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Author Topic: Non-linear Distortion Thread  (Read 2114 times)

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Marvey

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Non-linear Distortion Thread
« on: February 21, 2012, 10:02:12 PM »
Will start a similar thread on HF soon.

Differences in distortion of a 50Hz sine wave @ 90db on the HD800 and HP1000. For those who've heard both headphones - they know the bass sounds completely different. These graphs give us an insight into why. HD800 is dominated by the 3rd order harmonic at 150Hz. The HP1000 is dominated by 2nd order harmonics at 100Hz - quite a lot of it too.

These graphs illustrate why saying a headphone has 0.5% distortion at 50Hz doesn't say much.

Also see:

http://www.changstar.com/index.php/topic,298.0.html
http://www.changstar.com/index.php/topic,131.msg1156.html#msg1156
« Last Edit: May 22, 2012, 12:43:30 AM by purrin »
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LFF

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Re: Non-linear Distortion Thread
« Reply #1 on: February 21, 2012, 11:16:52 PM »
LOL!
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ocswing

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Re: Non-linear Distortion Thread
« Reply #2 on: February 21, 2012, 11:18:57 PM »
I don't have a frame of reference on these. Does the lower peak around 30hz on the HP1000 make a difference as well?
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Marvey

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Re: Non-linear Distortion Thread
« Reply #3 on: February 24, 2012, 05:46:55 AM »
LCD3 50Hz

The 150Hz spike is environmental noise not attributable to the LCD3. Don't know why it's there tonight...
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Marvey

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Re: Non-linear Distortion Thread
« Reply #4 on: February 24, 2012, 05:49:58 AM »
Quote from: ocswing on February 21, 2012, 11:18:57 PM
I don't have a frame of reference on these. Does the lower peak around 30hz on the HP1000 make a difference as well?


A lot of the sub bass 20-40Hz is environmental noise.
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regal

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Re: Non-linear Distortion Thread
« Reply #5 on: March 11, 2012, 06:13:25 AM »
Are you familiar with a Loftin-White topology?  Basically two gain stages SE.   Some 2H is cancelled by the second stage since they both have inverting outputs.  Not P-P 2H cancellation but SE.

So with the HP1000 you have shown some 2H distotion,  developed back when a typical amp driving them had some 2H distortion.  Note that originally Grado had phase inversion switches on the HP's.

Do you think or have any of your measurements shown that 2H from an amp can be cancelled by the headphone driver (if it is a 2H dominant one)  ?

The other issue is the temporal membrane has a 2H distorion which mainy postulate cancels out 2H distortion.   

I guess what I am saying is a driver with 2H distortion could be a good thing because it is not actually known to be an issue by the time it hits the auditory section of our brain  :-\
« Last Edit: March 11, 2012, 06:17:15 AM by regal »
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Marvey

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Re: Non-linear Distortion Thread
« Reply #6 on: March 11, 2012, 07:02:55 AM »
I dunno. I ran these out of the Objective2 amp, which is very clean according to nwavguy's measurements. Even at 90db, we're talking miliwatts here since the HP1000s are still quite efficient.


Second order is probably more benign than third or odd order, but honestly, I'd prefer to not have any at all, especially at such high a level. The LCD2/3 bass is simply just amazing. Hits loud and clear.
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regal

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Re: Non-linear Distortion Thread
« Reply #7 on: March 11, 2012, 11:54:59 AM »
Thats what I am getting at.  The O2 has extremly high distortion devices that are cancelled by heavy NFB,  seems a logical choice for testing drivers today,  but these drivers were developed a long time ago..

If you consider the headphone as part of the system,  should you consider a proper phase amp with 2H,  which would possible cancel the distortion of the HP drivers.   Mr Grado is pretty smart and didn't have low distortion amps at the time the drivers were developed.  Also probably didn't have 1ohm output impedance either.

Do you understand what I am trying to say and the analogy to Loftin-White ?

Maybe a fair question would be to find out the studio amp Mr Grado developed the drivers with and work from there.

Heck using the O2 is about as far from the 1996 IEC 61938 standard that you can get.

Not questioning your work,  but this is really still R&D.  Measuring Speakers is different because they decided to standardize for lowest output impedance and high NFB amplification,  not so with headphone drivers,  especially when the HP's were developed.
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Marvey

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Re: Non-linear Distortion Thread
« Reply #8 on: March 11, 2012, 04:44:47 PM »
I guess what I don't understand is the following:
  • How an an amp with the L-W topology would actually be able to create 2nd harmonic distortion which just happens to be opposite in phase to the distortion of the drivers to cancel the distortion
  • Why anyone in their right mind would build an L-W topology with so much distortion at normal listening levels that it be able to cancel a significant part of the distortion from the HP1000 driver (since distortion from drivers is magnitudes higher than any amp.)
  • It's a fallacy to think that amps somehow were more primitive or not good in the eighties. The state of audio hasn't progressed much for sixty years. In any case, the HP1000s do sound better out of low Z amps than high Z ones.
Also Joe made the HPA1 to power his headphones. I believe the HPA1 is similar to the RA1 - an op-amp based head-amp with fairly low output impedance.
« Last Edit: March 11, 2012, 07:27:23 PM by purrin »
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RexAeterna

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Re: Non-linear Distortion Thread
« Reply #9 on: March 11, 2012, 11:03:17 PM »
Quote from: purrin on March 11, 2012, 04:44:47 PM
The state of audio hasn't progressed much for sixty years. In any case

so true. not just audio but pretty much monitors too. i still haven't found a S-IPS panel produce as accurate and true to life colors as something like a Sony GDM-FW900 CRT. might weigh over 100lbs and run off of kittens blood but still one best monitors i ever used.
« Last Edit: March 12, 2012, 12:02:07 AM by RexAeterna »
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