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Headphones sensitivity, impedance, required V/I/P, amplifier gain

post #1 of 58
Thread Starter 

The following table is based on measurements, not manufacturer specs.

 

Target SPL is 110 dB SPL.

The source is assumed to output 2 V. The amp is assumed to be a voltage source (0 ohm output impedance).

Voltage, current, power are RMS figures.

 

What do the columns mean?

S@1V is the sensitivity with 1 V, 500 Hz sine wave input in dB SPL.

Z is the impedance at 500 Hz in Ω.

Voltage is the required voltage to reach the target SPL.

Current is the required current to reach the target SPL in milliamperes.

Power is the required power to reach the target SPL in milliwatts.

Gain is the gain the headphone amplifier theoretically needs to reach the target SPL without excess gain. If needed you can add a few dB excess gain (suggestion: 3 to 9 dB).

Notes:

  • 1 kHz: the measurement was done at 1 kHz instead of 500 Hz
  • specs: based on specifications provided by the manufacturer, not independent measurements
  • nc: noise canceling enabled

 

 

There is no guarantee that the data is 100% correct. The sensitivity of some headphones can vary as much as +/- 3 dB (some manufacturers even specify this explicitly).

 

 

Manufacturer Model S@1V [dB SPL] Z [Ω] Voltage [V] Current [mA] Power [mW] Gain [dB] Notes
AKG K240 Studio 103 64 2.239 34.98 78.311 1  
AKG K271 MK II 106 65 1.585 24.383 38.644 -2  
AKG K272 HD 110 65 1 15.385 15.385 -6  
AKG K550 115 35 0.562 16.067 9.035 -11  
AKG K601 99 131 3.548 27.085 96.101 5  
AKG K701 105 65 1.778 27.358 48.65 -1  
Audeze LCD-2 108 45 1.259 27.976 35.22 -4  
Audeze LCD-3 102 48 2.512 52.331 131.449 2  
Audio Technica ATH-AD700 113 35 0.708 20.227 14.32 -9  
Audio Technica ATH-AD900 114 37 0.631 17.053 10.76 -10  
Audio Technica ATH-AD900X 114 38 0.631 16.604 10.477 -10 1kHz, specs
Audio Technica ATH-ANC7B 118 305 0.398 1.305 0.52 -14 nc
Audio Technica ATH-ANC9 109 100 1.122 11.22 12.589 -5 nc
Audio Technica ATH-M50 115 38 0.562 14.798 8.322 -11  
Beats by Dr. Dre  Pro 117 18 0.447 24.816 11.085 -13  
Beats by Dr. Dre  Studio 121 216 0.282 1.305 0.368 -17 nc
Beyerdynamic Custom One Pro 116 18 0.501 27.844 13.955 -12  
Beyerdynamic DT770 Pro 98 251 3.981 15.861 63.143 6 1kHz
Beyerdynamic DT770-32 111 32 0.891 27.852 24.823 -7  
Beyerdynamic DT770-600 100 557 3.162 5.677 17.953 4  
Beyerdynamic T1 99 750 3.548 4.731 16.786 5  
Beyerdynamic T5p 116 41 0.501 12.224 6.127 -12  
Beyerdynamic T70 110 380 1 2.632 2.632 -6  
Beyerdynamic T90 102 308 2.512 8.155 20.486 2  
Bose AE2 112 36 0.794 22.065 17.527 -8  
Bose QC15 113 4800 0.708 0.147 0.104 -9 nc
Bowers & Wilkins P5 117 27 0.447 16.544 7.39 -13  
Denon AD-D2000 115 25 0.562 22.494 12.649 -11  
Denon AH-D1001 112 31 0.794 25.623 20.353 -8  
Denon AH-D7000 114 25 0.631 25.238 15.924 -10  
Denon AH-D7100 108 30 1.259 41.964 52.83 -4  
Fischer Audio FA-003 117 75 0.447 5.956 2.66 -13  
Fostex T50RP 107 54 1.413 26.158 36.949 -3  
Fostex T7 113 80 0.708 8.849 6.265 -9  
Fostex TH900 108 25 1.259 50.357 63.396 -4  
Grado Labs SR60i to 325i 111 34 0.891 26.213 23.363 -7  
Hifiman HE-4 90 63 10 158.73 1587.302 14  
Hifiman HE-500 102 34 2.512 73.879 185.576 2  
Hifiman HE-6 89 43 11.22 260.935 2927.734 15  
Hifiman Re0 118 60 0.398 6.635 2.641 -14  
KRK Systems KNS6400 110 34 1 29.412 29.412 -6  
KRK Systems KNS8400 106 35 1.585 45.283 71.768 -2  
Sennheiser Amperior 113 22 0.708 32.179 22.781 -9  
Sennheiser CX880 120 34 0.316 9.301 2.941 -16  
Sennheiser HD202 119 34 0.355 10.436 3.703 -15  
Sennheiser HD280 Pro 114 73 0.631 8.643 5.454 -10  
Sennheiser HD555/595 114 72 0.631 8.763 5.529 -10  
Sennheiser HD558/598 112 70 0.794 11.348 9.014 -8  
Sennheiser HD600 105 322 1.778 5.523 9.821 -1  
Sennheiser HD650 104 333 1.995 5.992 11.955 0  
Sennheiser HD700 105 199 1.778 8.936 15.891 -1  
Sennheiser HD800 103 430 2.239 5.206 11.656 1  
Sennheiser IE800 125 18 0.178 9.879 1.757 -21  
Sennheiser PX100 II 114 34 0.631 18.558 11.709 -10  
Sennheiser PX200 II 115 38 0.562 14.798 8.322 -11 1kHz
Shure SE215 126 18 0.158 8.805 1.395 -22  
Shure SE535 133 36 0.071 1.967 0.139 -29  
Shure SRH1440 107 38 1.413 37.172 52.507 -3  
Shure SRH1840 102 66 2.512 38.059 95.6 2  
Shure SRH440 116 41 0.501 12.224 6.127 -12  
Shure SRH750 113 39 0.708 18.152 12.851 -9  
Shure SRH840 116 44 0.501 11.391 5.709 -12  
Shure SRH940 113 40 0.708 17.699 12.53 -9  
Skullcandy Aviator 118 36 0.398 11.059 4.402 -14  
Skullcandy Crusher 114 32 0.631 19.717 12.441 -10 1kHz, specs
Skullcandy Mix Master 119 20 0.355 17.741 6.295 -15  
Sol Republic Tracks 118 60 0.398 6.635 2.641 -14 1kHz
Somic MH463 106 45 1.585 35.22 55.82 -2 1kHz, specs
Sony MDR-MA900 111 15 0.891 59.417 52.955 -7  
Sony MDR-XB1000 115 27 0.562 20.827 11.712 -11  
Sony MDR-XB500 123 43 0.224 5.206 1.166 -19  
Sony MDR-XB700 115 28 0.562 20.084 11.294 -11  
Superlux HD668b 108 61 1.259 20.638 25.982 -4  
Superlux HD669 110 62 1 16.129 16.129 -6  
Takstar HI2050 104 60 1.995 33.254 66.351 0 1kHz, specs
Ultrasone Edition 8 115 34 0.562 16.539 9.301 -11  
Ultrasone HFI580 115 36 0.562 15.621 8.784 -11  
Ultrasone HFI680 115 75 0.562 7.498 4.216 -11  
Ultrasone HFI780 116 40 0.501 12.53 6.28 -12  
Ultrasone Pro550 117 65 0.447 6.872 3.07 -13  
Ultrasone PRO750 114 41 0.631 15.389 9.71 -10  
Ultrasone PRO900 108 43 1.259 29.277 36.858 -4  
V-Moda Crossfade M100 115 36 0.562 15.621 8.784 -11  
Yamaha PRO 300 116 58 0.501 8.641 4.331 -12  

 

 

 

Some have raised concerns with 110 dB SPL being too loud. Well, that is just the absolute highest SPL you can reach with a full-scale 500 Hz tone and the volume set to max.

Music has a higher crest factor than sine tones, which means that the RMS value will be much lower.

 

The following graphic shows a volume control with a 15A taper pot as found in many heapdhone amps. Ideal range should be somewhere between 10 and 2 o'clock.

The inner labels show the attenuation of the pot at each full hour. So 110 becomes 95 dB SPL at 12 o'clock.

The outer blue/red labels show the overall perceived SPL of an uncompressed classical track and a heavily compressed metal track respectively. Loudness was calculated using an EBU R128 compliant scanner.

 

Obviously, you can really hurt your hearing if you listen to highly compressed music and turn up the volume. With less compressed music overall levels will be a lower but there can still be very loud passages or short peaks in SPL.

 

So turn the volume down - better be safe than sorry. Don't rely on calculations only. Use a sound level meter.

 

 

 

 

 

Please let me know if you find that some values are completely off or want some headphones added.


Edited by xnor - 9/22/13 at 6:18am
post #2 of 58

Thanks for the great work. Could you also include these models from beyerdynamic? I've provided the links below so you won't have to go searching for it.

 

T 70 - http://europe.beyerdynamic.com/shop/hah/headphones-and-headsets/at-home/music-pleasure/t-70.html

T1    - http://europe.beyerdynamic.com/shop/hah/headphones-and-headsets/at-home/music-pleasure/t-1.html

T5p  - http://europe.beyerdynamic.com/shop/hah/headphones-and-headsets/at-home/music-pleasure/t-5-p.html

T 90 - http://europe.beyerdynamic.com/shop/hah/headphones-and-headsets/at-home/music-pleasure/t-90.html

 

Thanks in advance.

post #3 of 58
Audio Technica ATH-AD700
Sony MDR-MA900

For fun, you could do a "marketing headphone" (Beats, SOL Republic, etc.).
post #4 of 58
Quote:
The source is assumed to output 2 V.

 

RMS I presume?

 

se

post #5 of 58
Thread Starter 

Yes, 2 Vrms.

 

Obviously the target SPL with that gain is only reached with a full-scale 500 Hz tone. But depending on the frequency response the headphone will produce a couple dB more at other frequencies.


Edited by xnor - 6/15/13 at 7:00pm
post #6 of 58
Thread Starter 

Added some more headphones. SOL Republic Tracks has a terrible dip at 400 Hz, which is the only headphone so far that has such a problem near 500 Hz, so I chose 1 kHz instead.

post #7 of 58

Thanks for the added information. I have a question regarding how the calculations work. Take for instance the Beyerdynamic T1, which is rated at 600 ohms. Why did you base the calculations on a 730 ohm impedance?

post #8 of 58

I might be wrong but... looks like the value in mA are based on the RMS voltage. They should be based on the peak voltage.

post #9 of 58
Thread Starter 

@Greenleaf7: That's because manufacturers provide nominal impedance in the specs. That number is just an approximation anyway.

 

The measurements of T1's I've seen never reach 600 Ohm. The minimum at 2 to 4 kHz is somewhere around 630 Ohm. It has a very broad impedance peak at about 80 Hz, so the impedance at 500 Hz is higher.

post #10 of 58
Thread Starter 

@00949: Numbers are based on RMS power. P = Vrms^2 / R = Vrms * Irms.

post #11 of 58

Irms is almost never used, datasheets and specification sheets usually use Ipeak and that's what is assumed when giving values in mA. If you use it, you should specify it (as you did for V).

post #12 of 58
Thread Starter 

Added some more headphones, added manufacturer column.

 

Interestingly, with just 3 dB excess gain more than 70% of the headphones listed require no more than unity gain (0 dB).

 

Even with a 1 V source like an iPod the SE535 would be fine with 20 to 14 dB of attenuation due to their high efficiency.

 

And to the DIYers and reviewers: If you have a DAP or amp that is free of hiss with the SE535 it is very likely going to be fine with any other earphone or headphone.


Edited by xnor - 6/16/13 at 2:55pm
post #13 of 58
Thread Starter 

As we know, ideally the volume control pot should spend most of its time between 10 and 2 o'clock.

 

Assuming the pot ranges from 7:00 to 17:00 and has a 15A resistance taper we get an attenuation of about 22 to 9 dB at those positions.

With the 110 dB SPL target and no excess gain that results in 88 dB to 101 dB SPL with the 500 Hz full-scale tone.

 

Using an EBU R-128 loudness scanner I looked at some completely uncompressed classical / hypercompressed metal tracks.

The perceived overall loudness of those tracks, which may have soft and loud passages, is up to 20 dB / 6 dB quieter compared to a full-scale 500 Hz tone.

 

 

What does this all mean?

 

Example:

110 dB SPL target with a 2 V source as used in #1

Sennheiser HD800 => amp with 0 dB gain

no excess gain

 

1) volume control at 10 o'clock

perceived overall loudness:

a) classical recording: 68 dB SPL

b) compressed track: 82 dB SPL

 

2) volume control at 2 o'clock

perceived overall loudness:

a) classical recording: 81 dB SPL

b) compressed track: 95 dB SPL

 

3) volume control at max

perceived overall loudness:

a) classical recording: 90 dB SPL

b) compressed track: 104 dB SPL

 

 

(EBU R128 uses Loudness Units instead of dB but I used plain old decibels to avoid [even more] confusion.)

 

 

edit: will have to do some measurements to see how big the error is using a 500 Hz tone as reference


Edited by xnor - 6/16/13 at 5:24pm
post #14 of 58

Couple quick thoughts

 

1) First and foremost, thank you for this reference! 

beerchug.gif

This is extremely helpful (see below) and *should* be linked to very very often in the future.

 

2) If you are from an english-speaking country:

sed '/[0-9]\,/s/\,/./g'

 I spent 20 minutes trying to figure out how the heck the HE-6s needed 3 kW to reach 110 dB!!!

I knew they were inefficient, but I didn't think they were that bad! wink_face.gif

 

4) there is no number 3.

 

5) This data is super helpful for guiding people who are considering new headphones or amplifiers and are unsure whether or not their amp-cans combination will work. If they have cans A and are considering cans B, they can compare the sensitivities, current requirements, and voltage requirements and weigh the differences against their amp's capability to source that current and voltage. 

 

6) I think 110 dB is a little bit high for a reference loudness, especially since 90dB is the typical threshold for hearing damage. Because this data is especially useful for guiding newer enthusiast in their search for headphone nirvana, I think it's a little dangerous to give the impression that they should be listening at 110dB SPL with any regularity. Perhaps you could put a disclaimer in the original post warning against prolonged exposure to  >= 110 dB. Of course I'm just picking nits here.

 

 

+1 rep

 

Cheers!


Edited by ab initio - 6/17/13 at 12:02am
post #15 of 58
Quote:
Originally Posted by xnor View Post

As we know, ideally the volume control pot should spend most of its time between 10 and 2 o'clock.

 

why? I never heard of this ideal placement for a volume pot

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