A couple questions

The DT990-32 should be easier to drive.

Afaik, terms like "well-driven", "underpowered", or funny creations like "unamped" are not even defined in a non-scientific way.

Have you seen the "describing sound: a glossary" thread? Vague, partly nondescript explanations imo. Helpful in a way, but stil...

About your 250/32 ohm question:

Sensitivity usually (but not always) is specified in db SPL at 1 mW and the beyer models all seem to have the same sensitivity regardless of impedance.

1mW is 1mW is 1mW.

With the higher impedance model you need a bit higher voltages, but less current and vice versa with the lower impedance model. A well designed amp shouldn't and doesn't have problems powering either load.

I will add that in the dynamic headphone world because of the wide varying range of impedances between 16 to 600Ohms, it is *easier* for an amp (built-in to a DAP or as a stand-alone device) to provide enough current rather than enough voltage. This is why there's the impression that lower impedance headphones are "easier to drive". 

Sensitivity relates to the efficiency with which the headphone is able to convert a unit of power input into sound energy. More efficient headphones require less power to generate a specific loudness. Higher efficiency headphones therefore have the reputation of being "easier to drive".

Jack

You can use the numbers to calculate how loud an amp could drive your headphones, but to see how well it performs you have to do measurements (e.g. with http://audio.rightmark.org/)*, or try to compare the devices by ear. :s

*) maybe someone already did that with your mp3 player and a dummy load, try to google for "<your player> RMAA"

The link you posted is a simple loopback test (line-out to line-in) without a (dummy) load.

Here's one with a 32 ohm load: http://rmaa.elektrokrishna.com/Comparisons/Cowon... 

These measurements don't show you the output power, to put it simple they show you how much the player degrades the signal.

Ideally, the frequency response would be flat and noise, distortion and crosstalk very low.

For output power look at the specs on the Cowon website. It says 29 mW into 16 ohms. 

You can power pretty any much any headphone with it, the question is how loud.

Most in-ears have low impedance and very high sensitivity, no problem with volume there.

However, with high-end (full size) headphones you'll probably be limited to below 100 dB peak.

The thing is that there are more variables involved besides sensitivity. What headphones are you looking at specifically?

I have headphones ranging from 5 ohms to 10,000 ohms and SPL from 90 to 125. The difference between them all is minimal, but on my relatively powerful MF X-CANV8P the volume control varies from 7 to 1 o'clock to get a decent volume out of them all. Only the Sony DR4C at 10,000 ohms will not work out of an ipod. The bulk work fine at maximum volume on the ipod and with only the most sensitive earbuds (SPL 124 and ohms 32) do I need to reduce the ipod's volume. Adding a FiiO amp to the ipod makes all bar the DR4Cs work fine,

That will hopefully give you a 'real world' explanation of how this works.

Quote:

Originally Posted by budgetboy 

Well maybe I'm confused. Like say I want to get the Beyerdynamic DT990/32 to use with my Cowon S9. Sensitivity=96db/Impedance=32ohms

I assume that they will get loud enough with my S9, but when I proposed this setup in threads on head-fi, people have stated that without an amp, the headphones will lose dynamic range, a full frequency response, and generally sound "less alive". So I'm guessing that this is caused by a lack of current (i assume this is constant from a portable source) not by a lack of gain (changes when you change the volume). I don't really get how this works, but what I'm asking is whether an S9 has enough current to get the most out of the DT 990/32, given their sensitivity. I believe that voltage and impedance are pairs as are current and sensitivity.

 

Am I on the right track here?

Look at the rmaa test I linked. Without load (like in this setup: cowon s9 - amp - headphones) dynamic range is 90.7 dB, with 32 ohm load it still is 90.4 dB. A difference that small is negligible.

So there is no real loss of dynamic range.

Frequency response will only be slightly rolled-off at the lower end, dunno if you will even notice this.

The only thing that really suffers is stereo crosstalk. If you need/want the left/right channel to be as much separated from each other as possible then adding an amp makes sense.

This kind of confusion is caused by people who make exaggerated claims, amp A is superb and significantly better than amp B. These headphones need to be amped or else you can clearly hear they are not performing at their best. In reality the differences are tiny.