Home Theater Forum and Systems banner

141 - 160 of 175 Posts

·
Registered
Joined
·
193 Posts
Discussion Starter #141
Looking good Eric, I like the way you have your diffusors layed out also the cherry stain looks very nice :T..

I replied to your post in my Mealstrom Subwoofer thread over at the AVS forum about your Diffusors and room acoustics, did you see it ??...

Yes you are spot on with your thoughts about the Abffusors and how they work....

Cheers....
 

·
Registered
Joined
·
193 Posts
Discussion Starter #142
Had A chance to install the Rigid fiberglass/ absorbtion membrane inc setting the pre determined air gap between the Back of the ply & front of fiberglass ...

The ultratel Fiberglass was cut A little to big and hangs out A bit but I dont mined the Muslin keeps it set in place and stops the glass fibers becoming airborn...

The reason I chose Muslin as opposed to Ply is because,
1: so the Absorbtion cf of the Abffusor will be higher due to the open back
2: Keep the weight down :bigsmile:....

Couple of pictures of the SLOW progress Just need to Paint the steel frame and rivet it together

Cheers....
 

Attachments

·
Registered
Joined
·
193 Posts
Discussion Starter #143
Well I Spray painted the metal outer frame matt black using A new product: Dulux Quit Rust Water Based Gloss Enamel with Urethane but the paint did'nt stick :hissyfit:...

Initally I was very happy with the way the outer frame came up straight off the spray gun (3 coats)
I left it for 6 days to dry but the paint didn't stick, thus wasted my time...

This paint is A Primer and paint in one with 7 years of protection to all metal surfaces..

When I first opened the one LT can of Matt black paint it had seperated as expected so I went to stir it but the primer down the bottom of the can was rock hard and near impossible to mix..
I went back to Bunnings and showed the guy who sold it to me, he then checked 2 other cans off the shelf but they were all the same so he attempted to mixed all three cans on there electric mixer and tipped all three cans into one and gave me that..

But obviously half of the primer was left in the bottom of the can's due to not mixing in with the paint, So there's your problem :unbelievable:

Before painting I preped the 1mm cold rolled steel by bead blasting with Glass beads then whiped over throughly with prepsol, This is the class 1 standard to prepair the metal surface and remove scale for painting and what Dulux recommends...

I am going to get A price on powder coating :bigsmile: and attempt to get my $32 clams back off bunnings...

Check out the paint job...

Cheers...
 

Attachments

·
HTS Senior Moderator
Joined
·
8,367 Posts
That looks nice Jason..It's a pity that the paint didn't stick..
You certainly did all the right preparation..
A "one off" powder coated job probably won't be cheap, but it will give a nice professional finish to the frames..
 

·
Registered
Joined
·
193 Posts
Discussion Starter #145
Actualy to get the metal frame powder coated costs around $50 in satin black so not to bad, I have to build 2 more of these Abffusors 3 total for my back wall so $150 for powder coating...

As they say you learn by your mistakes,

Cheers....
 

·
Registered
Joined
·
193 Posts
Discussion Starter #146 (Edited)
I draged my first Abffusor into my theatre and placed it in the middle of the back wall while I watched The Day The Earth Stood Still on Blu-Ray to see how it performed..

To tell you the truth I could'nt really notice much differance But once I build the other 2 and place them all against the rear wall mid hight with 6" thick bass traps under neath and QRD flutter Echo tiles placed Horizontaly on top of the Abffusors I am sure it will aid in the Acoustic performance of my theatre...

My standard room Dimentions are very good (R Walker BBC/ Pass) no integer multipule within 5% Pass according to the room mode calc, I am Thinking of trying/striving with help from Acoustisofts RplusD Modal Analyzer For Dolby's optimum ratios for film & music room/ an RT60 of 242ms...
Is this worth trying for??

Absorbtion to Achieve ITU/EBU Control Room Recommended 198ms RT60:443 Sabins

To help with Room modes I Have been looking at using A Helmholtz Resonator Mainly because They can be tuned for very low room modes & I can use my front Riser as the chamber and have A very low Q thus larger bandwidth:

According to the Room Mode Calc My room modes Dominate between 30Hz to 118Hz :
I will be taking realtime measurments to get A more precise idea of the modes..

The most dominant are: Axial 30.2Hz, Axial 47.1Hz 35.8%)

Tangential 55.9Hz 15.7%) Axial 70.6Hz 14.1%) Tangential 76.6Hz 7.8%

This is what I have come up with :
Helmholtz Dimentions: H:40cm W:130cm D:120cm
Specs:
Port length: 2cm
Port Diameter: 100cm
Volume:624lt
F res: 67.83
Q: .79
Bandwidth: 85.64Hz
F low:25.01Hz
F high 110.65Hz

Any advice and Suggestions would be greatly Appreciated..

Some pics of the Abffusor in the theatre

Cheers....
 

Attachments

·
Registered
Joined
·
1,405 Posts
My standard room Dimentions are very good (R Walker BBC/ Pass) no integer multipule within 5% Pass according to the room mode calc, I am Thinking of trying/striving with help from Acoustisofts RplusD Modal Analyzer For Dolby's optimum ratios for film & music room/ an RT60 of 242ms...
Is this worth trying for??
242ms is low for a listening room but it can depend on the speakers, source, and at what volume level you are listening to. For very high quality sources such as blu-ray I think that a lower RT60 would be good to shoot for, but your ears must tell you what sounds right. You might have a conversation with someone in the room and see if it is comfortable since your room dimentions effecting <200 Hz is in good shape. I have found that maintaining a balance of symmetry is very critical. If you decide to use Helmholtz Resonators (usually in rooms +30' or so in a direction I think) it can be helpful to have two instead of one. They sometimes take some trial and error to get right more than most treatments. I like the new treatments. :T
 

·
Registered
Joined
·
193 Posts
Discussion Starter #148
Thanks thewire for taking the time to post what you have experienced and pointing them out , I see your using A helmholtz rasonator at the front of your room :T....

I was thinking of only using one larger helmholtz resonator in the left front riser to the above diamiter, but I can use both my left and right front risers if I need to to keep things balanced....

Cheers....
 

·
Registered
Joined
·
193 Posts
Discussion Starter #149
I have been playing with the RT60 app in Acoustisofts RplusD & ran A few sweeps in the main listning position "subs only", but I know that you need to run the RT60 with main speakers & subs together when taking readings....

I need A decent calibrated mic instead of my standard ECM8000 mic but good enough for now untill I am ready to do the final tuning of the theatre...

I did notice that the real time analysis reconfirmed the big room modes from 47hz down like the room Mode calc predicted, But I am hoping to rectify the lower frequency room modes with one large or two
smaller HelmHoltz Resonator(s)..
1x large tuning: Volume 624lt,, Q.79, bandwidth of 85.64Hz , F,low 20-25Hz , F High 110Hz
hopfully this will work but either way I will get there with much persistence...


Also Has any one read Floyd Toole's book: Sound Reproduction: The Acoustics & Psychoucoustics of Loudspeakers & Rooms ?? I just ordered it.. Kevin Haskins said it is A must read as well as S Linkwitz...

Here is A croped RT60 graph of the subs running only, Subs crossed over at 80Hz...


Cheers :T...
 

Attachments

·
Registered
Joined
·
193 Posts
Discussion Starter #150 (Edited)
Just picked up Floyd E. Tooles new book today: Sound Reproduction, Loudspeakers & Rooms, Looks like A good bit of usefull easy to understand info in it but its $80au ...

Also I was chatting to one of Australia's room acoustic experts and he seemed to favour the idea of the use of Helmholtz Resonator for treating the lower model region in certin applications hopefully my situation :praying:, also pointed out A few ideas for bass traps that reach A little lower than the 3.0pcf (48Kg/m3 fiberglass 6" broadband bass traps I built that are only realy good down to around 100Hz when corner mounted...

So I am going to modify my rear Broadband bass traps and see how it sound & performs after running R+D...
It cost's another $150au for the extra membrane but there is none in my state so its A 2 week wait... If it works well I will be sure to post the build....


Cheers...
 

·
HTS Senior Moderator
Joined
·
8,367 Posts
Just picked up Floyd E. Tooles new book today: Sound Reproduction, Loudspeakers & Rooms, Looks like A good bit of usefull easy to understand info in it but its $80au ...

Also I was chatting to one of Australia's room acoustic experts and he seemed to favour the idea of the use of Helmholtz Resonator for treating the lower model region in certin applications hopefully my situation :praying:, also pointed out A few ideas for bass traps that reach A little lower than the 6.0pcf fiberglass 6" broadband bass traps I built that are only realy good down to around 100Hz when corner mounted...

So I am going to modify my rear Broadband bass traps and see how it sound & performs after running R+D...
It cost's another $150au for the extra membrane but there is none in my state so its A 2 week wait... If it works well I will be sure to post the build....


Cheers...
Jason...Is this something that fits over an existing bass trap, or a completely new design?
 

·
Registered
Joined
·
193 Posts
Discussion Starter #152
Hi Prof, yes it is/can be intergrated into the existing Bass Trap....

I have the membrane on order but its A 2 week wait...

Cheers....
 

·
Registered
Joined
·
335 Posts
cinema mad said:
A few ideas for bass traps that reach A little lower than the 6.0pcf fiberglass 6" broadband bass traps I built that are only realy good down to around 100Hz when corner mounted...
I would have thought 6" thick fiberglass would be capable of reaching down quite a bit lower than 100 Hz (more like 80 Hz or slightly below that especially if using an air gap). But this guy is an acoustic expert so who am I to argue ?

Regards,
 

·
Registered
Joined
·
193 Posts
Discussion Starter #154
Hi Vaughan100 thanks for taking the time to post..

Yes I do have A big air gap especially for my front broadband bass traps and that is A must to get decent performance out of this type of absorber IE: 3x50mm 48Kq/m3 or 3cf fiberglass, But the reality remains while 6" may absorb A little down at 80hz the further up in frequency say 250Hz the more it will obsorb.. Even Broadband absorbers have an effective bandwidth (Q) that tapers off either side of that... Also the less the thickness the greater directional attenuation can accure, so I believe Ref (Floyed E Toole).....

So the thicker the fiberglass the lower it will absorb but also every time you add thickness say after 100mm & then double that to 200mm the less difference it makes compared from going from 50mm to 100mm in thickness...

Cheers....
 

·
Registered
Joined
·
78 Posts
Hi All,
I have been watching this post for some time now, Most of the info has been very informative, I am currently working on my humble Home cinema room, I like many others am having a few problems with the acoustics, I am in the process of drawing up a floor plan of my room with the hope that you guys and gals can help out.

Regards Peter
 

·
Registered
Joined
·
193 Posts
Discussion Starter #156
Hi Peter,

I am sure that you will fined plenty of help on this forum mate, we are all hear to help each other where we can ..

I started this thread to show & share my ideas about building my own acoustic treatments in the hope that others would fined it useful and also share what they have come up with ...

Cheers....
 

·
Registered
Joined
·
193 Posts
Discussion Starter #157
I am still waiting on my membrane so no progress has been made with my rear bass traps :waiting:
But hope I will have it next week at the latest...

Cheers....
 

·
Registered
Joined
·
193 Posts
Discussion Starter #158 (Edited)
Last week I finally recieved the Quietel 130kg M3 fiberglass boards From CSR Bradfords, By adding Quietel it will extend the low frequency absorption of the rear corner mounted Broadband bass traps..
Unfortunately the Quietel only comes in A max thickness of 25mm (1") 2400x1200 x2 per pack :crying: as apposed to ultratel 48Kg M3 50mm 2400x1200 x3 per pack..

I just doubled up the Quietel to 50mm and added it to the rear of the existing 100mm 4" of Ultratel, so making A total of 150mm "6" thick bass traps for the rear wall corners...

Also I changed all my first reflection absorption panels (ultratel) from 50mm 2" to 100mm 4" thick
so as to obtain more "even" absorption for Mid & High frequencys, Floyd Toole's new book points out the importance of this..

I also re plastered the theatre's ceiling with one layer 10mm dry wall and only used 4 can lights this time as apposed to 8 and enclosed all 4 liqhts in MDF boxes sealed with Acoustic silicon placed in the roof cavity..

To further reduce my 4 Subwoofers decay time/ ringing I installed CSR Bradford sound screen plus 120mm thick in the ceiling cavity above the theatre wall to wall inc over the side wall cavitys paying attention that the acoustic batts were cut to insure A tight fit between the joists, also doubled it up 240mm thick directly above where the 4 corner mounted Broadband bass traps are..
The difference this made was immediate watching Bolt on blu-ray the bass was just so tight punchy and detailed...

At the moment I am fine tuning A helmholtz resinator placed in A high pressure zone to help smooth out the room modes,
Then the last thing I am doing with the room acoustics :daydream: is finishing my other 13 prime seed QRD abffusor for the rear wall :waiting:: So the back wall layout will have 7" deep QRD Diffusor/ 4" thick Absorbtion in the middel/ QRD Diffusor...

Cheers..
A couple pics..
 

Attachments

·
Registered
Joined
·
509 Posts
go cinemamad! I'm rootin for ya.

will be going thru this thread again soon, picking your brains as it were.

Just finished my speaker build, and have begun experimenting with room treatments. Our local spotlight does not have anything really that looks like grill cloth (for any treatments), so will grab the details from the geelong store you mentioned, they should be able to get it in..fingers crossed.

I do think I will lean quite heavily towards diffusion rather than absorption. Strictly two channel here, you must be into HT with a name like that yeah!! ha ha

not to steal your thread, but this pic might be good for light entertainment!



Remember the old tip to just throw an unopened bag of f/glass in the corner and see? Well, I did that, and more! just hung the raw batts with string, quick and good for testing purposes.

Pretty heavily did the front of the room, very good results. But, I now get the feel of how easy it would be to overtrap, so will have lot's of diffusion.

, throwing a few raw batts on the wall is only a couple of hours work (even tho I have to use an extension ladder!), but it is not so easy to test diffusion and find out is it.

"let's see, just where are those diffusors I just happen to have laying around??"





anyway, thanks for your thread
 

·
Registered
Joined
·
193 Posts
Discussion Starter #160
Hi Terry J, Very nice speakers you have there mate, what Model/Brand are they ?? I love my 2 channel as well but more into HT now...

As far as the speaker grill cloth, Scott from spotlight Geelong will ship it to you no prob's, $10au to ship AU wide I think...

Cheers Terry
Hope to see more pictures & idea's of what you end up coming up with mate...
 
141 - 160 of 175 Posts
Top