Ergonomic office chair with lumbar support and footrest: Welax S9 Pro hands-on review

The Welax S9 Pro offers some interesting ideas and features—though we’ve already seen them in this or a similar form on other ergonomic office chairs. These include, among other things, the extendable footrest and the ease of operating the most important functions using a single lever.

The highly adjustable armrests are also practical, though a bit too loose for our taste. On the plus side, the backrest and headrest can be adjusted high enough that, at just over 180 cm tall, I have no issues with them hitting my shoulders—unlike with other models I’ve tried. We also liked the sturdy, one-piece base.

If that were all, the Welax S9 Pro would offer an attractive overall package at its current price of around $500. Unfortunately, however, our testing also revealed some points of criticism. Among other things, the seating comfort didn’t fully convince us, as the non-height-adjustable lumbar support sits too low for our taste. There are also some concerns about quality and durability, particularly regarding the wobbly leg rest. 

The manufacturer’s suggested retail price for the Welax S9 Pro is listed at $499.99. However, this office chair—which is available in three colors—can often be purchased for significantly less, for example, directly from the manufacturer or on Amazon.

On its website, Welax promises “full body ergonomics” for the S9 Pro with simple one-button adjustment. We put it to the test to see what that means and whether this ergonomic office chair actually delivers in practice. Our findings are detailed in our review of the Welax S9 Pro.

The ergonomic office chair S9 Pro from Welax is delivered in two boxes, the larger and heavier of which weighs a good 23 kg. It contains all parts except for the base. The base is packed in the smaller box and, unlike many other office chairs, does not need to be assembled from multiple parts.

After unpacking the components—most of which are still wrapped in bubble wrap, which on the one hand creates a lot of waste but on the other hand ensures they arrive well-protected—it’s time to begin assembly. In total, the package includes seven large components and many small ones, including various screws (with one spare of each). In addition to the required Allen wrenches, two white cotton gloves are also included.

The instructions (in German, English, and French) consist of 8 steps, each explained with relatively small but clear illustrations. First, the five casters are inserted into the crossbar, followed by the gas spring. Next, the extendable footrest is screwed under the seat. The single screw used for this purpose is—unfortunately, there’s no other way to put it—of inferior quality. We therefore strongly recommend using a proper screwdriver of the correct size—rather than the included screwdriver/Allen wrench combination, which is also of rather poor quality.

The next step is to connect the seat and the backrest using three solid screws. Next, the two armrests—each labeled “L” and “R”—are screwed into place under the seat using two screws each. After that, the assembly can be placed onto the gas spring and thus connected to the base. The final step is a bit fiddly: The headrest is secured with two screws that are screwed into the backrest from below.

Overall, the assembly went well—aside from the issues mentioned—and can be completed in under 30 minutes. It’s easier with two people, but it’s also doable alone with a bit of skill and strength.

At first glance, for example, the Welax S9 Pro is reminiscent of the Sihoo Doro C300 Pro V2 (starting at about 510 euros on Amazon), which we recently tested. There are also many similarities in terms of ergonomic features, but a few differences as well.

Welax also highlights the one-button adjustment feature on the S9 Pro. This is a lever located on the right side beneath the seat. Depending on the direction of operation, this lever allows you to move the seat forward or backward by approximately 5 cm, adjust its height (approximately 8 cm), and adjust the angle of the backrest. However, there is also a second lever on the backrest to lock the lumbar support, as well as buttons to lock the footrest and headrest.

In terms of quality, the swivel base—which consists of a single cast metal piece—stands out. This is not the case with many other manufacturers, whose swivel bases often have to be assembled from multiple parts. Here, the Welax S9 Pro makes a very sturdy impression. As high-quality as this solid component is, some of the others are unfortunately rather cheap. For example, the plastic footrest bracket is attached to the extendable metal tube under the seat with a single small screw. This doesn’t give the impression of being particularly durable, especially since we’ve already commented on the quality of the screws.

The problem is that while the upper part of the backrest can be adjusted in height by a few centimeters, the lumbar support’s attachment to the backrest strut unfortunately cannot be adjusted, even though the support itself moves slightly. It also gets in the way of the backrest in the upper area. In our opinion, this reduces seating comfort rather than enhancing it.

On the positive side, however, the headrest on the S9 Pro—which is also height-adjustable—doesn’t collide with my shoulders. Standing at around 180 cm—not exactly a giant—I’ve already encountered this problem in several other ergonomic office chair reviews, such as the Sihoo Doro C300 (approx. 370 euros on Amazon). This isn’t the case with the Welax S9 Pro, however. We also liked the versatile, adjustable armrests, though we found them a bit too easy to move for our taste. However, we’ve made this same criticism of many other ergonomic office chairs we’ve tested, such as the LiberNovo Omni (approx. 1,150 euros on Amazon).

The footrest is adjustable in length, and the mesh support surface can be locked into place with a button. However, when sitting with your feet up, it feels just as flimsy as it did during assembly. While this provides a fairly pleasant level of flexibility, it doesn’t exactly inspire confidence when it comes to stability and durability.