The best amplifier for outdoor speakers
For most people: the Fosi Audio BT20A, a small Bluetooth amp that lets you play from your phone. Want AirPlay, Chromecast or a TV connection? The WiiM Amp. Already on Sonos? The Sonos Amp. Connecting a TV? See outdoor speakers and TVs.
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Quick picks
Do outdoor speakers need an amplifier?
Wired outdoor speakers are passive: they have no power of their own, so they need an amplifier to drive them. The amp sits indoors, and speaker cable runs from it through the wall to each speaker.
Portable Bluetooth speakers and powered outdoor speakers are different. They have an amp and a battery or mains supply built in, so they don't need one. If you're buying wall-mounted garden speakers like the Polk Atrium 6, you need an amp.
You have three choices: use an amp or AV receiver you already own, add a small Bluetooth amp so you can play from your phone, or get a streaming amp that works with AirPlay, Chromecast or Sonos.
How much power do you need?
Less than you'd think. Outdoor speaker makers publish a recommended amplifier range, and anything inside it will work. What matters more is the speaker's sensitivity: how loud it plays from one watt.
| Speaker | Sensitivity | Recommended amp power | Volume from 50 W* |
|---|---|---|---|
| Polk Atrium 4 | 89 dB | 10–80 W | ≈106 dB |
| Polk Atrium 6 | 90 dB | 10–100 W | ≈107 dB |
| Klipsch AW-650 | 95 dB | up to 85 W | ≈112 dB |
*Peak level at 1 metre from one speaker, calculated from the published sensitivity. Real-world listening level outdoors is lower, because sound falls off with distance and there are no walls to reflect it.
Two rules of thumb: doubling amplifier power adds only about 3 dB, which is a small step up in loudness. And every 3 dB of extra speaker sensitivity halves the power you need. That's why an efficient speaker on a modest amp often beats an inefficient one on a big amp. Try our outdoor speaker calculator to check your own setup.
Fosi Audio BT20A
The simplest way to get music outside: pair your phone, turn it up.
The BT20A is a compact class-D amplifier built around two Texas Instruments TPA3116 chips. It's rated at 50 W per channel into 8 ohms and 90 W into 4 ohms, which is well inside what the Polk and Klipsch speakers in our guides ask for. It has Bluetooth 5.0 and one RCA input for a TV or other source, plus bass and treble knobs on the front.
It's one of the most popular amps of its kind on Amazon, with thousands of reviews. Put it on a shelf near where the cable enters the house; Bluetooth range is roughly 10–15 metres, less through thick walls.
- Power
- 50 W × 2 at 8 Ω
- Inputs
- Bluetooth 5.0, RCA
- Controls
- Volume, bass, treble
- Size
- 13 × 10 × 3.5 cm
Reasons to buy
- Play straight from your phone
- Plenty of power for efficient garden speakers
- Small and inexpensive
Reasons to avoid
- No Wi-Fi streaming or app
- Not weatherproof: keep it indoors
WiiM Amp
For people who want to stream from any app and run the garden from their phone or TV.
The WiiM Amp is a streaming amplifier: it connects to your Wi-Fi and works with AirPlay 2, Chromecast and Spotify Connect, as well as Bluetooth. It also has HDMI ARC, optical and RCA inputs and a subwoofer output. It's rated at 60 W per channel into 8 ohms (100 W into 4 ohms).
The big advantage over a Bluetooth amp is range and reliability: it streams over Wi-Fi, so your phone doesn't have to stay near the amp, and you can group it with other WiiM devices for music in more than one room.
- Power
- 60 W × 2 at 8 Ω
- Streaming
- AirPlay 2, Chromecast, Spotify Connect
- Inputs
- HDMI ARC, optical, RCA, USB
- Extras
- Subwoofer output, app
Reasons to buy
- Wi-Fi streaming from almost any app
- HDMI ARC for TV sound
- Multiroom with other WiiM units
Reasons to avoid
- Costs more than a Bluetooth amp
- Needs a good Wi-Fi signal where it sits
Sonos Amp
If the rest of your house is Sonos, this is the amp that makes the garden another room in the app.
The Sonos Amp powers passive speakers and adds them to your Sonos system, so you control the garden from the Sonos app alongside every other room. It's rated at 125 W per channel into 8 ohms, has an HDMI ARC input and RCA line input, works with AirPlay 2, and has a subwoofer output.
It's designed to pair with Sonos Outdoor speakers by Sonance, but it drives any passive speaker in range, including the Polk and Klipsch models we recommend.
- Power
- 125 W × 2 at 8 Ω
- Streaming
- Sonos app, AirPlay 2
- Inputs
- HDMI ARC, RCA
- Extras
- Subwoofer output
Reasons to buy
- Seamless with other Sonos speakers
- The most power of the amps here
Reasons to avoid
- The most expensive option
- Overkill if you don't use Sonos
Fosi Audio BT20A Pro
The bigger version of our top pick, for long gardens or party volume.
The Pro uses a more powerful TI TPA3255 chip, so it has far more headroom than the standard BT20A. You won't need it for a patio, but it's a sensible match for the Klipsch AW-650 in a long garden, or if you'll run the speakers loud for parties. It keeps the same simple Bluetooth and RCA setup.
Reasons to buy
- Much more power headroom
- Same simple Bluetooth setup
Reasons to avoid
- Bigger than the standard BT20A
- More power than most gardens need
Compare the amps
| Amp | Power (8 Ω) | How you play music | Best for |
|---|---|---|---|
| Fosi Audio BT20A | 50 W × 2 | Bluetooth, RCA | Most gardens |
| Fosi Audio BT20A Pro | Higher (TPA3255) | Bluetooth, RCA | Big gardens, parties |
| WiiM Amp | 60 W × 2 | Wi-Fi streaming, HDMI ARC, Bluetooth | Streaming and multiroom |
| Sonos Amp | 125 W × 2 | Sonos app, AirPlay 2, HDMI ARC | Sonos homes |
Running more than one pair of speakers
Each pair of 8-ohm speakers is an 8-ohm load per channel. Wire a second pair in parallel on the same terminals and the amp sees 4 ohms, which some amps can't handle for long. If you want speakers in two areas, use a speaker selector with impedance protection between the amp and the pairs, or give each area its own amp. Streaming amps like the WiiM and Sonos make the second option easy, because you can group them in the app.
Where to put the amp
Indoors, somewhere dry with a bit of air around it, as close as practical to where the cable goes through the wall. A shorter cable run means thinner, cheaper cable. Our installation guide covers the cable route and sizes step by step.
FAQ
Do outdoor speakers need an amplifier?
Wired outdoor speakers are passive, so yes: they need an amplifier or AV receiver to power them. Portable Bluetooth speakers and powered outdoor speakers have an amp built in and don't need one.
Can I use my old hi-fi amplifier for garden speakers?
Usually, yes. If it has speaker terminals (not just a headphone socket) and the speakers' impedance is within its rating, it will work. Many stereo amps also have a "Speakers B" output you can use for the garden.
Can I use an AV receiver?
Yes. Many AV receivers have a Zone 2 or Speakers B output designed for a second set of speakers, so the garden can play something different from the living room.
How many watts do I need for outdoor speakers?
Check the speaker's recommended amplifier power and stay inside it. With efficient speakers (around 90 dB sensitivity), 50 watts per channel is plenty for garden listening. Doubling the power only adds about 3 dB of volume.
Can I connect two pairs of speakers to one amp?
Only if the amp is rated for the combined load. Two 8-ohm pairs wired in parallel present 4 ohms per channel. The safer option is a speaker selector with impedance protection, or a separate amp for each zone.
Where should the amplifier go?
Indoors, somewhere dry and ventilated, close to where the speaker cable goes through the wall. Amps get warm, so don't shut them in a sealed cupboard.