The Sonos Arc Ultra might not need a separate subwoofer

By Simon Cohen Published October 19, 2024

The new Sonos Arc Ultra is packed with 15 amps and 14 drivers, giving the Dolby Atmos soundbar the ability to reproduce 9.1.4 channels of sound, according to the company. That’s a big step up from the original Sonos Arc, an 11-driver, 5.1.2 system. And while the increase in surround channels (from 5 to 9) and height channels (from 2 to 4) is impressive, it’s the lonely “1” in the middle of the Arc Ultra’s channel setup that might make the biggest difference.

That middle .1 represents the low frequency effects (LFE) channel — the one that’s punted over to a dedicated subwoofer when you have one available. It’s the channel that gives movies the deep, powerful rumble we most closely associate with theatrical sound. On its own, the Sonos Arc does a decent job with low frequencies, but it relies on the same drivers that produce its mid-frequency sounds to do so. These drivers aren’t optimized for LFE sounds, which is why many Arc buyers add a Sonos Sub or Sub Mini, increasing the cost of their system by as much as $799.

The Arc Ultra, however, possesses a new “Sound Motion” driver — a four-motor, dual-membrane woofer. (That’s the rectangular box at the top of the exploded image below.) It has two membranes (the portion of the driver that moves air) in an area that would normally only have room for a single membrane. Sonos says this unusual arrangement “delivers exceptional bass in a revolutionary flat, compact design,” and claims that it gives the Ultra “double the bass” of the regular Arc.

The Sound Motion driver is based on patented technology that Sonos acquired when in bought Mayht, a Netherlands-based audio company, in 2022. This 2020 article in audioxpress.com explains how Mayht’s driver technology works.

But what, exactly, does “double” mean?

“When we say Arc Ultra produces up to twice as much bass as Arc,” Sonos told Digital Trends, “it means that at maximum volume there is 6dB more low-end output. This means that Arc Ultra has more dynamic capability in the low end which presents content with more realism.”

Curiously, the Arc and Arc Ultra have the same 50Hz limit on their low-end frequency response. So while bass won’t be any lower on the Ultra, it will be louder, which will give it greater impact.

I reached out to Hilmar Lehnert for his thoughts on how Sonos might tune the Ultra. Lehnert is one of the few people with deep knowledge of both Sonos and Mayht. He worked at Sonos for nine years, the last two as the company’s audio technology manager. When he left in 2020, he began a stint as a member of Mayht’s board of advisers, which ended when the company was acquired in 2022.

“It definitely would,” he said. “This reduces the need for the mid woofers to move a lot of air and their design and tuning can focus on further improving spectral and spatial performance.”

Can the Sound Motion driver replace a dedicated sub? No. As much as it would be awesome if a single soundbar could fill both roles, we’re not there yet. However, Sonos’ new driver technology narrows the gap. For some folks, it could make the difference between wanting a subwoofer and needing one.

This wouldn’t be a first for soundbars — I was mightily impressed by the Klipsch Flexus Core 200‘s solo bass performance — but it would a first for a Sonos soundbar. That could go a long way toward making folks feel better about the Ultra’s slightly more expensive price.