Modding the K340...

[SonicDawg]

For a long while I have my K340 slightly modded (cable, xover bypass, grill replacement, decottoning, that is, lol). To my dislike, the K340's (bass heavy version) retain a quite recessed nature on the top end, and I seem not be able to get a good frequency balanced from them, despite good performance on the rest of the frequency spectrum. Today, after reading up on Aerius's old post about bi-wiring the drivers here, and feeling a bit antsy and yet adventurous, I went on and replaced the original xover wires with some silver plated copper hookup wires. While the process was EXTREMELY painstaking and delicate, considering how little solder space it is between the electrat unit and the xover unit, and the miniscule voice coil wires connected to the xover wires that tend to MELT IF IT GETS TOO HOT, I wholeheartedly believe that I have once again upped the performance of my dearly mangled K340's

The trebles are much improved, though being still a bit soft, are much more pronounced than before the mod, and truly shine now. The top end remains soft and smooth, but much more balanced. If anyone feels the need to squeeze out the one last bit of his K340's, especially of the bass heavy variant, I recommending going through with a few hours of extreme stress (I having a drunken sailor's hands didn't bode well with such a delicate process) and let the phones truly present their glory

 

[jbloudg20]

Quote:

Originally Posted by SonicDawg For a long while I have my K340 slightly modded (cable, xover bypass, grill replacement, decottoning, that is, lol). To my dislike, the K340's (bass heavy version) retain a quite recessed nature on the top end, and I seem not be able to get a good frequency balanced from them, despite good performance on the rest of the frequency spectrum. Today, after reading up on Aerius's old post about bi-wiring the drivers here, and feeling a bit antsy and yet adventurous, I went on and replaced the original xover wires with some silver plated copper hookup wires. While the process was EXTREMELY painstaking and delicate, considering how little solder space it is between the electrat unit and the xover unit, and the miniscule voice coil wires connected to the xover wires that tend to MELT IF IT GETS TOO HOT, I wholehearted believe that I have once again upped the performance of my dearly mangled K340's The trebles are much improved, though being still a bit soft, are much more pronounced than before the mod, and truly shine now. The top end remains soft and smooth, but much more balanced. If anyone feels the need to squeeze out the one last bit of his K340's, especially of the bass heavy variant, I recommending going through with a few hours of extreme stress (I having a drunken sailor's hands didn't bode well with such a delicate process) and let the phones truly present their glory

I noticed quite a gain when I did this to my pair, which also is the bass heavy version.

 

[nelda]

I shall remember this.
I always feel the same too. But on some recording, it seems OK. for instance, Michael Jackson, Craig David, Gomez etc the highs are there but on some recording, it sounds really veil/dark or whatever you called them.

So it is recording or is it my K340? I believe mine is bass heavy version.

 

[SonicDawg]

I think overall it's just the warm sound signature of K340 that makes some recordings sound really dark. But having done the mod, I believe the frequency balance is much better IMO. One thing I noticed, though. Trebles in far off distance tend to sound more "veiled", while nearer instruments sound much more clearer. This is true before and after the mod. I tend to think that's an advantage of K340 to present good distance cue with accurate attenuation of HF.

 

[philodox]

So you wired silver to the electrets and copper to the bass drivers?

 

[SonicDawg]

That is correct, sir

 

[philodox]

Nice... I would imagine that sounds very nice with the bass heavy version. I think it might make my highs a little harsh though.

 

[SonicDawg]

It may be true. I have always wanted to hear the treble-oriented version of the K340, but now I think now I have come to a pretty good medium

 

[Xanadu777]

Out of over 40 pairs of K340's I've heard, not one I would call bass heavy. Lets look at the dynamic "bass" driver...

I decided to break out a pair of mine for some over the top tweaking not too long back. In the pic, the electret is shown upside down on the left. Notice the cone shape center that goes directly over the dynamic driver. The sound reflects out and under to the edges of the electret where 5 passive drivers direct (and affect) the sound upwards towards your ears. These can be tuned with cotton damping in the chamber behind them.

Now size isn't everything, right? True, but these (gray center in this pic) bass drivers are a puny 30mm (Grado is 45mm, AT is 52mm). At 640 ohms, not easy to drive, electret is 1835 ohms but the transformer coil brings that down to 685 ohms. I thought they'd run in series connecting directly to the dynamic, but they seem to be set up in parallel as the overall ohm reading is around 335 when connected this way (same as stock). Had I thought about it much, that would make sense as the volume after modding doesn't change at similar settings. The "bypass" mod, simply bypasses the stock short steel wire, solder connections and PCB traces. No surprise why it sounds better this way. Much easier for AKG to take the short cut of wire to connect their cable outside of the cups.

I was curious on what percentage of sound we hear from both drivers and was a bit surprised. The electret puts out a very small percentage of the overall sound. I tried them both out on their own from all contact points and in stock housing with just dynamic detached. At loud listening volume, you can barely hear them. I broke out another pair for the identical test (I have 3) just to make sure these weren't just tired (they weren't). So the electret, in my estimation, puts out very soft highlites above 5Khz basically only, aprox less than 5% (or less) of the overall sound you hear (by volume). Basically, it adds a faint bit of direct high end, to go along with the reflecting spectrum. It is a part of what makes K340's sound like they do, but way less than I ever imagined.

On to the dynamics. I took them out and made a mini headphone out of just them. I wanted to see how much of K340 sound I could get from them. They are nice sounding little dynamics, especially considering when they were made. They have a nice midrange, high end is not bad, but they don't have bass I would call heavy (adequate under the right circumstances). Not many cans do though. By this I mean compared to real live music. By what I read sometimes, I suspect that some peeps may not have ever experienced real, live music (any form, not just concert style). That aside, they would sound nice with a little tweaking paired with a bass driver, haha... These little dynamics produce 95% of the volume you hear IMO. The overall design of K340's plays a part on the sound itself, depending on how you tweak it. Hard to put a percentage on that, maybe up to a third.

Onward... I ditched the stock bass driver and have tweaked the mount to accept a Grado "bass" driver, at the same level as stock. I have them on and ready to go. I'm not finished putting them back together, so no results are known to me yet. I suspect I will be happy! I am real curious on how the overall design will sound with the Grado drivers (electrets will still be used). Comparing the stock AKG sound to how they sound on their own, I see no reason why I shouldn't like the result.

The K340 was a fantastic set of cans in it's day, and still is worthy to tweak. Hopefully, my time will have been well spent with the current mods I'm doing for possibly another way to enhance them into a contender for my rare listening time. Not sure I covered everything, back to work time though...

 

[swt61]

Wow! That sounds like an awesome mod. I'm dying to hear your impressions after everything is tweaked. Very interesting about the electrets, I would have thought they accounted for much more of the total output. You know what will happen if you post really good impressions of the Gra 340's though, you'll have lots of people wanting that mod.

 

[philodox]

Interesting findings, but when listening to just the electret wouldn't the impedance be way off? Also, are you measuring the actual impedance or the resistance? I measured the resistance of each side of my pair and it came out to 337 ohms. I have no way to measure the impedance with the equipment I have though.

 

[jbloudg20]

Quote:

Originally Posted by philodox Nice... I would imagine that sounds very nice with the bass heavy version. I think it might make my highs a little harsh though.

Not to my ears... but then again I am a fan of the 325i, which everyone else states as being harsh and overly bright.

Amd very impressive, Larry!

 

[TheSloth]

I'm not so sure about how little the electret does. According to the AKG tech docs, the acoustic crossover sets in at about 4k, 6dB per octave, meaning that the electret is responsible for just about everything above 4kHz. Additionally, when I first received my pair of K340's, one of the electrets was dead - the sound was obviously missing the entire upper frequency spectrum.

 

[Xanadu777]

I'll stick to that dynamics put out 95% of the VOLUME and the rest of the K340 design responsible for up to a third of the sound. So for sound only, that's 66% dynamic, 33% electret and passive design.

The electrets kick in at aprox 5k (though it's gradual), could be 4k if that's what specs say. Take away the sparkle of the electrets and you would certainly be able to tell. Take away both electrets and they would again sound balanced, with high frequencies intact. Intact in the sense of what they produce, not compared to adding the electrets on top.

I would guess that a similar affect of how they sound by themselves could be achieved by cutting all frequencies on an EQ below 4-5k and take a listen. Not much there volume wise...

Regardless, my intent is in changing the dynamics to something with some low nut clank so I might want to listen to mine instead of keeping them in a box

 

[PsychoZX]

Quote:

Originally Posted by Xanadu777 Regardless, my intent is in changing the dynamics to something with some low nut clank so I might want to listen to mine instead of keeping them in a box

Stick a PS-1 Driver in there.