Mortite/Rope Caulk for Cabinet Deadening

[HIPCHECK]

cheap cabinet deadening

well i have found a thread im right at home in. i have used almost all of these items in my current car audio install. lots of "peel and seal" 2 dynamat kits (free) and some oem style sound panels. these oem style sound panels are very thick,and adhesive backed. you can get them at sherwin williams paint store that carries automotive products. (6) 1ft2 panels is around $25.00 last time i bought one. perfect for inside treatment or sandwich construction on a mini sub.

i am also fond of using the 40mm pvc rubber used in lining showers and tubs in home construction. this is great for sound proofing cars. i use some stainless steel to seal up all the holes in the trunk and behind the seat, then line with the pvc rubber around the back deck/rear seat. same with the door openings, seal with metal, apply dynamat, foam, and a layer of pvc rubber.

pro sound proofing for pennies!

 

[sdclc126]

Yes rubber is something I've considered before too. Living in a large city there is a rubber products store near me, that I have used for different projects (non-audio) on my car.

They will custom cut sheets of it for you, your choice of type and thickness. Then you just glue the sheets on. That would be far easier than clay.

 

[noah katz]

"Out of curiosity, why not apply resin to the wood and then just press the batting to it. Why do you want hard resin on the surface, it would seem to just cause internal reflections and not absorb the waves. Am I missing something here?"

Constrained layer damping works by shearing (when you bend a panel, there are shear deflections in the inner layers which try to make them slide against each other) a thin viscoelastic layer between two stiff surfaces.

If it's all solid, the panel is stiffer but with much less damping.

Commercial stuff is sheet metal with a layer of viscoelastic adhesive.

 

[nunayafb]

If it's all solid, the panel is stiffer but with much less damping.

Let me clarify, You said attach the batting with liquid nails I said replace the liquid nail with the resin, same thing, basically. I was not referring to solid batting. If I remember correctly to transmit vibrations with minimum losses(MDF->batting) you need an adhesive as close in hardness to the mdf. The reason you want this is that the batting is more efficient at convert the acoustic energy into heat than the wood, the wood is a more efficient converter back into sound(panel resonance).

I believe the electrical analogy holds here: To achieve maximum power transfer the resistance of the load and source should be equal. the load is the batting and the source is the wood from one side and air from the other. How crucial? Dont know, hopefully someone has tested it on here.

You were planning on applying resing to the inside of the batting (away from the wall), this is similar to what is sometimes done for room treatments. The method utilizes some layers of dampening material(fibrous) and some thin and firm layers(wood, plastic, etc.)the sound impacts the firm layer causing motion and resonance and the fibrous layers absorb this energy and convert it to heat, dampening the frim layer. The important part of this sandwhich is that the firm layer is isolated from direct air contact or it causes reflections and almost negates the rest of the assembly.

From the original poster

was wondering if anyone has ever used this stuff to completely line the inside of a speaker cabinet to damp resonances?
Would it work? Is it practical? Cost effective? Would you still need to address standing waves, etc. with stuffing?

He wants to address standing waves and is referencing speaker cabinets as opposed to sub cabs, so im assuming he is referring to
stuffing/damping the mains, and this is why I recommended against the layer of resin inside the batting

 

[sdclc126]

"He wants to address standing waves and is referencing speaker cabinets as opposed to sub cabs, so im assuming he is referring to stuffing/damping the mains, and this is why I recommended against the layer of resin inside the batting."

Thanks - I was actually referring to damping vibrations in any cabinet, with caulk, clay, rubber, etc. Then I was asking if acoustic stuffing would still be required (in addition to the damping material) to absorb standing waves. I'm assuming it is, as I doubt "exotic" damping materials would also be anechoic.

I guess you want speaker/sub cabs to be both mechanically inert and anechoic - two different properties I think. So what do they make anechoic chambers out of, where they test speakers and drivers? Should we be endeavoring to make our cabinets as miniature anechoic chambers, or is that what we're doing already?

 

[nunayafb]

Then I was asking if acoustic stuffing would still be required (in addition to the damping material) to absorb standing waves.

For subs no, for everything else yes. The frequencies in sub cabs are too long of a wavelength and it is virtually impossible if not actually impossible to prevent standing waves or reflections. The higher the frequency the easier to stop.

 

[noah katz]

"Let me clarify, You said attach the batting with liquid nails I said replace the liquid nail with the resin, same thing, basically. I was not referring to solid batting. If I remember correctly to transmit vibrations with minimum losses(MDF->batting) you need an adhesive as close in hardness to the mdf. The reason you want this is that the batting is more efficient at convert the acoustic energy into heat than the wood, the wood is a more efficient converter back into sound(panel resonance)."

Apparently we're not talking about the same thing. When did batting enter the discussion?

Anyway, the discussion was about damping panel vibrations to minimize their radiated output, not about absorbing sound in the enclosure.

For which, liquid nails and resin are very different; the former is relatively low stiffness and lossy, resin is hard. IOW one is damping and the other is structure.

As for subs, stuffing is valuable to get an effective enclosure volume increase by absorbing the heat of compression.

I got about 20% (theoretical limit is 40% for the molecular composition of air) on my last sub.

 

[nunayafb]

When did batting enter the discussion?

apparently never!!!! I saw fiberglass cloth and my brain swapped in batting which is sometimes used for this app. Sorry

As for subs, stuffing is valuable to get an effective enclosure volume increase by absorbing the heat of compression.

Good point I forgot about that, got too focused on waves and resonance and neglected the other purposes.

For which, liquid nails and resin are very different; the former is relatively low stiffness and lossy, resin is hard. IOW one is damping and the other is structure.

I see what you are thinking now, hopefully. The plan is to bond a hard layer to the inside of the box via a flexible and lossy adhesive so that when the sound wave hits the glass it loses alot of its energy trying to pass through the liquid nails right?

This is getting me thinking. What if you attach a veneer or some other thin impermeable material to some type of batting/stuffing (sorry noah) so that it is basically a box inside a box. This would be similar to literally placing a box within the main enclosure and seperating them by sand. I wonder how the former would compare in damping out resonance to the sand filled enclosure.
Anyone heard of this? It sure would be alot lighter.

 

[noah katz]

"The plan is to bond a hard layer to the inside of the box via a flexible and lossy adhesive so that when the sound wave hits the glass it loses alot of its energy trying to pass through the liquid nails right?"

You're getting closer.

The adhesive isn't intended to be a barrier, although it might act like one a little bit.

Now that we're on the same page, re-read what I said about constrained layer damping.

A box within a box might work pretty good.

But it might introduce other problems, like diffraction from the drivers, which are now recessed.

 

[nunayafb]

A box within a box might work pretty good.

But it might introduce other problems, like diffraction from the drivers, which are now recessed.

The inside on is only a 5-sided box, or has large relief holes so as not to interfere with airflow from the speakers which are mounted on the baffle as normal. The baffle needs some other form of damping- extra thick, sand filled(separately) etc.

As far as constrained layer dampening, Im going to have to do some research on that until then im going to leave it be.

Thanks for your patience, I'le tri adn raed beter necks tyme

 

[noah katz]

"As far as constrained layer dampening, Im going to have to do some research on that until then im going to leave it be. "

It's not that hard.

Just think of how the pages of a phone book slide against each other when you take a handful and bend them.

 

[Pano]

From what I've read and seen illustrated about constrained layer dampening, one of the factors in its acoustic attenuation is the change in the speed of sound between each layer.

In other words, each time the sound passes from one material to the next, the speed of the wave will change, since the speed of sound is different in various types of material. Each change in speed will result in a net loss of energy.

Materials with different speed indexes sandwiched together will obviously produce the largest speed change, thus the largest energy loss.

That is outside the different resonant or absorptive properties of each material, which is a whole other matter.

 

[noah katz]

Where did you read that?

Sounds like the questionable speculation I read a lot of in audio.

It's true that energy transfer is inhibited at impedance discontinuities.

But I think it's speculation that it has anything to do with minimizing cabinet vibrations.

 

[quickshift]

Just thinking out loud... If certain types of material resonate or transmit sound at certain frequencies, if you layer up materials that don't transmit / resonate in the same range next to each other, would that dampen the cabinets effectivly?

I'm most of the way through building some little curved 2 ways ATM, they are built on an MDF skeleton skinned with bendy 4mm hardboard but lined with the following layers.

(0utside)
2 x fibreglass
1 x 2mm cork sheet
1 x fibreglass
1 x sand and fibreglass resin mixture
1 x fibreglass
1 x latex rubber

If I place my hand on the inside surface and knock on the outside, there is a lot less vibration compared to just MDF. I'll pop up some pics this weekend when they are finished.

 

[Pano]

Where did you read that?

Oh Crickey, Noah. Now you're asking the hard questions.
It was in a book or 2 about acoustics that I read years ago in Europe.

The effect was also given to explain why sand makes such a dead sonic panel; it will lose a lot of energy. If the energy must pass from grain to grain to grain, it will lose energy each time.

Makes one think that sand and lead shot could work well...

 

[noah katz]

"The effect was also given to explain why sand makes such a dead sonic panel; it will lose a lot of energy. If the energy must pass from grain to grain to grain, it will lose energy each time."

That makes sense. What I read said it was due to the friction between the grains dissipating energy.

I guess both are factors.

 

[Pano]

What I read said it was due to the friction between the grains dissipating energy.

I would think that the friction would be the biggest loss.
But if you could mix materials with different sound speeds, that might be best.

The speed of sound in glass is very high, in rubber and lead, very low (for a solid). Might give some ideas for a deadening material.

 

[critofur]

Even the difference between Aluminum and Steel is significant enough to do this quite effectively. Try making a laminate of one sheet of each bonded by a viscous adhesive and you'll find it to be quite "dead".