[spike33]

My oehlbach 120ohm adapter arrived today, it's suppose to boost bass and tame highs on certain beyer models. I tried it out with 501 and WHOA, there's alot more bass! I thought I was imagining things so I compared a bit with and without adapter and there's definately more bass with it. Has anyone tried this and reached same conclusion?

 

[wallijonn]

There can' t be more bass - there can only be a perception of more bass at the expense of the high end. The K501 is one of the few headphones which has two resonance peaks - one at the low and one at the high. So if anything it should recess the midrange even more.

When I used resistors to change the overall impedance of the headphones there was miniscule change - but I added mine in parallel and not in series.

 

[spike33]

You could be right that mids and highs are lowered to give perception of more bass, but nonetheless, there's more bass.

friend came over to try it. I asked him which one he liked better. He said the one with 120ohm adapter. I asked him why. He said there's more bass, its more fun.

 

[JaZZ]

Frequency response should be modified according to the graph below:

Meaning: mild mid-bass hump at ~100 Hz and upper-treble increase.

[Edit: graph exchanged and comment modified; I catched the wrong graph because the title characters in the HeadRoom PDF are almost unreadable.]

 

[spike33]

awesome, so I wasn't imagining it, it really does add bass

 

[WmAx]

Quote:

Originally Posted by spike33 awesome, so I wasn't imagining it, it really does add bass

Here is a measured acoustic response(3.5 Z source vs. 122.5 Z source) that illustrates the difference(s) to be expected within the bass range and treble range:

*Note that the K501 used in this measurement has modified pads installed. While this is true, it only affects a narrow band in the midrange. The relative bass and treble response shown here is valid, in a relative capacity.

-Chris

 

[wallijonn]

-Chris,

Your 3.5 Ohm reference point says that you will have 3.5 ohm resistors in parallel to the 120 Ohm (MINIMUM at 20 Hz) headphones. In effect you have turned them from 120 Ohm headphones into 4 Ohm speakers. That can't be right.

In my case I used 12 ohm resistors because I was using the x0.1 factor. It would seem that you are doing a 0.029 factor. That can't be right.

http://home.t-online.de/home/meier-audio/index.htm

If they are 120 ohm resistors in parallel with 120 ohm loads, that would be a final 60 ohm load (R1*R2)/(R1+R2). But if they are 120 Ohm resistors in series that would present a 240 Ohm load to the amp. In this case the attenuation factor is 0.5

Hey, graghs don't lie, right?, but your graph sees to indicate that there is more bass and treble presence at stock impedances. hmmm. That can't be right.

So the Z you are reporting is for the amp output. In which case you are now driving the K501 through 120 Ohm resistors in series for a total of 240 Ohms.

The only thing you then have to worry about is damping factor - the higher the better. Otherwise the bass may start to sound muddy and slow and bloated.

With the greater bass and the greater treble and with the same level midrange levels you should perceive a more recessed midrange (overal tonal quality speaking, of course), at least relative to before. But since what you wanted was a greater sense of bass it should all even out.

Me, I've advocated about +1.5 to +2 dB at 50Hz using an equaliser.

-wal

 

[spike33]

The midrange is indeed slightly recessed. You can always take off the adapter when you want more prominent mids. It's like having two headphones in one!

With the adapter, these cans can rock!

major weakness of 501 = solved!

 

[JaZZ]

Quote:

Originally Posted by wallijonn Your 3.5 Ohm reference point says that you will have 3.5 ohm resistors in parallel to the 120 Ohm (MINIMUM at 20 Hz) headphones. In effect you have turned them from 120 Ohm headphones into 4 Ohm speakers. That can't be right. ... If they are 120 ohm resistors in parallel with 120 ohm loads, that would be a final 60 ohm load (R1*R2)/(R1+R2). But if they are 120 Ohm resistors in series that would present a 240 Ohm load to the amp. In this case the attenuation factor is 0.5 ...your graph sees to indicate that there is more bass and treble presence at stock impedances. hmmm. That can't be right.

Wallijonn, the graph refers to 1) 122.5 ohm output impedance and 2) 3.5 ohm output impedance, so serial resistance, not parallel resistance. The graph is o.k., since it shows the expected mid-bass and treble increase with the higher serial resistance (blue curve).

Thanks, Chris!

 

[Nak Man]

Quote:

Originally Posted by wallijonn Hey, graghs don't lie, right?, but your graph sees to indicate that there is more bass and treble presence at stock impedances. hmmm. That can't be right.

Now I'm confused. Green line is stock output vs blue line with 120 ohms adaptor, right ?

Chris, could you please clarify what resistor configuration and values you used to modify the output impedance ? Thanks much.

 

[Tim D]

Except for maybe the Ety's I don't like bumping up impedance and would rather run it through a high quality EQ if I had to. But even better/best are pad mods. I am guessing the brown pads provide more bass because the brown leather backing couples better and tighter than the other pads and thus transmits vibrations better. But who knows maybe they were designed to work with high impedance outputs, perhaps a question to ask the AKG engineers.

 

[WmAx]

Quote:

Originally Posted by wallijonn -Chris,

Jazz is correct, it's serial/series.

-Chris

 

[WmAx]

Quote:

Originally Posted by Nak Man Now I'm confused. Green line is stock output vs blue line with 120 ohms adaptor, right ? Chris, could you please clarify what resistor configuration and values you used to modify the output impedance ? Thanks much.

The Green line was the direct connection to a headphone amplifier. 3.5 Z ohms is the measured output impedance of that amp. I put 119 Ohms of measured resistance(resistor) between the headphone and amp(3.5 ohms), therfor equalling 122.5 Z Ohms; this is the blue line.

-Chris

 

[wallijonn]

Jazz, Chris -

That's what I said - that two 120 Ohm resistors were put in series, for a total of 240 Ohm loads.

On most headhones adding a resistor will darken it, changing the overall tonal balance towards the bass - it will seem darker, you can turn up the volume to bring back a brighter sound (since voltage is being dropped across the resistor it will sound quieter) which should sound as if there is more bass.

The above affect is what I have detected with my cable change on the K401 and the K501 - better bass, better treble, slight midrange recess relative to before.

You could get almost the same affect by changing to darker sources (if you presently have very bright sources). But I already had a dark source (I didn't like the Sony DVD players - they were too bright). If you have a bright source the resistors may be the only way to go, or equalisation.

 

[WmAx]

Quote:

Originally Posted by wallijonn That's what I said - that two 120 Ohm resistors were put in series, for a total of 240 Ohm loads.

Where do you get "two 120 Ohm resistors were put in series" from? Or is this just a miscommunication on your part, and you are referring to the approximate load that the amp sees?

Quote:

The above affect is what I have detected with my cable change on the K401 and the K501 - better bass, better treble, slight midrange recess relative to before.

I cerainly don't know what kind of cable you made -- but if it even begain to audibly cause the above measured differences I presented, then it has to have several tens of ohms of resistance considering the K501 impedance, only possible by inserting resistors in the cable, or a very very poor/faulty connection/joint.

-Chris