# Headphones and vaping: why do ohms behave the opposite?

Discussion in 'Sound Science' started by CoryGillmore, Dec 1, 2018.
1. Alright guys so I've been into head-fi since around 2009. Been into vaping since 2014. Something I've noticed in regards to ohms and how they matter to each, is that they seem to behave in the opposite way. Example: in vaping the lower the ohm reading on your coil is, the more power it will take to power your coil. In headphones, the lower the ohm reading, the easier it is to power. I guess in headphones, ohms actually behave the way they should behave. As with headphones, less resistance requires less power.

So I guess the better question is: how come in vaping, wire with less resistance takes more power to use? Shouldn't it be the exact opposite? I realize this question would be better suited to a vaping forum..but what kind of douche visits a vaping forum? So yeah..head-fi it is...

2. Contributor
with headphones the total power you'll need will be decided by loudness, as that's really the only thing we care about when we turn the volume knob. so the sensitivity of the driver is at least as important as the impedance.
in P=V²/R the sensitivity of the headphone will determine the voltage you need to get the volume level you like. and as a squared variable, voltage can easily dominate over impedance when looking at the resulting power. so the general rule of thumb between headphone's impedance and power is often false.

with vaping, I'm going to assume that the voltage is determined by the battery, so that will be considered sort of a fixed value for further estimations. leaving the impedance of the coil free reign to determine the amount of current that will flow through it.
or using the same P=V²/R, assume V is a constant and you have your answer.

CoryGillmore likes this.
3. If headphone amps didn't have volume controls, then (all else being equal) lower impedance headphones would draw more power and be louder than higher impedance headphones. I don't know anything about vaping specifically, but I expect that is how it works there too. Using a lower impedance coil produces more vapor because the coil is drawing more power.

Headphone amps do have volume controls, and people set the volume to wherever they want to listen. Since lower impedance headphones naturally draw more power, you have to lower the volume further than you would for higher impedance headphones in order for them to draw the same power and be the same loudness. If vaping devices had level controls it would work the same. If you had two identical devices except for the impedance of the coil, then to get the same amount of vapor from each you would have to set the lower impedance to a lower setting and the higher impedance to a higher setting.

CoryGillmore likes this.
4. This makes a ton of sense and reminds me of something in vaping I had nearly forgot about which illustrates your point perfectly: mechanical mods. These are vaping devices that contain no electronic chips and are usually just a metal tube with an 18650 battery inside of it. The vapor production on such a device is determined by the impedance of the coil sitting on top of it. And lower impedance coils draw much more power from the battery which result in more vapor production.

Thanks to both of you!