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BEST Stuffing/Filling for Sealed Speaker Box?

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I know this topic has been discussed on countless websites over the years, but I'm so confused by all the conflicting arguments out there, and not having access to all these products here in South Africa makes things even more difficult.

 

I built a big ceiling cloud for my Atmos speakers (PRO-180RPC), overhead sound adsorption and lighting effects. Each speaker has its own sealed box within this cloud (see diagram below). Now I'm trying to figure out what absorption and/or filling to put inside these boxes. Each box is roughly 3.3 cubic ft. in volume.

 

I've set the crossover settings for my Atmos speakers to 80Hz, so we're not dealing with subwoofer level frequencies here. I need a solution that is suitable for a sealed enclosure from 80Hz - 23KHz.

 

I've read that the best stuffing would be Long Fiber Wool, however I cannot find this product in South Africa. The only remotely similar sounding product I could find is: Undyed Fibre – Karakul - http://woolcraft.co.za/shop/undyed-karakul/

 

And the only other product I can find here is Dacron stuffing (which I assume is normal pillow stuffing). I also have 25mm and 50mm thick mineral wool sheets left over from my acoustic treatment panels I built.

 

I also think I recently heard/read somewhere that Klipsch used a combination of Dacron and Long Fiber Wool in a recent speaker line, but I might have gotten this confused...

 

Please can I ask you guys to help figure the best way to dampen/fill these boxes, as I've invested a ton of time, work and money into these Atmos speakers, so I want to make sure I'm using the best material possible. Unfortunately I don't have the luxury of trying out different materials through trial and error, and I also can't measure the results etc. So it will just end up being a best effort.

 

Cloud-Layout---Option-3.thumb.jpg.8dba844751712a8385cc5d42ad189839.jpg

 

Speaker-Cloud-Build-Process-12.thumb.jpg.75b5081e03b47400b8a7c45c2625fc4e.jpg

 

Ceiling-Cloud-1.thumb.jpg.96074db051cf88092a15a0c1e4086ea3.jpg

 

Thank you.

 

Brendon

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  Try the internet for the wool. Should be able to source some. Check some diy speaker supply websites.

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Thanks for your input @Panelhead. I've searched high and low and even spoken to a few wool dealers in South Africa, and none of them are entirely sure what the audiophiles are referring to when they say Long Fiber Wool. The closest I could get to that here is the Karakul Wool I linked to above, but I don't know if this product would have the right acoustic characteristics. I did find this website last night: https://meniscusaudio.com/product/wool/ so at least now I know what it looks like, but this would require international shipping to South Africa. However if the outcome of this thread is that I should be using Long Fiber Wool, then I'll ask them what it would cost to send it to me.

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Per Dickason's "Loudspeaker Design Cookbook" Acousta-stuf is the best cabinet fill for the speakers that are designed to have it. Not all are. 

https://www.parts-express.com/acousta-stuf-polyfill-1-lb-bag-speaker-cabinet-sound-damping-material--260-317

It has a lobed fiber that reduces its density.

And second best was polyester fiberfil meant for pillows.  Its fibers (I think) are crinkled to reduce density. 

Can't tell from here, but you must have a superstore that carries that sort of thing. 

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I believe that both the bandwidth and the absorption for HD fiberglass is very much better than polyester stuffing. Melamine foam is extremely effective in absorbing especially at low frequencies. Little else does so well below 100Hz.

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Don't know it's the best......plan on using to fill my KG 5.5s before re assembly....Menards sells it for 3.99 a roll

 

George

IMG_20190915_170109.jpg

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make sure that you leave an open un damped volume from the bottom of the vent on up to the top of the upper woofer. You need this cavity to be fully resonant so the woofers can most effectively drive the vent into resonance. You can damp the bottom corners and the area above the top woofer solid with damping. You can line the walls with damping but you must leave a good sized cavity to be free to resonate. The woofers drive the vent into resonance then the vent loads the woofers at and just below the tuning frequency of the vent.

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Thank you all for your valuable input and assistance with this... I greatly appreciate your time and efforts.

 

On 9/15/2019 at 7:14 AM, Panelhead said:

  Try the internet for the wool. Should be able to source some. Check some diy speaker supply websites.

 

Yes, I managed to find this product: https://meniscusaudio.com/product/wool/, but would mean I need to import it myself. Which I'm happy to do if this is the best product to use for my application described in my original post. But I want to be sure this is the best product to use before I go to that length and expense. 

 

On 9/15/2019 at 10:38 PM, JohnA said:

Per Dickason's "Loudspeaker Design Cookbook" Acousta-stuf is the best cabinet fill for the speakers that are designed to have it. Not all are. 

 

I might be able to order from Parts Express if they deliver to South Africa, but I wonder how we would know if it's suitable for my cabinets... I'm not a speaker designer and didn't follow a very scientific process with these boxes... I just tried to make the boxes as big as possible since these speakers are designed for an infinite baffle as per Klipsch support... 🙂

 

On 9/15/2019 at 11:27 PM, moray james said:

I believe that both the bandwidth and the absorption for HD fiberglass is very much better than polyester stuffing. Melamine foam is extremely effective in absorbing especially at low frequencies. Little else does so well below 100Hz.

 

Yes, I've been reading a lot of this too... but I think fiberglass and Melamine foam that are suitable for this application are beyond my reach here in SA. Or I just don't know enough about these products. I don't really need anything below 100Hz as my Atmos speakers are crossed over at 80Hz anyway. 

 

On 9/16/2019 at 12:02 AM, oldred said:

Don't know it's the best......plan on using to fill my KG 5.5s before re assembly....Menards sells it for 3.99 a roll

 

 

We don't have this in South Africa unfortunately, but I'd be curious to hear how it works once you're done. 

 

On 9/16/2019 at 7:58 AM, moray james said:

make sure that you leave an open un damped volume from the bottom of the vent on up to the top of the upper woofer. You need this cavity to be fully resonant so the woofers can most effectively drive the vent into resonance. You can damp the bottom corners and the area above the top woofer solid with damping. You can line the walls with damping but you must leave a good sized cavity to be free to resonate. The woofers drive the vent into resonance then the vent loads the woofers at and just below the tuning frequency of the vent.

 

@moray james This is very interesting... I think I would have done something similar instinctively, but it is good that you drew my attention to this and gave me some very specific guidelines to work with. I assume the vent you are referring to is the port on a vertical standing floor standing speaker? I don't have any ports or vents in my design and the box is effectively lying on its front baffle orientation wise when comparing to a floor stander (see diagram in original post), as these speakers are on my ceiling. If you could describe the stuffing layout based on my speaker box orientation so that I don't get it wrong, I would greatly appreciate this. This is a sealed box btw.

 

Thank you all.

 

Brendon

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With a sealed box you can experiment with standard home insulation fiberglass or rockwook  (same thing) and experiment with the density of the stuffing. Start with a layer of stuffing on the walls then progress to adding a blanket layer across the area of the box behind the woofer, the idea here is that the blanket layer can move in the centre attached only at the side walls this will eat  up a considerable amount of back wave energy if things continue to improve sound wise then step up to fully but light stuffing then carry on to double that amount and see if things sound better or worse. If things sound better try half as much again. At some point you will not find an improvement but a regression simple for you to find a high point for performance this way quickly. I hope this helps.

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