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Approximating Headphone Volume Output (dB)

Discussion in 'Sound Science' started by tinyman392, Dec 21, 2011.
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  1. Jensigner
    Thanks for the useful comments and reference. I'll check it out.
    dBL as in:
    "Unweighted sound pressure level is called "linear sound pressure level" and is often written as dBL or just L"  (wiki info).
    I didn't measure the rms voltage with a voltmeter. I wrote an application which uses a high-end sound card and samples at 24bit/96kHz and computes the real rms voltage and calibrated with a precision voltage source. It seems to be accurate (~ 10%) up to 20kHz.
  2. xnor
    Oh okay, so the Vrms figure is more or less accurate, but that doesn't necessarily translate well to perceived loudness or measured weighted SPL. There's also still the problem with headphone frequency response.
  3. Jensigner
    Yes I agree with that. I think the only useful comparison (and it is only at one frequenc so is really of limited practical use and give a very rough idea of overall "loudness") is the spec'd dbSPL at 1 kHz for either 1 mW or 1Vrms. Being a Physicist, I like to "assume it's a sphere" :)  
  4. AbsoluteZero
    Interested in these things but still confused.
    First, I am feeding my music through an Apex Glacier which says the following in Maximum Output : 3.3V RMS into 15 Ohms; 2.14V RMS into 33 Ohms. Anyone care to decipher what that means and also which numbers can I extract as information?
    The Apex Glacier manual also stated that each step on the wheel is exactly 2 dB so is it correct if I assume this to be linear instead of logarithmic in the calculation? (there are 32 steps, I listen at around 10 to 16 steps)
    Also I have a headphone with 102 dB SPL/mW, 60 ohms impedance if anyone would kindly help me find my loudness number [​IMG].
    Thanks guys!
  5. xnor
    Specs on ttvj website say:
    Maximum output: >2.6V RMS into 150Ω; >1.7V RMS into 32Ω
    Maximum gain:  0dB, 10dB, or 20dB, ±<0.5dB
    Maximum input level: 2V RMS
    So with a 2V source you don't need any gain (0 dB) in order to reach (close to) max output into 60 ohms.
    102 dB SPL/mW = 114 dB SPL/V
    so at full volume: 120 dB SPL (+6 dB because of 2V source)
    at step 29: 114 dB SPL (120 - 3*2)
    at step 16: 88 dB SPL (120 - 16*2)
    at step 10: 76 dB SPL (120 - 22*2)
    This is with a full-scale 1 kHz tone. Real music will have a lower average SPL, but can have short term peaks reaching close to those numbers.
  6. Jensigner
    Assuming roughly that at 60 ohm load, we have ~ max output voltage of 3.3Vrms, then here are some results:
    A 2 dB step per volume increment means the output voltage factor is reduced by a FACTOR of 0.794  (or the POWER is reduced by a factor of 0.631).  So, these are the output voltages (pure sine wave) and assuming Z(1 kHz) = 60ohm with 102 dBSPL/mw or 114 dBSPL/1Vrms @ 1 kHz:
      10 setting:  21 mVrms      (22 dB below max setting)  giving  80 dBSPL at 1 kHz
      16 setting:  82 mVrms      (16 dB below max setting)   giving 92 dBSPL at 1 kHz
    Result using this calculator:   http://www.jensign.com/S4/calc.html
  7. AbsoluteZero
    Thanks guys for the calculations, I am starting to understand these things currently.
    Now I can calculate for my other headphonesin my inventory, cheers!
  8. Jensigner
    Glad to help out in some way. Related to audio level, I recently have built some basic gear to verify audio specs (typically "A-Weighted in a 20 kHz BW" noise and S/N) of some audio equipment I have. This is a very interesting area and opinions are strong (as you can see from the references I include):  http://www.jensign.com/AWeight/
  9. luisdent
    I haven't read this whole thread, but I see a potential flaw in this calculation.  If you use all the variable and figure out your decibel level that you are supposedly listening to, how do you determine the level of the music as well?  In other words, the result of this calculation tells you the potential max db level you're listening to, but some songs are quieter than others.  If you change nothing with the volume, but switch to a quieter track this calculation won't reflect that (unless I missed something).  So if track two is 20db quieter than track one, how do you know how loud either track is?  Is this formula based on listening to a song that is a wall of 100% db of noise?  Just curious...
  10. xnor
    His old calculations were completely wrong. It's best to ignore them.
  11. luisdent
    Is there any way to know your db without a measurement device?
  12. xnor
  13. Farhan Zulkipli
    Hello Tinyman. I'm 15 years old and not experienced in these things. Be nice to noobs hey :) Anyway, I've been having this tinnitus for the past few days and have not managed to go to school yesterday and today. I use a First Gen FIIO X3 and I listen to it on around 60/120 volume although i go higher on my computer do to it being to softer. I was wondering, what is the max volume it can go to with a Brainwavs HM5. specs for both devices are here
    Brainwavs HM5- https://www.amazon.com/Brainwavz-HM5-Studio-Monitor-Headphones/dp/B006MA9XXM
    Fiio x3 First Gen - http://www.fiio.net/en/products/41/comparisons and http://ohm-image.net/opinion/audiophile/sound-quality-review-fiio-x3
    Please oh please help me. I am so paranoid right now.
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