A Complete guide for buying Car Audio – Part II

This guide for buying Car Audio (and it is only a guide) is intended to answer some of the standard questions we all tend to asked. More often than not the question starts as

“Hi! I’m new and I’d like to put a stereo in my car!”
“What should i look for?”
“How to wire them up?”

So by now you’ve got the basics. You’ve got a head unit, a 4 channel amplifier. You’ve got a set of nice 6 ½” front speakers or 5 ¼ ‘s at a push, and you’ve got a big wedgy MDF box with a 12” sub installed in it. So the question now would be how do we fit this stuff to best effect? Well for starters,


Route all the cables


It looks simple, but finding and running cables along the car tends to be the biggest pain.
Conventional wisdom dictates that you run power cable up one side of the car, RCA and signal cable up the middle (as that’s where the head unit is) and Speaker cable down the opposite side of the car from the power cable. In reality, it can be a tricky task to perform.

So to begin with, It is worthwhile knowing where ECU’s and other complex electronic items in your car are (ie. airbag ECU’s, Fuse boxes etc) and routing all the audio cables well away from these.
They tend to kick out high frequency interference, and coils in crossovers may well pick that up inroducing noise to the audio system. Only by examining your car will you work out the best route for your cables. So long as you can maintain a separation of 5cm or so between the signal, speaker and power cables you will not pick up noise from one to the other.

Now I’m going to break down each of the key components in the System and explain to you how they all work out.


Head Unit

The 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 – Equalizers, Crossovers, Sub level control.
  • Any advanced features are a bonus, such as Time Alignment or a configurable crossover network.


Wiring up a Head Unit is more or less a simple job if you have managed to obtain a wiring adapter for your car’s wiring harness. On the contrary, mounting it on the dashboard will probably require you to get a professional on the job especially if the car you own has an integrated head unit. The whole procedure would need to take your car’s dashboard apart and remove the stock radio, install a wiring harness to connect the new receiver’s standard harness to your car, a mounting kit to hold everything into your dashboard, connecting the RCA cables and finally stitching it all back up.

Modern cars are more and more often being supplied with integrated sat-nav and vehicle information screens. These can pose a serious problem to the (“Do It Yourself” ) audio enthusiast, simply in obtaining a clean signal to amplify. It may be that retaining the OEM “head unit” and adding a processor may be the expensive and only option in some cases.
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.


Wiring your Amplifier

A Good locations to mount the amp would be under the seat or in the boot of your car, Which one of the two will largely depend on the size of your amplifier.
Always remember if you amplifier is in a tight space, install a fan for ventilation (A computer fans would do just fine).



After you figure out where you want to install your amplifier. Go ahead and put it in this location, test the feel and fit. Install it so that when your get your wires to it, it will be ready.

You can now run the RCA cables and remote turn-on lead (typically a blue lead but you will need to check your head unit’s manual) from the back of your head unit to your amplifier’s mounting location and the speaker cable from the amplifier to the where you want to install the speakers ( to get the amplified signals from the amp to the speakers obviosuly).

Remember to avoid running the power wires and signal cables on the same side of the vehicle as this could induce noise into your system.


To power your amplifier, the power wire from the amp wiring kit needs to run from the battery, through your car’s firewall, through the car’s body and on to the amp.

This power cable MUST be fused. Not should, not “it would be nice”. This cable plainly and simply MUST be fused as close to the battery as physically possible. This is not to protect the amp, it can take care of itself, but to protect your car from turning into a fire ball.

Why Do I Need To Fuse up the Wires?


Let’s say for example that a sharp metal edge in the engine bay cuts your insulation on your power cable and then contacts the conductor within. Here are the two scenarios:


Your battery is short circuited and begins to supply as much current as it can down your poor cable. The heat at the point of the short circuit is so great that it actually welds the cable to the bulkhead, making the connection firm… the battery instantaneously supplies 600 Amps down the cable, things get red hot, the cable insulation starts to melt… The fuse will instantly burn out, breaking the short circuit. Oh, and your amp stops working until you’ve repaired the cable and replaced the fuse.

The first part is the same, the battery begins to supply 600 Amps into the short circuit. The cables insulation does begin to melt though, and in fact gets so hot it sets itself on fire, catching with plastics and fuel in the engine bay. There is no fuse to blow, so the fire takes hold. Your engine is toast by now, and if you’re driving you’ve got about 10 seconds to pull over and get out before the cabin is filled with acrid smoke. You get to watch your car burn to the ground.
Oh, and your insurance probably won’t pay out after their investigators find out that the fire was wholly due to your negligence in fitting a 4awg cable directly to your positive battery terminal without a fuse.

So for power supply, you need a thick cable, and a fuse holder and fuse, and you need some ring terminals to make a good solid connection to the amplifier and battery.


The Ground should be equal in gauge to the supply, and should be grounded as close as possible to the amplifier. You should ground to bare metal and secure it.
A huge number of problems with noise in audio systems or amplifiers being unreliable or not working, are due to inadequate grounding of the amplifier.

An Important point to consider:
Your amplifier 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.



Speaker Installation:

It’s usually not a difficult work, but it’s just more work. For instance, to install the speakers on the door, you’ll need to get the door panels removed to gain access to the factory speakers and run cables from the amplifier into the doors, which often proves be the most challenging part.


Some speakers will fit right into the factory speaker openings and use the factory grilles and brackets. Other sizes fit with the help of a mounting bracket (might be free with your speaker purchase), or with minor modifications, such as drilling new screw holes, cutting a small area of metal or pressboard, or filing cardboard or plastic to make room for a speaker that is larger than the factory opening.

Here’s a diagram for reference for speaker location

The Tweeter should be mounted at somewhere between dashboard and Eye level. 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 the triangular panels or “Sail panels” that form the back of the Wing mirror mounting at the front of the doors.

The Mid Bass 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 square foot or more of semi-sealed volume to help our woofer reproduce bass.

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.
Make sure you match the polarity of the car and speaker’s connections. Usually, the speaker’s positive terminal is the larger of the two and is marked with a “+” or a small dot.





Installing a subwoofer is certainly the easiest job of the lot. A subwoofer or multiple subs installed in an enclosure would just need to be placed on a nice spot in the boot. If you have a hatchback or a crossover or even an SUV, 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 largely because you want to be sharing the same air enclosure with it.

To solve this problem, consider firing a sub forwards through the opening behind the rear seats ( in coupes ) if available, otherwise create the holes on the parcel self or use the parcel shelf speaker holes if available as vents to allow the sub bass to enter into the cabin.


” How do I wire up my subwoofers to my amplifier?”

This can be a tricky step because there are so many options and variables to consider when making the purchase and wiring up your sound system. Subwoofers have different impedance (Dual 4 ohm, Single 2 ohm, etc) that change your wiring options when you add or subtract woofers. Amplifiers also have limitations on your final impedance, so the subwoofers and amplifier must have the same final impedance to be connected.

Lets take for example, an subwoofer with its ratings:
-400w RMS
-1200w Peak
-4 Ohm Impedance

So a good amplifier for this sub (assuming its the only one attached to the amp) would be of atleast 2 channels and has the following ratings:
– 300 – 400w RMS (bridged mode)
– 4 Ohm Impedance

Another example would be If the subwoofer has a dual coil with its rating
– 4 ohm impedance per coil
– 400w RMS

then it can be paired with an amplifier with ratings:
– 400w RMS @ 2 ohm ( when the coils are connected in parallel )


So to summaries,

Your 2/4 channel amplifier should have a bridge mode and low pass filter on the pair or atleast on one pair of channels to allow 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!

If your plan is to add power to all 4 speakers, then you can put a 5 channel amplifier ( 5th channel for your sub) or a couple of amplifiers (4 channel amp for the speakers, plus one mono block for subwoofer).
The questions now is,


This is not easy to explain but the Mantra is to choose a speaker and amp that put out the most power, without blowing each other out.
What you want is the RMS (not the maximun power) of both the subwoofer speaker and the amplifier to be as close as possible. The RMS is also the amount of power the amplifier can continuously put out without over heating.

When looking at speakers and amplifiers, do not look at the peak power. A speaker or amp can only be run on the peak power for about a minute before it goes bad or overheats. You want to be running your subwoofers on its RMS rating rather than the peak rating.


Sound deadening :

A pack of a self adhesive sound deadening product will be quick and easy to cut, shape and install in doors, floor pans and other large resonant panels.
The bare minimum is to deaden the outer skins of your doors. essential if you’re putting 6 ½”s in there.


If you have the choice of ₹15,000 speakers or ₹10,000 speakers and ₹5,000 on sound deadening, then get the deadening and the cheaper speakers. You’ll win out every time.

So the amount of damping will obviously depend on your pocket. If budget is not a problem then you can get the whole floor pan, trunk and bonnet along with all the doors deadened.


The result surely would be that your car would be alot more quieter than before and with that you will notice alot more detail in your music and tight bass coming out from your speakers ( which iam sure you were looking for at the first place! ).
And yes not to forget, it will prevent all those annoying panel vibrations that spoils the experience of listening to quality music.



I have written this guide for buying Car Audio because I wish someone else had written it and given it to me all those years ago. I would have saved me some costly mistakes and some stupid errors. This information is if you like, the combined and generalized advice that many people have offered over the time.

So I thought I’d put it all in one place, as a port of call for newcomers to crystallize their ideas, review their expectations and get bang for buck they spend on car audio equipment.

This is not a “my way or the highway” post. We all experiment, it’s what we do, and should do to keep improving. But you must walk before you run and this guide for buying Car Audio is intended to get the newcomer off all fours and toddling along FAST.

               Click here for “A Complete Car Audio buying guide – Part I “
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