Impedance in headphones and speakers

[Jimbo Mahoney]

OK, I think I understand impedance in speakers, but I'm confused because it seems the situation in headphones and speakers is different. I'm probably just looking at things a bit backward though....

In headphones, a lower impedance requires less power to drive them, so low impedance phones are normally used with portable audio to maximise battery life, right?

In speakers, a lower impedance requires MORE power to drive them.

 

[Jimbo Mahoney]

I'm still confused.

When I plug my 85 ohm headphones into my MP3 player, I need to turn the volume up higher to achieve the same loudness as I do with my 24 ohm headphones. Thus, my 24 ohm headphones are easier to drive, right?

When I plugged my hifi amp into a set of 4 ohm speakers, I needed to turn the volume up more to achieve the same loudness as I did with my 8 ohm speakers.

So, with headphones, I get louder music with a lower impedance, but the reverse seems true with speakers an an amp.



EDIT - Ah, unless my confusion lies with the fact my amp (a NAD C320) has impedance detection of some sort...

So lower impedance = easier to drive and louder, right?

 

[Jimbo Mahoney]

OK, I guess I'm just confused because I need to turn the volume knob on the NAD higher when it's connected to 4 ohm speakers, which I guess makes sense if it needs to supply more current.

Just confused me how my mp3 player needs to be on, say 20 (out of 25) to drive my 85 ohm Sennheisers vs. 16 to drive my 24 ohm Sonys.

 

[Jimbo Mahoney]

What ohmage is your amp.

It says

• 2 x 40 Watts continuous into 8ohms
• 90 Watts dynamic power into 8ohms
• 125 Watts dynamic power into 4 ohms
• 160 Watts dynamic power into 2ohms
• Impedance Sensing Circuitry (ISC)

I've used it to drive 4 ohm speakers, which I assume is OK, especially if I don't play my music very loudly.

 

[Jimbo Mahoney]

Mine are Celestion F20's - 89 dB, 8 ohms

The pair I tried (lucky bugger who owns them!) were Dynaudio Audience 62's - 86 dB, 4 ohms