Planning Your First Sound System

Planning your first sound system is mostly arithmetic: decide the bands, count drivers and amp channels, check what the dB maths gives you, and leave money for processing and protection. Done in that order, the rig grows by adding matched boxes instead of replacing them.

Define the job

Fix three things first: the music, the room or site, and the vehicle. Roots, dub and DnB put heavy demands on the bottom octave, roughly 30 to 60 Hz, where excursion requirements are highest. A function room and a field need different headroom. And a box that won't go through the van door stays at home.

Bands

A three-way layout is the usual start and extends cleanly to four-way:

• Sub: 18" drivers in scoops, reflex boxes or horns, up to roughly 80 to 100 Hz.
• Kick / mid: 12" or 15" drivers, to around 1 kHz. See mid-bass drivers.
• Highs: compression driver on a horn.

Crossover points vary with the boxes; set them from measurements, not habit. Pick one sub design and one driver so every sub sums the same way. See scoop vs reflex vs horn and crossover basics.

What more subs buy you

At low frequencies, closely grouped subs sum coherently. Each doubling of identical subs, each with its own share of amplifier power, adds about 6 dB: 3 dB from the extra power and 3 dB from mutual coupling. Doubling displacement adds the same 6 dB to the excursion-limited ceiling. Four subs therefore give about 12 dB over one, which is why value per box matters: more boxes beats fewer, more expensive ones when the budget is fixed. See how many subs.

Example: four WM1850/8 subs

The thermal ceiling is a calculation from the sensitivity rating, not a measurement, and in the bottom octave the 12 mm Xmax will usually limit first. Model your box to see where. For horn-loaded subs or long, hard sets, look at the WM18X451: 1800 W RMS on a 4.5" copper coil, built for scoops and folded horns, at £345.

Amps, processing and cable

A driver on a clipping amp with no limiter is the common way first rigs lose drivers. Budget for:

• Amplifiers sized to each driver's continuous rating. See amp matching and amp channels for a stack.
• Crossover / DSP with high-pass and limiting on every band. The XR204 is a 4-way stereo active crossover (2 × XLR in, 8 × XLR out, >106 dB dynamic range, <0.004% THD+N): enough outputs for a three-way rig now and four-way later. See budget DSP.
• Cable, connectors, ply, handles, grilles, paint. Price them at the start.

Model before you cut

WinISD (reflex) and Hornresp (horns and scoops) take a driver's T/S parameters and predict response and excursion at your planned power. See our speaker tools and Thiele/Small parameters.

Build it to travel

• 18 mm birch ply is strong and holds screws well, but it is heavy: fit proper handles.
• Size every box for two people and the van you actually have. A WM1850/8 alone is 20 kg before any wood.
• Wheel boards and stackable shapes save backs and set-up time. See moving a sound system.

Sources: Wavemark WM1850/8 spec sheet, WM18X451 and XR204 product data. dB relationships are standard acoustics; calculated values rounded. Check each driver's data sheet and your amplifier's specification before connecting anything.