These are some common tools used to work on this device. You might not need every tool for every procedure.
Background and Identification
The HD428 are headphones originally released by the German audio company Sennheiser in 2009 (the announcement is recorded in this thread on the Head-Fi forums). In terms of design, the earpads on the HD428 fit around your entire ear. The exterior and headband are made from black plastic, and the section near each ear can swivel up/down and forward/back to fit better on your head. The best way to identify this model is to look for the cross or “X” pattern on the outside of headphones. Each side has four sections which are raised above the main surface and have a dimpled texture. The sections are divided by an X-shaped flat section. The brand name “Sennheiser” is printed in this flat area.
The HD428 headphones can reproduce audio from 18 Hz tones to 22 kHz. They have a relatively low input impedance of 32 ohms, which means they will work well with a portable music player. Unfortunately, the cable on these headphones cannot be detached (at least without disassembling the device). You can replace the 3.5 mm stereo plug on the end if you are willing to do a little soldering. The most common issue with these headphones is that the earcups break down eventually. You can pop them off (as shown in this YouTube video) and buy replacements online.
- Frequency response: 18 Hz to 22 kHz
- Impedance: 32 ohms
- Cannot be disconnected
- 3.5 mm stereo plug
- Comes with 6.35 mm (1/4 inch) plug adapter
- 208 g (0.45 lb)