OHMs? Impedance? please help explain...

[belltollsforthee]

i am having some trouble understanding what soundcards will work with my headphones. My headphones are rated at maximum input power 500mW and 64 ohms impedance. Do i need a headphone amp? Would it be beneficial to get Xonar Essence STX?

Xonar Essence STX says
Output/Input Full-Scale Voltage 2 Vrms (5.65 Vp-p)
Headphone Impedance Optimized for 32~600Ω

Thanks for the help

 

[house70]

I don't think you need the amp, the impedance of that prospective card is within limits.
External speakers have lower impedance than headphones, the bigger the speaker, the lower the impedance. That helps with low-frequency sound (bass). headphones are limited by design.
I don't use add-on sound cards, I sometimes find the drivers to be too taxing on the system, and any additional expansion means increased chances for resource conflicts.
Do your headphones work with the onboard sound? If they do, they will also work with the add-on card.

 

[hunter315]

The impedance is part of the design of the drivers in the speakers, your average desktop or home audio speaker is usually about 2-8 ohms, headphones are much higher impedance, this reduces the input current of them reducing their power draw on stuff like ipods.


If you try to use them on a system expecting 8 ohm speakers, you wont get nearly enough power out of them and your sound will be weaker, i would first check using your onboard to see if it doesnt already have enough power for them, if it doesnt i would get the card, since they are within the impedance range of that card you wont have an issue, it will sense it and compensate.


@house70, impedance is more a feature of the driver than a function of the size, i can find you a 2 ohm tweeter and a 8 ohm woofer or vice versa.

 

[Ranger67]

ohms is a measure of resistance. The low the ohms or resistance the less power required to drive the speaker but typically the greater the distortion. Manufactures in crease the ohms to mask the distortion that is produced from the field generated by the signal. The conception that more ohms is better could not be farther from the truth. Imagine a boat on the ocean, is it easer to sail through 8 foot waves or 16-32 foot waves. It is math and physics and any one arguing it is simply wrong and needs to educate themselves of the physics of it. Humans hear in 8 ohms also. Watts drive the speaker not ohms and the ohms is the resistance of the voice coil or crossover.

There is a brand of earbuds being launched by ClarityOne that claims a patented technology and is 8 ohms. www.clarityoneaudio.com. If they have accomplished what is being claimed, it will be a revolutionary change in sound. I saw an interview from CES and have reviewed their site. It looks like they are for real.

 

[RetiredChief]

ohms is (as stated above) a measure of resistance (R) and can be two flavors - Pure Resistance and or Impeadance. Impeadance includes the reactive components (RLC) such as capacitance and Inductive and is only valided at a given frequency For audio about 10KHz (center freq of 20 -> 20 KHz).

For Speakers you need to match the Output Impeadance (source) with the Device Impeadance (speakers). Max power transfer is when Zout=Zin. In the case of a Amp with a output Z of 8 ohms, If the speakes have 4 ohms, or 16 ohms then the power to the speakers is reduced. Also effect freq response. Note Speakers are generally a high wattage rating when compared to headphones.

Headphones - Above still applies: However, The output Z for the driver is normally high as current requirements are much lower (Power = Current squared x Ohms), and IS normally NOT specified by manuf. - Makes it diff to match Zs. I find that the 16/32 ohm Headphones provide the best match - Need to also pay attention to the Type of device used to reproduce the sound.