The band helps to fix sensors and get a strong enough signal. If the band is loose, the headband may fail to collect qualified signals to analyze. But if it’s tight, you may feel uncomfortable and find it hard to relax.

If no band brings the right pressure, knotting the larger one could shorten it a bit to put a comfortable amount of pressure against your skin, but not too much pressure. Generally, after making one or two knots you would find the sensor contact is improved and feel comfortable, too.