If you work in security, you already live in the low-voltage world—access control, intrusion, cameras, networks. Yet many integrators hesitate when they hear “70-volt” or “100-volt” loudspeakers, assuming they’re dealing with something closer to an electrician’s scope. In reality, 70V/100V speaker systems are generally considered low-voltage, power-limited audio circuits, designed for the same types of commercial buildings where you already run cable every day.
In reality:
Keep reading to understand how the two systems work, what they are good at, and how to choose the right one for your project.
When you hear “70-volt system” (or “100-volt system” in many regions outside North America), it refers to a constant-voltage audio system.
Instead of directly driving a single speaker at 4 or 8 ohms, the amplifier output is stepped up to a higher voltage (70V or 100V). Each speaker on the line has a small transformer with selectable wattage taps such as:
You choose the tap based on how loud you want that speaker to be in that area. To size the amplifier, you:
This design was created for distributed audio: long cable runs, many speakers, and large coverage areas where you need consistent paging and background sound.
Because the line voltage is higher, the current is lower for a given power level. That gives you three practical benefits:
An 8-ohm system is the more familiar “direct” or low-impedance approach:
This is common in:
Low-impedance systems can offer more precise control over the speaker driver and can be preferred where critical listening or higher-fidelity music is the main goal.
This is the key concern for many security integrators.
In day-to-day language, “70 volts” or “100 volts” sounds like something that ought to involve an electrician. In practice, 70V/100V loudspeaker lines are treated as low-voltage, power-limited circuits when used with properly listed amplifiers, speakers, and wiring, and installed according to code.
In many jurisdictions:
That said, code is local. Licensing rules, categories (e.g., Class 2, Class 3, limited energy), and inspection practices vary. You should always confirm requirements with the authority having jurisdiction (AHJ) in your area.
The practical takeaway:
For most commercial paging, announcement, and background sound applications, 70V/100V systems are not treated the same way as 120V/230V mains power. They are designed and regulated as low-voltage audio distribution circuits.
For security integrators, 70V/100V systems are often the practical choice when:
Typical examples:
One amplifier can drive dozens or even hundreds of speakers. You simply tap each speaker at the desired wattage for that area, then add up the total.
Campus-style layouts, long corridors, and multi-building sites are common in education, healthcare, and corporate environments.
In these cases, constant-voltage lines:
Facilities change. Wings are repurposed, rooms are subdivided, departments grow or shrink.
In a 70V/100V system, it is usually straightforward to:
In many security-driven projects, the priority is:
Constant-voltage systems are widely used for these use cases and are well supported by commercial paging and mass-notification equipment.
There are also many cases where 8-ohm (or other low-impedance) systems are the right choice.
Examples:
If the zone only needs a few speakers and the runs are short, an 8-ohm system is simple and effective.
Where cable runs are short and confined to one area, voltage drop and line loss are not major concerns. Low-impedance wiring is easy to implement and troubleshoot.
In areas where music or detailed audio quality matters more:
Low-impedance systems are often preferred, provided the rest of the chain (amplifiers, DSP, speakers) is designed to match that performance level.
Many AV devices include built-in low-impedance amplifier channels. Using 4/8-ohm speakers keeps the wiring model simple in those local systems and avoids extra components.
Here’s a quick reference you can scan when deciding which approach fits a given part of your project:
| Question / Factor | 70V/100V (Constant-Voltage) | 8-Ohm (Low-Impedance) |
|---|---|---|
| Typical application | Distributed paging/BGM, large coverage | Local AV, small zones, higher-fidelity audio |
| Number of speakers per amp channel | Many (dozens or more) | Usually a small number |
| Design method | Sum of speaker wattage taps | Total impedance calculation |
| Cable run length | Very good for long runs | Best for short runs |
| Expansion and changes | Generally easy (add speakers / change taps) | May require recalculating load |
| Audio priority | Intelligible voice, even coverage | Critical listening and detailed program material |
| Typical locations | Halls, classrooms, wards, warehouses, corridors | Control rooms, meeting rooms, small retail, AV spaces |
Neither column is “right” or “wrong.” They simply describe different tools.
It is common to see both approaches used together in the same facility:
You do not mix 70V/100V and 8-ohm on the same amplifier output, but you can:
Many commercial speakers from manufacturers such as AtlasIED include multi-tap transformers plus an 8-ohm bypass in the same enclosure. That allows the same model to be used in both types of systems or reconfigured later if the system design changes.
You don’t have to take sides. In a K-12 school, hospital, corporate campus, industrial site, retail center, or hotel, it is normal to see both systems used in different zones.
If you treat 70V/100V as another standard low-voltage option—alongside the systems you already install—you gain flexibility to design audio and paging that match the operational needs of the site without unnecessary complexity or assumptions about “high voltage.”