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iRobot Roomba s9 Plus Review: A nearly perfect robot

Sack your cleaner. It's time to invest in the best robot vacuum money can buy

iRobot Roomba S9
iRobot Roomba s9 Plus Review: A nearly perfect robot
MSRP $1,399.00
“Skip this year's smartphone upgrade and spend your money on the best robot vacuum around.”
  • Superb cleaning performance
  • Self-emptying dust bin
  • Multi-floor smart mapping
  • Precise object detection and navigation
  • High price

In the world of robot vacuums, the story of 2019 is one of continued price deflation and increased accessibility. Platoons of low-priced cleaners cascading from far-off factories, advancing into homes across the globe with the smarts, performance, and convenience to make traditional cleaner brands like Bissell blush and Dyson despair. “The days of thousand-dollar robovacs are behind us,” we thought.

Well, think again.

A glance at our Best Robot Vacuums for 2020 list demonstrates that you can pick up a reasonable robotic cleaner for as little as $200. That is, if you’re comfortable trusting aging, entry-level technology to sweep your floors. iRobot’s Roomba S9 Plus (s9550) is not for you. This top-of-the-line model is positioned as the iPhone 11 Pro Max of robot vacuums and, at $1400, is priced similarly to Apple’s leading-edge smartphone.

That may seem another lazy Apple comparison, but hear me out. We’ve come to expect smartphone manufacturers to reinvent their hardware platforms on an annual basis. Robot vacuum vendors, not so much. But that’s exactly what iRobot has done.

We’ve come to expect smartphone manufacturers to reinvent their hardware platforms on an annual basis. Robot vacuum vendors, not so much.

Last year’s Roomba i7+ was the most innovative robot vacuum we’d ever seen. Smart mapping, powerful suction, upgraded processing that powered a swathe of convenient features. Oh, and it emptied itself after every clean. It aced the competition and iRobot’s own sales expectations, so we’re told. However, one year later, it’s clear that wasn’t enough to satisfy the company’s designers who, with the Roomba s9 Plus, have turned up the innovation amps to eleven.

Built from the ground up for improved edge and corner cleaning

Rather than tweak the i7, iRobot has built its latest model from the ground up. The result is a robot vacuum that looks noticeably different on the outside, with significant enhancements under the hood. The s9 Plus is the Roomba’s first flat-fronted, D-shaped design to reach the market. It eschews the standard hockey puck form factor with the goal to improve edge and corner cleaning. Neato’s Botvac series has employed a similar design for many years with the same target, and while the shape certainly improves access into corners, we’ve found cleaning performance to be only incrementally better than circular models.

Flip the s9 Plus over and you’ll see a number of additional enhancements designed to tackle that issue. A larger, more powerful cleaning head is positioned further forward in the chassis than other Roombas. A supporting vacuum motor delivers 40-times the suction of older generations (such as the Roomba 600 series), delivering a deeper clean on carpets and enhancing performance in corners and edges. The traditional side-sweeping brush has also been moved forward, a new five-spoke design allowing better reach into corners and along the sides of the walls.

Terry Walsh / Digital Trends

The s9 Plus also debuts a new 3D sensor in the front bumper that enhances Roomba’s wall detection. Scanning at 25 times per second, it allows the robot to hug walls closely, improving edge cleaning. As a bonus, the new sensor also allows the s9 Plus to navigate into – and out of – cluttered environments, boosting floor coverage.

The fabulous CleanBase dirt disposal charging station has been retained – this time out with a thin, differentiating band of color around its waist – but you can also purchase the s9 Plus on its own. Why you would invest $1100 on a high-end robovac without its headline-grabbing party trick, I don’t know. Other than the slight design tweak, the CleanBase looks and performs similarly to the model supplied with the i7+. iRobot tells us they’ve improved the connection between the s9 Plus robot and the base to provide a better seal during emptying. They boast 99% pollen and mold allergen capture in the bag.

The CleanBase uses the same disposable bag system as the i7+, which we found to be a neat solution. At the end of each clean, the s9 Plus trundles back to the base for recharging, initiating a formidable whoosh from the CleanBase as it sucks the dirt out of the robot. Each bag holds up to 30 bins of dust and debris from the robot and neatly self-closes as it’s extracted from the base. Replacement bags are priced at a reasonable $14.99 for a pack of three, meaning the s9 Plus does require some ongoing investment. However, we’d expect that to be fine for homeowners happy to spend $1400 on a robovac.

Stylish and sturdy

Out of the box, the Roomba s9 Plus is dressed to impress, with a new chassis design that blends understated, curvy matte black plastics with a bronze brushed-metal highlight. The center lid flips up smoothly to expose the internal dust bin which, at 550 ml, is the largest you’ll find on a Roomba. Of course, if you’re using the CleanBase, you’ll only encounter the dust bin when changing filters ($40 for a three-pack). As you’d hope from any $1400 device, the Roomba s9 Plus is well-built throughout with thoughtful attention to detail. When powered on, you’ll notice a subtle ring of illumination under the center lid providing status notifications. Under the hood, rubber seals at either end of the dust bin prevents dust, pollen, and dirt escaping during operation. While the s9 Plus’ exterior is likely to suffer a few bumps and grazes in its life, it feels tough enough to cope.

Well-built throughout with thoughtful attention to detail.

On the underside, the s9 Plus is endowed with two cylindrical rubber brushes sporting alternative ridges for scooping up dust, hair, and dirt. Both brushes are significantly wider than those equipped on the i7. There’s only a single corner brush on the right, while the two spring-loaded, rubberized wheels allow the robot to clamber easily over thick rugs and chunky floor trims.

Terry Walsh / Digital Trends

Simple setup, easy cleaning

Once unpacked, your first clean with the s9 Plus is only a matter of minutes away, thanks to a quick and effortless setup using the iRobot smartphone app. The new model supports iRobot’s Smart Mapping feature, which uses an array of on-board sensors and vSLAM navigation to build a detailed plan of each floor in your home. Unlike basic models, which may not offer any mapping or can only cater for single-floor properties, the Roomba s9 Plus is able to charter and clean multiple floors.

It takes a few cleans for the robot to build up sufficient data and produce the map, following which you can tweak the layout and label rooms easily in the iRobot app. Sadly, maps can’t be shared between devices, so if you’re upgrading from a Roomba i7 and have your home already mapped, the s9 Plus has to start from scratch.

It’s worth the effort, though. Once your maps are created, you can set the s9 Plus to work cleaning your entire floor, or focus its attention on a single room. Support for Google Home and Amazon Alexa works brilliantly here, allowing you to order a specific room clean with a single voice command.

With the robot set for Detailed Cleaning (the maximum power setting), you’ll certainly hear the powerful vacuum motor as it fires up, but it’s not loud enough to distract you from your work. Those with more sensitive hearing can opt for a one-tap Quick Clean setting, available from the app, while a Custom option allows you to tweak suction power and cleaning passes to your personal preference.

Elsewhere in the app, you’ll find an easy scheduling feature for building daily or weekly cleaning cycles. Again, once maps are complete, you can target individual rooms or an entire floor plan and the same custom cleaning options are available to tailor power settings. It’s all very simple.

Advanced object detection and nimble navigation prevents hard bumps and snags

During the first few cleans, we did notice the robot gently bump into furniture a few times as it got to know its new surroundings. We were pleased to see it the s9 Plus hugs walls very closely. Indeed, standing in front of the robot as it traveled towards us, we could see the corner brush striking baseboards as it swept. The Roomba successfully detected and navigated around most obstacles in its path, expertly weaving in between the legs of our dining room chairs. We deliberately planted tricky obstacles, such as cables and bags with trailing straps around the floor, to see how the s9 Plus coped and while the robot trundled over them and almost got trapped, it was able to pause and maneuver to prevent its wheels from becoming jammed.

As with any robot vacuum, detecting low-height obstacles can be an issue for the s9 Plus. During its first run, the s9 Plus steamed right into a kitchen tray holding two pet food bowls, pushing it into the lounge. Not to be thwarted, iRobot’s new Keep Out feature allows you to manually highlight areas of your floor plan that the robot should avoid. It’s the latest in a roadmap of software feature enhancements that iRobot has planned for the s9 Plus and i7 in the coming months.

The first cleaning run lasted an hour and six minutes, almost depleting the s9 Plus’ lithium-ion battery, but considering the robot was running at maximum cleaning power, we’re pleased overall with the s9 Plus’ battery life. In larger rooms, where the cleaning cycle has not been completed, the s9 Plus will return to its base to charge. But the robot only rests until it has sufficient battery capacity to finish vacuuming, boosting efficiency.

Only a single, slight issue marred that first run. The s9 returned to the CleanBase but found itself unable to find its charging point. It repeatedly climbed the shallow CleanBase ramp, reached the top, then reversed back down the ramp to try again before its batteries were depleted. Moving the CleanBase slightly away from the wall resolved the issue.

First-class cleaning performance

In terms of cleaning performance, the Roomba s9 Plus is simply the best robot vacuum we’ve tested. While the powerful suction motor makes light work of dust and debris on hard floors, carpets, and rugs, it really slams the competition – and any other Roomba before it – on edge cleaning.

The Roomba s9 Plus is simply the best robot vacuum we’ve tested.

We scattered coffee grains on the floor alongside our hallway baseboards to replicate heavy dust. Typically, we find robot vacuums struggle to clean closer than half an inch to the wall. The s9 Plus, however, is able to clean much closer to walls than any other robot vacuum we’ve reviewed, sucking up almost all of the grains we scattered.

Corner cleaning was decent – in line with leading contenders, but we found the robot’s brush wasn’t quite able to reach far enough into corners to scoop out all of the debris. So, the s9 Plus won’t quite release you from the chore of pushing around a regular vacuum once in a while, but it comes very close.

Terry Walsh / Digital Trends

Our take

The Roomba s9 Plus may be one of the most expensive robot vacuums on the market but it’s also the smartest, easiest to use, and best performing autonomous cleaner around. You’ll love the headline-grabbing convenience of Roomba’s self-emptying CleanBase, but the s9 Plus’ real magic is its smart mapping, precise navigation, and leading-edge cleaning performance that extends the gap between iRobot’s premium robot vacuums and discount also-rans.

Is there a better alternative?

Short of hiring a cleaner to vacuum your house for you, no. The Roomba i7+ will remain on sale with a price drop to $999, so if you like the idea of a self-emptying robot vacuum, but wish to save yourself $400, then it’s a great option that doesn’t quite match the s9 Plus on cleaning performance. Want to spend less? Nowadays, you’ll find solid robot vacuums available to meet every budget, but none of them are better than the Roomba s9 Plus.

How long will it last?

Like all robot vacuums, you’ll need to look after your Roomba with new filters and brushes. A regular clean-out to remove trapped hair, dust and debris from around the vacuum and CleanBase is also advised to keep your s9 Plus in good order. But you should expect this robot vacuum to live a long life, with semi-regular feature updates and enhancements gilding your initial investment.

Should you buy it?

Yes. If you have $1,400 spare to invest in a robot vacuum, you can’t do better. For a premium price, you get premium performance.

Too rich for your blood? Find affordable alternatives by taking a look at the best robot vacuum deals and iRobot Roomba deals available today.

Terry Walsh
Terry Walsh is a British-born technology writer living in Canada, whose first computer was a cherished 48k ZX Spectrum…
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