Dumb question about sensitivity.
Dec 10, 2019 at 2:44 AM Thread Starter Post #1 of 7


100+ Head-Fier
Mar 8, 2010
Hi All.
May I ask for simple clarification if possible? I have a HiBy R6. It has high output impedance. I’m trying to understand the comments about high sensitivity iems.
There are figures always published with every pair and a general warning from HiBy owners to avoid low impedance iems (seems a rule of about 16 ish) but also ‘highly sensitive’ iems.

So, what ??? db mW is considered ‘sensitive?’
90,100,110? Etc.

huge thanks for any answers.
Dec 10, 2019 at 9:28 AM Post #2 of 7
Hi @Tooros,

This is not a dumb question by any means & while I am no electrical engineer, I can at least help you with your question.

Before we get into output impedence, high or low, it is important to understand what impedence is & what it does to an electrical signal or in this case, the audio signal, in general terms.

Impedence is basically the rated resistance an electrical signal has against the resistor &/or electrical component.
In other words, impedence is like a water tap or dam sluice where water or in this case, electrical current is controlled, by turning said tap or how large or small that dam sluice is to open or close.
As electrical current acts the same as water, the path of least resistance.
This is one reason among many why impedence &/or resistance exists.

Sensitivity is slightly different to impedence as it is the rated volume audio equipment can reach without distortion, clipping or excessive noise though this is not a hard & fast rule either.
Basically anything from 96 db + is considered sensitive or loud for head gear in general though this will also depend on the following aside from impedence :

Frequency Response
Max Input Power Handling &/or Cpntinuous Input Power Handling
Sound Isolation (If applicable)
Sound Tuning

As such, sensitivity isn't limited to IEMs as 'sensitive' headphones can potentially have more an issue than IEMs but both can be potentially problematic.
In this way, High Output Impedence can be a problem for sensitive head gear though it may often be more a problem for human hearing as the feedback is more damaging to what we can hear than the actual gear but this doesn't let said gear off the hook, so to speak as behind that High Output Impedence is potentially high current which will potentially damage any output device attached to it.
As a general rule, for example, when connecting head gear to an amp or source device, make sure the volume is 0 to avoid feedback which can potentially damage your hearing &/or equipment.
This is why head gear generally shouldn't be connected to an amp or source device when it is off either unless explicitly stated by the manufacturer there is a protection circuit built in.

Hope this all makes sense, feel free to ask more when needed.

Hope you have a great day !
Dec 10, 2019 at 3:07 PM Post #3 of 7
Hi All.
May I ask for simple clarification if possible? I have a HiBy R6. It has high output impedance. I’m trying to understand the comments about high sensitivity iems.
There are figures always published with every pair and a general warning from HiBy owners to avoid low impedance iems (seems a rule of about 16 ish) but also ‘highly sensitive’ iems.

So, what ??? db mW is considered ‘sensitive?’
90,100,110? Etc.

huge thanks for any answers.

Sensitivity is rated at xxdB/1mW. That's roughly how loud it can potentially go with 1mW input,* and every additional 3dB in volume will require doubling the power input.

Too high sensitivity on a high noise amplification circuit or in some cases too low sensitivity with too high sensitivity can be a problem, like on the SE535. High output impedance on the headphone amp circuit can exacerbate that. Note however that this is not always universal, just like damping factor dropping and bass getting too loose if not also boosted when the output impedance isn't low enough, like how it's really easy to get noise on a 35ohm Shure SE530 at 119dB/1mW than a 32ohm Aurisonics ASG-1 at 120dB/1mW, while it's a lot easier to end up with loose bass on the Aurisonics than the Shure.

As for what is considered "sensitive or high sensitivity," that tends to have more to do with how easy it is to get enough power. On headphones 96dB/1mW on 250ohm Beyerdynamics is high enough, 99dB/1mW on 32ohm Grados are "really easy to drive," and newer headphones with roughly 32ohms and 102dB/1mW are along the lines of "easily runs on a DAP" (sic), all in lieu of accepting the need for a good portable amp at least.

With IEMs the scale moves a bit. An Etymotic with 94dB/1mW would be considered really effing low and only offset by really good isolation (sic), 105dB/1mW, VSonics and KZs at 105dB/1mW is still kind of low for an IEM, some good IEMs like the SE530, Westone2, and ASG-1 are high sensitivity, and then there's the Westone UM3X at 124dB/1mW being practically the Grados not just be their relative position (and even higher) in the sensitivity rankings but also because it has strong response in the upper bass that together makes music easier to groove to as it enhances the beat without really wanting more than 10mW even for dynamic peaks. This is due to how many would expect them work well on a decent smartphone with at most 15mW of power (and even less than that of clean power).

Heck on speakers it can vary since they can be rated with xxdB/1W at 1m distance (unlike headphones measured at drum reference point, though some measure at ~1in from the driver), each listener's room can have a different seating position distance and other acoustic properties that can alter the response and ergo the perception of how loud it is or how loud it needs to be cranked up (and ergo power), so in some cases "sensitive" on passive, non-nearfield use speakers can be "91dB/1W at 1m can work with a 3watt tube amp, sounds great from 2m away."

Easy guide: just check what other people use on that DAP and what has noise, avoid those. If you don't like the ones that don't, then look for IEMs with impedance no lower than and sensitivity no higher than those that don't have any noise.

If you want to gamble on an IEM with a sound you like, maybe check if it has over 24ohm impedance and no higher than 110dB/1mW sensitivity.

*Note: that doesn't factor varying gain levels on recordings, differences in output per instrument as per mastering, the driver response, ambient noise, etc, so don't assume you will literally have for example 120dB as soon as you go past mute on a smartphone with something like an Aurisonics ASG-1.3 hooked up.
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Dec 10, 2019 at 3:19 PM Post #5 of 7
There are figures always published with every pair and a general warning from HiBy owners to avoid low impedance iems (seems a rule of about 16 ish) but also ‘highly sensitive’ iems.

In terms of IEM/player pairing, IEMs can be both low-impedance and highly sensitive, or they can be just one or the other. (Or neither.)

Speaking very generally, "highly sensitive" iems are more prone to picking up hiss/backkground noise if they are present in the source. I don't know if there's a consensus on what the threshold is for being very sensitive. The hissiest IEM I own is probably the iBasso IT01, which is 108db and 16ohm.

Low-impedance IEMs can react to a high impedance source in different ways, depending on the design of the IEM. The classic rule of 8 damping factor thing applies mainly to single dynamic driver units, and basically means that you may get bloated bass if your source output impedance is over roughly 1/8 of your headphone impedance. But the scenario that most IEM owners are more concerned about is that source output impedance can impact the frequency response of multi-driver IEMs. (I.e., if each IEM has multiple BAs, or one BA and one DD, etc.) And the tricky thing here is that you can't actually tell from the rated impedance of the IEM what level of output impedance is safe.

The two IEMs I have that are sensitive to source output impedance are the Massdrop Plus, which is a three balanced armature IEM at 10 ohms, and the BQEYZ Spring 1, which is a DD/BA/piezo hybrid rated at 40 ohms -- but if I plug into an amp with a high output impedance, the midrange driver freaks out and sounds like it's underwater. By contrast, the IT01 sounds great with that same amp, even though it's only 16 ohms. The difference is that the IT01 is a single dynamic driver, not a hybrid. Plus, you can't tell without testing what part of a multi-driver IEM's frequency response will be impacted.

tl;dr since you have the Hiby already, if you don't want to worry about IEM pairings, stick to single dynamic driver IEMs or IEMs that have been reviewed well with that particular player.
Dec 10, 2019 at 3:22 PM Post #6 of 7
Interesting you mention the it01. I have the same and to honest, I think they sound great out of the HiBy. I’ve got some kanas pros coming (single DD and 32ohm) so I’m not too worried. I’ll never get to $1000 multi BAs so I’m pretty comfortable. I wanted to better understand my long term options. I really appreciate all the help! :)
Dec 11, 2019 at 4:55 PM Post #7 of 7
To answer your questions:

1. Impedance is Resistance, but it varies with frequency. Since headphones and IEMs are used for listening to music (voltage at different frequencies), the "resistance" of a headphone can vary and is referred to as impedance, instead. For instance, a Sennheiser HD650 generally measures about 300 ohms. However, if you plot that impedance from 20Hz to 20kHz, you'll find a huge spike in impedance at 100Hz - as high as 500 ohms or more:

IEMs can be similar. Some might be flat all the way across 20Hz to 20kHz, others can vary all over the place.

2. When it comes to volume level of a headphone or IEM, the sensitivity of the headphone/IEM, combined with the gain of the amplifier, is almost always predominant. It's why you see so many people around here (and elsewhere) claim they get "sufficient volume" from the sound card on a PC with a 300 ohm Sennheiser HD800 or similar. It does not mean they get quality sound with that pairing.

3. Any headphone/IEM sensitivity approaching or exceeding 100dB/mW is VERY sensitive, IMHO.

Typically (and maybe unfortunately), if someone advises you to watch out for high-sensitivity IEMs or headphones with a particular amplifier, it usually means that amplifier has one of two issues (or both): a) residual background noise that is masked by lower-efficiency headphones, or b) a volume control that leaks sound at the bottom volume setting or has a noticeable volume imbalance at normal listening levels.
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