend not to have a port behind the rear seats. You may have to locate a smaller subwoofer up front, in the foot well, under a seat, or even in the glovebox! See owners clubs for other enthusiasts solutions to the problems presented by specific cars.

[sidle]

Re: beginers guide to car audio...

Sub woofers:

I Want LOADS of BASS! I Want it LOUD! I want to set off car alarms! One Sub is loud, so two are louder, right?!
Or alternatively:
I listen to Radio 2 and Mozart… I don’t need a Sub, do I?

In Car audio, for a newcomer, a Single 10” or 12” subwoofer in a sealed enclosure, being driven by that wonderful 4 channel amplifier, is actually the right answer to both of these situations. I would probably recommend a 12” Sub to the first person, and a 10” Sub to the second, but the principles are the same and here’s why:
In a car, you’re fighting that battle against road noise, wind roar, engine noise and the sound of your partner moaning about the loud music. These are all low frequency drones. Your 6.5” speakers, as strong as they are at Bass and Mid Bass, simply can’t produce the sub bass efficiently enough to overcome this “noise floor”. Remember what I said about Bass and cone area: More cone area = more efficiency. This is doubly true with a Subwoofer. You simply need to move air to generate sub bass. Whilst 6.5’s can do it, they’d rather not. Giving those low frequencies (and we’re talking about bass below around 100Hz here) to a dedicated subwoofer not only means that they are reproduced as accurately as possible by a speaker designed for the job, it also frees your Woofers from the responsibility. This helps them in two important ways: Firstly the power that would be used to drive the cone into high excursion sub-bass notes can now be focused higher up in the frequency range – it gives your amp more head room. Secondly, it protects your speaker. Nothing kills a speaker faster than high volume signals at a frequency lower than it was designed to handle. If the voice coil can’t move any further, that energy simply becomes heat instead of movement. Eventually (or quite quickly for tweeters) the voice coil will overheat, melt it’s insulation off, and cook itself, and your speaker will be toast. Bad news.

So, we use a Crossover – probably the head units own crossover – to separate out those sub bass signals below a cut off point. This is known as a Low Pass Filter. Think of it as a limbo bar for music. Only those LOW enough will get through and make it to your 4 channel amplifiers bridged rear channels… and get amplified. This means we get the Sub-Bass we need, and spare our carefully selected 6.5” speakers the torture of trying to do something they’re not really designed to do, and improve their sound quality in the process.

“But I listen to Phil Collins and Beethoven – Why do I need a Sub”
A well chosen subwoofer is a compliment to ANY car audio system. Say “Sub” to the uninitiated and most people immediately picture the rattling clapped out escort in the town centre, Dragging it’s lowered arse, full of a big ported sub box and a sagging parcel shelf with 2 sets of 6X9’s in it, shaking itself slowly to pieces whilst annoying everyone not in the car. This is the perception of car audio. But in reality, all music has sub bass, and it’s an important part of the overall audio system to reproduce it. In the very best SQ cars you would be hard pressed to find the sub, and you may not even be aware in listening that it has one, but it will be there and it will be fulfilling a very important role. This is blatantly obvious in most Rap, Reggae and Dance music, but even in classical music there is substantial sub bass – indeed Timpany Drums and in particular a pipe organ produce some of the most impressive natural Sub-Bass you are ever likely to hear. If you’ve ever heard a pipe organ in full tilt in a church, you’ll know that amazing wobbly 20-30Hz Tone that you FEEL but don’t really hear. That’s a pipe about 100ft long resonating at its natural frequency, and it’s impressive. We can reproduce this in our car, any time we like, so long as we have a Subwoofer.

"Why Sealed and not ported? – I heard Ported Subs are louder"
This is true- to an extent. Ported Subs are louder around the frequency to which they are tuned. But therein lies the problem. By specialising and tuning the sub to particular frequencies, you boost its output (by a factor of Two or more!) in that range, but the rest of the Sub-range suffers. So you might have a box tuned to 30Hz which is absolutely outstanding with Dub Reggae, but completely fails to keep up with the fast paced Drum and Bass of a bit of Jungle or fast House music. Likewise, you might have a sub tuned to a higher point which is brilliant for Dance, but doesn’t drop low enough to do Hip-hop Justice.

[sidle]

Re: beginers guide to car audio...

Why 6 ½” (17cm) speakers?
The reproduction of bass tones relies on cone area. The bigger the cone area of a speaker, the more efficiently it can produce Bass. A more efficient speaker needs less power to go loud, and is less likely to distort when played loud. You will get more bang for buck out of a pair of 6 ½” speakers than you will 5 ¼” or 4” speakers. 4” speakers in particular will struggle to play low bass unless real thought and attention to detail has been paid to their locations and their installation. That said, if the car takes 5 ¼” speakers as standard and it would be a huge amount of work to install 6 ½ “ speakers, then a quality pair of 5 ¼” speakers installed with care may surprise you with their solid bass reproduction.

"Why component speakers?"
Speaker sets by and large come in two flavours: “Co-Axial” (shared centre line!) and “Component Systems” (lots of bits!”)
In fact, co-axial speakers are component systems. They have all the same bits. Any quality speaker system consists of:

A Tweeter, to play high frequency sounds. Generally this is around 3,000Hz (3Khz) and above.
A Mid-Bass Driver (Woofer), to play Middle and Bass notes, usually from around 100Hz up to 3KHz.
A Crossover or filter – To ensure that the tweeter and mid-bass drivers receive only the signals they are designed to accurately reproduce. In most co-axial systems this is simply a capacitor across the tweeter which acts as a filter to protect the tweeter from lower frequencies than it can safely handle.



Of course, a co-axial speaker is an attractive proposition. It contains a whole speaker system in a single package that you could fit and forget. Why is this not the best solution?

We perceive the bulk of information about positioning and locations of sounds from the upper range of our hearing. If your tweeter is low down, the music will sound low down. If it’s behind you, it’ll sound behind you. If it’s in front of you around ear height then it will sound natural – like the music is coming from a stage in front of you.
Once we have the high frequencies located, a small amount of attention to detail with other speaker placement allows us to play some tricks on our own ears. We can fool the brain into believing that the Bass from the speakers low down is also coming from up high. If we get it spot on, we can even fool it into believing that Sub-Bass, from a Sub-Woofer in the boot, is coming from in front of us…. We can build an Audio Image which gives the impression of a musical stage spread right across our bonnet, as if the windscreen isn’t there.
The crossovers on co-axial speakers tend not to be adjustable, and we cannot adjust phasing (The polarity of +ve and –ve connections) between the tweeter and the woofer. Quality component speaker systems come with separate adjustable crossover networks. They allow you to alter the level (volume) of the tweeter relative to the woofer and perhaps some other tricks too. Some even include a basic EQ system. They also allow you to reverse the connections which can help with imaging and tonality. When we refer to the crossovers supplied with a speaker system, we are talking about “Passive” crossovers. They receive no additional power, and they sit in the signal path after amplification.



So, I’ve convinced you that a 6 ½ “ speaker system is the way forwards.
Where should I put them in the car?
At least as important as the kind of speaker you fit is where you fit it. By and large cars have a speaker position down in the front of the door somewhere, or possibly in the “kick panel” in the footwell. Many cars now also have a separate tweeter location somewhere up near the A-Pillar or on the back of the wing mirror mounting. Here’s a diagram for reference:

Car Speaker Locations



The Tweeter should be mounted at somewhere between dashboard and Eye level. The left speaker should be as far left as possible, the right as far right for the widest possible sound stage. Popular positions include at the base of the A pillar (the pillar that forms the edge of your windscreen), the top of the dashboards at either side, or the “Sail panels” – the triangular panels that form the back of the Wing mirror mounting at the front of the doors.
The Woofer should be mounted either in the front of the front doors, or the kick panels (the outside of the footwells). Woofer positioning is dictated by the physical size of the drivers – they tend to have large magnets – and the fact that they need a large enclosure to work well. The biggest enclosure available to us is the Front door itself, often offering a cubic foot or more of semi-sealed volume to help our woofer reproduce bass. Woofers are also mounted low down in doors. Again, this is for a couple of reasons. Doors are full of stuff – Window winder mechanisms primarily, but also switches, locking mechanisms, and increasingly airbag systems and crash intrusion beams. The best chance of avoiding this stuff is low down at the front corner of the door. Secondly, I mentioned “path length difference” earlier which is the time difference introduced by the different distances sound has to travel to our ears from speakers located unequal distances away. Well, moving the speakers lower down decreases the relative difference between them, and this has benefits in sound quality.
The second viable option for the Woofer is the “Kick panel” – the outside of the footwell by the passengers feet. The primary advantage of this location is again related to path length difference. There is even less relative difference (in most cars) from this location. It also tends to offer an enclosure of sorts for the speaker, and prevents you having to route speaker cable into the car door if it doesn’t already have cable there. However, very few cars are able to accept 6.5” speakers In this location without either modifying the car or fabricating Kick panel enclosures for them. If your car is designed to accept 6.5” Speakers in the front doors, than this is what you should fit in almost all situations.
Now, given that only 30 years ago many cars were supplied without any speakers at all, and 20 years ago they just had them wherever they would fit, it’s actually a huge leap forwards that nowadays cars are supplied with speakers in pretty much the right place for stereo imaging. It only took them 20 years to catch up! If your car has 6 ½ “ Mid-Bass speakers in the doors and a tweeter positioned in the A-Pillar or the Sail panel, then by and large you should make use of these positions. Large speakers are designed to work in a large semi-sealed enclosure such as a door, and the high frequency sounds from the tweeters locate the sound stage high up across the windscreen.

Aiming Speakers
The other point to note is aiming. Aiming speakers, and particularly tweeters, has a large effect on the character of their sound and also the imaging capabilities of the system on the whole. A basic first step is to get a blob of blu-tac or Velcro and stick your tweeters to your proposed mount point. You can them play around with aiming before settling on your favourite position. On-axis means pointing at you, and off axis means pointing away! Imagine a laser pen pointing straight out from the middle of the tweeter, and aim that dot on the opposite head rest as a start point. Ultimately, it depends on your car, equipment and ears and there is no “correct” answer to this problem. There are many variables and many compromises and it is down to you to make the call based on what you hear.

Enough Already! I've got CASH and I'm ready to SPEND!

Look for reputable brands.
If you’re unsure, err towards Silk Dome Tweeters. They have a less harsh and more natural sound.
They should have a power handling in the region of 50 Watts- up to As much as you like but again beware “800 Watt” specials. 100W-150W power handling in the upper range is normal.
They should fit! Check mounting depth carefully. Speakers with deep baskets and large magnets may foul your windows when you try and roll them down, or they may not fit within the depth you have available. Check owners clubs for your specific car to see what others have been able to fit.
Buy New, or reputable second hand. Speakers DO die if they’re abused. Tweeters are particularly likely to have been killed if they’ve been fed a full range signal or abused in other ways.
Brands that have a good reputation and a good all-round sound quality include DLS, JL Audio, Polk Audio, Diamond, Infinity, CDT, Focal and Hertz. JBL and Alpine make perfectly good entry level speakers. I’m not going to name brands to avoid, but some cheaper speakers appear to have had more money spent on the way they look than the way they sound, and this is pretty obvious when looking at them.
And the golden rule of speakers: YOU MUST LISTEN to a number of set ups before deciding on what to get. Speakers have certain traits, but only your ears will tell you exactly what you prefer. To my ears, Focal speakers tend to sound sharp, verging on harsh, but others revel in the detail they offer. I prefer the laid back sounds of DLS and JL Audio products, other people might say they sound too dull and unexiciting. The speaker system above all else, more than the amplifier or the head unit, dictate the colour and texture of your music. It is very important you spend time getting to know what you like so that you buy the right product first time. If you really are unsure, you won’t go far wrong with JL-Audio, CDT, or Focal speakers. You can always play with your head units EQ to get them sounding right to your ears, but nothing will tame the shrill laser tweeters and low volume distortion of a pair of £20 Ebay Special speakers….

[sidle]

Re: beginers guide to car audio...

Speakers:

Why “Front speakers only?”
Why should I listen, then buy?
Why should I fit 6 ½" component speakers if I can?

The mantra on this site is “Fit and amplify front speakers, then see if you think you still need upgraded rears”. This flies in the face of conventional car audio wisdom. For years the thing to do if you wanted a loud car stereo was to buy a 2 channel amplifier and a cheap pair of 6X9 speakers and put them in the parcel shelf. Amplify them up, and hey presto, you’ve got a wall of music coming from the back of the car…. Why did people do this, and why shouldn’t you?

It’s cheap. Just a small amp, wiring kit and a pair of £50 speakers.

It’s quick. You could do this install in an afternoon on a mates drive.

It’s Lazy. You could fit better speakers up front, but that would involve removing door cards, routing cable into doors, messing around with positioning to get a good sound… Why bother?

Cars used to come with insufficient space or mounting points up front for larger speakers. This is no longer the case.
It makes poor use of the amplifier you’ve bothered to install. That amp would be so much better off powering the front speakers (and a sub too – it’s no more work installing the 4 channel than the 2 channel, remember?)

6x9’s, as a rule of thumb, are cheap and nasty. They use claims of high power handling (made up numbers!) and ever increasing “Four way!” “Five Way!” Designs to sell to people who aren’t really sure what they’re buying. You CAN get some very nice 6X9’s and they do have their place in certain applications. I’m fitting some as we speak to a US classic, because we don’t want to ruin the vehicle to fit a large subwoofer. But by and large, if it’s either or, you should spend your money on front speakers. Why?

Your ears face forwards on your head. This means that music should come from in front of you, not behind.

It is only possible to re-create a stereo recording accurately with a pair of stereo speakers in front of the listener.

Tweeters more than any other driver influence where it sounds like the music is coming from. If you have tweeters behind your head, you WILL hear them, and they will both muddy the sound stage and drag the sound towards the rear of the vehicle.

Even a huge install should have some nod to being musical. That’s why we’re all here – we love music. You can build a wall of subwoofers and 6X9’s behind your head and crank them up to eleven, but that’s not musical, it’s just loud.

[sidle]

Re: beginers guide to car audio...

Amplifiers:

In this section you will learn why a decent quality 4 channel amp producing a nice clean 50 Watts a channel or more is about the best purchase you can make right now.

An amplifier is a box. You feed it a signal, and it outputs a signal. They should be the simplest part of your audio system, but they often end up the most complex. They have (or lack) a range of settings which mean that they can make or break a sound system. They can also break your speakers or your ears if incorrectly set up. Here we will find out why a single 4 channel amplifier is the best purchase you can make in your car audio career.

"But my head unit makes 4X50Watts! It says so on the box! This Crappy Genesis Amplifier only makes 4X50Watts! Why am I even bothering?"

No, your head unit does not make 50 Watts a channel. Not even close. The MAXIMUM RMS output of any head unit on a 10amp fuse is about 10-12Watts a channel, tops. You need the additional grunt of a quality amplifier. Even if you only really want some heavy, heavy bass and so a single channel amp and sub would do, the high bass output will quickly overwhelm the front speakers, you’ll crank the head unit volume up to compensate, they’ll distort as the head unit internal amplifier reaches it’s (low) limits and you’ll end up cooking speakers and breaking your head unit. Do it properly from the outset, and you’ll have a clean sounding, powerful and upgradeable system that will keep you happy for years.

"I've been advised to look for a 4 channel amplifier. Why?"

A good four channel amplifier is a thing of wonder and beauty. It could be used to run, for example, four sets of speakers one in each corner of the car, but this is a real waste of its potential and we will find out why later. Any four channel amplifier worth its salt can also be a two Channel amplifier OR a Three channel amplifier. You can use it to drive a pair of speakers in the front of a car, and the other two channels can be “Bridged” together to provide double the power output into a single subwoofer channel. So you have a complete install running from a single amp. That means just 2 pairs of signal cables to it, only one power cable to arrange and only one amplifer to find a mounting place for and secure safely in the car.
If you buy correctly the first time, this 4 channel amp can stay with you for many installs to come, and here’s why:
I
've realised I'm a Bass head. The bridged rear channels don’t cut it anymore. You buy a 1Kw Mono amp and fill the boot with Subs. Now your 4 channel amp becomes the core of your front end. You bridge the 4 channels into 2 pairs, and give your front end double the power to keep up with the bass.

I'm a Sound Quality Fairy. I want more control over my set up.
You buy a mono amp for a high quality subwoofer. You now remove the passive crossovers from the system (more on this in the speakers section), and you run each individual speaker, that is each tweeter and woofer on its very own amp channel. You use the crossovers in either the amp or the head unit to send only the correct frequencies to that speaker, giving you more control over the sound, and more dynamic range as you are effectively giving your front end double the power to play with. Your 4 channel amp is now running 4 individual channels in an “Active” set up.

My wife complains about the bass and lack of boot space, and that the kids can’t hear their Barney The Dinosaur CD. She's made me throw out the Sub.
NOW is the time to amp up those rear speakers using the rear amp channels. Run a set of speakers in the doors or the rear shelf, and just accept that your life is pretty much over…..

Ok! I'm Convinced! What should I look for in an Amplifier?"

A reputable make. Brands to look out for include Genesis (no longer in business, but a strong second hand market exists), Infinity, Rockford Fosgate, Kenwood, DLS, Rainbow, Audison. JBL and Vibe make perfectly acceptable cheaper amplifiers.

4 Channels Ideally (DLS make 3 channel amps and these are acceptable but less flexible alternatives)

Output consistent with your needs. 4X50 watts is really a starting point, but beware “EBAY SPECIAL – POPULAR IN EUROPE! 800W output!!!!” No name amps. It is possible to build amplifiers very cheaply. They are not beautiful things. There are absolute bargains to be had in this forums classifieds section (Stick around and we’ll let you in eventually) Such as basic 4 channel amps for £30-£50 which will allow the newbie to set up a powerful system on a tight budget.
It should be Bridgeable.
It should have a low pass filter on one pair of channels allowing them to be bridged to run a sub.
Ideally it should have a crossover which is adjustable allowing you to use it “Actively” without purchasing more equipment.
It should have an external fuse, usually a blade fuse mounted on the face of the amp. This is to protect the amplifier itself and is NOT A SUBSTITUTE for the fuse on the power supply cable!

They will have a variety of switches and setting on them, the most important of which is “input level” or “Gain”… DO NOT SIMPLY TURN IT UP TO MAXIMUM… we’ll learn more about this later.
It is generally safe to buy amps second hand. They don’t “wear out” as such and can be easily repaired if they are old. If they work, then by and large, they work.



"I've read some stuff about amplifier Classes - which do I need?"

There are several classes of amplifiers available and they are differentiated by how they switch their power supply. For the most part, 90% of car audio amps available are Class "AB" and these suit the bulk of the newcomers needs.

Class A Amplifiers have a detailed warm sound but are very inefficient. They run hot and tend not to have massive power output.

Class AB amplifiers are more efficient and have high power output for their size with good sound quality.

Class D amplifiers are digital amplifiers with very high efficiency but traditionally poorer sound quality. Until recently they have been largely restricted to Subwoofer use. However, they are coming on leaps and bounds and their advantages in terms of small size and low heat output make them ideal for car audio. In the next five years I expect to see Head units with a true 4x50 Output from onboard Class D amplifiers.

With that said: If you need an amplifer and you're not fussed, go Class AB. If you want a tiny amplifier or alternatively you need BIG power, One of the forms of Class D amp should be on your shopping list.

[sidle]

Re: beginers guide to car audio...

Head Unit:
“What’s wrong with what’s in my car already?”

The problem with most factory installed head units is primarily that they have no way of getting a signal to the amplifier. There is a way around this, but it’s messy. Some (Cheaper) amplifiers have “High Level” inputs, which means that you connect the speaker outputs to the amplifier directly, and it then amplifies this. This is all well and good, but that signal has already been through the head units (very cheap) amplifier output stage. You will also lack a number of other adjustments. You may not have a Sub Woofer output and the ability to control the Sub Woofer level independently of the rest of the system. You probably won’t have anything other than a basic EQ settings. You might not be able to control your Ipod or play music from a USB stick or even hard drive. All of these things can be provided by choosing the correct aftermarket Head Unit.

One caveat I will address is that more and more frequently, cars at all price points are now equipped with integrated Stereo/Navigation/Information display systems. Some of these can be really, really complex and fiendishly difficult to get around. It may simply not be possible in your New Audi, BMW, or Mercedes, or even Peugeot for that matter, to pull out an old stereo and put in a new shiny one. If this is the case, you are really limited to buying a product such as the expensive and extremely clever JL Audio Cleansweep, Audison Bit One or JBL MS8 Processors. These take the speaker or signal level inputs from the cars own audio system, and allow you to split it, process it, and output it for amplification pretty much however you want. At a minimum of £400 you’re looking at a significant investment, and you may want to seek professional installers to do this work. I would refer you to Model specific owners clubs if you’re in this situation, to see what others have done to improve their car audio.

So, that out of the way, you’ve decided you want a DIN slot sized Car Stereo. What should you look for?

Head Unit shopping list Summary:
2 or 3 pairs of RCA sockets on the back.
High level Pre Outs – 2V to 8V
Compatible with your music sources.
A reputable Brand
Some Audio Adjustment – Equalisers, Crossovers, Sub level control.
Any advanced features are a bonus, such as Time Alignment or a configurable crossover network.
New or Second Hand according to budget.



"Why Do I need RCA Outputs? What Are they?"

RCA’s are a co-axial cable that send the signals to your amplifier. Some head units have just one pair often called “Rears”. Some have 2 Pairs “Rear and Sub” and some have three pairs – “Front, Rear and Sub” and this arrangement the most flexible and useful. If you have a head unit already but it only has one RCA output, and can’t afford/don’t want another then there are ways around this. They aren’t pretty, but all is not lost. You can use a simple splitter to split the signal, but you will not be able to adjust the balance from front to back or of the sub from the head unit. You can also use an amplifier with an RCA “Pass through” (it simply outputs an unaltered signal for you to another RCA on the amp itself) and this can be very useful for sub set ups, although again you will not be able to adjust the sub level from the head unit. A head unit that will be future proof needs a minimum of 2 pairs of RCA outputs, which are simply round plug points on the back of the unit allowing you to connect RCA cables. Three Pairs is better and offers more flexibility. Each pair carries a stereo siginal to the amplifier. In most ausio systems 3 pairs making six channels is the most you will encounter.

"What inputs do I need?"

The head unit should be capable of playing music how you want it to: A USB stick with 32Gb of tunes on it, your trusty ipod, Via Bluetooth from your mobile phone…. Even CD’s! Make sure you are confident your head unit connects to these sources and works the way you expect it to. You may need additional boxes for ipod and USB functionality, and you might need a compatible cd-changer if you want multiple discs in the car. We live in a digital age, and most head units for the last 10 years have had some kind of MP3 functionality, some better executed than others. A front “Aux” input via 3.5mm jack plug may be a bonus. Hook your ipod up via the correct cable, and it should work… until the battery dies anyway. iPod compatible head units will connect via the ipod plug and should also charge the ipod to keep it alive as long as it’s in the car.
Some form of adjustable Equaliser Settings (EQ). This allows you to shape the music to your tastes, to tame a sharp top end or add a little bit of bass. Cheaper head units might have a few Pre Sets “Party! Pop! ROCK!” and adjustable treble and bass settings…. You can make do with these but they won’t give you the control you might want. It may be worth upgrading or considering an external EQ in this circumstance.
Popular and reputable makes include Pioneer, Alpine, and Kenwood. Sony, JVC and Panasonic also make perfectly acceptable head units but they are not as renowned for their sound quality. Some cheaper head units offer serious value for money, but if your budget is under £100 consider what you can get second hand for the price of a cheaper new head unit. Ebay or the classifieds here are always full of head units for sale, and your £80 budget might buy you a head unit one or two tiers above what you could afford new.

"What features is it nice to have?"

Processing or equalisers(EQ) of some kind . A fully adjustable EQ can be the difference between a dull, flat sounding system and one that sounds fantastic. Look for “20 band” or “parametric” EQ’s. The latter allow you to select frequencies to boost or cut, the former offers enough flexibility to tune the sound sufficiently. More expensive head units might allow you to adjust left and right EQ setting independently or even each individual speakers channel on it’s own. Most head units have five or more pre-set EQ settings (PARTY! ROCK! HISSY!) And these are best avoided as they are inflexible.

Crossovers. The most basic form of crossover you are likely to encounter in a head unit is a “Low Pass Filter”. This acts on the Subwoofer channel and passes only low frequency sounds, below the crossover point which you set, to the Subwoofer channel for amplification. Commonly this will be adjustable to one of these frequencies: 50Hz, 80Hz, 100Hz, 125Hz or a little higher. This is useful to have, but not essential as most amplifiers can also perform this function. Some headunits again come with fully customisable crossovers which can be active on any channel, to divide frequencies before amplification. This isn’t the place for a detailed discussion on crossovers, and as you will see there are no fewer than 3 opportunities for crossovers to come into play in even a simple systems. Suffice to say that a head unit that has a versatile set of crossovers or even a full crossover network can be a godsend as your system grows and improves.

Time Alignment (TA): Time alignment is a digital process whereby an audio signal is processed, and part of that signal or one channel of it is delayed slightly prior to amplification. In car audio it is important because you do not sit an equal distance from all of the speakers. Here in the UK we are often half as far away from the right channel as the left channel, and the subwoofer is probably even further away, in the boot. The time sound takes to travel in air means that if all the speakers play the same sound at the same time, it actually reaches you at a fractionally different time because it has travelled unequal distances. This can be compensated for by time alignment. This is a complicated and detailed process of tweaking and setting up. It may be that you never need it. Well installed systems avoid problems caused by “Path Length Difference” by positioning the speakers carefully. Suffice to say, if your head unit has time alignment it is probably in the top tier of head units, and it may just save you having to upgrade or buy an expensive external digital processor to get that last 5% out of the system.