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impact of 1/8th impedance rule on sound

post #1 of 17
Thread Starter 

What is the sonic impact of violating the 1/8th rule with matching headphone impedance to amplfier output impedance?  Does the bass get mushy?  Distortion?  Is it linear where the worse the ratio is the worse the sound?  I have an amp that has an output impedance of 10 ohms and headphones that are 50 ohms.  I am wondering if it is worth switching to an amp with an output of 5 or lower.  Is that a big enough mismatch to consider changing amps or am I being concerned over nothing? 


Edited by domes - 9/29/12 at 9:36pm
post #2 of 17

It depends on exactly what 50 Ω headphones you have. However, while the difference might be audible, it is usually not a major one.

post #3 of 17
Quote:
Originally Posted by domes View Post

What is the sonic impact of violating the 1/8th rule with matching headphone impedance to amplifier output impedance?  Does the bass get mushy?  Distortion?  Is it linear where the worse the ratio is the worse the sound?  I have an amp that has an output impedance of 10 ohms and headphones that are 50 ohms.  I am wondering if it is worth switching to an amp with an output of 5 or lower.  Is that a big enough mismatch to consider changing amps or am I being concerned over nothing? 

I run 40-Ohm, 50-Ohm and 60-Ohm headphone with my Essence STX (10-Ohm) and I feel no reason for changing to a different amplifier.

post #4 of 17
Thread Starter 

I have Sennheiser HD598 and the Audioengine D1.  Sounds like it is not enough of a difference to consider changing at least for that reason.  Been thinking of changing to the Aundinst HUD-MX1 or the HRT Musicstreamer II and with maybe the Maxtrix M Stage.  Was hoping to improve the bass performance a bit and the soundstage.  I thought the HD598 was supposed to have a great soundstage and I'd say it is just ok with the D1.  Thought maybe the 10/50 ohm mismatch might be contributing to that.

post #5 of 17
Quote:
Originally Posted by domes View Post

I have Sennheiser HD598 and the Audioengine D1.  Sounds like it is not enough of a difference to consider changing at least for that reason.  Been thinking of changing to the Aundinst HUD-MX1 or the HRT Musicstreamer II and with maybe the Maxtrix M Stage.  Was hoping to improve the bass performance a bit and the soundstage.  I thought the HD598 was supposed to have a great sound stage and I'd say it is just ok with the D1.  Thought maybe the 10/50 ohm mismatch might be contributing to that.

What source(s) do you plug the AudioEngine D1 into?

post #6 of 17
Quote:
Originally Posted by domes View Post

I have Sennheiser HD598 and the Audioengine D1.  Sounds like it is not enough of a difference to consider changing at least for that reason.  Been thinking of changing to the Aundinst HUD-MX1 or the HRT Musicstreamer II and with maybe the Maxtrix M Stage.  Was hoping to improve the bass performance a bit and the soundstage.  I thought the HD598 was supposed to have a great soundstage and I'd say it is just ok with the D1.  Thought maybe the 10/50 ohm mismatch might be contributing to that.

 

Bass performance may be affected by impedance mismatch, but I doubt that you would notice any improvement in the soundstage with a lower impedance amp. If anything, I'd rather expect it to get worse - that's what happens when the tonal balance shifts towards low frequencies (unless there's also some phase shifting going on that affects the soundstage - but that's very difficult to figure out).

post #7 of 17
Quote:
Originally Posted by domes View Post

What is the sonic impact of violating the 1/8th rule with matching headphone impedance to amplfier output impedance?  Does the bass get mushy?  Distortion?  Is it linear where the worse the ratio is the worse the sound?  I have an amp that has an output impedance of 10 ohms and headphones that are 50 ohms.  I am wondering if it is worth switching to an amp with an output of 5 or lower.  Is that a big enough mismatch to consider changing amps or am I being concerned over nothing? 

If you have, for example, 50 Ohm 'phones and an amp with a 50 Ohm output impedance, then you would get very power power transfer from the amp to the 'phones.
But if you are 50 to 10 Ohms: 'phones to amp, then power transfer will be fine.
post #8 of 17
Quote:
Originally Posted by domes View Post

What is the sonic impact of violating the 1/8th rule with matching headphone impedance to amplfier output impedance?  Does the bass get mushy?  Distortion?  Is it linear where the worse the ratio is the worse the sound?  I have an amp that has an output impedance of 10 ohms and headphones that are 50 ohms.  I am wondering if it is worth switching to an amp with an output of 5 or lower.  Is that a big enough mismatch to consider changing amps or am I being concerned over nothing? 

 

There's a link at the bottom of the post in my sig.

Primarily there's a difference in frequency response.

post #9 of 17

I'm using my 21ohms UE IERM with the 5ohms output impedance Matrix m-Stage. I've been wanting to change amps for a long time, but they do sound quite good though...

post #10 of 17
Thread Starter 

My source is a mac mini via USB.  I suppose I could try the optical via the headphone out on the mini if I got an adapter and ran it to the D1 optical input.  Xymordos - if you decide to sell the matrix, let me know. :)

post #11 of 17

So if the output impedance of my source is 10 ohms and the output impedance of my amp is 1 ohm, then what is my actual output impedance? 10 ohms? 

post #12 of 17
Quote:
Originally Posted by Slickman View Post

So if the output impedance of my source is 10 ohms and the output impedance of my amp is 1 ohm, then what is my actual output impedance? 10 ohms? 

 

1 Ω, if you mean connecting a 10 Ω source (DAC) to a 1 Ω amplifier.

post #13 of 17
Quote:
Originally Posted by stv014 View Post

 

1 Ω, if you mean connecting a 10 Ω source (DAC) to a 1 Ω amplifier.

 

 Yes, that is what I'm talking about. I have the Dacport LX and Burson Soloist. The Dacport LX has 10 ohm output impedance and the Soloist supposedly has less than 1. 

post #14 of 17
Thread Starter 

I forgot I had a optical cable downstairs hooked up to my airport express.  I hooked it up to the headphone out on the mac mini and into the optical input on the D1.  Wow!  What an improvement!! Via the usb connection the sound was smooth with deeper bass but it sounded more congested or slightly restricted.  Via the optical, way more open sounding, natural and much better soundstaging.  My headphones sound like a new phones!  I am literally floored.  So this is what a decent DAC is supposed to sound like.  I can actually hear depth and placement.

 

I had already purchased a used HRT music streamer that I am waiting to get delivered so this comparison should be interesting except I won't be able to compare via my headphones, only speakers as I don't have a separate headphone amp yet.  I might not be getting one either.  Does optical usually sound better than usb?  Really curious now if the optical on the D1 will smoke the HRT via usb.  I am at least convinced that the best way to use the D1 is with the optical connection.

post #15 of 17
Quote:
Originally Posted by Slickman View Post

So if the output impedance of my source is 10 ohms and the output impedance of my amp is 1 ohm, then what is my actual output impedance? 10 ohms? 

 

The place where you plug your headphones is the place where this impedance is measured.

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