Impedance: The Power Juggler
Impedance is arguably the most vital term you need to grasp when choosing headphones. Simply put, impedance is electrical resistance - how well a device resists the electrical current passing through it.
This resistance, measured in ohms (Ω), indicates how much power your headphones need to reach an optimal listening volume. It acts as a yardstick, telling you how much you're going to have to crank the volume before things are comfortable.
The significance of impedance lies in its direct relationship with power requirements. Higher the impedance, the more power-hungry the headphones are. This means devices like smartphones may not be able to deliver enough power to these headphones, resulting in a quieter output, even at maximum volume.
This could also lead to the appearance of odd artifacts in the sound.
Interpreting impedance is straightforward. Headphones with impedance up to 32Ω can be easily driven by portable devices like smartphones. Headphones with impedance ranging from 33-100Ω lie in a grey area - you may achieve adequate volume, but the sound quality can significantly improve by using a portable headphone amplifier.
Headphones with an impedance exceeding 100Ω will almost certainly require an amplifier.
The reason for opting for highimpedance headphones lies in their ability to more accurately and vividly reproduce sound due to their enhanced capacity to handle electrical signals. However, this doesn't mean that lowimpedance headphones deliver poor sound. The impedance simply guides you to pair your headphones with the appropriate device for the best sound output.
Sensitivity: The Volume Dictator
Sensitivity is a measure of how loud a pair of headphones will play at a given power level. If one pair of headphones has a higher sensitivity rating than another at a power level of one milliwatt, the audio it produces will be louder at that volume. This implies you won't need to turn the volume knob too much to get more volume out of the headphones.
Sensitivity ratings range from a low of around 86dB (decibels) to a high above 110dB. However, sensitivity, also referred to as Efficiency or Sound Pressure Level (SPL), isn't the most reliable measure for comparing headphones as manufacturers may use different measuring methods.
Hence, it can be challenging to determine whether a pair of headphones will be loud enough.
High sensitivity isn't always advantageous. While it amplifies the music, it also amplifies everything else in the signal chain, including the hiss of your amplifier or phone circuits and electrical noise. High-sensitivity earbuds can pick up substantial noise if not paired with a high-quality amp.
Impedance, Sensitivity, and Bass Response
When it comes to bass response, both impedance and sensitivity play a significant role, albeit indirectly. Highimpedance headphones, especially when paired with a suitable amplifier, can often provide a cleaner, more detailed sound across all frequencies, including bass. They are less likely to be affected by output impedance variations in the source, leading to a more consistent bass response.
Low-impedance headphones, while easier to drive, might struggle with bass reproduction if the source device can't provide enough current. In such cases, the bass might sound weak or lack punch. However, with the right source or amplifier, low-impedance headphones can still deliver a fantastic bass response.
Sensitivity plays its part too. Headphones with high sensitivity tend to be louder at the same volume setting, which can make the bass seem more pronounced. However, higher sensitivity doesn't necessarily equate to better bass. In fact, if the headphones are too sensitive, they might distort at higher volumes, muddying the bass and the overall sound quality.
Practical Examples
We’ll be real here. When it comes to matching a pair of headphones with an amplifier or portable device to get the best sound, it’s possible to get very technical.
Before you know it, you’ll be deep into a world of voltage, current, output impedance of the amplifier, distortion, frequency variations, and whether or not you’re facing west at the full moon. All things considered, we’d rather avoid that.
Let's take, for instance, the Amazrock AB18 Headphone with 50mm Driver, a popular choice among super bass headphones with enthusiasts.
The Amazrock HD Extra Bass headphone, known for their powerful, immersive bass, serves as an excellent example of the relationship between impedance, sensitivity, and the overall listening experience. The AB18 is designed with an impedance (32Ω ± 15%) and sensitivity (108dB ± 3dB) that are perfectly balanced for common devices like smartphones and laptops, eliminating the need for an additional amplifier.
This balance ensures that the impressive bass response is delivered at an optimal volume level, without any distortion or loss of detail in the mid and high-frequency ranges.
As such, the Amazrock AB18 demonstrates how a well-considered balance of impedance and sensitivity can significantly enhance the audio output, particularly for those who favor a robust bass response. While there are plenty of in-depth explanations available online, we think that for most people, they simply aren’t necessary. If you have a basic knowledge of what impedance and sensitivity are, you will quickly be able to match a pair of headphones with a suitable source.
More importantly, let’s give it a try with one of the best pairs of headphones we’ve ever tested: At around $4,000, the Focal Utopia would require you to make a significant investment. Nevertheless, just like any other headphones, they have an impedance figure and a sensitivity figure. They have an impedance of 80Ω and a sensitivity of 104dB, indicating that they are moderately loud and require a decent amount of power to drive efficiently.
The Utopia headphones would work best when paired with a good headphone amp, although it is theoretically possible to simply plug them into a smartphone. You won’t get decent volume if you do that, however. And it would be a disservice to a truly brilliant pair of cans.
On the other hand, the $99 1More Triple Driver In-Ears offer an impedance of 32Ω and a sensitivity of 99dB. They are moderately loud and don't require much power to drive, making them suitable for direct plugin into a smartphone. For enhanced sound quality, a specialist digital audio player would be a good investment.
Final Thoughts
It’s possible to get very technical about matching an amplifier to a pair of headphones, delving deep into the specs.
However, for most people, a basic understanding of impedance and sensitivity will suffice.
Each pair of headphones and amplifier has its own unique sound characteristics, adding another layer to this audio experience. But, that's a topic for another time."
This provides a comprehensive view of practical examples that range from highend headphones like the Focal Utopia to more affordable options like the 1More Triple Driver In-Ears and the Amazrock AB18.
Image Credit: B&W
