EP 27 Earpads replacement guide

Understanding the principles of headphones' acoustics. 

So called pad-rolling is a long standing tradition in the headphones' community. At some point, anyone exploring headphones will try to play with earpads and miraculously find a better earpad than the stock ones. 

Here's a short list of main principles of acoustics in headphones. 

1. airflow resistance on the surface of the earpads: How much air can escape and how easily will determine the prequency response of any headphones, specifically in the low mids and lows. Traditionally velour or similar top surfaces of the earpads (are in touch with your skin) will have less bassy response. And soft leather like materials will seal best, creating a boost in the low end.

2. absorbtion in the foam: Soft earpads are comfy, but they also absorbe more, usually the mids are affected the most. The softer the pads, less mids are presented. That's not always the case as other factors play a major role. But as a rule of thumb,...buying hard foam will boost mids and highs.

3. diffusion and reflection of inner layer materials: The material inside the earpads will create a very different resonance depending on it's hardness, shape (deformation after clamping force is present) and surface. Again, softer materials will absorbe more and may sound smoother. In some cases earpads will change the perception of transients.

4. size and shape of the cavity for your ear: Usually it's in a shape of oval or circle. Theoretically oval is slightly better but you need to understand that the volume of air left around your ears is less in this case. Less air, means more direct sound and usually less soundstage. Bigger pads will introduce more reflections and may resolve in two ways. Either bigger soundstage or loss of clarity with cancellation of frequencies in the higher spectrum. For example 6000Hz is where earpads size starts to introduce reflections and resonances. Wantend and unwanted.

5. clamping force: The more force you have on the headband, the more earpads are deformed and less volume is left inside the pads. That results in more SPL level and higher bass as the seal is stronger. Similar to room acoustics. Same speaker outside, then in a living room and then in a small closet...selfexplanatory.

You can watch a short vlog touching on all main principles and see results measured with an industry standard device, the GRAS 45CA - 711 coupler.

DOWNLOAD ALL MEASUREMENTS from the video here.