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Old 18th June 2010, 05:07 AM   #4761
Gordy is offline Gordy  United Kingdom
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Quote:
Originally Posted by johnferrier View Post
I've seen measurements for three pairs of Audez’e headphones indicating that 90 decibels requires 0.111, 0.134, and 0.119 Vrms. Which is like 124 dB at 6 Vrms.
Thanks for the clarification John. That makes their sensitivity about 95 dB at 1 mW. They ought to update their published specifications. I'm still surprised 6V was needed... hope you ears are OK Demian!
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Old 18th June 2010, 01:46 PM   #4762
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Quote:
Originally Posted by johnferrier View Post
I've seen measurements for three pairs of Audez’e headphones indicating that 90 decibels requires 0.111, 0.134, and 0.119 Vrms. Which is like 124 dB at 6 Vrms.

Still shy of loudnesses achieved at concerts of Manowar, My Bloody Valentine, and Gallows (> 130 dB). Not sure, but crescendos of large orchestras will probably approach 124 dB.

-

Maximum output: 133dB, 15W
Audez'e LCD-2 --> Wikiphonia
Two important points;

With headphones peak levels can be 30 db or more than listening levels.

It is not quite so simple to measure what a headphone delivers to the listeners ears. There is standardized equipment to do this which gives reasonably nice repeatable results, however although it corresponds to what is delivered to humans it is not the same.


I was asked to review the test data in a hearing loss claim. The plaintiff's expert used a cavity that was half the volume of the standard so that all his numbers were 6 db higher. A small note mention that the results were comparable to the standard. But then the hearing loss was the same in both ears and the exposure was only to the left ear.
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Old 18th June 2010, 02:23 PM   #4763
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Quote:
Originally Posted by simon7000 View Post
With headphones peak levels can be 30 db or more than listening levels.
Because of music dynamics, the peak is 30 dB over the average level. And the same signals ought to produce approximately the same dynamics with a speaker system.

Regardless, a time averaged 90 dB to the ears with headphones or speakers is the same, right? (Lets say for one 4 minutes songs so that we are not trying to damage ears.)
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Old 18th June 2010, 03:00 PM   #4764
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Quote:
Originally Posted by johnferrier View Post
Because of music dynamics, the peak is 30 dB over the average level. And the same signals ought to produce approximately the same dynamics with a speaker system.

Regardless, a time averaged 90 dB to the ears with headphones or speakers is the same, right? (Lets say for one 4 minutes songs so that we are not trying to damage ears.)
Actually with loudspeakers and the room masking caused by even the limited reverberation in the listening space 20db is more the norm. That is why some use headphones for more critical listening. In doing live symphony work outdoors I found I could hear clipping when the system had less than 30db of headroom. Indoors that drops to 20db. So for headphones the minimum should be at least 30db maybe even more.

An average level of 90 is louder than I prefer, however Osha allows 8 hours per day to 90db. The WHO allows 11 minutes for 91db! Testing if hearing damage is the same from headphones or loudspeakers would be an interesting research project, any volunteers?

But I suspect that with the large volume of the headphone's coupling space that the measured sensitivity is really delivering about 80db to the listener. That is allowed for several hours by the WHO.

The other factor not stated is power compression or that at the loudest levels the increase in volume is not the same as at lower power levels.

So these reasonably efficient headphones used 40db below clipping for really critical listening could possibly be used all day and meet everyones hearing preservation standard.

But that is my OPINION as to the possibility, I have not measured them or seen the test setup used by others or even how big someone else's ear cavities are!

Last edited by simon7000; 18th June 2010 at 03:03 PM.
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Old 18th June 2010, 03:59 PM   #4765
1audio is offline 1audio  United States
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The LCD-2's have a large internal volume. They are too large for my NBS9a coupler- they overhang the edge and have a huge leak. The sensitivity numbers sound about right. I don't listen at such high levels. However the extra drive or some aspect related seems to have a significant impact on the perceived bass impact and depth.

Measuring SPL inside a headphone is an exercise in standards vs reality. Academics have been going around and around over this for years. You can use a probe microphone and measure the spl inside even an in ear headphone. However the relationship between that and perceived level or response is, shall we say, not established. The headphone manufacturers just ask for a target curve since there is no accepted "right" curve.

This is drifting pretty far from Blowtorch stuff, except perhaps the drive issue.
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Old 18th June 2010, 04:04 PM   #4766
jcx is offline jcx  United States
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Mr Curl does talk a lot about the low (noise) end of dynamic range - maybe he also has thoughts on the other end?

I certainly advocate for "audiophile grade" headphone amps to at least be able to drive the desired headphones to 120 dB SPL without clipping

for low feedback circuits, operating at a small fraction of the bias point is another tool for distortion reduction - again pointing to huge "headroom" being desirable

Last edited by jcx; 18th June 2010 at 04:18 PM.
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Old 18th June 2010, 07:01 PM   #4767
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I promised Kirkwood Rough's e-mail. What I have, and I'm pretty sure it works is:

<removed by moderator -- please distribute this info by private message or email> Give it a shot.
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Old 18th June 2010, 07:12 PM   #4768
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Oh darn, I was just trying to help.
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Old 18th June 2010, 07:55 PM   #4769
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Quote:
Originally Posted by john curl View Post
I promised Kirkwood Rough's e-mail. What I have, and I'm pretty sure it works is:

<removed by moderator -- please distribute this info by private message or email> Give it a shot.
It seems like my previous post was deleted.
So I'm trying again.

John could you please email me the info from Kirkwood?

Cheers
Stein
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Old 18th June 2010, 09:49 PM   #4770
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This was only a follow-up to a previous request, and Scott Wurcer having a problem with K's e-mail address. It is really up to Scott Wurcer to follow up.
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