Impact of room on speaker sound?

[haraldo]

Bass traps only work on frequencies above 100htz. No affect at all in low bass.

I don't quite agree on this

If you look at measured characteristics of some professional bass traps they have very very good effect way down into the bass, but as a result of physics, if you want bass traps that are efficient in the lower bass, they must be BIG... like VERY BIG

Check for instance thee products, very powerful even at low bass, but not cheap
http://www.rpginc.com/products/modexcorner/index.htm
http://www.rpginc.com/products/modexcorner/modc_imp.htm

http://www.rpginc.com/products/modexbroadband/Modex-Broadband.pdf


Many of the products like bass busters and the likes from echobusters have very little effect in the lower bass, simply because they're not large enough

I have made a room mode calculator that shows frequencies of standing waves in a room, but this only really works for rectangular rooms, enter room dimensions in feet and it will show distribution of the different standing waves. This is from a model presented in the master handbook of acoustics.

Where you have X's in the columns besides room modes, the modes are very close to each other and may need particular attention. I have added dimensions for a sample room.

 

[fmw]

fmw, Did you post here or on another site? Are there any key words I can use in a search that will be more likely to pull up those posts?

Maybe you could do an article for audioholics.

I'll go as quickly as I can. We did a bias controlled listening test in my home in 1998. Room A was a 12' X 12' bedroom with terrible acoustics Room B was a 26' X16' bedroom with very good acoustics. In the larger room we could place the speakers about midway leaving lots of room behind them and between them and the listening position. The small room had the speakers placed near a wall. In the small room we used a pair of B&W Matrix 802 speakers which had a list price of around $8000 at the time. In the larger room we put a Sub Sat 6 system from Boston Acoustics which has a pair of very small boxes with an 8" subwoofer. Its list price was about $700 at the time.

The group was 10 audiophiles. Normally, we don't actually blindfold people to do blind listening tests but we did for this test. Each tester was taken to each room blindfolded and we played 2 minutes worth of well recorded music in each room. The audiophiles were told there was an expensive pair of speakers in one room and a modestly priced pair in the other. After hearing the music in each room, the testers were asked to id the expensive pair - room A or room B. We ran the test twice for each listener. We changed the music on each pass and changed which room they heard first on each pass. So we had 20 iterations of the test. 7 of the listeners (14 of 20 id's in all) were incorrect. They thought the Boston Acoustics speakers were the more expensive pair.

Our conclusion was that they were actually voting for the room with the better acoustics. Better speakers in an acoustically poor room couldn't make up the difference. That's the basics of the test we ran.

 

[DD66000]

I'll go as quickly as I can. We did a bias controlled listening test in my home in 1998. Room A was a 12' X 12' bedroom with terrible acoustics Room B was a 26' X16' bedroom with very good acoustics. In the larger room we could place the speakers about midway leaving lots of room behind them and between them and the listening position. The small room had the speakers placed near a wall. In the small room we used a pair of B&W Matrix 802 speakers which had a list price of around $8000 at the time. In the larger room we put a Sub Sat 6 system from Boston Acoustics which has a pair of very small boxes with an 8" subwoofer. Its list price was about $700 at the time.


Our conclusion was that they were actually voting for the room with the better acoustics. Better speakers in an acoustically poor room couldn't make up the difference. That's the basics of the test we ran.

Its a given a square room, at probably any size, will always be less than good, no matter what speakers you use. So why is that a surprise?

And any quality system, setup wrong, will not sound as good as it should and that means being too close to walls, unless the speakers were designed as onwall/inwall.

But put the two systems in the same room and do a blind test, as they do at Harman's Northridge testing rooms and then it a whole different thing.

 

[haraldo]

Its a given a square room, at probably any size, will always be less than good, no matter what speakers you use. So why is that a surprise?

And any quality system, setup wrong, will not sound as good as it should and that means being too close to walls, unless the speakers were designed as onwall/inwall.

But put the two systems in the same room and do a blind test, as they do at Harman's Northridge testing rooms and then it a whole different thing.

fmw shows a point that room acoustics is more important than probably anything else that you may put into your system, that's not a surprise if you know a few things about acoustics, but still important to write about.

 

[DD66000]

fmw shows a point that room acoustics is more important than probably anything else that you may put into your system, that's not a surprise if you know a few things about acoustics, but still important to write about.

Some rooms will be better than others, but even many bad rooms, can be made to sound fairly good, if you can give the speakers some space, and if needed, laid out diagonally across the room. And if needed add some wall treatments at the first reflection points for really narrow rooms.

The big problem is even with the popularity of HT, many houses don't have even one room that could be considered good from a stand point of sound reproduction: too many windows, large rock fireplaces, too many openings to the room, L shaped. Add to that in-wall/ceiling speaker installs that are poorly thought out, using ceiling speakers for the LCRs.

The constractors just stick their HT option in a L shaped great room, wide open to the majority of the house, with the area for the TV laid out off center from the built-in speaker system. Over the last four years I've seen about every kind of crap room setup you can think of. And it doesn't have to be that way, just a bit of thought by the Architect.

 

[highfigh]

I don't quite agree on this

If you look at measured characteristics of some professional bass traps they have very very good effect way down into the bass, but as a result of physics, if you want bass traps that are efficient in the lower bass, they must be BIG... like VERY BIG

Check for instance thee products, very powerful even at low bass, but not cheap
http://www.rpginc.com/products/modexcorner/index.htm
http://www.rpginc.com/products/modexcorner/modc_imp.htm

http://www.rpginc.com/products/modexbroadband/Modex-Broadband.pdf


Many of the products like bass busters and the likes from echobusters have very little effect in the lower bass, simply because they're not large enough

I have made a room mode calculator that shows frequencies of standing waves in a room, but this only really works for rectangular rooms, enter room dimensions in feet and it will show distribution of the different standing waves. This is from a model presented in the master handbook of acoustics.

Where you have X's in the columns besides room modes, the modes are very close to each other and may need particular attention. I have added dimensions for a sample room.

Harald- did you see the link I posted? That one does two wall modes, tangential and all six walls. I have an Excel sheet that does the first set but hadn't seen the link until last night.

 

[fredk]

Thanks for the reply fmw. Thats a lot of effort for a few audio enthusiast to go through to satisfy curiosity.

 

[highfigh]

I'll go as quickly as I can. We did a bias controlled listening test in my home in 1998. Room A was a 12' X 12' bedroom with terrible acoustics Room B was a 26' X16' bedroom with very good acoustics. In the larger room we could place the speakers about midway leaving lots of room behind them and between them and the listening position. The small room had the speakers placed near a wall. In the small room we used a pair of B&W Matrix 802 speakers which had a list price of around $8000 at the time. In the larger room we put a Sub Sat 6 system from Boston Acoustics which has a pair of very small boxes with an 8" subwoofer. Its list price was about $700 at the time.

The group was 10 audiophiles. Normally, we don't actually blindfold people to do blind listening tests but we did for this test. Each tester was taken to each room blindfolded and we played 2 minutes worth of well recorded music in each room. The audiophiles were told there was an expensive pair of speakers in one room and a modestly priced pair in the other. After hearing the music in each room, the testers were asked to id the expensive pair - room A or room B. We ran the test twice for each listener. We changed the music on each pass and changed which room they heard first on each pass. So we had 20 iterations of the test. 7 of the listeners (14 of 20 id's in all) were incorrect. They thought the Boston Acoustics speakers were the more expensive pair.

Our conclusion was that they were actually voting for the room with the better acoustics. Better speakers in an acoustically poor room couldn't make up the difference. That's the basics of the test we ran.

By any chance, did that larger room have a 10' ceiling? If it did, the proportions almost exactly match the Golden Ratio.

Too bad you couldn't have used the same speakers in both rooms. That would have been interesting, especially if the listeners had no idea what kind were being used.

 

[haraldo]

Harald- did you see the link I posted? That one does two wall modes, tangential and all six walls. I have an Excel sheet that does the first set but hadn't seen the link until last night.

Yes, nice I saw the link after I did my post, thanks

I believe that probably even the most unlistenable rooms can be made quite good, with simple means, if you're able to tame the worst modes and to some extent control first reflections, you could possibly be making significant progress,

Can you post (or send me) the excel sheet?

 

[fmw]

By any chance, did that larger room have a 10' ceiling? If it did, the proportions almost exactly match the Golden Ratio.

Too bad you couldn't have used the same speakers in both rooms. That would have been interesting, especially if the listeners had no idea what kind were being used.

No my house has 8' ceilings. What makes the long bedroom so good acoustically is the ability to place the speakers well. Speakers do poorly when backed up against a wall. They need breathing room.

We could have done a test with both pairs of speakers in the same room but we didn't think it would tell us anything. We were testing the rooms, really and the concept of room acoustics trumping equipment. We simply assumed that, in the same room, people would have picked the B&W as the more expensive speaker pair. While we didn't test it, I still think it is a safe assumption. The 802's are fairly short on flaws while the Sub-Sat 6 has plenty of them. Incidentally, I still use the Sub Sat 6 system with my bedroom TV. Same bedroom, too. It is our master bedroom.

 

[highfigh]

No my house has 8' ceilings. What makes the long bedroom so good acoustically is the ability to place the speakers well. Speakers do poorly when backed up against a wall. They need breathing room.

We could have done a test with both pairs of speakers in the same room but we didn't think it would tell us anything. We were testing the rooms, really and the concept of room acoustics trumping equipment. We simply assumed that, in the same room, people would have picked the B&W as the more expensive speaker pair. While we didn't test it, I still think it is a safe assumption. The 802's are fairly short on flaws while the Sub-Sat 6 has plenty of them. Incidentally, I still use the Sub Sat 6 system with my bedroom TV. Same bedroom, too. It is our master bedroom.

Having the proportions for the length of two walls close to the Golden Ratio makes a big difference. I have installed many systems in different sized rooms and can't remember a square one sounding good, but with a little time spent in speaker placement, I also can't remember the rectangular ones sounding bad unless the acoustical properties of the materials just weren't conducive to good sound. Those ratios not only look better, they sound better.

 

[DD66000]

Any rectangular room can sound very good, unless the dimensions are multiples (8'x 16'x 24')
And you don't stick the speakers in the corners, because of having a screen too wide for the room's width.
The closer you can get the main L/R speaker locations set to 27.6 % of the room width from the side walls the better. And that will result in your hearing to reject the first reflective signal, as it will get to the seat well after the direct signal.

But if you have to use a square room, it would be much better to setup the speakers diagonally across the corners, so they're 45* to the walls.