I am with Maverickronin on this one.The way I see it (and was often told I was wrong) if a driver swings out, this could be compensated by applying the 'opposite signals' (motion feedback/noise cancelling principle but done differently)This would have to be done at all the specific frequencies or in very narrow bands, when non-active feedback is used and that would amount to a lot of computive power to modify the incoming signal to the 'needed one'.Also each headphone would have to be compensated individually (look at the DT1350 choclats), not to mention diafragms changing properties over time or temperature change would do to the original compensation.Another thing..... will the headphone actually sound ideal as well with all these 'modifications' of the original signal ?Test signals perhaps.. music unsure.Strange plot it cannot be just FR compensation but time domain must be addressed as well (for the ringing) otherwise a simple EQ would have been enough and it isn't for the 'effen ringin' IMO.If it were that simple to create the perfect headphone there would have been handy sellers that were already selling headphones with built-in active compensation for large sums of money as they would be very easy to make and sound 'perfect'.No such thing yet.
3. What did "It's not perfect but that's not surprising considering I used the raw data" mean?3) It means that I didn't do any averages over positional changes. I didn't re-measure the headphones with the inverse filter applied (you could do this multiple times trying to improve the filter each time). Also there was no smoothing, so narrow 20 dB dips would be narrow 20 dB peaks in the inverse filter which could cause problems if you used that filter for listening.Still, overall you can generate filters to flatten the FR which will also improve the impulse response, provided they're mostly min phase (so no crazy multi-way crossover stuff) . You can also do it by hand, but it's a lot more work if you have to do it for multiple headphones over and over again.
I think xnor's plot is a bit idealized as there would be positional variations and distortion that would not result in such an ideal response. The purpose was to show that equalization can indeed make corrections to the CSD response.Acoustic equalization through damping offers similar benefits (or if wrongly applied... issues):TR50PParadox:http://www.changstar.com/index.php/topic,41.0.htmlhttp://www.changstar.com/index.php/topic,17.0.htmlKoda:http://www.changstar.com/index.php/topic,208.msg2304/topicseen.html#newI couldn't find measurements of the stock YH-3s here at effin' ringin', but here are the results after some well thought modifications:http://www.changstar.com/index.php/topic,388.msg6294.html#msg6294
Quote from: ultrabike on September 10, 2012, 03:27:55 AMI think xnor's plot is a bit idealized as there would be positional variations and distortion that would not result in such an ideal response. The purpose was to show that equalization can indeed make corrections to the CSD response.Acoustic equalization through damping offers similar benefits (or if wrongly applied... issues):TR50PParadox:http://www.changstar.com/index.php/topic,41.0.htmlhttp://www.changstar.com/index.php/topic,17.0.htmlKoda:http://www.changstar.com/index.php/topic,208.msg2304/topicseen.html#newI couldn't find measurements of the stock YH-3s here at effin' ringin', but here are the results after some well thought modifications:http://www.changstar.com/index.php/topic,388.msg6294.html#msg6294This is an old post but I just saw it...Damping doesn't just change the FR though. It changes how the driver operates because of putting different "pressures" on the movement of the diaphragm. At least IMO/E. And it definitely also actually eliminates resonance separate from FR. You could have a lot of different sounding T50rp mods with wildly different FR but all very clean. With the riht mods that is.
Since I have never tinkered with headphones in this particular way I wonder how they sound after the 'near ideal' response is created ?I mean polishing a will still be a polished Can you get a HD201 to sound like the SR009 or will it still sound like a HD201 but 'imporoved' ?I have tried to 'speed up' severely rolled off HP's by EQ but do not get the desired results as the membrane simply cannot create the needed movement.Similar to turning up the bottom end on a bass-shy HP, this too will never give a good bass reproduction.Starting base would have to be a very good headphone that only needs a few nudges.my personal FR is limited to about 16kHz, though the 16.265kHz I can still detect (but not as loud as when I was young)Although some claim related harmonics above the audible range contribute to the overall SQ I feel that 20kHz (-0.1dB) is sufficient.As long as I can get risetimes of the membrane fast enough to follow those that exist in music signals I can't complain.Usually the fast moving amplitudes are very low in amplitude so no full range squarewave response is needed (for me)
In regards to the interpretation of the phase response, I have actually also looked into this as part of my previous investigation but decided not to post the results because it wasn't too clear. You have to "unwrap" the phase response of the headphone to check if it has minimum phase characteristics. You also obviously need to remove the "propagation delay" of the original headphone IR (e.g. shift the IR so the peak pulse occurs at the beginning of the time window) as this adds up to the unwrapped phase response. For instance, a pure dirac has no phase change while the unwrapped phase of a time delayed (t_0) pure dirac unwraps at the rate of exp(-i 2*pi*f*t_0) or some like that. Once you've removed the propagative phase component of the headphone response, you may be able to see how much the headphone deviates from minimum phase characteristics (the minimum phase version naturally has no "propagation phase" component, e.g. the peak occurs at t=0). I haven't bothered going there yet and probable the bode plot approach is much more convenient...
