[SethGG]

Hi peoplez of head-fi
 
I'm thinking about getting a Meridian Explorer for my AD900X cans because I can get one for really cheap and it has some amazingly positive reviews. The only potential problem I have encountered is that the Explorer has an output impedance of 5 ohm and that may be a tad high for my 38 ohm headphones (according to the 1/8 rule an impedance of 38/8=4,75 or lower is recommended). The Explorer2 on the other hand has an output impedance of only 0,47 ohm but it's also double the price.
 
So I would like to know if the output impedance is going to be a problem for me. Also why is so important to have a low output impedance with easy to drive headphones?

 

[billybob_jcv]

There is a long, complicated answer to why that rule exists, but it involves math and I'll just screw it up if I try to explain it...

The short answer is a concept called damping factor. You want impulse signals sent from the amp to the headphone to rise sharply and not to oscillate. A higher ratio between the headphone and the amp impedance provides a higher damping factor.

 

[SethGG]

There is a long, complicated answer to why that rule exists, but it involves math and I'll just screw it up if I try to explain it...

The short answer is a concept called damping factor. You want impulse signals sent from the amp to the headphone to rise sharply and not to oscillate. A higher ratio between the headphone and the amp impedance provides a higher damping factor.

I see, but does that mean that the Explorer is not going to work for me?

 

[billybob_jcv]

It's a guideline, not a hard absolute. I don't know for sure, but I think you should be OK.

 

[onebigunion]

I think you'll have no problem.  The impedance of the 900x is relatively flat, so you won't have any significant frequency response fluctuations.  You're at a damping factor of about 6.5, acceptable in my opinion.  Especially since the 900x is pretty well-damped already.  I say go for it.

 

[PurpleAngel]

  Hi peoplez of head-fi
 
I'm thinking about getting a Meridian Explorer for my AD900X cans because I can get one for really cheap and it has some amazingly positive reviews. The only potential problem I have encountered is that the Explorer has an output impedance of 5 ohm and that may be a tad high for my 38 ohm headphones (according to the 1/8 rule an impedance of 38/8=4,75 or lower is recommended). The Explorer2 on the other hand has an output impedance of only 0,47 ohm but it's also double the price.
 
So I would like to know if the output impedance is going to be a problem for me. Also why is so important to have a low output impedance with easy to drive headphones?

 
I used my 40-Ohm ATH-A900X headphones with a Essence STX, which has a 10-Ohm output impedance and the A900X's sounded fine.
So the Meridian Explorer's 5.25-Ohm output impedance should be ok.