Pay Attention to Vibration Frequency

PistolPete23

Hall of Fame
Most people pay attention to RA when it comes to assessing stiffness but not enough to a racquet's characteristic vibration frequency (VF). In short, the vibration frequency is "how fast" a frame oscillates after ball impact as felt in the hand. Racquets with a high frequency number will have a crisp response, whereas low VF values will feel plush. In other words, while RA measures quasi-static flex, the vibration frequency is a better metric for the dynamic stiffness of the racquet, i.e., the stiffness of the racquet during play. While RA and VF are strongly correlated, the relationship is not 1:1. That's why it's possible for a racquet to play significantly softer than its RA indicates, and the opposite could also be true. Case in point is the Head Pro Tour 2.0. It's target RA is 65, but has a measured VF of 136 Hz, which is comparable to racquets with RA ~60. These numbers are consistent with the prevalent feedback that the PT 2.0 plays a lot softer than its RA indicates.

For a given RA, you can lower its VF by adding weight. So next time you see a racquet with all the specs you like except for RA, don't immediately dismiss it. Check its VF first on TWU or consider customizing with weight.
 

Purestriker

Legend
Most people pay attention to RA when it comes to assessing stiffness but not enough to a racquet's characteristic vibration frequency (VF). In short, the vibration frequency is "how fast" a frame oscillates after ball impact as felt in the hand. Racquets with a high frequency number will have a crisp response, whereas low VF values will feel plush. In other words, while RA measures quasi-static flex, the vibration frequency is a better metric for the dynamic stiffness of the racquet, i.e., the stiffness of the racquet during play. While RA and VF are strongly correlated, the relationship is not 1:1. That's why it's possible for a racquet to play significantly softer than its RA indicates, and the opposite could also be true. Case in point is the Head Pro Tour 2.0. It's target RA is 65, but has a measured VF of 136 Hz, which is comparable to racquets with RA ~60. These numbers are consistent with the prevalent feedback that the PT 2.0 plays a lot softer than its RA indicates.

For a given RA, you can lower its VF by adding weight. So next time you see a racquet with all the specs you like except for RA, don't immediately dismiss it. Check its VF first on TWU or consider customizing with weight.
Great points!
 

Purestriker

Legend
I’ve found that VF correlates the closest to how comfortable a racquet is far more than RA stiffness. I’ve also been telling players to check VF to get an idea of how comfortable it is. Unless you know how to find it on TWU, it is not an easily accessible spec though.
Can you share the link? I cannot find it.
 

PistolPete23

Hall of Fame
I’ve found that VF correlates the closest to how comfortable a racquet is far more than RA stiffness. I’ve also been telling players to check VF to get an idea of how comfortable it is. Unless you know how to find it on TWU, it is not an easily accessible spec though.
I'm making a racquet exploration tool. It also has specs like recoil weight and polarization index. It's a side project, so probably will need another 2-3 weeks until ready to launch. Stay tuned.
 

Roforot

Hall of Fame
This may perhaps be related, but on TennisNerd podcast, he once interviewed Chris from TW who cautioned about his experiment to go low w/ tension. He said something to the effect that at 30# the vibration synchronized and gave his elbow discomfort which was not present at lower or higher tension.

I am not explaining perfectly, so if he is lurking in the forums, I hope Chris can elaborate on his experience.
 

PistolPete23

Hall of Fame
This may perhaps be related, but on TennisNerd podcast, he once interviewed Chris from TW who cautioned about his experiment to go low w/ tension. He said something to the effect that at 30# the vibration synchronized and gave his elbow discomfort which was not present at lower or higher tension.

I am not explaining perfectly, so if he is lurking in the forums, I hope Chris can elaborate on his experience.

Very interesting. String bed vibration and frame vibration are separate. When they vibrate at the same frequency, I think it's theoretically possible for resonance. In other words, the string bed vibration adds to the amplitude of the frame vibration, so even though the frequency of vibration remains unchanged, off-center hits will feel harsher on the arm. I'm not sure if this was what Chris was talking about.
 

Roforot

Hall of Fame
Very interesting. String bed vibration and frame vibration are separate. When they vibrate at the same frequency, I think it's theoretically possible for resonance. In other words, the string bed vibration adds to the amplitude of the frame vibration, so even though the frequency of vibration remains unchanged, off-center hits will feel harsher on the arm. I'm not sure if this was what Chris was talking about.
yes I think that is what he was saying but he said it was different for each frame w/ specific string and tension.
 

tele

Hall of Fame
This certainly would explain Babolat's reputation. Despite having highish RA's, they have super high VF's.
In the compare racquets tool, their VFs seemed to line up with wilson and yonex racquets with similar RAs. I did not check thoroughly, though.
 
I don't think there is any question at all that racquets VF under 140 are best for arm safety. Those in the mid 150's up are a problem for arm safety. I certainly agree this is the single most important racquet measurement.
 

Icsa

Professional
There might be more to it. I'm guessing weight is a major factor too.
My elbow gets irritated faster when playing with a "soft" Blade 98 measured at 130VF/60RA than with a "stiff" RF97 at 150/70.
 

PistolPete23

Hall of Fame
There might be more to it. I'm guessing weight is a major factor too.
My elbow gets irritated faster when playing with a "soft" Blade 98 measured at 130VF/60RA than with a "stiff" RF97 at 150/70.
Weight is absolutely a factor. For the same impact, the lighter racquet will likely vibrate at a higher amplitude. In other words, there’s less mass to absorb the energy of impact.
 

Tao69

Semi-Pro
Some where on one of these forums it was said that foam filling the racquets has the effect of lowering the amplitude but not the frequency. Assuming that's true, does foam filling to some extent negate some the impact from the a slightly higher RA in a lighter frame?
 

mmazzinin1

Semi-Pro
Actually, what matters is the combo string + racquet, with anything >600 hz being potentially armful. Duration of vibration matters as well
 

Crocodile

G.O.A.T.
Interestingly the silver anniversary of the clash 100 had a lower VF than the original V1Clash 100. Maybe the silver anniversary had a batch of slightly lower RA figures. The PK Black Ace 300, 315 and Pro also have very low numbers with their VF scores.
 

esm

Legend
How about different type of paint/clear coat? Will it give different VF reading on the same model of racquet?
 

Tao69

Semi-Pro
How about different type of paint/clear coat? Will it give different VF reading on the same model of racquet?
I did wonder this myself, I have a Clash 98v1, and as much as many are not a fan of the soft touch finish, I do wonder if that was an intentional choice by Wilson to keep the stiffness and/or vibrations down.
 

mmazzinin1

Semi-Pro
Cash 100, 100 Reverse an
Interestingly the silver anniversary of the clash 100 had a lower VF than the original V1Clash 100. Maybe the silver anniversary had a batch of slightly lower RA figures. The PK Black Ace 300, 315 and Pro also have very low numbers with their VF scores.
Clash 100 v1 standard, reverse and silver have all the same VF score based on twu database (121)
 

anarosevoli

Semi-Pro
Very interesting. I just looked for Burn FST racquets because it was always mysterious to me how a RA70+ racquet can be quite comfortable which was the case with the Burn FST series.
WilsonBurn FST 9912672324
WilsonBurn FST 99S13174317
RA like Pure Drive and VF like Phantom/Clash. Should be a good recipe but nobody liked these raquets.
 

Trinity110

Semi-Pro
Is there a way we can find out what our older (20+ years) racquets' VFs are? I suppose I mean a document somewhere, as I doubt we can whip up a test in the kitchen!
 

PistolPete23

Hall of Fame
Is there a way we can find out what our older (20+ years) racquets' VFs are? I suppose I mean a document somewhere, as I doubt we can whip up a test in the kitchen!

A while ago, I created a thread to discuss how to measure VF of a tennis racquet at home. I and another forum member (don't remember who, but most credit goes to him) came up with an inexpensive (< $50 for the whole setup) and effective method. The thread got deleted, no idea why. I've thought about making a video guide on YT.
 
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PistolPete23

Hall of Fame
Very interesting. I just looked for Burn FST racquets because it was always mysterious to me how a RA70+ racquet can be quite comfortable which was the case with the Burn FST series.
WilsonBurn FST 9912672324
WilsonBurn FST 99S13174317
RA like Pure Drive and VF like Phantom/Clash. Should be a good recipe but nobody liked these raquets.

Something funky going on with that racquet for sure. I think it might be the most extreme combination of high RA and low frequency.
 

ey039524

Hall of Fame
I did wonder this myself, I have a Clash 98v1, and as much as many are not a fan of the soft touch finish, I do wonder if that was an intentional choice by Wilson to keep the stiffness and/or vibrations down.
I sanded off the bright red/orange on one of my v1 clashes. I didn't notice a difference between that one and my other when playing. It would be interesting to have measured them both.
 

Tao69

Semi-Pro
Very interesting. I just looked for Burn FST racquets because it was always mysterious to me how a RA70+ racquet can be quite comfortable which was the case with the Burn FST series.
WilsonBurn FST 9912672324
WilsonBurn FST 99S13174317
RA like Pure Drive and VF like Phantom/Clash. Should be a good recipe but nobody liked these raquets.
I’ve got two Burn FSTs, they got thrown in with my used stringing machine, they’re heavily used (exposed graphite). I’ve never played them due to the stiffness, might give them a go.
 

Tao69

Semi-Pro
This certainly would explain Babolat's reputation. Despite having highish RA's, they have super high VF's.
Does the plane of vibration come into it?

My thinking is RA is usually measured perpendicular to the racquet face, but Wilson has introduced models which feature flexibility in the same plane as the racquet face. I guess my thinking is your technique is going to play a part in how much any given racquets VF is going to bother you.
 

veelium

Hall of Fame
Does the plane of vibration come into it?

My thinking is RA is usually measured perpendicular to the racquet face, but Wilson has introduced models which feature flexibility in the same plane as the racquet face. I guess my thinking is your technique is going to play a part in how much any given racquets VF is going to bother you.
Babolat RDC measures like this
 

PistolPete23

Hall of Fame
Wilson has introduced models which feature flexibility in the same plane as the racquet face.

I recently learned that Wilson's Stablefeel tech is a design to slightly stiffen all three main modes of bending - normal (perpendicular to racquet face), lateral (parallel with racquet face), and torsional (twisting stiffness). They're measuring all three modes.

With regard to VF, I've tried to measure lateral bending vibration by applying a tapping load accordingly. I think in most cases the VF is slightly higher than when I apply a normal load. I haven't tried it with the Shift.
 

Tao69

Semi-Pro
So I strung up one of the Burn FSTs I have with MSV Focus Hex Soft at 50lbs, had a hit for about 15 mins. It did feel a little muted, but the stiffness still bothered my arm. I would say that there's a limit to which a lower vibration frequency can negate how much a stiff frame aggravates your ligaments and tendons. Can't escape the laws of physics, so if the racquet has less give than your ligaments and tendons, then a low vibration frequency isn't going to matter.
 

ChanterRacquet

Professional
Or the reported vibration frequency is wrong. Science requires reproducibility of measurements.

In reality, the only frequency that’s being reported is the lowest. There are higher frequencies of the frame. The waveform may also be a contributing factor, it’s not just sine waves. So there’s A LOT of unexplored territory, and it will likely remain so because it’s easy enough to demo a racquet.
 
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