Reversible AKG K701 bass mod
Oct 27, 2017 at 4:44 AM Post #331 of 394

xxAMAROKxx

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I have never removed stick on my K701, but have experience with Sennheiser HD-449. They have similar stick on the back of the driver.
- By removing it, the bass is much stronger, but it destroy soundstage and details are not acuurate.
- If I use foam intead of stick, the bass is still stronger, but sound is muffed in general.

If someone need more bass or less treble, this is good option: https://www.head-fi.org/threads/reversible-akg-k701-bass-mod.660408/page-22#post-13576147
 
Oct 27, 2017 at 9:57 AM Post #332 of 394

Beagle

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Neat.
 
Jan 6, 2018 at 6:05 AM Post #333 of 394

Hitashi

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A common complaint about the AKG K701 which I share is a lack of bass, or rather of bass impact/punch. Listening to a Beyerdynamic Dt 880 I can hear and FEEL just the right amount of deep bass, with the K701 I just hear it.

On a german speaking forum somebody posted a completely reversible, easy to do mod which alledgedly increases the bass. It is as simple as removing a small piece of felt or something glued on the middle bassreflex.



Wrap this piece in polysthene foil so you can later easily undo the mod if you wish to. Here's another picture showing the small piece that has to be removed:




Has anybody yet tried this? I sadly can't for myself, as I don't own a pair :) But it would be interesting to know if this actually works.

Even if the mod is said to be reversible: try at your own risk only. Not of my invention, so kudos and all credits to the "inventor". Original thread: http://www.hifi-forum.de/viewthread-211-474.html

I have a AKG K702, i did this mod yesterday, it did change the sound signature a whole lot, for the better, the harsh peak at 2.2khz and the trebble peaks around 6-10khz were less agressive sounding. What people don't seem to understand, is the relative SPL, if you increase SPL in the bottom, you have effectively reduced the mid/highs.

The bass does become bloated so much that you have to dampen the headphone using some cotton into the the chassis, where the arrows point to 2418128.jpg


But i would recommend taming this headphone using Parametric EQ, using ASIO bit-perfect direct connections, try out Jriver, and use these parametric EQ settings, it will sound like a very linear floorstander. and yes, definately use this mod, it really tames the driver, removes a good deal of the peaky aggressive harsh nature of the driver, then use my EQ settings ( i have a background in DIY high-end crossover builds for Loudspeakers ) This EQ will work with the modded K702

267hz
Q = 0.59
-1,6 dB

1111 hz
Q = 1,15
+0,69 dB

2265 hz
Q = 0.91
-5.43 dB

7105 hz
Q = 1,84
-3.96 dB
 

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Jan 7, 2018 at 5:49 AM Post #334 of 394

xxAMAROKxx

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I have a AKG K702, i did this mod yesterday, it did change the sound signature a whole lot, for the better, the harsh peak at 2.2khz and the trebble peaks around 6-10khz were less agressive sounding. What people don't seem to understand, is the relative SPL, if you increase SPL in the bottom, you have effectively reduced the mid/highs.
I`m courious about soundstage. Is it wider now? And what about accuracy of instrument location?

I`m thinking of some sort of this mod in invisible version:
https://www.head-fi.org/threads/akg-q701-vs-akg-k702-comparison-review.594927/page-9#post-8147720
- It gives some borders to the soundstage. Music becomes not so airy.
- Adds a bit of body to music.
- But also adds some unwanted sibilances
 
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Jan 8, 2018 at 6:20 AM Post #335 of 394

Hitashi

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me borders to the soundstage. Music becomes not so airy.
- Adds a bit of body to music.
- But also adds some unwanted sibilances

Doesn't add " a bit of body " after doing the bass mod, i had to remove the low shelf filters, the mod itself add's +2 dB in the bottom, at the very least.
It does not add unwanted sibliance, since you add more bottom, the already sibilant headphone seems much less sibilant.

this headphone have giant spikes between 5-10 khz .. it's not 'airy' it's harsh and sibilant peaky sound..! Take a look at the frequency response for crying out loud..
https://www.rtings.com/headphones/1-1/graph#332/1184

Don't believe Innerfidelities graphs, they are in the woods.

Soundstage does narrow a bit after doing the mod, the bass became too loose for my taste, so i dampened the room with some cotton, it gives the perfect blend between stock and bass mod, insert the cotton with tweezers like on the image.
2418128.jpg
 

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Mar 13, 2018 at 5:38 PM Post #336 of 394

Shoewreck

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I tried the mod on K712. Lots of deep bass, the everything seems cleaner and bigger.
Very impressive with electronic music (i.e. Infected Mushroom - Groove Attack) and metal (Ihsahn - Disassembled). Stereo effects, definition - it's all there, just bigger and more powerful. True basshead delight.
Great solo female vocal (Dead Can Dance - The Wind That Shakes the Barley (Live)). It was not the voice that was affected, but the sense of surrounding space.
There is a saying that Jazz sounds good on almost anything. Not the case: Antoine Fafard - E+3. Bass just overpowers and pushes guitar away. Lighter rock (Fleetwood Mac - Second Hand News) and bass-rich pop (Bjork - Army Of Me) show the same kind of imbalance: vocals sound small and distant, overpowered by tremendous low end.
Last test track that many think is bass-heavy left me disappointed. Opeth - Sorceress. Bass guitar wasn't overpowering, despite having a solid foundation. And it was feeling like lacking coherence.

Finally I put the stickers back. This sort of bass made me feel like I'm going deaf. Very deep, very powerful, but there is still no true bass sensation. Like speaker systems use multiple transducers for different frequencies, human hearing doesn't fully rely on ears. You need to shake your body, not eardrums, to feel the lowest bass notes. Raised lows also mask details in music (it's a fault of human hearing, not a headphone) - that's the reason why modded units sound cleaner. That's probably the reason why AKG kept making bass light headphones for so long: this way you're hearing more detail without stressing your eardrums with sounds you're not hearing properly in a headphone.
 
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Mar 14, 2018 at 2:29 PM Post #337 of 394

xxAMAROKxx

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Doesn't add " a bit of body " after doing the bass mod, i had to remove the low shelf filters, the mod itself add's +2 dB in the bottom, at the very least.
It does not add unwanted sibliance, since you add more bottom, the already sibilant headphone seems much less sibilant.

I was exploring only tissue mod, never did bass mod.

From some point, I`m using only Equalizer for K701. More db from 500 to 1000 Hz and Less db from 10 to 16 kHz (but its due to tubes). And more Bass of course.
Spikes from 5 to 8 kHz doesn`t bother me.

I bought K701 for instrumental and new age music and they are great for these, without any mod or EQ. But for most other music, good equalizer is necessary. (EQ in ASUS center is very bad. Using AIMP EQ now).
 
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Mar 30, 2018 at 2:55 PM Post #338 of 394

DiamondPilot

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I did the mod on a K701. I found it to add a subtle but noticeable boost to the low bass. As others have alluded, it seems like dampening is removed and the bass notes can breathe and articulate better.

However, it increased the bass distortion. Maybe the reason AKG put the stickers over the port is that the driver needs to be dampened a bit to limit distortion.

I have a new pair of K701s without the mod, and a broken-in pair (~300 hours) with the mod. So, I was able to A/B simultaneously to confirm these observations by plugging both pairs into the 2 headphone jacks in my Saffire Pro 40.

Furthermore, I can confirm that break in on these headphones is no myth, and not the result of my brain or ears becoming accustomed to their traits, as some hypothesize. Before doing the mod, I did the A/B test between both the unmodded but broken in and the unmodded and never played pairs, and noted that the sound is much smoother, more open, with a more articulate bottom end on the broken in pair. Both sets were the Chinese versions, purchased together, and with near serial numbers.
 
Apr 4, 2018 at 6:17 PM Post #339 of 394

sekim

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I ended up designing a Baxandall inspired bass boost circuit that is placed in my headphone amp. I modeled the sound I wanted using my studio software and then used LT Spice to model the circuit needed to duplicate in hardware the boost curve I built in software. Works really well and totally changed the listening experience from not using a boost. I decided on this route after reading a couple of posts where EQ was preferred by the posters over the port mod. DiamondPilot's post above also leads me to believe this is probably the better way to go if you can do DIY electronics (or can access high quality software EQ). Would be happy to post a schematic and response curve if anyone is interested...
 
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Apr 8, 2018 at 6:17 AM Post #340 of 394

bluemonkeyflyer

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I ended up designing a Baxandall inspired bass boost circuit that is placed in my headphone amp. I modeled the sound I wanted using my studio software and then used LT Spice to model the circuit needed to duplicate in hardware the boost curve I built in software. Works really well and totally changed the listening experience from not using a boost. I decided on this route after reading a couple of posts where EQ was preferred by the posters over the port mod. DiamondPilot's post above also leads me to believe this is probably the better way to go if you can do DIY electronics (or can access high quality software EQ). Would be happy to post a schematic and response curve if anyone is interested...

Interesting. Please post.
 
Apr 9, 2018 at 10:34 AM Post #341 of 394

sekim

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Interesting. Please post.

Here you go. I placed the bass boost circuit between the vol pot and the input opamp of this headphone amp circuit (which is a very good sounding piece IMO): http://sound.whsites.net/project113.htm. If you build a separate bass boost box, it would go between the DAC analog out and the analog input of headphone amp. I would use hand matched components for the resistors and caps, especially in the bass boost circuit, as well as identical component construction. (I used hand matched cap values but one was a poly and the other a stacked film and the channels sound a little different, enough so that I'm going to retrofit them later). I used LME49720 for the opamps.

I tuned the circuit from the perspective of someone who mixes music in a studio, with the goal of being able to mix as much as possible in headphones and then very quickly do a final mix on studio monitors. That said, you may or may not like the sound of this for general listening, IMO it borders on sounding a little too fat for general listening, especially if you like the normal K701 sound. But I can usually get a good mix quickly that will translate to most any playback system when I mix with this sound, hence the tuning of both this and my open monitor system. Changing C1 to .056uF and R2 to 22K will give it a more "linear" sound at the expense of obscuring a bit of detail in the lows. Its tuned for the early Austrian built AKG K701 (and my preferences). As usual, this is JMO, YMMV, etc, etc. Another option is to just build a Baxandall which of course is adjustable, which is what I started with here. Once I determined a curve I liked for mixing, I wanted it non-adjustable since it serves as a reference for my purposes, and that allowed me to simplify the actual circuit.

Also, if you have software that can do it, you can get very close to the curve below using a 6dB per octave low shelf. That will allow you to audition something very close to the sound of the posted circuit before building it. The reason I don't use soft EQ for this full time is because I also do a lot of general listening, and soft EQ'ing a 16 bit source and then re-normalizing it to -.1dB so it doesn't clip the DAC requires very good software, which I have but its a pain to use for general listening. This soultion allows zero alteration of the source bits at full resolution to go to DAC without clipping issues - meaning any playback software or device is fine. Enjoy.

K701_bass_boost.JPG
 
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Apr 13, 2018 at 1:05 PM Post #342 of 394

bluemonkeyflyer

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Thanks for sharing. I need to order bits from mouser and give it a try.

Another approach is solderdude's Kameleon headphone amp with the corresponding filter module that sounds very good. It's easy to build and allows you to build filter modules for other headphones.
 
Apr 13, 2018 at 2:14 PM Post #343 of 394

sekim

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Thanks for sharing. I need to order bits from mouser and give it a try.

Another approach is solderdude's Kameleon headphone amp with the corresponding filter module that sounds very good. It's easy to build and allows you to build filter modules for other headphones.

Not surprising to see others doing something similar, it is quite effective and a fairly obvious solution. For the one I posted I'd probably start with the fatter version (.047 / 33K as posted). The more I listen to the fat version the more I like it even for general listening. The alternate version (.056 / 22K) is letting the K701s truncate the lowest regions of some material. Of course jme (just my ear), jmo, ymmv... Update on the caps I mentioned earlier: I was able to hand match a set with same construction and they sound great.
 
Apr 13, 2018 at 4:48 PM Post #344 of 394

Shazb0t

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I just performed the bass port mod on my pair of Q701s that I've had for several years. The change isn't drastic, but I definitely think that it improves the bass and brings the headphones closer to a neutral sound. Bringing up the bass effectively lowers the treble and makes these headphone less bright sounding. I dig it so far!
 
Sep 23, 2018 at 7:51 AM Post #345 of 394

dhruvmeena96

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After a day with this mod, I can see why some people prefer "colored" headphones. The standard K701 is just... too flat, too clean, and no bass impact, which translates to NO FUN for a lot of people.

I can't believe I'm saying this now, but I'm listening to Rock music with K701 and I ENJOY it. The mod definitely boosted certain frequencies that make the bass and drums sound DELICIOUS. This is done without sacrificing K701's famous soundstage.

The only cost is imaging. I may not have an un-modified K701 to compare, I still have my HD800. I'm very well aware of the differences between an unmodified K701 and HD800. The unmodified K701 and HD800 are like two gentlemen sipping tea. The modified K701 is the once gentleman ripping off his suit.
Modified AKG k701 sounds like unrefined HD820 to me.
But this is still a steal

But the real steal is akg k551 mod by solderdude. Nailed everything(I did to my akg k550mk3)

Its like AKG k501 mids + akg k701 soundstage + no roll off bass from a closed back.

It will remind you of k701 on mid bass(before mod) but surprising factor is the subbass extension.. Damm
 

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