Sennheiser HD650 & Massdrop HD6XX Impressions Thread
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dakanao

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Isn't the cost of 2 USB isolators + Black Dragon more than the cost of a HD650? Seems like a waste of effort/funds to get them to sound good on a Mojo to me, just my opinion but wouldn't it be easier to get a DAP (for portable use) or DAC+amp that didn't need the USB isolators and I'm one that doesn't believe that headphone cables makes any audio difference that I or any of my friends and family could hear.
Yes it is, but the Mojo itself is also more expensive than the HD650. I also got 2 other headphones that sound fantastic with the same setup.

The Mojo isn't thin and bass light by itself, it's just needs shielding from RF/EMI to perform it's fullest, and to me it is a noticable and endgame upgrade from the Mojo stock, even though the additional gear is a bit expensive.
 
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Deftone

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How does the Mojo sound thru SPDIF? SPDIF has no RF/EMI.
Its also galvanicly isolated so no noise coming in from the source as well like usb, its a smoother treble but without the bass boost like @dakanao gets with with his jitterbug and usb cable. Any extra bass would be too much imo because the mojo already sounds rich in the mid bass with roll off in upper treble and sub bass. Its not a flat reference type of sound.
 
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auronthas

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Hi, please comment if there's any error in headphone/IEM SPL, power, voltage, current calculation to determine how difficult headphone/IEM to drive.

Also, may i know what is the "norm" desired listening level ?

Headphone SPL calculation.png
 
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Hi, please comment if there's any error in headphone/IEM SPL, power, voltage, current calculation to determine how difficult headphone/IEM to drive.

Also, may i know what is the "norm" desired listening level ?

Sensitivity should be SPL dB @ 1V rms, and efficiency as SPL dB @ 1mW

From previous investigation I can say that the comparison* between the HD650 and the K701 is way off, for the same SPL dB the K701 needs ~1.5 times more voltage and ~ 7.5 times more current so ~ 11 times more power than the HD650, others will liikely be incorrect.

* Using the measurements by Tyll at Innerfidelity, actual measurements on the same test rig as opposed to manufacturers unspecified numbers
 
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auronthas

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Sensitivity should be SPL dB @ 1V rms, and efficiency as SPL dB @ 1mW
Indeed, I used both sensivity and efficiency formula to generate the power, voltage and current required based on desired loudness @110 dB



From previous investigation I can say that the comparison* between the HD650 and the K701 is way off, for the same SPL dB the K701 needs ~1.5 times more voltage and ~ 7.5 times more current so ~ 11 times more power than the HD650, others will liikely be incorrect.
The K701 data I got from their specification as you mentioned may be biased …

* Using the measurements by Tyll at Innerfidelity, actual measurements on the same test rig as opposed to manufacturers unspecified numbers
I am not denied it.
 
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"Desired loudness" 110db??????????????????
 
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dakanao

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Its also galvanicly isolated so no noise coming in from the source as well like usb, its a smoother treble but without the bass boost like @dakanao gets with with his jitterbug and usb cable. Any extra bass would be too much imo because the mojo already sounds rich in the mid bass with roll off in upper treble and sub bass. Its not a flat reference type of sound.
I would imagine the Mojo to sound the same with optical, as with the isolated setup I have with USB.

The bass doesn't actually get boosted, it's just that distortion noise in the uppermids/treble gets taken rid off, and so the bass gets more defined in impact because of that.
 
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Hi, please comment if there's any error in headphone/IEM SPL, power, voltage, current calculation to determine how difficult headphone/IEM to drive.

Also, may i know what is the "norm" desired listening level ?

this might help http://www.apexhifi.com/specs.html
if you click on the excel picture, you can download the file and use it with your own values to check or just see what operations he's using in the spreadsheet.
 
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"Desired loudness" 110db??????????????????
Exactly I was wondering why http://www.apexhifi.com/specs.html used 110db as desired loudness. In my post earlier, i asked what's the "norm" of desired listening level.

If we lower down desired loudness, the required power to drive the headphone will be reduced too, right?
 
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Exactly I was wondering why http://www.apexhifi.com/specs.html used 110db as desired loudness. In my post earlier, i asked what's the "norm" of desired listening level.

If we lower down desired loudness, the required power to drive the headphone will be reduced too, right?
the loudness picked is a personal matter. ideally you'd pick a worst case scenario for yourself. I never listen to music very loud, and happen to have a way to measure the SPL out of my headphone, so I know what I need and have absolutely no need for some amplifier with a disproportionately huge gain into my headphone. but I use some EQ and replay gain and those have to be accounted for. so the actual signal is often 10 to 15dB(for modern tracks at least) below digital full scale. meaning that even if I aimed for 90 or 95dB SPL which is really the loudest I'm going to listen at night in my room with my HD650. 95dB is a level I can need when I measure the headphone so it's a nice limit for me. I still have to consider a safety margin of... maybe not the 10 or 15dB because I don't measure stuff with replaygain, and only about half the time with some EQ in the signal path. so maybe 6 to 8dB for some worst gain compensation from EQ, leaving me with a target of max loudness of at least 95+8 dB SPL. I'm confident that I would leave just fine with that. it might bot be the case for somebody else who enjoys music as loud as if he was at a concert(and some do).
a different approach could be to consider that 115 or 120dB is where sounds start to cause pain to most listeners. so there might not be any reason to get a lot more.
some people think that more is pretty much always better, or they have their own safety margin over what's already a safety margin. I don't have many headphones and I absolutely hate having a hard time setting my desired listening level with a volume knob that makes music too loud before even reaching 9 o'clock(plus some have serious channel imbalance in that area of the knob, and the higher the gain, the more likely it is for background noise to also increase). that's why I avoid stuff that are clearly too powerful for my needs. unless they have convenient gain settings, or I can ask the manufacturer to lower those gain values before sending the amp to me.

anyway, the average Joe might not know how loud he's listening to music, and he might have no reliable way to know. I suspect that it's a big reason why people tend to consistently pick the more powerful amp among those they were considering. and it's hard to blame them, because while too much power can cause issues, not being able to get music as loud as we want is always bad news.
 
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auronthas

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the loudness picked is a personal matter. ideally you'd pick a worst case scenario for yourself. I never listen to music very loud, and happen to have a way to measure the SPL out of my headphone, so I know what I need and have absolutely no need for some amplifier with a disproportionately huge gain into my headphone. but I use some EQ and replay gain and those have to be accounted for. so the actual signal is often 10 to 15dB(for modern tracks at least) below digital full scale. meaning that even if I aimed for 90 or 95dB SPL which is really the loudest I'm going to listen at night in my room with my HD650. 95dB is a level I can need when I measure the headphone so it's a nice limit for me. I still have to consider a safety margin of... maybe not the 10 or 15dB because I don't measure stuff with replaygain, and only about half the time with some EQ in the signal path. so maybe 6 to 8dB for some worst gain compensation from EQ, leaving me with a target of max loudness of at least 95+8 dB SPL. I'm confident that I would leave just fine with that. it might bot be the case for somebody else who enjoys music as loud as if he was at a concert(and some do).
a different approach could be to consider that 115 or 120dB is where sounds start to cause pain to most listeners. so there might not be any reason to get a lot more.
some people think that more is pretty much always better, or they have their own safety margin over what's already a safety margin. I don't have many headphones and I absolutely hate having a hard time setting my desired listening level with a volume knob that makes music too loud before even reaching 9 o'clock(plus some have serious channel imbalance in that area of the knob, and the higher the gain, the more likely it is for background noise to also increase). that's why I avoid stuff that are clearly too powerful for my needs. unless they have convenient gain settings, or I can ask the manufacturer to lower those gain values before sending the amp to me.

anyway, the average Joe might not know how loud he's listening to music, and he might have no reliable way to know. I suspect that it's a big reason why people tend to consistently pick the more powerful amp among those they were considering. and it's hard to blame them, because while too much power can cause issues, not being able to get music as loud as we want is always bad news.
I get what you mean...

In short the ideal and perfect headphone/amplifier matching is important so not to miss any music details as per the Master Records and at tolerable listening level.
 
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