Beyerdynamic DT 770 Pro 80 Ohm to Audio Source matching

[Page Rumbles]

Hello everyone, how is everyone doing, I'm new to the forum and I have a question regarding headphone - amplifier (interface) matching.

 

I have a pair of Beyerdynamic DT 770 PRO 80 Ohm on a loan.

 

My audio source is the Audio kontrol 1 by NI USB interface.

 

The specs for the headphone output are:

Load impedance: 8 ... 600 Ohms

Maximum Output Level: 4.26 V rms, 100mW @ 100 Ohms

(Other specs in the enclosed picture)

 

I am interested whether it is safe (and correct) to use the headphones in this setup. I understand that the 80 ohm impedance falls into medium impedance territory, but cannot for the life of me figure out if it is safe or a match to use them with my audio interface. 

 

My understanding at the moment is that the load impedance is in this case basically the headphone impedance or in other words the values of headphone impedance that my interface can work with. In theory that would mean it can work with both very low and very high impedance headphones.

 

Is my understanding correct? I'm worried I might damage the headphones. What should I be careful about to avoid damaging the headphones (any headphones really)?. I would like to use the 1/8 impedance rule in this case, but I can't determine the output impedance from the specs from the interface. 

 

Thank you for your help

 

 

 

[opus101]

Your 80ohm HPs will do just fine driven by this device as the range is 8 to 600 ohms. They'll also play extremely loud if fed by 4VRMS so I'd be more concerned about ear damage than HP damage.

 

HPs are most at risk from being accidentally driven with DC - you may want to check if your HP amp has DC protection built in.

[Page Rumbles]

Thanks for answering. So if 4v RMS is a lot. isn't it then possible to overload them and damage them? Or is this just on extremely high listening levels. Also, can the 1/8 impedance rule be applied in my scenario?

[opus101]

4VRMS is a lot for 80ohm HPs in terms of SPL but only a couple of hundred mW so not likely to damage them. The 1/8th impedance rule is just a rule of thumb for indicating the highest source impedance which is likely to work well. Your specs don't say what the output impedance is so I can't tell if its violated or not.

[John Dyson]

I just checked some graphs online that show the SPL vs. freq vs. source impedance 0ohm, 60ohm and 300ohm, and the frequency response difference looks to be very small (just attenuated at the higher impedance as expected.)   I ended up with similar information from various sources.

 

Another set of measurements from a different standpoint, the headphone load impedance has a peak at around 80Hz (about 1dB) and an impedance trend upwanrds above 10kHz by about 1dB.   So, with higher source impedances will have an attenuated loudness, but will have a little boost at 80Hz and trend upwards a little starting at 10kHz.   The 1dB number is the maximum increase based upon an infinite impedance source, so with a lower than infinite impedance source, the increases at 80Hz and beyond 10kHz will be less than 1dB.

 

Of course, there are other secondary effects also -- like a lower impedance will likely drive the device more accurately, so MIGHT have lower distortion at a given SPL.

 

I got info from various sources (similar/same models), and the characteristics appear similar.

 

The second set of raw numbers that I am talking about are at this location: (look for the brown curve on the left hand frequency response curves.)   The brown curve shows the loading vs. frequency  -- relatively flat, close to 1dB as measured on other curves.

https://reference-audio-analyzer.pro/en/report/hp/beyerdynamic-dt-770-pro-80.php#gsc.tab=0

 

The 600ohm version appears similar in behavior about loading.   Of course, driving with a higher source impedance will result in lower levels (the Pro80s are measured at 90 ohms load.)

 

Bottom line:  varying the source impedance on a Beyerdynamic DT770/Pro80 isn't deadly.   I drive mine with 10ohms.

 

John