OP will probably need a truckload of reticulated foam.
More on trying to damp an entire wall: https://gearspace.com/board/bass-tr...rray-massive-damping-measurements-inside.html
It can work, but you should take care not to completely kill the spaciousness for upper frequencies. You might need a rigid perforated wall on top of the damping so that you can get back some reflections for mids/highs.
Right, in theory need to build the horn/room as a ~sealed compartment as if it's a mobile audio app, then add damped vents to ideally bleed off any unwanted excess low end 'cabin' gain with of course enough damping to reduce exterior noise to below local code levels and of course the room proper will need considerable damping to quell room/horn modes, reflections.
My SWAG is that it will probably require at least a much lower tuning, which in turn increases damping requirements, so got a sneaking suspension it will be a 'dog chasing its tail' scenario unless the local codes are either fairly lax and/or it will be a 'looooong' way to the nearest 'neighbors'. That, or some sort of an active system.
My SWAG is that it will probably require at least a much lower tuning, which in turn increases damping requirements, so got a sneaking suspension it will be a 'dog chasing its tail' scenario unless the local codes are either fairly lax and/or it will be a 'looooong' way to the nearest 'neighbors'. That, or some sort of an active system.
My money is still on the rigid Owens-Corning 70x series being of valuable service. Maybe my reference is too old -- maybe somebody else bought 'em, or the product was found to be carcinogenic? (probably by the state of California . . 😉)
Cheers
edit: nope, just checked - they still offer it!
Cheers
edit: nope, just checked - they still offer it!
Agreed, TTBOMK I've used/recommended the 700 series duct board since its inception due to Altec switching to it and no longer recommending regular in-wall fiberglass insulation. Another advantage Vs the in-wall is that one doesn't need nearly as much for a given speaker design, though need to use washer head nails to hold it without compressing it: http://web.archive.org/web/20150930063454im_/http://www.soundsclassic.com/altec820inside.jpg
As far as I can tell, the recycled denim insulation has better absorption in the low frequencies than glass or rock wool. Of course it's much more expensive.
It's worrth a look at the data, although the charts don't go very low.
It's worrth a look at the data, although the charts don't go very low.
For a given thickness? Seems like it would need to be in the form of a stretched panel; speaking of which, I just remembered that for rooms, the norm for VLF is full wall size ~spring loaded mounting clipped panel absorbers with the one system I've seen used dual 1" MDF to do 16 Hz, so pretty sure these others are strictly for the speech BW - up, at least IME with fiberglass and its replacements.
For thinner thicknesses, the rockwool does more, but you can use more of the denim before hitting a literal "wall" before the sound wave just bounces doesn't penetrate any further into the absorption media, compared to rockwool.
Yes, for a given thickness the cotton seems to absorb more at lower frequencies. It measures flatter than glass or mineral wool.
@GM I've read a lot about the mechanical traps for bass, seen photos, but don't remember actually seeing one in person.
Most literature says that bass is very hard to block or absorb, so making a dead wall for bass isn't going to be easy. I suspect that if you asked 5 acoustic engineers, you'd get 6 answers. 🙂
Most literature says that bass is very hard to block or absorb, so making a dead wall for bass isn't going to be easy. I suspect that if you asked 5 acoustic engineers, you'd get 6 answers. 🙂
If you have something mechanical in front of the poly fill rock ‘n’ roll Owens Corning product etc. like a thin rubber membrane, semi permeable not unlike a dialysis artificial kidney or an reverse osmosis membrane but more mass loaded butyl yet thin??to knockdown the girth or the strength (so to speak, but in the idea of waveform ) for bass frequencies before they get into the poly fill etc. and then a A boubce off to the very end (hopefully now abbreviated so it’s only a foot or two, maybe 4 feet deep ?) with gaps in between to get creative with Materials in and on the way out hopefully it’s not enough left to get through the rubber membrane now attenuated through all of the series of things including the first hit?
True as I learned the hard way when the ceiling caved in, though seems like with a sprung wall air/whatever gapped to the outside adobe wall that's a significant portion of, or better yet, a whole WL of the horn's fundamental would then only require a layer of whatever air gapped/attached to it to absorb the ~250 Hz-up BW.
The more I think about it.......I wasn't allowed to copy any part of any of the plant's technical library, but can't think of a reason ATM why this 'exercise' can't be viewed as a vertically oriented oscillating power tool isolated from the floor, or in my case, all manner of electrical power, controls structures, cabinets isolated/damped to meet various seismic, shipboard, etc., vibrations up to, and including detonations, so the math is out there, just no clue where to find it other than corporate/classified mil-spec docs nor how to use it [I had an EE doc to do all my 'heavy lifting' math].
might be a logical fallacy or incorrect thinking on my part but if your "in the horn" and it's exit is terminated in a "perfect absorber" isn't the net gain zero?? or am i offside??
I love the idea. I too am up late with speaker ideas. It's one if the things that makes life exciting and rich. I sure hope you build this! I wanted to share my experience. Reading about the quality of horn bass, I built a folded front horn. Sim was great, measurements matched Sim, except for some squiggles presumably from the folds/poor transitions. Outdoors it sounded amazing. I set it up right in front of me firing right at me. The back of the room is very deep with 5 bags of Rockwool 1 foot from The back wall. I dialed in crossover and listening was a huge disappointment. It was fine, but not as good as my 2 12" overdamped sealed subs. Output capability was insane, but quality was not. I'm not sure if that's worth much because I am not a horn expert at all, and I can't even explain why it disappointed me, but my lesson was that eliminating the room problems by achieving directivity didn't work out. Now you will have much more heroic absorption, and be in the horn, so maybe my experience is not relevant. The same sub moved to the theater with a second to even things out gives better bass there than it did directed right at me. It's almost as if the room modes were necessary if the room couldn't be eliminated entirely (ie, outdoors). I'd love to get Earl Geddes input on that, he seems to have a good understanding of room modes and bass in rooms. I wish you the best and I'm excited to see it. Craig