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post #1891 of 10427 Old 01-19-2007, 09:55 AM
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Quote:
Originally Posted by causeofhim View Post

I was using info from this thread. It seems that the consensus on here that 1" is the "sweet spot".
If people think that 2" would be better in my situation, I will use it.

I'm not sure where the 1" comes from. The idea behind broadband absorption is that you want to absorb all frequencies equally, so you're not changing the tonal response of your room.

Now some rooms need a little tuning. If you have lots of hard reflective surfaces, you may want to focus on the high frequencies with 1". If you have a smaller room that has bass problems, but you don't want to make it too dead (can sound like listening to your room with a headcold, just very unnatural), you can used faced (FRK) fiberglass (better low end absorption, much less high end absorption).

But, a safe starter solution is almost always attacking 1st reflection points with broadband. This will help with dialogue clarity in movies and definition in music. In my experience, probably the biggest improvement you can make in a system for $150.

Then, look at low end control. This will balance your sound so it doesn't seem boomy or too thin. Try the BFD for an inexpensive half-solution, and add some corner traps as time, money, space, and significant others will allow.

From there, you can hit up the rest of the room with more absorption if it's too live, or diffusion if it's starting to sound dead (diffusion should also help to expand the listening sweetspot).

To others out there: Am I off on any of this?

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post #1892 of 10427 Old 01-19-2007, 12:12 PM
 
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My situation is a little tricker I would guess. I am moving into a house with an attached garage. The original owner closed off the garage and made it into a room with a dropped ceiling. I have been in this has before as I know the current owner and I would imagine that the garage has no real insulation as its hot in the summer and cold inthe winter.

I am not planning on doing any real construction to this room. Both the front wall where the screen would be and the right wall have long built in closets that go from one end of the wall to the other. They have metal folding doors.

I am going to replace the dropped ceiling tiles with black accoustic tiles.

I guess my question is, what should I do about the screen wall and the right wall. As my wife wont let me close off the closets space, at the very least I will need to change out the metal doors to wood.

Is there anything I can do to treat these wood closet doors which basically will wind up being the side and screen wall and secondly, as the rear and left walls are completely walls and cannot be touched, is there anything I can do for them

Although its not part of the topic, but woild placing insulation of over the top of the dropped ceiling and possibly in the closets help with the heat and cold.
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post #1893 of 10427 Old 01-24-2007, 11:15 AM
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Have read most of this thread. Lots of opinions! Am ready to apply some treatments using panels of 1" Knauf duct board, which I was able to find locally without trouble as opposed to 703, which has eluded me. Acoustic properties are close.

My question has to do with how to treat rear wall ompared to the front wall. My screen is painted directly to the drywall, so getting an absorbing material behind it is not going to be possible, unless you count the R11 behind the drywall already. I will make panels to surround the screen as best I can. The images below are what the room looks like, although there have been some minor changes.

The general consensus I have been able to glean is that the panels for first refelction points along the side walls need to extend from floor to ear height, more or less.

What about the rear wall? Should these extend from floor to ceiling, or continue with the ear height concept? Should I make the panels on the rear wall thicker than the front wall?

I am sure that if I build a dozen or do panels for the room, I will improve the sound quality over that of my drywall box regardless, but it would be nice to have made the most out of my effort.

I am planning using the mirror method to help me locate the panels for the side walls and maybe for the ceiling as well, although I will have to see how this all looks. The dimensions of the room are approx. 23' front to back 12' wide along the screen wall, and 15' wide at the seating area. Preliminarily, my plans are as follows. I hope that someone will leap in and either applaud me, rescue me from ruin, or offer a couple of tweaks:



I will flank the screen with panels along the left and beneath. I have a new PJ, and have grown the screen size to the right almost to the wall to the right and up, almost to the ceiling, so ther is no option to the right or above.

Along the left wall where the left channel and sub sit there will be a panel coming out of corner about 3' towards the sconce shining down as well as a matching one in the opposite corner. The speakers have been change to Klipsch Heresys for the front line, sitting on the floor. I will have panels behind these. Going down the right wall will be floor to ear height panels at probably two reflection points.



Looking back to the rear, you can't see because I compressed the images too much, but there are two rear surround in-walls that will impact how I treat this surface. A bass trap straddling the corner from floor to ceiling is planned but may be no more than a double layer of the 1" board (foil backing removed). It is the rest of the rear wall that I am unsure of. How tall should they be? Ceiling height at the rear of the room is barely 7'. I am thinking about a panel on the door. What about the rest of that wall? With the equipment rack where it is, trapping across the rear corner is not going to work. All the cabling emerges from a good sized opening behind the equipment. What would anyone suggest for this corner? Coming down the wall from the equipment rack corner I will place probably two panels at the reflection points. This has been complicated by the addition of a relatively large free-standing open shelf which replaces the black shelf shown in the pictures. I will have to pull it out from the wall to determine the locations for these panels. If you want to see all the pictures of my completed room, take a look here:http://www.chriswhitworth.com/complete.htm

I am looking forward to this project to tighten up my sound. I can tell it just isn't what it should be. Will be very grateful to anyone offering some advice.

Christer Whitworth

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post #1894 of 10427 Old 01-24-2007, 12:08 PM
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That is a nice little theater! Those seats look pretty comfy for having a slim profile.
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post #1895 of 10427 Old 01-24-2007, 12:47 PM
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Very nice room.

A few questions...

So the screen isn't centered on the wall, but up against the right wall (you say the screen has grown to the right wall)? Meaning the right speaker is basically up against the right wall? That's how it looks in the pictures, anyway. And now the speaker is in front of the screen?

Ideally the screen would be centered and the speakers would be much further away from the side walls, symmetrically spaced from the front and side walls. That would be ideal, even if it meant reducing the size of the screen slightly.

Can you center the seating and screen in the room? That would be the absolute best for the sound, and allow you to properly place 1st ref point absorbers on the sides.

But the speakers should also be moved forward more, away from the front wall. You can place bass panels in the front corners, either straddling the corner, or cut into triangles and turned into wedges. Do the rear right corner, but don't worry too much about the corner behind the equipment rack. If you treat the other three corners, you're already doing much better than most people, even here on AVS.
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post #1896 of 10427 Old 01-24-2007, 12:53 PM
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What are the areas that you feel your sound is lacking? Is dialogue unintelligible? Boomy or flabby bass? Instrument imaging lacking?

My opinion, if this were my room:

Front wall: the off center screen is throwing me. You're going to wind up w/ asymetrical sound regardless w/ center channel off center, more so if you treat one side of the wall. With no room for a bass trap in the right corner, I'd leave the front as is, with the possible exception of treating the 1st reflection points behind the speakers themselves. If you can bring the fronts forward a bit, and have enough room, then try a bass trap in the right corner (superchunk style)

Side Wall: 1st reflection points for sure (all the speakers, don't miss center, side, or back), sandwich 2 layers to give you 2". Focus on ear level, don't need to go to the floor or the ceiling.

Rear wall: Put 2 inch on as much as possible, focusing on the first reflection points. Bass trap in corner? Why not. Once again, Superchunk seems to be the easiest and most effective (fiber cut into triangles and stacked in corner to make a solid fiberglass tri-post)

Ceiling: 1st reflection point between your center channel and your seating positions.

Speaking of bass traps, if your material is anything like 703, you'll want 4 inches (had this pointed out to me when I asked a similar question). 2 inches won't do much of anything (trust me, I've tried and had Room EQ wizard confim that I was wasting my fibergass)

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post #1897 of 10427 Old 01-24-2007, 12:54 PM
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Quote:
Originally Posted by causeofhim View Post

That is a nice little theater! Those seats look pretty comfy for having a slim profile.


If those are the poyang (sp?) chair, they are amazing comfy (and should be for over $100 for wood and a pad). They have a new chair that looks like the poyang, only cheaper, stay away!

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post #1898 of 10427 Old 01-24-2007, 01:06 PM
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That was my first reaction too, but he says the screen is painted on. Re paint, I guess, is an option.

Quote:
Originally Posted by cyberbri View Post

Very nice room.

A few questions...

So the screen isn't centered on the wall, but up against the right wall (you say the screen has grown to the right wall)? Meaning the right speaker is basically up against the right wall? That's how it looks in the pictures, anyway. And now the speaker is in front of the screen?

Ideally the screen would be centered and the speakers would be much further away from the side walls, symmetrically spaced from the front and side walls. That would be ideal, even if it meant reducing the size of the screen slightly.

Can you center the seating and screen in the room? That would be the absolute best for the sound, and allow you to properly place 1st ref point absorbers on the sides.

But the speakers should also be moved forward more, away from the front wall. You can place bass panels in the front corners, either straddling the corner, or cut into triangles and turned into wedges. Do the rear right corner, but don't worry too much about the corner behind the equipment rack. If you treat the other three corners, you're already doing much better than most people, even here on AVS.


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post #1899 of 10427 Old 01-24-2007, 02:48 PM
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Chris,
Other than the tweaks you know you need, you might want to move the left speaker the same distance from the center of the screen as the right speaker. An SPL monitor wouldn't hurt.

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post #1900 of 10427 Old 01-24-2007, 03:17 PM
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Talk about speedy replies! Don't you guys work?

In looking at my photos again, I can see your confusion. What you don't see is that I have a length of soffit running the full length of the left wall which houses HVAC vent and gas line. It starts out about 30" wide at the screen wall and grows to nearly 6' by the time it reaches the rear of the room as you can see here. You can also see how the riser has nowhere to go as far as re-positioning:



This gives you a better idea of the design issues I faced. In my previous shots, you can't see the entrance to the room. The white door in the shot above is to access HVAC and water heaters, not the entrance to the room. The shot below shows how the soffit and entrance (door with poster on it) affected the look of the room.



The screen is centered on the section of wall which has full ceiling height (8'). You can see a vertical seam that drops straight down from the soffit just to the right of the two electrical boxes in the corner in the picutre above. This section to the right is what the screen is centered on. The seating is centered in front of the screen. The speakers are in the corners. When you are in the room, if you really pay attention, you can tell the screen if offset to the right relative to the speakers , but not to the wall/ceiling interface. If I had centered the screen on the wall, not the ceiling, the left section of the screen would be under the soffit. If I did that, apart from making the room look out of balance, it would also have meant having to extend the riser to the left (looking forward) to center the seating, blocking access to my furnaces and water heaters. I really did give this a lot of thought. Regarding the perceived problem of the speakers being offset to the screen, I think the visual imbalance of having one speaker in the corner and the other two feet in from the corner is too high a price to pay for the very nominal improvement in imaging I would experience, but I will give it a try! The center channel is centered under the screen which is centered relative to the seating. Since in a movie, all/most dialog comes out of the center, I think my problems in this area are not as great as you may think. The only thing off center is the left speaker.

Funny, when I got my Heresys back in the 70's Klipsch themselves counciled putting all their speakers in corners. You may have heard of Klipschorns? I have always had them in the corner of every room they have ever been in. Nothing else ever ocurred to me. I suppose I could move them forward and inward, slightly. With grandkids LEAPING on to the Lovesac (basically a giant beanbag you can see in the earlier post), the idea of having the speakers out in the room is not one that thrills me. As you get older, the idea of life being a series of compromises comes home, over and over!

The screen itself is a product of Mississippi Man's Mudd formula that was popular when I built this three years ago. A combination of silver metallic udercoat and top coats consisting of a mix of clear base, ultra pure white and pearl opalesence. At Home Depot, they thought I was crazy when I had them mix it up for me. I have since re-painted it so that it is still in the same space, but slightly wider, and slightly taller. It was 106", now up to 118" diagonal. The black frame is now butting up against the right wall, and the top molding is pretty close to the ceiling, so there isn't any way to get anything meaningful on either side. Bottom and left are what's available.

The chairs are indeed from IKEA. I paid 69.00 for the Poang chairs and 40.00 for the ottomans. You could spend far more for something far less comfortable, so I consider them a good buy. Also, their trim lines keeps the room 'spare' if you will. They are very comfy. I went to a friend's house who had his HT done professionally and watched a movie sitting in his Berklines. I didn't find them any more comfortable, and they had no head rest support.

Eugovector,

I really appreciate your input on the treatments. I doubt that I would have doubled up all the panels. Maybe I can get a discount now that I will have to buy twice as much or perhaps I will get the 2" stuff to start with.

Chris Whitworth
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post #1901 of 10427 Old 01-24-2007, 03:24 PM
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I see. Didn't realize the room was wider in the back, or that there was a riser. But you said the screen now goes to the edge of the wall on the right.

No matter what, the screen and speakers should still ideally be symmetrical on the wall they reside, even with the soffit in the upper left corner. The screen area needs to be moved to the left, in the center of the wall (regardless of the soffit - move the screen down if needed).

Try putting on some 2-channel music, and play around with the location of the speakers. Even if they are close to the front wall, changing their proximity to the side walls will drastically change their sound. The point of side-wall absorption is to absorb the sound at the first reflection point. But with the speakers right next to the side walls, you are making that much worse than it should be. And you don't want to put a panel to the side of a speaker inches away from it.
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post #1902 of 10427 Old 01-24-2007, 04:18 PM
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cyberbri,

Your suggestion means my seating will not be centered, or best case, the floor seats are centered, but the riser seats are off-set to the right.

In your gallery you have a picture of your daughter(?) kneeling on a bench/shelf. Next to her is an absorber shown wrapped in lilac. Is that mounted there full time? If so, I think we are coming from very different spaces in regards to how the balance of aesthetics vs sound performance needs to be addressed.

Don't get me wrong, and I am not criticizing, but I cannot imagine moving my screen down and to the left. The sight lines for the rear viewers, offest to the right in this new scenario would be like being in an old theater; they would have to look around the heads of the people in front of them to see the bottom of the screen. With my Heresys in place before I moved the screen up, the center was just flush with the bottom of frame. Moving it down at all would require either laying them on their sides, or making the screen narrow enough that the L&R would fit on either side and perhaps a different center channel. Neither of those sound good to me, no pun intended.

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post #1903 of 10427 Old 01-24-2007, 04:26 PM
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I just said "ideally." In the end, you have to do what works for you. Having speakers right next to the wall, and/or place asymmetrically, is very bad for the sound. If you only watch movies and don't listen to music in the room, that's probably not much of a concern for you. If you can find a way to treat the side walls and maybe the ceiling, that should help a lot, especially with the speakers so close to the side walls.

And no, the panels are not mounted or permanent. But they are there full-time. There's a window there, which is presumably even worse for reflections than a regular wall. We need the bench/shelf there, so putting the panel sideways on top of it worked the best. On the other side, the matching panel is sitting on the floor, propped against the wall.

So the balance of aesthetics vs sound for my living room is 45-55. If it was a dedicated room not used for anything but TV/movies/music/games, it would be 10-90 or 20-80, aesthetics vs sound. I would make sure everything (screen, speakers, seating) was centered and symmetrical and set everything up for the best sound and picture. Plus a lot more room treatments. I have done that as much as I can in my living room, to the extent that we have to have other furniture in the room because it functions as a living room as well, with a fireplace on the left and a large bay window on the right (and a desk w/computer in rear of room under R surround speaker). But I have kids (8yo and 2yo) and I still have my speakers out and not against the walls. They know not to touch or play around with them, and this is in our living room.
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post #1904 of 10427 Old 01-24-2007, 06:52 PM
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When I get everything put together, I will post new shots and PM you and eugovector.

Thanks again for your input.

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post #1905 of 10427 Old 01-25-2007, 06:50 AM
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[quote=christer W.]Talk about speedy replies! Don't you guys work? /QUOTE]

Nope, I retired in 96'. Piddling around with construction projects, art and the like keeps me busy.

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post #1906 of 10427 Old 01-25-2007, 10:37 AM
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Christer,

I think you've been given some very good advice and I agree with it for the most part. Normally with 3 seats in the front you want to keep the main center position just a bit (6-12") off dead-center but with only 2 in the front it'd be perfect to center the seats exactly. IMO the solution for you is to make the screen smaller. A large screen is not necessarily better. What's needed (IMO) is a screen that's large enough to see all of the detail presented in the image. Too close and/or large and you see imperfections that you're better off never seeing, and too small will have you missing details. I suspect even an 70-90" screen would be plenty but you could test this yourself by just projecting a smaller image for a bit and seeing how the PQ looks. Some of the benefits of a smaller screen is that it'll be brighter and will also look like a more clear, detailed image from any given distance compared to a larger screen.

What I'd like to stress is for you to try things out for yourself. For Sound Quality, get some good music that you know inside and out, and then listen to it with your speakers where they are, vs pulling them 2 feet out from the rear and 2 feet in from the side walls. Then you can hear the difference that pulling them off the side walls makes, and judge the tradeoff for yourself. The consensus is that even toed in towards the listenner, speakers should be at least 18" away from the sides and from the rear also. Being too close to the sides will affect the voices and highs, while being to close to the rear will affect bass and lower frequencies.
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post #1907 of 10427 Old 01-25-2007, 10:04 PM
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Felgar,

Thanks for your reasoned response. I have been grateful of the advice given and will use it to the best advantage for my room.

Regarding the screen, what you may have missed is that I have made by screen BIGGER after having lived with the one you see in the pictures for near on 3 years, so this is not an impulsive newbie move. My earlier PJ was the Panasonic L200u that had/has 1/4 HD panels. On my 106" diagonal screen at 12", if I really looked hard, I could see a little SDE. So what? Still looked great. Still would have looked great if I had sprung for a new bulb. But, for only a little more, a 720p seemed like the way to go.

I went over to a fellow AVS'er who has a Panasonic L500 with 720p panels and the difference was very noticeable, this in spite of his projecting onto a 122" diagonal screenl. I was amazed at how those extra inches seemed to make such an impact. Had to go home and plan it all out. While I was at it, the idea of doing some sound treatments came to mind, which is how we all got here.

I am looking forward to making the panels. I am figuring about a dozen in various shapes, thicknesses,, and types. It should be fun and for not very much money.

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post #1908 of 10427 Old 01-26-2007, 07:49 AM
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I'm with you on some level, as viewing distance is, IMO, the most overlooked aspect in our bigger is better world. However, Christer is right on THX spec w/ his screen/seating distance. As long as he's watching high-res material on good equipment, it'll look fine. In the end though, unless you have a acoustically transparent screen and have positioned speakers behind it, you'll likely be sacrificing acoustics for image size in THX spec.

The rule of thumb that I use is seating distance should equal 2 times the 16:9 screen diagonal. Now, THX specs will tell you that this is way to small. Check out this calculator here:

THX Seating Distance Calculator

I currently sit 7.5 feet away from my 51" screen, a little closer than 2x the diagonal. THX tells me that I should either be sitting less than 6 feet away, or that I should have a 67" screen. But I won't bemoving closer, or buying a bigger TV, and this is why.

Let me start by saying that I'm throwing out approximate numbers here, just working off the back of a piece of scrap paper. I'm sure my math is a little off with rounding and what not, but close enough for our purposes.

Speaker placement: Dolby recommends front speaker placement 22-30 degrees off center. THX suggests similar placement. Many opinions that I've read say that for movies, you should shoot for the 22 degrees, for stereo music, the 30. Break out our 11th grade trig books and we see that the distance between speakers should be between 0.8 (for movies) and 1.15 (for music) of the seating distance.

My screen is about 45 inches wide, with the bezel my TV is 48. On my fronts (JBL S38II), the tweeters are atleast 14 inches from the side of the speaker. That means that if I butt the speakers right against the edge of my screen, the tweeters are 73" apart. Realistically, leaving an inch or two in between, we're at 75-77". At my THX recommended seating distance of 5.7 feet (68.4 inches), the tweeters of the speakers should be between 55 (movies) and 79 inches (music) apart. That doesn't leave a lot of wiggle room, and I found that in my room, the 79" was even too wide for music. I also needed a wider sweetspot, as I'd be watching most movies as at a pair, not a single.

So what did I do? Buy smaller speakers? Nah, I compromised. Good sound was more important to me than the biggest picture image (especially considering that I won't be watching HD exclusively, but also a lot of upscaled and processed 480P). I spent a lot of time listening, and moving, and listening, and measuring, and listening, and moving, and listening some more.

So, long story short, I postioned my speakers correctly and use a rule of thumb that you should sit slightly less than 2x the screen diagonal away from your display. No complaints yet.

Christer, with your current screen size, you'll probably be sacrificing acoustics for screen size. If that works for you, don't worry about it. Do what you can with your current setup, and sit back, and enjoy. However, if you want to improve your sound, positioning everything correctly is the start.


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IMO the solution for you is to make the screen smaller. A large screen is not necessarily better.


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post #1909 of 10427 Old 01-26-2007, 10:14 AM
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I plan on moving things around a little to see what sounds best. It should be interesting. Documenting all the changes will be the hardest part

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post #1910 of 10427 Old 01-26-2007, 10:18 PM
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Getting ready to enlist some help from a family member to sit in the chairs while I wander around the room with a mirror to figure out where to place my yet-to-be-built panels/traps. Was thinking about the idea of putting an incandescent light where the speakers are to help you get your reflection points, as suggested elsewhere on this thread.

What exactly do you get out of seeing the bulb that you don't get out of seeing the speakers themselves in the mirror? I am guessing you are trying to make it easier to see??? Why not just have your assistant aim a flashlight at the speaker itself, if necessary? Place the center of the speaker in the middle of the mirror, attach piece of tape/Postit note on wall behind mirror to mark center of panel....

Is there something I am missing?

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post #1911 of 10427 Old 01-27-2007, 06:46 AM
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Quote:
Originally Posted by christer W. View Post

Getting ready to enlist some help from a family member to sit in the chairs while I wander around the room with a mirror to figure out where to place my yet-to-be-built panels/traps. Was thinking about the idea of putting an incandescent light where the speakers are to help you get your reflection points, as suggested elsewhere on this thread.

What exactly do you get out of seeing the bulb that you don't get out of seeing the speakers themselves in the mirror? I am guessing you are trying to make it easier to see??? Why not just have your assistant aim a flashlight at the speaker itself, if necessary? Place the center of the speaker in the middle of the mirror, attach piece of tape/Postit note on wall behind mirror to mark center of panel....

Is there something I am missing?

Hi Chris - The main thing is to see the speaker in the mirror at your seated position. Whether the speaker is lit up, there's a light bulb in place of it, or there's a small statue of Elvis where the speaker will be, should pose no difference in the outcome. There could be some unexpected trauma for the seated person suddenly seeing Elvis when he really should be working at the 7-11 across town, but that's not an acoustic issue and outside the scope of this discussion.....
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post #1912 of 10427 Old 01-27-2007, 07:02 AM
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Going solo? Use a laser with the mirror method to find first reflection point.

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post #1913 of 10427 Old 01-27-2007, 09:35 AM
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Ahh,

The laser. Hmm....something to use my pointer for other driving my cat crazy making her chase the red dot on the floor.

Not sure how the laser helps with going solo. Can you elaborate on this technique? Doesn't the mirror have to move back and forth until the person in the chair sees the speaker? I suppose if you had a large enough mirror, you eye-ball where you think it should appear, place the mirror there (hoping you have the correct vertical angle so your beam doesn't go right over or under the target) and then use the laser to pinpoint the location of the center of the panel....

Chris Whitworth
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post #1914 of 10427 Old 01-27-2007, 10:18 AM
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christer W.

I'd use the laser for direct pointing your speakers, and not for the mirror trick.

The problem with the light bulb, is that you have to move your speaker to put it there. And it would only work if you walls were painted gloss so the light would reflect. Or for example if you have a plant in the way, it's not going to work.

You can calculate mathematically where the wall reflection point is (if your walls aren't square mathematically is a little trickier, and if they're curved use a mirror), or if you have a 3"x3" mirror and some post it notes, then you can sit and someone else can move the mirror along the wall until you can see the speaker in the mirror and then they can put a post it note there labeling the name of the speaker you can see. So each left/right wall should have three post it notes (left speaker, right speaker, center speaker) for each seating position. Then where you want first reflection point absorbers is a minimum 1' outside of all the post it notes.

The phrase you may recall from grade school is "angle of reflection equals angle of incidence". Sound is bouncing off that wall.

Later, if you do measurements with RTA software, the difference in time/distance (because sound travels at 1130ft/s, 1 foot is approximately 1ms) between the direct sound path length (e.g. 3'), and one of The Mirror Trick reflection sound path lengths (e.g. 13'), is the corresponding spike that appears in your impulse graph (e.g. 13' - 3' = 10', aka a spike that appears 10ms after the direct sound).
In this graph there's a spike at 29.9ms (direct sound), and another one at 31.1ms (reflection) and another one at 39.5ms (reflection).
31.1 - 29.9 = 1.2 feet. (approximately)
39.5 - 29.9 = 9.6 feet.
On a frequency response graph it appears as comb filter dips.

See the Direct vs Reflected macromedia flash at
http://www.acoustics.salford.ac.uk/a.../duck/duck.htm

http://www.audioholics.com/news/uploads/slide02.gif
http://www.audioholics.com/techtips/...reatments3.php

http://www.msr-inc.com/sp_installation.php

http://www.etfacoustic.com/mirrortrick.html

http://www.bryston.ca/newsletters/43_files/vol4is3.html

http://www.asc-hifi.com/acoustic_basics.htm

http://www.auralex.com/auralex_acous...mirrortest.asp

http://www.stjohngroup.com/downloads...EL_install.pdf (see page 2)

http://forum.studiotips.com/viewtopic.php?p=14288#14288
look at "1st Ceiling Reflections.pdf", "1st Side Reflections.pdf"

http://www.audioholics.com/techtips/...ics101THX2.php

http://psbg.emusician.com/ar/emusic_...ered_studio_2/

http://www.realtraps.com/art_room-setup1.gif

http://www.realtraps.com/art_room-setup3.gif

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post #1915 of 10427 Old 01-27-2007, 11:05 AM
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BasementBob,

Thanks for the links. Most interesting. I have now come upon something that has me even more slightly confused than before. The MSR site you suppled to a link to has a very complete installation guide to their products. What has me confused is this image and subsequent text:



My confusion stems from the advice given throughout this thread that the treatment of side walls should extend up to ear level, or a figure of 44"- 48" is seen often. The diagram is hard to make out, but their instructions are not:

"Fasten a V-Bar so the bottom of this bar is 64 inches from the floor onto the wall using either drywall screws into studs, using wallboard inserts and screws, or other appropriate fasteners."

You then hang the panel with its already attached V bar mate. In the diagram, you can see that their panels extend a couple of inches higher than the V bar, and they are off the floor about 18-24" - hard to tell exactly.

So which is it? Obviously, I can experiment, but am loath to put holes in my walls that may later need to be patched and painted

Chris Whitworth
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post #1916 of 10427 Old 01-27-2007, 11:35 AM
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christer W:

Both are valid.

There are a bunch of different styles of applying acoustical treatment.

One is Dennis Erskine Style (i.e. copying the romours, not an actual DE designed theater which is almost certainly better).
Another is putting a bunch of 2'x4' panels, roughtly evenly spaced throughout the room.
There are others.

The only example of a bunch of 2'x4' panels, in a home theatre, that I have handy are these:
http://www.realtraps.com/cust_ht1.jpg
http://www.realtraps.com/cust_ht2.jpg
http://www.realtraps.com/cust_ht3.jpg
http://www.realtraps.com/cust_ht4.jpg
http://www.realtraps.com/cust_ht5.jpg
http://www.realtraps.com/cust_ht6.jpg

In a DE Style theatre, the rule is
a) front wall, floor to ceiling, wall to wall, 1" of linacoustic
b) side and rear walls, floor to half way up the wall, 1" of linacoustic. Assumption that the mirror point of all speaker drivers to all listener's ears is lower than the half way up the wall point.
c) side and rear walls, half way up the wall to ceiling, polyester batting
d) lots of leather covered couches (bass absorption)
e) rear riser and columns with bass traps (helmholtz, membrane)
f) deeper absorption (e.g. 6" 703 with 4" air gap behind) on some side/rear wall surfaces
g) carpet with thick underlay
h) soundproof rigid walls, preferably decoupled with something such as RSIC, and green glue to damp the wall resonance.

So, the absorption is used to do two things:
1) change the RT60 of the room so it's a little on the dead side
2) handle first reflections and SBIR issues.

Where the absorption is not, the idea is to let the sound reverb (bounce) around the room to increase ambiance and spaceousness, and reduce knowledge of directivity. Notice how the front 3 speakers have absorption on all sides, but the left/right/rear surround speakers have reflective surfaces near them (walls without absorption). Imagine the sound bouncing around above your head for many reflections.

What it sounds like where your ears are not, who cares.

An obvious side effect of treating the entire room's bottom half, is that it doesn't matter where the seats are placed, or where the listener sits, it's guranteed that first reflections are handled. No mirror trick is required.

If you're putting 2'x4' panels up, the mirror trick is required. If it's possible to spread them out with space between each, that's better (a diffusive and a LF absorptive effect) -- but for the main left/right reflection point in a home theatre with 3 or 4 front seats, and a second row, this is usually impossible.

So, in summary, you want to absorb the actual reflection. But you also want to have sound bounce around the room a bit. Both the designs/recommendations you spotted do that in different ways.

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post #1917 of 10427 Old 01-27-2007, 11:48 AM
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BasmentBob,

Thanks very much for your concise distillation of the entire 64 page thread. Had I known to ask, I could have saved myself hours of reading.

I look forward to the the mirror exercise.

Chris Whitworth
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post #1918 of 10427 Old 01-27-2007, 02:06 PM
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Chris,

> I look forward to the the mirror exercise <<br />
I don't understand why Bob linked only to the pictures on the RealTraps site but not the accompanying articles, because that would have been much more useful to you. While you're at our site, click Acoustics Info at the top of any page, then Acoustics Articles. There also are videos that show how to set up a room properly for speaker and bass trap placements etc.

--Ethan

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Ethan's Audio Expert book

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post #1919 of 10427 Old 01-27-2007, 02:13 PM
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Quote:
Originally Posted by BasementBob View Post

christer W:

Another is putting a bunch of 2'x4' panels, roughtly evenly spaced throughout the room.
There are others.

The only example of a bunch of 2'x4' panels, in a home theatre, that I have handy are these:
http://www.realtraps.com/cust_ht1.jpg
http://www.realtraps.com/cust_ht2.jpg
http://www.realtraps.com/cust_ht3.jpg
http://www.realtraps.com/cust_ht4.jpg
http://www.realtraps.com/cust_ht5.jpg
http://www.realtraps.com/cust_ht6.jpg


If I'm not mistaken, that's Ethan's house. May not be your cup of tea, but probably sounds great.

Listen to the Real HT Info Podcast at http://realht.info, including video reviews at my YouTube Channel: http://www.youtube.com/user/realhtinfo/videos
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post #1920 of 10427 Old 01-28-2007, 12:27 PM
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I have started a new thread on needing help with Acoustical Treatment with room dimentions and graphs. I did not where would be the best place to put it so Here is the link over to my thread in the audio theory section.
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