Previously (in part 1), i had explained about the significance of impedance in headphones and it's effect on loudness and quality of the sound delivered, in this part, we'll be going a bit deeper into the following -
1. What is impedance matching ?
2. Significance of impedance matching
3. Sensitivity
4. When you require an amp
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1. Impedance Matching
It is a process that helps in extracting the best audio quality from a headphone. Each headphone comes with a particular impedance that is used to match with the impedance of the source that you're connecting to.
There exists a rule called "the rule of eighths" which states that the output (source) impedance should be less than 1/8th of the headphone impedance. For example, if someone purchases a headphone with 250 ohms, then the source impedance should be less than 31 ohms. Though decent results can be achieved with slightly greater source impedance, it should be kept in mind that there will be some deviation in the frequency range.
So in this case, when we apply the 1/8th rule, the phone output impedance should ideally be 37.5 ohms
(300/8=37.5) but as stated earlier you can still get away with a
little mismatch with only a slight deviation in the frequency range.
2. Significance of Impedance Matching
For general use/casual listening, an impedance mismatch doesn't really matter much because the differences aren't really noticeable but when it comes to studio application/critical listening, it is very important that there is proper impedance matching else there will be some sort of frequency deviation (i.e. coloration) which will mislead the listener during a mix session etc.
In some cases there will be distortion, especially in the high frequencies and sometimes when you connect a high impedance headphone into a mobile phone or PC, there will be insufficient output volume which can be sorted out by using a suitable amp.
3. Sensitivity
In a nutshell, sensitivity refers to how loud the headphone can get. it also tells us how efficiently the electrical signal gets converted from the source device to an acoustical signal. More the sensitivity, more the loudness and vice versa. Similarly, more sensitivity requires less power while less sensitivity requires more power to obtain substantial loudness.
It should be kept in mind that a headphone with high sensitivity can also produce distortion at very high volume and may even damage the driver. It is advised to stick to a sensitivity rating of 100 dB which is a safe zone in terms of loudness (90dB is on the lower end while 110 dB is on the higher end).
4. When you require an amp
As discussed in part 1, there are 2 types of impedance - high and low. A headphone with an impedance rating of 100 ohms or more requires an amp to achieve substantial loudness. On the other hand, headphones with less than 50 ohms don't require any amplification as they are loud enough by nature.
But buying an amp blindly will lead to more complications, so before one can invest in an amp, a ton of research should be done so that it actually compliments the headphone that is going to be plugged into. Factors such as impedance matching, rated sensitivity etc should be kept in mind while investing in an amp.
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Hope you all got an idea of what impedance matching and sensitivity is and the roles that they play in delivering proper sound quality - atleast to some extent. Had to do a ton of digging so that i could put it in the simplest way possible. If you've any queries/feedback do drop them in the comments below, will surely check them out. I will also be coming up with a headphone buying guide that'll help you decide what you want and what you don't want when it comes to headphones. So stay tuned!!
Check out the links below if you want to dive deep into the technical stuff -
1. NwAvGuy
2. Headphones impedance demystified
1. What is impedance matching ?
2. Significance of impedance matching
3. Sensitivity
4. When you require an amp
ーーーー
1. Impedance Matching
It is a process that helps in extracting the best audio quality from a headphone. Each headphone comes with a particular impedance that is used to match with the impedance of the source that you're connecting to.
There exists a rule called "the rule of eighths" which states that the output (source) impedance should be less than 1/8th of the headphone impedance. For example, if someone purchases a headphone with 250 ohms, then the source impedance should be less than 31 ohms. Though decent results can be achieved with slightly greater source impedance, it should be kept in mind that there will be some deviation in the frequency range.
 |
| The headphone on the top is the Sennheiser HD 650 which comes with an impedance of 300 ohms and the one below is the Steinberg UR22 MK II which has a phone output impedance of 40 ohms. |
2. Significance of Impedance Matching
For general use/casual listening, an impedance mismatch doesn't really matter much because the differences aren't really noticeable but when it comes to studio application/critical listening, it is very important that there is proper impedance matching else there will be some sort of frequency deviation (i.e. coloration) which will mislead the listener during a mix session etc.
In some cases there will be distortion, especially in the high frequencies and sometimes when you connect a high impedance headphone into a mobile phone or PC, there will be insufficient output volume which can be sorted out by using a suitable amp.
3. Sensitivity
In a nutshell, sensitivity refers to how loud the headphone can get. it also tells us how efficiently the electrical signal gets converted from the source device to an acoustical signal. More the sensitivity, more the loudness and vice versa. Similarly, more sensitivity requires less power while less sensitivity requires more power to obtain substantial loudness.
It should be kept in mind that a headphone with high sensitivity can also produce distortion at very high volume and may even damage the driver. It is advised to stick to a sensitivity rating of 100 dB which is a safe zone in terms of loudness (90dB is on the lower end while 110 dB is on the higher end).
4. When you require an amp
As discussed in part 1, there are 2 types of impedance - high and low. A headphone with an impedance rating of 100 ohms or more requires an amp to achieve substantial loudness. On the other hand, headphones with less than 50 ohms don't require any amplification as they are loud enough by nature.
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| The Beyerdynamic DT 770 PRO (80 ohms) being connected to the Fiio E11 headphone amp. 80 ohms lies in the grey area which means amplification is not really necessary at all times. |
ーーーー
Hope you all got an idea of what impedance matching and sensitivity is and the roles that they play in delivering proper sound quality - atleast to some extent. Had to do a ton of digging so that i could put it in the simplest way possible. If you've any queries/feedback do drop them in the comments below, will surely check them out. I will also be coming up with a headphone buying guide that'll help you decide what you want and what you don't want when it comes to headphones. So stay tuned!!
Check out the links below if you want to dive deep into the technical stuff -
1. NwAvGuy
2. Headphones impedance demystified
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