Seiko 5KX Sonar SRPJ45 Watch Review - Why It's Not An SKX Replacement (But It Doesn't Matter)

Ask anyone who has been collecting watches for a while about some of their earliest pieces, and chances are the Seiko SKX will be on the list. Reference numbers SKX007 and SKX009 were some of Seiko's most popular dive watch models due to their durability, price, looks, and dimensions. When Seiko discontinued these watches a few years ago, it came as a shock to the community. Sure, models like the Prospex Turtle attempted to that hole, but those watches are more expensive and a bit bigger.

As you might expect, Seiko quickly remedied the situation...sort of. The Seiko 5 Sports line has similar styling to the original SKX and adds useful hacking and hand-winding but it lost its tool watch credibility. With a non-screw down crown, lack of a lume pip, clear case back, and half the water resistance of the 200m original, it was an attractive watch, but a not replacement for the SKX. Since it was released, a number of attractive colorways caught my eye, but I was never motivated to spend the money on an SKX poser. Until recently that is.

After seeing the attractive “Sonar” series in person, I was finally moved to buy one. It took me a while to figure out why, but I realized that the unique dial and teal color of the SPRJ45 moved it out of the SKX’s shadow. In my mind, it was now just a fun and attractive watch. Something that was different enough from the original that it didn’t feel like an imposter. Plus, buying one would finally give me a chance to try out the 5KX. 

First Impressions

This watch stands out due to how fun the dial is to look at. Not only is it an attractive color, but the visible day and date discs give you more things to notice the longer you stare at this watch. The glossy dial and metal surrounds on the hour markers play with light a lot more than anticipated.

The Details

The most obvious update to the Sonar version is its teal translucent dial (also available in brown in the SRPJ47 and a limited edition Brown/Teal SPRJ41, SBSA177). The dial has more of a reflective gloss finish than I expected with a hint of a sunburst pattern on it. This makes it very fun to look at in bright light, with subtle reflections dancing across the day and date discs.

The first twenty-minute section of the aluminum bezel insert is colored in a corresponding teal. It has the typical imprecise bezel feel of an entry-level Seiko, but this does allow some play to line up the 12-hour marker.

Additionally, while standard Seiko 5 models use a clear mineral crystal caseback, the sonar features one with a dark tint. I think that this looks cool, and it also hides the industrial, unfinished appearance of the 4R movement. The flat front crystal is also made from Seiko’s “Hardlex” mineral material. Expected for a Seiko in this price range.

The case finishing is attractive, but built to a cost. The top surface of the lugs are brushed, with polished curved sides to the case. The crown is also unsigned.

The hands are standard 5 Sports fare, but the second hand is finished in an attractive neon orange that creates a very fun contrast against the teal dial. Pair it with a bright orange strap, and it visually pops even more.

Wearing the Sonar

As with most Seikos, compact lugs and a well-thought-out case shape make the 5KX wear much better than its 42.5mm width might indicate. The wide bezel also visually shrinks the watch, as the dial is a bit smaller.

Legibility is surprisingly good for a watch with such a busy dial. The hands are bright white, and the dial is tinted enough that the day and date discs don’t distract you during normal wear.

Night-time legibility is also quite good, with Seiko’s green Lumibrite providing illumination. Prospex models tend to have a thicker (and thus brighter) application, but this lume is still quite good, especially for being one of Seiko's entry-level automatics. It helps when it's accented by a Luminous Elastic Strap though!

Strap/Bracelet

I bought this watch pre-owned, and it had been stripped of its original bracelet along the way. Normally it would have included an oyster-style bracelet with pins and sleeves securing the links and a single-fold deployant with a safety latch and twin-trigger release.

Based on photos, and my past experience with Seiko, it's likely comfortable, with basic brushed finishing. Nothing special, but appropriate for the price.

I’ve been wearing it on a number of different StrapHabit straps, my favorites being the orange Vented Rubber, and a teal Ridge Rubber. Scroll to the end of the article to shop some of the straps shown on this watch.

Movement

While Seiko did downgrade some of the 5KX's specs, one improvement that it made over the SKX is the movement. The SKX used the 7S26 movement, which was Seiko’s entry-level automatic with day and date, with without the ability to hand wind or hack. The newer 4R series uses the same movement construction as the original and adds these features. Now wearers can stop the timekeeping by pulling out the crown to set the time with precision and can wind it using the crown, rather than shaking it to get it to start running. This is even more convenient on the 5KX as the crown does not screw down.

Conclusion

Even with its downgrades on paper, the 5KX is more than enough watch for most people. It still had 100m of water resistance, and not having a screw-down crown actually makes it more convenient to set and wind. Many of the available colorways would make a great daily wear watch.

I'm happy that I held out for the Sonar, however. I enjoy staring at its fun dial, and it's just unique enough to make it stand on its own.

Specifications: 

Name: Seiko 5 Sports
Reference Number: SRPJ45
MSRP: $300
Diameter: 42.5mm
Height: 46mm
Thickness: 13.4mm
Lug Width: 22mm
Weight: 165g (with bracelet)
Movement: 4R36
Power Reserve: 41 hours
Water Resistance: 100m
Crystal: Hardlex
Crown:  Push-pull
Bezel: Unidirectional, 120 clicks
Bracelet: Stainless steel three-fold clasp with push button release (not shown)

 

Shop Other Straps for the Seiko Sonar SRPJ45: 

Ridge FKM Rubber Quick Release

 

Smooth FKM Rubber Quick Release

 

 

Distressed Canvas Quick Release

Waffle FKM Rubber Quick Release