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Before we get into the question of What is Sensitivity in Headphones, grab a snack, sit back and relax because..
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What I will bring you in this review
- Sound Pressure Level
- Need an amp?
- Final Word
Now without further ado, let’s get rolling!!
I previously never gave the word Sensitivity attention. For the longest time, it was just an obscure term that you could find in the Specifications area of most audiophile headphones. It was just a number and didn’t mean a whole lot.
In reality, it’s pretty important in determining if your headphones need amplification or not.
What is Sensitivity in Headphones?
To begin, we must understand that there are a few terms here that are interrelated and co dependent on each other:
- Sound Pressure Level
- Amps & Impedance
Sensitivity is how efficient a headphone driver is at using the power it receives. What is a Headphone Driver? This power is used to deliver to us the sound we hear (free of distortion).
It has to do with how the headphone responds to voltage. A headphone might require a large amount of voltage to drive, but not necessarily consume a lot of power.
Sensitivity is measured in either dB/mV (decibels per millivolt), while efficiency is measured in dB/mW or dB/W (decibels per milliwatt/watt).
Efficiency has more to do with energy transfer, meaning if you put a certain amount of watts in, you’ll get a certain Sound Pressure Level out.
So, a headphone with a low efficiency will require a ton of power to produce an adequate Sound Pressure Level.
Sound Pressure Level
Sensitivity also lets us know how loud the headphone can be according to the level of power it receives from the source. It’s measured in decibels, and most headphones don’t need more than 1 milliwatt of power to produce a high Sound Pressure Level. What is SPL?
It’s important to note that having more or less than a mW of power will not double or cut in half the SPL, respectively.
So for example, if you have a headphone with an SPL of 100 1 mW, 2 milliwatts wouldn’t result in a 200 SPL.
Need an Amp?
Essentially, a headphones sensitivity and efficiency will help you determine if it requires an amp to reach a listenable level. For instance, the Sennheiser HD600 absolutely requires an amp to sound good, because it’s not that efficient on it’s own. There’s just no getting around it. If you plug it into your phone or laptop without even a DAC, it’s going to sound distant and quiet.
An example of a higher sensitivity headphone would be the Samson SR850. It’s pretty efficient regardless of what you plug it into. I used it with my Schiit Magni/Modi and didn’t even have to turn the volume past 10 ‘o clock to get to a good listening level. Anything past that would have proved to be too harsh and sibilant. What does Sibilant mean?
So the takeaway is that it did benefit from an amp, but less so than a low sensitivity headphone.
A headphone with a higher impedance will almost always require an amp because there is more current that it must provide. What is Headphone Impedance? The amount of Ohms dictates this relationship that we’ve been discussing between resistance, current, and voltage.
The higher the resistance, the more current that is needed. This is the “load” presented to the amplifier.
An example would be the Grado SR80. It has an impedance of 32 Ohms, and a Sound Pressure Level of 98dB. Pretty efficient, but not extremely. A very efficient headphone like the V-Moda Crosssfade M100 would exceed the 100 dB mark.
So, the SR80 needs more power to reach a given volume, but presents less of a load to the amp because of it’s low impedance rating. You won’t have to turn the volume knob up hardly at all with it plugged into a good amp. How to choose a headphone amp!
Sensitivity in headphones is a tricky subject, but shouldn’t have to be all that complicated. Generally, a headphone with around 95dB or below isn’t that efficient, and mostly comes in the form of planar magnetic headphones, or other higher end audiophile type gear. A headphone that’s around 100dB and greater is very efficient, and doesn’t need an sort of amplification to sound good. The internal amp in your mobile device should suffice.
Well that’s about it for today my friend! I hope I’ve answered your question of What is Sensitivity in Headphones?
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