Sennheiser HD650 & Massdrop HD6XX Impressions Thread
Oct 22, 2017 at 7:15 PM Post #40,021 of 44,467

Bengkia369

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Just invest in a good DAP like the Opus #2 and a good amp, will certainly makes your HD650 sounds very good. For me, I'm using Phatlab Phantasy tube amp to drive my HD650, sounds really awesome.
Please don't use HD650 on the iPhone, it's sounds horrible or buy anything less than the HD650.
 
Oct 22, 2017 at 8:19 PM Post #40,022 of 44,467

DavidA

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@DavidA Why do I say your post makes no sense? Firstly, I stand by my earlier statement that nothing that fits in your pocket will drive Sennheiser HD6XX's like what I good desktop system will, and from what I've read and heard the Xonar Essence sound cards are an excellent headphone DAC/amp. If you really think a Fiio portable DAP is in the same league as a Bottlehead Crack, on that we will forever disagree and there's no point debating. You have your opinion and I have mine. But for the life of me I can't understand why, when a HeadFier is looking for advise on components to drive his premium full-sized headphones you tell them to run out and buy another set of FS headphones :/
Have you even tried a X3ii with the HD650? or some of the other more powerful DAPs ? I used to have a Xonar STX sound card when I was gaming a lot but these days even the cheap Xonar DG & DGX are decent sound cards (I have one of each) and to some of my friends they do sound better than the BH Crack, it just depends on ones preferences, its not my opinion, its the preferences of others.

As to getting a second headphone the op had noted in the original post about getting a Momentum (which I think is decent sounding but way over priced) so for the price of the Mojo I suggested a DAP + headphone and the X3ii is capable of driving the HD650 but it has its own sound when paired with the HD650, it may not be ideal to you but to others it is.
 
Oct 22, 2017 at 11:59 PM Post #40,023 of 44,467

castleofargh

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Go get the new easy to drive Sennheiser HD660S. I consider them as portable.
they quote virtually the same sensitivity while it's apparently half the impedance. that makes the hd660 harder to drive, not easier(needs close to twice the current to get the same voltage/loudness).
 
Oct 23, 2017 at 1:45 AM Post #40,024 of 44,467

pietcux

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they quote virtually the same sensitivity while it's apparently half the impedance. that makes the hd660 harder to drive, not easier(needs close to twice the current to get the same voltage/loudness).
As I have both, my own personal finding is that the HD660S is easier to drive.
 
Oct 23, 2017 at 2:12 AM Post #40,025 of 44,467
As I have both, my own personal finding is that the HD660S is easier to drive.

The Sennheiser HD650 required around 211 mVrms to get 90 dBSPL at 1 kHz, and the HD660S around 107 mVrms for the same. In actual use, I'm getting greater returns from my portable digital audio players (Astell&Kern, FiiO, Sony) with the HD660S than the HD650, in terms of drive and sound quality (to my ears).
 
Oct 23, 2017 at 3:12 AM Post #40,026 of 44,467
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Both the Aune M1s and the Opus #1 does a OK job with the HD650 through their balanced output. Not exactly the Burson V2 but good enough for me to use in the bedroom while reading a nice book :wink:
 
Oct 23, 2017 at 4:50 AM Post #40,028 of 44,467

castleofargh

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The Sennheiser HD650 required around 211 mVrms to get 90 dBSPL at 1 kHz, and the HD660S around 107 mVrms for the same. In actual use, I'm getting greater returns from my portable digital audio players (Astell&Kern, FiiO, Sony) with the HD660S than the HD650, in terms of drive and sound quality (to my ears).
200mV for 90dB into the hd650 is right, I get about that too and Tyll also. but Senn's page quotes
Sound pressure level (SPL) - 104 dB at 1V 1kHz
for the 660, and we've had 103dB at 1V for the 650 for ages. so yeah, half the voltage needed says 6dB more sensitive, not 1.

still if impedance isn't just as wrong, we end up with half the voltage and twice the current, so about same total power.

@pietcux you've make a discovery ^_^.
 
Oct 23, 2017 at 5:20 AM Post #40,029 of 44,467

pietcux

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200mV for 90dB into the hd650 is right, I get about that too and Tyll also. but Senn's page quotes for the 660, and we've had 103dB at 1V for the 650 for ages. so yeah, half the voltage needed says 6dB more sensitive, not 1.

still if impedance isn't just as wrong, we end up with half the voltage and twice the current, so about same total power.

@pietcux you've make a discovery ^_^.

As we say:
The truth lies on the match field.
 
Oct 23, 2017 at 10:08 PM Post #40,031 of 44,467
That counts roughly to 104 dB@1V HD 650 and 109 dB@1V HD660s Could official data be wrong?

I presented our measurements to Axel Grell, and he did say ours was correct. The 1 dB sensitivity difference (between the HD650 and HD660) shown on Sennheiser's website is incorrect.

Is it unusual for Sennheiser to understate the sensitivity?
(I know AKG at least has overstated the sensitivity of K701/2)

Since we're on the topic of headphone sensitivity specs...

I know we're always looking to find firm answers in numbers and lines, but sometimes (most of the time) it's not as simple as it seems. Some things to consider:
  • I'm not exactly sure how Sennheiser measures sensitivity.

  • Do they measure sensitivity at EEP (ear entry point) or DRP (drum reference point)? (We measure at DRP.) Where one measures in this regard will affect sensitivity measurements.
ERP-EEP-DRP.png
  • New pads? Old pads? In our case they were new, and, of course, Sennheiser would certainly spec with new pads. I'm only mentioning this because if someone else is measuring the headphone with older pads, it will make a difference.

  • How tight was the headband set? If it's an independent measurement, is it an old headband that's a bit more broken-in with lower caliper pressure than a brand new headband? (The HD650 and HD660S we measured are still like-new.) These things affect sensitivity measurements. (More on this shortly.)

  • Sennheiser (especially with their high-end headphones) has some of the best channel-matching in the industry. I visited their factory in Tullamore (Ireland) years ago, and I observed how they took great care to match channels with the HD600. Still, no matter how well they do, slight variations will occur between channels.

    In fact, even after our analyzer sets the level to 90 dBSPL, the measured level drifts up and down (in tiny amounts) despite the unwavering 1 kHz sine wave it's being fed. The level from the microphone doesn't just lock in at exactly 90.000 dBSPL with those numbers to the right of the decimal point not moving or drifting -- again, those numbers drift, even while inside an acoustic/vibration isolation enclosure in a quiet room. Also, just leaving the headphone on the measurement head for a time can cause earpad compression (again, affecting the measurement).
The values in my post above were taken from the output voltage indicator of the analyzer. The headphone amp used in those measurements was the Rupert Neve Designs RNHP which, prior to the measurement session, we set to unity gain (hand-set via the volume knob, but done while monitoring gain on the Audio Precision audio analyzer). To illustrate how much all of the above (and other) variables can affect sensitivity measurements, we just did the following:
  • We calibrated our GRAS measurement microphones with a pistonphone, adjusting for temperature and ambient static pressure.

  • We swapped-in the Audio Precision APx1701 Transducer Test Interface (in place of the Rupert Neve Designs RNHP). The APx1701 contains calibrated instrument-grade amplifiers, and it "talks" directly with our audio analyzer, so I'd be more apt to trust the voltage level set and indicated with this combination than the hand-set Neve RNHP.

  • We put the Sennheiser HD650 on a GRAS KEMAR measurement manikin after setting the HD650's headband size to nine clicks out of each side, and asked the system to set the output level to 90 dBSPL at 1 kHz.

    • With nine clicks out of each side, the HD650 achieved 90 dBSPL at an output level of 210.9 mVrms.
    • At eight clicks out, it required 195.9 mVrms.
    • At six clicks out, it required 188.0 mVrms.

  • We put the Sennheiser HD660S on the measurement manikin.

    • At nine clicks out of each side of the headband, it took 127.7 mVrms.
    • At eight clicks out, it required 119.9 mVrms.
    • At six clicks out, it required 111.4 mVrms.
I know it's way too late at this point to say "long story short," but the point of all of this is that sensitivity specifications are really more of a guideline, and perhaps the manufacture-provided numbers are most useful when comparing to their sensitivity specs for their other models.

What about comparing sensitivity specs of different models between different manufacturers? Grains of salt abound. Assume for a moment two headphones from two different manufacturers that have exactly the same sensitivity at a given frequency (usually 1 kHz) -- if one manufacturer measures sensitivity at DRP and the other at EEP, expect the headphone measured at EEP to have a sensitivity spec that's higher than the DRP-measured one by perhaps a few decibels. And then there are all the other variables we've covered.

Of course, headphone sensitivity specs can be useful, but do keep all of the above in mind when you see them.
 
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Oct 24, 2017 at 12:48 AM Post #40,033 of 44,467

jimmers

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Thank you for that very interesting and thorough description of your measurement procedures.
It's hard to imagine Sennheiser don't also take care of their measurements and they publish 1V 1kHz sensitivities for the two headphones that are only 1dB apart, maybe a typo?
 
Oct 24, 2017 at 12:55 AM Post #40,034 of 44,467

castleofargh

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I know we're always looking to find firm answers in numbers and lines, but sometimes (most of the time) it's not as simple as it seems. Some things to consider:
  • I'm not exactly sure how Sennheiser measures sensitivity.

  • Do they measure sensitivity at EEP (ear entry point) or DRP (drum reference point)? (We measure at DRP.) Where one measures in this regard will affect sensitivity measurements.
  • New pads? Old pads? In this case they were new, of course. I'm only mentioning this because if someone else is measuring the headphone with older pads, it will make a difference.

  • How tight was the headband set? That affects sensitivity measurements. (More on this shortly.)

  • Sennheiser (especially with their high-end headphones) has some of the best channel-matching in the industry. I visited their factory in Tullamore (Ireland) years ago, and I observed how they took great care to match channels with the HD600. Still, no matter how well they do, slight variations will occur between channels.

    In fact, even after the analyzer sets the level to 90 dBSPL, the level drifts up and down (in small amounts) despite the unwavering 1 kHz sine wave it's being fed. The level from the microphone doesn't just lock in exactly at 90.000 dBSPL with those numbers to the right of the decimal point not moving or drifting -- again, those numbers drift, even while inside an acoustic/vibration isolation enclosure. Also, just leaving the headphone on the measurement head for a time can cause earpad compression (changing the measurement).
The values in my post above were taken from the output voltage indicator of the analyzer. The headphone amp used in those measurements was the Rupert Neve Designs RNHP which, prior to the measurement session, we set to unity gain (hand-set via the volume knob, but done while monitoring gain on the audio analyzer). To illustrate how much all of the above (and other) variables can affect sensitivity measurements, we just did the following:
  • We calibrated our measurement microphones with a pistonphone, adjusting for temperature and ambient static pressure.

  • We swapped-in the Audio Precision APx1701 Transducer Test Interface for the Neve RNHP. The APx1701 contains calibrated instrument-grade amplifiers, and it "talks" directly with our audio analyzer, so I'd be more apt to trust the voltage level set and indicated with this combination than the hand-set RNHP.

  • We put the Sennheiser HD650 on the measurement manikin after setting the HD650's headband size to nine clicks out of each side, and asked the system to set the output level to 90 dBSPL at 1 kHz. It achieved this at an output level of 210.9 mVrms.
    • At eight clicks out, it required 195.9 mVrms.
    • At six clicks out, it required 188.0 mVrms.
  • We put the Sennheiser HD660S on the measurement manikin, and at eight clicks out of each side of the headband, it took 127.7 mVrms.
    • At eight clicks out, it required 119.9 mVrms.
    • At six clicks out, it required 111.4 mVrms.
I know it's way too late at this point to say "long story short," but the point of all of this is that sensitivity specifications are really more of a guideline, and perhaps the manufacture-provided numbers are most useful when comparing to their sensitivity specs for their other models.

What about comparing sensitivity specs between different models of different manufacturers? Assume for a moment two headphones that have exactly the same sensitivity at a given frequency (usually 1 kHz) -- if one manufacturer measures sensitivity at DRP and the other at EEP, expect the one that measures at EEP to show greater sensitivity by perhaps a few decibels. And then there are all the other variables we've covered.

Of course, headphone sensitivity specs can be useful, but do keep all of the above in mind when you see them.
I admit I'm biased on this. the brand name absolutely changes the way I read the specs. I always keep a huge headroom for Hifiman because several times they were quoting sensitivities wayyyyyy too high compared to the pair I had to try(as in, all the measurement factors added together in the same direction would still make it look suspicious). I don't trust Audeze because of how often they would modify a series while leaving the same name. but this is Sennheiser, I expect more consistency. the same way I expect it from Etymotic. I was going to say even more for a flagship, but it just occurs to me that the 660 is not it.
anyway, TBH I only have a few anecdotes to justify my views, so I'll leave in objective shame. ^_^
 
Oct 24, 2017 at 1:47 AM Post #40,035 of 44,467

Shoewreck

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Did Sennheiser change the way they do their measurements? Two headphones with similar (yet not identical) everything except impedance do measure 5-6dB apart (that's absolutely expectable, given 2x impedance difference) on @jude 's equipment, but only 1dB apart according to official specs.
 

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