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Topic: Anyone tried the newer noise cancelling headphones? QC35, MDR1000X. (Read 10523 times) previous topic - next topic
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Re: Anyone tried the newer noise cancelling headphones? QC35, MDR1000X.

Reply #25 –
Quote from: klaberte on
Quote from: mitchco on
Please see: http://www.innerfidelity.com/images/BoseQuietComfort20.pdf Note the Isolation chart on the right... and the broadband attenuation spec at the bottom.

OK, but that doesn't answer the question definitively.  Claiming broadband isolation of 26 dB for a large frequency range, when the "isolation" graph varies from 20-30 dB...  Perhaps there are some notes that provide details on what these graphs mean.  To me, it doesn't clearly show whether ANC is operating at higher frequencies.  My proposed test might shed some information.

(unless mitchco is the writer of those blogs he posted...)

Here is the matching graph with ANC turned off:
http://www.innerfidelity.com/images/BoseQuietComfort20Passive.pdf

Those are from InnerFidelity:
http://www.innerfidelity.com/content/travelers-sanctuary-bose-quiet-comfort-20-noise-canceling-earphone-measurements

Tyll measures noise cancelling headphones both turned on and off. Just open the PDF's for "active" and "passive" and flip between them to see exactly what the ANC is doing. For the QC20, it looks like the ANC works up to about 1.5kHz, and above that you get better isolation in "passive" mode (not sure why passive is better?)

Re: Anyone tried the newer noise cancelling headphones? QC35, MDR1000X.

Reply #26 –
Quote from: Ed Seedhouse on
Quote from: klaberte on
So, we will put Ed into the "no" column, although, again, mass has nothing to do with this limitation.

I will agree that it probably has very little to do with it, but it must at least theoretically have some effect, possibly at such high frequencies as to make no difference.  Anything with mass cannot be accelerated instantly.  It will take some (very slight) for the microphone diaphragm  to accelerate, some time to process the resulting signal (much less time, though), and some (slight) time to accelerate the speaker diaphragm.

I don't do math well enough to calculate what effect this will have, though intuitively it seems likely to be very small.


Perhaps, but missing the point.  Instantaneous movement is not a requisite property for audio headphones.

Yes, F (t)=MA(t), meaning that for some object with mass (M), you need a requisite time sequence of force F(t) to move it in some specific pattern (characterized by accelerations A(t)).  The question is: does a set of headphones have the requisite force to move its speaker in some arbitrary pattern, given that the pattern is limited to some set of frequencies, nominally those frequencies perceptible by human hearing. 

The answer to that is found in the spec sheet.  If the headphones can render arbitrary signals composed of that set of frequencies, then the headphones have the requisite force.  That is how they are designed.

If you are going to continue to argue this point, please share some references.

Re: Anyone tried the newer noise cancelling headphones? QC35, MDR1000X.

Reply #27 –
Quote from: eric.w on
(not sure why passive is better?)

I'm not sure either, as I didn't find his test procedure on isolation measurements: http://www.innerfidelity.com/headphone-measurement-procedures

Reading the plots literally suggests that in ANC mode, the headphones are injecting wideband noise, i.e. what is being blocked passively is getting re-injected by the headphone speakers.  Not sure if that is an artifact of the ANC system or the measurement procedure...