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:
- 70V/100V speaker systems are generally considered to be low-voltage, power-limited audio circuits.
- In many regions, they can be installed by low-voltage contractors, similar to access control, intrusion, and other signaling systems (always confirm with the local AHJ).
- Both 70V/100V and 8-ohm have clear pros and cons. Neither is “better” overall. Each is useful in different situations.
Keep reading to understand how the two systems work, what they are good at, and how to choose the right one for your project.
1. What a 70V/100V System Really Is
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:
- 1 W
- 5 W
- 7.5 W
- 15 W
- 30 W
You choose the tap based on how loud you want that speaker to be in that area. To size the amplifier, you:
- Add up the wattage taps of all the speakers on that line.
- Add some headroom (commonly 20–30%).
- Choose an amplifier that can support that total.
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:
- Less loss over distance – better performance on long runs.
- Smaller-gauge cable may be acceptable compared to an equivalent low-impedance system.
- Simpler system expansion – adding more speakers is usually just a matter of adding their wattage to the total.
2. What an 8-Ohm System Is
An 8-ohm system is the more familiar “direct” or low-impedance approach:
- The amplifier output is rated at 4 or 8 ohms.
- Each speaker is also rated at 4 or 8 ohms.
- You wire speakers in parallel or series/parallel so that the total impedance seen by the amplifier stays within its rated load.
This is common in:
- Small rooms and local zones.
- AV systems in conference rooms, boardrooms, and classrooms.
- Situations where audio quality is a higher priority than broad coverage.
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.
3. Is 70V/100V “High Voltage”?
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:
- These circuits fall under low-voltage or limited-energy categories, similar to many security and communication circuits.
- Low-voltage contractors are permitted to install them, just as they install access control, intrusion detection, camera power, and other signaling conductors.
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.
4. When 70V/100V Makes Sense
For security integrators, 70V/100V systems are often the practical choice when:
A. You Have Many Speakers on One System
Typical examples:
- Hallways and classrooms in K-12 and higher ed.
- Patient rooms and corridors in healthcare.
- Production floors in industrial facilities.
- Dining, lobby, and corridor areas in hospitality.
- Large retail floor plates.
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.
B. You Have Long Cable Runs
Campus-style layouts, long corridors, and multi-building sites are common in education, healthcare, and corporate environments.
In these cases, constant-voltage lines:
- Handle longer runs with less signal loss.
- Often allow you to stay with reasonable cable sizes instead of moving to heavier gauge wire.
C. You Need Flexibility Over Time
Facilities change. Wings are repurposed, rooms are subdivided, departments grow or shrink.
In a 70V/100V system, it is usually straightforward to:
- Add additional speakers to a run.
- Change tap settings to adjust local volume.
- Reconfigure coverage without redesigning the entire load calculation, as long as the amplifier has the necessary capacity and the system is rechecked for compliance.
D. You Are Focused on Paging, Alerts, and BGM
In many security-driven projects, the priority is:
- Clear announcements.
- Staff pages.
- Emergency messages.
- Background music at modest levels.
Constant-voltage systems are widely used for these use cases and are well supported by commercial paging and mass-notification equipment.
5. When 8-Ohm Systems Make Sense
There are also many cases where 8-ohm (or other low-impedance) systems are the right choice.
A. Small, Self-Contained Zones
Examples:
- Security control rooms.
- Small lobbies.
- Individual retail spaces.
- Single conference rooms.
If the zone only needs a few speakers and the runs are short, an 8-ohm system is simple and effective.
B. Short Distances
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.
C. Higher-Fidelity Program Audio
In areas where music or detailed audio quality matters more:
- Executive floors.
- Boardrooms and training rooms.
- Certain hospitality and retail locations.
Low-impedance systems are often preferred, provided the rest of the chain (amplifiers, DSP, speakers) is designed to match that performance level.
D. Integration with AV Hardware
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.
6. Side-by-Side Comparison
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.
7. Mixing 70V/100V and 8-Ohm in the Same Project
It is common to see both approaches used together in the same facility:
- 70V/100V for building-wide paging and common areas.
- 8-ohm systems for meeting rooms, presentation spaces, or specialty environments.
You do not mix 70V/100V and 8-ohm on the same amplifier output, but you can:
- Use different amplifier channels or separate amplifiers for each type.
- Use loudspeakers that support both 70V/100V and 8-ohm bypass, depending on how that zone is wired.
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.
8. Key Takeaways for Security Integrators
- 70V/100V systems are low-voltage, power-limited audio circuits, commonly installed by low-voltage contractors under the same general framework as other signaling and communications wiring, subject to local code and licensing rules.
- 8-ohm and 70V/100V are complementary tools. Use constant-voltage for wide coverage and long distances, and use low-impedance where zones are small or audio quality is a higher priority.
-
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.”