[DeweyCH]

 

[SilverTrumpet999]

With very minor EQ (-3dB at 2.5 kHz) these K340s are now eclipsing both my HE-500 and Ether CX on the THX 789 amp...

I never really EQ'd the others, looking into that to see if they can be made to compete.

 

[Reputator]

Just arrived in the mail today. They look to be in immaculate condition.

Haven't opened them up to see the driver color yet, but I'm getting ready for a first-listen.

EDIT:

Well, first listen, the bass wasn't non-existent. I read even the "bass heavy" version isn't really bassy, and this one seemed to have light but balanced bass, so I thought I MIGHT have got lucky, but...

Nope! Darn.

But that being said, I'm immediately impressed with the treble. For such a vintage headphone, the treble is incredibly detailed and airy. Good soundstaging for an old closed-back too, I'd say.

Can't wait to swap out these earpads though. They're definitely not helping the sound (or comfort).

 

[Mellowship]

Just arrived in the mail today. They look to be in immaculate condition.

Haven't opened them up to see the driver color yet, but I'm getting ready for a first-listen.

EDIT:

Well, first listen, the bass wasn't non-existent. I read even the "bass heavy" version isn't really bassy, and this one seemed to have light but balanced bass, so I thought I MIGHT have got lucky, but...



Nope! Darn.

But that being said, I'm immediately impressed with the treble. For such a vintage headphone, the treble is incredibly detailed and airy. Good soundstaging for an old closed-back too, I'd say.

Can't wait to swap out these earpads though. They're definitely not helping the sound (or comfort).

Those look great! They seem to have been well taken care of by the previous owner.
As for the bass, do not worry. You probably noticed that, in original form, the bass is not of the rumbling kind, you cannot feel it, but on the other hand, you can listen to the details, textures and tones of bassy instruments and you can even guess the weight of it by the enormous quantity of information the K340 are able to transduce. A new set of pads will give you that extra thump. Even cheap pleather substitution pads for AKG K240 from AliExpress will work great in that matter. You should, however, cut off the cloth in the back of the pads as it tends to cut down some "magic" from the electret drive.
If you want them really bassy you can get a set of Defean pads for AKG, which are thicker and have a narrower hole. You will gain some bass, some comfort around the ears (but not ON the ears, as that hole cannot encompass the whole ear inside it), but it comes as an exchange for a smaller soundstage and a somewhat duller presentation.
The thing that really made the difference for me was to convert them in balanced headphones. I had to do it in order to properly amplify them within by budgetary constrictions, using a Loxjie P20. In full balanced mode with this amp, they sing beautifully.
Have fun!

 

[Reputator]

Those look great! They seem to have been well taken care of by the previous owner.
As for the bass, do not worry. You probably noticed that, in original form, the bass is not of the rumbling kind, you cannot feel it, but on the other hand, you can listen to the details, textures and tones of bassy instruments and you can even guess the weight of it by the enormous quantity of information the K340 are able to transduce. A new set of pads will give you that extra thump. Even cheap pleather substitution pads for AKG K240 from AliExpress will work great in that matter. You should, however, cut off the cloth in the back of the pads as it tends to cut down some "magic" from the electret drive.
If you want them really bassy you can get a set of Defean pads for AKG, which are thicker and have a narrower hole. You will gain some bass, some comfort around the ears (but not ON the ears, as that hole cannot encompass the whole ear inside it), but it comes as an exchange for a smaller soundstage and a somewhat duller presentation.
The thing that really made the difference for me was to convert them in balanced headphones. I had to do it in order to properly amplify them within by budgetary constrictions, using a Loxjie P20. In full balanced mode with this amp, they sing beautifully.
Have fun!

I got that sense that the pads were robbing the bass. They don't seal around the ear, and based on my experience with other vintage phones (Stanton Sixties) old pads really rob a lot of the capabilities of the drivers. So that's the first thing I'll do.

Definitely looking through the thread for ideas. Looks like I need to reverse one of the driver plates, the cotton backing like you said needs to be removed, and I can play with maybe converting them to open, but I'm not sure on that one.

But even with the old hardened pads, what's really impressed me is the natural timbre and airy and detailed treble. Honestly the mids sound really good, and if I need more bass, they respond exceptionally well to EQ. I don't feel the need to EQ any of the other frequencies in the stock config. I got no unpleasant peaks from the treble. It's honestly just a really enjoyable top end, the kind of thing a lot of modern highend headphones strive for and still don't get right.

I'm always so impressed when I hear vintage audio sounding so good. With mods, the Stantons sounded like a good $300 modern headphone. Without mods, these easily blow away my memories of the K702. I really couldn't find much to like there, but the K340 is fantastic so far.

 

[Coug]

Being a proponent of reversing a driver plate, I would recommend doing so with bluetack or tape before drilling. See if you like it first.

 

[Reputator]

So I removed the stock pads and measured the diameter, and was surprised to find that it actually matches my Stantons. That means the stockpile of Aliexpress earpads that I already have can work with the K340, which is awesome!

Spoiler

The super cheapy ones shown on the headphones in the first two images is actually the one that sounds the closest to the stock pads. The fit, while not perfect, is a lot better. The pads in the bottom image turn the bass WAAY up to the point of overwhelming the other frequency ranges and taking away from the strengths of the headphone. I think I might actually prefer to keep them "bass light", as it gives a very different presentation to music, and I have plenty of headphones with ample bass if I want.

As @Mellowship mentioned, the bass is present, very well textured, and conveys some sense of weight without actually being elevated. Very interesting. Because the mids are still full-bodied, the K340 doesn't actually sound cold or artificial in any way. The treble is extremely filled out and even, not necessarily in a realistic way, but in a way that for some genres can be pleasing. Again, I'm enjoying how different they are from my other headphones.

Listening to some Mozart last night, that forward treble really brought out the textures of strings and brass instruments, and the separation is just fantastic. I went back to my HEDDPhone, and it honestly sounded muddy by comparison. And while it's not as detailed as the HEDDPhone, this may be due to the higher contrast dynamics on the K340. The HEDDPhone brings the faintest sounds forward, but that can sometimes cause the music to sound more compressed. K340s are borderline shouty at times, but that can sometimes be a good thing on very dynamic recordings, as classical usually is. These seem to be the go-to headphones for that genre of music.

 

[Mellowship]

So I removed the stock pads and measured the diameter, and was surprised to find that it actually matches my Stantons. That means the stockpile of Aliexpress earpads that I already have can work with the K340, which is awesome!

Spoiler

The super cheapy ones shown on the headphones in the first two images is actually the one that sounds the closest to the stock pads. The fit, while not perfect, is a lot better. The pads in the bottom image turn the bass WAAY up to the point of overwhelming the other frequency ranges and taking away from the strengths of the headphone. I think I might actually prefer to keep them "bass light", as it gives a very different presentation to music, and I have plenty of headphones with ample bass if I want.

As @Mellowship mentioned, the bass is present, very well textured, and conveys some sense of weight without actually being elevated. Very interesting. Because the mids are still full-bodied, the K340 doesn't actually sound cold or artificial in any way. The treble is extremely filled out and even, not necessarily in a realistic way, but in a way that for some genres can be pleasing. Again, I'm enjoying how different they are from my other headphones.

Listening to some Mozart last night, that forward treble really brought out the textures of strings and brass instruments, and the separation is just fantastic. I went back to my HEDDPhone, and it honestly sounded muddy by comparison. And while it's not as detailed as the HEDDPhone, this may be due to the higher contrast dynamics on the K340. The HEDDPhone brings the faintest sounds forward, but that can sometimes cause the music to sound more compressed. K340s are borderline shouty at times, but that can sometimes be a good thing on very dynamic recordings, as classical usually is. These seem to be the go-to headphones for that genre of music.

Glad you could find a quick pad fix.
Some people like the velour pads also, but I think they don't help the bass.
That "showty" characteristic you speak of, it comes with no sibilance, which is great. It provides for a lot of information in the upper mids and treble without acoustic annoyance, which means these headphones can be worn without fatigue for hours ( I mean, if they were lighter...).
And I agree these are great for orchestral music. One of the albums that sounded great for me was The Mission soundtrack, by Morricone. Brilliant!

 

[Reputator]

Glad you could find a quick pad fix.
Some people like the velour pads also, but I think they don't help the bass.
That "showty" characteristic you speak of, it comes with no sibilance, which is great. It provides for a lot of information in the upper mids and treble without acoustic annoyance, which means these headphones can be worn without fatigue for hours ( I mean, if they were lighter...).
And I agree these are great for orchestral music. One of the albums that sounded great for me was The Mission soundtrack, by Morricone. Brilliant!

Yeah the velour pads I had surprisingly didn't affect the bass too much, but sucked the warmth out of the mids and elevated the treble, making it sound overly bright and hollow.

And yeah there's zero sibilance with the regular pads. And while they were borderline shouty, I wouldn't call them overly so. "Shouty" is just a common trait of 70s and early 80s headphones, owing to their very dynamic nature. The better ones can control it, and it makes for a fun listen.

 

[Majoox]

There is often talk of a "PCB bypass". However, it is never explained what this means exactly.

When I look at the crossover, two cables go into the PCB, two cables from the PCB to the electrostatic driver and two cables from the PCB to the dynamic driver. Now I connect the two cables "from the outside" directly to the dynamic driver, and leave everything like that?

Due to the fact that a coil and a resistor is installed, it doesn't look like a crossover to me, rather like a voltage regulator for the electrostatic driver. Therefore the dynamic driver is "passed through" and the PCB has no effect on the dynamic driver. Why this modification should be done now is unclear to me, because a few solder joints can increase the resistance, but this is still in the milliohm range.

 

[JadeEast]

There was some conflict in the documentation from AKG back in the day. Below is a write up from the company saying that there is no crossover: however, there is other catalog info that says there is a 6db crossover point at 4khz. I believe, based on some older conversations here the transformer and resister network does roll off the response of the electret driver and bypassing was used to let it run free. I could be mistaken. This was well before enthusiasts were measuring response at home/shop and mods would have been based mostly on subjective testing and experience.

 

[Davidzak64]

I was researching the K340's on this thread and the very next day, Bam! A nearly mint condition set came up on FB and are in my possession. $65 Out the door I ran. They are not nearly as hard to drive as others have stated. I'm driving them with my Topping L30 with some Headroom to spare. So far I'm very pleased with the sound and the bass is much better than I expected. I'll be doing some comparisons with my HE-400i's and HD58X's tonight when I get home from work.

 

[arielext]

Good deal!

 

[Majoox]

Thanks for the answer.

Hmm, apparently the electrostatic elements in my K340 have aged unevenly. A frequency response measurement showed massive differences of over 5 db in some places. I can smooth this out with specific filters and an EQ, but it's still surprising how differently the drivers can age. I can not think of a solution so quickly. When I play Pink Noise from 1,000 to 20,000 Hz it basically sounds centered. Everything is fine with the dynamic driver.

 

[Davidzak64]

So I had a chance to spend some quality time with with my new K340'S and I was blown away by it's level of accuracy in all frequencies. I was almost sure that they were the Bass heavy version but when I took the covers off it revealed the green driver.
These are now my new go to cans. I'm going to spend a little time with them before deciding to do any Mods cause I really can't find any faults except the 2 Khz bump which is easily removed with a slight -1 to -2 db eq adjustment. The other issue I want to correct is replacing the elastic bands. Does anyone know if there is a Video or tutorial for replacing the bands? I would appreciate any advice on opening up the sound stage also. Would removing the driver covers open them up?