Why did my headphones lose their bass?

The ear pads have compressed and no longer seal against your head. Bass response depends on that seal more than on anything electrical, and pads are a wear part — replacing them typically restores the low end completely.

Why it happens

Closed-back headphones rely on a sealed volume of air between the driver and your ear. Break that seal anywhere and low frequencies leak out instead of pressurising the chamber. A gap you cannot even see is enough to remove a substantial amount of bass.

Pads are polyurethane foam under a covering, and the foam takes a permanent set from months of clamping pressure. It happens gradually, so most people never notice the change — they conclude the headphones have simply aged, or that their hearing has.

Glasses are the other common cause. The arms break the seal along the temple, and the effect is immediate and reversible: take them off and listen to the difference.

What to do about it

1. 1Press the earcups gently against your head while music plays. If the bass returns, it is the seal, and new pads will fix it.
2. 2Replacement pads are widely available for most models and usually stretch on by hand with no tools.
3. 3Note that pad material changes the sound: leather-style covers seal tighter and give more bass, velour breathes better and gives less.