This is a review and detailed measurements of the AKG K712 Pro open back (gaming?) headphone. It is on kind loan from a member and costs US $327 on Amazon.
I find the K712 cute and cheerful:
The huge cups (64mm inside diamater/24mm deep) fit over my ear fine. But I thought the cups didn't compress enough and after a while, I could feel their slight pressure on head. Ditto for the headband. I would rate it as 90% comfortable.
Plastic components help keep the weight lower:
A mini XLR socket is provided which you can use to create balanced or unbalanced connection. I used the aftermarket nice twisted cable the owner had supplied.
Note: The measurements you are about to see are made using a standardized Gras 45C. Headphone measurements by definition are approximate and variable so don't be surprised if other measurements even if performed with the same fixtures as mine, differ in end results. Protocols vary such as headband pressure and averaging (which I don't do). As you will see, I confirm the approximate accuracy of the measurements using Equalization and listening tests. Ultimately headphone measurements are less exact than speakers mostly in bass and above a few kilohertz so keep that in mind as you read these tests. If you think you have an exact idea of a headphone performance, you are likely wrong!
The large cups made an easy job of mounting them on my fixture and getting good measurements on first try.
AKG K712 Pro Measurements
Let's start with our usual frequency response measurements:
Compliance with our target is only in the 200 to 500 Hz (I calibrate to 420 Hz). Very hard to imagine what they were thinking in the response between 500 Hz and 5 kHz. There is massive shortfall. We also have the usual bass droop.
Relative response shows that we need very large compensation at 4.5 kHz:
Distortion is very good at lower levels:
Impedance at 1 kHz is same as advertised but is variable:
Bass tuning is at 100 Hz and hence the reason response drops below that.
They are not very sensitive so you definitely need a headphone amp:
Group delay is reasonable in balance:
AKG K712 Pro Listening Tests and Equalization
I only listened for a minute before reaching for EQ. It sounded very closed and improper to me out of box. EQ development is a bit challenging due to troughs not matching the shape of a parametric filter. Still, I lucked out and with just three filters massively improved the response:
High level of filter amplitude causes easy clipping so I had to pull the overall levels down which means you need even more drive from your amplifier. I also could not push the bass enough as distortion would set in. As is, deep bass was good with EQ.
I really enjoyed the spatial qualities that equalization brought to these large drivers/cups. Turning off the EQ made this collapse. As usual, this is caused by lack of energy in the 2 to 5 kHz without EQ.
Conclusions
I was very surprised at the response of this headphone. I looked up the announcement data and it was 2013. I think Harman had already performed its headphone research by then. So I have to think the AKG folks were not on board with it in development of K712 Pro as it doesn't remotely comply with their preference curve. And if any headphone needs to comply with that standard is the K712. It is impossible to make a case that you want to filter out all the music spectrum in 1.3 and 3.4 kHz!
I can't recommend the K712 Pro without EQ. With EQ, I am not super happy with deep bass response but spatial qualities are good enough to push me to put it on my recommended list.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I find the K712 cute and cheerful:
The huge cups (64mm inside diamater/24mm deep) fit over my ear fine. But I thought the cups didn't compress enough and after a while, I could feel their slight pressure on head. Ditto for the headband. I would rate it as 90% comfortable.
Plastic components help keep the weight lower:
A mini XLR socket is provided which you can use to create balanced or unbalanced connection. I used the aftermarket nice twisted cable the owner had supplied.
Note: The measurements you are about to see are made using a standardized Gras 45C. Headphone measurements by definition are approximate and variable so don't be surprised if other measurements even if performed with the same fixtures as mine, differ in end results. Protocols vary such as headband pressure and averaging (which I don't do). As you will see, I confirm the approximate accuracy of the measurements using Equalization and listening tests. Ultimately headphone measurements are less exact than speakers mostly in bass and above a few kilohertz so keep that in mind as you read these tests. If you think you have an exact idea of a headphone performance, you are likely wrong!
The large cups made an easy job of mounting them on my fixture and getting good measurements on first try.
AKG K712 Pro Measurements
Let's start with our usual frequency response measurements:
Compliance with our target is only in the 200 to 500 Hz (I calibrate to 420 Hz). Very hard to imagine what they were thinking in the response between 500 Hz and 5 kHz. There is massive shortfall. We also have the usual bass droop.
Relative response shows that we need very large compensation at 4.5 kHz:
Distortion is very good at lower levels:
Impedance at 1 kHz is same as advertised but is variable:
Bass tuning is at 100 Hz and hence the reason response drops below that.
They are not very sensitive so you definitely need a headphone amp:
Group delay is reasonable in balance:
AKG K712 Pro Listening Tests and Equalization
I only listened for a minute before reaching for EQ. It sounded very closed and improper to me out of box. EQ development is a bit challenging due to troughs not matching the shape of a parametric filter. Still, I lucked out and with just three filters massively improved the response:
High level of filter amplitude causes easy clipping so I had to pull the overall levels down which means you need even more drive from your amplifier. I also could not push the bass enough as distortion would set in. As is, deep bass was good with EQ.
I really enjoyed the spatial qualities that equalization brought to these large drivers/cups. Turning off the EQ made this collapse. As usual, this is caused by lack of energy in the 2 to 5 kHz without EQ.
Conclusions
I was very surprised at the response of this headphone. I looked up the announcement data and it was 2013. I think Harman had already performed its headphone research by then. So I have to think the AKG folks were not on board with it in development of K712 Pro as it doesn't remotely comply with their preference curve. And if any headphone needs to comply with that standard is the K712. It is impossible to make a case that you want to filter out all the music spectrum in 1.3 and 3.4 kHz!
I can't recommend the K712 Pro without EQ. With EQ, I am not super happy with deep bass response but spatial qualities are good enough to push me to put it on my recommended list.
-----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
