The relevance of measurements to audible quality of sound

[March Audio]

The measurements tell us one of two things, you stated you liked the 650, so if you find bass issues with the 6xx then either your 6xx is not performing to spec/faulty or your perception of it, or that of the 650 is incorrect.

This is the beauty of measurement, it separates fact from perception (fiction).


https://www.innerfidelity.com/content/if-it-aint-brokethe-massdrop-sennheiser-hd-6xx

http://www.innerfidelity.com/images/MassdropHD6XX.pdf

http://www.innerfidelity.com/images/SennheiserHD650.pdf


Well...they've changed their tune a bit with the just announced Massdrop Sennheiser HD 6XX because in this case they didn't change the headphone's tuning it at all. (Measurements show the HD 6XX and HD 650 essentially identical within measurement errors.) No, there is really no reason for them to re-tune the Sennheiser HD 650. They've done their homework. They know that this is widely considered amongst headphone enthusiasts the standard by which all other headphones are compared. I've reviewed them and love them. Yes, there are better sounding high-end headphones, but none deliver the price/performance ratio of this icon.

 

[March Audio]

I would like to thank everyone for their input. It has been very interesting.

I have at least derived some sense here. I should look for a Headphone Amp (with or without DAC open at this point) with the following requiremenmts:

105dB Peak SPL midband and the ability to EQ the HD6XX to the Harman Target Curve from it's original Response found here:

https://www.innerfidelity.com/images/MassdropHD6XX.pdf

105dB peak need 0.86V.

The target requires +3dB @ 20Hz while the Headphone measures - 15dB, so 18dB extra output are required to allow for the EQ.

Thus 0.86V * 18dB (8x) = 6.88V, our amplifier should support at least 7V output. This seems a surprisingly high figure, but is a result of the required EQ.

It would be good, I think, to handle most of this EQ in the analogue domain. If done digitally we would need to attenuate the signal by 18dB to avoid the potential for clipping, which seems to have the potential of trouble, especially with less expensive equipment.

I think it would be possible to make a special cable with a passive EQ build in, but my soldering is not very good, I'd need someone to make this for me.

So we now have:

Headphone Amp with:
7V minimum output
Bass EQ 18dB at 20Hz
Optionally USB connected DAC
Price below 200 USD

Does anything come to mind?

Magnum Innominandum

I would be cautious about this level of EQ at low frequencies. It won't be an issue for an amp, if you can find one that delivers 7 volts, but the driver displacement will be very high and you may create significant distortion. It would need to be tested and measured.

 

[andreasmaaan]

I would like to thank everyone for their input. It has been very interesting.

I have at least derived some sense here. I should look for a Headphone Amp (with or without DAC open at this point) with the following requiremenmts:

105dB Peak SPL midband and the ability to EQ the HD6XX to the Harman Target Curve from it's original Response found here:

https://www.innerfidelity.com/images/MassdropHD6XX.pdf

105dB peak need 0.86V.

The target requires +3dB @ 20Hz while the Headphone measures - 15dB, so 18dB extra output are required to allow for the EQ.

Thus 0.86V * 18dB (8x) = 6.88V, our amplifier should support at least 7V output. This seems a surprisingly high figure, but is a result of the required EQ.

It would be good, I think, to handle most of this EQ in the analogue domain. If done digitally we would need to attenuate the signal by 18dB to avoid the potential for clipping, which seems to have the potential of trouble, especially with less expensive equipment.

I think it would be possible to make a special cable with a passive EQ build in, but my soldering is not very good, I'd need someone to make this for me.

So we now have:

Headphone Amp with:
7V minimum output
Bass EQ 18dB at 20Hz
Optionally USB connected DAC
Price below 200 USD

Does anything come to mind?

Magnum Innominandum

I agree with @BE718, this seems an extreme amount of EQ in the bass, particularly given the HD6xx is an open headphone.

There was some discussion of the Harman target curves and bass in another thread. An interesting suggestion was made (I forget by whom now) that maybe one reason there is such a significant bass boost in the Harman target was to do with subjects in the tests compensating for headphones sealing with their heads imperfectly. There's also a suggestion that the curve - in the bass anyway - is better suited to closed headphones. I think it was @Grave who found that EQing the DH650 to the target curve didn't seem to produce what he felt was a neutral result. I'm a bit hazy on the details now though...

Anyway, I'm not sure there's a definitive answer to this one without subjective experimentation and measurement. But you may not want to boost the bass by as much as you're suggesting.

Still, no harm in having the extra headroom for experimenting, if you can find a device capable of outputting that much power for a reasonable price.

Given you don't know how your laptop's DAC performs, you may also want to look for an integrated DAC/amp IMHO.

 

[Magnum Innominandum]

The measurements tell us one of two things, you stated you liked the 650, so if you find bass issues with the 6xx then either your 6xx is not performing to spec/faulty or your perception of it, or that of the 650 is incorrect.

Neither, I liked the HD650 despite the weak bass. Bass can be EQ'ed if the midrange is wrong this harder to fix. So I accepted the weak bass as I knew EQ can be used to fix this.

Magnum Innominandum

 

[solderdude]

I would like to thank everyone for their input. It has been very interesting.

I have at least derived some sense here. I should look for a Headphone Amp (with or without DAC open at this point) with the following requiremenmts:

105dB Peak SPL midband and the ability to EQ the HD6XX to the Harman Target Curve from it's original Response found here:

https://www.innerfidelity.com/images/MassdropHD6XX.pdf

105dB peak need 0.86V.

The target requires +3dB @ 20Hz while the Headphone measures - 15dB, so 18dB extra output are required to allow for the EQ.

Thus 0.86V * 18dB (8x) = 6.88V, our amplifier should support at least 7V output. This seems a surprisingly high figure, but is a result of the required EQ.

It would be good, I think, to handle most of this EQ in the analogue domain. If done digitally we would need to attenuate the signal by 18dB to avoid the potential for clipping, which seems to have the potential of trouble, especially with less expensive equipment.

I think it would be possible to make a special cable with a passive EQ build in, but my soldering is not very good, I'd need someone to make this for me.

So we now have:

Headphone Amp with:
7V minimum output
Bass EQ 18dB at 20Hz
Optionally USB connected DAC
Price below 200 USD

Does anything come to mind?

Magnum Innominandum

At 20Hz you will only need 7dB boost, my 'scientific' evidence (including target response) HERE

My efficiency numbers are different: 104dB @1V = 6.3V for 120dB peak
We want at least 3dB headroom so 9.6V eff is needed to drive it to loud levels.
For this you need an amp with +/- 15V rails.
The max voltage for the HD650 = 12V (0.5W) but peaks it can handle more.

When using digital EQ the level should be lowered by about 7dB in order to facilitate a boost of around +6dB (low shelve)
I am in agreement with doing EQ in an analog way ..

Subjectively I found an output voltage this high is not really needed.
HERE are experiments (using the HD650) showing how much voltages are needed.
With around 5Vrms (7Vpeak) you will be covered but when you want 3dB extra headroom you come back to 7Vrms again.

Passive filtering is a no go in the headphone cable but quite feasable in the line input of an headphone amp.
It needs quite a bit of gain in this case.
This rules out a 1 box solution.

 

[Magnum Innominandum]

At 20Hz you will only need 7dB boost, my 'scientific' evidence (including target response) HERE

I have used the measurements (raw response grey lines) from innerfidelity, which show 20Hz 15dB down on the midband:

The target I want to use is the Harman Target (orange OE2017) which seems well researched and founded in real science:

To get to the above from the measurements by innerfidelity I read off 18dB required boost. Am I doing this wrong?

I will consider your test results as well. However I feel the modifications needed will exceed my capabilities.

If an Amplifier without Bass Boost is used then a passive filter in the line cable may be needed. I do not see why it could not be applied in the headphone cable though. It just needs different RC values, no? Say 100Ohms in series to not loose much power and 10Ohm and 100uF Cap (Nichicon Muses Audio Grade) to ground should create a suitable EQ to do the rest digital. This was recommended to me elsewhere but I am not sure I could assemble this. It would need a lot of output voltage, but I think 7V would still be enough.

Seeing the bass boost on the Oppo HA2 (I might be able to stretch to 299 USD and it looks really good) this seem not suited for HD6XX and the output is too low.

https://audiosciencereview.com/foru...s-of-oppo-he-2-se-dac-and-headphone-amp.4597/

Any better option?

Magnum Innominandum

 

[andreasmaaan]

I have used the measurements (raw response grey lines) from innerfidelity, which show 20Hz 15dB down on the midband:

View attachment 16395

The target I want to use is the Harman Target (orange OE2017) which seems well researched and founded in real science:

View attachment 16396

To get to the above from the measurements by innerfidelity I read off 18dB required boost. Am I doing this wrong?

I will consider your test results as well. However I feel the modifications needed will exceed my capabilities.

If an Amplifier without Bass Boost is used then a passive filter in the line cable may be needed. I do not see why it could not be applied in the headphone cable though. It just needs different RC values, no? Say 100Ohms in series to not loose much power and 10Ohm and 100uF Cap (Nichicon Muses Audio Grade) to ground should create a suitable EQ to do the rest digital. This was recommended to me elsewhere but I am not sure I could assemble this. It would need a lot of output voltage, but I think 7V would still be enough.

Seeing the bass boost on the Oppo HA2 (I might be able to stretch to 299 USD and it looks really good) this seem not suited for HD6XX and the output is too low.

https://audiosciencereview.com/foru...s-of-oppo-he-2-se-dac-and-headphone-amp.4597/

Any better option?

Magnum Innominandum

The bast boost on that Oppo works way up into the midrange - definitely a bad idea for your headphones IMO.

 

[March Audio]

Neither, I liked the HD650 despite the weak bass. Bass can be EQ'ed if the midrange is wrong this harder to fix. So I accepted the weak bass as I knew EQ can be used to fix this.

Magnum Innominandum

Ok, thanks for clarifying.

 

[solderdude]

The thinking is sound. Using Tyll's plots is not the right way... at least not for anything above 1kHz

Rtings measurements show 10dB boost is needed to reach the target.
Sonarworks states +6dB at 30Hz and think +7dB (20Hz) is enough.
There are those that feel (and measure) the HD650 flat to 20Hz and that it does not need any EQ at all.
In my plots the target is already incorporated (+4dB is my target) so a straight line is 'perceived flat at average listening levels.
The 'target response' really is only valid at a certain average SPL.

Also the Harman target plot shown is only valid when the same HATS is used. Tyll's was different

the problem with 'standard' bass boost is that it boosts bass but most likely NOT exactly how you want it.
Custom EQ is the only way.

It cannot be passively done in the headphone cable because A: you loose 6dB and thus your amp would need to reach 14V rms instead of 7V rms to compensate for the loss and B: you would need to use about 330 Ohm in series with the driver. The rather high impedance peak means the bass will get boosted AND sound 'muddy'

 

[March Audio]

I have used the measurements (raw response grey lines) from innerfidelity, which show 20Hz 15dB down on the midband:

View attachment 16395

The target I want to use is the Harman Target (orange OE2017) which seems well researched and founded in real science:

View attachment 16396

To get to the above from the measurements by innerfidelity I read off 18dB required boost. Am I doing this wrong?

I will consider your test results as well. However I feel the modifications needed will exceed my capabilities.

If an Amplifier without Bass Boost is used then a passive filter in the line cable may be needed. I do not see why it could not be applied in the headphone cable though. It just needs different RC values, no? Say 100Ohms in series to not loose much power and 10Ohm and 100uF Cap (Nichicon Muses Audio Grade) to ground should create a suitable EQ to do the rest digital. This was recommended to me elsewhere but I am not sure I could assemble this. It would need a lot of output voltage, but I think 7V would still be enough.

Seeing the bass boost on the Oppo HA2 (I might be able to stretch to 299 USD and it looks really good) this seem not suited for HD6XX and the output is too low.

https://audiosciencereview.com/foru...s-of-oppo-he-2-se-dac-and-headphone-amp.4597/

Any better option?

Magnum Innominandum

Only looks like 10dB down at 20 hz to me.

I have owned 650s and Funnily enough have a pair of 6xx coming from the latest mass drop, due to arrive next week. Getting them as additional test reference for my headphone amp design along with my Oppo PM1. I can try the EQ digitally and see how I find different levels. My memory of the 650s is that it wouldn't require that high a level of EQ, but it will be interesting to try.

 

[oivavoi]

To the OP: you seem to me to have a very rational approach to these things. Kudos. For your needs, I would perhaps look into this for eq: https://diyaudioheaven.wordpress.com/headphones/kameleon/

It comes with a set eq profile for the 650; and is not expensive. Then you need to add a dac to feed it. One of the topping unit seems like a good investment.

 

[RayDunzl]

Only looks like 10dB down at 20 hz to me

I think he takes both of those graphs into account...

The missing bass in the top one, plus the boost in bass in the second for the curve to be emulated (green line).

 

[solderdude]

To the OP: you seem to me to have a very rational approach to these things. Kudos. For your needs, I would perhaps look into this for eq: https://diyaudioheaven.wordpress.com/headphones/kameleon/

It comes with a set eq profile for the 650; and is not expensive. Then you need to add a dac to feed it. One of the topping unit seems like a good investment.

outside of the budget I am afraid...

I could look into designing one passively (in the line level in front of an amp) specifically for HD650 as it does not need a notch filter.
Would probably please a lot of owners...

 

[March Audio]

I think he takes both of those graphs into account...

The missing bass in the top one, plus the boost in bass in the second for the curve to be emulated (green line).

Indeed, which makes 13dB if you use 1khz as your reference. The op wants the orange curve. I am still struggling to reconcile this level of boost with my own experience of the cans. I don't dispute the Harman info, but something is amiss.

Oh and what about Fletcher Munson curves? Volume level needs to be accounted for.

 

[Wombat]

To the OP: you seem to me to have a very rational approach to these things. Kudos. For your needs, I would perhaps look into this for eq: https://diyaudioheaven.wordpress.com/headphones/kameleon/

It comes with a set eq profile for the 650; and is not expensive. Then you need to add a dac to feed it. One of the topping unit seems like a good investment.

Do I assume from that site(by omission) that my DT880s are perfect, or beyond help?

That device could be something different for Amir to test.

 

[solderdude]

No please... no Amir tests ... it would not pass on frequency response, phase response with a filter in it.
The G1217 openframe version is also likely to show mains components in there as well under the wrong circumstances.

DT880 is NOT beyond help at all. check out the DT880 page.

 

[Blumlein 88]

No please... no Amir tests ... it would not pass on frequency response, phase response with a filter in it.
The G1217 openframe version is also likely to show mains components in there as well under the wrong circumstances.

DT880 is NOT beyond help at all. check out the DT880 page.

What DT880 page?

 

[Deleted member 65]

Neither, I liked the HD650 despite the weak bass. Bass can be EQ'ed if the midrange is wrong this harder to fix. So I accepted the weak bass as I knew EQ can be used to fix this.

Magnum Innominandum

This thingie will do the trick for you, right @solderdude ... ;-)

 

[solderdude]

What DT880 page?

This one

 

[Magnum Innominandum]

To the OP: you seem to me to have a very rational approach to these things. Kudos. For your needs, I would perhaps look into this for eq: https://diyaudioheaven.wordpress.com/headphones/kameleon/

It comes with a set eq profile for the 650; and is not expensive. Then you need to add a dac to feed it. One of the topping unit seems like a good investment.

This looks interesting, but I cannot build this. Can I buy something like it anywhere?

Magnum Innominandum