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Okay, so here’s the scenario: you’ve finally decided to take the plunge, and add some meaty bass to your anorexic-sounding stock audio system. In other words, you want the homies to hear you before they see you; you wanna bang! So you head over to your favourite car audio supplier; the plan is for a subwoofer (or two), and a suitable amplifier to power your new setup.

Problem is, as soon as you walk through the door you’re bombarded with a huge range of brands and products; and to further compound matters, you’ve got an over-enthusiastic sales assistant breathing down your neck, pushing you to choose products you might not necessarily be interested in (or not have the budget for). Relax, your situation isn’t unique – it happens nearly everywhere on a daily basis; which is why I figured it’d be pretty useful for you guys to have a clear idea on the steps needed in order to properly pair a subwoofer and amplifier system.

Follow these few simple guidelines, and I guarantee you that you’ll get the best audio performance within your allocated budget! Before we get started, I cannot emphasise this enough: Bigger isn’t always necessarily better! Have some faith here – I can show you a properly planned and constructed system, comprising of a single 12” subwoofer and a small monoblock amplifier; that has the ability to destroy systems made up of two 15” subs and an amplifier. Genuine!

The trick to it all is so simple: Just ensure all your equipment is properly matched and set up. Before I move to the topic at hand, I want to start off by saying that we’re going to work off the assumption that all subwoofer enclosures referred to have been properly designed & constructed; and that the installer is using the correct gauge and grade of copper cable.

Getting started: Amplifier current draw on stock electrical systems.

First and foremost; you need to establish what you’re working with in terms of your car’s electrical system. Find a battery centre in your area that can Load Test your vehicle’s battery to ensure that it’s in good health. This is usually a free service, and should cost you nothing but your time. It doesn’t matter if you’re only planning on one amplifier or ten; if your car happens to be older than 1 year, this will become an essential step. Once they’ve established how strong your battery is and have given you the green light, step 2 is to begin your amplifier search.

Before we even get into that though; I’m sure you’re curious as to why a battery test is so crucial? Well in short: so you don’t murder it with huge, power-hungry amplifiers whose demand is greater than the electrical system’s ability to supply. Most cars typically come equipped with a battery rated between 40Ah and a 60Ah; which means that you can safely get away with using a small monoblock amplifier (along with a four-channel to feed the vocals) using the stock battery.

Note: ‘Ah‘ is Amp Hours – it describes how much current can be delivered at a constant rate, as the battery is depleted over the course of an hour.


If you happen to have anything less than a 40Ah battery, I’d recommend no more than a four-channel amplifier. Don’t feel despondent or let this deter you, especially if you’re an up and coming “bass head” – it’s still possible to build a system that can be heard from down the road, with just a four-channel amp powering your bass system. Yes, I am speaking from experience; and yes, I’ve personally done this before. Adding an extra battery will make a massive difference; but I’ve already covered that in another article.

If you’re in the fortunate position of having anything above 60Ah; feel free to add a small monoblock amplifier to accompany your four-channel amplifier; but please hear me out on this one: don’t even think of adding anything over 1000W RMS, especially if you want your system to be efficient and reliable. Don’t let sales assistants coerce you into buying an amplifier bigger than your electrical system’s capabilities.

Will a capacitor help if I am using a stock battery?

I’ve witnessed so many “pro” installers and retailers shamelessly con customers into buying capacitors (aka power caps) under the pretence that it will help with the battery’s reserve current. Surprise: If anybody has told you this, trust me, they’re talking utter rubbish. Capacitors DO have a place and purpose yes; but “helping with your reserve current” simply isn’t it. If you’re using a capacitor but your electrical system isn’t up to scratch, you’re doing more harm than good.

Subwoofer shopping.

While subwoofer enclosures are extremely important, I’m not going to dive too much into it as I’ve covered this in the past. What we will discuss though, is the “beginner’s guide” on how to mate woofers with the correct amplifier. The most “common method” used when choosing a sub is to look at the RMS rating of the sub; then trying to match it to an amplifier’s RMS output.


All good and well in theory; BUT: the problem I have with this is that there are so many subwoofers on the market that have really high, fantastic ratings on the sticker; but out here in the real world, those woofers probably won’t be able to handle half of its rated power for more than 3 minutes straight at full tilt.  Remember, you wanna be smokin’ tyres, not subs!


So as a beginner, how do you know what’s the correct speaker to use?

A good start would be to look at the woofer’s voice coil size. The larger it is, the more power it’s able to handle… BUT it’s not quite as simple as that. Many have made the unfortunate mistake of assuming that using a low power amp on a high-powered woofer will ensure the woofer won’t break, and should perform better… right? See, here’s the thing about that though:

In my experience of building small pounders I’ve discovered quite the opposite; so as a rule of thumb, I’ll always suggest that when you’re using a low power amplifier (around 300W RMS’ish), always try to match it up with a subwoofer that has a voice coil no larger than 5cm (2-inch). Generally speaking, these woofers have high sensitivity, so won’t need much power to get really loud. Now; if you were to feed this same amplified power into a woofer with a 7.5-10cm (3- or 4-inch) coil – which ideally needs a few thousand Watts RMS’ worth of power to really get it pumping – the simple fact of the matter is this: the higher-powered sub would not be as loud as the sub with the smaller coil.

If your amp is rated between 300-700W RMS, you can start looking at subwoofers that have voice coils up to 6.3cm (2.5-inch) in diameter; but please, no larger than that. Truth be told, it’s possible to use subs with 7.5cm (3-inch) coils within this amplified power range; but don’t expect them to sound as good, feeding off that low power.

Once you start playing in the 1000+W RMS amplifier range, you can extend your search to include subwoofers featuring voice coils larger than 3”; but ensure your electrical system is able to handle the load you’re about to place on it.

There’s naturally a lot more to everything we’ve just discussed; however, I’ve tried to keep it as basic and simple for newbies to understand and follow. Purchasing the right products is only one half of the equation; you’ll also need to ensure that they are properly installed using best industry practices, in order to get the best possible audio performance. Literally bang for your buck!

By properly planning out your system by using the above-mentioned guide, coupled with following proper installation principles; you can build a small, inexpensive system that can be heard from a few blocks away. Remember, efficiency is key; ‘more’ isn’t always more. You don’t always need massive equipment to be loud.



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