Building Great Bass Response In your Home Theater

[admin]

If you are searching for the utmost listening experience in your room with your system it is time you consider how your space is constructed. It is the purpose of this article to show you how the construction relates to your audio experience. There is an inverse relation between sound isolation (STC) and sound absorption (NRC). The greater the isolation of a surface the more sound energy is going to remain in that space. This applies directly below 200 Hz where the resonance of room modes is a primary factor of your systems character. It becomes compounded when you add multiple sound sources with low frequency information…you got it, your room.

Discuss "Building Great Bass Response In your Home Theater" here. Read the article.

 

[KC23]

Wish this was put together for non-audio geek speak types like me. I really had a hard time getting anything useful from it, but it was probably me.

 

[Davemcc]

I like this,

"If you are looking for the type of bass response that drops effortlessly from guitars to bass to kick drum…from orchestral score to rampaging sound effects you should consider construction as a this year’s system improvement."

Well I can dream, can't I?

 

[birdonthebeach]

Well I can dream, can't I?

I know the feeling - but one day, you may look up and realize you are about to build a house or remodel, etc., and suddenly having this info is a very good thing! I have always clipped or printed out articles like this and saved them for that one day..... which is now gonna happen. Start a notebook or a file, and dream BIG!

 

[Jeff Hedback]

I thought I would reply to KC23 in non-audio speak (hopefully).

The low frequency response is simply how tight and accurate your bass sounds.

Low frequencies act a lot like big ocean waves. If you are to get truly great audio you need to address and control them. Construction is one way to address and control low frequencies.

The THX standard is tough to achieve, but even a simple material change like the Audioholics Reference System 1 example can really help (subfloor material).

If you can not do anything, just thinking this way may help you know some of the limitations of your system (room, speakers, components, furnishings and you).

Hope that may help.

Thanks for the repsonse.

 

[MDS]

I thought the article was very informative although I won't personally be able to use the construcion ideas as the house is relatively new and won't be undergoing any remodeling anytime soon.

Please correct me if I am wrong but what I got out of the article is:

1. To keep sound IN, you want a high STC number. Higher STC numbers result in higher transmission loss (TL) which means more of the sound is attenuated at the wall boundaries and does not go through the wall (as much) to adjacent structures.

2. To keep sound OUT (or reduce sound contributed by the room itself), you want absortion panels with a high NRC.

Sound right? As the article said isolation and absorbtion are inversely related so you choose the right materials/construction techniques for the problem you are trying to address (although it is anything but simple).

I am trying to reduce the noise from my HVAC enclosure so I chose sound dampening sheets and foam absorption tiles. I think I am on the right track as my goal is to reduce sound in that area.

 

[Jeff Hedback]

Close...NRC is a rating for materials that control reflections within a space (like absorption panels). And in your case, it is usually the right approach with HVAC issues. Internally absorbed ducts, etc.

There is an article on this HVAC topic just a week or so ago by Gene DellaSala. It may help you with your goals.

 

[Savant]

Great piece, Jeff. Just a couple of thoughts:

- An STC rating is got by curve-fitting the lab-measured, 1/3-octave-band TL data from 125 to 4000 Hz; a wider range than the 500 to 2000 Hz indicated in the article.

- I was happy to see editorial mention of utilizing the absorbent properties of drywall at low frequency to advantage in small room design - and how difficult a process it is! While difficult, if a designer is already involved, the right combination of a high-STC wall, like poured concrete, with an interior "finish" of studs and drywall (leaving the appropriate airgap, of course) could yield outstanding results. It's not as easy as it sounds though. The variables are the mass of the drywall, the depth of the cavities, the amount of absorption in the cavities, the spacing between the studs, etc. In all likelihood, all these will have to be varied considerably to make the results worth the trouble. Of course, while this could help reduce the need for "tweaks" like DRC or overly-large "traps," the design and construction costs will also be substantially higher, thus introducing another (sometimes the most important) variable...

These two comments aside, nice work!

 

[Jeff Hedback]

Hi Jeff.

Thanks for the read and the comments!

I appreciate you bringing forth the STC range. I was attempting to highlight how the STC rating by itself without futher details of the TL numbers at different frequencies is most helpful for typical speech or common applications, not the complex needs of a dedicated music space.

I really appreciate you expanding on the use of drywall to "tune" a room. I included the editorial because it needed to be mentioned, but would be beyond the needs of that article to go into detail. You brought it forth in terms of balance, meaning: if there is an ultimate goal of performance and aesthetics...which choices are the best for each person??? Nice emphasis.

I like this forum a great deal. It allows points to be brought into the light and better focused. What a tremendous way to communicate.

I guess I'm giving kudos to Gene and Audioholics for some great structure and planning.

Hope you're well!

 

[bigeric]

Into the details ...

This is a great thread, exactly what I need to make the next step forward in my construction planning.

I'm building a theater in my basement on a shoestring budget but, being an engineer, I want to get the bones of the room right so that I have a solid foundation for the theater of my dreams when I can afford it.

I'm looking for a bit more detail on how to make my room have good acoustical performance. Here are some of the things I'm working with based on a lot of reading on the forums:

Front wall, poured concrete. I've been planning to stud in a wall and have a false, acoustically transparent screen wall. Total flexibility in materials and distance of the stud wall from the concrete.

Left side wall, poured concrete. Total flexibility in materials and distance of the stud wall from the concrete.

Right wall, stud wall. Total flexibility in materials and some flexibility on location to balance room width and audio performance. Backs to a storage room and hallway, no room directly adjacent.

Back wall, stud wall. Total flexibility in materials and location. Backs to a utility room / workshop.

Estimated room dimensions:
front third 12-12 1/2 feet wide
rear two thirds 14-14 1/2 feet wide, door on right side aisle on right side

Estimated screen size:
8-9 feet wide

Estimated viewing locations:
row at 11 feet from screen
row at 16.5 feet from screen
bar behind second row

Thanks in advance,
Eric

 

[tsmessi]

Love

This is an interesting discussion. thank you for sharing :

 

[Sasquatch]

So I could improve the acoustics of our TV room by adding a layer of ordinary foam insulation to the back wall and covering that with a layer of Hardiboard? That would sort of mimic the the effect of the inner wall often built in studios? The back wall of our room is normal timber/drywall construction and adjoins the garage. Does the garage space then factor into the room design? Could I add anything to the garage side of the wall to improve the TV room acoustics?

Our TV room is very small. So I can't sacrifice a ton of space building extra walls and adding massive traps everywhere. And the couch has to be on the back wall. So there isn't room behind the seating to add much of any treatment to the back wall.