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help !!! some questions about adding 75 Ohm quality resistors to porta pro

post #1 of 22
Thread Starter 

1.hi, just as a new DIYer, I want  my new porta pro to be improved in sound quality by adding series of 75 Ohm high quality resistors but facing several questions :

 

_ how many resistors should i add in ( using ipod touch and ipod video to play ) ?

_ how should i solder those resistors to both drivers ?

_ what method used to stop leaking sound from headphone as i feel so uncomfortable when playing at maximum volume during travelling ? ( am i right that adding a pair of big pads, Ex: HD414 pads, would does so )

 

 

 

2.otherwise, i hav another set of porta pro but left driver is not working, cant be certain about fault cable either left driver itself....how do i check that the driver is still working ,by not having a try like soldering new cable and test ?

 

 

.

post #2 of 22

1)

1 resistor per channel

Inline with signal.

No idea, they're open headphones.

 

My recommendation - build or buy a little impedance adapter and don't mess with the headphones.

 

2)

Measure resistance across driver, if it's 60 ohms your driver is fine and cable is broken, next to 0, your wire is shorted, if it's infinite, your driver is fried.

post #3 of 22
Thread Starter 

thx bro....any further recommendation plz.....

post #4 of 22
Thread Starter 


 

Quote:
Originally Posted by FallenAngel View Post

1)

1 resistor per channel

Inline with signal.

No idea, they're open headphones.

 

My recommendation - build or buy a little impedance adapter and don't mess with the headphones.

 

2)

Measure resistance across driver, if it's 60 ohms your driver is fine and cable is broken, next to 0, your wire is shorted, if it's infinite, your driver is fried.


hi.... been searching but seen now repose of how to make a DIY piece of impedane adapter 100 Ohm....plz give me some instruction

post #5 of 22
Quote:
Originally Posted by khanhhoa1912 View Post


 

Quote:
Originally Posted by FallenAngel View Post

1)

1 resistor per channel

Inline with signal.

No idea, they're open headphones.

 

My recommendation - build or buy a little impedance adapter and don't mess with the headphones.

 

2)

Measure resistance across driver, if it's 60 ohms your driver is fine and cable is broken, next to 0, your wire is shorted, if it's infinite, your driver is fried.


hi.... been searching but seen now repose of how to make a DIY piece of impedane adapter 100 Ohm....plz give me some instruction


take a box.

cut 2 holes in the box

u should have bought the 2 jacks first do that while you are shopping for a box

put the 2 jacks in the holes you cut in step 3.

wire the grounds together.

put the resesters in the signel path

 

ur welcome.

 

I would normally recommend "whatever resistors you happen to have handy" but this usually comes with a reply of "what would be better"?

A 100 to 250 ohm dual linear pot would be better so you can tune the sound to your preferences, but since 75 is the number written in the bible by the lord 75 is what it is. Texas components bulk foil vishay resistors are well regarded.

post #6 of 22

you can buy the etymotic p to s adapter 

 

R0013514.jpg

post #7 of 22

This was done by head-fi user in the diy cable gallery

 

P040710_00460002[1].jpg

P040710_12180001[1].jpg

 

P040710_12190002[1].jpg

 

It's very simple to make and works like a charm, I can't find the members name if I do I'll post it

 

cheers

FRED

post #8 of 22

This is the definition of awesome.
 

Quote:
Originally Posted by Fred_fred2004 View Post

This was done by head-fi user in the diy cable gallery

 

P040710_00460002[1].jpg

P040710_12180001[1].jpg

 

P040710_12190002[1].jpg

 

It's very simple to make and works like a charm, I can't find the members name if I do I'll post it

 

cheers

FRED

post #9 of 22
Thread Starter 


 

Quote:
Originally Posted by FallenAngel View Post

1)

1 resistor per channel

Inline with signal.

No idea, they're open headphones.

 

My recommendation - build or buy a little impedance adapter and don't mess with the headphones.

 

2)

Measure resistance across driver, if it's 60 ohms your driver is fine and cable is broken, next to 0, your wire is shorted, if it's infinite, your driver is fried.


hi bro......the value of left driver was shown at 32 ohms, same as right driver value of 32 ohms..... can I conclude that the left driver does not have any problem ???

post #10 of 22

Are you sure you measured correctly? Both sides should be 60-ohm.

post #11 of 22
Thread Starter 
Quote:
Originally Posted by Lil' Knight View Post

Are you sure you measured correctly? Both sides should be 60-ohm.



yes i did bro, using FLUKE 117 to measure numbers............both sides are 32 ohms so what does it say ???

post #12 of 22
Thread Starter 

yea...the result now is 60 ohms.....haha..my drivers have not gone wrong yet........................

post #13 of 22

Could someone explain the point to me? I understand high vs low impedance voice coils, but does adding resistance inline really have the same effect as the voice coil itself having a higher impedance? I don't see how it would. If anything I'd think you'd just get more resistor noise in the signal path. Am I missing something?

post #14 of 22

The inline resistors change the frequency response of the headphones in response to the variations of impedance VS frequency of the driver.

 

What effect does having a high impedance driver have? The fact that the amp cant drive 32ohms nicely dosnt mean anything about the headphone, just the amp. Beyer's apparent inability to make a 32 ohm headphone that sounds like their 250ohm driver in the same shell does not extend to other MFR's who pride themselves on their low impedance drivers.

post #15 of 22

Not disagreeing, just discussing. If this is the case, why is it that people with an amp that is say... awesome for 300ohm cans.. will  go buy a second amp to drive their Grado's also? Why not just add resistance to all lower-ohm cans they own?

 

I'm curious because I will soon have a Crack amp which is intended for high impedance cans. I'll use it with HD600/650, Sextett, and soon something closed. Can't decide between a high-ohm DT770 or a D2000 - been leaning away from the D2000 due to its low impedance. You are saying if I just throw some resistance inline then there's no big difference vs an already high-impedance can?

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