Traps, walls and furinishings, oh my!

[zuter]

I'm in the process of closing off my den for my theatre room. It's in the basment with already finished wall ceiling and floors. It measures 20' x 11' (see below diagram). I've removed a banister and closed off this section to include a doorway. I'll be adding a solid core door with weather stripping and bottom sweep to stop light and noise. To this new wall section I've added "safe and sound' insulation. The remaining walls are 2 x 4" drywall in front of concrete. Additionally I'm changing the flooring to 12 mil laminate wood flooring.

I was going to re-run my sound setup routine on my amp (Pioneer Elite) to recalibrate my HT. I know that introducing so many reflective surfaces will require taming and was going to put some throw rugs and stuffed recliners in to help. However after reading some other posts here I realize that this my not be enough and other treatments my be required. This is a whole new world to me and quite frankly I'm not sure where to start. Bass traps, wall treatments, deading of the front wall, etc? I've some idea as to what these are but how to impliment them, nada!

I've almost completed the new wall and the door is next, after that, the floor. I feel it would be best to get that done first then test the room, soundwise, to find what needs to be done. I don't have the testing equipment for REW but have access to a professional SPL, which I used to tweak my current setup to 85bd. However, if there things that are true for all theatres that I should do now, please let me know.

Thanks

[bpape]

Carpet on the floor is a better idea if you haven't already done the floor.

Things that need to be done to all dedicated theaters:

- Broadband bass control in the front corners, rears if you can swing it.

- Kill the front wall behind the speakers 100%

- Address all side wall reflection points (# of seats x 3 front speakers = number of points on each wall).

- Additional absorbtion in targeted places as required to deal with response anomolies and bring decay times in line across the spectrum.

Bryan

[Prof.]

Also in your drawing, the back speakers are shown too far apart..Ideally they should be apart about the width of a 3 seat sofa..

[zuter]

Thanks Bryan for the info. But could you go into more detail or provide links to your various points. As I said I understand the basic ideas just don't know how to achieve them... ie: Broadband bass control in the front corners, rears if you can swing it." ? you mean bass traps I assume. or "Kill the front wall behind the speakers 100%"...haven't a clue how to do this!

As for the carpet, my WAF wants laminate so...whatever baby wants, baby gets! Best I can do here is throw rugs and overstuffed furniture. Wall treatments, as longs as there are decorative, are do-able. Decay times should be handled by the MCACC (calibration) on the amp - though further treatments maybe required.

[zuter]

Hi Prof

I should have pointed out that the drawing isn't to scale nor is placement of components properly recorded. The speakers fronts and rears are actually 2' in and 2' out from the corners. I'm currently looking into wall/ceiling mounting the rears but haven't decided yet as they are the same as my fronts so they are large and heavy.

[bpape]

MCACC just sets the relative time delay between speakers. It does nothing to change the decay time in the room. I'm talking about getting the midrange decay time down to maybe .35 seconds (time to decay by 60db after things stop playing). A bit higher in the bottom, lower on top. Keep it balanced and know what you're shooting for.

For the corners, bass traps is a misused term. Real bass traps are relatviely narrow in range and not terribly broadband (and are also usually VERY VERY deep - think 1-2 FEET thick). The concept is to absorb from as low as you can all the way up on the front corners. For the rest of the wall, cover it 100% in absorbtion from 1-2" thick depending on the situation.

Bryan

[zuter]

Thanks

So if I were to build corner traps they'd start at the floor and go to the ceiling...this is do-able. And in your previous post you mentioned this for the rear wall also. However what is the construction for this? Build a frame, add a streched material, to cover, with sound absorbing material as a fill for the corner? For the Front wall I add the 1" - 2" material...again same construction concept as above? Can I use styro-foam sheeting? I can see how this would would "kill" the wall!

I work at a large theatre/auditorium, which was recently renovated and they use large cloth panels to help reduce reflections...of course they use many other techniques...could this concept be used also? These panels would have to be mounted away from the walls (and corners possibly) 2" - 5" and use suffciently heavy material to gain any benefit. Our sound guys could get me this material! I might get the wife to agree to that because the panels could be easily removed for cleaning! Also, if done right - like my work place, these panels could be movable (rolled up) to change the sound for different situations like music or just tweaking purposes?

Let me know what you think!

[bpape]

Slow down a bit. Cloth by itself will do nothing (except if you put it in front of a diffusor and that will mess it up). Spacing heavy cloth away from a wall will actually produce a very narrow filter which is NOT at all desirable in most cases. Styrofoam will do nothing except take up space and maybe do a TINY but above 10kHz. These are not where your problems will lie. Use standard and proven materials that have known acoustical properties.

For the corners, think of sheets of 2" OC703 cut into 17x17x24" triangles. Stack those up to make solid chunks floor to ceiling. Cover with cloth. THAT is a good bass absorber. 2" straddling the corner is minimalist at best and will miss most of the subwoofer range.

Also, understand that while some of the materials in a commercial theater would be usable, HOW they're used and how much is totally different in a large space than it is in a smaller (relatively) residential space.

Reflection points on the walls can be done with 2" 703 covered with cloth. Front wall - depends on the room and a thousand other things as to what thickness is required. Sorry, it's not a cookie-cutter thing to PROPERLY treat a room. You have to look at size, # of seats, # of people, how is the room built, usage (HT or 2 channel or both), etc. All of those things impact the design.

Bryan

[zuter]

Thanks again Bryan for the info regarding materials.

I just spoke to our sound tech. He agrees that deadening and reducing reflections are key to good sound in a HT as it is in a live theatre space. They use specailized materials and shapes to reduce reflections in the audience chamber while the stage is "dead". These techniques are specifically designed for the given space to achieve the desired effect. The same can be said for the average HT. However, it depends on the space and the budget of the owner.

His suggestions evolve around the proper placement of the speaker(s) and lowering the reflections while not elimnating them. His recommendation is to use rugs and furnishing first then look at the space to determine exposed reflective points. Placing curtains (or tapestries) on the sidewalls will greatly reduce these problem areas. Deadening of the front and rear walls can be achieved by using sponge foam (2") covered with a layer of "eggcrate" foam....the front wall is the most important for this treatment. In front of the foam using a heavy velour (or any heavy material) will effectively deaden the wall and look betterthan the foam alone. I like this idea as I can cover the front wall and then let the wife decorate with a curtained theatre motif! The rear wall can have a similar treatment if I choose or if reflections become a problem.

As for the ceiling, use a drop ceiling with insulation or batting to further deaden the space...this came up in coversation concerning an idea I had for adding indirect lighting. Not something I'll do right away but down the road.

I'm sure your material suggestions are also good but depending on the costs would determine if these are in my budget. However his simple suggestions maybe good for others with similar budgets. I look forward to posting pics of my space as I complete each stage.

[bpape]

You need to make your own decisions. I'll just tell you that I redo theaters and listening rooms every day that were initially done the way you're considering doing it. Yes, placement is important, key in fact. However, rugs, curtains, foam with cloth over it, etc. is purely upper mid and high frequency treatment that completely ignores the bulk of the spectrum and the part that really makes the most difference IMO.

Just trying to save you a redo later down the road and spending more money in the long run than is necessary. Also, remember that the person you're speaking with on the side is used to dealing with larger spaces where acoustic theory and treatment are quite different than in residential sized spaces. In particular, 250Hz down is dealt with exactly opposite in larger spaces than it is in smaller ones.

Bryan

[stevenkelby]

bpape wrote:

For the corners, think of sheets of 2" OC703 cut into 17x17x24" triangles. Stack those up to make solid chunks floor to ceiling. Cover with cloth. THAT is a good bass absorber. 2" straddling the corner is minimalist at best and will miss most of the subwoofer range.

Sorry to but in, but Bryan, how can we know, or calculate, which range of frequencies will be absorbed by this, and by how much?

Thanks,

Steve.

[zuter]

bpape wrote:

You need to make your own decisions. I'll just tell you that I redo theaters and listening rooms every day that were initially done the way you're considering doing it. Yes, placement is important, key in fact. However, rugs, curtains, foam with cloth over it, etc. is purely upper mid and high frequency treatment that completely ignores the bulk of the spectrum and the part that really makes the most difference IMO.

Just trying to save you a redo later down the road and spending more money in the long run than is necessary. Also, remember that the person you're speaking with on the side is used to dealing with larger spaces where acoustic theory and treatment are quite different than in residential sized spaces. In particular, 250Hz down is dealt with exactly opposite in larger spaces than it is in smaller ones.

Bryan

Absolutely! The differences in theory are correct. However, the differences are "audiophile" tweaking...I'm not that hard core! My space will definately not be "high end". All I want to do is compensate for the changes to the room when completed, ie: enclosing a room with new hard floors. Reflections will be my biggest problem specifically in the mid and upper range. Adding absorbing materials and soft surfaces will go along way if strategically placed.

Besides, adding large corner columns of material will not make it past the WAF but a proscenium of heavy curtains, resembling a theatre, goes along way in deadening the space, hiding ugly wiring, adding aesthetic enhancements and is easily maintained...all WAF approved! This, including proper speaker placement and calibration should control but not eliminate most of my reflection problems.

If, down the road, I decide to really get into this, then people like yourself with specific knowledge of HT's will be invaluable.

Thanks again