Hoved-fi

Spøg til side, det fungerer rigtig godt, selvom det er sådan lidt... pudsigt, når man tænker over det

This guy took some measurements with the port and rear closed and open.
http://rinchoi.blogspot.nl/2013/08/akg-k702.html#more

It's a K702 but that isn't very different, a tad more bass perhaps

It looks very interesting, but I'm not sure I understand any of it
I thought all the vents would be closed off when it is in stock mode?
So what is "stock" and what is "all rear vents blocked"?
And what is "baffle ring foam" which apparently is removed? The circular piece of tape on the back of the driver is not made of foam?
What am I missing here?

With the vents Rin means the openings in the driver itself.
K702 may have slightly different 'vents' than K701.

with rear vents he means the 'holes' on the back of the driver.
He just tapes them shut and measures what it does.

Baffle ring foam is the ring you see around the business end of the driver.
Plenty of modders have taped some off or glued extra foam over it.
he removed it to see what it does.

He also blocked all the 'holes' in the rear of the driver (which is completely stupid) probably just to 'measure' what happens.

Stock = unmodified headphone (when you bought it) and in the plot he uses this as a 'reference'.
This means it isn't 'flat' as in the picture but as that has become the reference it shows the differences opposite an unmodified one.
Takes some getting used to though.

What is visible though is that the hole in the centre of the driver has a profound influence on the sound in a very small band (1kHz to 5kHz) and shows a change of 6dB opposite an unchanged driver (the grey line).

The guy (Rin) isn't native English speaking and doesn't post pictures of mods nor clear guidelines.

he seems a very busy guy and is totally hung up on 'dr. Oliver'

Never the less, he does some measurements and likes to modify headphones and earphones.

Ok, thank you for explaining
So there seems to be a difference, just not in the bass and according to Rin it's not a "substantial difference".
This could be true. I'm not experiencing a substantial change with the mod, even though there is an audible change, it still sounds like a k701. But it does not sound like a change in the highs. But if you take some of the highs away the lows will come forward... I guess.
I am still a bit confused though as Rin is only talking about "blocking" vents and not about "opening" vents, which seems to imply that "stock" is with the vents open, and thats not at all like my k701.

Are you completely sure that Rin is not only talking about blocking the rear grille and all the other holes around the back of the cup?
That would actually make more sense given the measurements. It's like covering the rear of the cups with your hands, which does make the highs more mute, so to speak.

I am not 100% sure but I know he has a habit of blocking ports and holes in enclosures as well as on the drivers.
I sometimes need to read it twice and look at pictures to see what he means.

With 'open' he could very well mean that there is acoustic paper over the holes.
He generally does not remove that stuff but has a habit of blocking holes and seeing (measuring) what it does.

Read some of his other articles to get a feel of what he is all about.
On the left part scrolling down you can see months/years (it is a blog) and 'open' (drop down) these to see which headphones he measured and played with.

1-2kHz is in the upper mids range.
The typical K701 'peak' is up a bit higher so that won't be affected.
sharp peaks (and even more so dips) are very hard to hear when playing music.
You can 'spot' them using a sweeped sinewave though.

removing highs generally gives the impression there is more lows.

If he means that a hole covered with a rubbery, stretchy, airtight piece of tape is "open" and then puts another piece of tape on top of the other and then calls it closed, then it makes sense. But I'm affraid I don't believe he did.
I think he has been experimenting with different closed-back mods and then measured the results. And then the deffinitions of each mod and the corresponding measurements make sense. I'm also having a hard time admitting that what I heard when I first modded one of the cups, listened with only one side modded and then compared the two, doesn't mean anything. I heard a small but essential change in the bass and nothing else.

Sometimes he does weird things and draws weird conclusions.
On the T50RP he mentions he closes the upper rear port, which doesn't exist as it is taped shut with plastic from the inside.
He measures a tiny difference (so small it could easily come from repositioning the headphone on the rig) and concludes the port was 'open' just a little bit.

The problem is that most of what he does is not documented with pictures and thus is open for interpretation.
The only option that remains is ask him in the reply area.
He will elaborate for sure.

I will ask him right away.

Rin has responded that he hasn't done this mod, which means that the measurings is not of the mod in question, and this also means that my ears are not lying to me

Lets hope he does some measurements on these mods.
The K702 has the same sticker on that hole.
I am really surprised he hasn't removed it and assumed with 'all rear vents' he also meant the center hole.
Given the amount of trouble he has gone through he did not remove that sticker.

That would be great if he did. At least now he knows about it.
It's very easy to misinterpret his terminology. "Back of the driver" should always mean exactly "the back of the driver" and not the back of the cup.
A very interesting blog by the way, thank you for linking to it. Nice to see someone take a look at the Stax basics... very nice readings indeed

Jeg har brug for lidt assistance.. Tænkte jeg skulle modde mine nyankomne K701 - MEN, får ikke det forbandede gitter løs! Eneste jeg har opnået indtil videre er en styg ridse i det hvide plastikhus, fordi redskabet gled af på gitteret. Troede jeg havde en passer, men fandt den ikke, så har prøvet søm, syle, opsprætter og fingre indtil videre. Er det muligt, at gitteret engang var limet fast (denne K701 er fra medio 2010)? Nogen nye forslag til at løsne gitteret?

Hej Ketil,
Jeg har ikke for 5 øre forstand på AKG, men kan denne video hjælpe?:



Edit: det ser bestemt ikke ud til at hans AKG er limet...

Det var, hvad jeg havde planlagt at gøre med passeren. Fandt nu en lignende saks frem og prøvede med den, men gitteret sidder bare bom fast.

Jeg brugte en neglesaks til at dreje med, så den havde fat 2 steder i gitteret.