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Technical Inquiry: IEM, Changes in Impedance and Sensitivity

post #1 of 13
Thread Starter 
I've been searching the forums, but still can not grasp the connection between impedance/sensitivity and their relation to the performance of an IEM.

I have requested the services of a company to modify the driver layout of several of my IEMs. Put aside the possible changes in sound signature, what should I expect in terms of performance (I.e. with the same volume setting before/after, possible difference in audible perception? possible difference in DAP battery life? etc.) should the following factors change?

Sensitivity 119 -> 110
Impedance 36 -> 16

Your valued feedback would be most appreciated.
post #2 of 13
Quote:
Originally Posted by JiPod View Post
I've been searching the forums, but still can not grasp the connection between impedance/sensitivity and their relation to the performance of an IEM.
Because in most of the time, there is very little, if any connection at all, between impedance/sensitivity and their relation to the performance of an IEM.
post #3 of 13
Thread Starter 
Quote:
Originally Posted by ClieOS View Post
Because in most of the time, there is very little, if any connection at all, between impedance/sensitivity and their relation to the performance of an IEM.
Allow me to rephrase my inquiry.

If the IEM's impedance changes from 32 ohms to 16 ohms, all other variables unchanged, how does this affect the DAP's battery life? I am assuming that the battery life is reduced as more current will be utilized.

Further, if the IEM's sensitivity changes from 119 dB SPL/mW to 110 dB SPL/mW, all other variables unchanged, how does this effect the listener's perception of the set volume? I am assuming that the IEM should sound not as loud.
post #4 of 13
it should require 4 times the voltage to get equivilant volume, at least if those numbers are correct, and i think twice as much current. but dont quote me on that lol im at work
post #5 of 13
Quote:
Originally Posted by JiPod View Post
If the IEM's impedance changes from 32 ohms to 16 ohms, all other variables unchanged, how does this affect the DAP's battery life? I am assuming that the battery life is reduced as more current will be utilized.
Well, if impedance is lower then obviously you will need less power to get the same volume which in term will save you more battery. Just show you how much a noob I am still . However, given that the most power consuming part on most DAP is not on the amp section (usually it is on the CPU/decoder), the battery save will not be very significant.


Quote:
Originally Posted by JiPod View Post
Further, if the IEM's sensitivity changes from 119 dB SPL/mW to 110 dB SPL/mW, all other variables unchanged, how does this effect the listener's perception of the set volume? I am assuming that the IEM should sound not as loud.
You will never get to the point of 110dB, left alone 119dB. The number only tell you how loud the headphone can theoretically be per 1mW of power. If you do listen at that kind of volume, you will be deaf very soon. You have a normal listening volume, which probably near / around 80dB and won't change depends on how easy/sensitive the IEM can be driven, right?
post #6 of 13
Thread Starter 
Ok ok ok. Now I'm even more confused.

Quote:
Originally Posted by ClieOS View Post
Well, if impedance is lower then obviously you will need less power to get the same volume which in term will save you more battery. However, given that the most power consuming part on most DAP is not on the amp section (usually it is on the CPU/decoder), the battery save will not be very significant.
Was I wrong to assume that the lower impedance, all other variables unchanged (volume setting included), would draw more current from the source, thus shortening battery life?

Quote:
Originally Posted by ClieOS View Post
You will never get to the point of 110dB, left alone 119dB. The number only tell you how loud the headphone can theoretically be per 1mW of power. If you do listen at that kind of volume, you will be deaf very soon. You have a normal listening volume, which probably near / around 80dB and won't change depends on how easy/sensitive the IEM can be driven, right?
Am I wrong in assuming that the lower sensitivity, all other variables unchanged (volume setting included), yields a "less louder experience"?
post #7 of 13
that first quote you made of ClieOS, while technically incorrect, what he meant was correct, the power will be the same, the thing that will be lower for the same volume will be the voltage, but the current will be higher. power is current times voltage, so if your voltage dropped by half, your current draw would double, if you wanted equal power, to get equal SPL's. Also, i think batteries life is based on the amount of current being drawn, not the voltage that is needed. So the battery would drop off faster. I dont know this from fact, mearly because battery capacity is quoted in mAh, not mVh.

does that clear it up?
post #8 of 13
Thread Starter 
Quote:
Originally Posted by SoupRKnowva View Post
that first quote you made of ClieOS, while technically incorrect, what he meant was correct, the power will be the same, the thing that will be lower for the same volume will be the voltage, but the current will be higher. power is current times voltage, so if your voltage dropped by half, your current draw would double, if you wanted equal power, to get equal SPL's. Also, i think batteries life is based on the amount of current being drawn, not the voltage that is needed. So the battery would drop off faster. I dont know this from fact, mearly because battery capacity is quoted in mAh, not mVh.

does that clear it up?
So I plug my modified IEM into my iPod. I do not fiddle with any settings. With the impedance dropping from 36 to 16, my battery life is shortened. Further, with sensitivity dropping from 119 to 110, the sound would be less "loud" in comparison.
post #9 of 13
Yes.
post #10 of 13
yes, it would be less loud, as i said, roughly 4 times the voltage, and i couldnt tell you how far that would require moving the volume knob to attain.
post #11 of 13
at reasonable long term listening levels the impedance, sensitivity differences really have little impact on battery life for these high levels of sensitivity

wether its 1 or 2 mA drain to drive either of these to >90 dB SPL, it isn't near the level of the rest of a portable player's current draw

lower sensitivity, higher impedance does give lower hiss with noisey sources, but IEM drive levels are so low that the only real solution to this is attenuation of the drive signal - external "hiss buster" resistor divider is inefficient, a quality step down transformer would be my choice if I had $K IEMs - a custom transformer pair could be used with many IEMs, a "one off" custom IEM would be much more exepnsive
post #12 of 13
Thread Starter 
Quote:
Originally Posted by jcx View Post
at reasonable long term listening levels the impedance, sensitivity differences really have little impact on battery life for these high levels of sensitivity

wether its 1 or 2 mA drain to drive either of these to >90 dB SPL, it isn't near the level of the rest of a portable player's current draw

lower sensitivity, higher impedance does give lower hiss with noisey sources, but IEM drive levels are so low that the only real solution to this is attenuation of the drive signal - external "hiss buster" resistor divider is inefficient, a quality step down transformer would be my choice if I had $K IEMs - a custom transformer pair could be used with many IEMs, a "one off" custom IEM would be much more exepnsive
Very eloquently put. Now I can move on.
Thank you.
post #13 of 13
Impedance is how resistive the whole system is to electrical flow.
Sensitivity is how efficient the system is.
They are not especially related.


Batteries can output less power as the potential difference between poles decreases.

By decreasing resistance of a headphone, assuming it still needs the same amount of power to get to say, 80 db, you require more current to acheive the same loudness. This means that the battery will drain faster (and thus potential difference and total charge remaining will)

If the headphone is less efficient (i.e. needs MORE power to get to 80 dB), you will also have faster drain if you push it to 80 dB.

The effect is fairly negligable compared to the rest of the DAPs power requirement.

The relationships I have drawn are mostly from ohms law.

Think of it like: lower resistance, faster electron flow, faster battery drain.
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