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AKG K712 Pro Review (Headphone)

amirm

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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:


AKG K712 Pro Review Open Back Headphone.jpg


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:
best open back headphone review.png


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:

AKG K712 Pro Measurements Frequency Response Open Back Headphone.png


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:
AKG K712 Pro Measurements Relative Frequency Response Open Back Headphone.png


Distortion is very good at lower levels:

AKG K712 Pro Measurements Distortion Precentage Open Back Headphone.png


AKG K712 Pro Measurements Distortion Open Back Headphone.png


Impedance at 1 kHz is same as advertised but is variable:

AKG K712 Pro Measurements Impedance Open Back Headphone.png


Bass tuning is at 100 Hz and hence the reason response drops below that.

AKG K712 Pro Measurements Impedance zoomed Open Back Headphone.png


They are not very sensitive so you definitely need a headphone amp:
Most sensitive headphone tested.png


Group delay is reasonable in balance:

AKG K712 Pro Measurements Group Delay Open Back Headphone.png


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:

AKG K712 Pro Equalization EQ Parametric Filter Open Back Headphone.png


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.

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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/
 

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solderdude

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I got quite similar results with such a deep dip around 3.5kHz and *think it is audible as a lack of clarity. (K712, K7XX)
(My bass correction is not as extreme and 'sharp' as Harman)

k712-vs-k7xx.png


Thanks for measuring these.

I noticed you found sensitivity is 107dB/V where mine is 102dB/V but then realized you measure at 420Hz and mine was at 1kHz. At 1kHz it is down 5dB opposite 420Hz.

Edit: *was a remnant I forgot to remove after editing some text before hitting the submit button.
 
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sweetchaos

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To import this PEQ profile into 'Equalizer APO', use:
Preamp: -9.3 dB
Filter 1: ON PK Fc 30 Hz Gain 8.0 dB Q 1.0
Filter 2: ON PK Fc 1350 Hz Gain 6.0 dB Q 2.0
Filter 3: ON PK Fc 3394 Hz Gain 9.0 dB Q 3.0
Otherwise, see my PEQ guide.
..................................................................................................................
For those who don't have PEQ-capable app, and want to use GEQs instead:
See my GEQ guide for 10-band, 31-band, and 127-band GEQ profiles.
 
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tktran303

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@solderdude

Is the 712 a variant of the 702; as far as you can tell?

Coz that 701/702 has been around for about 2 decades IIRC; well before AKG was acquired by Harman. and it sounds like what as Amir measures this one- limited sub bass bass; airy sparkling highs but annoying on certain material…
 
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solderdude

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The K712, K702 (with K712 pads) and K7XX all differ a bit so they aren't exactly the same driver/baffle it seems.

k712-bn-vs-k7xx-gn-vs-702-with-7xx-pads-pu.png
 
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xaviescacs

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At some point I was considering these to replace the 701, which clearly doesn't make any sense. As a read more headphone reviews here (edit: and on @solderdude's site) I get more convinced there is not point on buying based on amateur or pro reviews without measurements.
 
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ernesternest

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The AKG712 Pro, that Solderdude measured, accidently was mine and at the date of measurement it had been in charge for about two years before that.
When it was new, I didn't like it that much and just used it daily for listening to spoken text, yet it turned into a better better hp by age.
Meanwhile I use it for Music as well, even without EQ, when my ears got hot form K731 ;-).
So its age might be one part of the reason for different curves.
 

staticV3

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A mini XLR socket is provided which you can use to create balanced or unbalanced connection.
The K712 uses a 3pin Mini XLR jack, so unfortunately balanced operation is impossible out of the box.
You can however replace that with a 4pin jack to make it compatible with balanced Amps.
If done correctly, this mod is 100% seamless.
Photos:
IMG_20210615_171937__01.jpegIMG_20210615_172342.jpg
 
OP
amirm

amirm

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The K712 uses a 3pin Mini XLR jack, so unfortunately balanced operation is impossible out of the box.
You can however replace that with a 4pin jack to make it compatible with balanced Amps.
If done correctly, this mod is 100% seamless.
Photos:
View attachment 166602View attachment 166603
Oh, my sample must have had that conversion done. I was wondering why the stock cable would not fit it.
 

krumpol

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The AKG712 Pro, that Solderdude measured, accidently was mine and at the date of measurement it had been in charge for about two years before that. [..] So its age might be one part of the reason for different curves.
AKG also closed its manufactury in Vienna, Austria four years back, new batch of K712 Pro is manufactured in Slovakia now.
 

pavuol

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AKG web: "The K712 PROs are reference, open, over-ear headphones for precise listening, mixing and mastering."
Amir: "open back (gaming?) headphone"

Amir correcting both its category classification and FR curve :D

Back in the days I remember considering these to buy as praised middle class HPs, well, back in the days.. :rolleyes: I still like its design and detachable cable. Also, way lower distortion than DT990 looks nice.
 

staticV3

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One curiosity with the K712 is the insane price for replacement ear pads.
The headphone itself is 222€ in Germany right now and a new pair of pads will set you back another 100€.
 

ZolaIII

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@solderdude seams K702 (with stock or memory foam K712 pads) is a winner from those three. As I don't like deep between 1 to 2 KHz, K7XX resolves it but with boost in lows and you again get a overlap in male vocals.
 

Luke

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I sold my K712 when I realised the pads alone cost £100 haha
I think the K612 is tuned better and the pads are more reasonably priced too :)
 

solderdude

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Oh, my sample must have had that conversion done. I was wondering why the stock cable would not fit it.

Aside from not fitting (pin 4 preventing that) the pinning is also very different. (picture from Hart cables)

pinning.png
 

PeteL

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I got quite similar results with such a deep dip around 3.5kHz and think it is audible. (K712, K7XX)
(My bass correction is not as extreme and 'sharp' as Harman)

k712-vs-k7xx.png


Thanks for measuring these.

I noticed you found sensitivity is 107dB/V where mine is 102dB/V but then realized you measure at 420Hz and mine was at 1kHz. At 1kHz it is down 5dB opposite 420Hz.
You "think" a 12.5 dB drop on about an octave bandwidth is audible?
Edit: Oh I would assume you probably mean post EQ, if so apologies for the sarcastic nature of the comment.
 
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JJB70

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I have always found the classic AKG design incredibly comfortable, I can wear these all day. Light weight, low pressure and the self adjusting design works superbly. The only issue (which isn't trivial) is the faff when the elastic bands break. Soundwise I quite liked these and found them very agreeable for the most part.
 

FrantzM

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The competition is strong in the area; unless you really want this particular AKG, there are better headphones at same/similar prices... IMO, DCA, Sennheiser, HiFiMan comes to mind.
Peace
 
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