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Discussion Starter #1
My room is bare wall apart from blackout curtains almost all the way along 1 side of the room where the windows are. The walls are plasterboard with brick underneath (I think :scratch:). The ceiling is plasterboard and the floor is carpeted.

I do have slap echo in the room but in general I love the sound from my system. So how do I know whether it will be worth putting accoustic panels and bass traps up?

Do I just put a couple of panels up at the first reflection point and that is it, just enough to maybe get rid of the slap echo, or do I go for broke and put bass traps in the 4 corners of the room, absorbant panels around the front 3rd of the room, absorb/diffuse combi panels along the bare side wall and diffusers on the rear wall and diffusers on the ceiling.

In general do you just treat where necessary or can you fill the room with treatment like I suggested above and assume that would give you the best balance of sound overall. I like to keep things as simple as possible (so my simple brain can deal with things better :rolleyesno:) so I would prefer, if possible, a straight instruction as opposed to, put one panel up see how that sounds, put another one up, see how that sounds etc etc.

I am on a tight budget so I would rather know exactly what I need to put up, if I even need to put any up at all. I have spent a lot of time with REW trying to get the best out my sub, I found that quite a draining process so if there is simple way of achieving good quality sound that I will notice a big difference from the good sound I am hearing now, without measuring all the time that would be great.

I would really appreciate your advice :help:

Kind Regards
Marty
 

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I would prefer, if possible, a straight instruction as opposed to, put one panel up see how that sounds
You may get generalized advice on which type of room treatments can help with the echo, but I don't expect you to get the specific answer you want with so little information given. Room treatments vary considerably based on the frequency range of the problem you wish to correct. You could examine the waterfall graphs you have and determine which frequencies have the biggest decay problems.

I don't have personal experience solving that particular problem, but I'm guessing it involves the higher frequencies well above the sub range and will require broadband treatments. knowing if you are using a measurement microphone or a sound level meter to obtain measurements would indicate how useful your full range measurements could be. Since your room is apparently non-symmetrical, you might consider posting a layout drawing with measurements so people have an idea on what your dealing with. An acceptable budget and WAF factors which must be adhered to might help people give you more helpful suggestions as well.

Matt
 

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Discussion Starter #3
I have put a 360 of my room although the rear bipole speakers behind the couch are now further apart and closer to the corners:

front room 1.jpg

front room 2.jpg

front room 3.jpg

front room 4.jpg

front room 5.jpg
 

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Broadband bass absorption floor to ceiling in the 2 front corners. I'd also do some in the shorter left rear corner.

I would add at least 2-3 2" 2'x4' absorption panels on the left wall to bring better left to right symmetry by matching better with the curtains on the other side.

Ideally, the front wall would also be 100% dead to help with boundary interactions and to prevent reflections from the surround channels contaminating the front soundstage.

Bryan
 

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Discussion Starter #5
Broadband bass absorption floor to ceiling in the 2 front corners. I'd also do some in the shorter left rear corner.

I would add at least 2-3 2" 2'x4' absorption panels on the left wall to bring better left to right symmetry by matching better with the curtains on the other side.

Ideally, the front wall would also be 100% dead to help with boundary interactions and to prevent reflections from the surround channels contaminating the front soundstage.

Bryan
So do you mean put absorbant panels all around the screen?

Also would anything be needed for the back wall, as these 2 speakers are bipoles they need to rely on the reflective surfaces?

Will all of this be a massive improvement to the sound?

Will I have to move my sub again once putting bass traps in as I have a pretty good response at the moment and it will be a pain to start over again?

Thanks
Marty
 

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If you've played with sub position to get the best response, the chances of having to move it a lot more are pretty slim. Maybe some slight improvements to be had with slight movements but nothing that you'd have to do right away certainly - or possibly not at all.

Yes - ideally, the front wall would be 100% covered with absorbing material.

Rear wall - not so much other than potentially some membrane type absorbers if you have problems with cancellations in the bass off of the rear wall. Those types will still allow the surround field to sound lively.

Bryan
 

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Discussion Starter #7
If you've played with sub position to get the best response, the chances of having to move it a lot more are pretty slim. Maybe some slight improvements to be had with slight movements but nothing that you'd have to do right away certainly - or possibly not at all.

Yes - ideally, the front wall would be 100% covered with absorbing material.

Rear wall - not so much other than potentially some membrane type absorbers if you have problems with cancellations in the bass off of the rear wall. Those types will still allow the surround field to sound lively.

Bryan
Thanks Bryan

How do I tell if I have bass cancellations with the bass from the rear wall?

The membrane type absorbers, where would they go, if you look at rear speakers and then imagine that they are now both further apart, about 1.5 feet from each side wall, these speakers are bipoles so would the membrane absorbers reflect the sound like bipoles are supposed to?

Kind Regards
Marty
 

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All I'm looking for in the back is something that will absorb bass but not as much in the upper mids and highs to preserve the surround field.

If you move your mic forward or backward from the seating position, do you notice any nulls going away or changing in frequency? If either, then you have potential rear wall problems.

Bryan
 

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Discussion Starter #9
All I'm looking for in the back is something that will absorb bass but not as much in the upper mids and highs to preserve the surround field.

If you move your mic forward or backward from the seating position, do you notice any nulls going away or changing in frequency? If either, then you have potential rear wall problems.

Bryan
I did notice that there was a dip around 35-40hz that got steeper as I moved further away from the rear wall, about 2 feet from the rear wall seemed better. I still have to try out rew v5 properly, I tried it the other day and the results were different to what I got in version 4 so I still dont know how to use v5?

Thanks
Marty
 

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Probably just a change in mic position. Or, could be you have smoothing set differently.

Bryan
 

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Discussion Starter #11
Probably just a change in mic position. Or, could be you have smoothing set differently.

Bryan
Does this null mean I have rear wall bass problems?

How do I absorb the front wall, I wouldn't be able to put much above the screen as there is only about 5 inches from the top of it to the ceiling, I do not know how to remove the screen as it fixed and was proffesionally installed, are you just talking about surrounding the screen with something?

If my subs response is pretty good why would I need bass traps in the 4 corners, what difference would it make to the sound? Would the untrained ear notice a difference?

Thanks Again
Marty
 

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Do as much as you can on the front wall given the restrictions.

If you have a changing null based on seating position front to back, it can be helped with rear wall treatment coupled with good positioning.

For the other absorbers, remember that there is much more than just frequency response in play here. I can have perfectly flat response and excessive ringing and decay times that will muddy up sound, cause dialog intelligibility problems, cause loss of imaging cues and harmonic details, etc.

Bryan
 

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Discussion Starter #13
Do as much as you can on the front wall given the restrictions.

If you have a changing null based on seating position front to back, it can be helped with rear wall treatment coupled with good positioning.

For the other absorbers, remember that there is much more than just frequency response in play here. I can have perfectly flat response and excessive ringing and decay times that will muddy up sound, cause dialog intelligibility problems, cause loss of imaging cues and harmonic details, etc.

Bryan
Thanks Bryan :T

So what you are saying is the bass traps will make the sound better to the ear but not necessarily visible through REW?

Regards
Marty
 

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It will make it better in REW if you look at the decay time or waterfall windows as opposed to just the measured frequency response.

Bryan
 

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Discussion Starter #15
It will make it better in REW if you look at the decay time or waterfall windows as opposed to just the measured frequency response.

Bryan
Interesting, I wouldn't have the first idea on what to look at on those sceens :huh:

In regards to the front wall again, I saw a thread where a guy put a couple of corner shelves up and placed triangular cut slices of rockwool on top of eachother all the way up the wall. Is this the correct way of making a corner bass trap because I was under the impression that you need to leave a bit of air space between the rookwool and the corner?

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Marty
 

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It's one way to do it and will work just fine.

The air gap is a common misconception. It's not the space, it's getting the leading edge of the absorber out farther from the hard boundary that helps extend performance. That said, any time you can have a solid chunk rather than a thinner chunk with an air gap (think 6" flat on a wall vs 4" with 2" of air), the solid piece will perform better. Same goes for flat panels straddling a corner vs solid triangular chunks.

Waterfalls are an easy graphical representation of how fast sound decays across the frequency spectrum. Bottom axis is frequency. Left axis is intensity (db level). Z axis (depth) shows time in milliseconds. The proper decay time varies by each room in terms of size and what you'll use the room for. Classrooms are different from churches from home theaters from listening rooms, etc.


Bryan
 

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Discussion Starter #17
It's one way to do it and will work just fine.

The air gap is a common misconception. It's not the space, it's getting the leading edge of the absorber out farther from the hard boundary that helps extend performance. That said, any time you can have a solid chunk rather than a thinner chunk with an air gap (think 6" flat on a wall vs 4" with 2" of air), the solid piece will perform better. Same goes for flat panels straddling a corner vs solid triangular chunks.

Waterfalls are an easy graphical representation of how fast sound decays across the frequency spectrum. Bottom axis is frequency. Left axis is intensity (db level). Z axis (depth) shows time in milliseconds. The proper decay time varies by each room in terms of size and what you'll use the room for. Classrooms are different from churches from home theaters from listening rooms, etc.


Bryan
I understood it that the sound travels through the absorber reflects off the wall behind and then gets absorbed again?

What decay time would I be aiming for in a home cinema then? Would it be the same db level across all frequencies?

Thanks
Marty
 

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True on the reflection - but - with a solid piece, it's doing the same thing but never leaving the absorbing material.

What are the room dimensions? That's part of the calculation.

The decay times will be a downward sloping curve which is somewhat flat in the middle with the low end being a bit higher and the high end being a bit shorter.

Bryan
 

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Discussion Starter #19
True on the reflection - but - with a solid piece, it's doing the same thing but never leaving the absorbing material.

What are the room dimensions? That's part of the calculation.

The decay times will be a downward sloping curve which is somewhat flat in the middle with the low end being a bit higher and the high end being a bit shorter.

Bryan
My room is 18ft 6inchesx12ft 11inches and 8.5ft high
 

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From an RT60 standpoint (really more for larger rooms but OK for reference), you'd want to be around 200ms in the midrange - maybe 250 in the lows and 160-170ms in the high end. You're really more interested in RT30 which is a bit more than 1/2 of those times but most people don't like it that dead.

Untreated, the low end is now probably closer to 1 second or a bit more.

Bryan
 
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