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General Question about Impedace

momo7G

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I have read about matching the impedance for speakers / headphone at about 1/8 or 1/10 of the amp output.

Which it works for a better damping factor the transducer to provide better base performance.

I am wondering, what would happen if I plug a low impedance, say 16 ohm, headphone into a amp with output impedance of 51 ohm.
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Will I hear sound that greatly distorted? If that's the case, how will it sound in real life? Will it like muffled or echoing base or something really funny?
 

amirm

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I have read about matching the impedance for speakers / headphone at about 1/8 or 1/10 of the amp output.
No, no, no. :) In audio you never want to match impedances.

What you want is the output impedance to be a fraction of the input impedance of the next device connecting to it. The rule of 10:1 comes from that.

If you violate this as in the case of the amp you posted, it will change the frequency response of the speaker/headphone you are connecting to it. This may be a positive thing (e.g. increasing bass response) or bad thing (e.g. increasing highs).

In general, it is best to avoid any high output impedance amplifiers and certainly one in this range.
 

amirm

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Oh wait. The 51 ohm above is the line output. That is fine because typical line input is 1000 to 10,000 ohm. So no problem there. We only get concerned when the load is a speaker or headphone that has much lower impedance.
 

dc655321

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The effects of this sort of impedance "issue" depends on the what the impedance curve of the headphones looks like, and what the relative difference is between amp and 'phones. For example, planars are virtually constant impedance (purely resistive over the audio range), so the only effect is constant attenuation. Something like the HD-6xx has a large impedance peak in the bass, so its impedance is far from constant. Most headphones are that way...
 

Tene

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The effects of this sort of impedance "issue" depends on the what the impedance curve of the headphones looks like, and what the relative difference is between amp and 'phones. For example, planars are virtually constant impedance (purely resistive over the audio range), so the only effect is constant attenuation. Something like the HD-6xx has a large impedance peak in the bass, so its impedance is far from constant. Most headphones are that way...

Yeah I remember my HD598 having a huge impedance peak going up to 300Ω which is kind of concerning for a 50Ω model. Made them sound bloated in the mid-bass with the 10Ω output impedance of my STX. Overdamping isn't much of an issue as long as the impedance curve behaves itself as you said, though sometimes it's hard to find measurements for uncommon headphones.
 
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