[wavoman]

August 2008 issue just hit my mailbox. Long article by Keith Howard about the "science of measuring headphones". Mostly about artificial ears and the correct way to measure freq response. The actual HPs tested were not that interesting. In fact the overall article was not that gripping, which surprised me. One "conclusion": you have to test the cans and the amp together, a different HP amp leads to a different sound.

Duh. The author should hang out here more.

But opposite Page 115 is a nice plug for CanJam by Jorges at HeadRoom. He discusses 08 and tells people to come to 09. Super! Bravo HeadRoom!

 

[eruditass]

do they have any of this online?

 

[charonme]

What? Stereophile approves measurement/objective testing?

 

[ingwe]

Quote:

Originally Posted by charonme /img/forum/go_quote.gif What? Stereophile approves measurement/objective testing?

They're very into measurements. Always have been, I believe.

 

[spraggih]

I enjoyed the article-- not sure if it is online.

Here are excerpts (do believe this falls under fair use):

Excerpt 1
A more serious issue in most cases is repeatability... Five consecutive one-shot measurements of one capsule of a Senn 650, which was untouched during the measurements. Above 100Hz the responses overlap almost exactly...as you would expect... however at lower frequencies the disparities become progressively larger until at 18Hz the largest difference is 2.7dB. Remember that the headphone had not be removed during these measurements, so the errors must be due to the presence of low frequency environment sounds

In other words... believe it or not for open headphones the room is affecting the sound quality of the headphones just like with speakers (sound bouncing off of walls, floor, etc.)The writer believes this affects electrostatics mostly.

Excerpt 2
The ramifications for subjective assessment of headphones are more troublesome because it is usually unclear what assumptions the [headphone] manufacturer made regarding source impedance. Designed for near zero impedance or the 120 ohms suggested by the IEC?


In other words... it is believed source impedance affects tonal balance so if you have your review source and amplifier that you always use-- and you review/test a headphone it is possible it will not sound well due impedance of the amp).
We all know about synergy but this suggests synergy could be there but could not be maximized, heard because of a simple electrical concern of impedance. Once the impedance and expected headphone impedance is known it can be remedied.

 

[dvessel]

Quote:

Originally Posted by spraggih /img/forum/go_quote.gif [/B]In other words... believe it or not for open headphones the room is affecting the sound quality of the headphones just like with speakers (sound bouncing off of walls, floor, etc.)The writer believes this affects electrostatics mostly. [/i]

Seems implausible. Low frequency sounds bouncing from the head phones to the room? Maybe they had a refrigerator running in the next room.

 

[spraggih]

Hey I am just the messenger. That's what they say.

 

[warpdriver]

Quote:

Originally Posted by charonme /img/forum/go_quote.gif What? Stereophile approves measurement/objective testing?

The majority of the reviews they publish have extremely detailed measurements.

 

[James63]

Their reviews are junk.... They only review speakers that already have good rep. But their measurements are first rate. I don't read a word they right but take good time looking at their measurements.

As for the room affecting headphones

Ok just did a quick test with my 650s in a 15 foot by 15 foot room turned up to 80db (inside the cup). I then measured the volume from 7 feet. At seven feet I could only read the peaks at 55db. So I lost 25dB over 7 feet and I would assume I would loose another 25dB or more on the sounds way back to the headphones..... That would give you a 50dB drop.

Now when stereophile measures cabinet noise they do not worry about anything that has dropped by 30dB and consider it in audible.

Here is an example of their comments.

"As shown by fig.2, a waterfall plot calculated from the accelerometer's output when it was attached to the back panel, there were two modes present, at 360Hz and 539Hz, but these are low enough in level and high enough in frequency to be not worth worrying about."

Stereophile: Wilson Audio Specialties Sophia loudspeaker

 

[charonme]

Quote:

Originally Posted by warpdriver /img/forum/go_quote.gif The majority of the reviews they publish have extremely detailed measurements.

Quote:

Originally Posted by ingwe /img/forum/go_quote.gif They're very into measurements. Always have been, I believe.

Eh, my bad then, I mistook them for some other magazine

 

[pirate6955]

Quote:

Originally Posted by James63 /img/forum/go_quote.gif Ok just did a quick test with my 650s in a 15 foot by 15 foot room turned up to 80db (inside the cup). I then measured the volume from 7 feet. At seven feet I could only read the peaks at 55db. So I lost 25dB over 7 feet and I would assume I would loose another 25dB or more on the sounds way back to the headphones..... That would give you a 50dB drop.

if i remember correctly sound level [amplitude] drops as the square of distance. its like gravity i think, no way to avoid it....

 

[pirate6955]

Quote:

Originally Posted by spraggih /img/forum/go_quote.gif We all know about synergy but this suggests synergy could be there but could not be maximized, heard because of a simple electrical concern of impedance. Once the impedance and expected headphone impedance is known it can be remedied.

and what about reactance? VARS? or the drivers ability to overpower the amplifier with counter EMF? the only thing differentiating a generator from a motor are VARS or the generators resistance to being a motor.... no?

never saw a power factor measurement for a stereo amp driver setup. basically different amp/driver combos have different power factors. this could be corrected to mate any driver amp combo. the cable would affect this too of course, big time.