Why doesn't my room sound better than it does? - AVS Forum
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post #1 of 65 Old 04-10-2013, 12:21 PM - Thread Starter
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Hoping someone has some ideas on something that has been bothering me. Four months ago I moved to a new house and set up my speakers based on what should be ideal positioning but have been disappointed that in some ways the sound is worse than what I had at my previous house which had far from ideal speaker/listening positions. What bugs me specifically is that when listening to 2 ch music in my old room, I could pinpoint exactly where the singer's voice was coming from – it was very defined and I could picture exactly where the singer’s mouth was. In the new room, the singer's voice is not as defined and sounds like it’s coming from a larger area. It’s easier to me explain using a visual analogy – the previous sound was like a golf ball and the new sound is like a basketball. I think this is the case with instruments too but it’s most obvious/bothersome to me with the singer’s voice.

I’ve attached some pictures of the rooms.
Old room (don’t recall dimensions; speakers probably 1.5 ft off wall; LP up against back wall):


New room (24x19x8; speakers 3.5 ft from front wall and 5 ft from side walls; LP about 10ft from front wall):



The only culprit I can think of is that the old projector screen was solid laminate whereas the new one is a thin material and I have placed Owens Corning insulation panels between it and the window.

I’ve made some new acoustic panels with more OC panels and plan to hang them along the side walls this week but don’t anticipate them making a huge difference in this respect.

Any thoughts/suggestions appreciated.
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post #2 of 65 Old 04-10-2013, 01:11 PM
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Your new room is vastly better than your old room. So part of the problem is you're just not yet used to the improved sound quality. However, you'll benefit greatly from acoustic treatment. In particular, your old room was open on the sides, where your new room gives strong reflections from the side walls. So in that one regard your old room was better. The good news is this is easy to fix. This short article is mainly about home recording, but all the same principles apply to hi-fi and home theater too:

Acoustic Basics

Once you apply some basic acoustic treatments, your new room will be far better than your old room could ever have been.

--Ethan

RealTraps - The acoustic treatment experts
Ethan's Audio Expert book

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post #3 of 65 Old 04-10-2013, 01:44 PM - Thread Starter
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Originally Posted by Ethan Winer View Post


Once you apply some basic acoustic treatments, your new room will be far better than your old room could ever have been.

--Ethan

Thanks Ethan, I've already spent a good amount of time on your site in the past.

I have already built 4 panels which are currently resting on the floor against the side walls (I"ll be hanging them this week); so far I can't say I notice much difference with them but hope getting them a few ft higher will help. I have 2 more sheets of insulation to build panels with - would you suggest the greatest benefit is treating the ceiling or next to the screen? My old room had a 10 ft ceiling and the new one is only 8 ft so I wonder if that's a factor. The brown panels in the windows are OC panels and they are basically right behind the mains but I could add another panel next to each of those.

Do you not think the window being entirely covered in OC panels is having adverse acoustic effects?

You might be right about needing to get used to the room but I don't think this lack of vocal definition will grow on me. In some ways it does sound better than my old room but I had very high hopes when moving here since I was able to set everything up based on ideal specifications in terms of speaker and listening positions; maybe my expectations were too high.
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post #4 of 65 Old 04-10-2013, 05:33 PM
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Originally Posted by benunc View Post

Four months ago I moved to a new house and set up my speakers based on what should be ideal positioning...
Not sure what you mean by "ideal positioning" but, if you're open to placement suggestions, here's what I would do. If your room is 19 ft wide, then it will resonate at roughly 30Hz, 60Hz and 90Hz across the width of the room. You can ameliorate peaks & dips at those frequencies (across all seats) by placing your subs 57 inches in from the side walls and placing your left & right speakers 38 inches in from the side walls. You can further smoothen the frequency response by placing the seating at one of the 1/3 or 1/5 divisions of room length: e.g., 14.4 or 16 feet from the front wall.
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In the new room, the singer's voice is not as defined and sounds like it’s coming from a larger area.
Early reflections can have the effect of broadening the soundstage, like moving closer to the screen to get a bigger image. You can tighten the imaging and shrink the soundstage by absorbing early reflections from the side walls and ceiling. A demonstration of this was your old room, which had a higher ceiling and no nearby side walls, lessening the broadening effect of early reflections.
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I’ve made some new acoustic panels with more OC panels and plan to hang them along the side walls this week but don’t anticipate them making a huge difference in this respect.
If the OC703 panels are sufficiently broadband in their absorbtion, then they will give you the effect you're looking for. In order for them to absorb directional frequencies, they should be at least 3-4 inches thick, placed 3-4 inches (air gap) from the walls. Panels that are too thin will only absorb higher frequencies, giving you a dull sound. Finally, consider covering more of your front wall with absorbtion; will keep reflections from your surround speakers from bouncing off the front wall and interfering with the phantom imaging in your front soundstage.

Sanjay
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post #5 of 65 Old 04-10-2013, 08:39 PM
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Originally Posted by sdurani View Post

Not sure what you mean by "ideal positioning" but, if you're open to placement suggestions, here's what I would do. If your room is 19 ft wide, then it will resonate at roughly 30Hz, 60Hz and 90Hz across the width of the room. You can ameliorate peaks & dips at those frequencies (across all seats) by placing your subs 57 inches in from the side walls and placing your left & right speakers 38 inches in from the side walls. You can further smoothen the frequency response by placing the seating at one of the 1/3 or 1/5 divisions of room length: e.g., 14.4 or 16 feet from the front wall.

Hi Sanjay,

I've never seen a response quite so precise before, can you share the reason behind your calculations, and perhaps the formula? I'm intrigued.

Ben, just a thought but have you experimented with toe-in angle? You look to be 40-45 degrees, you may find that in the new and more symmetrical room somewhat less of an angle may improve your soundstage. It's odd I know, but sound can take on pretty big changes by moving your speakers even an inch.

Nice space! Don't spill red wine on that carpet (he said with the wisdom of experience wink.gif ).

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post #6 of 65 Old 04-10-2013, 11:39 PM
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Originally Posted by Nethawk View Post

I've never seen a response quite so precise before, can you share the reason behind your calculations, and perhaps the formula?
Sure, there was some explaining in the REW measuring thread. Start reading from the following post:

http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs/1080#post_22946030
Nethawk likes this.

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post #7 of 65 Old 04-11-2013, 07:12 AM - Thread Starter
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Originally Posted by sdurani View Post

Not sure what you mean by "ideal positioning" but, if you're open to placement suggestions, here's what I would do. If your room is 19 ft wide, then it will resonate at roughly 30Hz, 60Hz and 90Hz across the width of the room. You can ameliorate peaks & dips at those frequencies (across all seats) by placing your subs 57 inches in from the side walls and placing your left & right speakers 38 inches in from the side walls. You can further smoothen the frequency response by placing the seating at one of the 1/3 or 1/5 divisions of room length: e.g., 14.4 or 16 feet from the front wall.

Early reflections can have the effect of broadening the soundstage, like moving closer to the screen to get a bigger image. You can tighten the imaging and shrink the soundstage by absorbing early reflections from the side walls and ceiling. A demonstration of this was your old room, which had a higher ceiling and no nearby side walls, lessening the broadening effect of early reflections.

If the OC703 panels are sufficiently broadband in their absorbtion, then they will give you the effect you're looking for. In order for them to absorb directional frequencies, they should be at least 3-4 inches thick, placed 3-4 inches (air gap) from the walls. Panels that are too thin will only absorb higher frequencies, giving you a dull sound. Finally, consider covering more of your front wall with absorbtion; will keep reflections from your surround speakers from bouncing off the front wall and interfering with the phantom imaging in your front soundstage.

I followed Dennis Erskine's guidelines from a post I found while searching for advice on positioning.

Due to the way small rooms interact with speakers, the subs+bookshelf approach allows you to place the L/C/R speakers in a location for best imaging, clarity, etc. whilst the sub(s) are located in positions providing the better bass response in the seating locations. Further (assuming an 80Hz crossover between the mains/subs) you'd want your L/C/R's to be more than 3.5' from any wall (floor or ceiling) and your subs less than 3.5' from any wall. If you cannot get the mains more that 3.5' from a wall you'll need 4 or more inches of absorptive materials on all surfaces inside that 3.5' radius. (3.5' is approximately the 1/4 wavelength of the crossover frequency).

So, I set my LCR 3.5 ft from the front wall.

I found something else online regarding distance from side walls that stated mains should be at least 1.7 ft and 1.3x the distance from front wall; in my case this means the speakers should be at least 4.55 ft from the side walls and mine are over 5ft from side walls. I also read a guideline dealing with the difference between reflected distance of speakers to LP and the direct distance of speakers to LP; I don't recall the exact guideline but I think it suggested the reflected distance should be at least 5.5 ft more than the direct distance which my setup allowed. I found something suggesting a LP distance of 38% of room length. I think this is on Ethan's site. I'm around 40-42% which is as close as I can get due to the size of my screen. I tried moving my LP back which resulted in worse sound. I've tried varying toe-in and am happiest with mains pointed directly at the LP.

My acoustic panels are 2" OC703 and will be about 1 inch off the wall. Not quite what you suggest but hopefully enough to provide some benefit.

I have two sheets of OC703 left so guess I can try one on the ceiling and cut the other in half to add 1ft on each side of the screen.

Should one 2"x24"x48" panel be enough on the ceiling?

I have taken measurements with REW and am mostly happy with my subs' performance. I have the mains crossed at 80hz. There's a narrow null at 75hz but rest looks decent. I'll play around with placement more when I have time and think I can likely get an even better response. My concern is addressing the higher frequencies. I listen to music in stereo so the surrounds aren't a factor in what I'm experiencing.
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post #8 of 65 Old 04-11-2013, 07:18 AM - Thread Starter
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Originally Posted by Nethawk View Post


Ben, just a thought but have you experimented with toe-in angle? You look to be 40-45 degrees, you may find that in the new and more symmetrical room somewhat less of an angle may improve your soundstage. It's odd I know, but sound can take on pretty big changes by moving your speakers even an inch.

Nice space! Don't spill red wine on that carpet (he said with the wisdom of experience wink.gif ).

Yes, I've tried all degrees of toe-in and was most pleased with the mains pointed directly at the LP. Less angle created a wider soundstage but less precise imaging (basically the opposite of what I'm trying to achieve).

Thanks, I'm careful with the drinks but do worry about my friends after they've had a few. I'm actually installing a 2nd row of seating with a riser now (should be done this Saturday). Hopefully it doesn't have too bad of an impact on acoustics.
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post #9 of 65 Old 04-11-2013, 07:34 AM
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Quote:
Originally Posted by benunc View Post

What bugs me specifically is that when listening to 2 ch music in my old room, I could pinpoint exactly where the singer's voice was coming from – it was very defined and I could picture exactly where the singer’s mouth was. In the new room, the singer's voice is not as defined and sounds like it’s coming from a larger area. It’s easier to me explain using a visual analogy – the previous sound was like a golf ball and the new sound is like a basketball. I think this is the case with instruments too but it’s most obvious/bothersome to me with the singer’s voice.
 

I feel silly chipping in with all the heavy-hitters here, but it sounds to this amateur like a phase/polarity problem. Did you check the simple stuff first?

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Did you really need to quote that entire post in your reply?
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post #10 of 65 Old 04-11-2013, 08:56 AM
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Originally Posted by benunc View Post

I followed Dennis Erskine's guidelines from a post I found while searching for advice on positioning.

Due to the way small rooms interact with speakers, the subs+bookshelf approach allows you to place the L/C/R speakers in a location for best imaging, clarity, etc. whilst the sub(s) are located in positions providing the better bass response in the seating locations. Further (assuming an 80Hz crossover between the mains/subs) you'd want your L/C/R's to be more than 3.5' from any wall (floor or ceiling) and your subs less than 3.5' from any wall. If you cannot get the mains more that 3.5' from a wall you'll need 4 or more inches of absorptive materials on all surfaces inside that 3.5' radius. (3.5' is approximately the 1/4 wavelength of the crossover frequency).

So, I set my LCR 3.5 ft from the front wall.
Dennis mentions two alternatives, I put absorbtion on my front wall to avoid sacrificing 3.5 feet of space. The speaker/sub placement I mentioned had to do with cancelling width modes in your room. Cancelling peaks & dips across the seating area using speaker positioning means less reliance on treatments and equalization.
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Originally Posted by benunc View Post

My acoustic panels are 2" OC703 and will be about 1 inch off the wall. Not quite what you suggest but hopefully enough to provide some benefit.
It will down to about 500Hz or so. I was suggesting more broadband absorbtion, down to around 100Hz, so that frequency response problems below that could be handled with subwoofer placement.
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Originally Posted by benunc View Post

Should one 2"x24"x48" panel be enough on the ceiling?
If you were to point a flashlight from your centre speaker to its first reflection point on the ceiling, you'd see a circle that is wider than 24". Sound doesn't travel like a narrow beam. So to catch the reflection of the centre speaker, I would use a 48"x48" panel centered at its first reflection point.

However, you're trying to catch the reflections from your L/R speakers, since you don't use your centre speaker when listening to 2-channel music. So you would need two of those panels, in order to be effective. You can have someone slide a mirror across the ceiling while you're seated in your main listening position. I doubt the ceiling reflections from both speakers will fall within one 24"x48" panel.

Sanjay
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post #11 of 65 Old 04-11-2013, 09:18 AM
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Originally Posted by benunc View Post


I’ve attached some pictures of the rooms.
Old room (don’t recall dimensions; speakers probably 1.5 ft off wall; LP up against back wall):


New room (24x19x8; speakers 3.5 ft from front wall and 5 ft from side walls; LP about 10ft from front wall):



The only culprit I can think of is that the old projector screen was solid laminate whereas the new one is a thin material and I have placed Owens Corning insulation panels between it and the window.

I’ve made some new acoustic panels with more OC panels and plan to hang them along the side walls this week but don’t anticipate them making a huge difference in this respect.

.

I see the old room as being kind of irregular and chaotic, while the new one is neat and clean. In room acoustics irregular and chaotic can be very good and regular and clean can be very bad.

The new room needs more chaos and irregularity.
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post #12 of 65 Old 04-11-2013, 09:38 AM - Thread Starter
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Originally Posted by sdurani View Post

Dennis mentions two alternatives, I put absorbtion on my front wall to avoid sacrificing 3.5 feet of space. The speaker/sub placement I mentioned had to do with cancelling width modes in your room. Cancelling peaks & dips across the seating area using speaker positioning means less reliance on treatments and equalization.
It will down to about 500Hz or so. I was suggesting more broadband absorbtion, down to around 100Hz, so that frequency response problems below that could be handled with subwoofer placement.

Since I had the room to move the speakers 3.5 ft off the wall, I just did that. It was cheaper and easier than adding at least 4" thick panels.

I'll try your placement suggestions this weekend.

Quote:
If you were to point a flashlight from your centre speaker to its first reflection point on the ceiling, you'd see a circle that is wider than 24". Sound doesn't travel like a narrow beam. So to catch the reflection of the centre speaker, I would use a 48"x48" panel centered at its first reflection point.

However, you're trying to catch the reflections from your L/R speakers, since you don't use your centre speaker when listening to 2-channel music. So you would need two of those panels, in order to be effective. You can have someone slide a mirror across the ceiling while you're seated in your main listening position. I doubt the ceiling reflections from both speakers will fall within one 24"x48" panel.

Sounds like I need to buy another pack or two of OC703. I can use 4 sheet to thicken the 4 panels I'll have on the side walls to 4". And then sounds like I'd want 48"x48" on the ceiling; not sure I can get away with 4" on the ceiling due to the projector and screen height (I've since raised the screen from where it is in my picture on the earlier post).

Thanks for all the feedback.
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post #13 of 65 Old 04-11-2013, 09:41 AM - Thread Starter
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Originally Posted by arnyk View Post

I see the old room as being kind of irregular and chaotic, while the new one is neat and clean. In room acoustics irregular and chaotic can be very good and regular and clean can be very bad.

The new room needs more chaos and irregularity.

Well I'll have a 1 ft tall riser with a 2nd row of seating up this weekend. I was worried that might have negative acoustic effects but maybe it will actually help. You can't see the back of the room in that photo but I have some bookshelves and a computer desk back there; so the room isn't as bare as it looks.
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post #14 of 65 Old 04-11-2013, 11:31 AM
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Originally Posted by benunc View Post


Sounds like I need to buy another pack or two of OC703. I can use 4 sheet to thicken the 4 panels I'll have on the side walls to 4". And then sounds like I'd want 48"x48" on the ceiling; not sure I can get away with 4" on the ceiling due to the projector and screen height (I've since raised the screen from where it is in my picture on the earlier post).

Simply spacing 2" panels 2" away from the walls has pretty much the same effect as doubling the thickness of the absorbers tp 4"
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post #15 of 65 Old 04-11-2013, 11:33 AM
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Originally Posted by benunc View Post

Quote:
Originally Posted by arnyk View Post

I see the old room as being kind of irregular and chaotic, while the new one is neat and clean. In room acoustics irregular and chaotic can be very good and regular and clean can be very bad.

The new room needs more chaos and irregularity.

Well I'll have a 1 ft tall riser with a 2nd row of seating up this weekend. I was worried that might have negative acoustic effects but maybe it will actually help. You can't see the back of the room in that photo but I have some bookshelves and a computer desk back there; so the room isn't as bare as it looks.

Bookshelves at least partially filled with books usually have acoustical benefits. Thing is they have to cover a high enough percentage of the wall to make a difference. Putting them close to the speakers may help.
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post #16 of 65 Old 04-11-2013, 01:06 PM
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Quote:
Originally Posted by benunc View Post

...What bugs me specifically is that when listening to 2 ch music in my old room, I could pinpoint exactly where the singer's voice was coming from – it was very defined and I could picture exactly where the singer’s mouth was. In the new room, the singer's voice is not as defined and sounds like it’s coming from a larger area. It’s easier to me explain using a visual analogy – the previous sound was like a golf ball and the new sound is like a basketball. I think this is the case with instruments too but it’s most obvious/bothersome to me with the singer’s voice. ...

Would you be surprised to find that some folks would prefer if your basketball were a beachball? (I'm one of them.)

There seem to be two schools, some folks prefer pinpoint imaging with very tight localization and others prefer loudspeakers that disappear into a diffuse, broad sound field. You're in the former group. and everyone's spot on in their advice to treat first reflections. Here's a link to Harman's white papers, and I recommend the second from the bottom, Part 2. The last 20% of this talk addresses imaging with a basic imaging test and some advice on options for improving it using absorbers and diffusers.
http://www.harman.com/EN-US/OurCompany/Innovation/Pages/WhitePapers.aspx

Arny's right about a little space being work lots of low end absorption, and you're starting with 2" panels, not 1" as shown, so your "0" airspace curve is for the 2"panel. You'll get plenty of absorption down to 100Hz with what you've already built if spaced from the wall a little.


Have fun,
frank
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post #17 of 65 Old 04-14-2013, 04:00 PM
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Originally Posted by benunc View Post

Hoping someone has some ideas on something that has been bothering me. Four months ago I moved to a new house and set up my speakers based on what should be ideal positioning but have been disappointed that in some ways the sound is worse than what I had at my previous house which had far from ideal speaker/listening positions. What bugs me specifically is that when listening to 2 ch music in my old room, I could pinpoint exactly where the singer's voice was coming from – it was very defined and I could picture exactly where the singer’s mouth was. In the new room, the singer's voice is not as defined and sounds like it’s coming from a larger area. It’s easier to me explain using a visual analogy – the previous sound was like a golf ball and the new sound is like a basketball. I think this is the case with instruments too but it’s most obvious/bothersome to me with the singer’s voice.

I’ve attached some pictures of the rooms.
Old room (don’t recall dimensions; speakers probably 1.5 ft off wall; LP up against back wall):


New room (24x19x8; speakers 3.5 ft from front wall and 5 ft from side walls; LP about 10ft from front wall):



The only culprit I can think of is that the old projector screen was solid laminate whereas the new one is a thin material and I have placed Owens Corning insulation panels between it and the window.

I’ve made some new acoustic panels with more OC panels and plan to hang them along the side walls this week but don’t anticipate them making a huge difference in this respect.

Any thoughts/suggestions appreciated.

I am so jealous. Your old room is EXACTLY like my existing HT area in my open basement. I have my screen on the wall of my staircase and my couch against the back wall. I am fully open on the left side of my room; and I have a wall 10' to the right of my screen.

Someday soon, when my kids are grown, I will either take one of their (rather large) bedrooms, or, move into a different house with a better suited room for acoustics.

BTW, my room sounds great; except for bass issues and reflections caused by the back wall. I am currently in process of purchasing bass traps for the back corner and wall, and, absorbers for my first reflection points on the right wall. Also, I just recently experimented by pulling my couch out from the wall by 33% of the distance from the front to the back wall. The improvement in the my bass and surround information is HUGE!! As a plus I am now able to install side speakers for 7.1. My drawback is that I am only 9 feet back from my 106" diag screen.

Congrats on the new place!

David Lynch
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post #18 of 65 Old 04-14-2013, 09:20 PM
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Originally Posted by jdlynch View Post

My drawback is that I am only 9 feet back from my 106" diag screen.
When you watch 'Dark Knight', you get the IMAX effect at home. Hardly a drawback. Besides, your 46 degree viewing angle isn't as big as some of the home theatres I've seen locally.

Sanjay
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post #19 of 65 Old 04-15-2013, 04:13 AM
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Originally Posted by sdurani View Post

When you watch 'Dark Knight', you get the IMAX effect at home. Hardly a drawback. Besides, your 46 degree viewing angle isn't as big as some of the home theatres I've seen locally.

Sanjay-

You and I are in full agreement. Would you do me a favor: Please call my wife and convince her that 9' is not too close? smile.gif

David

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post #20 of 65 Old 04-15-2013, 04:17 AM
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Quote:
Originally Posted by sdurani View Post

When you watch 'Dark Knight', you get the IMAX effect at home. Hardly a drawback. Besides, your 46 degree viewing angle isn't as big as some of the home theatres I've seen locally.

Sanjay-

You and I are in full agreement. Would you do me a favor: Please call my wife and convince her that 9' is not too close? smile.gif

I don't know if it is a gender thing or what, but I sense that many women are not comfortable with more immersive media experiences. Either they just want their space, or they are sensitive to the fact that immersion is often done badly.
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post #21 of 65 Old 04-15-2013, 05:58 AM - Thread Starter
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Originally Posted by arnyk View Post

Simply spacing 2" panels 2" away from the walls has pretty much the same effect as doubling the thickness of the absorbers tp 4"

I got 4 of my panels hung this past weekend. I'd already made them a couple weeks ago but hadn't gotten around to hanging yet. They are 2" thick but based on feedback in this thread, I was thinking I'd try to add a second panel behind what I'd made. Unfortunately, the framing isn't as deep as I was thinking so I don't think there's a good way for me do that. I didn't see your post until now or else I'd have tried mounting them further off the wall than I did. I'll probably try remounting them this week/weekend to get them a full 2" off the wall. Thanks for the suggestion.

As is, they do seem to help but still don't get me where I want to be. Might be in my head but female vocals seem more defined than male; maybe b/c of the higher frequency?

I have 2 more sheets of OC703 that I plan to mount to the ceiling this week too so hopefully they help further.
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post #22 of 65 Old 04-15-2013, 06:16 AM
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My take on it:
Put dampening material on the front wall from corner to the screen - floor too ceiling (4-6" thick). Move the front speaker back against them and up towards subwoofers, keeping the same angle to listening, move sofa if needed.
Put diffusion on side walls. Buy another 6 subwoofers and stack them. Some ceiling diffusion. Consider more surround speakers, even if they play the same channel, higher up the farther back they go.

Under construction: the Larch theater
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post #23 of 65 Old 04-15-2013, 06:36 AM - Thread Starter
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Originally Posted by fbov View Post

Would you be surprised to find that some folks would prefer if your basketball were a beachball? (I'm one of them.)

There seem to be two schools, some folks prefer pinpoint imaging with very tight localization and others prefer loudspeakers that disappear into a diffuse, broad sound field. You're in the former group. and everyone's spot on in their advice to treat first reflections. Here's a link to Harman's white papers, and I recommend the second from the bottom, Part 2. The last 20% of this talk addresses imaging with a basic imaging test and some advice on options for improving it using absorbers and diffusers.
http://www.harman.com/EN-US/OurCompany/Innovation/Pages/WhitePapers.aspx

Arny's right about a little space being work lots of low end absorption, and you're starting with 2" panels, not 1" as shown, so your "0" airspace curve is for the 2"panel. You'll get plenty of absorption down to 100Hz with what you've already built if spaced from the wall a little.


Have fun,
frank


I can see why some would prefer the larger sound stage but I like hearing exactly where each instrument and singer is.

Thanks for the link, I'll read that.

If I understand your charts, it looks like I'm getting 20% absorption at 125hz with 1" spacing off the wall. But it doesn't look like spacing and thickness have the same effect - i.e., 3" thick and 0" spacing absorbs 60% at 125hz while 1" thick and 3" spacing only absorbs 20%. What level of absorption should I be shooting for?
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post #24 of 65 Old 04-15-2013, 06:44 AM
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Hi, In your first pic the speaker appears to be pointed straight at you. In the 2nd the speakers are pointed at each other directly across which seems not a good idea to me.

I am not up on new sound systems at all but I am an expert in old school setups and whenever I set up my speakers I turn them away from the audience at 45 degree angles or straight at the audience but slightly turned to the sides away from each other's signal because I don't want the sound from the speakers to shoot straight toward each other which could cause feedback or some interference.
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post #25 of 65 Old 04-15-2013, 06:50 AM - Thread Starter
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Originally Posted by jdlynch View Post

I am so jealous. Your old room is EXACTLY like my existing HT area in my open basement. I have my screen on the wall of my staircase and my couch against the back wall. I am fully open on the left side of my room; and I have a wall 10' to the right of my screen.

Someday soon, when my kids are grown, I will either take one of their (rather large) bedrooms, or, move into a different house with a better suited room for acoustics.

BTW, my room sounds great; except for bass issues and reflections caused by the back wall. I am currently in process of purchasing bass traps for the back corner and wall, and, absorbers for my first reflection points on the right wall. Also, I just recently experimented by pulling my couch out from the wall by 33% of the distance from the front to the back wall. The improvement in the my bass and surround information is HUGE!! As a plus I am now able to install side speakers for 7.1. My drawback is that I am only 9 feet back from my 106" diag screen.

Congrats on the new place!

Thanks man. A nice room for my theater was one of my most important criteria when house searching. Not many homes have basements around here and most bonus rooms are over garages and are narrow with slanted ceilings so I'm very happy with the size/shape of this room. My old room actually sounded pretty good to me and I got a much flatter bass response; the worst part was that it was a town house with neighbors attached on both sides so I couldn't crank it up as much as I'd like. I'm now sitting 10 ft back from a 110" diag screen which is as close as I'd want to be but doesn't feel too close.

Here's a picture with the riser that was finished this past weekend and the side acoustic panels hung.
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post #26 of 65 Old 04-15-2013, 07:58 AM
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How high did you make your riser?

David Lynch
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post #27 of 65 Old 04-15-2013, 08:01 AM - Thread Starter
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Originally Posted by Nightlord View Post

My take on it:
Put dampening material on the front wall from corner to the screen - floor too ceiling (4-6" thick). Move the front speaker back against them and up towards subwoofers, keeping the same angle to listening, move sofa if needed.
Put diffusion on side walls. Buy another 6 subwoofers and stack them. Some ceiling diffusion. Consider more surround speakers, even if they play the same channel, higher up the farther back they go.

8" of insulation over the entire front wall and 6 more subs aren't going to happen even if I wanted; my wife will make sure of that. I'll probably add one more 2-4" panel on each side of the screen and maybe another another couple along the side walls eventually. No intentions of adding subs any time soon - the two up front are 18" Daytons I just build and I have an Epik Legend half way down a side wall and an Epik Empire near a rear corner - I can hit down to the low teens and play louder than I'd ever listen. I did consider adding another pair of surrounds for the 2nd seating row but think it would create more acoustic problems than it would resolve (I do have a rear speaker for which helps in the second row).
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post #28 of 65 Old 04-15-2013, 08:11 AM - Thread Starter
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Originally Posted by jdlynch View Post

How high did you make your riser?

12" + maybe 1.25" top. I used a calculator I found in some thread to determine height needed and ended up exceeding it by maybe an inch. Unfortunately my head ended up blocking the bottom inch or so of screen when my wife tried sitting in the 2nd row behind me. I'm about 6'2 and she's maybe 5'4 so I imagine that was a factor. If the front seats are reclined a bit, it's OK (as long as the 2nd row doesn't recline too I guess). I only have 8' ceilings so wouldn't have wanted to go any higher with the riser anyways; I come close to bumping my head on the projector as it is. If it ends up being a problem for others, I might try adding an inch or so block under the 2nd row seats' legs.
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post #29 of 65 Old 04-15-2013, 11:32 AM
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Originally Posted by benunc View Post

If I understand your charts, it looks like I'm getting 20% absorption at 125hz with 1" spacing off the wall.
Left chart is on-wall. You're getting about 25% absorption from a 2" panel on-wall; 0 spacing. You gain ~15% from 2" spacing for a 40% total.
Quote:
...But it doesn't look like spacing and thickness have the same effect - i.e., 3" thick and 0" spacing absorbs 60% at 125hz while 1" thick and 3" spacing only absorbs 20%. What level of absorption should I be shooting for?

Correct, spacing and thickness are not interchangeable.
- thickness increases the amount of absorber present, so it increases the energy absorbed
- spacing it away from the wall just shifts the low frequency roll-off down in frequency.

Level of absorption... no good answer without data. You're not shooting for a level of absorption so much as a decay rate for sound in the room. You want to measure room decay time as a function of frequency, aka a waterfall plot. Typical criteria are:
- 0.3 sec for a -40dB decay at all frequencies
- no modal resonances extending beyond 0.4 to 0.5 sec.

A waterfall plot will show decay at all frequencies.
- add absorption at frequencies that exceed 0.3 sec
- swap diffusion for absorption at frequencies that have much less than 0.3 sec decay
- tell us about any modal issues and ask what folks have done; bass is very hard to absorb.

HAve fun,
Frank
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post #30 of 65 Old 04-15-2013, 01:44 PM - Thread Starter
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Originally Posted by fbov View Post

Level of absorption... no good answer without data. You're not shooting for a level of absorption so much as a decay rate for sound in the room. You want to measure room decay time as a function of frequency, aka a waterfall plot. Typical criteria are:
- 0.3 sec for a -40dB decay at all frequencies
- no modal resonances extending beyond 0.4 to 0.5 sec.

A waterfall plot will show decay at all frequencies.
- add absorption at frequencies that exceed 0.3 sec
- swap diffusion for absorption at frequencies that have much less than 0.3 sec decay
- tell us about any modal issues and ask what folks have done; bass is very hard to absorb.

HAve fun,
Frank

Gotcha, makes sense. I've run waterfall graphs in REW when calibrating my subs but don't think I've ever looked at a full range plot. I'll pull the measurement equipment out this weekend and see how it looks. I know I have low frequencies that extend well past 300ms in places; I'll probably get around to building bass traps at some point. I have doors in the back room corners so don't think I can add any back there but could place a couple in the front corners behind where the subs currently are. I still plan to experiment with moving subs around based on an earlier suggestion in this thread too.
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