BroadBand Bass Trap's Build - Page 18 - Home Theater Forum and Systems -

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post #171 of 175 Old 08-03-09, 09:39 AM
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Join Date: Sep 2008
Location: Calgary
Posts: 201
Re: BroadBand Bass Trap's Build

Hey Jason ... wonder if you could make some suggestions as you have clearly invested alot of time on this subject

Theatre is at rough-in stage but planning for acoustic treatments ... room size is ~ 14' X 23' ... 7.1 surround using Axiom M80 LR, EPIC 600 SUB, VP150 center and 4 X QS8 surrounds ( another sub to be added later on if needed )

I had planned to put OC703 corner wedge bass traps on screen wall, linacoustic on rest of screen wall and for the first 4' of the side/rear walls and empty space above that covered with a AT fabric like GOM or Dazian

my questions for you are:

- would you recommend using diffusors above the linacoustic on the side/rear walls ?

- if yes, then due to the linacoustic being 1" thick would it possible to use strips of hardwood to create the channels for the diffusor and glue to the drywall to save space ?

- if I build diffusors with a max depth of 1", would that be beneficial ? ( could go deeper on rear wall ... maybe 2" deep ) ... reason I ask is all your diffusors seem to be much deeper

- if all the above works out, I had planned to cover all the walls with a AT fabric, do you see any problem covering a diffusor with a AT fabric ?

I am very limited on the side walls due to the door location ( support post restricts entrance door location to be very close to side wall )

Thanks for any suggestions
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post #172 of 175 Old 08-05-09, 11:29 AM Thread Starter
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Join Date: Jan 2007
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Re: BroadBand Bass Trap's Build

Hi Steve,

Diffusors inc Flutter Echo Diffusors (around 25-30mm thick) will work fine on the rear sidwalls, you can place them over semi riged fiberglass or absorbtion substrait, but small cutouts in the deeper wells of the diffusors are needed as well as random spacing with an air gap behined the diffusors to allow for the lower frequencys to be absorbed below where there usfull diffusion stops...
Flutter Echo Diffusors can be mounted to small strips of wood that are attached to the drywall.. I have never cut varying depths of wood strips/vains based on QRD prime seed to form wells for diffusors, but they would need to be mounted to A hard backing such as wood and must be built very precisely to perform as designed....

The main thing to remember with QRD diffusors is the deeper the wells the lower they will diffuse
the larger QRD's I made are prime seed 13 & 7" deep but I chose to placed them on the back wall next to my rear bass traps...

I would'nt recommend covering diffusors with any thing due to affecting there ability to diffuse optimumly....

A good rule of thumb for the most important areas to cover when it comes to room treatments for A Home theatre is to first treat the 4 corners with bass traps either with super Chunk style or 6"thick floor to Ceiling if possable Also the first reflection points inc the Ceiling..
Then you can move on to treating the rear wall with absobtion directly behined the rear seats and diffusion on either side closer to the corners, Diffusion on the rear side walls also placing Accoustic insulation batts in the Ceiling cavity above the theatre can aid in low freq absorbtion...

It is important to not over treat the room with two much absorbtion as this will deaden the room to much, rather its A fine balance of Absorbtion reflection and Diffusion analizing the room with mic & Acoustic software then futher tweaking/refining untill you get A good balance & even decay time...

Hope this helps
Cheers Steve...
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post #173 of 175 Old 08-05-09, 05:58 PM
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Re: BroadBand Bass Trap's Build

Hey Jason ... thanks for the response

Due to WAF and wanting to have the fabric theatre look where all walls are covered in fabric it looks like diffusors will be out for me then if they cant be covered with fabric

The ceiling will be R19 batt/rsic clips/hat channel/DD/GG ... walls staggered stud/R13/DD/GG

If you look at the drawing I can only fit corner bass traps in the front of the theatre room as the rear of the room has 2 doors to deal with ... I can probably put 2" or 4" insulation on the rear wall though ... maybe even 6" if that will help with bass trapping ??? - Should I just cover the entire rear wall then with absorbtion or just where the first reflection point software indicates ?

I had also planned to put a sub built into my riser ( 4 X 12" Shiva drivers firing to the back wall - drawing in my build thread )

Also I plan to build a coffered ceiling with Linacoustic in the areas of first reflection as my center channel will be mounted in the soffit
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post #174 of 175 Old 08-05-09, 11:53 PM Thread Starter
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Posts: 193
Re: BroadBand Bass Trap's Build

Hi Steve, This looks as though its going to be an Awesome HT mate, I could only wish for A room this size to Build A HT..

You could use Polycylindrical diffusers "Polys" on the rear side walls and paint them the same colour as your Acoustic fabric or put acoustic fabric over them, they can be fairly easy to make with thin Ply, also I think Bryan GIK sells polys...

you could put some form of absorbtion 6" thick semi rigid fiberglass on the back wall placed between the Ceiling and rear wall thus providing an air gap to boost the lower freq absorbton, or placed against the rear wall..

I found the more Subwoofers (I have 4) which in turn brings up the LF sound pressure the more bass traping I needed to try and tame the LF decay time/ringing..

Also the down side to: more rigid you make your side walls IE:adding 2/3 layers drywall) the less LF they absorb so the more important Acoustic treatment's become, same goes for concrete walls...

Cheers Steve,
RE: Jason...
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post #175 of 175 Old 11-01-11, 06:19 PM
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Join Date: Aug 2011
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Re: BroadBand Bass Trap's Build

Hi All. I have been reading and re-reading this thread lately and there is some great information in this thread. I know this is a couple of years old now but i would be keen to hear where you are all at two years plus down the road. Changes made ... what you would definitely do again and what didn't really work out. The reason for these questions is because i am about to go down the same route with my room. Thanks a heap. cheers j
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