Point of first reflection

In yesterday's post, I wrote about acoustically treating the room. I had used a term unfamiliar to some. The point of first reflection. This is the point along the room's sidewalls where sound from the loudspeaker first strikes and then bounces off back to the listener. When this happens we get a delayed reflection in addition to the direct sound reaching our ears. (The sound is delayed because it is taking a longer path than the direct route) Here's a drawing I scrounged off the internet. By absorbing or diffusing that point of first reflection along the sidewall, you can dramatically improve the performance of your stereo system. If you refer to yesterday's post, I had recommended placing a tall bookshelf on both sidewalls as an attractive and effective means of diffusing/absorbing that reflection. Finding that point where sound first strikes is easy if you have the luxury of an assistant and a small mirror. Have your volunteer hold the mirror against their chest and place their back against the sidewall. As you sit in your listening position have them scootch along the wall until in the mirror you can see your speaker's tweeter. Bingo! That's where you place your bookshelf. (These tricks and tips are all covered in my book, The Audiophile's Guide)