I had no choice but to setup on a stage last night. The L1 mII was a good 3-4 feet off the ground, pushed back 10 feet from the edge.
Certainly sounded different than usual.
What should be my expectations when raising the L1 since it can't act as a linear array b/c there is no boundary effect from the floor coupling.
Does 3-4 feet have the same effect as if it were 1ft off the ground?
And what about pushing it back as opposed to on the edge?
Kind of a few questions here....
Hi jaswrx,
Interesting questions.
jaswrx posted:I had no choice but to setup on a stage last night. The L1 mII was a good 3-4 feet off the ground, pushed back 10 feet from the edge.
If you have 10 feet of stage directly in front of the L1® you were still getting some benefit from the floor reflection.
Certainly sounded different than usual.
What should be my expectations when raising the L1 since it can't act as a linear array b/c there is no boundary effect from the floor coupling.
The L1® is acting as a line array even if there were no floor. It just won't project as far.
The reflection of the floor enhances the line array aspect. You were still getting some of that.
Does 3-4 feet have the same effect as if it were 1ft off the ground?
People whose heads are not within the approximately 80" vertical coverage will not hear the system as well. If people are seated 3-4 feet below the bottom of the L1®, the L1® will sound muffled. If people are seated 1 foot below the bottom of the L1®, the sound should be clear.
And what about pushing it back as opposed to on the edge?Kind of a few questions here....
Even if the L1® is at the front edge of the stage, it's still acting like a line array, but the effective distance may be shorter.
Here are some more notes from a previous discussion: Does elevating the L1™ change the line array performance?
Ken-at-Bose posted:My explanation will on the one hand sound nice and neat but in reality the answer is messy and fuzzy.
Caveat emptor.
A nice big hard massive floor can be thought of like a mirror with light. When you put the L1 system against the floor, the effective length doubles because of the mirror image L1 created by the floor (the mirror).
The next interesting thing is that with line source, when you double the length (i.e. add the effect of the floor) you effectively QUADRUPLE the "line-sourced-ness". So, for example, if you observe a certain "line-sourced-ness" at one distance with a line source of some length, then you will observe the same line-sourced-ness at FOUR TIMES the distance if you double its length.
Similarly, if you observe a behavior at one frequency for a line source of a particular length, then you will observe that same behavior at ONE FOURTH the frequency if you double the length of the line source.
Pretty cool.
Now, when you raise the L1 system off the floor, you create a gap between the L1 system and its mirror image equal to twice the height you raise it off the floor. Said another way, you create an array of two L1 sources separated by twice the height off the floor. At higher frequencies this will create a shadow zone in coverage -- okay if the only thing in that shadow zone are legs and knees of the listeners. The benefit is that more ears can "see" more of the L1 source.
But at least some (this is the fuzzy and messy part) of the benefit of "pure" double-length, four-times the effect, line source are diminished because of the gap.
A stage lip is of course an even messier situation. The "mirror" isn't flat but has two offset surfaces, and this creates a more complicated set of image sources. Again, some of the effectiveness of having a big flat floor plane are going to be diminished.
I hope this is of some help to the community.
(Many thanks to Chris-at-Bose who gave me years ago the most lucid explanation of line source behavior, much of which I'm drawing on here.)
Ken
Chris-at-Bose posted:It's hard to untangle this question, because we are talking about four factors that affect throw: having a big flat floor under an L1 (as opposed to no floor at all), the obstruction caused by a lot of people, raising the L1 above the floor, and "lowering the floor only out where the audience is" to make an elevated stage. What is confusing is that the answer about throw distance depends on which combinations of these effects we mean to include. I think there is a way to step through this in a sequence that will give a useful answer for all the combinations encountered in practice.
Start with an L1 suspended in mid-air. Call its throw distance the "bare L1 throw". (I know, we don't encounter this, but it's a reference condition.)
Now put the L1 on a big, flat, hard, empty floor. As Ken said, the new throw distance will be four times the bare L1 throw.
Now add a dense mass of people on the floor. (Popular, aren't you! They must love you and your Bose sound.) They block virtually all the sound reflected from the floor (taking the floor effect out of the picture) AND they block some of the direct radiation from the L1. So the real throw distance now becomes less than the bare L1 throw, possibly far less. Call this the "obstructed throw". Most of us have experienced this at one time or another, unless you're never popular.
Now raise the L1 above the floor. The actual throw distance improves as the L1 gets above the obstruction of all those people. If you hypothetically raised the L1 'way up in the air, you would get back to the bare L1 throw, but you won't actually raise it that high because the "sound layer" would go over everyone's heads and they would all hear muffled sound. So the throw you get by raising the L1 is farther than the obstructed throw, but not as far as the bare L1 throw. Notice that the floor effect is not a factor in your decision, because all those people are obstructing the floor anyway.
Now, with the L1 elevated, take away the people. What throw do you get? Who cares--put that L1 down, you no longer have a reason to elevate it. (Gotcha!) This trick allows me to avoid having to admit, "I don't exactly know". (Oh, I just did, didn't I. Never mind.)
Let's go back to the case where the L1 is elevated and you are so popular that the place is packed with people. Remember that the throw distance was between the obstructed throw (short) and the bare L1 throw (medium). Now quick, imagine a stage that elevates you up to where the L1 is. People see you better, but do they hear any difference? Basically, no. (I'll explain why in the next paragraph.) So you get the same throw as when only the L1 was elevated, some distance between the obstructed throw and the bare L1 throw. For the audience's ears, the elevated stage is the same as the elevated L1. But they do see you better.
So, why doesn't the stage sound different from just elevating the L1s? Well, as Ken said, you have to imagine the floor as a mirror. If the stage floor were a mirror, how much of the L1 image could the audience see in the floor of the stage? Typically very little. Most of the image is cut off by the edge of the stage. Since they can't see most of the L1 image, that image has little effect on the sound they hear. So, if the stage could be magically removed, leaving the L1s and performers floating, those in the audience would hear very little difference in the sound of the L1. (The bass would change, but we're not talking about that.)
I think that covers the bases. In summary, the only time you really get the 4x longer throw from the floor reflection is when the floor within 50 feet or so of the L1 is hard, flat, and sparsely populated, as it is in some extensive outdoor events. And you need the extra throw for sprawling events like that. When the floor is densely packed, elevating the L1s improves the throw, whether the means of elevation also raises the performers (i.e., a stage) or not.
If I don't mention it, someone will ask about the intermediate case where the density of people is moderate. As always, let your ears be your guide. If it sounds muffled in back, you have an obstruction problem and elevation will usually help. But I must remind you that safety has to come before sound quality. When you say you "killed the audience", we don't want that to be literally true. Be careful.
Hope this is useful.
Chris
Hi jaswrx,
I had a similar problem about a week ago. The stage we had to play on was about 32" high but I was lucky enough to be able to use a roughly 7' x 3'6" x 16" high podium which I placed directly in front of the stage. We played seated (as always) and the audience was state so no problem there, The gig went perfectly with really good sound for everyone. Your gig sounds even more problematical.
Here's a link to an article I published last week regarding my gig. Maybe it's of some interest to you.
https://www.bosepro.community/...and-a-single-compact
Sometimes we have to make compromises that are more than just compromises, and they don't do anything to really make us feel happy. Unfortunately sometimes we've just got to live with it.
If you have to do gigs like that and are interested as to what difference it makes setting up onstage or not, record the L1 sound in the room with the L1 set up in both positions (and with the recording level set to manual). Then you'll know. It's no big act to set up the L1 for such an experiment as you probably very well know.
Interesting subject, though. Thanks for bringing it up.
Tony
ST-
A few things--
Thanks so much for the notes.
It seem as:
If the L1 does not have boundary reflection, the line array properties of the far projection compared to point source are diminished. It will still have ultra wide dispersion, but the the distance won't be as far as if it were on the floor.
The ideal L1 situation looks to be outside with several feet away before the crowed as there are not guest blocking and they are not below or above it.
It seems that even though I was on a stage, ONLY I was getting the effects of boundary reflection since the people were much below that.
It actually seems like 16-24" is idel if playing where dancing happens right in front of the speakers.
I have noticed too many guests blocking the L1, and it sounds very muffled the further the way you get from it.
