quote:

Originally posted by dukes ok for headphones what are ideal conditions for your impedance values? i know that the headphones should be as close to the same value as you mixer output but is it better to have high impedances or low?

Matching impedence is meaningless. Generally, higher impedance headphones are harder to drive than lower ones... for example, you would probably want a headphone amp to drive a Beyerdynamic DT770 Pro (250 ohms impedance) and you wouldn't need one to drive, say, the Sennheiser HD25 (70 ohms impedance). Of course, impedance isn't the ONLY thing that influences how loud a headphone gets or how well a headphone is driven from any given source (note those are *two seperate concepts*), things like efficiancy and maximum spl also matter...

quote:

Originally posted by Gluegun Matching impedence is meaningless.

Every place I've looked said to match impendence I thought...

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perhaps i phrased this slightly wrong....
i know that matching is important because the headphones act in the same way as mesurement devices in electronics.

but im wondering the effects on sound quality that high and low impeadance values have?

*tries to remember electronic engineering class* (might not be accurate)

I think you have to match the impedances so that maximum power transfer can occur. This means that the speakers and headphones will operate at maximum efficiency and sound will be at max volume with minimum distortion.

I dont think it matters if the impedance is higher or lower, i think its the size of the difference that matters. The bigger the difference, then the bigger the sound distortion and the lower the effiecency.

i just found out the matching is very important and you need higher impedance values between 50-70 are the best. its something to do with the best output with minimum interfeancy and power consumption.

I posted a number of comments on impedance matching in another thread that are relevant here:

quote:

When it comes to time-varying signals (like audio), you have to match the impedances (ohms) between your components. It's not really an issue of whether or not your headphones or speakers are easier or harder to drive--if the impedances are mismatched, the signal from your amplifier will not drive your headphones (or speakers) efficiently. This means that pairing low-impedance headphones with a high-impedance amplifier will result in a lower sound pressure level than if you matched the impedances of your headphones to your amplifier. If you can't match the impedances exactly, getting them closer still improves the efficiency. The correct rule to remember is that matched impedances are easier to drive than mismatched impedances.

Afterwards, I worked out that power transfer falls off more rapidly if the load impedance is too low than if it's too high. (I graphed power transfer vs. inpedance on the computer--I'm such a big dork ) Thus if you can't match the impedances exactly, it's better to be too high than too low, as far as efficiency is concerned.

One other effect that you have to be aware of is that impedance mismatches cause signal reflections--that's why you lose power transfer, even when connecting an "easier-to-drive" headphone to a high-impedance amplifier. Worse, impedance varies with frequency, so mismatching the nominal impedances of your components will almost certainly result in distortion. I'm not sure exactly how this changes if the headphone impedance is too low vs too high, but my thinking is that it's still probably better to go a little too high than a little too low.

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The impedeance matching does (kinda) affect the sound generated my your headphones. If headphone impedence is too high then genrally it's a bit tinny, too low and it's a bit muddy. The bigger the mis-match the bigger the effect. Tho it's not always that noticeable. Plus in genral it's better to get a higher impedance mixer output than a lower beacause it's normally able to deliver more power like duke says 50-80ish is about as high as you want to go really for driving normal DJ headphones cos thats roughly the impedance of them. As another person said the closer the impedences the more efficent and the more power can be driven into a given set of phones by a given mixer. So to say that the impedence is meaningless I think is kinda wrong. Tho your right that in the big scheme of things SPL and overall frequency characteristic is more important as is the efficency i.e. how much power the headphones will effecently use of which they draw(also changes with impedance) from your mixer. Also in my humble opinion how sturdy the things are, so long as they are useable(i.e. ok soundwise), isolate enough and are easy to monitor with, is the most important thing. It doesn't matter how good they are if they break within a few months, whats the point **chough SONYS chough**. Remeber these are for constant pulling off and on not placing delicatly on and absorbing yourself in the bright freqency responce hehehe

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