How to treat a concrete room.

[JapanDave]

The room is 20.1ft long X 16.4ft wide and 7.7ft high, all walls and ceiling are 10" concrete, the floor is 18" thick with one heavily soundproofed door.

I am carpeting the room and using an underlay of some sort, other than that I am not sure how I should approach this room. I understand that the base is what is going to give me problems and of coarse bass traps will be used but this is not going to solve everything.

I intend on treating the corners , but being that there is no where for the bass to escape I am at a loss. I was reading an article on here about bass traps, But it says not to use fiberglass-based traps for concrete structures, so what should I be doing get the acoustics sorted out in my room?


Any help would be appreciated.

 

[Audioholics]

That room is going to kick BUTT! You just have to tame it, but pressurization shouldn't be a problem. Lots of 4" panels and diffusion where possible. If you can put some thinner binary diffusers on the ceiling at the reflection point between you and the front speakers that would help immensely.

 

[lsiberian]

The room is 20.1ft long X 16.4ft wide and 7.7ft high, all walls and ceiling are 10" concrete, the floor is 18" thick with one heavily soundproofed door.

I am carpeting the room and using an underlay of some sort, other than that I am not sure how I should approach this room. I understand that the base is what is going to give me problems and of coarse bass traps will be used but this is not going to solve everything.

I intend on treating the corners , but being that there is no where for the bass to escape I am at a loss. I was reading an article on here about bass traps, But it says not to use fiberglass-based traps for concrete structures, so what should I be doing get the acoustics sorted out in my room?


Any help would be appreciated.

I suggest you at least call up GIK acoustics they have nice packages and could probably help you get it done right.

 

[jostenmeat]

The room is 20.1ft long X 16.4ft wide and 7.7ft high, all walls and ceiling are 10" concrete, the floor is 18" thick with one heavily soundproofed door.

I am carpeting the room and using an underlay of some sort, other than that I am not sure how I should approach this room. I understand that the base is what is going to give me problems and of coarse bass traps will be used but this is not going to solve everything.

I intend on treating the corners , but being that there is no where for the bass to escape I am at a loss. I was reading an article on here about bass traps, But it says not to use fiberglass-based traps for concrete structures, so what should I be doing get the acoustics sorted out in my room?


Any help would be appreciated.

I immediately recognized your handle, from AVS, so I looked, and it seems you've already been given good advice in both the threads you started in the dedicated build subforum.

Where the heck did you read fiberglass is no good for concrete? (I mean, traps are wrapped in fabric anyhow).

Just remember it is virtually impossible to go overkill with bass trapping.

Have you settled on a PJ choice yet? Have you had much contact with Sherardp (as he's a member here, and I can see he's given you advice too, out there in Japan).

 

[DD66000]

You'll need more than just bass traps. The highs will be bouncing all over the place. Those walls are going to need quite a few wall panels to suck up the reflections.

As for the types of panels I would use recycled denim panels. much more environmently friendly.

 

[JapanDave]

That room is going to kick BUTT! You just have to tame it, but pressurization shouldn't be a problem. Lots of 4" panels and diffusion where possible. If you can put some thinner binary diffusers on the ceiling at the reflection point between you and the front speakers that would help immensely.

Thanks, that is something I no idea on in regards to the binary diffusers on the ceiling. Is there a way to measure where that point will be?

I immediately recognized your handle, from AVS, so I looked, and it seems you've already been given good advice in both the threads you started in the dedicated build subforum.

Where the heck did you read fiberglass is no good for concrete? (I mean, traps are wrapped in fabric anyhow).

Just remember it is virtually impossible to go overkill with bass trapping.

Have you settled on a PJ choice yet? Have you had much contact with Sherardp (as he's a member here, and I can see he's given you advice too, out there in Japan).

Yes I did, but I didn't know there was an internet rule that you could only post a question on one website? I certainly did get some good advise from one kind person , but I am still looking for more answers. This is the thread, if everything is covered for room accoustics in this thread I will appologise. h t t p ://w w w.avsforum.com/avs-vb/showthread.php?t=1185613&highlight=

I got the fibre glass is undesirable on this site, in this article and it raised some more concerns for me. (I can't post links yet) h t t p: / /w w w.audioholics.com/education/acoustics-principles/bass-traps-not-just-for-fisherman

It's difficult to get substantial absorption below about 80 Hz using a fiberglass-based trap. Fortunately, as explained earlier, most rooms don't need much absorption below 80 Hz because sheet rock walls pass and absorb those very low frequencies. So unless you have walls made of cement or block, or have two layers of sheet rock for increased isolation between rooms, fiberglass bass traps are an ideal choice.

How am I supposed to take this?

I am getting a JVC PJ Probably the 550 or the new version of the 750. I talked to Sherardp mainly about screens and PJ's, but his house is completely different to mine in the way it is built, unfortunately.

You'll need more than just bass traps. The highs will be bouncing all over the place. Those walls are going to need quite a few wall panels to suck up the reflections.

As for the types of panels I would use recycled denim panels. much more environmently friendly.

Thanks for the advise.

@ lsiberian unfortunately I am Japan.

 

[Audioholics]

Thanks, that is something I no idea on in regards to the binary diffusers on the ceiling. Is there a way to measure where that point will be?

You can use trig, or have someone hold a mirror up on the ceiling. When you see the front speakers you're at the center point. Cover an area about 4'x8' if possible.

 

[AVRat]

Mike C did a similar bunker setup in Manila: http://forums.audioholics.com/forums/showthread.php?t=30439

Many people completely cover the Front stage out about 4-6' with 4-6" of the 703 to deaden the front end. They also create soffit style bass trapping around the upper corners of the room.

 

[jostenmeat]

Yes I did, but I didn't know there was an internet rule that you could only post a question on one website?

I never said that. My intention was to encourage you to listen to what's been offered (in case you were dissatisfied and/or were not sure if the information given was good). For, IMO, you are most likely not going to find better answers here. Sure, might as well ask, but my answer, again, was simply giving a +1 to what's been advised.

I certainly did get some good advise from one kind person , but I am still looking for more answers. This is the thread, if everything is covered for room accoustics in this thread I will appologise. h t t p ://w w w.avsforum.com/avs-vb/showthread.php?t=1185613&highlight=

I got the fibre glass is undesirable on this site, in this article and it raised some more concerns for me. (I can't post links yet) h t t p: / /w w w.audioholics.com/education/acoustics-principles/bass-traps-not-just-for-fisherman

How am I supposed to take this?

That is very interesting, thank you very much for that insight. I'd ask the author of that article directly, and he's a regular at the Acoustic theory subforum at AVS. Or just email directly, via Real Traps. If you look at his own site for comparative product data, yes there is reduced effectiveness below 80hz, but it still absorbs.
http://www.realtraps.com/data.htm

Now these are just rectangular panels, but if you do the super chunk traps as Kal Rubinson advised you, you will have much better effectiveness at absorbing the low frequencies. (Think "thickness" or "mass" for absorbing bass). On one hand, front corners are a bang for buck location in terms of bass trapping, but I'd like to repeat it's virtually impossible to go overkill with trapping. So if you can only do two corners, the front two are it, but I think you are going to be able to do more, so if you see a corner, trap it.

OTOH, the deadened front wall is popular with HT enthusiasts, but it's NOT the priority bang for buck spot, for it's not a first reflection point (like with sidewalls/ceiling/backwall outside of using dipole/omnipoles), but if you can go for it. Ethan Winer will tell you the exact same thing.

I am getting a JVC PJ Probably the 550 or the new version of the 750. I talked to Sherardp mainly about screens and PJ's, but his house is completely different to mine in the way it is built, unfortunately.

Are you still thinking ballpark of 150" screen? I'm not sure it's going to be bright enough with these PJs, unless you use a retroreflective screen. I'm sure you've been told that already, and I haven't checked in on those subforums too recently. Good luck!

 

[JapanDave]

I never said that. My intention was to encourage you to listen to what's been offered (in case you were dissatisfied and/or were not sure if the information given was good). For, IMO, you are most likely not going to find better answers here. Sure, might as well ask, but my answer, again, was simply giving a +1 to what's been advised.



That is very interesting, thank you very much for that insight. I'd ask the author of that article directly, and he's a regular at the Acoustic theory subforum at AVS. Or just email directly, via Real Traps. If you look at his own site for comparative product data, yes there is reduced effectiveness below 80hz, but it still absorbs.


Now these are just rectangular panels, but if you do the super chunk traps as Kal Rubinson advised you, you will have much better effectiveness at absorbing the low frequencies. (Think "thickness" or "mass" for absorbing bass). On one hand, front corners are a bang for buck location in terms of bass trapping, but I'd like to repeat it's virtually impossible to go overkill with trapping. So if you can only do two corners, the front two are it, but I think you are going to be able to do more, so if you see a corner, trap it.

OTOH, the deadened front wall is popular with HT enthusiasts, but it's NOT the priority bang for buck spot, for it's not a first reflection point (like with sidewalls/ceiling/backwall outside of using dipole/omnipoles), but if you can go for it. Ethan Winer will tell you the exact same thing.



Are you still thinking ballpark of 150" screen? I'm not sure it's going to be bright enough with these PJs, unless you use a retroreflective screen. I'm sure you've been told that already, and I haven't checked in on those subforums too recently. Good luck!

It was the article that prompted me to post here, as I was all set to go with superchunks and treat the front wall with fiberglass panels when I read the article. It just got me concerned again.

I might just give Real Traps an e-mail and see what they have to say.

As for the screen, I currently have my A-Lens with JVC Japan, the engineers over there are testing the lens with brightness, throw range ect, ect . Obviously this is the best way to see what size screen the PJ's will handle as they are the ones who designed the PJ. I have had some contact the other day and they said that 140" is deffinately ok and are now testing if a 150" screen will work or not as that is what I really do want.

Thanks for the advise.

 

[highfigh]

I got the fibre glass is undesirable on this site, in this article and it raised some more concerns for me. (I can't post links yet) h t t p: / /w w w.audioholics.com/education/acoustics-principles/bass-traps-not-just-for-fisherman

I would contact Ethan Winer to find out why he wrote the comment about fiberglass not working over concrete block. It may have to do with the cavities in each block but if yours have been filled, this wouldn't apply. If you don't want to see the concrete walls when the room is done, you could build wood framed walls over them, using drywall on the faces and insulating behind. Then, you won't have any issues from the concrete walls because it'll be an additional barrier. Doubling the drywall where the low frequency energy is strongest will keep resonances to a minimum. Then, fiberglass baffles will minimize the other problems.

 

[JapanDave]

I would contact Ethan Winer to find out why he wrote the comment about fiberglass not working over concrete block. It may have to do with the cavities in each block but if yours have been filled, this wouldn't apply. If you don't want to see the concrete walls when the room is done, you could build wood framed walls over them, using drywall on the faces and insulating behind. Then, you won't have any issues from the concrete walls because it'll be an additional barrier. Doubling the drywall where the low frequency energy is strongest will keep resonances to a minimum. Then, fiberglass baffles will minimize the other problems.

I will contact him through an e-mail and see what he has to say.

I have thought of that and I am going to speak with the contrator ASAP.

Thanks for the advise guys.

 

[JapanDave]

I would contact Ethan Winer to find out why he wrote the comment about fiberglass not working over concrete block. It may have to do with the cavities in each block but if yours have been filled, this wouldn't apply. If you don't want to see the concrete walls when the room is done, you could build wood framed walls over them, using drywall on the faces and insulating behind. Then, you won't have any issues from the concrete walls because it'll be an additional barrier. Doubling the drywall where the low frequency energy is strongest will keep resonances to a minimum. Then, fiberglass baffles will minimize the other problems.

Thank you very much for your help. I would too like to know why he said that. I am planing on using some sort of drywall setup with fiber glass insulation. I also plan to use superchunks and bass traps where possible.

 

[DD66000]

Thank you very much for your help. I would too like to know why he said that. I am planing on using some sort of drywall setup with fiber glass insulation. I also plan to use superchunks and bass traps where possible.

If you're going to install framed/insulated/sheetrock walls inside the block walls, then there is no problem. The furred out walls still act as any normal drywall room, plus the added benefit of the concrete walls keeping in the sound.

 

[highfigh]

If you're going to install framed/insulated/sheetrock walls inside the block walls, then there is no problem. The furred out walls still act as any normal drywall room, plus the added benefit of the concrete walls keeping in the sound.

Bass traps are still needed, though. Concrete doesn't let low frequencies through the way drywall does.

Drums and bass are hard to stop if any openings to the outside exist. Everything above that region makes the air resonate but bass exerts much more energy.

 

[DD66000]

Bass traps are still needed, though. Concrete doesn't let low frequencies through the way drywall does.

Drums and bass are hard to stop if any openings to the outside exist. Everything above that region makes the air resonate but bass exerts much more energy.

I believe I said that concrete holds in the sound better than a framed wall. What part of that don't you agree with?
I never said anything about bass traps not needed. But if there is an insulated wall inside the concrete you don't get the high frequencies bouncing around as much as if its just bare concrete walls.

 

[highfigh]

I believe I said that concrete holds in the sound better than a framed wall. What part of that don't you agree with?
I never said anything about bass traps not needed. But if there is an insulated wall inside the concrete you don't get the high frequencies bouncing around as much as if its just bare concrete walls.

You're right- I didn't see that, for some reason. Sorry.

 

[mtrycrafts]

You're right- I didn't see that, for some reason. Sorry.

Another example of our senses doing their own things fooling us.

 

[DD66000]

Another example of our senses doing their own things fooling us.

Yeah, like proof reading a post before submitting a reply, and still have a spelling error.

 

[highfigh]

Yeah, like proof reading a post before submitting a reply, and still have a spelling error.

If this is aimed at me, show the error.