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  1. #1
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    Default Tension/Frequency test

    Today I went and bought 2 identical rackets that I'll be using for plastic shuttles, and I thought it was a good idea, since they were both brand new, to do a test and compare the quality/accuracy of a string job done by me and a string job done by a local (general) sports shop.


    Conditions:
    I tried to eliminate the most variables as possible, so this is what we have:
    • Same racket (model)
    • Same condition
    • Same tension (22 x 24)
    • Same string (both strings provided by myself)
    • Same string color
    • Same pattern*
    *I asked for 1 piece - 2 knots, however they started at T8 like in the manufacturer's stringing pattern and I started at T9


    Variables:
    This is what can affect the result is some way
    • Small variation in rackets of the same model (probably negligeable)
    • Small variation in strings of the same model (probably negligeable)
    • The extra/lack of string at the bottom
    • Different stringing machines
    • I tried to have both rackets strung at the same time, however they strung it a little before time, so there is probably a 30 mins -1 hour difference between when both rackets were taken off the machines.

    Assumptions:
    • Their machine is supposed to be calibrated. Mine was calibrated.
    • Stringing was done at around the same temperature

    Details to note:
    • Their machine is a very good electronic machine (Babolat Star iirc)
    • My machine is a decent/good electronic machine with WISE tension head, fixed clamps and 6 supports

    Tests:
    These are the tests I'd like to do with these rackets:
    • Frequency/stringbed tension test
      • Measured with ClearTune, hitting a small blunt object in the middle of the stringbed
    • Playability test
      • Will be tested on court next week
    • Durability test
      • Might not be tested fully as I might cut the strings before they break
    Test results:
    • Frequency tests:
      • 8 hours after stringing:
        • Sports Shop racket: 906.1 Hz
        • My racket: 1056.8 Hz

    Analysis:
    There is a ~15% difference between the frequency of both stringbeds. Using my frequency as a reference and using 22 lbs as a general tension (which sounds about right at 48 Hz/lbs), the stringbed produced by the sports shop would be at around 18.86 lbs.

    This is a huge difference considering that many of the variables were eliminated. While I can't expect the stringbeds to have the same frequency considering that there are variables that can affect it, I think it would be fair to expect a difference of less than 5% (more than 1 lbs in this case, which is big).


    Conclusion
    There are still other things to considerate and test, especially since the stringbeds didn't have time to settle yet. I will be doing more tests during the week and update my data/provide feedback.


    This is not 100% science and there might be things that I forgot to consider. I appreciate any feedback or recommendations that you may have, since I would like to create some kind of discussion around this. Questions are welcome too!

  2. #2
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    Day 2:

    Frequency readings for both rackets (24 hours after stringing):

    • Sports Shop racket: 877 Hz (96.79% of previous reading)
    • My racket: 1034 Hz (97.84% of the previous reading)
    ​It seems that the tension in the sports shop racket decreases faster than the rack I strung.

  3. #3
    Regular Member visor's Avatar
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    One major variable to consider: the stringer... ie his skills in placing the clamps, thing knots, etc.

    The *art* of stringing, if you will.

    That's why I only bring my rackets to stringers that I trust.

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    Actually, this test is mainly to identify the impact of the "Stringer" variable :P AKA the difference between stringing at a general sports shop and a pro shop if all the parameters are the same/alike.

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    Day 3:

    Frequency readings for both rackets (48 hours after stringing):

    • 1-Sports Shop racket: 864.5 Hz (95.41% of previous reading)
    • 2-My racket: 1023 Hz (96.8% of the previous reading)
    The racket #1 is still losing tension faster than #2. The pitch should have stabilized by tomorrow.

    Interesting fact:
    I tested a racket of the same model that I have strung several months ago and played with several times. It was strung at the same tension (iirc, maybe 1 lbs lower) with the same string.

    The pinch is still higher than the racket that was strung just 2 days ago by the sports shop (and is still unused), at 969.3 Hz!

  6. #6
    Regular Member visor's Avatar
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    Conclusion of the story: don't go to a general sports shop. Which one is this btw so that we can avoid it?

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    Regular Member visor's Avatar
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    Speaking of excellent stringers (ie tension retention), I find that Eric of RKEP is the best I've come across. Even with a string like VS850 that is infamous for tension loss, his string jobs retain tension the best. VTZF 24 lbs initial at 1135 Hz dropping to 1070 for a 5.8% loss after 4 months of playing is incredible. Too bad he's so far away in Taiwan.

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    Quote Originally Posted by visor View Post
    Conclusion of the story: don't go to a general sports shop. Which one is this btw so that we can avoid it?
    I'm affraid I can't give a name because it could have legal repercussions and they could easily crush me :P You can however find many bad comments on their stringing/sales services on here.

    I do plan on releasing these results in some way as a mean to warn people that the place where you string your racket does make a difference, so I'm sure this company will hear of it.

    I suspect that the results would be the same with 99% of non specialized stores that sell rackets, so you could probably put any name on there :P.

    As for RKEP, I've never ordered from Eric, however I've been wanting to sell some his stuff for a while. I just need more budget :P The skills of the stringer does make a huge difference on tension retention, the secret seems to reside in the knots and straightening crosses during the stringing process.

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    This is great summary report. it will be nice to compile the frequency results for a list of rackets, with different strings, at different tensions.

    For myself, I always use the frequency to compare the tension of rackets.

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    Quote Originally Posted by dunmaster View Post
    This is great summary report. it will be nice to compile the frequency results for a list of rackets, with different strings, at different tensions.

    For myself, I always use the frequency to compare the tension of rackets.
    It would indeed be very nice to be able to identify what tension one's stringbed is at with the frequency. However, we'd need a lot of data to be able to do so (100s of (common) rackets x 10s of strings), and even then we'd have no way to know if the data is reliable unless multiple people come up with the same result

    There must be some way...

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    Quote Originally Posted by yan.v View Post
    It would indeed be very nice to be able to identify what tension one's stringbed is at with the frequency. However, we'd need a lot of data to be able to do so (100s of (common) rackets x 10s of strings), and even then we'd have no way to know if the data is reliable unless multiple people come up with the same result

    There must be some way...
    Indeed a huge task, and hope there is a way...

  12. #12
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    Stringer's skill is obviously the biggest factor.

    My friend is lazy and usually gets it strung at the courts. If you read some of my threads...you'll know which courts I'm talking about. Anyways...each time he gets it strung...it's way off. Once it was loose and I knew it couldn't be 26lbs. Another time it was tighter than a ... .


    So in conclusion...go with a reputable stringer. Use ClearTune to check the work. See the how much tension is lost in the next couple of days. And re-check to see if the tension stabilize.

    Or do it yourself.

  13. #13
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    Quote Originally Posted by dunmaster View Post
    Indeed a huge task, and hope there is a way...
    Stuff like this...probably best for known stringers (see the guys on the stringing forum) to record the frequency of each string job for each racket. Quite the undertaking though.

  14. #14
    Regular Member gundamzaku's Avatar
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    Quote Originally Posted by yan.v View Post
    Today I went and bought 2 identical rackets that I'll be using for plastic shuttles, and I thought it was a good idea, since they were both brand new, to do a test and compare the quality/accuracy of a string job done by me and a string job done by a local (general) sports shop.




    Conditions:
    I tried to eliminate the most variables as possible, so this is what we have:
    • Same racket (model)
    • Same condition
    • Same tension (22 x 24)
    • Same string (both strings provided by myself)
    • Same string color
    • Same pattern*
    *I asked for 1 piece - 2 knots, however they started at T8 like in the manufacturer's stringing pattern and I started at T9


    Variables:
    This is what can affect the result is some way
    • Small variation in rackets of the same model (probably negligeable)
    • Small variation in strings of the same model (probably negligeable)
    • The extra/lack of string at the bottom
    • Different stringing machines
    • I tried to have both rackets strung at the same time, however they strung it a little before time, so there is probably a 30 mins -1 hour difference between when both rackets were taken off the machines.
    Assumptions:
    • Their machine is supposed to be calibrated. Mine was calibrated.
    • Stringing was done at around the same temperature
    Details to note:
    • Their machine is a very good electronic machine (Babolat Star iirc)
    • My machine is a decent/good electronic machine with WISE tension head, fixed clamps and 6 supports

    Tests:
    These are the tests I'd like to do with these rackets:
    • Frequency/stringbed tension test
      • Measured with ClearTune, hitting a small blunt object in the middle of the stringbed
    • Playability test
      • Will be tested on court next week
    • Durability test
      • Might not be tested fully as I might cut the strings before they break
    Test results:
    • Frequency tests:
      • 8 hours after stringing:
        • Sports Shop racket: 906.1 Hz
        • My racket: 1056.8 Hz

    Analysis:
    There is a ~15% difference between the frequency of both stringbeds. Using my frequency as a reference and using 22 lbs as a general tension (which sounds about right at 48 Hz/lbs), the stringbed produced by the sports shop would be at around 18.86 lbs.

    This is a huge difference considering that many of the variables were eliminated. While I can't expect the stringbeds to have the same frequency considering that there are variables that can affect it, I think it would be fair to expect a difference of less than 5% (more than 1 lbs in this case, which is big).


    Conclusion
    There are still other things to considerate and test, especially since the stringbeds didn't have time to settle yet. I will be doing more tests during the week and update my data/provide feedback.


    This is not 100% science and there might be things that I forgot to consider. I appreciate any feedback or recommendations that you may have, since I would like to create some kind of discussion around this. Questions are welcome too!
    and i thought i was OCD with badminton related stuff. thank you for the very detail description of your experiment. it was an eye opener for me because i always thought to give "unknown" stringers a chance. now i'm thinking that just to make things consistent i'll continue to string my own string cos it's worth the 45min.

  15. #15
    Regular Member gundamzaku's Avatar
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    Quote Originally Posted by CanucksDynasty View Post
    Stringer's skill is obviously the biggest factor.

    My friend is lazy and usually gets it strung at the courts. If you read some of my threads...you'll know which courts I'm talking about. Anyways...each time he gets it strung...it's way off. Once it was loose and I knew it couldn't be 26lbs. Another time it was tighter than a ... .


    So in conclusion...go with a reputable stringer. Use ClearTune to check the work. See the how much tension is lost in the next couple of days. And re-check to see if the tension stabilize.

    Or do it yourself.
    LOL at tighter than a.............sorry it's been a long time since i've been out, that was a great joke!!!

  16. #16
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    After a week and some play time:

    I played with both rackets this week. However, #1 got MUCH less play time. I played #1 about 5-10 minutes because I didn't like the feeling of it (too loose). I played #2 3 times for about 2 hours each time, so 6 hours total.

    Frequency readings for both rackets:

    • 1-Sports Shop racket: 842 Hz (92.93% of previous reading)
    • 2-My racket: 987 Hz (93.4% of the previous reading)
    It's also impossible to produce a lasting ping off #1. The sound ends right after I hit the stringbed.

    Playability test:

    It's no surprise that #1 feels looser, but did it make that much of a difference ? It's just more power right ? NO! I completely hated playing with #1. I felt like I was hitting the shuttles with wet spaghettis. The stringbed had no feeling to it. Smashes felt weak and drops were much higher than usual at the net. After 10 minutes, I couldn't bare the racket anymore and I started using #2. I found my shots back from when I play with feather shuttles, with the usual smashes almost never being returned, because that's what playing with plastic shuttles does :P


    There was a world of difference between both rackets. Just because of the quality of the stringbed ? I think so! However we have to keep in mind that I knew which racket I was using while playing, so it wasn't a blind test (I would have known anyways). That may have had some psychological effects. However, seeing how the difference between both strings is big in frequency and ping duration, I'm confident in saying that most of the difference is due to the string job's quality.


    Durability:

    Well, both strings lasted through the week. Seeing how loose #1 strings are, I can guess that their strings will probably last a lot longer, because looser strings usually do last longer (unless they abused the awl or played with sharp tools around the strings or something). However, I can say that their string will fail the durability test, because I'll have to cut it as I feel that it is unplayable for me :P


    General conclusion:

    Well, we already knew that, but only have your rackets strung by people you trust. Find a pro shop instead of general sports shop. It's usually cheaper and the quality of the string job will be MUCH better. They can also give you better advices on what strings and tensions you should use.

    I already knew the conclusion before doing this. However I wanted to put it in numbers for everyone (myself included) to see that the difference is real and big. Not everyone has 20$ to waste like I do, but I encourage people to do experiments like this for tension. This will not only inform people, but we may be able to find a solid corelation between the tension of a string job and the pitch it produces.

    Lastly, if you have any questions/comments, please do reply and I'll happily answer back!

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    I'd also like to add that this was for a pretty low tension range (22x24 lbs). Chances are that the difference would be even bigger (not just in lbs, but in %) for high tensions.

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