First of all I would like to say thank you proton007 for taking your time and effort to get all this information together, especially "Hydraulic Analogy" is great, there are some minor things that gets me little confused, but otherwise I think I get the point perfectly.

Second thing is that when it comes to formulas I get little lost.

**Mainly here :**

Use this formula to calculate the power needed:

```
Power = Antilog ( (Desired SPL - SPL per mW)/ 10).
Note that a 3dB increase in SPL will cause a 2x increase in Power.
For reference, 85 dB is considered to be the limit where long term exposure can cause hearing
damage.
Use 85dB to calculate the average power needed.
```

Deduced that SPL is sensitivity, 85 dB is "ideal volume" but thats where it ends for me

I don't want to waste your time, but if you get some to spare, could you please show me and maybe other electrical newbies example of explained calculation ?

Got data here :

**Sennheiser HD700**

- Nominal Impedance : *150Ω*

- Max Impedance : *370Ω @ +-120hz*

- Sensitivity : *105dB (Characteristic sound pressure level (at 1 KHz) - 105 dB SPL (1 kHz, 1 Vrms))*

- THD : *0.03% (1 kHz, 1 Vrms)*

**FiiO E12**

- Drive ability : *16~300Ω (recommend)*

- Output Power : *>880mW@32Ω*

- THD : *<0.005%*

- Output Impedance :* <0.5Ω*

- Input Sensitivity :* <710 mV(Gain:high)*

- Signal to Noise Ratio : *>110dB*

- MAX input Level : *>8 Vrms*

- MAX output voltage : *15.5 Vp-p*

- MAX output current : *170 mA*

- Channel imbalance : *<0.5dB*

Your opinion on these two would mean a lot to me. Thanks in advance.

Sources :

http://en-us.sennheiser.com/downloads/download/file/3329/HD_700_GB_542592_low.pdf

http://graphs.headphone.com/graphCompare.php?graphType=0&graphID[]=3808&scale=30

http://fiio.com.cn/products/index.aspx?ID=100000038732625&MenuID=105026001

ps : Liked the avatar-bold text matched color

Edited by Flisker - 11/14/13 at 10:09am