Syskonics / Guide
How to Choose Speaker Wattage: 10W vs 20W vs 40W
Why the number on the box is not the number that matters, how power taps actually work, and what wattage different rooms really need.
The most common misunderstanding in PA system design is that a 40W speaker is always drawing 40W. On a 100V line system it is not. It draws whatever its tap is set to — and choosing that setting well is most of what separates a system that sounds right from one that does not.
This guide explains what a tap is, how to pick one, and how the choice feeds into the amplifier you need.
What a power tap actually is
A 100V line speaker has a small transformer behind the driver. That transformer has several connection points — taps — and each one presents a different load to the amplifier. Change the tap and you change how much power that speaker takes, and therefore how loud it is.
The SYS-106 is a clear example. It is a 40W speaker, and its published taps are 5W, 10W, 20W, 40W and 8 ohm. Wired to the 10W tap, it draws 10W from the amplifier and costs you 10W of your power budget. The 40W rating tells you what it is capable of, not what it will use.
This is why specifying a higher-rated speaker is rarely wasted. It gives you headroom to turn a zone up later without replacing hardware.
Choosing a tap for the room
Start from how much competing noise there is and how far the listener sits from the speaker. These are working starting points, not rules — commission the system by ear and adjust the taps afterwards.
| Space | Typical tap | Why |
|---|---|---|
| Quiet office, meeting room | 5W – 10W | Low ambient noise, listener close to the speaker |
| Classroom, reception, retail floor | 10W – 20W | Moderate noise, speech has to stay clear |
| Corridor, canteen, assembly hall | 20W – 40W | Larger volume, more people, more noise |
| Workshop, warehouse, covered outdoor | 40W – 60W | High ambient noise and long throw distances |
Sensitivity matters as much as wattage
Two speakers at the same tap will not be equally loud if their sensitivity differs. Sensitivity is how much sound a speaker produces for a given input, and across the Syskonics wall range it runs from 89 dB to 93 dB.
Three decibels of sensitivity is worth roughly as much as doubling the power. So the 93 dB SYS-208 at a 30W tap is comparable in level to a 90 dB speaker at 60W — while using half the amplifier budget. When you are comparing two models, read sensitivity alongside rated power rather than in isolation.
Turning taps into an amplifier size
Once every speaker has a tap, the amplifier calculation is simple addition. Total the taps, then add headroom so the amplifier is not running flat out continuously — 20 to 30 percent is a sensible margin.
- Twelve ceiling speakers at 10W = 120W. A 150W or 250W amplifier is appropriate.
- Twenty wall speakers at 20W = 400W. A 500W amplifier is appropriate.
- Eight wall speakers at 40W = 320W. A 350W amplifier is the minimum; 500W leaves room to grow.
Common mistakes
Two errors account for most disappointing installations. The first is using too few speakers at too high a tap — one loud speaker at the end of a corridor is unpleasant beneath it and inaudible at the far end. More speakers at lower taps is almost always better.
The second is leaving no headroom on the amplifier. An amplifier run at its limit distorts on peaks, which is exactly when speech clarity matters most, and runs hot enough to shorten its life.
Products in this guide
SYS-104
Wall Mount Speaker
- 100V Line
- Classroom
- Office
SYS-106
Wall Mount Speaker
- 100V Line
- Industrial
- Commercial
SYS-208
Wall Mount Speaker
- 100V Line
- Industrial
- Commercial
CLS-406
Ceiling Speaker
- 100V Line
- Conference
- Office
Common questions
01Is a 40W speaker louder than a 20W speaker?
Only if it is tapped higher. On a 100V line the tap setting determines the power drawn, so a 40W speaker set to its 10W tap draws 10W. The higher rating gives you the option of more level, not automatically more level.
02How do I calculate the amplifier size I need?
Add up the tap setting of every speaker on the line, then choose an amplifier rated 20 to 30 percent above that total. Twenty speakers at 20W is 400W of load, which suits a 500W amplifier.
03What wattage do I need for a classroom?
For a standard classroom, 10W to 20W per speaker is a good starting point, using two to four speakers rather than one. That gives even coverage without any position being uncomfortably loud.
04Can I change the tap after installation?
Yes. The tap is a wiring connection at the speaker, so it can be changed at any time. This is why installing a higher-rated multi-tap speaker is a sensible hedge — the room can be turned up later without new hardware.