Construction: Co-polyester Monofilament
Gauge: 15G (1.35 mm), 16G (1.30 mm), 17G (1.25 mm), 18G (1.20 mm), 18L (1.15 mm)
Length: 40 feet (12.2 M)
Test Racquet / Tension
Wilson Blade 16 x 19 v7/16 G (1.30 mm) @ 50 lbs
While it may not be the biggest brand in the tennis world, Kirschbaum has a long history of producing high quality, German engineered tennis strings. New for 2019, they are introducing a polyester string called Xplosive Speed. This string boasts a pentagonal profile for maximum grip and spin production. Kirschbaum also applies their signature ThermoFusion Technology which pre-stretches the string at the factory for improved playability and tension maintenance. Having enjoyed previous strings in the Kirschbaum lineup, I was eager to get my hands on the new Xplosive Speed for a trial run.
Xplosive Speed definitely played livelier than my usual string setups. I’d rate its power level as a medium. It provided a good amount of easy power without feeling like I was constantly fighting to keep it under control. I was surprised at how subtle the 5-sided profile of the string really was. It was actually a really slick string and it was hard to really tell it had a shaped design. The strings seemed to have low string-to-string friction, allowing it to generate a solid level of spin. I didn’t think it had the same type of grip offered by some of the more aggressively shaped strings, but there was still plenty to hit topspin groundstrokes and put good movement on kick serves, etc. Control was solid for the most part, although I found the launch angle to be inconsistent at times. Some shots seemed to exit at a steeper angle than I expected and sailed on me. This was especially true if I was too casual in my swing. The more aggressively I swung, the more I was rewarded with lively power and a more controlled response.
I enjoyed the feel of Xplosive Speed throughout my time with it. The softening agents applied to it did a good job of giving the string flex without making it overly mushy feeling. It played with a clean response and didn’t exhibit any buzzing or increased harshness as it wore out. I was able to feel the ball on the strings well and it gave me a good sense of what the ball was going to do as it left the string bed. This was one of the more comfortable polyesters I’ve hit with recently and it seems brands are getting increasingly better at producing soft polys that still have solid playability and response. I played the string at 50 lbs and could see it performing well both below and above that tension depending on player preferences.
Durability was an area that surprised me a bit. It was a 16g sample, which was thicker than normal for me, so I expected it to hold up for awhile. In reality, the string exhibited heavy notching within the first 3 hours of use and I broke it after about 6 hours of use. This seemed to be a byproduct of the string’s softness as I can usually get to double digit court hours in thinner gauge but firmer polyesters. The good news was that Xplosive Speed remained highly playable the entire time until it broke. It took the same initial tension drop that’s typical with polyester, but then settled in nicely and lost minimal tension each time out. Even right before I broke it, it was still playing with consistent response and control, allowing me to hit confidently up until the end.
It seems 2019 is a year focused on comfort in the tennis world. Kirschbaum has introduced a new polyester to their lineup that offers outstanding comfort, excellent power and solid spin. It is a highly playable string that can add pace to the ball and brings enough spin to create movement off the court. Poly players looking a balanced blend of spin and power wrapped in a layer of comfort should enjoy playing with Kirschbaum Xplosive Speed.
About the Reviewer: Matt Locke formerly served for 3 years as the Junior Programs & Development Coordinator for USTA-Idaho. He is a PTR certified coach and is an active USTA 4.5+ League and Tournament player.