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Reversible AKG K701 bass mod - Page 14

post #196 of 202
I am not sure if I misunderstand you. About the b&w nautilus I was thinking about the long tubes that is also a chamber behind the drivers. Try and google "b&w nautilus" and you will see what I mean.
I think this kind of "snailhouse chamber" could be an interesting headphone design. It is all patented by b&w I am sure and therefore all creativity and development stops right there of course.
Quote:
Originally Posted by bluemonkeyflyer View Post

The Q701 Bass Port is actually flared similar to the B&W Nautilus Bass Port. The flare diameter is ~ 2.5 mm and the "tube" is ~ 2 mm.

The stock self-adhesive disk covering the Q701 Bass Ports looks impermeable to me and the glue is very strong.

I tried to modify the tube effect with thin craft felt, 3mm open cell foam, and punching various hole sizes in double-sided tape vs silicone furniture bumpers. The felt and open cell foam had no effect, functioning pretty much like the stock self-adhesive disk. Changing the hole size in silicone furniture bumpers seems to allow for a tunable bass port: smaller = less bass, larger = more bass.

Angle Hair over the ear side of the driver sucks out the lower mids around 500 to 700 Hz by ~ 5 dB.

Removing the stock foam ring on the ear side of the baffle causes even greater suckout by ~ 8 dB.

The best sounding bass port mod to my ears (so far!) results from:

1. Fully open bass port after removing the stock tape disk + add an equal size Arctic Cotton disk overlaying the stock foam disk + Paxmate on the underside of the plastic grille receptacle, only at the bottom, leaving all 4 "vents" fully open (2 small at the top, 2 large at the bottom).

2. Partially open bass port after removing the stock tape disk + silicone disk with 1.5 mm hole placed over the open bass port + self-adhesive craft felt instead of Paxmate, as above.

I have measurements and photos of each mod combination. I will post everything in a new thread this weekend and post a link in this thread for anyone interested.
post #197 of 202
This philosophical approach is allways relevant, no doubt, it makes everyone wake up and think twice.
But I must admit that... well I just really like the k701 with this mod, I think it sounds better this way. And yes akg chose to close this port off with all their expertise, but the thing is, I don't care about that, I disagree with their priorities on this, it still sounds better with this mod.
Quote:
Originally Posted by alphaman View Post

It's important to note that while metrics (objective data/graphs) may, indeed, improve as a result of various mod(s), the actual subjective sound may not correlate to those changed metrics. E.g., flattening of the freq. response may not appeal to all ears (as the ever-controversial diffuse field vs. free field results indicate). 
One particular subjective (controversial) quality is PRAT. I find that even 'phones that display a clean/impressive impulse response may not, in fact, sound as snappy/punchy one that graphically looks (measures) worse. Another unquantifiable is long-term listening -- this may yield subjective results (e.g. listening fatigue) that immediate sonics (or metrics) just can't correlate to. In this case, it's not that objective science is wrong ... rather, it's that currently known-to-human science is missing something ... and may be discovered/quantified by some future da Vinci or Galileo. 
Unfortunately, for logical-fallacy reasons -- like sunk-cost fallacy, etc. -- various mod projects (audio forums are full of them!) gain a sort of "pop inertia" ... like some quaint pop celebrity ... and that may very well be the case with THIS thread. Indeed, as I noted a few posts back ... that AKG was probably aware of the port vs. no-port sonic issue .... and they SELECTED to cover it up after important/informed/well-founded decision metrics.
Hence, with  proposed mod projects , I almost always (now) either ignore or treat them with extreme skepticism ... a lesson that was learned the hard way
post #198 of 202
Quote:
Originally Posted by alphaman View Post
 

It's important to note that while metrics (objective data/graphs) may, indeed, improve as a result of various mod(s), the actual subjective sound may not correlate to those changed metrics. E.g., flattening of the freq. response may not appeal to all ears (as the ever-controversial diffuse field vs. free field results indicate). 

One particular subjective (controversial) quality is PRAT. I find that even 'phones that display a clean/impressive impulse response may not, in fact, sound as snappy/punchy one that graphically looks (measures) worse. Another unquantifiable is long-term listening -- this may yield subjective results (e.g. listening fatigue) that immediate sonics (or metrics) just can't correlate to. In this case, it's not that objective science is wrong ... rather, it's that currently known-to-human science is missing something ... and may be discovered/quantified by some future da Vinci or Galileo. 

Unfortunately, for logical-fallacy reasons -- like sunk-cost fallacy, etc. -- various mod projects (audio forums are full of them!) gain a sort of "pop inertia" ... like some quaint pop celebrity ... and that may very well be the case with THIS thread. Indeed, as I noted a few posts back ... that AKG was probably aware of the port vs. no-port sonic issue .... and they SELECTED to cover it up after important/informed/well-founded decision metrics.

Hence, with  proposed mod projects , I almost always (now) either ignore or treat them with extreme skepticism ... a lesson that was learned the hard way

 

I agree with you, alphaman.

 

Graphs do not necessarily correlate with perceived sound quality. Psychoacoustics is a complicated phenomenon. Many variables come into play: hearing acuity, personal preferences, various forms of bias (positive and negative expectation), placebo, file type, audio gear chain, etc. 

 

Graphs cannot tell us if the headphone will sound good or bad but can provide a peak into the effects of various modifications, if used properly.

 

My graphs (and anyone's graphs) cannot be directly compared to anyone else's graphs. Instead, they must be used relative to the other graphs generated using the same hardware:software system, set-up, and methods by the same individual. Measuring All Stock AKG Q701 serves as the baseline, or reference, against which all other measurements are compared. Each modification can be measured and compared to the baseline to better understand the effects of each particular modification as well as combinations of modifications...or a mod configuration.

 

Measurement graphs should be considered and used as nothing more than tools to improve our understanding of the potential performance and sound quality of various headphones and the modifications we implement. Measurements are easily misunderstood and often misused to "prove" that headphone A sounds better than headphone B... or that modification X sounds better than modification Y.

 

The mod configs I've tried, so far, and like the best don't have the "prettiest" graphs. The graphs, however, provide clues about what's going on with the multivariate interactions of all the acoustic and mechanical variables involved.

 

Boosting Q701's bass via modifications results in improved sound quality without messing with the mids and treble too much, IMO/IME. Each person must draw their own conclusions.

 

Quote:
Originally Posted by Dafo View Post

I am not sure if I misunderstand you. About the b&w nautilus I was thinking about the long tubes that is also a chamber behind the drivers. Try and google "b&w nautilus" and you will see what I mean.
I think this kind of "snailhouse chamber" could be an interesting headphone design. It is all patented by b&w I am sure and therefore all creativity and development stops right there of course.

 

Bowers & Wilkens 803S Flared Bass Port

Each speaker comes with an open cell foam cylinder that can be inserted into the bass port to tone down the bass, much like the adhesive disk over the Q701 bass port.

 

 

I am referring to the hole centered over the back of the driver that's covered by the stock adhesive disk that, when once removed, fully opens the "bass port." Here's a picture of the lower bass driver and bass port of one of my B&W 803S speakers. Note the bass port is flared. The bass port on Q701 is similarly flared. I don't know, however, if the Q701 bass port functions in the same way as in the 803S.

 

Cheers All,

 

~ BMF

post #199 of 202

Just going over some of Tyll's comments, at IF, WRT sealed vs. open. Specifically, he noted that for pro use, important diffs between the sealed Focal Spirit Professional vs. "open" HD800. Not sure the HD800's driver is sealed or ported (like the AKG of this thread). 

I don't own a sealed set (any model) at the moment. So maybe those of you who do can comment on sealed sound (disregarding the isolation issue, of course) vs. open-back.

 

Another thing to explore might be an added sealed chamber connected to that taped port (sort of like closed TDL) ... think crack pipe ;)

post #200 of 202

Since you, bluemonkeyflyer, seem to be interested in modifying the FR curve of the AKG, why not set a goal ...say emulating the notably flat curve of the Philips Fidelio X1...

(above from Tyll's IF)

 

It'd be interesting to see/hear how deliberate curve flattening helps and/or hurts other aspects of AKG stock sound. E.g., dynamics, "speed", slam, punchiness, etc.

Another possible approach to modding the AKG might be experimenting with the side "vents" covered with similar material as rear port ...

...say, use tape to partially cover, with the goal of curve flattening.

post #201 of 202

Done this bass mod on my K702. Definitely more bass but you do lose clarity - which is the main appeal of these headphones to me so I reversed straight away. Listening to Pink Floyd Animals (ALAC) and the change to the guitars clarity was a good test. Can see why this would appeal but seems to change the sound "type" and maybe sound like different headphones. So my opinion is do it if the current sound is not what you are after otherwise dont!

post #202 of 202

Alright, I did it to the right cup and left the other alone on my q701. Despite what everyone says, the bass sounds less loud, but maybe a slightly tighter impact? Comparing the two cups, and switching between ears, the untouched side actually sounds like the bass is louder.  I also think the headphones sound clearer! I don't understand it. I agree with Tdockweiler's review completely! Im not sure if I will convert the other, or undo it.

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