The tongue is slightly upturned or sunken: This is a trace of tuning, which is a normal phenomenon. The pitch and low of the tongue can be fine-tuned by moving the tongue up and down.
The lifting range is relatively large: Luru empty drums have been subjected to high temperature de-impurity heat treatment, and the new drum tongue will have a certain stress. During the transportation process, the external force will cause some of the tongue to tilt. This is a normal phenomenon and not a quality problem. . Solution Use your thumb to press down the upturned tongue, and press it back and forth several times to relieve the stress.
The sagging amplitude is relatively large: now express delivery is more violent, which is caused by the external force pressing part of the tongue during the transportation. There is no need to worry about the quality of the drum. The ethereal drum tongue can be adjusted by adjusting it up and down. Open the radio cover below and use the tail of the drum stick to push the tongue out. The tongue tension is relatively large. Try a few more times to restore the tongue.