# first reflection points:right and wrong ways?



## terry j (Jul 31, 2006)

Hi all

I hope I can explain my question clearly, it would help if I was good at using paint or something, but I'll try a verbal description first.

Room treatment, yes I'll get to it one day, but as I have to renovate the room yet, no point doing it fully just now.

First reflection points, I understand what they are and how to determine where to put the absorption, ie the old mirror trick. I have always assumed that, in my room at least, treating the first reflection point might not yield the benefits it can give in a lot of rooms, simply because my speakers are around two meters or so from the side walls, hence any delayed reflection should be outside the critical zone timewise.

However, I did borrow some ugly looking room dividers, you know, the ones we often see in offices etc, and as a quick experiment I threw them in, and blow me down if it didn't help heaps!!

So, notwithstanding my large room (roughly 9m wide, 5m deep with a bay of a further 2m behind the LP, and 5m ceilings) I think I will go on and make some nicer looking treatment panels.

BUT, due to the layout I'm unable to permanently mount them on the wall for the first reflection points, there is a door in the way, so some sort of screen on castors will probably be the way to go.

FINALLY the question, hope I didn't bore you getting here! Is there any difference in the final result between an absorption panel on the wall at the FRP (first reflection point) or an absorption panel next to the speaker, yet placed so it intercepts the sound before the wall??

In other words, does the sound from a speaker 'need space to develop' as it emanates out, which development might be interfered with by placing a screen beside the speaker. Does that make sense??

If no different, then is it a logical extension to posit that there would be benefits from say surrounding the speaker on all sides by a screen? thereby preventing 'any' room reflections.

Hope you can follow that ha ha


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## bpape (Sep 14, 2006)

Yes - it's a lot different.

When doing a panel against the wall, you're only damping the sound there. With a panel right next to the speaker, you're also damping some of the bottom end from spreading out as well as a lot of other sound that would have gone other places in the room besides the reflection points.

Bryan


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## terry j (Jul 31, 2006)

thanks Brian

in a case like that I spose it's try it both ways and see what you like. For my simple experiment, I have the screens quite close to the speakers, and like what i hear. I'll have to put a 'do not enter' on the door and try them closer to the walls as in the usual situation, and compare the two.

As I said, because of the size of the room I'd assumed I didn't need it, and having the reflected sound outside of the critical period (I assume it is) I also thought that the delayed sound would contribute to ambience, which is good in my book.

The funny thing is, I did notice an increase in clarity and imaging tightness, but without any loss in ambience, so hey good all round.


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## Prof. (Oct 20, 2006)

Terry, If your first reflection point is on the door, can't you make up a panel and fix it to the door, leaving enough space at the sides of the panel to be able to open and close the door?


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