Importance of impedance? Senny HD25

2ndtimelucky

Well-Known Member
Got a set of HD 25 cans for Christmas to use for dj-ing and home listening. Running from my mac they sound great, different level compared to my old things.

Unfortunately using them on my Denon mixer last night they struggled to get even close to my old phones in output level before distortion...

Noticed today that my old 'phones are 16 ohm while the HD 25 are 70 ohm, could this be the problem?

Many thanks in advance :)
 
I looked at the specs on the Sennheiser site and noticed no actual spec for sensitivity. The text only mentions "high sensitivity", so there is no real way to be sure. I suppose if the output impedance of the Denon is in the 50 - 75 Ohm range and there is little drive current available, the 70 Ohm Z of the 25s could be the problem. Have you checked the specs on your mixer headphone output?

Cheers
 
Cheers for the reply, the denon spec sheet says:

Headphone Output/Impedance 1.0v/32ohm

Not sure how this translates to sound quality or 'output power'???

I must add though that output wise the Sennheisers are brilliant off the Mac and my other laptop, even from my phone.

Maybe the Denon just has a rubbish headphone stage?? Hope not as it's an expensive bit of kit :D
 
Headphone Output/Impedance 1.0v/32ohm

Making a couple of assumptions, it seems the output of your Denon is a little anemic.
First, I'll assume the spec is such that the Denon can develop 1Vrms max across a 32 Ohm load. Assuming, for calculation purposes, the 32 Ohms is purely resistive, this results in about 30mW output into 32 Ohms. With your 16 Ohm phones this would be about 60mW - not great, but workable with sensitive phones.
With the Sennheisers at 70 Ohms, output power would be reduced to about 15mW. Sennheiser usually specs their sensitivity referenced to 1Vrms. Again, in the assumption mode, your Denon would provide only about half what is needed to achieve the rated (but unknown) sensitivity SPL of the Senns. So, your HD-25s are getting about 1/4 the power of your older phones.

Again, this is only an estimate based on some assumptions. If correct, this would explain the low levels you are experiencing.

Not a fix, but maybe it sheds some light on your situation.

Cheers
 
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