BroadBand Bass Trap's Build

[cinema mad]

For Any One that is interested in Building there own PRO LOOKING Corner Mounted BroadBand Bass Traps take A look down A few posts for Some Ideas and What I came UP with.....


I went with Ultratel 50mm thick 1200x2400 semi rigid fiberglass for my bass traps the packs came in lots of 3 sheets per pack, it's very pricey at A retail price of over $300 per pack , I was luckily able to get the Ultratel direct from bradfords .... I made my Bass traps 8ft high X 690mm wide and 6in thick (3 layers),I put them across the corners so ended up with an air gap being 16in out from the wall corner to the front of the trap's.. Here are some pictures of the front Bass traps.....

Hope this helps....

Cheers.....

[Prof.]

cinema mad wrote:

I went with Ultratel 50mm thick 1200x2400 semi rigid fiberglass for my bass traps the packs came in lots of 3 sheets per pack, it's very pricey at A retail price of over $300 per pack ,

That is expensive!!..I got the 50mm. Supertel sheets for about $60.00 each..

I made my Bass traps 8ft high X 690mm wide and 6in thick (3 layers),I put them across the corners so ended up with an air gap being 16in out from the wall corner to the front of the trap's.. Here are some pictures of the front Bass traps.....

So all three layers were 690mm. wide?..That would leave quite a gap between the panels and the corner..
I don't know if that would be beneficial or detrimental to the performance of the traps,considering that the wedge type traps are right in the corner..
Brian might be able to throw some light on that..

Hope this helps... It appears that my 1024x768 jpeg pictures will not upload it thinks they are 1200x1000 Works fine on AVS...

I normally load photos at 800x600 without a problem..You might have to resize them..

[cinema mad]

Hi PROF, For A pack of 3 Ultratel 1200x2400 x50mm (2in) thick is over $300au retail but I did'nt pay that Direct from CSR Bradfords, Bradfords wont deal direct to the public only Trade or suppliers.... the Specs for 50mm Ultratel KG/m3 is 0.35@ 125hz, while 50mm Supertel KG/m3 is 0.27@ 125hz... So if you X that by 3 (150mm thick) Ultratel is the way to go for this type of Bass traps...

Own's Corning 2" plain 705 is 6.0pcf,96kg/m3 and 0.16@ 125hz..
The Same Own's Corning plain 2" 705 with A 16" air gap is 0.62@ 125hz, so as you can see with A 16" air gap from the wall 705's performance is more than 3 times better than flat on A wall....

To up the efficiency/performance of these type of corner bass traps An air gap is A must......Also noted in the fourth Edition of Master Handbook of Acoustics... Thankyou for the tip for uploading photos Prof

Here is A 750x562 picture of my front Corner Bass traps....

Cheers....

[cinema mad]

I first made A frame 690mm wide x just under 8ft high, I covered the front with 1 large piece of Black speaker grill cloth doubled up for each Bass trap so I had no fabric joins, and for the back I used doubled up white open weave stuff like used under couches can't recall the name.. I used my air Staple gun with 80/10mm staples to attach the coverings...

To attach the Bass traps to the wall I used A stud wall hook right in the top corner of the wall and attached 2x 4mm Gauge 40mm length eye screws to the top left and right corners of the bass trap's, then used 12 KG picture frame wire to pull and hold the bass trap tight into the corners... I also made A stand for the bass traps to sit them on for added stability and authetics.... see the attached picture....

I purchased the black speaker grill cloth and white open weave fabric from Spotlight....The Fixings I got from Bunnings....

Hope this helps.....Cheers....

[Prof.]

Hi Jason..

Thanks for the detailed description of your bass traps..

cinema mad wrote:

the Specs for 50mm Ultratel KG/m3 is 0.35@ 125hz, while 50mm Supertel KG/m3 is 0.27@ 125hz... So if you X that by 3 (150mm thick) Ultratel is the way to go for this type of Bass traps...

Yes, I did see the specs. for the two types and the Ultratel is a denser, more compacted fibreglass..which tends me to believe that it would be more reflective than the Supertel..
But hey..if it's worked for you in your environment, then that's all that matters..

Own's Corning 2" plain 705 is 6.0pcf,96kg/m3 and 0.16@ 125hz..
The Same Own's Corning plain 2" 705 with A 16" air gap is 0.62@ 125hz, so as you can see with A 16" air gap from the wall 705's performance is more than 3 times better than flat on A wall....

I'm surprised that a 16" air gap could change the performance as much as that!

I'll have to incorporate that sort of air gap in my traps, and see if there's any improvement..

[Prof.]

cinema mad wrote:

I first made A frame 690mm wide x just under 8ft high, I covered the front with 1 large piece of Black speaker grill cloth doubled up for each Bass trap so I had no fabric joins, and for the back I used doubled up white open weave stuff like used under couches can't recall the name.. I used my air Staple gun with 80/10mm staples to attach the coverings...

To attach the Bass traps to the wall I used A stud wall hook right in the top corner of the wall and attached 2x 4mm Gauge 40mm length eye screws to the top left and right corners of the bass trap's, then used 12 KG picture frame wire to pull and hold the bass trap tight into the corners... I also made A stand for the bass traps to sit them on for added stability and authetics.... see the attached picture....

Sounds like a very effective design..well done..

I purchased the black speaker grill cloth and white open weave fabric from Spotlight....The Fixings I got from Bunnings....

I've bought numerous materials from Spotlight over the years, but I've never seen any grille cloth there..
Are you sure it was grille cloth or something that looks like it?..
I recently bought a material from them that looks like grille cloth, which I'm using to cover some new acoustic panels..
It's called Black Polyester Stretch...It has the same open weave as grille cloth, but it's a fraction of the price, and comes in 1500mm. wide rolls..

BTW..I think that white material you're referring to is Dacron..

Some full shots of the finished traps would be nice to see..

[cinema mad]

Hi Prof, Thankyou for the kind words...

The Black speaker cloth I used from spotlight sounds simmilar to yours, Scott from spotlight Geelong orderd in A few rolls its called "Loud Speaker Meterial" original name spotlights part No 1283123... and the roll is around 1400mm wide.. The problem is he is not back at the Geelong store untill tomorrow to confirm I was given the correct part No... I will post A picture of the white material I used on the rear of the front corner Bass traps Because its not Dacron, full shots of front bass traps as you requested....

Hope this Helps, Cheers...

[Prof.]

cinema mad wrote:

I will post A picture of the white material I used on the rear of the front corner Bass traps Because its not Dacron, full shots of front bass traps as you requested....

Hope this Helps, Cheers...

Ah yes!..I see the white material is a type of netting, which is fitted to the back of the traps..
Obviously, this would allow sound waves to pass through without affecting the performance of the Ultratel, as opposed to a solid backing...Good idea..

I didn't have to worry about making my front traps look neat, because the're behind a screenwall..
I just stacked the raw panels in the corners, floor to ceiling and stapled black burlap across them..

It looks like you've done a nice job on yours. .

I'll have to look up that material no. for the "speaker cloth" and see just what it is..
How much per metre did it cost?..The material I bought was only $9.95/M..

[cinema mad]

Hi PROF,
I have A young 6 year old son and 14 year old daughter so I wanted to make sure that none of the Glass fibers from the ultratel could escape and be air born ....

I just got off the phone from Scott of spotlight Geelong He said that if your spotlight store does'nt carry the Speaker Cloth that they can post it any where in Australia for $6.95...

The loom width of the speaker cloth is 1.5mt, PartNo 1283123 and $12.95mt....

Cheers.....

[Prof.]

cinema mad wrote:

Hi PROF,
I have A young 6 year old son and 14 year old daughter so I wanted to make sure that none of the Glass fibers from the ultratel could escape and be air born ....

Generally it's pretty safe...It's only when you're cutting it that you need to cover up, not to get any on your skin..

I just got off the phone from Scott of spotlight Geelong He said that if your spotlight store does'nt carry the Speaker Cloth that they can post it any where in Australia for $6.95...

The loom width of the speaker cloth is 1.5mt, PartNo 1283123 and $12.95mt....

Thanks Jason...I'll see if I can find that part number online, but I'm not sure if Spotlight actually list their material numbers online..If not, I'll give my local shop a call..

[cinema mad]

Because I Had A day off I decided to Build Broad Band Bass Trap's For My Rear corners.. I thought It might be good to share with you all How I made Them...
So I took some step buy step photos to help...

To Make my Rear Corners,1770x640 Broad Band Bass Traps the following items is what I used....
CSR BRADFORDS ULTRATEL 2" 1200x2400 semi riged fiberglass cut in half to make 600 X4" thick.. "Must weare Gloves and mask"
2 mtrsx1500mm wide Speaker Grill Cloth (spotlight)
4mtrs Muslenx900mm wide (spotlight)
Wood Pine 2x2.4mtrsx90mmx19mm
8x 40mmx3.5"OD" screws
PVC Glue
80/10mm Bostitch Staples

The Tools I used...
2.4mt Straight Edge (for cutting Fiberglass)
Sharp long bladed stanely Knife or Sharp BREAD knife (any sharp knife will work)
Tape mesure
Makita LS 10.13 Slide Compound Saw
1/4in Trimmer (router)
1x small 1/4" roundover router bit
Air Stapler with 80/10 Staples
Compressor
Bench Drill for counter sink holes
Bosch power Drill
Dewalt 18v DrillDriver
Bosch random orbital sander with 240grit sand disk
Clamps 2x1mt and 4x 60mm

Broad Band Bass Trap Prep
First I measured and cut the 4 pieces of 90x19mm pine (per Bass Trap)
then I cut 4 small triangel corner pieces to give the frame Rigidity
marked out the 2x screw holes per side 8 total to drill with my bench drill (longest Piece)
Drill bit should be the size of the screws(3.5mm)..
lay out the pieces of frame (Dry Fit) clamp so flush and square and drill through the 8x pre drilled holes into the end pieces with A 2.5 to 3mm drill bit screw in screws as you drill each hole but not to tight...

Dissasemble and counter sink holes slightly
lay out frame reasemble one end (clamp) but leave one end out,Apply PVC Glue liberaly to this unasembled end on bothends of the join then clamp checking ends for flush/square and apply the scews tighten..
glue both surfaces liberaly and fit (clamp) 2 of the triangle peaces to the inside of the joins you just glued and screwed together..
Repeate the Same procedure at the other end..
Leave fram clamed to dry for 2 hours minumum..

Next sand the ends and triangle pieces flush as well as the sides/ends
Now route the outside edges top and bottom with A "small" round over Bit

Cut the semi rigid 605/supertel/Ultratel to the inside diamitor of the frame 1200x2400 cut in half=600mm x 4" thick using your straight edge and knife to score the semi rigid Fiberglass with 3 or 4 passes...
Next lay out the 1500wide speaker cloth in half +75mm on the floor taking care that the speaker cloth is folded well
lay the frame on top of the cloth making sure that the frame is equal distant at all sides top bottom, working along the sides strech the fabric up to the back of the frame working from the middle to the ends. The side affect of this will be that the fabric overhang at the ends will pull in A bit allowing us to get mor streach out of the fabric for the sides...

Start from the middel of one side and strech the cloth and staple onto the back of the frame with 3 or 4 staples 2" apart, go to the exact oposite side and do the same strech staple
to back 3-4 staples 2" apart (Dont over strech the fabric)
Repeat this procedure crossing over sides until you get 1" from the end leving that unstapled for now..
Repeat the same above procedure untill ether side is completed...

For the ends start from the middel streching the fabric to the back of the frame with 3-4 staples an inch or so Apart
Go to the corner and fold the fabric so you get A nice even fold and staple in place repeat this fo both corners of this end.. now working from the middel again Strech and staple the fabric to the back of the frame working to the corners (dont over strech fabric)...Repeat the procedure for the oposite end

Flip over your broad Band bass trap to check the fabric has no rinkels or flaws..

Now lay it back down so the Rigid fiberglass is facing up so the Muslin can be fitted to the back..

First get the 4mtrs x 900mm Muslim and fold it long was so it is now 2mtrs x900mm (doubled up)
lay it over the back of the fiberglass so it is at equal distent all the way around besides the end with the fold in the Muslim Make this end flush no over hang
Next Start At the "END" of the bass trap with the Muslim that has the fold make it 5mm before the end and stapel from the middel to the corner
Now fold the Mulim so that the over hang on the "LONG" sides is just covering the inner staples that were used for the Speaker Cloth, Paying attention that the long fold is straight all the way along the back edge of the frame.

Now go to the other end and pull the Muslin tight and staple from the middel out to the sides leaving the staples around 2"apart But not pulling the muslim over tight, Once this is done now start the sides working from one end to the other making sure that as you staple the Muslim fold is around 5mm from the outside edge of the frame you wont need to "STRECH the MUSLIM" for the LONG sides at all.

Your DIY "Pro" Looking Corner Broad band Bass trap is finnished to enjoy...

I will Try to Attach the photos to there correct positions tomorrow (Unless "PROF" wants to do it) But hear they are for now all in one place Cheers.....

[cinema mad]

And the finnished Bass traps in place in the back...

I hope this helps in giving people the motivation to have A go and make some...

Cheers...

[Vaughan100]

Now it's measurement time !

Regards,

[Prof.]

Very good, detailed description Jason...and they turned out alright.
I'm sure your work will be of benefit for anyone contemplating building this type of trap..

I tried the flat panel approach with the large air space behind, for my traps the other night..
I think it did actually show some improvement, particularly in the detail of the lower register, but I only had enough Supertel to make the panels 4" thick..
I'll have to get some more, and try them at 6" thick...

I haven't had any luck in finding that grille cloth material..I'm afraid the female assistants at my local Spotlight have never heard of grille cloth...all they know are dress materials..

I'm still in the middle of re-modelling my theatre, and I'm using up the black stretch material I already had, for the acoustic panels..
I may not have enough to re-do the bass traps, so I'll take another look at it then..

[cinema mad]

Hi Prof,
Thanks for the kind Words..

Yes I went with 6" thick on the front corners floor to ceiling and 4" thick for the rear corners from rear riser to ceiling but I also have thick theatre woolen curtains from Jands Audio on the large rear window..

The larger the air gap behined the Broad band Bass traps and the thicker 4"-6" the more coefficent (Supertel Ultratel) they will be in the lower end frequency's thus why I went 690 wide with the front Traps...The air gap has an affect much like using 4"Fiberglass thickness in place of 8" thus saving $$$$ and quadrupling the coefficence of the bass trap in the low frequency's, in that they will obsorb even lower also....

When you inquired about the Speaker cloth at your Spotlight store did you give them the Part No??...

[Prof.]

cinema mad wrote:

Hi Prof,
Thanks for the kind Words..

Yes I went with 6" thick on the front corners floor to ceiling and 4" thick for the rear corners from rear riser to ceiling but I also have thick theatre woolen curtains from Jands Audio on the large rear window..

The larger the air gap behined the Broad band Bass traps and the thicker 4"-6" the more coefficent (Supertel Ultratel) they will be in the lower end frequency's thus why I went 690 wide with the front Traps...The air gap has an affect much like using 4"Fiberglass thickness in place of 8" thus saving $$$$ and quadrupling the coefficence of the bass trap in the low frequency's, in that they will obsorb even lower also....

Sorry Jason...I should have mentioned that the traps I changed were the rear ones..They were 6" thick, and right into the corners, but the're now 4" thick flat panels with an air space..
The front ones ( which are behind the screenwall ) are 6" thick, floor to ceiling and of the same type construction..flat panels..

When you inquired about the Speaker cloth at your Spotlight store did you give them the Part No??...

I've since contacted another branch and at least they know of speaker cloth..
I've given them the part no., but their computers were down at the time..so I've given them my number and I'm just waiting for a call back..

[Prof.]

Hi jason,

I've heard back from spotlight and they found the material from the part no.
Unfortunately it's only available from their Geelong store....I have no idea why other branches in major cities don't stock it..

It looks like if I ever need to get any of that material, I'll have to get it through your contact..

At the moment I have enough material to re-do the bass traps..and I've just started re-building them..

[cinema mad]

Hi Prof,

What A pain mate, If or when you need some Speaker grill Cloth The Guy you need to talk to's name is Scott in the Dress department Spotlight Geelong Vic as I mentioned in the other post. He offered to ship it to you when I spoke with him...
I think He got it in because of alot of requests so I don't think its A standard line that spotlight carry....

How is your Home theatre coming Along mate ??....

[Prof.]

cinema mad wrote:

Hi Prof,

What A pain mate, If or when you need some Speaker grill Cloth The Guy you need to talk to's name is Scott in the Dress department Spotlight Geelong Vic as I mentioned in the other post. He offered to ship it to you when I spoke with him...
I think He got it in because of alot of requests so I don't think its A standard line that spotlight carry...

.
Thanks jason..I'll keep that in mind..

How is your Home theatre coming Along mate ??....

VERY slowly!!..It's taking longer than I expected..
It's not so much the construction side, but the finishing of the timber panels that's taking the time..
I'm using plain MDF for the soffit trays and columns and I'm applying a timber grained finish to them, using special artists paints..
Each panel has three different applications to get the required timber grain colour and effect..and of course there's a long drying time between each application..

The timber moulding I'm using for the external framing of the acoustic panels is prepainted with a white finish (you may know the type of moulding I'm talking about..it's used for skirting boards ) and this is proving even more difficult and time consuming to change it to a timber grain finish...But I'm slowly getting there and they're turning out quite nice..

So far I've finished two columns, two frames and two acoustic panels..and the soffit trays are up..
I have two more columns,two frames and two acoustic panels to go..and then I start on the new lighting!!..

[cinema mad]

I had some spare time on my hands to make Another Broadband trap 2" thick ultratel, to be mounted on the ceiling in the front 1/3 of my home theatre in between and in front of the main speakers ...My plan was to hang the trap with a 2"-4" gap between the trap and ceiling...

Pictures and details to come...

Cheers....

[cinema mad]

I just finnished making and mounting for now A small BroadBand Ceiling mounted Trap for the Treatment of first reflection Point's, I will be making one lage BroadBand Trap for the Ceiling the size will be 2" 2400x800 W.. And more for the Side Walls, and Screen Wall will be treated with 2" Semi rigid fiberglass as well But I need to get more 1200x2400 sheets of Semi Rigid Fiberglass (CSR BradFord UltraTel)... I have already used 5 1200x2400 sheets of Ultratel

The BroadBand Trap for the first reflection points on the Ceiling for now is 2" thick 1200x750 Ultratel with A 3" air gap.. The BroadBand Traps to treat the First Reflection Points for side Wall's Will be 2" thick with A 2" to 3" air gap same as the one on the Ceiling....

I made the Frames with 42mm wide x 19mm thick Pine.. For Ceiling mounting the Trap I used Eye Screws 4mm OD X 40mm L screwed into each corner of the trap... Picture Hanging Wire 12Kg Strength for holding the trap 2" to 3" away from the Ceiling...
For Mounting the BroadBand Trap For the First Reflective Points I used Threaded Plastic Plaster inserts that I then Screwed more Eye Screws into...

I used The Mirror Technique to find the First reflection point of the front Main and Center Speakers to allow the correct Positioning of the Ceiling Trap's ....

After I finnish treating my Theatre with absorbers I am going to build custom accoustic WideBand Diffusor's IE, RPG's Diffractal DFR73, Diffraction-Grating Diffusors or something simpler like Primitive Root Diffuser's to be placed on the rear, side walls and rear wall, to further refine the sound quality in the room and help with my pacific ROOM MODES combined with BroadBand bass traps/ BroadBand Traps will treat the lower and higher frequency room modes....





















Hope this Gives you some Ideas for your own Build Cheers....

[Prof.]

Very nice work Jason....All those panels should help things considerably..

I used 70x19 pine ripped down to 55x19 for my frames, for the 2" Supertel..because mine are mounted directly onto the walls and I wanted a flat surface on the fronts of them..

What would we do without our Irwin clamps eh!! they're a great bit of gear..

I've used more "Wall-Mates" in my theatre than I can remember..I've even used them for the ceiling mounted projector..
I also found they work well for mounting the side surrounds, just using an eye screw and a right angle cup hook..
My surrounds weigh about 10Kg...and they hold very well..

Keep us up to date with your progress..

[cinema mad]

Hi Prof,
Yes the plaster inserts "Wall-Mates" are fantastic and provide A very strong anchor in plaster for many applications, It sounds like you have found many uses for them Prof ...

I should point out The 42mm x 19mm pine used for the frame is perfectly flush at the front with the Fiberglass due to the double layer of Acoustic cloth's tension but the fiberglass is around 8mm higher than the pine frame at the rear of the BroadBand Trap But the Muslin hides this....

Cheers....

[cinema mad]

Thought I would share my DIY Tuned Bass Trap Build... Note This Bass trap is usfull if you dont want to absorb High Frequency's but reflect Thus it is not A BroadBand trap and is aimed for lower frequency's absorbtion...

Just Finnished My first reflection for side walls x4 4'x2' and 2x 8'x2' & 1x 4'x2' for ceiling
I also built another bass trap with high frequency reflection Membrane to go between the corner BroadBand Bass Traps in the back of the room , It will go where the back wall and ceiling meet for added low frequency absorbtion performence.

I chose to use A tuned Bass Trap to stop high frequency absorbtion as I didnt want the room to dead...
Next I will be adding Diffusion to the room, I am going with three types...

1/ Advanced BroadBand QRD Based Nested Diffusing fractal 2'x4', 2x will be placed inbetween the first reflection absorbers on the side walls...
2/ Primitive Root Diffusors 3-7" Deep for rear side walls...
3/ Diffusing tiles placed on ceiling aimed at flutter echos, 25mm thick...

So far it took me two hours to calculate/design then test make 1 flutter echo tile from MDF but I need to use hard wood as the well gaps are very close together and when routing the wells, the MDF would split .... See close up picture of Diffusor Tile Prototype for Flutter Echo issue's

Any comments and suggestions are most welcome Cheers...

[Prof.]

Wow!! jason..you're really giving it the treatment!!

I wouldn't be overly concerned about it being too dead..
I thought the same thing when I started adding treatments to my room..and even trhough you can hear the deadness ( for want of a better description ) when I walk from the outside room into the theatre, it still sounds alive with sound when playing a movie..

cinema mad wrote:

3/ Diffusing tiles placed on ceiling aimed at flutter echos, 25mm thick...

What size are these diffusion tiles you're making, and how much of the ceiling area are you covering with them?
If they're are made from timber, wouldn't they tend to reflect rather than absorb sound?