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  1. jackocleebrown

    KEF LS60 Wireless Just Announced

    Hi @Mnyb, you originally tagged me for a reply, but when I came to answer I saw that @AOR beat me to it. @AOR is one of our very talented KEF engineering team and nobody knows the way LS60 perform better because AOR did the DSP tuning .
  2. jackocleebrown

    Kef LS60 wireless review by ErinsAudioCorner

    Thanks for the suggestion. I agree it's something we can improve. Our spec sheet max SPL figure is based on 1m 1speaker instantaneous max peak SPL on pink noise. I think that what you suggest is better. A couple of extra notes. On active speakers we do as much limiting as possible with average...
  3. jackocleebrown

    Kef LS60 wireless review by ErinsAudioCorner

    What you see here is thermal protection kicking in on the tweeter. This occurs because a test sweep has extremely high average spectrum at high frequencies. On real music this isn't the case and this protection will almost never be triggered.
  4. jackocleebrown

    Speaker Break-In and Environmental Measurements

    Hi @MAB, I really admire the thoroughness of your study. My experience is a bit different. Only today we have a driver in development where we are discussing Fs shift after production. Using this prototype as an example, the Fs directly after assembly was 57Hz and after sweeping in free air at...
  5. jackocleebrown

    Which way is up? (Which way does a loudspeaker driver move?)

    Shameless plug for this thread which answers some of the questions you pose https://www.audiosciencereview.com/forum/index.php?threads/how-does-a-loudspeaker-cone-generate-acoustical-pressure.48261/
  6. jackocleebrown

    KEF R3 Meta - Review & Measurements by Erin

    It's unfortunate that I can't post the Klippel paper. Anyhow, in the slides you can clearly see the "break-in" period marked on the graphs and distinct from the fatigue behaviour. In the paper Klippel defines this non-reversible change as "Initial exposure to mechanical load opens some bonded...
  7. jackocleebrown

    KEF R3 Meta - Review & Measurements by Erin

    Hi Guys, Driver suspension break-in is a well known effect. For example, please see this paper from Klippel on the topic. https://www.aes.org/e-lib/browse.cfm?elib=16000 You can also find some slides from the paper here...
  8. jackocleebrown

    Audio Engineering Society 2023 Conference

    I'm involved with two papers on the program. @amirm, one is in the same session as yours and I look forward to meeting you in person. https://aesny23.sched.com/event/1SsKE/paper-presentation-iterative-metric-based-waveguide-optimisation...
  9. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    Most trained acousticians would have studied radiation from compact sources into free-space at some point, but it's often done in a fairly abstract way using complex numbers. Mostly you find that velocity sources are used during teaching and there's not much discussion of flatness of transfer...
  10. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    To try and explain the difference between case 2 and case 3 more clearly I've added some additional animations at the end of the first post.
  11. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    The tube is either infinite, or it's extremely long. Because of this, the change in the volume caused by the piston displacing forwards is insignificant. The final volume of the tube is approximately the same as the initial volume of the tube. No air particles have been added or removed from the...
  12. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    I understand the logic, but I'm afraid this isn't correct. For instance, it doesn't explain the difference between case 2 and case 3 (after all, both have the same speed of sound and exactly the same cone motion). The key thing is that in case 2 the velocity of the air particles is parallel to...
  13. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    Hi Jorge, I saw that René replied to you but only just realised there were some other questions you posed too. 1. You're right, I'm simplifying things to an extreme extent by just focusing on the mass. You're quite right to flag the stiffness and damping of the elastic system. I also ignored...
  14. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    Oh, sorry for the misunderstanding. Case 3 says we should try and design a driver where the acceleration of the cone is dictated by the input signal. This sounds complicated but there's a great way to do it. Newton's laws of motion say that if we apply a force to a mass it will accelerate. F=ma...
  15. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    Because they aid understanding of why it can't be cone displacement that determines pressure in case 3. This is a property of the radiation condition. Speakers with horns/waveguides have slightly different behaviour but the same principles apply; the key is how restricted the sound waves are.
  16. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    You're welcome. Yes, the same applies but with the Manger (or a conventional cone in breakup) some parts of the cone are moving forwards while others are moving backwards. Even though it's a much more complicated situation, the acceleration of the different parts of the cone determine the...
  17. jackocleebrown

    How does a loudspeaker cone generate acoustical pressure?

    Introduction This post is inspired the thread "Which way is up", started by @René - Acculution.com, and especially by a comment from @BeerBear. In "Which way is up" René shows that when replaying a sine wave, the maximum pressure coincides with the point when the loudspeaker cone is at maximum...
  18. jackocleebrown

    Which way is up? (Which way does a loudspeaker driver move?)

    You mean in this equation? This equation is in terms of velocity, not displacement. Velocity is the rate of change of displacement, so you can relate the "w" in Rene's equation to the "vp" in this equation like this: Put this into the equation from the paper and you have j is the imaginary...
  19. jackocleebrown

    KEF LS50 Meta Review (Speaker)

    Hi Everyone, Just jumping in here to clarify on this point. The LS50 META carry a 5 year warranty that covers a wide range of problems (more info on our website) but it isn't unconditional and doesn't cover accidental damage from mishandling. However, if you do have a problem our service teams...
  20. jackocleebrown

    KEF R6 meta Measurements and Review

    Hi Abdo123, The midwoofer horizontal spacing causes the horizontal directivity to narrow relatively low in frequency. If you compare the normalised directivity contours provided by @Nuyes you can see that the horizontal -3dB width drops below +-50deg at 300Hz, whereas vertically it's above...
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