The SR404 Signature is the current flagship Lambda from Stax, if you consider that the 404LE is a special edition that recently has been finished of its production. Moving up to the 404 Signature, you get rewarded with an overall improvement on build quality and materials. The U-shaped plastic that holds the driver housing is thicker, the leather headband is thicker, the pads is of a higher quality leather, the cable joint out of the driver housing is beefier, and the cable is wider. Overall, the build quality certainly has improved, although in terms of comfort and ergonomics, the improvements are less evident. The earpads are still made of artificial leather, but it’s a better quality pads that’s softer than the one in the SR-Lambda. Also, visible from the housing grille is a red ring on the driver that looks like the one you find in the SR404 Limited.
Before we continue, here are some photos illustrating the differences between the three headphones: