What are the characteristics of a hypothetical room designed for ideal acoustics? - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 6Likes
Reply
 
Thread Tools
post #1 of 34 Old 08-23-2019, 08:28 AM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Question What are the characteristics of a hypothetical room designed for ideal acoustics?

What are the characteristics of a hypothetical room designed for ideal acoustics? What are its dimensions? Is the floor hardwood, carpeted, or some other material? If it is hardwood (or otherwise reflective), where should rugs be placed, if at all? What types of furniture should be in the room, and what materials should they be made out of?
Skinfax1 likes this.
Drew Neilson is offline  
Sponsored Links
Advertisement
 
post #2 of 34 Old 08-23-2019, 08:35 AM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
I had to type the above post before I realized that I needed to search Bing (my preferred search engine) for [ideal room characteristics for best acoustics].
Drew Neilson is offline  
post #3 of 34 Old 08-23-2019, 08:47 AM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
In case anyone is going to ask why I am asking such a broad, open-ended question as 'what are the characteristics of a hypothetical room designed for ideal acoustics', it is this: I may have the opportunity to move my A/V setup from one room to another in the same house, and I may look at other places to live for reasons unrelated to getting better sound. In either case, it would be good for me to know what to look for in a room in order to choose a room with the best possible characteristics, and also what I can do to further improve a room once I have chosen one.
Skinfax1 likes this.
Drew Neilson is offline  
Sponsored Links
Advertisement
 
post #4 of 34 Old 08-23-2019, 09:20 AM
AVS Forum Addicted Member
 
Ratman's Avatar
 
Join Date: May 2002
Location: Collingswood, N.J.
Posts: 19,220
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2299 Post(s)
Liked: 2156
Next to impossible to provide a definitive answer. Too many variables to provide a "one size fits all". Of course..... in my opinion.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
Ratman is offline  
post #5 of 34 Old 08-23-2019, 10:08 AM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Here's a starting point:
  • Acoustic symmetry is beneficial.
  • A rectangular room is beneficial.
  • A "suspended" floor will have different acoustic properties than a concrete slab.
  • Modal response is somewhat predictable using online calculators, but the models for the prefect room dimensions are elusive. Just try not to have the dimensions as multiple of each other and you should be fine.
  • The ability to acoustically treat the room is helpful. IOW, look at where windows and door are placed.
  • Make sure you have the ability to mount the speakers in the correct locations according to the speaker layout you need. IOW, look at where the doors and windows are placed.
  • Consider whether you want a "sealed" room or a room open to other spaces.
  • Consider sound isolation requirements? IOW, how important is it to not allow sound to leak to the rest of the structure? If that is important, you'll want a room that has good acoustic isolation, (soundproofing.)
  • Consider where the seating can be placed for optimal sound quality. (Seating against a wall is NOT good.)
  • Consider the speakers you will be using. Different types of speakers have different setup requirements.
  • If this will be a "Home Theater" space, consider where the display will be mounted. If a projection system, consider if a false wall is necessary. If so, a baffle wall may be beneficial.
I'm sure there are other considerations that others may contribute.


Craig
sdurani likes this.

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System
craig john is offline  
post #6 of 34 Old 08-23-2019, 10:31 AM
AVS Forum Addicted Member
 
Ratman's Avatar
 
Join Date: May 2002
Location: Collingswood, N.J.
Posts: 19,220
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2299 Post(s)
Liked: 2156
Stereo only or "home theater"? (may determine size desires)
5.1/7.1/Atmos? (If theater)
Carpet type? (shag, berber, wall to wall)
Size of doorways?
Furniture type? (wood, metal with glass tops)
Seating type? (couch, chair ( seating for 1,2,4,8))
Cloth, leather, one row, two rows?
If theater... type/size of TV/screen? (projection, OLED, LCD, etc)
Where will equipment be located? (in same room in a rack, closet in same room,)


Sorry, but just throwing out some initial thoughts.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
Ratman is offline  
post #7 of 34 Old 08-23-2019, 04:27 PM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by craig john View Post
Here's a starting point:
  • Acoustic symmetry is beneficial.
  • A rectangular room is beneficial.

I'm not positive that I understand what you mean, but I'm going to guess that those two things go together, and that the left speaker's distance from the left wall should equal the right speaker's distance from the right wall, the left side-surround speaker's distance from the left wall should equal the right side surround speaker's distance from the right wall, all three of the front speakers should be equidistant from the front wall, and both of the rear surround speakers (if present) should be equidistant from the rear wall, and all three of the front speakers' distance from the front wall should equal both rear speakers' (if present) distance from the rear wall. And I think I read that in a 5.1 speaker setup, me, my center speaker, and my left side surround speaker should form a triangle whose largest angle is 90-110 degrees. Aim all five speakers towards the listening position (towards its center, I assume). I only have a 5.0 speaker setup, so I haven't read much about ideal placement of rear-surround speakers and height speakers, but I might have them in the future.

Quote:
Originally Posted by craig john View Post
  • A "suspended" floor will have different acoustic properties than a concrete slab.
Is one better than the other?

Quote:
Originally Posted by craig john View Post
  • Modal response is somewhat predictable using online calculators, but the models for the prefect room dimensions are elusive.
Are there calculators that will predict the acoustics of a rectangular room when given that room's dimensions, assuming that all speakers are placed appropriately? Are they using Dolby's speaker placement recommendations, or someone else's?

Quote:
Originally Posted by craig john View Post
Just try not to have the dimensions as multiple of each other and you should be fine.
As in, don't have the distance from the front wall to the back wall be a multiple of the distance from the left wall to the right wall (or vice-versa)?

Quote:
Originally Posted by craig john View Post
  • The ability to acoustically treat the room is helpful. IOW, look at where windows and door are placed.
  • Make sure you have the ability to mount the speakers in the correct locations according to the speaker layout you need. IOW, look at where the doors and windows are placed.
Hmm, I'm sensing a theme here. Is it the location of doors and windows? 😉

Quote:
Originally Posted by craig john View Post
  • Consider whether you want a "sealed" room or a room open to other spaces.
Previously, when I saw images of dedicated theater rooms in people's homes, with seating arranged in rows as in real movie theater auditoriums, those rooms always looked 'cold' or 'unfriendly' to me because those are single-purpose rooms; you go in there to watch TV shows and movies, and maybe play video games. You don't go in there with other people and do social activities with them, because the seating is arranged such that you can't look everyone face-to-face. So it's not like a living room, where you can all watch a TV show OR play a board game OR play Twister, for example. So I always thought that a multipurpose living room and media room was a better idea.
If anyone has any counterpoints to this, I'd be interested in hearing them.

Quote:
Originally Posted by craig john View Post
  • Consider sound isolation requirements? IOW, how important is it to not allow sound to leak to the rest of the structure? If that is important, you'll want a room that has good acoustic isolation, (soundproofing.)
That would be ideal, no matter whether the room is a dedicated theater room or a multipurpose room. However, I read a little about that, and it kinda seems like if a room is not already soundproof, soundproofing is only possible by remodeling it--tearing down and rebuilding its walls, floor, and ceiling in order to put up soundproof walls, floor, and ceiling. That's not possible for people who are renting their home, are looking for a place to rent, or own their home but don't have a lot of money. I guess that if I look for a new place to live--which would mostly be for other reasons--I could try to find a place that has a soundproof room that is acoustically optimal, but I don't know how much that would increase the monthly rent price or sale price.
I get why soundproofing is ideal: it lets people watch TV shows and movies at a decent volume without disturbing other people in other rooms.

Quote:
Originally Posted by craig john View Post
  • Consider the speakers you will be using. Different types of speakers have different setup requirements.
Can you elaborate?
Drew Neilson is offline  
post #8 of 34 Old 08-23-2019, 04:56 PM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by Ratman View Post
Stereo only or "home theater"? (may determine size desires)
5.1/7.1/Atmos? (If theater)
Right now, only 5.0 (I don't have a subwoofer), but my system might grow.

Quote:
Originally Posted by Ratman View Post
Carpet type? (shag, berber, wall to wall)
I mean, I'm trying to find out what type of floor would be acoustically ideal. I don't have a specific type in mind yet. Same thing with other characteristics of the room.

Quote:
Originally Posted by Ratman View Post
Size of doorways?
Is this only relevant to their position in the room, or is it relevant for other reasons as well?

Quote:
Originally Posted by Ratman View Post
Furniture type? (wood, metal with glass tops)
Seating type? (couch, chair ( seating for 1,2,4,8))
Cloth, leather, one row, two rows?
I'm trying to find out what characteristics would be acoustically ideal.

Quote:
Originally Posted by Ratman View Post
If theater... type/size of TV/screen? (projection, OLED, LCD, etc)
Right now, my TV is a 47" LED LCD TV, but that might change.

Quote:
Originally Posted by Ratman View Post
Where will equipment be located? (in same room in a rack, closet in same room,)
I don't know.
Drew Neilson is offline  
post #9 of 34 Old 08-23-2019, 11:30 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,478
Mentioned: 45 Post(s)
Tagged: 0 Thread(s)
Quoted: 5094 Post(s)
Liked: 3711
Quote:
Originally Posted by Drew Neilson View Post
What are the characteristics of a hypothetical room designed for ideal acoustics? What are its dimensions?
Depends if it is for an audience of one or for a big family but there's some stuff here which might be of interest. It's how professional laboratories design rooms for critical evaluations. Dolby Labs uses it for instance.
See section 8 Listening Conditions including "Reference Listening Room"

Last edited by m. zillch; 08-24-2019 at 09:41 AM.
m. zillch is offline  
post #10 of 34 Old 08-24-2019, 08:38 AM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Quote:
Originally Posted by Drew Neilson View Post
[/LIST]
I'm not positive that I understand what you mean, but I'm going to guess that those two things go together, and that the left speaker's distance from the left wall should equal the right speaker's distance from the right wall, the left side-surround speaker's distance from the left wall should equal the right side surround speaker's distance from the right wall, all three of the front speakers should be equidistant from the front wall, and both of the rear surround speakers (if present) should be equidistant from the rear wall, and all three of the front speakers' distance from the front wall should equal both rear speakers' (if present) distance from the rear wall. And I think I read that in a 5.1 speaker setup, me, my center speaker, and my left side surround speaker should form a triangle whose largest angle is 90-110 degrees. Aim all five speakers towards the listening position (towards its center, I assume). I only have a 5.0 speaker setup, so I haven't read much about ideal placement of rear-surround speakers and height speakers, but I might have them in the future.
Correct. You don't want one speaker to "live" in a different acoustic environment than another. Speakers come in matched pairs so they "match". This is important for sounds that pan around the listening space and for imaging. For example, if you're trying to project a "phantom" sonic image from between two speakers, they both need to sound the same, or the image won't be precise or stable. If you put them into different acoustic environments, they'll no longer match. If sounds pan around from speaker to speaker, you don't want the tone of the sound to change as it moves from speaker to speaker.

Quote:
Originally Posted by Drew Neilson View Post
Is one better than the other?
A suspended floor can be made to provide tactile response. A subwoofer system, or even good full-range speakers, can acoustically couple with the floor and cause it to "shake." That causes motion energy to be transferred to the seating and the listener. Some people REALLY like that, others don't. Personally, I love it. If you're on a concrete slab, tactile response is virtually eliminated. In that case, you can add it with tactile transducers. That's what I have done in my HT: https://www.avsforum.com/forum/113-s...rs-thread.html In the subwoofer forum, there are numerous threads about adding tactile response.


No matter what the construction of the floor, it is beneficial to absorb some of the reflected sound from the floor, Carper, area rugs, etc. can help, the thicker, the better IMO.

Quote:
Originally Posted by Drew Neilson View Post
Are there calculators that will predict the acoustics of a rectangular room when given that room's dimensions, assuming that all speakers are placed appropriately? Are they using Dolby's speaker placement recommendations, or someone else's?
There are a number of calculators that predict the "modal response" of the room. Just Google "Room Mode Calculators." However, they are predicated on rectangular rooms. If the room is not rectangular, all bets are off. Even if they are rectangular, the construction of the boundaries will impact the *actual* modal response. Therefore, the calculators are only modestly useful. There are some *theoretically * ideal room dimensions that spread the room modes out across the bandwidth, but following them is not as necessary as some claim. Just make sure the dimensions are not multiple of each other. IOW, a 12' x 24' x 12' room would not be ideal. It can still work, but 13' x 23' x 9' would work better.

Quote:
Originally Posted by Drew Neilson View Post
As in, don't have the distance from the front wall to the back wall be a multiple of the distance from the left wall to the right wall (or vice-versa)?
Exactly.

Quote:
Originally Posted by Drew Neilson View Post
Hmm, I'm sensing a theme here. Is it the location of doors and windows? 😉
Yes, The locations of doors and windows will impact a number of things. Ingress/Egress. Speaker placement. Placement of acoustic treatments. Light spillage onto displays. Sound leakage into adjacent spaces and/or outdoors, etc. The "ideal" room has no doors or windows. You lock yourself in and you can never leave, just like Hotel California!

Quote:
Originally Posted by Drew Neilson View Post
Previously, when I saw images of dedicated theater rooms in people's homes, with seating arranged in rows as in real movie theater auditoriums, those rooms always looked 'cold' or 'unfriendly' to me because those are single-purpose rooms; you go in there to watch TV shows and movies, and maybe play video games. You don't go in there with other people and do social activities with them, because the seating is arranged such that you can't look everyone face-to-face. So it's not like a living room, where you can all watch a TV show OR play a board game OR play Twister, for example. So I always thought that a multipurpose living room and media room was a better idea. If anyone has any counterpoints to this, I'd be interested in hearing them.
No counterpoints, just different design goals. One is a dedicated Home Theater, the other is a media system in a communal living space. However, it's almost impossible to design a "living space" as an ideal acoustic and viewing space.

Quote:
Originally Posted by Drew Neilson View Post
That would be ideal, no matter whether the room is a dedicated theater room or a multipurpose room. However, I read a little about that, and it kinda seems like if a room is not already soundproof, soundproofing is only possible by remodeling it--tearing down and rebuilding its walls, floor, and ceiling in order to put up soundproof walls, floor, and ceiling. That's not possible for people who are renting their home, are looking for a place to rent, or own their home but don't have a lot of money. I guess that if I look for a new place to live--which would mostly be for other reasons--I could try to find a place that has a soundproof room that is acoustically optimal, but I don't know how much that would increase the monthly rent price or sale price.
I get why soundproofing is ideal: it lets people watch TV shows and movies at a decent volume without disturbing other people in other rooms.
Yes adequate soundproofing or sound isolation is not for the feint of heart. It's pretty much an "all or nothing proposition. If you can't do it completely, there is only limited benefit to doing it "a little bit."

Quote:
Originally Posted by Drew Neilson View Post
Can you elaborate?
Speakers can have all sorts of different dispersion patterns, and their dispersion patterns can impact their placement in the room. You don't want to place a speaker that fires to the front and the rear. (bipoles/dipoles), close to the rear wall. You want some distance behind the speaker to allow it to reflect off the rear wall properly. You don't want to place a speaker with wide dispersion too close to the side walls because you'll get reflections and boundary interference effects. OTOH, some wide dispersion speakers benefit from those reflections. On-walls or in-walls have their own set of criteria. Also, acoustic treatments can modify and ameliorate the effects, (remember the doors and windows.)

Bottom line, a listening room and the audio system within it work in a symbiotic relationship. Ideally, the entire *system* should be designed as a whole to work together cohesively. There are always compromises, but starting with the "ideal" as the target allows one to understand the impact of the compromises.

Good luck and have fun.

https://realtraps.com/art_room-setup.htm
https://routledgetextbooks.com/textbooks/9781138921368/

Craig

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

Last edited by craig john; 08-24-2019 at 08:48 AM.
craig john is offline  
post #11 of 34 Old 08-25-2019, 09:08 AM
Member
 
Join Date: Apr 2015
Location: Silicon Valley
Posts: 70
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 31 Post(s)
Liked: 21
Choose your speakers first, this determines speaker location requirements within the room and reflection points which are all critical to all the rest of your room design.

You have to start somewhere and speaker choice is best

Jim Meader
JimMeader is offline  
post #12 of 34 Old 08-25-2019, 12:07 PM
AVS Forum Special Member
 
asarose247's Avatar
 
Join Date: Mar 2010
Location: DIY enabled in SoCal / OC
Posts: 4,402
Mentioned: 104 Post(s)
Tagged: 2 Thread(s)
Quoted: 1234 Post(s)
Liked: 1079
This "journey' and careful, deliberate and debated assemblage of info and necessary compromises

follow the research , contributors , choices, whys and why-nots,

https://www.avsforum.com/forum/19-de...ter-build.html

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS V2, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x 6000DSP
asarose247 is offline  
post #13 of 34 Old 08-25-2019, 01:35 PM
AVS Forum Special Member
 
asarose247's Avatar
 
Join Date: Mar 2010
Location: DIY enabled in SoCal / OC
Posts: 4,402
Mentioned: 104 Post(s)
Tagged: 2 Thread(s)
Quoted: 1234 Post(s)
Liked: 1079
then I listen to these guys . .


and think . . .
You're gonna need a bigger room" . .

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS V2, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x 6000DSP
asarose247 is offline  
post #14 of 34 Old 08-26-2019, 03:33 AM
Senior Member
 
Skinfax1's Avatar
 
Join Date: Feb 2018
Posts: 255
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 197 Post(s)
Liked: 65
@Drew Neilson
Congratulation on asking that question.



Good sound is always the result of engineering. And engineering always starts with measuring. Consumer industry and mainstream will never tell customers about that: improvements in room acoustics are worth roughly ten (10!) times the amount spent on equipment like speakers and receivers. For example: only $500 in room treatment is worth more than spending $5000 (fivethousand) on equipment.
Skinfax1 is offline  
post #15 of 34 Old 08-27-2019, 06:27 AM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by craig john View Post
A suspended floor can be made to provide tactile response. A subwoofer system, or even good full-range speakers, can acoustically couple with the floor and cause it to "shake." That causes motion energy to be transferred to the seating and the listener. Some people REALLY like that, others don't. Personally, I love it. If you're on a concrete slab, tactile response is virtually eliminated. In that case, you can add it with tactile transducers. That's what I have done in my HT: https://www.avsforum.com/forum/113-s...rs-thread.html In the subwoofer forum, there are numerous threads about adding tactile response.
Are suspended floors something that I'd only find in purpose-built home theater rooms?

I'd be concerned about the floor vibrating with some errant frequencies; I'm not sure what the technical term for that is. EDIT: The technical term might include the word 'resonate', but I still can't remember the exact technical term.

Quote:
Originally Posted by craig john View Post
No matter what the construction of the floor, it is beneficial to absorb some of the reflected sound from the floor, Carper, area rugs, etc. can help, the thicker, the better IMO.
So you think that carpet is better than plain hardwood or otherwise reflective flooring? That's helpful, because the room that I'm considering moving my A/V equipment to is carpeted, and when I look at other places to live, I can try to find a place with a multipurpose room or dedicated theater room that has carpeted flooring.

Quote:
Originally Posted by craig john View Post
There are a number of calculators that predict the "modal response" of the room. Just Google "Room Mode Calculators." However, they are predicated on rectangular rooms. If the room is not rectangular, all bets are off. Even if they are rectangular, the construction of the boundaries will impact the *actual* modal response.
I think that "boundaries" means the floor, walls, and ceiling. So you're saying that how the walls, floor, and ceiling were built, and what materials they were built with, will impact the modal response. That makes sense. What materials are best?

Quote:
Originally Posted by craig john View Post
Therefore, the calculators are only modestly useful. There are some *theoretically * ideal room dimensions that spread the room modes out across the bandwidth
Quote:
Originally Posted by craig john View Post
spread the room modes out across the bandwidth
What are "room modes" and "bandwidth"?

Quote:
Originally Posted by craig john View Post
Ingress/Egress.
Does that mean entry and exit, as in 'the location of the doors will affect where people enter and exit the room'?

Quote:
Originally Posted by craig john View Post
Speaker placement. Placement of acoustic treatments. Light spillage onto displays. Sound leakage into adjacent spaces and/or outdoors, etc. The "ideal" room has no doors or windows. You lock yourself in and you can never leave, just like Hotel California!
Hotel California allows its residents to check out anytime they like, even though they can never leave.

Quote:
Originally Posted by craig john View Post
No counterpoints, just different design goals. One is a dedicated Home Theater, the other is a media system in a communal living space. However, it's almost impossible to design a "living space" as an ideal acoustic and viewing space.
If I were building a room from scratch or were remodeling a room, could I design it to be acoustically perfect and still be a 'living' room? I guess that the seating is the main problem: if the seating is arranged such that everyone can see each other, then not everyone is facing the screen, and not everyone is inside of the acoustic sweet spot. What other trade-offs are there when it comes to choosing a living room over a dedicated theater room? On the other hand, what trade-offs are there when it comes to choosing a dedicated theater room instead of a living room?

And what about furniture in a living room? What impact does furniture have on the acoustics? I understand that more furniture = more acoustic reflections, but how do different types of furniture and the materials that they are made out of impact acoustics? 100% wooden furniture (such as a table) vs a couch with cushions?

Quote:
Originally Posted by craig john View Post
Speakers can have all sorts of different dispersion patterns, and their dispersion patterns can impact their placement in the room. You don't want to place a speaker that fires to the front and the rear. (bipoles/dipoles), close to the rear wall. You want some distance behind the speaker to allow it to reflect off the rear wall properly. You don't want to place a speaker with wide dispersion too close to the side walls because you'll get reflections and boundary interference effects.
Is there a general rule for how much space should exist between the front speakers and the side walls, and how much space should exist between the rear speakers (if present) and the side walls? I understand that ideally, I'd know the dispersion patterns of all of my speakers and choose the amount of space between them and the side walls accordingly, but a general rule would be helpful for those of us that don't know the dispersion patterns of our speakers.

Last edited by Drew Neilson; 08-27-2019 at 06:32 AM.
Drew Neilson is offline  
post #16 of 34 Old 08-27-2019, 12:09 PM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Quote:
Originally Posted by Drew Neilson View Post
Are suspended floors something that I'd only find in purpose-built home theater rooms?

I'd be concerned about the floor vibrating with some errant frequencies; I'm not sure what the technical term for that is. EDIT: The technical term might include the word 'resonate', but I still can't remember the exact technical term.
A "suspended" floor is a floor not connected to the earth. IOW, a first floor over a basement or crawl space would be "suspended." The suspension system would be the floor joists, subfloor and flooring. Since these have no immediate contact with the foundation of the earth, they have the ability to move. "Resonate" is the correct term. "Shake" is the other correct term.

Quote:
Originally Posted by Drew Neilson View Post
So you think that carpet is better than plain hardwood or otherwise reflective flooring? That's helpful, because the room that I'm considering moving my A/V equipment to is carpeted, and when I look at other places to live, I can try to find a place with a multipurpose room or dedicated theater room that has carpeted flooring.
Reflective flooring causes... reflections. Those reflections of the soundwaves can combine and interfere with the direct soundwaves causing reinforcements and cancellations, which change the sound that arrives at your ears. Floor bounces are generally not considered beneficial, and absorption of them is usually desired. A thicker cut-pyle carpet will absorb more sound than a thin berber style carpet. The pad can also be sound deadening. The thicker the carpet/pad system is, the lower in frequency it will absorb.

Quote:
Originally Posted by Drew Neilson View Post
I think that "boundaries" means the floor, walls, and ceiling. So you're saying that how the walls, floor, and ceiling were built, and what materials they were built with, will impact the modal response. That makes sense. What materials are best?
This is a complex subject as there are many different construction techniques, even within the range of "studs and drywall." Plus, there are two dissimilar goals for wall construction techniques, sound absorption and sound proofing. Some walls flex and the flexing absorbs acoustic energy. Other don't flex nearly as much and reflect more energy. Concrete walls don't flex at all and reflect virtually all the acoustic energy that hits them. I don't want to get into all that but if you want more info, try googling "wall construction for sound absorption."

Bottom line, for in-room sound treatment, most people recommend flexible interior wall like your standard stud walls with 1/2" drywall, glued and screwed.

Quote:
Originally Posted by Drew Neilson View Post
What are "room modes" and "bandwidth"?
Room Modes: http://www.acousticfrontiers.com/room-modes-101/
Bandwidth: the total band of frequencies of interest. In the context I used it, I meant the modal frequencies, usually from about 20 Hz to about 200 to 400 Hz, depending on the size of the room.

Quote:
Originally Posted by Drew Neilson View Post
Does that mean entry and exit, as in 'the location of the doors will affect where people enter and exit the room'?
Yes. The location of the door(s) will impact where people will enter or leave, but will also impact the acoustics, speaker placements, furniture placements, ability to place acoustic treatments, etc. Likewise with windows.

Quote:
Originally Posted by Drew Neilson View Post
Hotel California allows its residents to check out anytime they like, even though they can never leave.
Exactly.

Quote:
Originally Posted by Drew Neilson View Post
If I were building a room from scratch or were remodeling a room, could I design it to be acoustically perfect and still be a 'living' room? I guess that the seating is the main problem: if the seating is arranged such that everyone can see each other, then not everyone is facing the screen, and not everyone is inside of the acoustic sweet spot. What other trade-offs are there when it comes to choosing a living room over a dedicated theater room? On the other hand, what trade-offs are there when it comes to choosing a dedicated theater room instead of a living room?
A living room or family room is a place for socialization. A dedicated theater is a space with one and only one purpose: viewing movies and television.

In a living room, many, many things affect the ability to implement a "hypothetical room deasign for ideal acoustics": seating arrangements, visibility of speakers, subwoofers and electronic equipment, (aesthetics and "WAF" or "Wife Acceptance Factor), placement of video screens, (i.e., above the fireplace is BAD), selection of flat panel TV vs projector and screen, etc, etc, etc. Many, many things can be optimized in a dedicated theater that must be compromised in a living room. The number and magnitude of the compromises will vary depending on how the living/family room is utilized, and some of those compromises can also carry over to dedicated theaters, but in general, it is far easier to optimize a dedicated space than to try and cram a Home Theater in to a living/family room. Nonetheless, many people do it... and thoroughly enjoy the results.

Quote:
Originally Posted by Drew Neilson View Post
And what about furniture in a living room? What impact does furniture have on the acoustics? I understand that more furniture = more acoustic reflections, but how do different types of furniture and the materials that they are made out of impact acoustics? 100% wooden furniture (such as a table) vs a couch with cushions?
Soft cushions with padding can work quite well as acoustic absorbers and be benficial for acoustics. More reflective surfaces, like leather, wood, glass, porcelin, etc, will add some reflections, and they may, or may not be diffuse. If diffuse, they're beneficial. If they cause direct reflections, like off of a wooden/glass coffee table situated between the front speakers and the listener, they can cause acoustic interference, which is not beneficial. Also, speaker mounted in "entertainment units generally don't benefit from the internal reflections off the unit. Dedicated Home Theaters would not use an entertainment console.

Quote:
Originally Posted by Drew Neilson View Post
Is there a general rule for how much space should exist between the front speakers and the side walls, and how much space should exist between the rear speakers (if present) and the side walls? I understand that ideally, I'd know the dispersion patterns of all of my speakers and choose the amount of space between them and the side walls accordingly, but a general rule would be helpful for those of us that don't know the dispersion patterns of our speakers.
You've answered your own question. This will depend ENTIRELY on the speakers, so find out what the dispersion characteristics are. Having said that, there are some good guidelines in the link I posted previously summarizing Dr. Toole's book. I would encourage to read that entire website. It has the answers to most, or all of your questions.

Craig

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System
craig john is offline  
post #17 of 34 Old 08-27-2019, 12:53 PM
AVS Forum Addicted Member
 
sdurani's Avatar
 
Join Date: Oct 2001
Location: Monterey Park, CA
Posts: 27,838
Mentioned: 205 Post(s)
Tagged: 0 Thread(s)
Quoted: 7153 Post(s)
Liked: 6163
Quote:
Originally Posted by Drew Neilson View Post
What are "room modes" and "bandwidth"?
When you blow across an empty bottle, the air in that small chamber will resonate (make that booooooh sound). If you enlarge that small chamber to the size of your room, the air inside will still resonate (of course at different frequencies than the empty bottle). These resonances will result in peaks & nulls throughout the room. That means some listeners will be sitting in quiet nulls while other listeners will be hearing loud peaks. It's mostly audible in the bass range.

The good news is that these peaks & nulls are at specific/fixed locations in the room. This allows you to move your seating so that the listeners' ears end up at locations that avoid severe peaks & nulls and instead have smoother frequency response. The fixed locations also allow for subwoofers and speakers to be placed where they will prevent room modes from being excited. If you can prevent a mode from resonating, then it cannot cause peaks & nulls. Which means smoother response AND greater seat-to-seat consistency.

Best part: it's free (doesn't cost anything to experiment with placement of seating, subs and speakers).

Sanjay
sdurani is offline  
post #18 of 34 Old 08-27-2019, 01:42 PM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by craig john View Post
[*]Modal response is somewhat predictable using online calculators, but the models for the prefect room dimensions are elusive. Just try not to have the dimensions as multiple of each other and you should be fine.
Do different companies--Dolby, THX, DTS, etc.--have different speaker placement recommendations? If so, whose speaker placement do these online calculators use?

Quote:
Originally Posted by craig john View Post
[*]The ability to acoustically treat the room is helpful. IOW, look at where windows and door are placed.[*]Make sure you have the ability to mount the speakers in the correct locations according to the speaker layout you need. IOW, look at where the doors and windows are placed.
What is the ideal location for doors? I assume that ideally, the room would have no windows.

Quote:
Originally Posted by craig john View Post
[*]Consider whether you want a "sealed" room or a room open to other spaces.
When I first read this, I figured that you meant that I should ask myself whether I want a dedicated theater room or a multipurpose room. I just realized that you maybe meant something else when you said "a room open to other spaces." I'm not sure what that means.
Drew Neilson is offline  
post #19 of 34 Old 08-27-2019, 02:20 PM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Quote:
Originally Posted by Drew Neilson View Post
Do different companies--Dolby, THX, DTS, etc.--have different speaker placement recommendations? If so, whose speaker placement do these online calculators use?
The online room mode calculators don't consider speaker placements. They calculate the room modes, which are independent of the speaker placements. Room modes are explained in the link I posted. Also, see Sanjay's explanation above.

The speaker placement recommendations are based on angle calculations from the central "sweet spot" listening position. They are pretty much all the same between Dolby, DTS and THX. CC at "0" degrees, L & R at 22 to 30 degrees, side surrounds at 90 to 110 degrees, rear surrounds at 135 to 155 degrees.

Quote:
Originally Posted by Drew Neilson View Post
What is the ideal location for doors? I assume that ideally, the room would have no windows.
Wherever a speaker, a TV, a projection screen, an equipment rack or an acoustic treatment DOESN'T need to go.

Quote:
Originally Posted by Drew Neilson View Post
When I first read this, I figured that you meant that I should ask myself whether I want a dedicated theater room or a multipurpose room. I just realized that you maybe meant something else when you said "a room open to other spaces." I'm not sure what that means.
A room open to other spaces is a room with large openings, (doors, archways, open to a kitchen or hallway, etc.) The acoustics are greatly affected by large openings, and where they're located in relation to the speakers and listening position. A "sealed" room, (one not open to other spaces and "sealed" by closed doors/windows), is easier to pressurize with bass because only the air inside the sealed space needs to be pressurized, ("pressurized" as in sound pressure, not barometric pressure.) An open room needs more subwoofer acoustic input to reach the same pressurization because all the air in the adjacent spaces also needs to be pressurized in addition to the air in the room.




Do you have a specific room or space in mind, or are you starting from scratch designing this room?

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

Last edited by craig john; 08-27-2019 at 02:29 PM.
craig john is offline  
post #20 of 34 Old 08-27-2019, 02:53 PM
AVS Forum Addicted Member
 
Ratman's Avatar
 
Join Date: May 2002
Location: Collingswood, N.J.
Posts: 19,220
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 2299 Post(s)
Liked: 2156
Quote:
Originally Posted by Drew Neilson View Post
What are the characteristics of a hypothetical room designed for ideal acoustics?
Anechoic chamber.
PrimeTime likes this.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
Ratman is offline  
post #21 of 34 Old 08-27-2019, 02:53 PM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by craig john View Post
there are some good guidelines in the link I posted previously summarizing Dr. Toole's book. I would encourage to read that entire website. It has the answers to most, or all of your questions.
Thanks. I'll take a look at it.
Drew Neilson is offline  
post #22 of 34 Old 08-27-2019, 04:08 PM - Thread Starter
Member
 
Drew Neilson's Avatar
 
Join Date: Nov 2013
Posts: 158
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 7
Quote:
Originally Posted by craig john View Post
Do you have a specific room or space in mind, or are you starting from scratch designing this room?
I'm trying to learn how to evaluate any given room's suitability for home theater, which will help me determine which room in my current house to put my home theater system, and also help me in the future find a new place to live that has a room that's good enough for home theater. I don't know if I've seen a housing search engine for rental or purchase properties that allows searchers to filter search results to only results that have a room suitable for home theater; probably not, unless it limits results to properties that have dedicated theaters.

The room that my system is currently in is very small: big enough that if it were a garage, a car would fit in it, and nothing else. It has a hardwood floor. The other room is my bedroom and is several times the first room's size and has a carpeted floor (I don't know what material is underneath the carpet) but the home theater would only exist in part of it, because that room contains my bed. I'm going to have to research the dispersion patterns of my speakers in order to find out how to best place them in this bigger, carpeted room--where to put the TV, front speakers, and side surround speakers.
Drew Neilson is offline  
post #23 of 34 Old 08-27-2019, 05:25 PM
Member
 
Join Date: Aug 2019
Posts: 27
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 2
Quote:
Originally Posted by Drew Neilson View Post
What are the characteristics of a hypothetical room designed for ideal acoustics? What are its dimensions? Is the floor hardwood, carpeted, or some other material? If it is hardwood (or otherwise reflective), where should rugs be placed, if at all? What types of furniture should be in the room, and what materials should they be made out of?
I've heard that a room with non-parallel walls are good?
Attached Thumbnails
Click image for larger version

Name:	Floor_Plan+(1).png
Views:	17
Size:	55.2 KB
ID:	2608060  
Ex JL Rep is offline  
post #24 of 34 Old 08-28-2019, 11:59 AM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Quote:
Originally Posted by Ex JL Rep View Post
I've heard that a room with non-parallel walls are good?
That's a myth. I have friend with a room like that. He paid a bunch of $$$ to have the room constructed with non-parallel walls. It still has room modes and standing waves. They're just not predictable with a room mode calculator.
sdurani likes this.

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System
craig john is offline  
post #25 of 34 Old 08-28-2019, 12:13 PM
AVS Forum Addicted Member
 
m. zillch's Avatar
 
Join Date: Oct 2006
Posts: 12,478
Mentioned: 45 Post(s)
Tagged: 0 Thread(s)
Quoted: 5094 Post(s)
Liked: 3711
Quote:
Originally Posted by Ex JL Rep View Post
I've heard that a room with non-parallel walls are good?
THX certified commercial theaters use non-parallel walls, said to help reduce standing waves.

Last edited by m. zillch; 08-28-2019 at 12:21 PM.
m. zillch is offline  
post #26 of 34 Old 08-28-2019, 12:48 PM
AVS Forum Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 11,721
Mentioned: 65 Post(s)
Tagged: 0 Thread(s)
Quoted: 1270 Post(s)
Liked: 1530
Quote:
Originally Posted by Drew Neilson View Post
I'm trying to learn how to evaluate any given room's suitability for home theater, which will help me determine which room in my current house to put my home theater system, and also help me in the future find a new place to live that has a room that's good enough for home theater. I don't know if I've seen a housing search engine for rental or purchase properties that allows searchers to filter search results to only results that have a room suitable for home theater; probably not, unless it limits results to properties that have dedicated theaters.
Here's the process I would go through when looking for a room into which I could install a Home Theater:

Before looking at ANY room, there are some general decisions to be made:

Video: How big a display is required? Is a flat panel, (OLED, QLED, LED, etc.), satisfactory or is a projection/screen system required.

Audio: What is the speaker/channel count required, 5 or 7 or 9? Is 3D audio, (Atmos, DST:X, Auro 3D), a consideration? How many subwoofers are required.

Type of Room: Will this be a dedicated Home Theater or Listening Room, or will it be a media system in a living/family room?

Once those questions are answered in a general sense, then the room layout necessary to accommodate those requirements becomes more clear. Walk into any room, and first look at the geometry. Is the room rectangular? If so, is there an optimal spot to place the display along one of the short walls? If there is no obvious place to place a display of the size required, start looking for another room.

If there is a good spot for the display, then look for possible speaker placements. Is there room around the display to accommodate the L/C/R speakers? (One aside... it is *ideal* to place the CC behind the display, but that requires an Acoustically Transparent screen and projector. If that's not a possibility, then look for space above or below the display for the CC.) An *ideal* room would allow symmetrical placement of the display and speakers, with all 3 front speakers aligned at the same height horizontally and with the tweeters all at ear height.

If the room has possibilities for the display and the front stage, then look at the seating locations. The sweet spot should be in front of the middle of the display and on-axis of the CC. Seating directly against a wall is to be avoided. Placing the seating at 1/3 or 2/3 of the long dimension of the room is usually best from an acoustic standpoint. Also consider all the non-sweet-spot seating and how important it is to provide multiple seats with near-optimal viewing/listening opportunities. Are rows of seats better than a more "conversational" seating arrangement?

Next, look at placements of the surrounds. Knowing the ideal locations for surround placement:



...see if the room can accommodate those placement, (no doors or windows where the speakers need to go.)

If 3D audio is a requirement, look at the ceiling to determine if it can accommodate ceiling speakers.

If the room can accommodate all the surround and ceiling speaker placements, next look at subwoofer placements. For an *ideal* theater, multiple subs are required. Placing one in the front of the room and one in back is good, and one on each wall is better.

If the room can accommodate all of those things, then look at the ability to place acoustic treatments. An *ideal* room would allow acoustic treatments at the primary reflection points and diffusion wherever that is required.

If you can find an *ideal* room that meets all those requirement, start looking for equipment to fill it up. Obviously, finding that *ideal* room is not easy. In fact, it's easier to construct a room from scratch than to try to modify an existing room. Also, it's far easier to accomplish the ideals in a dedicated room than in a more social room, like a family room or living room.

No matter what, prepare to compromise.
Quote:
Originally Posted by Drew Neilson View Post
The room that my system is currently in is very small: big enough that if it were a garage, a car would fit in it, and nothing else. It has a hardwood floor. The other room is my bedroom and is several times the first room's size and has a carpeted floor (I don't know what material is underneath the carpet) but the home theater would only exist in part of it, because that room contains my bed. I'm going to have to research the dispersion patterns of my speakers in order to find out how to best place them in this bigger, carpeted room--where to put the TV, front speakers, and side surround speakers.
Neither of those rooms sounds *ideal* but, with some compromise, they can both be made to work well.

Craig

Lombardi said it:
"Perfection is not attainable, but if we chase perfection we can catch excellence."

My System
craig john is offline  
post #27 of 34 Old 08-28-2019, 03:05 PM
AVS Forum Addicted Member
 
Alan P's Avatar
 
Join Date: Jan 2003
Location: South Dakota
Posts: 11,613
Mentioned: 106 Post(s)
Tagged: 0 Thread(s)
Quoted: 6282 Post(s)
Liked: 5614
I've read that a geodesic dome is the ideal room for audio. No personal experience...
Alan P is offline  
post #28 of 34 Old 08-28-2019, 03:16 PM
AVS Forum Addicted Member
 
sdurani's Avatar
 
Join Date: Oct 2001
Location: Monterey Park, CA
Posts: 27,838
Mentioned: 205 Post(s)
Tagged: 0 Thread(s)
Quoted: 7153 Post(s)
Liked: 6163
Dome will focus the sound in the middle, like parabolic dish does for antennas and microphones.

Sanjay
sdurani is offline  
post #29 of 34 Old 08-28-2019, 03:25 PM
AVS Forum Addicted Member
 
DonH50's Avatar
 
Join Date: Feb 2010
Location: Monument CO
Posts: 12,243
Mentioned: 67 Post(s)
Tagged: 0 Thread(s)
Quoted: 3218 Post(s)
Liked: 3262
Few basic points, sorry if brought up before:
  • Making the dimensions (H, W, L) relatively prime or using one of the "Golden Ratio" multipliers will prevent room modes from doubling (or tripling) up to help the bass a little.
  • Rectangular rooms are much easier to analyze and set up than ones with curves or slanted areas. Non-rectangular/perpendicular surfaces can either add or detract from the overall sound.
  • Isolation from the rest of the house will let you play loud without disturbing others and soft without them disturbing you. In my case that meant floating the walls and ceiling with Kinetics IsoMax clips and adding a minisplit HVAC unit so no ducting to the rest of the house. Mine is in the basement, concrete floor, so didn't bother to float the floor. I have the instructions I sent to my builder, somewhere...

FWIWFM - Don
sdurani likes this.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
DonH50 is offline  
post #30 of 34 Old 08-28-2019, 06:03 PM
AVS Forum Special Member
 
PrimeTime's Avatar
 
Join Date: Mar 2003
Location: Lower California
Posts: 3,247
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 800 Post(s)
Liked: 493
If we're talking about "ideal acoustics," one would start with an anechoic environment. Which is what your house was before you put up the floors, walls, ceilings and roof. (Dam helicopters!)

Ideally, one should start with the most anechoic/absorbent space you can possibly achieve. It is much easier/better to add acoustically reflective surfaces (and/or surround radiation) as desired than to try and reduce reflections by putting up a couple of protruding wall panels at the "first reflection points" and calling it optimized.

However, the conversation here seems to prioritize bass response. Which is unaffected by said wall panels and is at the mercy of the room size, geometry. construction and materials.
PrimeTime is offline  
Sponsored Links
Advertisement
 
Reply Audio Theory, Setup, and Chat

Tags
Acoustics , audio , room , room acoustics

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off