Direct Sound, LLC – There are many different headphone styles and designs on the market today. Deciding what type works best for your personal recording environment can be confusing. In this post, our goal is to help you understand the benefits isolation headphones have for recording environments and an understanding of the closed-back design isolation headphones are built around.
A closed-back headphone keeps sound from escaping out of the back and generally offers a truer-to-original audio quality and frequency response. This is a very different design from Open-back models on the market. Open-back headphones have their place in certain situations, but this post will focus on the benefits of the closed-back design and specifically the reasons a closed-back headphone is best for isolation and critical recording and monitoring.
A closed-back design allows sound to focus towards the ears in a one-way direction, without the distractions of noise leaking in through the back of the headphone enclosure as with an open-back design.
Here are three key benefits of a closed-back isolation-style headphone
Better Sound Isolation
Closed-back headphones help eliminate outside noise from leaking in (and out) of the headphone for a better and more accurate listening experience. This means you can hear more accurate detail during monitoring, even at low-monitoring volume levels. When mixing or mastering, this level of detail and authentic sound is critical to achieving a great mix.
When external sound and ambient frequencies leak into a headphone mix, you will tend to mix from an inaccurate perspective. This is because the mix you are hearing is not a true representation of the music you are hearing. The ambient frequencies and sounds will color the mix and cause you to accommodate for the ambience in the adjustment of EQ, volume and other critical audio effects.
Leakage is a term that describes what happens when audio emanates into or out of the ear cup because of poor or inferior design. In the studio, “click bleed” is a common problem and an example of sound leakage. Click bleed occurs when the sound of the click used during recording leaks out through the headphones and gets picked up by a live mic and mixed in with the audio the mic is intended to pick up.
Once click bleed happens and becomes part of an audio track (also known as being “printed” on an audio track), it’s almost impossible to eliminate it, and usually requires a track to be scrapped and re-recorded.
Better Low Frequency Reproduction
Loudspeaker cabinets are tuned by design for superior low frequency reproduction, and the ear cup of a closed back headphone can be tuned as well. This means that the bass frequency is truer to the original track, and can go a long way in helping ensure that a track being mixed or mastered is as accurate and true as possible.
Additionally, some active headphone models (active meaning a headphone that uses batteries for power) pump up bass frequencies to enhance the listening experience and meet the consumer market’s trend towards pumped-up bass in a mix. While this may be great for general listening and enjoyment, this pumped-up bass effect can have undesirable effects for your final mix because you will tend to dial bass out of a mix when it’s enhanced, making the final mix sound lifeless.
Best to rely on a well-designed closed-back ear cup for accurate bass reproduction.
Isolation Headphones and Extreme Isolation Models
Isolation is a headphone quality specific to closed-back designs. This is because it is sonically and acoustically impossible to isolate sound in an open-back design headphone because, by design, the sound is going to be distributed in and out of the headphone.
The measure of isolation is labeled as Noise Reduction Rating (NRR), a designation that was created by OSHA for headphones used in workplace environments.
There is a lot of misinformation about what a Noise Reduction Rating is, and isn’t, particularly as it relates to headphones for music applications.
If a pair of headphones claims “isolation,” the first spec you should look for is the NRR. Many headphones that claim to be isolation headphones have never been tested for noise reduction and don’t have an officially Noise Reduction Rating. For this reason, the claims of “isolation” are misleading and mis-informational.
A true NRR is a reflection of the level of sound, measured in decibels, that a headphone isolates across the entire frequency spectrum, from a low of 20Hz to a high of 20kHz. The process of determining accurate NRR is a very important point to understand.
Isolating sound at the high end, such as the 20 kHz level, is not nearly as difficult to achieve as isolation for frequencies in the 20 Hz to 50 Hz range. Without getting too technical, this challenge is due to the way that sound waves travel, in addition to the fact that low end frequencies are generally felt as well as heard.
Some headphone manufacturers will claim a Noise Reduction Rating of 36.7 dB, which is technically higher than the 29 dB or the 25 dB NRR headphones such as the Direct Sound EX-29 and EX-25 claim respectively. But this is where you need to dig deeper to get accurate information.
It’s probably true that the headphones that claim this do isolate 36.7 dB at the high end, or at 20 kHz. Note that the Direct Sound EX-29 and EX-25 isolate 36.7 dB at 20 kHz. But this is not the headphone’s true Noise Reduction Rating. That is because when you factor in the low frequency noise reduction spec, which is much harder to isolate as mentioned before, the 36.7 dB spec can drop dramatically.