As a recording studio owner I often am asked to sit and observe band rehearsals. I have found that while some groups have productive and meaningful rehearsals many instead opt to hold cacophonous noise orgies that consistently result in soreness, shame, and despair. So because of this fact I have compiled this quick list of reasons why you should do yourself (and the rest of us) a favor and turn that shit down!
1. Too Much Mud
The first reason is that many bands rehearse in small, rectilinear practice rooms. From an acoustics standpoint, loud volumes can be particularly problematic in these settings and will keep you from hearing each instrument clearly. This is most noticeable when trying to properly hear the band's lower frequencies. By turning down a group can mitigate the "low-end build up" inherent in small rooms and will start to hear things clearer. Additionally, coating the room in 4"-6" of compressed fiberglass insulation can help to absorb some of this sonic mud. The classic example of this is when a band comes into the studio to realize their rhythm guitar player has been playing wrong notes since day one. Don't be that band, turn it down.
2. I'm Getting Tired
The second reason practicing too loud can hold you back is that it will fatigue your band faster. Sound is powerful shit, in fact it is so powerful that at a certain decibel level it can actually vaporize human flesh! Although the amp you just picked up off of craigslist won't boil the dermis off your bones it can put stress on the body if exposed for too long. Additionally, non electric instruments will need to compete for volume. Meaning your drummer will have to play harder, your vocalist may need to strain their voice to be heard, and your acoustic guitarist... well hopefully you don't have one, because he or she will be utterly fucked. All of these players needing to play harder just to compete for volume can and will lead to the band throwing in the towel early. Err on the side of caution and turn it down.
3. Loud and Soft: A Love Story
The third reason rehearsing too loud can have adverse effects on your band's success is that it often ignores the power of dynamics. When everything is loud all the time your band loses one of its greatest compositional tools. By playing quieter in certain sections of songs and louder in others you provide your audience with a more engaging listening experience. You will have effectively taken your fans on a deeper more meaningful journey through your music as opposed to blaring your message in their ears for four minutes before moving on to your next advert. Additionally, being able to play at softer volumes will make your band more marketable. The classic example of this is the loud rock band not getting a call back because they were too loud for the venue. Some event spaces are not ideal for loud acts, but it doesn't mean that a typically loud act can't play those venues with success. Learning how to control your band's volume in rehearsal can become an indispensable collective skill set at home and on the road.
By being mindful of these three areas of concern you will find that your rehearsals will become more productive, more focused, and will make your band more versatile. So go forth and turn it down to 10!