Polk Atrium 4 vs 5 vs 6 vs 8
Short answer: the Atrium 6 for most gardens. The Atrium 4 for balconies and small patios, the Atrium 5 where the 6 won't fit, and the Atrium 8 SDi for big gardens or where you only have room for one speaker.
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All four side by side
| Atrium 4 | Atrium 5 | Atrium 6 | Atrium 8 SDi | |
|---|---|---|---|---|
| Woofer | 4.5" | 5" | 5.25" | 6.5" |
| Tweeter | 0.75" aluminium | 0.75" aluminium | 1" aluminium | 2 × 1" aluminium |
| Frequency response | 75 Hz – 25 kHz | 60 Hz – 25 kHz | 50 Hz – 27 kHz | 45 Hz – 27 kHz |
| Sensitivity | 89 dB | 90 dB | 90 dB | 91 dB |
| Recommended amp | 10–80 W | 10–100 W | 10–100 W | 10–125 W |
| Size (H × W × D) | 21.9 × 14.5 × 17.0 cm | 26.2 × 17.1 × 19.7 cm | 29.7 × 19.5 × 22.2 cm | 32.7 × 21.6 × 23.3 cm |
| Sold as | Pair | Pair | Pair | Single |
| Buy | Check price | Check price | Check price | Check price |
From Polk's published specifications as listed by authorised retailers. Atrium 8 SDi size includes the bracket. All four are 8-ohm passive speakers.
Polk Atrium 4
For balconies, small patios and covered seating where you sit close.
The smallest Atrium has a 4.5-inch woofer and fits under low eaves and next to door frames. Its rated bass stops at 75 Hz, so it sounds lighter than the bigger models, which matters less when you're only a few metres away.
Polk Atrium 5
A step up in bass from the 4, for when the 6 is too big for the space.
The Atrium 5 has a 5-inch woofer with rated bass down to 60 Hz, and the same 90 dB sensitivity and 100 W rating as the Atrium 6. It keeps the smaller 0.75-inch tweeter of the Atrium 4. If both fit, the Atrium 6 is the better buy.
Polk Atrium 6
The one most gardens need: fuller sound, loud from a small amp.
A 5.25-inch woofer and 1-inch tweeter, with rated bass down to 50 Hz. At 90 dB it reaches lively listening levels across a typical garden from a 50-watt Bluetooth amp. It's our top pick overall, and we compare it head to head with the Atrium 4 and the Klipsch AW-650.
Polk Atrium 8 SDi
For big gardens, or where one speaker has to do the job of two.
The flagship has a 6.5-inch woofer, two 1-inch tweeters and rated bass down to 45 Hz. Its single/dual input switch lets one speaker play both stereo channels, which helps on a narrow side wall or when you can only run cable to one spot. It's sold singly, so buy two for a stereo pair, and it takes up to 125 W, so it suits a bigger amp like the Fosi BT20A Pro.
Which size for your space?
| Your space | Pick |
|---|---|
| Balcony, small or covered patio | Atrium 4 |
| Patio where the 6 won't fit | Atrium 5 |
| Typical garden, deck or terrace | Atrium 6 |
| Large garden, pool, or one speaker only | Atrium 8 SDi |
Not sure? The outdoor speaker calculator checks whether a model will be loud enough at the distance you sit.
FAQ
Which Polk Atrium is best?
For most gardens, the Atrium 6. It has a 5.25-inch woofer and 1-inch tweeter, reaches down to 50 Hz and is rated at 90 dB, so it gets properly loud from a small amp. The Atrium 4 suits small spaces and the Atrium 8 SDi suits large ones.
Is the Atrium 5 or Atrium 6 better?
The Atrium 6 has a slightly bigger woofer, a 1-inch tweeter instead of 0.75-inch, and deeper rated bass (50 Hz against 60 Hz). Both are rated at 90 dB and 10 to 100 W. Choose the 5 only when the 6 is too big for the space.
Is the Polk Atrium 8 sold as a pair?
The Atrium 8 SDi is usually sold as a single speaker, so you need two for a stereo pair. Its switch also lets one speaker play both stereo channels.
What does SDi mean on the Atrium 8?
It refers to the single/dual input switch. In one position the speaker plays left and right channels on its own; in the other it works as one half of a stereo pair.
Do Polk Atrium speakers need an amplifier?
Yes. All Atrium models are passive and need an amplifier or AV receiver. A small Bluetooth amp such as the Fosi Audio BT20A is enough for the Atrium 4, 5 and 6.