Originally Posted by Ratamacue
If I'm understanding your comment on the 17.4 angle at the MLP => it's based on 1/3 rule (24 / 3 = 8 and 11 / 3 = 44in) which is to get into the ballpark to avoid room modes etc.. Its close I suppose, but with only 11ft, there isn't a lot space width wise. By design, it leaves room behind and to the sides of the speaker. They aren't buried in the corner or next to a wall / boundaries. As you pointed out, there are many options for placement and I'll try some at the 30deg (closer to side walls) and see how things correlate.
Also, the subs in the current spot offer great integration so far (corner loading/reinforcement). I can't tell where they are. If I move them closer to the back of the mains (say 1ft behind), they seem to be in a null and don't produce much low end at all.
Attached is my layout, thanks again for your time.
BTW, I don't believe you attached your layout to your post. The missing piece of information is the current placement of your two subs.
Regarding the distance between your mains, I was only presenting information on an accepted placement principle, that is having the MLP, left front, and right front form an equilateral triangle. Your current 44" distance produces the following:
Angle "A" is 17.4 degrees, considerably smaller than the 30 degrees you would have with an equilateral triangle. In the worksheet I have, I can simply vary the distance "a" until the formulas result in a 30 degree angle. This occurs when there is 41x2=82 inches between the mains, leaving 25" from each main to the side wall.
I don't know if this placement would be acceptable to you, or how it would alter the sound, but I think it is worth a try. Clearly, the different spacing between the speakers would alter the width of the soundstage, which I think could be beneficial for two-channel music. Another thing to consider is that the current placement of the mains puts them at the 1/3 point of the room length, as well as the 1/3 and 2/3 points of the width. Moving the mains to where I suggested places them at the 1/5 and 4/5 points of the width, which I suspect will also alter the overall frequency response in the room. Whether this would be an improvement or not, only an experiment will tell.
And finally, while you may not find this recommendation to your liking, I would experiment by setting the mains to small, and crossing over to the subs at a higher point, say 80Hz. Why? Because the smoothness of the bass is all about positioning. With the mains, you have a conflict. Either they are placed to provide the best imaging, or they are placed to provide the smoothest bass. These two objectives can rarely be satisfied by one placement. So, position the mains for best imaging, and position the subs for best bass. I am assuming you have significant latitude WRT sub placement. Anyway, you probably know all this, since I am only repeating conventional wisdom.
WRT your question about the measurement levels and the shape of the waterfalls, if you go back and check, I think you will find that it is the change in the Time Range setting from 600ms to 450ms that produced the biggest change in the appearance of the waterfalls. The guidance that has been given here is to first measure your listening room's noise floor (typically in the 45dB-50dB range), and then measure at a level that gives you 40dB of clearance above the noise floor. Interpreting the resulting waterfalls continues to be one of the more difficult concepts to grasp. You can read the REW help section on waterfalls, but you may come away even more confused. If I recall guidelines we received from John M., he said to focus on the first 20dB from the top of the graph. Look for uniformity in the time slice waves in the first 20dB. Closely-spaced waves producing deep "ridges" are an indication of trouble at that particular frequency.
So, in your waterfalls, I would pay attention to the marked areas:
I don't recall seeing frequency response graphs of the mains+subs. My recommendation would be:
- Experiment with the equilateral triangle placement of the mains, focusing on imaging improvements.
- Set the mains to small with an 80Hz crossover.
- Measure bass response, first with subs alone, then with subs+mains.
- Experiment with sub placement to optimize bass frequency response.
- Once frequency response is optimized, look at the waterfalls/spectrograms. if bass ringing above 30Hz is not as good as you want it to be, consider adding room treatments.