Ginky Weeds Home Theater

[Ginky Weeds]

Lumber for stage and riser is in the house.  My wallet's a lot lighter....

[bmoney]

Has wood not come down in price?

[Ginky Weeds]

Supposedly, but it sure seemed expensive yesterday.  Still stings....

[Ginky Weeds]

While waiting for my drywall amigo to break free, I've been designing my stage and riser.  And I'm torn on what fill to use in each.  I've read lots of dialogue on the other forum debating between the two.  My conclusion is that those that have been building home theaters for some time all recommend filling the stage with sand and the riser with insulation.  There are others, even one that measured vibrations and SPLs in the process, that couldn't measure a difference or simply don't want to lay out the cash and effort to schlep bags of play sand.  I'm leaning toward stuffing both with insulation and using isolation feet on my four subwoofers, two on the stage and two on the riser.  Have any of you built stages or risers with subwoofers on them and not used sand as an acoustic absorber?  Hoping to hear some actual experience.

Thanks!

Chuck

[bmoney]

Ive never seen anything OTHER than sand being used.  I dont have a stage so cant directly comment but from all Ihave seen its sand or nothing.  never heard of insulation being used tbh

[Ginky Weeds]

It appears some people are using insulation to avoid the cost and labor intensity of the sand.  And I agree that sand in the stage is "best practice".  So I'm coming around to filling the stage with sand.

The riser is a different story.  I haven't seen any reports of sand used there, just "pink fluffy".  I'm still studying if I want to and can use the riser as a bass trap.  I will either fill with sand under the two subwoofers and use insulation in the remaining cavities or use insulation all the way and attempt to design it as a bass trap.  That requires venting of the riser from what I read and I haven't absorbed all that yet to come to a conclusive design.

Chuck

[bmoney]

The riser most use it as a bass trap so def no sand. If mine was taller I would have cut vents into it to make it a bass trap. But…

[bmoney]

Sorry I didn’t read your post all the way through lol

Yeah you have to design it ahead of time a s a trap. Using hangars. And cutting vents around the edges. They work extremely well. Risers are so expensive Now to build with 3/4” plywood being 100$ a sheet

[Ginky Weeds]

I spent a lot of time yesterday searching and reading about risers as bass traps and concluded that it's not worth pursuing since my riser isn't tall enough to have much affect.  That's according to the Erskine group.  So I'm just going to stuff the riser with insulation with no vents.  I do plan to stack insulation blocks above each of the four subs to function as bass traps.  And with isolation feet on the subs, I think I'll be good to go.

Yesterday I ordered 160 60 lb. bags of play sand for the stage.  Hope my old bones endure the 'rite of passage'...

Happy Thanksgiving all!!

Chuck

[randman]

I'm just about to start my home theater in the basement. Home Theater will be built on concrete. Subs in front and riser in rear wall. This is the first I've heard about risers being used as bass traps. I'm wondering how the effectiveness of a riser is driven by insulation versus vents. For example, what if I pink insulation, but not vents (since vents would me more labor intensive in terms of installing them and then getting carpeting around them). Wondering how much help the vents will help. Insulation, on the other hand, seems much simpler to add. So, trying to see is the insulation would be a bigger bang for the buck approach. Or do we have to worry about vents, and which direction the studs in the riser face, etc. Any enlightenment? 

[Ginky Weeds]

By the way, the 3/4" plywood wasn't $100 a sheet, 'only' about a third of that.  $100 would qualify as 'sticker shock' for sure!!

[Ginky Weeds]

randman, my understanding of the intended effects of the two approaches to riser design are different.  Filling with insulation without vents I believe is simply intended to quiet vibrations and remove hollowness as impacted by footfalls or sound.  The broadband absorber approach uses the entire cavity filled with insulation to absorb and deconstruct sound waves, with primary interest in low frequencies.  To create the large cavity in this design, the riser is built with stringers that are a size smaller than the frame.  In my case, 2 x 8 stringers in a 2 x 10 frame.  This allows sound waves to pass throughout the insulation in the entire cavity.  How effective are they?  I don't know...I'm still struggling with the whole concept of stage and riser design and why they are not designed in the same way.  

This morning I took advantage of the opportunity to send questions to Peter Aylett on the other forum.  Peter is introduced as an integrator of over 30 years and now a partner at HTE Acoustic Interior Design, Peter currently chairs the CTA/CEDIA R10 Standards Committee as well as one of its workgroups currently re-writing best practice for entertainment space/cinema/theatre audio design.  Here are the questions I asked:

Peter, I’m interested in your comments on stage and riser construction. I’m currently designing them for my HT (in progress; hanging drywall next week) and have read extensively the discussions on the AVS forums regarding both. And I come away with no clear approach. I understand that ‘best practice’ for stages is to fill them with sand to absorb sound and prevent vibration of the stage and the surrounding structure. I also understand that many like to design risers as ‘broadband absorbers’ using vents to allow sound waves to enter the structure and be deconstructed by the insulation filling the large cavity. I see both as sound (pun intended) approaches, but have the following questions about my design that includes large LCR speakers and two subwoofers on a 17’ x 6’ x 10” stage and the equipment rack and two large subwoofers on the 10’ x 10’ x 10” riser:

• Do you agree that the stage should be filled with sand? If not, what do you recommend instead?
• Do you promote the design of a riser as a broadband absorber? If not, what do you recommend?
• In thinking about the applications of each, if the broadband absorber is desirable in the riser, why shouldn’t the stage be designed as a broadband absorber as well? It will have similar impact from and equal number of subwoofers as the riser, right? Conversely, if sand is more beneficial, why not use it as fill in the riser as well?
• Do you recommend use of corner bass traps in both front and rear (both will be concealed in my design), regardless of construction of riser (and stage?) as broadband absorbers?

I hope to get a response that helps to guide my design decisions on the stage and riser.  Obviously, I'm still struggling.

[bmoney]

Def looking forward to his response 

[randman]

randman, my understanding of the intended effects of the two approaches to riser design are different.  Filling with insulation without vents I believe is simply intended to quiet vibrations and remove hollowness as impacted by footfalls or sound.  The broadband absorber approach uses the entire cavity filled with insulation to absorb and deconstruct sound waves, with primary interest in low frequencies.  To create the large cavity in this design, the riser is built with stringers that are a size smaller than the frame.  In my case, 2 x 8 stringers in a 2 x 10 frame.  This allows sound waves to pass throughout the insulation in the entire cavity.  How effective are they?  I don't know...I'm still struggling with the whole concept of stage and riser design and why they are not designed in the same way. 

This morning I took advantage of the opportunity to send questions to Peter Aylett on the other forum.  Peter is introduced as an integrator of over 30 years and now a partner at HTE Acoustic Interior Design, Peter currently chairs the CTA/CEDIA R10 Standards Committee as well as one of its workgroups currently re-writing best practice for entertainment space/cinema/theatre audio design.  Here are the questions I asked:

Peter, I’m interested in your comments on stage and riser construction. I’m currently designing them for my HT (in progress; hanging drywall next week) and have read extensively the discussions on the AVS forums regarding both. And I come away with no clear approach. I understand that ‘best practice’ for stages is to fill them with sand to absorb sound and prevent vibration of the stage and the surrounding structure. I also understand that many like to design risers as ‘broadband absorbers’ using vents to allow sound waves to enter the structure and be deconstructed by the insulation filling the large cavity. I see both as sound (pun intended) approaches, but have the following questions about my design that includes large LCR speakers and two subwoofers on a 17’ x 6’ x 10” stage and the equipment rack and two large subwoofers on the 10’ x 10’ x 10” riser:

• Do you agree that the stage should be filled with sand? If not, what do you recommend instead?
• Do you promote the design of a riser as a broadband absorber? If not, what do you recommend?
• In thinking about the applications of each, if the broadband absorber is desirable in the riser, why shouldn’t the stage be designed as a broadband absorber as well? It will have similar impact from and equal number of subwoofers as the riser, right? Conversely, if sand is more beneficial, why not use it as fill in the riser as well?
• Do you recommend use of corner bass traps in both front and rear (both will be concealed in my design), regardless of construction of riser (and stage?) as broadband absorbers?

I hope to get a response that helps to guide my design decisions on the stage and riser.  Obviously, I'm still struggling.

I plan on having wall-to-wall carpeting and 1/2" padding under the carpet, so I'm not sure how much more insulation will help regarding minimizing vibrations and footsteps. Carpet/pad will go over the concrete floor in the front of the riser and on the riser itself. Putting insulation in the risers doesn't seem like it would require much labor and cost, so it may be good to just do it without more "analysis paralysis" :-). 

But adding vents would be a bit more labor/time/cost intensive, and from my quick perusal of this topic, it has to be done mathematically correctly in order to determine the ideal places to put the vents? Not sure how much I would gain by doing the vents. 

Your other questions are very interesting. Wow. Sand is so much heavier and messier than insulation. I recall making a mess when I added sand to some speaker stands in the past, and decided not to do it again when I got new stands later . 

[Ginky Weeds]

I'd encourage using the insulation in the riser.  For the same reason that most speakers contain fill and why drummers put pillows in their kick drums.  Should knock down the hollow sounds and help to keep it from resonating.  And as you say, it's relatively inexpensive and easy to do.

Adding vents sounds like an effective approach as a bass trap.  I wouldn't know where to start to make it a tuned chamber.  But I like the idea of making it a broadband absorber using vents placed at the wall boundaries.  In my case I can add vents that will be concealed from the theater area.  So I will likely do that.  But still waiting to hear an opinion from Peter Aylett before making that decision.

Chuck