Sonoff SNZB-09P Review: A 105 dB Zigbee Siren With Tamper Reporting and a Backup Battery
Ten alarm tones, four volume levels and a red flashing light strip, plus a built-in battery that keeps the siren alive when the power goes out.
The Sonoff SNZB-09P is the audible half of a Zigbee alarm: it pairs to a Zigbee hub and turns any sensor trigger into up to 105 dB of sound, a red flashing light, or both, with ten selectable tones and an alarm duration you can set anywhere up to 15 minutes. Its two standout specs are the tamper reporting, which tells you when the siren has been pulled off its base, and the built-in lithium backup battery, which keeps the device online for months in silent mode and lets it still sound after mains power is cut. It is an indoor unit with no IP rating and it needs a hub, so it belongs inside a Zigbee system rather than on an exterior wall, but for that role it is a cheap way to make automations impossible to ignore.
- Zigbee alarm systems
- Home Assistant and SmartThings setups
- Indoor deterrence
- Leak and smoke sensor alerts
- Budget buyers
Pros
- Up to 105 dB alarm with four selectable volume levels
- Ten alarm tones, so different sensors can sound different
- Red flashing light strip that can run with or without the sound
- Built-in backup battery keeps it running after a power cut, over 300 days in silent mode
- Tamper reporting when the siren is removed from its base
- Alarm duration configurable up to 15 minutes
- Works with Home Assistant via Zigbee2MQTT, plus SmartThings, Alexa and Google Home
- Compact 81 x 81 x 35 mm body with screw or adhesive mounting
- Two year warranty
Cons
- Requires a Zigbee hub, with no Wi-Fi, Z-Wave, Thread or Matter option
- Indoor only, with no IP rating for outdoor mounting
- No Apple HomeKit support
- IFTTT support is listed as requiring a membership
- Backup battery is built in and not user replaceable
- Light brightness is not specified by the manufacturer
- No voice prompts, only alarm tones
- No presence simulation
Who is the Sonoff SNZB-09P for?
This is a siren for a home that already runs Zigbee. It has no Wi-Fi radio of its own, so it joins an existing network through a Zigbee hub and is then driven by automations. Sonoff lists its own gateways (the Zigbee Bridge Pro and Ultra, NSPanel Pro and iHost) plus Home Assistant through a Sonoff dongle with Zigbee2MQTT or ZHA, and a SmartThings Zigbee hub with the Sonoff driver. The practical use case is turning a silent trigger into something the whole floor hears: a door or window contact, a motion or presence sensor, a water leak sensor, or a camera event. Because sound and light can be enabled independently, the same device can also serve as a quiet visual indicator in a room where a 105 dB alarm would be unwelcome.
What the SNZB-09P offers
Sound output tops out at 105 dB at one metre, with four volume steps of roughly 75, 82, 93 and 105 dB, so it can be tuned to a hallway or a garage without being all-or-nothing. Ten alarm sound effects mean different sensors can be given different tones, which makes it possible to tell a leak alert from an intrusion alert without looking at a phone. On the front there is a red circular light strip that can flash alongside the sound or on its own. Alarm duration is configurable from one second up to 15 minutes. It is powered over USB-C at 5V, and the built-in 600mAh lithium battery takes over automatically when that power is removed, keeping the device online for more than 300 days in silent mode and recharging itself once the cable is live again. Tamper reporting flags when the body has been twisted off its base, and it can be used as an automation trigger in its own right, alongside triggers for alarm, external power loss and the device going offline. The 81 x 81 x 35 mm ABS body mounts with screws or adhesive, and Sonoff backs it with a two year warranty.
What to know before you buy
A Zigbee hub is mandatory: there is no Wi-Fi, Bluetooth, Z-Wave, Thread or Matter path to this device. Voice assistant control exists but is indirect, arriving through the eWeLink cloud integration for Alexa and Google Home, and limited to turning the alarm on and off. IFTTT support is listed by Sonoff as requiring a membership, and Apple HomeKit is not supported at all. The unit is specified for indoor use with no IP rating, so it is not a substitute for an exterior bell box. The backup battery is built in rather than user swappable, brightness of the light strip is not published, and there are no spoken voice prompts, only tones. There is also no presence simulation feature. On the Home Assistant side, Zigbee2MQTT support is in place, while native ZHA support was still pending at launch and needs a script from Sonoff for full functionality; the SmartThings path also relies on a driver and does not carry over-the-air firmware updates.
Is the Sonoff SNZB-09P worth it?
For a Zigbee system that currently has no way to make noise, it is an inexpensive upgrade that adds the two features cheap sirens usually skip: a backup battery so cutting the power does not silence the alarm, and tamper reporting so removing the siren is itself an event. The trade-offs are the ones you would expect at this tier, namely indoor-only construction, hub dependency and a light whose output is not specified. Compare it against outdoor-rated sirens with IP ratings if you need something mounted on an exterior wall, and against mains-only sounders if you want the cheapest option and do not care about power cuts.
Frequently asked questions
Does the Sonoff SNZB-09P need a hub?
Yes. It is a Zigbee 3.0 device with no Wi-Fi radio, so it needs a Zigbee hub. Sonoff's own gateways work, as does Home Assistant with a Sonoff Zigbee dongle, or a SmartThings Zigbee hub with the Sonoff driver.
How loud is it?
Up to 105 dB at one metre, with four volume levels that correspond to roughly 75, 82, 93 and 105 dB.
Will it still sound if the power goes out?
Yes. It runs from USB-C but has a built-in 600mAh lithium battery that takes over automatically when external power is lost, and recharges when power returns. In silent mode that battery keeps it online for more than 300 days.
Does it work with Home Assistant?
Yes. It is supported by Zigbee2MQTT, which exposes the siren, the sound and light toggles, tone, volume, duration, battery level and tamper status. ZHA needs a script from Sonoff for full functionality.
Can the light be used without the alarm sound?
Yes. Sound and light are controlled independently, so it can be set to sound only, flashing light only, or both together.
Can it be installed outdoors?
No. It is specified as an indoor device and carries no IP weather rating.


