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blargh4 t1_jec7ql0 wrote

Like all these receivers/boomboxes, the headphone jack is a bit of afterthought and does not have a dedicated amplifier, but uses the speaker amp going through a resistor. The resistor causes the amp's output level to be very sensitive to variations in the headphone's impedance at different frequencies, which for most dynamic driver headphones gives you a midbass "boost" (though what's really happening is that it's struggling to drive the other frequencies at the same level). It also reduces the control the amp has over the movement of the driver, but I'm not sure to what extent this has an audible effect. You can get the same effect with an impedance adapter dongle.

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FourOpposums t1_jecyn6v wrote

HD560 and high-end Sennheiser headphones in general are high ohm headphones, built in / designed for a time when people still used their stereo headphone jacks which use resistors as you describe

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rhalf t1_jediyzf wrote

HD560s is not very high-ohmic. It's in the middle. It's definitely not designed for high impedance outputs. 120 ohm or (whatever it has) is around the output of many of those headphone outs. Also the HD500 line has been 50ohm since I remember.

Portable amps with automatic gain read HD560s as a low impedance load.

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FourOpposums t1_jedjjpm wrote

I know they are 120 ohms and not 300 ohms like HD600/650 but I would not consider 120 to be a low ohms headphone. More generally, it is an explanation for why they sound better out of OPs moderately high output impedance headphone jack.

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rhalf t1_jedk4un wrote

To me it's more like these things are unrelated. The guy likes the sound, but it's not how they were designed. You get more bass and it changes the image, but that's a different tuning.

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FourOpposums t1_jedkrya wrote

Fair enough you do make a good point, I just don't agree with you lol. By OPs description of the sound I would prefer it too and that convinces me that they are functioning very well.

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blargh4 t1_jedrcwp wrote

Yeah, it was a reasonable/effective solution before low-impedance cans became more of the norm (presumably with the rise of the walkman/discman, where for similarly cost-sensitive reasons you'd rather need higher currents than higher voltages).

While it may flatter the Sennheisers, a few hundred ohms of output impedance will have much less agreeable effects for a lot of cans/IEMs, so I just want to assure OP that his headphone dongle is behaving as a modern headphone amp ought to.

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