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String Playtest Comparison: Kirschbaum P2 vs Signum Pro Poly Plasma

About the play testerAbout the String

Tester: Midlife Crisis of Talk Tennis message board

Playing Level: 4.5 - 5.0

Regular playing equipment: Prince Thunder Rip, 28", 358 grams, 11 pts. HL, 382 SW, 115 sq. in. headsize, Signum Pro Poly Plasma 1.28, 67 mains/crosses on a crank lockout stringer (Gamma X-ST).

Game Style: Aggressive all-court, fast swing speeds, semi-western forehand, one hand backhand and can hit heavy slice to heavy topspin off both sides.

Strings being tested: Kirschbaum P2 vs Signum Pro Poly Plasma

Gauge: Kirsch P2: 17, Signum PPP: 17

Racquet(s) string is in: Prince Thunder RIP

Tension: 67 lbs

Signum Pro Poly Plasma 17 (1.23) String
Durable, spin friendly and with more comfort than traditional polyester offerings, Poly Plasma is a solid choice for the modern, aggressive player.


Both strings were strung in the same racquet, using one piece for the 16X19 pattern and without pre-stretching.

The Kirschbaum P2 measured 39'9" and weighed 21 grams out of the pack. Stringing used 35' and added 18 grams of weight.

The Signum Pro Poly Plasma measured 40'8" and weighed 21 grams out of the pack. Stringing used 34'4" and added 17 grams of weight.

Both strings act like typical polys. They have moderate coil memory and can tangle if not handled carefully. They are both clean, smooth strings that string up without leaving residue on the clamps, linear gripper, or on the hands. Knots for both strings snug up well and hold without slipping, but do require a firm pull to cinch the knot tightly. There is not a lot of difference in feel between these two when stringing up the racquet, though the Signum Pro Poly Plasma is more elastic when being pulled. I normally use the 1.28 version of Signum Pro Poly Plasma and the 1.23 version that was supplied did stretch slightly more. However, the 1.25 P2 was still slightly less elastic than even the 1.28 Signum Pro Poly Plasma. The Signum Pro Poly Plasma required 8 inches, or 2%, less string. Weaving the crosses was easy with both strings because of their smooth surface. The last few crosses were more difficult as there was less room to maneuver the weave, but no more so than any other poly string. Both strings felt extremely tight and stiff when first strung, and both lost some tension as they sat overnight.


The P2 is less powerful on all shots, but more so on softer shots. On serves, you can see that the ball moves slower, and on an average of ten first serves, a radar gun measured the ball speed to be 3-5 MPH slower than I normally get with Signum Pro Poly Plasma. On groundstrokes, I felt confident hitting the ball flatter than with Signum Pro Poly Plasma when going for hard shots from the baseline, and these had a trajectory that seemed to indicate they had more topspin than the swing would seem to give. Hitting high, loopy topspin shots felt more natural with the P2 than the Signum Pro Poly Plasma. These shots had more spin but less speed than the SPPP, but the higher bounce worked well against my level of opponent. I seemed to notice that the ball trajectory on these shots was slightly lower with the P2, which worked with the lower ball sped to make the shot land shorter. Volleys had less pop and required a more firm stroke to put the ball away. Volleys below the net seemed to have just the right amount of power, and the ball would go deep without having to consciously cut down on the stroke. Probably the most surprising thing is that the "hot spot" I have with the Signum Pro Poly Plasma is not there with the P2. The ball never flew wildly, and there is a more consistent level of power across the entire sweetspot.

The Signum Pro Poly Plasma is a more powerful string. Full swings are rewarded with a lot of pop, and booming flat first serves or overheads feel natural. Signum Pro Poly Plasma also produces a lot of ball speed when taking big uppercut swings at the ball, and you get both a lot of spin and a lot of pace. It is very easy to produce a winning shot off a midcourt sitter. The downside is that there are a couple of times each set when the ball just flies and goes a surprisingly long distance out, even though the stroke and timing of the shot feels normal. The power level of Signum Pro Poly Plasma makes it necessary to hit with some topspin from the back of the court, especially when going for a maximum speed shot. Volleys have a lot of pop, and shots above the level of the net are easy to put away. However, there are times on stab volleys off hard shots where the ball is very difficult to keep in the court.


The P2 has more control, not only because it is a lower powered string but also because in my racquet it produces a more consistent ball response across the entire stringbed and sweetspot. At first, I felt like I had to compensate for the lower power by swinging harder, but once I realized that the ball never flew wildly, I started using a flatter, more easily controlled swing path. After about ten hours of play, I felt like I had much more directional accuracy, and in a surprising number of instances put the ball almost exactly where I intended. Touch shots were especially good, and I was able to hit drop shots and drop volleys that I had been unable to consistently do with Signum Pro Poly Plasma. The response from soft shots to hard shots, and flat shots to spinny shots, is more linear and predictable with the P2, at the expense of some ball speed. The P2 seems to be less affected by incoming spin than Signum Pro Poly Plasma.

The control from Signum Pro Poly Plasma is very good. With the exception of the couple of shots every set that just seem to sail, the ball leaves the stringbed with very consistent trajectory and spin. The good power from the string makes it possible to block back awkward shots with a small controlled stroke, which helps get the ball back in play more consistently. However, compared to the P2, it has a higher power level and also has that small hotspot where the ball speed is higher than expected. Also, Signum Pro Poly Plasma is more affected by the spin on the incoming ball, and this is most noticeable when volleying slice shots, when it seems to take an unnaturally open face to keep from netting the ball.


The Signum Pro Poly Plasma is more comfortable than the P2. It has a greater feel of pocketing the ball when hit on the sweetspot, a more elastic feel and more give when a ball is mis-hit. The P2 has a sharp impact feel that is especially harsh on hits high off the stringbed, but the remaining vibration seems to be well dampened. Neither string created any elbow or wrist soreness or tenderness, and when hit on the sweetspot, both strings offer a nice, solid, muted feel, though some of that may be due to the stringbed dampener (Gamma worm) that I use.


Both strings produce a lot of spin. The Signum Pro Poly Plasma produces a slightly higher ball trajectory off the stringbed, and combined with a slightly higher amount of power, I hit topspin groundstrokes that were deeper but did not bounce as high. The P2 would hit balls about three to five feet shorter but with about the same height bounce despite the lower trajectory. Once I compensated for the shorter ball depth by either swinging harder or aiming higher, the topspin groundstrokes became very effective, dipping hard towards the ground and bouncing up sharply.

On slice shots, the P2 allowed me to hit a low, penetrating slice that seems to just skim the ground. It was harder to hit these shots with Signum Pro Poly Plasma and these kinds of shots would float and tend to go long. There was also a more natural feel of being able to hit slice shots with the P2, and it seemed to be less affected by an incoming slice shot.

On serves, because I needed to swing faster with the P2 to get the same ball speed, I was able to hit some wicked spin serves. However, I had a problem getting depth on second serves. On some shots where I really tried to spin it without generating a lot of ball speed, the ball would even land in the first half of the service court. With the Signum Pro Poly Plasma, I felt like I could both spin it and bomb flat serves, and hitting flat serves is when the difference in power is most noticeable.


For me, feel is most about consistency of response and confidence in my ability to hit all shots. The feel of the impact needs to correlate with the stringbed response, and here the P2 was by far my favorite. The P2 has a sharper/harsher impact that increases and decreases linearly with the impact force. The feedback from the strings let me more easily gauge how the ball was going to react from hit to hit, and gave me confidence to hit shots like drop volleys, which I would only rarely attempt with the Signum Pro Poly Plasma. The Signum Pro Poly Plasma feels springy and there's not as clear of a differentiation of impact feel on softer shots. It feels a lot like a multi in this respect, and this springy feel doesn't give me confidence to try touch shots. Maybe because I wanted or expected more difference in the feel on really soft shots, I ended up either dumping drop shots and drop volleys into the net, or popping them up for sitters when using Signum Pro Poly Plasma.

String Movement

With the P2, after 30 hours of play, the strings still had no movement. I ended up cutting out the strings after 35 hours of play, and they had just started to move around at that time. Because I replaced the P2 with the Signum Pro Poly Plasma, I could not do a back-to-back comparison to see how much playability had been lost with the P2, but it felt like it had retained its elasticity better than Signum Pro Poly Plasma usually feels at 40 hours. As far as string movement itself, the P2 moves less than Signum Pro Poly Plasma.

I am a long time user of Signum Pro Poly Plasma and it is my preferred string. I find that Signum Pro Poly Plasma stays put for the first 20 hours or so, then starts to move slightly but not enough to require straightening. For about the next 20 hours of play after that, the string will gradually start to move more and more. Beyond 40 hours, I've found the playability to go away as the string loses elasticity, and this correlates to when the string starts moving enough to require occasional straightening. Because this has been so consistent, I use the amount of string movement as my gauge to restring.

Tension Maintenance

Initially, it felt as if the Signum Pro Poly Plasma were better at retaining tension. The P2 seems to lose more tension initially, then stay constant for the remainder of the time that I used it. The Signum Pro Poly Plasma loses some tension initially, seems to stabilize, and then loses a little bit more tension as the string starts to move around at about 20 hours of play. Overall, for the first 10-15 hours of play, Signum Pro Poly Plasma seems to hold tension slightly better, but once over 30 hours of play, the P2 seems to hold tension slightly better. The P2's tension loss, because it happens all at once when the string is newer, provides a more consistent stringbed for a longer period of time. Overall, both of these strings are among the better of polyester strings at maintaining tension.


At 35 hours, Signum Pro Poly Plasma is getting close to the time when its playability has degraded and I'm ready to cut it out. Signum Pro Poly Plasma also has minimal notching, and also does not look like it is close to breaking.

I played a total of 35 hours with the P2, and it did not feel as if the string had lost as much elasticity as I normally see with Signum Pro Poly Plasma. There was minimal notching, and the string was not close to breaking.

For both strings, the playability of the string is likely to go away before the string breaks, with an edge to the P2 for retaining its playability longer.


All playing time was indoors on medium speed hardcourt, with temperatures between 55 and 70 degrees F.

Court Surface:

Medium speed hardcourt, indoors.

Overall Summary

Both of these strings seem to have all of the characteristics of the new co-poly strings, in that they produce a lot of spin, have excellent durability, have very good tension maintenance, and do not have the harsh feel of older types of poly strings.

For players using polyester strings for the first time, those coming from a synthetic gut or multifilament string would probably like the Signum Pro Poly Plasma better. It has a softer, more elastic feel that would give a good transition to a poly type string without a huge risk of joint problems. The power level seems fairly similar to a synthetic gut string.

Players transitioning from Kevlar strings or from harsher poly strings, or those players looking to decrease their racquet power, will like the P2. The P2 would be a very good alternative to a Kevlar string in that it provides less shock, more spin, a little more power, and similar durability. It produces a very consistent stringbed response and provides excellent control for those players who can generate their own power.

After having used Signum Pro Poly Plasma exclusively for the last year, I am switching to the Kirschbaum P2 without any hesitation.


Signum Pro Poly Plasma 17 70
Kirschbaum P2 17 50
Kirschbaum P2 17 95
Signum Pro Poly Plasma 17 70
Kirschbaum P2 17 90
Signum Pro Poly Plasma 17 80
Overall Playability
Kirschbaum P2 17 90
Signum Pro Poly Plasma 17 80
Signum Pro Poly Plasma 17 75
Kirschbaum P2 17 65
Kirschbaum P2 17 90
Signum Pro Poly Plasma 17 90
String Movement
Kirschbaum P2 17 95
Signum Pro Poly Plasma 17 90
Tension Maintenance
Kirschbaum P2 17 90
Signum Pro Poly Plasma 17 85

Playtest date: December, 2006.
All content copyright 2007 Tennis Warehouse.

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