Sonoff SNZB-09P Review: A Very Loud Zigbee Siren That Is Best Paired With Zigbee2MQTT
The Sonoff SNZB-09P is a Zigbee indoor siren that turns any sensor trigger into up to 105 dB of sound, a red flashing light, or both, with ten tones, four volume levels and a built-in backup battery. Owners praise how loud it is, how quickly it pairs and how fast it reacts, mostly in Home Assistant setups. The recurring caveats are support rather than hardware: under ZHA some controls need a custom quirk or are not exposed at all, SmartThings owners ran into trouble, and a few units fired alarms on their own or arrived dead. It is an inexpensive way to give a Zigbee system an alarm that cannot be ignored, and it is best for people who already run Zigbee2MQTT or are comfortable tinkering.
- Home Assistant setups
- Zigbee2MQTT users
- Indoor deterrence
- Leak and door sensor alerts
Pros
- Very loud, up to 105 dB, with four volume levels
- Pairs quickly and reacts fast to triggers
- Ten alarm tones, so different sensors can sound different
- Red flashing light that works with or without the sound
- Built-in backup battery keeps it running after a power cut
- Tamper reporting when it is removed from its base
- All controls show up in Zigbee2MQTT
- Works with Home Assistant and SmartThings, plus Alexa and Google Home via eWeLink
Cons
- Some controls need a custom quirk or are missing under ZHA
- SmartThings owners ran into trouble getting it recognized
- Speaker can sound shrill or cheap to some owners
- Light ring has no brightness or pattern settings
- A few units fired alarms on their own or arrived dead
- Built-in battery and an off switch on the outside of the case
- Requires a Zigbee hub and no Apple HomeKit or Matter support
- Indoor only, with no IP rating
Who is the Sonoff SNZB-09P for?
It is a siren for a home that already runs Zigbee. There is no Wi-Fi radio on board, so it joins a Zigbee network and is driven by automations: door contacts, water leak sensors, doorbells or a mailbox sensor can each set it off. Owners use it as an alarm and, at a lower volume, as a notification sounder for events such as the doorbell or the mailbox. Sound and light can be enabled independently, so it can also flash silently.
What owners like
The first thing owners mention is volume. It is loud enough to hurt the ears at close range, and the lower steps still work as notifications. Pairing is the second praise: owners call it easy, and in Zigbee2MQTT the tone, volume, light and alarm duration all show up straight away. Response to a trigger is quick, and Home Assistant needs no subscription or cloud account for it. Owners also like the built-in backup battery that keeps it sounding through a power cut, the tamper report when it is lifted off its mount, and the possibility of running it from a USB-C charger. It runs on native Zigbee without a Sonoff bridge.
What to know before you buy
Integration depth depends on how it is connected. Under ZHA in Home Assistant, owners say a custom quirk from Sonoff is needed for full control and that the tone, volume and strobe controls may still be missing or unreliable, while Zigbee2MQTT exposes everything; one owner says the alarm stayed at its lowest level under ZHA. SmartThings owners reported trouble getting the siren recognized at launch. Some owners find the speaker shrill or a little cheap, a couple expected more volume, and the light ring has no brightness or pattern settings. The off switch sits on the outside of the case and the back is not magnetic. The battery is built in rather than replaceable, tamper reporting covers removal from the wall mount, not the USB cable, and a handful of units sounded the alarm on their own or never powered on at all. It is an indoor unit with no IP rating.
Is the Sonoff SNZB-09P worth it?
For a Zigbee system that has no way to make noise yet, it is a good value, and owners who run it through Zigbee2MQTT are the most satisfied. If the hub is ZHA or SmartThings, expect some setup work and read the current integration notes first. Look at an outdoor-rated siren if it has to go on an exterior wall.
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 or coordinator, such as a Zigbee dongle running Zigbee2MQTT or ZHA in Home Assistant, or a SmartThings hub with the SONOFF driver.
How loud is the Sonoff SNZB-09P?
Up to 105 dB at one metre, with four volume levels of roughly 75, 82, 93 and 105 dB. Owners find the top steps very loud indoors, though a couple expected more from it.
Should I use ZHA or Zigbee2MQTT with it?
Both work, but owners report that Zigbee2MQTT exposes every control (tone, volume, light and duration) right away, while ZHA may need a custom quirk and can leave some controls out.
Will it still sound if the power goes out?
Yes. It runs from USB-C, and its built-in 600 mAh lithium battery takes over automatically when external power is lost, then recharges when power returns. In silent mode the battery lasts over 300 days.
Does it work with Apple HomeKit or Matter?
No. It works with Home Assistant and SmartThings over Zigbee, and with Alexa and Google Home through the eWeLink cloud integration, but not with Apple HomeKit or Matter.
Can it be installed outdoors?
No. It is an indoor device with no IP rating.












