how much deadner?

[Rudy 10+ year member]

Food for thought guys. When I get the new car I'll probably look into the tech more thoroughly. If I had to guess I would say that mass is doing 95% of the work or more and any other characteristics would have to be cost effective.
For the right car I'd probably pay double for the last five percent of efficiency, but not for my current bucket.

And based on the explanation posted above 5% is being very generous. It sounds like marketing b.s. to me on face value, but I'll yield to your guy's expertise for now since I've never had the opportunity to compare.

However, there's one inescapable thought that comes to mind. Deadener isn't designed to block sound, so if that is what makes you think it's working better you're using the wrong stuff from the get go.

If the resonant frequency with the added mass is sub- audible, who cares what portion of that sub-audible sound is converted to heat on a quantum level.

I'll shut up now because I know people sell the better product here and I agree it's a great product. (Just don't pee on my leg and tell me it's raining).

It's a better product (Butyl based products) because it's cleaner, more durable, less aromatic, easier to work with, and if it comes to it, easier to remove. These are the only valid selling points. I might not put asphalt into an expensive high end car for those reasons, then again maybe I would if I wanted to save a few bucks and it was MY car.. I certainly don't regret putting it in my Subaru. It works great!

I used to think the same thing - before I found ways to test the vibration damping performance of different materials AND started to measure shifts in resonant frequency as you add them to a panel. Viscoelastic constrained layer vibration damping is complicated. It's much more than just using a butyl based adhesive. A good vibration damper is a careful balance between adhesive formulation and the strength of the constraining layer. Butyl based roofing products are not much more effective than asphalt, but they are less likely to fail. A proper CLVED is approximately an order of magnitude more effective than the alternative. That kills the value proposition for anything else and makes questions of durability irrelevant.

It is absolutely true that extravagant marketing claims have added made things more difficult to understand. Describing the constraining layer as a heat sink is one of my favorites. It's also true that the performance shortcomings of inferior materials have been used as a justification for the overuse of good products. Aftermarket automotive is really the only market where vibration dampers are sold directly to consumers and it shows.

Adding mass as a general purpose vibration control mechanism is another case of taking a truth and twisting it to sell product. Adding mass lowers resonant frequency - if no other characteristics of the part are changed in the process. This can be a reasonable approach when you want to lower a part's resonant frequency to get it out of a narrow pass band, useful when one part of a machine is resonating at a frequency generated by an adjacent part of the machine. Not useful in a vehicle where the range of frequencies available cover the audible range. Adding enough mass to lower the resonant frequency out of the audible range requires an impractical amount of mass. The materials being discussed also stiffen the panel as you add them, causing an offsetting rise in resonant frequency.

I had a couple of less supported columns that failed the tap test when I applied one layer, with two they went from a pingy resonance to a thud, an exception to every rule I suppose.

The "tap test" is a good way to determine which areas of a panel, or which panels, need treatment. It's a terrible way to determine when a panel has been sufficiently treated. It's especially bad if you are tapping on the side of the panel you are treating since the material you are adding is also cushioning the impact of the tap. In any case, tapping will always excite the panel at its resonant frequency. Vibration dampers work by reducing the amplitude of the resonance. That doesn't mean that there isn't resonance, just that it is insignificant under the conditions to which the panel will exposed in use. All of this applies to vibration dampers. Since you need 10 times as much asphalt or butyl designed for other purposes, it's possible that you won't get any audible change until you have added multiple layers at full coverage.

 

[Databyter 10+ year member]

Good post Rudy,

I'm thinking of using the better stuff in back, where my sub is going to be aimed at. It's a rear firing 500 watt sub who's target is a hatchback. I imagine I'll need to work the door at minimum, and possibly the sub floor where my spare tires compartment is.

At any rate there are some good deals on the better quality material if you don't need it NOW. Lots of folks sell left overs or buy in bulk to save dollars and piece out what they don't need.

I'm surprised no-one has flamed me for using carpet padding yet lol. Mines the grunge job, but it's done with love and attention to detail, so it's gonna work anyway.

 

[audioholic 5,000+ posts]

Why would we flame you for using carpet padding?