dB per milliWHAT? Efficiency vs. Sensitivity vs. "How loud do they really go?"
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j-curve

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Headphone efficiency has been quoted in dB/mW ever since headphones were invented, hasn't it? Probably a good idea too, because it was fairly easy to calculate how much power you were going to need. It also allowed manufacturers to compete on a meaningful basis, improving efficiency with better designs, stronger magnets, lighter diaphragms, etc.

Recently there has been a move by Sennheiser and AKG to abandon the traditional measurement and quote sensitivity in dB/V instead. This could be an even better idea, because amplifiers are primarily voltage devices, and now we have a number which doesn't require a tertiary qualification in electronics to figure out how loud our headphones will sound. The downside is that if manufacturers compete on dB/V sensitivity, there will be an inevitable trend to lower impedance headphones, and we'll hear background hiss every time we plug into any source.

In the meantime, we have two different standards for specifying loudness, neither of which is definitive because it can still depend on the output impedance of the amplifier, and whether or not the headphones you're comparing will be plugged into the source at the same time or one after the other.

What started as a list of a handful of 'phones has become a database which I'd like to share with fellow Head-Fiers. These are two Excel files which have been zipped to meet the 25kB size limit on attachments. Both contain macros so I've scanned them at virusscan.jotti.org before posting.

One is the database. The other is a utility for calculating maximum SPL for given phones and amplifier.

Please let me know of any significant omissions or errors.

MD5 Checksum info:-
Sensitivity.zip 9c171822e593bbcbe6aaf338a6b9cb8b
Sensitivity.xls 3fbec765547cf9a88a8eb126c791d305
MaxSPL.zip a7e01b48456bfed455f8e0f67e13505b
MaxSPL.xls a4da9074675e3bf697cd264921b74697

Edit: Replaced Senstivity.zip, incorporating changes contributed by Iron_Dreamer and sgrossklass, and adding Sony V6 & V9.
 
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post-1988121
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hugz

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bump for useful post
 
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post-1988278
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Iron_Dreamer

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I'm not too much of a fan of using dB/V, I prefer dB/mW as it is analogous to the dB/W/M used with regards to speakers. I think Sennheiser and AKG are using it, because it makes their headphones APPEAR more efficient than they really are, to folks who don't know or don't care to know the distinction. I mean, a lot of folks would think the HD570 is efficient, based on it's dB/V rating, when in fact it's one of the LEAST efficient headphones I've ever seen.

I had put together a similar database, though with not quite so many headphones, calculating maximum volume based on the manufacturer's rated max mW. The loudest headphones I've noticed so far are the Senn HD25 at 143dB, followed closely by the Beyer DJX-1 at 142dB, and the Sony V900 at 140dB. Loudest "audiophile" cans being the AT L3000 at 137dB.

FYI I noticed a couple of efficiency errors in your database, the Beyer DT531 should be 94dB/mW, and the DT831 98db/mW. I don't know why but they are commonly listed at 96 on most websites, even though the values I listed are given right on their respective boxes.
 
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sgrossklass

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A couple more Senns:
HD525: 94 dB/mW
HD535: 97 dB/mW
HD545, HD565: 96 dB/mW
(all 150 ohm)
HD455: 94 +/-2 dB/mW, 52 ohm
HD465 (old), HD475: 94 +/- 2 dB/mW, 60 ohm
HD560: 94 dB/mW, 300 ohm
(Actually pretty much all pre-1991 open Senns were spec'd at 94 dB/mW, though I've found the HD540 to play noticeably louder than a HD420SL and HD430 in spite of its impedance being slightly higher still - ~607 ohm instead of ~580 ohm.)
The HD590 was originally spec'd at 97 dB/mW (just like HD600 and HD650, apparently the '650 with its newer drivers is a touch more sensitive), but since it was noted to be more sensitive than the "120 ohm" (actually more like 150 ohm, as per Headroom) HD595 and is generally fairly easy to drive, 100 might also be possible. Note that my '590 measures ~99 ohms of DC resistance, so its true nominal impedance should be closer to 100 ohms... which would mean precisely 100 dB/mW assuming we are to trust the 110 dB/1Veff spec (otherwise this would be 107 dB/1Veff).
The "120 ohm" HD595 was spec'd with 104 dB/1Veff, which makes 95.8 or ~96 dB/mW considering it's actually 150 ohms.
 
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sgrossklass

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Cans added, HD280 corrected (spec'd at 102 dB/mW, or 113 dB/Vrms), DT531/831 changed, formatting in computed cells changed to no decimals (no precision stuff anyway). Hopefully no compatibility issues arise, I have OOo 1.1.4 here. Seems one can only upload oldschool zip files, could someone please add 7-Zip (.7z)? (That same file would have been only 15K then.)
 
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j-curve

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Iron_Dreamer, thanks for the corrections. I'm not sure where I got the Beyerdynamic specifications, but evidently it wasn't from the Beyer website - search for the DT531 there and nothing comes up. I agree that numbers off headphone boxes will in general be more reliable than numbers from websites.

So keep the corrections coming in, folks!

Sgrossklass, thanks for the raft of Senn's, and especially for fixing up the HD280 spec., which was out by 11dB!
Now I know that "IEC 268-7" means dB/V, not dB/mW.
Quote:

sgrossklass: Hopefully no compatibility issues arise, I have OOo 1.1.4 here.


Unfortunately there are a couple of issues when loading back into Excel: the macro buttons were no longer linked to the macros, although surprisingly the macros were still intact. Also, the font in the comment boxes changed, so the text didn't fit. Minor issues, but for that reason I've incorporated your changes back into the file attached to the first message.

Speaking of which, only 26 downloads so far, a bit disappointing. I think more people should be aware of this because modern headphones are too sensitive. Even with the HD215, which is only 112dB/V, I'm hearing hiss from my headphone amplifier and computer soundcard. At present there are 146 headphones in the database with equal or greater sensitivity, and only 84 headphones with lower sensitivity, so there must be a lot of people suffering background noise with their music.

Not only that, many of the smaller headphones and earphones available (including all of the canal phones) have sensitivities of 122dB/V and above. A recent thread asked for lists of portables which hissed and those which didn't. People are hearing hiss from op-amps, even when there is no power transistor buffer stage involved. We're talking about microvolts of electronic noise, this is crazy.

End rant, I suppose.
 
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sgrossklass

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Quote:

Originally Posted by j-curve
I think more people should be aware of this because modern headphones are too sensitive.


Good point. Particularly "home headphones" are too low in impedance these days, which makes them prone to FR changes due to output impedance and difficult to drive with unbuffered amps (worst-case: low-impedance and rather insensitive, e.g. K501, K601/701, SBC-HP1000; the current HD5x5 also are a little weird in that they combine 50 ohm drivers with 1/4" connector). When I still used the TX-SV636's output, the background noise with the HD590 did bother me a bit, and these cans still need to be operated at higher volume levels than I'd like on the BT928 run off a tuner with rather high output level, due to volume pot channel imbalance - and the amp has already been modded for lower gain, among other things. In fact, I tend to listen to the old HD420SL (600 ohm, supposedly 94 dB/mW but possibly lower) at a volume only a little higher than what's needed for proper channel balance, which also has to do with this being my bedside rig and operated when ambient noise is very low. I kinda like 600 ohm cans in general.

Oh, and my K26P doesn't exhibit much noise on the G3, though I admit that its 110 dB/mW spec is quite amazing. I guess portable phones are made this sensitive to be powered easily even by 5mW/ch or "euro-capped" weaklings (my G3 will power even the HD420SL but this apparently can't be taken for granted with all players), and outside ambient noise is usually going to drown out background hiss anyway... unless one is using IEMs.
 
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Good work!
 
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sgrossklass

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Semi-current versions:
OpenDocument format
OpenOffice 1.x format
This is lacking the Denon AH-Dx000 models and who knows what else, so if you've spotted a bunch of missing models, post these (plus the necessary data) here.
 
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j-curve

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Denons spotted here (japanese font).
AH-D5000, 25 Ohms, 106 dB/mW
AH-D2000, 25, 106
AH-D1000, 32, 103
 
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jung

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Quote:

Originally Posted by j-curve /img/forum/go_quote.gif
Speaking of which, only 26 downloads so far, a bit disappointing. I think more people should be aware of this because modern headphones are too sensitive.


It would be more accessable if you have these in HTML on a web page, instead of a spreadsheet.
 
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jung

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Quote:

Originally Posted by j-curve /img/forum/go_quote.gif
Headphone efficiency has been quoted in dB/mW ever since headphones were invented, hasn't it? Probably a good idea too, because it was fairly easy to calculate how much power you were going to need. It also allowed manufacturers to compete on a meaningful basis, improving efficiency with better designs, stronger magnets, lighter diaphragms, etc.

Recently there has been a move by Sennheiser and AKG to abandon the traditional measurement and quote sensitivity in dB/V instead. This could be an even better idea, because amplifiers are primarily voltage devices, and now we have a number which doesn't require a tertiary qualification in electronics to figure out how loud our headphones will sound. The downside is that if manufacturers compete on dB/V sensitivity, there will be an inevitable trend to lower impedance headphones, and we'll hear background hiss every time we plug into any source.

In the meantime, we have two different standards for specifying loudness, neither of which is definitive because it can still depend on the output impedance of the amplifier, and whether or not the headphones you're comparing will be plugged into the source at the same time or one after the other.



Besides dB/mW and dB/V, dB/mA may be interesting, too. Also, the power required to output 110dB, mW/110dB, mV/110dB, and mA/110dB:
http://stereo.50webs.com/

My question is, do headphone amps mainly supply voltage or current? I thought if an amp does not have enough voltage, the hard clipping will result in harsh high frequency noise. So if the harsh distortion is not obvious, but it does not sound good, I thought it is because the amp can not supply enough current. But from the calculation, even low efficiency low impedence phone like K701 only needs 29mA to produce 110dB, not much more than SR60's 22mA.
 
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AKG K340: 88 dB/mW
 
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hey, sorry to bringing to life a very dead thread, but I have been searching for hours and have not been able to find the SPL dB / mW rating for the AKG K701's (or an actual conversion formula, either). I just bought a pair and would like to know the sensitivity to pair it up with a respective amplifier.
 
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jung

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Quote:

Originally Posted by T_Schmidt /img/forum/go_quote.gif
hey, sorry to bringing to life a very dead thread, but I have been searching for hours and have not been able to find the SPL dB / mW rating for the AKG K701's (or an actual conversion formula, either). I just bought a pair and would like to know the sensitivity to pair it up with a respective amplifier.


AKG K701 93 dB/mW 105 dB/V

See my page:
http://stereo.50webs.com/
 
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