impact of 1/8th impedance rule on sound
Sep 30, 2012 at 12:34 AM Thread Starter Post #1 of 17
domes

domes

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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? 
 
Sep 30, 2012 at 11:31 AM Post #3 of 17
Quote:
domes said:
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? 
Click to expand...

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.
 
Sep 30, 2012 at 12:31 PM Post #4 of 17
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.
 
Sep 30, 2012 at 1:04 PM Post #5 of 17
Quote:
domes said:
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.
Click to expand...

What source(s) do you plug the AudioEngine D1 into?
 
Sep 30, 2012 at 8:29 PM Post #6 of 17
Quote:
domes said:
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.
Click to expand...

 
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).
 
Sep 30, 2012 at 8:52 PM Post #7 of 17
domes said:
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? 
Click to expand...


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.
 
Sep 30, 2012 at 9:03 PM Post #8 of 17
Quote:
domes said:
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? 
Click to expand...

 
There's a link at the bottom of the post in my sig.
Primarily there's a difference in frequency response.
 
Oct 2, 2012 at 2:22 PM 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...
 
Oct 2, 2012 at 2:47 PM Post #10 of 17
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. :)
 
Oct 2, 2012 at 3:25 PM Post #12 of 17
Quote:
slickman said:
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? 
Click to expand...

 
1 Ω, if you mean connecting a 10 Ω source (DAC) to a 1 Ω amplifier.
 
Oct 2, 2012 at 4:33 PM Post #14 of 17
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.
 
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