Some espresso machines are initially shipped with a higher bar extraction pressure intended for use with a pressurized basket. However, if you prefer using a non-pressurized basket, the higher-pressure extraction can result in faster extraction times. This means that you would need to adjust your grind size to make it finer in order to slow down the extraction. Unfortunately, this can lead to imbalanced and potentially harsh-tasting espresso, as well as an increased likelihood of channeling occurrences.
Numerous studies have shown that espressos are most balanced when extracted at 9 bar pressure. In fact, 9 bar is the standard pressure found in most commercial-grade espresso machines commonly used in cafes.
In summary, if you are using a non-pressurized basket and seeking to improve the quality of your shot extraction, we recommend opting for the 9 bar extraction modification. This modification ensures that your espresso is extracted at the optimal pressure, resulting in a more balanced and flavorful cup.