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squarewaves for headphone measurements is it useful ?

solderdude

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#1
The conversion to sound waves is very flawed compared to electronics. Even the excellent Sennheiser HD 800 S converts a square wave of whatever frequency into a signal that is barely identifiable as a square wave.

Taking that into account, it's almost ridiculous how bad speakers and headphones are compared to electronics.

Above the 440Hz square-wave of the HD800, below the HD650.


The HD650 produce about the best squarewaves I have measured to date.
 

March Audio

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#2

Above the 440Hz square-wave of the HD800, below the HD650.


The HD650 produce about the best squarewaves I have measured to date.

A fairer test would be to band limit the square wave to say 20kHz first. Its really not a useful test as the original square wave shown will have harmonics spreading beyond the bandwidth of the transducer, in which case they will never look the same and never be a representative test.
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solderdude

solderdude

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Thread Starter #3
A fairer test would be to band limit the square wave to say 20kHz first. Its really not a useful test as the original square wave shown will have harmonics spreading beyond the bandwidth of the transducer, in which case they will never look the same and never be a representative test.
Bandwidth limiting is caused by the microphone and/or driver. The squarewave is 'real' and does not need to be bandwidth limited as the 'receiving side' is an oscilloscope and not an audio ADC.
To me the test is quite usefull anyway as the scales are linear and it says a lot about ringing etc.
I also measure at 40Hz and impulse (but not the same as Tyll did)
These 3 measurements give me extra insight in the performance of the headphone.. so they may not be usefull for some but to me they are as I know the limits of the test and explain them on the website.

Those thinking they can hear far beyond 20kHz will have something to moan about and would demand 100kHz minimum for this test. ;)
 
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March Audio

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#4
Bandwidth limiting is caused by the microphone and/or driver. The squarewave is 'real' and does not need to be bandwidth limited as the 'receiving side' is an oscilloscope and not an audio ADC.

Those thinking they can hear far beyond 20kHz will have something to moan about and would demand 100kHz minimum for this test. ;)
No its not real. It can only be reproduced accurately by a system with infinite bandwidth. Its not a useful real world test to compare non-band limited signals with band limited signals expecting them to appear the same. They simply wont.

See the above plot of a 20kHz filtered 440Hz square wave. Sloping edges and ringing. You need to filter within the limits of the headphones and measurement microphone.
 
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solderdude

solderdude

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Thread Starter #5
No its not real. It can only be reproduced accurately by a system with infinite bandwidth. Its not a useful real world test to compare no-band limited signals with band limited signals expecting them to appear the same. They simply wont.

See the above plot of a 20kHz filtered 440Hz square wave. Sloping edges and ringing
Have you ever seen a bandwidth limited scope shot of a squarewave though an amp ? It doesn't look that way because the filtering is not as steep.
Why would I limit bandwidth to 20kHz in such a steep way when I measure FR all the way up to 30kHz ?
The 'ringing' would also be shown in that plot and is not there when using 96/24 formats for instance, they ring around 90kHz.

By the way... I don't expect the plots to be the same. I look at the ringing of the driver and waveform shape. This tells me bits about its behaviour.

With EQ the HD800 looks different of course. I don't think the squarewaves tell everything. Just like FR does not tell everything nor distortion.
It's an entire measurement suite + subjective evaluation.
Despite the HD650 looking 'better' on the squarewaves and other measurements the HD800 (with EQ) to me sounds a LOT better in many many aspects.
 

Krunok

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#6
A fairer test would be to band limit the square wave to say 20kHz first. Its really not a useful test as the original square wave shown will have harmonics spreading beyond the bandwidth of the transducer, in which case they will never look the same and never be a representative test.
Shouldn't we apply the same rule when measuring equipment as well? RBCD recordings won't have much above 22kHz, right?
 

March Audio

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#7
Shouldn't we apply the same rule when measuring equipment as well? RBCD recordings won't have much above 22kHz, right?
Yes. This is why I take issue with those DAC single sample impulse filter tests. OK, they have use in showing what type of filter it is, but beyond that it has no relevance. A single sample is an illegal signal and will never be encountered as the ADC should filter anything above 1/2 FS. So you want to see what an output filter really does, put in a half sine cycle at 22.05kHz (for 44.1kHz)
 
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solderdude

solderdude

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Thread Starter #8
Oops.. I have the HD 650 and think about upgrading to the HD 800 S :(.
From which years are those specific models?
Are these your private measurements or are they available online? I would be interested in comparing them to Tyll's on innerfidelity.com.
All my measurements are online.
They do not compare to Tyll's in any way.
I think the HD800 is a MUCH better headphone in many aspects (that count to me) but only with 'proper' EQ.
There are others that find the HD650 better.
So... audition but recommend to do so with EQ in place or in mind.
I learned to never buy a headphone or speaker based on measurements.
Bought, sold and auditioned well over 200 headphones already.
They can only 'help' a bit as a guide.
 
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solderdude

solderdude

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Thread Starter #9
Shouldn't we apply the same rule when measuring equipment as well? RBCD recordings won't have much above 22kHz, right?
Don't you want to know how much garbage there is above 20kHz which may hurt the sound when 'folded back' into the audible range ?
 

Krunok

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#10
All my measurements are online.
They do not compare to Tyll's in any way.
I think the HD800 is a MUCH better headphone in many aspects (that count to me) but only with 'proper' EQ.
There are others that find the HD650 better.
So... audition but recommend to do so with EQ in place or in mind.
I learned to never buy a headphone or speaker based on measurements.
Bought, sold and auditioned well over 200 headphones already.
They can only 'help' a bit as a guide.
Impressive list!

As I need to buy heaphones as a present for my son which model would you recommend in the $500 price range? :)
 

Krunok

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#11
Don't you want to know how much garbage there is above 20kHz which may hurt the sound when 'folded back' into the audible range ?
I'm not listening to HiRes as I don't believe in it and I don't think there is much above 20kHz on RBCD recordings. I do believe that decent electronic equipment should have some technical reserve so expecting it to perform well up to 48kHz seems reasonable to me. But I see no point in measuring above that.
 
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solderdude

solderdude

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Thread Starter #12
Impressive list!

As I need to buy heaphones as a present for my son which model would you recommend in the $500 price range? :)
Impossible to tell..
Headsize, Pinna size and position, comfort, open, closed, portable gear or desktop, fashionable, retro, music taste, listening SPL, looks, price ?
I really can only tell you which headphones I like myself and know there are plenty that have very different preferences/choices.
 
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Krunok

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#13
Impossible to tell..
Headsize, Pinna size and position, comfort, open, closed, portable gear or desktop, fashionable, retro, music taste, listening SPL, looks ?
I really can only tell you which headphones I like myself.
They should be over-ear with ability to replace cable. He listens rock music (Pink Floyd, Dire straits, Santana, ..). He plays solo el. guitar, so they should be able to reproduce that well. Moderate SPL.

He had tried Sennheiser HD1 and he likes them. Anything similar to that but better in sound?
 

Blumlein 88

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Impossible to tell..
Headsize, Pinna size and position, comfort, open, closed, portable gear or desktop, fashionable, retro, music taste, listening SPL, looks, price ?
I really can only tell you which headphones I like myself and know there are plenty that have very different preferences/choices.
I read a few of your reviews on headphones I've owned or used. Your description of the sound seems dead on to what I hear of them. Especially the various Grados. I could hear in the first two minutes why people talked about them, and also why I couldn't live with them for more than about 5 minutes. I'd used SR325s which were the best of theirs I'd heard. The basic character was still there. It was better than the SR60's and SR80's I owned for a short time, but still the same sort of sound balance.

I've still have some DT880 Pro phones, and your description seems right on those also. I've always found them a bit bright or sharp at high levels, but at more normal levels I could live with it due to their good qualities elsewhere. I'll have to try the tissue paper trick. Reminds me of the T-shirt trick I'd suggest for early Thiel speakers. Cut a circle from a cotton t-shirt a bit larger than the tweeter and put it inside the cloth in front of the tweeter.
 
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solderdude

solderdude

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Thread Starter #15
They should be over-ear with ability to replace cable. He listens rock music (Pink Floyd, Dire straits, Santana, ..). He plays solo el. guitar, so they should be able to reproduce that well. Moderate SPL.

He had tried Sennheiser HD1 and he likes them. Anything similar to that but better in sound?
Never heard the HD1 but acc. to Rtings that measured them are close or equal to Momentum 2 over ear which I measured and heard (but did not own).
Rtings measurements here
My impression was the momentum is lacking in clarity but is fairly 'balanced' sounding but less 'quality' in bass.
I assume he wants a bit more 'spice' in clarity/presence and tighter bass ?

Would recommend to look into the Beyerdynamic COPP (but modified as per my website) or HD58X (Massdrop only or via people not liking it)
Maybe DT1990 (with EQ) but there are more in my recommended list which is loosely based on my preference which, looking at the plot of Rtings is close to his preference as well.
Maybe the ATH-M50X ? Beyer DT250 ?
Will always remain a personal thing though.
 

oivavoi

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#16

Above the 440Hz square-wave of the HD800, below the HD650.


The HD650 produce about the best squarewaves I have measured to date.
Cool. Thanks!

This is something I don't know: how do you actually measure a square wave on headphones and/or speakers?
 
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solderdude

solderdude

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Thread Starter #17
Built a purpose made squarewave and impulse generator (harmonics well into the MHz range) and an amplifier that runs to 120kHz (-0.2dB) = 0.4MHz (-3dB) that drives the headphone measured on a DIY rig with DIY purpose made pre-amp into a digital USB oscilloscope.

Not on speakers... I don't know of any speakers that do decent squarewaves aside from some planars.
 

March Audio

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#18
But keep in mind that music can be produced completely digitally with the use of digital instruments that may produce artificial signals (like digital synthesizers, e.g. many of Jean Michel Jarre's recordings). In that case there is never an ADC and a single sample is possible and a legal signal.
Im afraid that in that case a filter should still be part of the production process. Letting signals through higher than 1/2 FS is wrong however they are generated.
 

March Audio

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#19
Built a purpose made squarewave and impulse generator (harmonics well into the MHz range) and an amplifier that runs to 120kHz (-0.2dB) = 0.4MHz (-3dB) that drives the headphone measured on a DIY rig with DIY purpose made pre-amp into a digital USB oscilloscope.

.
But whats the purpose of that? We already know the transducer is bandwidth limited. A simple sweep tells us that and characterises it in a more meaningful and comprehensible way
 
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