Sennheiser HD650 & Massdrop HD6XX Impressions Thread
Oct 24, 2017 at 11:44 PM Post #40,037 of 44,480

mindbomb

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It would be a 3db difference if 2 headphones were otherwise the same but one was half the impedance. However, I would think that with 1+ tesla magnets being standard now in 2017, that efficiency would have risen and the difference being even greater than 3db (like what Jude found). Instead, sennheiser says the difference is smaller.
 
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Oct 25, 2017 at 6:55 AM Post #40,038 of 44,480

denis1976

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hello i don't know if this allready has been discussed but the efficiency of db/1v and db/1mw makes a huge diference
 
Oct 25, 2017 at 11:31 AM Post #40,040 of 44,480

rexhu100

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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.
  • 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 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 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 (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 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 GRAS pistonphone, adjusting for temperature and ambient static pressure.

  • We swapped-in the Audio Precision APx1701 Transducer Test Interface (in place of the Ruper 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.

Cool! Very technical yet useful.
 
Oct 25, 2017 at 1:24 PM Post #40,041 of 44,480

denis1976

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Generally sensitivity is with respect to Voltage, which we have been comparing, and efficiency is with respect to Wattage.
what i meant is that for exemple the ie800 everybody saying that they are very easy to drive, and yes they are not very dificult to drive but 125db/1v in normal measurement that other brands use is for exemple 110db/1mw that is in real world more efficient than the ie800
 
Oct 29, 2017 at 8:08 AM Post #40,042 of 44,480

RiseFall123

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Hi,

Sorry for the weird question, according to your experience about these two scenarios:

A) iphone>Tidal>hd650 (WITHOUT any amp)

B) iphone>Tidal>another lower impedance/high sensivity over-ear (Momentum, Fidelio, etc)

The A solution is far worse than the B or the HD650 will sound simply not at their best but will compete with the second (more appropriate) solution?

In other words, do you will buy another more easy drive over-ear or the difference is so minimal that you would stick 650 even WITHOUT an amp?
 
Oct 29, 2017 at 8:41 AM Post #40,043 of 44,480

castleofargh

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Hi,

Sorry for the weird question, according to your experience about these two scenarios:

A) iphone>Tidal>hd650 (WITHOUT any amp)

B) iphone>Tidal>another lower impedance/high sensivity over-ear (Momentum, Fidelio, etc)

The A solution is far worse than the B or the HD650 will sound simply not at their best but will compete with the second (more appropriate) solution?

In other words, do you will buy another more easy drive over-ear or the difference is so minimal that you would stick 650 even WITHOUT an amp?
what's the voltage output of an iphone nowadays?

if loudness isn't an issue, do you like the signature and comfort of the hd650 more than the signature of a momentum? there is your answer. ^_^
 
Oct 29, 2017 at 9:12 AM Post #40,044 of 44,480

RiseFall123

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It’s never been clear (to me) the real output values of an iPhone. But, now i owe one that has built in jack but the next i will buy (before or later) will be without the built in jack but with a littoe adapter so i assume the output will ve even weaker.

I luke everything about hd650 including their “open” style but still curious about what i asked before.
 
Oct 29, 2017 at 10:02 AM Post #40,045 of 44,480

RickB

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It’s never been clear (to me) the real output values of an iPhone. But, now i owe one that has built in jack but the next i will buy (before or later) will be without the built in jack but with a littoe adapter so i assume the output will ve even weaker.

I luke everything about hd650 including their “open” style but still curious about what i asked before.

Perhaps you should look at the new Senn HD660S. That is 150 ohm and will be easier to drive from portable devices.
 
Oct 29, 2017 at 10:49 AM Post #40,046 of 44,480

TYATYA

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Hi,

Sorry for the weird question, according to your experience about these two scenarios:

A) iphone>Tidal>hd650 (WITHOUT any amp)

B) iphone>Tidal>another lower impedance/high sensivity over-ear (Momentum, Fidelio, etc)

The A solution is far worse than the B or the HD650 will sound simply not at their best but will compete with the second (more appropriate) solution?

In other words, do you will buy another more easy drive over-ear or the difference is so minimal that you would stick 650 even WITHOUT an amp?

Tidal is not a relate thing. Iphone to hd650 or iphone to another hp (exam momentium), depending on budget you plan for it. Over ear hp is not a small size thing, so how about inserting a mojo dac amp to your stack?
Hd660 is one option too. It may same budged
 
Oct 29, 2017 at 12:08 PM Post #40,047 of 44,480

raybone0566

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Perhaps you should look at the new Senn HD660S. That is 150 ohm and will be easier to drive from portable devices.
Not much easier. I own both and on my ZDS I'm roughly at 9 o'clock with the 650's and about 10 til with the 660's
 
Oct 29, 2017 at 12:57 PM Post #40,048 of 44,480

RickB

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Not much easier. I own both and on my ZDS I'm roughly at 9 o'clock with the 650's and about 10 til with the 660's

Not something I know much about, but if the ZDS is an OTL, then it will always work better with a higher impedance headphone. I'm guessing that on a solid state amp, the HD660S would be easier to drive.
 
Oct 29, 2017 at 1:22 PM Post #40,049 of 44,480

raybone0566

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Not something I know much about, but if the ZDS is an OTL, then it will always work better with a higher impedance headphone. I'm guessing that on a solid state amp, the HD660S would be easier to drive.
The ZDS has hi & low output switch. I've also got a sa amp & it was pretty much the same. I've got friends who have both and they feel the same. I'm not keeping mine as I can justify the cost. They are more similar than not.
 
Oct 29, 2017 at 1:23 PM Post #40,050 of 44,480

RickB

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The ZDS has hi & low output switch. I've also got a sa amp & it was pretty much the same. I've got friends who have both and they feel the same. I'm not keeping mine as I can justify the cost. They are more similar than not.

Fair enough.
 

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