Concrete Block Home Theater - Good Idea ?

[vramak]

I've read in many websites that unpainted porous concrete block is a excellent sound absorber and also gives optimal reverb time. (Here's one such website - Room Acoustics: Basic Principles of Sound Absorption | )

So, I'm wondering if I should use exposed concrete block walls in the HT I'm building. I'm thinking about leaving the inner surface of the walls exposed and the outer surface plastered, so that external noise won't leak in. Do you think this is a good idea ? (I can find workarounds for the construction problems that such a structure will impose, so don't worry about that.)

By the way, the HT room will be in the stilt car park area and it will be 23.3x16x10 ft in size.

 

[GeorgeO]

I used solid blacks and plastered them in my basement. A couple of years later when I started work on HT, I used Anutone boards for sound absorption.

 

[vramak]

I used solid blacks and plastered them in my basement. A couple of years later when I started work on HT, I used Anutone boards for sound absorption.

Yes, installing acoustic panels is the most reliable way for acoustic treatment but I want to experiment with porous concrete blocks as this would (theoretically) substantially improve the acoustic quality of the room. Besides there's no reason not to use them.

I find that the sound absorption co-efficient for porous concrete blocks is 0.3 to 0.4 , whereas for fiberglass panels it's around 0.7 to 0.9. So I'm thinking of using walls made of these blocks and using acoustic panels only for first reflection points. I have to find out how effective such room treatment will be.

Please let me know if anyone thinks why such room treatment will be ineffective.

 

[Thad E Ginathom]

Unsealed concrete blocks are going to create dust, and that dust is going to be a very abrasive grit. How will audio equipment, especially the bits with moving parts, cope with that?

It could be sealed, of course, but then would the acoustic benefit be lost?

 

[Moviela]

A lot of theaters are made of precast concrete blocks. They are always painted to avoid problems with dust and moisture. When tuning the room with pink noise the best acoustic control materials are foam and drapery. Textiles covering foams are appealing to the eye and provide the control necessary. As for reverb, that is something that is desirable in a live performance venue, but for cinema consider that the "reverb" is mixed into the soundtrack and will be reproduced by the speakers. The room has just one reverb delay, but the sound engineer can change the delay depending on the size of the space being portrayed in the film.

 

[Thad E Ginathom]

I suppose a concert hall should not be dead, but reverb desirable? I want to hear the performance, not the echoes!

 

[vramak]

Unsealed concrete blocks are going to create dust, and that dust is going to be a very abrasive grit. How will audio equipment, especially the bits with moving parts, cope with that?

It could be sealed, of course, but then would the acoustic benefit be lost?

A lot of theaters are made of precast concrete blocks. They are always painted to avoid problems with dust and moisture. When tuning the room with pink noise the best acoustic control materials are foam and drapery. Textiles covering foams are appealing to the eye and provide the control necessary. As for reverb, that is something that is desirable in a live performance venue, but for cinema consider that the "reverb" is mixed into the soundtrack and will be reproduced by the speakers. The room has just one reverb delay, but the sound engineer can change the delay depending on the size of the space being portrayed in the film.

I'm not sure if everyone understands what I mean by 'porous concrete blocks'. The specific type I'm planning to use is called cellular lightweight block or foam concrete block. I know someone who makes these blocks and he is pretty sure that these blocks absorb sound well and can be left exposed. I have do more research about these blocks.

About reverb, I believe movie audio is mastered for rooms with a bit of reverb but I might be wrong. I did read somewhere that a slightly 'live' room is better for home theaters than a 'dead' room.

EDIT: Found a research paper about the acoustic properties of concrete blocks - https://engineering.purdue.edu/~concrete/weiss/publications/r_conference/RC-035.pdf - going by what the paper says, porus concrete blocks won't make a big acoustic difference for home theaters. I think I'll opt for usual acoustic treatment.