Car Audio: Speakers, Amps and Subwoofer Guide

Coaxial or component

Coaxial speakers mount the tweeter on the same axis as the mid-bass driver, so the whole thing drops into the factory hole with no extra work. For most drivers this is the sensible upgrade — the improvement over worn paper factory cones is immediate.

Component sets separate the tweeter, giving you the option to mount it higher in the door or the A-pillar, closer to ear level. The soundstage lifts off the floor and vocals sit on the dashboard rather than by your knees. It costs more in parts and considerably more in fitting time.

Sensitivity matters more than power on a factory head unit

A standard factory head unit puts out modest continuous power per channel, whatever the sticker claims. A speaker with high sensitivity converts more of that limited power into volume, so it is the specification to chase if you are not adding an amplifier.

If you are fitting an external amplifier, sensitivity matters less and power handling matters more. Match RMS to RMS and leave headroom, because a clipping underpowered amplifier destroys more tweeters than an overpowered clean one ever has.

Sound deadening: the unglamorous upgrade

A car door is a thin steel panel with holes in it — effectively a very poor speaker cabinet. Adding constrained-layer damping to the outer skin and sealing the inner skin turns that door into something closer to a sealed enclosure, and the mid-bass improvement is often larger than the speaker swap itself.

Start with the front doors, since that is where most of the music comes from. The boot floor and wheel arches are the next priority if you are fitting a subwoofer.

Adding a subwoofer without electrical trouble

An under-seat active sub is the tidy solution for most cars: one box, built-in amplifier, minimal boot space lost. A boot-mounted enclosure with a separate amplifier goes far deeper and louder, at the cost of luggage space.

Any amplifier over a few hundred watts needs a properly fused power cable run from the battery, an adequate earth point on bare metal, and ideally an upgraded alternator cable on older vehicles. Dimming headlights on bass hits are a sign the electrical side is under-specified, not a badge of honour.

Car audio upgrade paths

Buying checklist

• Look up your vehicle's factory speaker sizes and mounting depth first
• Prioritise sensitivity if you are keeping the standard head unit
• Deaden the front doors before spending more on drivers
• Fuse any battery power cable within 30cm of the battery terminal
• Match amplifier RMS to speaker RMS and avoid running an amp into clipping

Frequently asked questions

Coaxial or component car speakers?

Coaxials are the straightforward drop-in upgrade and suit most drivers. Components separate the tweeter so it can be mounted at ear level, which lifts the soundstage — worth it if you are prepared for the extra fitting work.

Will new speakers work with my factory stereo?

Yes, provided you choose a high-sensitivity speaker. Factory head units deliver limited continuous power, so sensitivity is what converts that into volume.

Do I need an amplifier for car speakers?

Not for a basic upgrade. An amplifier becomes worthwhile once you fit component sets or a subwoofer, or if you regularly listen loudly and hear the factory unit straining.

What size subwoofer fits in a car?

An 8 or 10-inch driver suits most boots and under-seat spaces. A 12-inch goes deeper but needs a larger enclosure, so measure the boot before ordering.

Does sound deadening really make a difference?

Yes, and it is frequently the best value change in a car. Damping the door skin stops panel resonance and gives the speaker something closer to a sealed enclosure to work against.

Why do my headlights dim when the bass hits?

The amplifier is drawing more current than the electrical system comfortably supplies. Check the earth point, upgrade the power cabling, and on older cars consider the charging system before adding more power.