[youngho]

This is probably a dumb question, but why not simply mount Real Traps or other fiberglass-based products along all room boundaries at ear level for a home theater, at least as much as possible? Wouldn't this address all first reflections for all channels, assuming that they're mounted at ear level? Why bother with mirrors and equations? Just turn the RealTrap sideways and buy a few more. Add a rug on the carpet, possibly a fiberglass "cloud" on the ceiling. It seems as though this would still maintain a significant amount of reflectivity in the room from the boundaries above and below the RealTraps. What am I missing?

Young-Ho

[EProvenzano]

I asked the same question in the 'Slap echo' thread.
Still haven't had a reply to my question. My logic follows yours.

EP

[bpape]

If all reflections travelled purely in paths parallel to the floor this would work to a point.  Unfortunately, they don't.  Reflections move in many directions and at different heights and off multiple boundaries.

Second, you don't necessarily WANT to hit all of the reflections.  The ones that are of concern are those that reach you within 20-25ms of the direct sound reaching you.  

Third, if you did it the way you're describing, you would still have slap at the top and bottom of the room, and potentially could overabsorb at some frequencies while ignoring others.

Fourth, related to the previous point, how much you need, what your target decay times should be, where absorbtion should go, etc. is also related to how you'll use the room (2 channel, multi-channel, studio mixing, live room, etc.).

Lastly, let's look at the front wall.  In a multi-channel environment, the only thing you want coming from the front is direct sound from the fronts - not reflected sound from the surrounds that would mess up the imaging.  So, you cover the whole front wall.  In the rear however, you want a bit more spaciousness and diffuse soundfield where some of the sound from the front is allowed to reflect back at you as well as allowing the surrounds to generate a good enveloping effect.

In a 2 channel room, much of the above applies.  However, in this case, you do not have channels dedicated to creating the surround field.  It all has to come from the front 2.  In that case, you use the room to your advantage in creating the 3 dimensionality of the space.

[Glenn K]

This is probably a dumb question, but why not simply mount Real Traps or other fiberglass-based products along all room boundaries at ear level for a home theater, at least as much as possible? Wouldn't this address all first reflections for all channels, assuming that they're mounted at ear level? Why bother with mirrors and equations? Just turn the RealTrap sideways and buy a few more. Add a rug on the carpet, possibly a fiberglass "cloud" on the ceiling. It seems as though this would still maintain a sig ...

sure you could do that and I am sure Ethan would be more then happy to sell you 17 or more traps, but you really want to focus on corners of the room where bass builds up... Then go back and place panels on the first reflection points.. There was a case study done at AV Science of EQ vs Traps and Ethan put 17 traps in the room.. He felt as though this would pretty much kick the crap out of the EQ, but because he did not straddle corners the results where not as good as hoping.. IMO, they would have gotten better results with 8 traps in corners and additional panels on first reflections..
BTW, I really take my hat off to Ethan for taken the time to do the test. We all learned a lot from it..  You should all go check it out if you have the time..

Glenn

[youngho]

Thanks for the replies! I'm not trying to argue or anything, just clarify my thinking (or lack thereof) behind my original post.

I figured that for a multichannel monopole system, say only 5.1, treating first reflection points could potentially mean 6 or more MiniTraps hanging on the wall (the L and R each may have a first reflection point on each sidewall and the back wall, meaning six traps there, which I'll assume might also coincidentally treat the center channel's reflections, and we haven't even gotten to treating the rear channel's first reflection points or addressed the front wall). Since each MiniTrap is already 4 feet tall, you could cover more "ground" by turning it sideways.

Brian suggests treating the entire front wall (at ear level, I assume). Add 6 or more traps for the side and back walls. At this point, I figured you might as well make it a continuous zone. Add the rug or carpeting, possibly the fiberglass cloud mentioned, definitely some bass trapping separately. Since most rooms are at least 8 feet tall, you've only covered about 25% of the vertical surface in the room, so it seemed like there would be a decent amount of reflections left. One could mount the surrounds on the walls above ear level, particularly if using bipoles. My recollection was that Ethan himself uses a TON of traps in his room (I don't remember how many, but I thought it was more than 20), suggesting that this might work okay. I forgot about measuring decay times.

Anyway, guess it sounds like a bad idea. Thanks again,

Young-Ho

P.s. I followed that immensely long thread on AVS, but for some reason, I thought that the testing had focussed on the mid- and lower bass regions. I'll have to look at it again.

[bpape]

Actually, I meant the WHOLE front wall.

Think of it this way...

Your surrounds are up at maybe 6' high.  They're going to put out waves that will bounce off the front wall and back at you from a point that's NOT at ear level but about halfway between your ear and the speaker height.  You'll also get some that go to the other side wall, then to the front, then to the first side, then to you.  Which one do you treat?  By the time you figure out all the points, it's easier to just do the whole front wall so you CAN'T get anything from the front except the direct signal from the front mains.

[Ethan Winer]

Young-Ho,

> only 5.1, treating first reflection points could potentially mean 6 or more MiniTraps hanging on the wall <

Let's see ... I have two HF MiniTraps on the ceiling, one MicroTrap on each side for the front reflections, and one HF MiniTrap on each side behind me for the rear reflections. Yep, that's six of them!

> My recollection was that Ethan himself uses a TON of traps in his room <

Not quite a ton, but I do have 38 of them. They are all carefully placed, and the RT60 is extremely uniform at all frequencies.

--Ethan

[Glenn K]

>Not quite a ton, but I do have 38 of them. They are all carefully placed, and the RT60 is extremely uniform at all frequencies. <


Not to give you any marketing ideas   but maybe you should have the wife do a review for ou..  
38 TRAP????? My god you must own the company..