Specify a PA from the audience outwards. Size loudspeakers to the room, then choose an amplifier rated about 1.5 to 2 times the speaker's continuous power at the actual load impedance. Cabinets in this range publish 110 to 135 dB maximum SPL.
Work in the right order
The single most common way to end up with an expensive system that does not work is to start from a wattage figure. The order that works is: audience and room, then loudspeakers, then amplification, then processing, then inputs.
Loudspeakers: size to the room, not the budget
Point-source cabinets cover small and medium rooms efficiently and go up on a stick in minutes. Line arrays earn their rigging in larger rooms and open-air spaces, where controlled vertical coverage keeps the level similar at the front and the back. Below a few hundred people an array is usually more work than the job needs.
Two specifications do most of the filtering: maximum SPL tells you how much level the cabinet can produce, and the low end of the frequency response tells you whether you need subwoofers.
| Model | Type | Frequency response | Max SPL | Impedance | Price |
|---|---|---|---|---|---|
| CA-06 | Conference Audio | 90Hz-20kHz | 120 dB | 8 ohms | $107.99 |
| MH-8 | Active Speaker | 70Hz-18kHz (±3dB) | 110 dB | 8Ω | $114.99 |
| MH-10 | Active Speaker | 70Hz-18kHz (±3dB) | 110 dB | 8Ω | $149.99 |
| CA-10 | Conference Audio | 60Hz-20kHz | 122 dB | 8 ohms | $158.99 |
| MS-12 | Active Speaker | 60Hz-19kHz (±3dB) | 112 dB | 8Ω | $235.99 |
| FT-12 | Stage Monitor | 60Hz-19kHz (±3dB) | 120 dB | 8Ω | $294.99 |
| MS-15 | Active Speaker | 55Hz-19kHz (±3dB) | 113 dB | 8Ω | $354.99 |
| MS-18 | Stage Monitor | 35Hz-220Hz (±3dB) | 128 dB | 8Ω | $433.99 |
| MS-215 | Active Speaker | 50Hz-19kHz (±3dB) | 119 dB | 4Ω | $473.99 |
| VS1500 | Active Speaker | 65Hz-18kHz (±3dB) | 112 dB | 8Ω | $512.99 |
| LA-8 | Line Array Speaker | 65Hz-19kHz | — | HF: 8Ω, LF: 16Ohm | $708.99 |
| VS2500 | Active Speaker | 60Hz-18kHz (±3dB) | 115 dB | 4Ω | $708.99 |
| LA-8 | Line Array Speaker | 45Hz-200Hz | 120 dB | 8Ω | $748.99 |
| HW-1801 | Active Speaker | 35Hz-20kHz (±3dB) | 132 dB | 8Ω | $748.99 |
| LA-10 | Line Array Speaker | 50Hz-19kHz | — | HF: 8Ω, LF: 16Ohm | $787.99 |
| LA-10 | Line Array Speaker | 45Hz-200Hz | 123 dB | 8Ω | $787.99 |
| MS-218 | Stage Monitor | 35Hz-220Hz (±3dB) | 132 dB | 4Ω | $787.99 |
| LA-12 | Line Array Speaker | 70Hz-19kHz | 130 dB | HF: 8Ω, LF: 16Ohm | $906.99 |
Across the cabinets in this range that publish a figure, maximum SPL runs from 110 dB to 135 dB with a median of 120 dB, and the low end of the published frequency response runs from 20 Hz to 90 Hz with a median of 60 Hz. That median tells its own story: half the cabinets here stop around 60 Hz, which is fine for speech and thin for music.
Amplifiers: match the speaker, then check the load
A widely used guideline is an amplifier rated about 1.5 to 2 times the loudspeaker's continuous (RMS) power rating, with limiting set to protect the drivers. The headroom exists for transients, not to run the system louder.
Underpowering damages more loudspeakers than overpowering does. An amplifier pushed into clipping produces a distorted waveform rich in harmonics, and that energy lands in the high-frequency driver, which is not built for it.
Worked example
A cabinet rated 400 W continuous at 8 ohms:
- Target amplifier power: 400 x 1.5 to 400 x 2 = 600 to 800 W per channel at 8 ohms
- Two of those cabinets in parallel on one channel present 4 ohms
- At 4 ohms you need the amplifier's 4-ohm rating to reach 1200 to 1600 W, because it is now driving 800 W of continuous rating
That second step is where improvised systems fail. Amplifier power is quoted per channel at a stated load, and the 8-ohm figure is not the 4-ohm figure.
Subwoofers
There is no universal ratio. What decides it is programme material: speech-led events need very little low-frequency extension, while music-led events typically run substantially more subwoofer capacity relative to the tops. If your cabinets stop at 60 Hz and you are reinforcing kick drum and bass guitar, subwoofers are not an upgrade, they are the missing part of the system.
Processing
Crossover decides what each driver receives. Delay aligns cabinets that sit at different distances from the audience. Equalisation corrects the room. A modest, properly tuned system beats a larger untuned one in almost every room, and processing costs far less than the extra boxes it saves you buying.
Monitors and inputs
Monitor wedges sit in the worst position in the room: close to open microphones and pointing at them. Gain before feedback, not raw power, is what makes a wedge useful, and that comes from controlled coverage plus equalisation on each monitor send at line check.
Plan one mix per listening position rather than one per performer, and confirm the console has enough auxiliary buses to feed them. Count your input sources, add spares, and check the bus structure before the console is ordered rather than on the day.
Reading a frequency response figure honestly
A frequency response is only meaningful with a tolerance. “50 Hz to 20 kHz” without a decibel window says very little, because any loudspeaker produces something at 50 Hz if you accept a large enough drop. Published figures across manufacturers use different conventions, which is why comparing two numbers from different sources is unreliable.
What the figure is good for is a rough sorting. Across the cabinets in this range the published low-frequency limit runs from 20 Hz to 90 Hz, with a median of 60 Hz. A cabinet quoted from 90 Hz is a speech and background music box whatever else it claims; a cabinet quoted from 40 Hz is doing real low-frequency work.
Coverage: the specification people skip
Maximum SPL tells you how loud a cabinet gets on axis. It says nothing about where that level goes. A cabinet with 90 degrees of horizontal coverage and one with 60 degrees aimed at the same audience produce completely different results, and the narrower one will seem louder to the people in front of it and absent to those at the sides.
In practice two correctly aimed cabinets almost always beat one louder cabinet placed badly. When comparing options, put coverage angle next to maximum SPL rather than treating it as a footnote.
Gain structure, in order
Most systems that sound poor are not short of equipment. They have gain set in the wrong places, so the console runs quietly into an amplifier turned up to compensate, and the noise floor comes up with it.
- Set the amplifier input to a known reference, usually fully up or at a marked position, and leave it there.
- Set the processor output so the amplifier reaches full output at the processor's clip point.
- Set the console output to operate around its nominal level with headroom above.
- Set each channel's input gain so normal programme sits around the console's reference level.
Done in that order, the console's meters mean something and the limiter protects the drivers rather than catching an already-distorted signal.
Subwoofer placement changes more than subwoofer count
Two subwoofers either side of a stage and the same two in a central cluster produce different coverage. Spaced pairs create interference patterns across the audience that are audible as loud and quiet zones when you walk the room. A central cluster avoids that at the cost of sightlines.
Cardioid arrangements, where subwoofers are arranged and delayed to cancel rearward output, reduce low frequency on stage. That is worth real money on a loud stage, because low-frequency energy behind the subwoofers is what muddies the monitor mix and makes vocal microphones harder to control.
Cabling and connectors
Speaker cable gauge matters over distance. A long run of thin cable wastes amplifier power as heat and changes the damping the amplifier applies to the driver. For install work the run length is fixed, so this is a one-time calculation worth doing properly.
Keep speaker and mains cable separated where practical, and keep microphone lines away from both. Most live-sound hum is a cabling layout problem rather than an equipment fault.
A system for 200 people, specified end to end
- Tops: two full-range cabinets on stands, each covering half the room. Choose from the published maximum SPL and coverage angle, not wattage.
- Subs: two, centrally placed if sightlines allow, because the music programme runs below the tops' 60 Hz limit.
- Amplification: rated about 1.5 to 2 times each cabinet's continuous rating, read at the actual load impedance.
- Processing: crossover, delay and room equalisation, with limiting set from the speaker ratings.
- Monitors: four wedges on two mixes for a standard band layout.
- Console: enough inputs for every source plus spares, and at least two spare auxiliary buses.
- Microphones: one per source, plus a spare vocal microphone patched and ready.
Common mistakes
- Buying by wattage. It is the least informative number on the page.
- Skipping processing to afford more boxes. Tuning beats quantity in almost every room.
- Ignoring the load impedance when paralleling cabinets. The commonest way to damage an amplifier.
- Counting monitor mixes per performer rather than per position. Buys buses you do not need, or runs out where you do.
- Leaving gain structure to chance. Costs headroom and adds noise for free.
Decision criteria
- If the audience is under a few hundred in a normal room, choose point-source cabinets over an array.
- If the cabinet stops at 60 Hz and you are doing music, add subwoofers.
- If two cabinets share an amplifier channel, read the amplifier's rating at the combined impedance.
- If the budget is tight, buy processing before extra power.
- If the stage is loud, prioritise monitor coverage control over monitor wattage.
Browse Pro Audio, PA speakers, line arrays, power amplifiers, stage monitors and microphones.
Sources
- IEC 60268 – sound system equipment, including loudspeaker power rating methods.
- AES standards and information documents on loudspeaker measurement and system practice.
- Speaker figures come from the product data published for cabinets listed in this store.
Frequently asked questions
How do I match an amplifier to a speaker?
A common guideline is an amplifier rated about 1.5 to 2 times the loudspeaker's continuous RMS rating, with limiting in place. A 400 W cabinet suggests 600 to 800 W per channel at the cabinet's impedance.
Why is underpowering worse than overpowering?
An amplifier driven into clipping produces a distorted waveform with high harmonic content, and that energy goes to the high-frequency driver, which is not designed to handle it.
What happens if I put two speakers on one amplifier channel?
The impedance halves. Two 8-ohm cabinets in parallel present 4 ohms, so you must read the amplifier's rating at 4 ohms, not its 8-ohm figure.
Do I need subwoofers?
If your cabinets roll off around 60 Hz and you are reinforcing music, yes. For speech and background programme a full-range cabinet is usually sufficient.
When is a line array worth it?
Generally in larger rooms and open-air spaces where controlled vertical coverage keeps level consistent front to back. For a few hundred people, point-source cabinets are usually the better fit.
How many monitor mixes do I need?
One per listening position rather than one per performer, since people standing together can share. Check the console's auxiliary bus count supports that number.
