John Curl's Blowtorch preamplifier part II

[qusp]

Originally Posted by Max Headroom

Try Ford V8 valve springs as equipment and speaker supports.....works for me.

Dan.

chill out with some smoldering cones, cheaper again...

[john curl]

Well, a measurement of the headphone should SHOW THE RESONANCE. Once I had a pair of Beyer DT-48S phones, that I flew to LA from SF just to buy in the 60's. They were 'clean' but bright in the midrange and I could hear HISS with these phones better than any other way. We measured these phones in 1974 in our lab in Switzerland with a B&K artificial ear that we had in the lab. I found this amazing midrange resonance that was both a notch and then a peak. It certainly set the midrange for these phones.
As with Demian, a colleague, and even more in-tune with modern headphone design, I hardly know what you folks have been arguing about for the last day or so.
Yesterday I heard a pair of Sennheiser headphones (very expensive) and found them free of any lack of smoothness, at least on a short term listening.

[qusp]

Well, a measurement of the headphone should SHOW THE RESONANCE

it does....

no idea what Frank has been arguing about, hes not heard them before...

not looking for smoothness, just lack of painfulness

[Esperado]

Originally Posted by bcarso

And Paul Tanner, wonderful trombonist, sterling educator, and outstandingly nice person, just passed. He played Theremin on that Beach Boys tune.

It is boring, this landscape witch looks more and more like a cemetery !

[Esperado]

Originally Posted by john curl

Yesterday I heard a pair of Sennheiser headphones (very expensive) and found them free of any lack of smoothness, at least on a short term listening.

It seems our ability to tolerate large accidents in response curves of headphones is amazingly large. May-be our brain, able to discriminate rooms resonances, is doing some auto correction because no room ?
More than that, if i can correlate the response curve of a loudspeaker with listening impression, it is not so true with headphones. I make big mistakes when i try to equalize some instruments with some headphones.
On the contrary, i'm unable to suffer any earphone and cannot afford closed headphone for a long time.
I wonder why it seems so difficult to build good headphones, while it seems easier than speakers (little membranes, low power).

[1audio]

Originally Posted by qusp

it does....

no idea what Frank has been arguing about, hes not heard them before...

not looking for smoothness, just lack of painfulness

The resonance is most likely a dimensional issue and may not be fixable with damping. Its so high Q I doubt you can actually hear it with music, maybe with an oscillator. The sound issues are more likely the back cavity material or the diaphragm. The big problem with diaphragms for these is that they are very thin to get the sensitivity and extended highs and they breakup at pretty low drive levels. I have not found a way to measure this since it changes a lot between on ear and free space. Cut and try seems to be the way to get a good sounding headphone. You won't get there with instruments alone.

If you look at the different plots even the very big change (1 CM pad) makes a very small change in the response and magnitude of the peak. The changes I saw could be from removing and replacing the headphone on the fixture with no changes to it. Usually you need to make several plots to be sure of your measurement.

The different pads will make a difference, more from absorbing energy in the cavity than anything else. There are some exotic damping materials that might work better. If you have the headphone apart the "tap test" may be the best. Tap and listen to the parts. Metal parts tend to be high Q and seem to be pretty audible. But plastic looks cheap. Fortunately we are getting plastics that really look like metal today.

[1audio]

Originally Posted by Esperado

It seems our ability to tolerate large accidents in response curves of headphones is amazingly large.

Speakers as well. Welcome to www.SoundStageAV.com

Look through the curves and you will see little correlation between response and perceived quality. There seems a higher correlation between distortion and perceived quality even when the response is really weird: SoundStage! Measurements - Zu Cable Druid Loudspeakers (9/2002)

I suspect response issues are the same as color balance, The colors change when the light source is incandescent or open sky but you can still tell red from green from blue. Your hearing can pull the pattern of a voice and allow you to recognize who is calling regardless of the response variations and horrible distortions of a cell phone. Perhaps the best gauge of an audio system is the reaction in the first 100 mS before your brain has processed and removed the overall signature of the sound system. Listen to a speaker for an hour and it will sound pretty correct and whatever is next will be wrong. This may be why a-b tests are do hard to do.

[qusp]

I dont think its the resonance/peak thats actually heard directly, more a sort of anomaly; a diffraction/interference/cancellation caused by that resonance, sort of comb filtering and its the peaks and dips within all that complexity bouncing around and canceling out what should be there that is 'heard' sort of an absense of the bass or mids that should be there, rather than a peak in the treble, but translates as a peak/resonance in the treble.

I dont, nor would I ever own them, but i've spent a fair bit of time with different peoples (including several in my own home on my gear) and I have the same or similar issue with all of them. they are mostly a very rigid hitech plastic, except for the diaphragm and the piece that seems to cause the problem, which they have made an attempt to damp, maybe by ear so it worked for those in the test grpoup, or the designers themselves, but shows up randomly among users depending on the shape of the ear and its localized response.

dont know if that makes any sense, its odd, even without it I wouldnt buy them, but its my main critique of them.

[gk7]

Originally Posted by john curl

...
Yesterday I heard a pair of Sennheiser headphones (very expensive) and found them free of any lack of smoothness, at least on a short term listening.

HD800 ?

[qusp]

if it was a promotional event they were probably flogging the momentum