shingdaz

I just purchased 46 FT of closed cell damping foam from Elemental designs...it comes @ 1/4" thick and has a very strong adhesive backing...it is a new product on the market, it is designed to block and dampen resonant freq's above 200HZ...it can be used on doors and floor panels as well.

I plan on multi-layering this material directly behind my door where my woofer sits, and even the entire door cavity...in return I expect to get a warmer~ dynamic~ sounding woofer, that has the same damping characteristics of an enclosed woofer. Currently regular damping materials such as Brown Bread etc only keep panels from vibrating in the lower 90HZ range...Mid-Woofers don't play that loud in that range...and most experience cone break-up in the upper 200HZ freq'...damping these reflective freq's from behind the woofer should greatly reduce the distortion value's, and actually increase the moving Mass weight of the woofer inside the Cabin.

extreme1

Closed cell foam is hardly anything new, I've been using as gasket material for speakers and woofers for 12 years.

JohnVroom

add the material a little at a time till you have a grip on its performance. The material may very well decrease output in the midrange in ways you will like... until you add to much and then the driver will sound dull and non dynamic.

You are correct in thinking there is more to life than Dyna/ brown/ bquiet (though dampening is VERY important since sheet-metal is so thin and resonant)

shingdaz

[/QB]


Actually too much is often never enough...the trick is to keep the surface behind the woofer solid for the lower freq's and absorbable for the higher ones since they scatter more easily...which is what the closed cell foam will do , somthing like the damping material Dynamat makes that is made of rubber, and feels like jello...that stuff is what absorbs the scattered upper freq's and keep them OFF THE WOOFER'S MEMBRANE.

JohnVroom

... the foam comment I made was if it was used to affect the backwave of the midrange... perhaps I was off point (sorry)

still I would listen to the system with the woofer rear chamber empty then stuff the cavity behind the woofer full of the foam, listen for the difference (also use an RTA with pink noise before and after using the same volume and EQ) and see how that product affects the woofers response.

shingdaz

I beg to differ, in this experiment I beleive I will definatley improve the sound of the woofer in the door....simply because it is over a much wider area insteas of just directly behind the woofer, such a s Dynamatt's dynasorb stuff. Placing fiber-fill behind the woofer will dampen the sound, but it will not be use-full much due to the window itself getting in t he way when it is drawn down. When a woofer plays a 200HZ tone that sound is reverberated through-out the entire interior surface of the door cavity, which in turn gives a tinny sound to an un-damped door...damping material seems to not only dampen the vibrating door frame, but in damping the Metal itself keeps the woofer from becoming transparent to bouncing waves from inside the cavity. If it is not quite unders-stood, it basically increases it's TONAL REFERENCES more efficiently, and plays more dynamically in the lower 100HZ freq-range, without the shrill tinny sound that most woofers produce in an undamped door.

JohnVroom

True, UNLESS he uses quite a bit, but it still may end up doing nothing well. If he layers it you will have an adhesive layer stuck to the foam layer (assuming it will stick at all) and that would be a constrained layer system... that might have value

shigdaz- you are pretty fast and loose with the acoustic terms and you are making some false assumptions in your 'technical' post. The benefits derived from a product may or may not be heard in a fully desirable way, and not for the reasons stated. Your assuming a result prior to purchase (based on product marketing) and you will find a world of partial truths there. The 1/4" foam will have negligible value under 2000 Hz and layering it may lower the affective range to 800 Hz (approximate values but not too far off I bet). Only a few products are scientifically measured (ASTM 423) to show their absorptive value at various frequencies, (ASTM E90) to show their value as a transmission loss product (sound block).

Note:
When talking about polyfill avoid using the word damping
Woofers can not produce shrill tinny sounds in metal unless they are midranges or tweeters (EDITr metal is rubbing against something)

If there was a way to target individual frequencies using polyfill life would be much easier (untill then EQ for you!).

Again, the only way to quantify your results is with an RTA through pink noise and volume matching. The only way to qualify your results is to volume match and listen to music (subjective).

shingdaz

Although my assumptions are only assumptions, non-the-less, it seems to me that what I'm trying to do has some people thinking it will cause my Woofer's output to become muffled?...how is that?..how do I loose [/COLOR]Tonal Accuracy?[COLOR=Black]by layering closed cell foam inside the entire cavity of my door? When placing Poly fill inside a woofer box,does this result in a degradable sound along certain freq ranges?...it definatly does not...and the poly fill is even directly behind the woofer itself...MID or MID-BASS.

And using an RTA to measure any difference in sound IS ABSOLUTLY REDICULOUS!!.. .An RTA can't differentiate TONAL BALANCES...it's like asking a dog to spot the differnt colours of a rainbow?...and dogs are colour blind. Has any-one here actaullay lined their entire door cavity with any damping material? other than just one layer?...if you havn't then your arguments are frivolous.

Dukk

In fact it most definitely can. In most 'woofer box' installs in a vehicle the degraded frequency range is above the crossed over response of the woofer though. However, once one moves into the midbass and midrange frequencies it is wise to experiment with both surface and volume damping as there is such a thing as 'too much'.

John and Dereck are two of very few people I personally would even begin to entertain as having an opinion on this topic that is worth debating. I personally do not know who you are or what you know but their points are certainly valid and worthy of consideration.

shingdaz

Well I have been a member of this forum for the last 2 years...most of my studies have been on Solid Facts>...what I do know is that Multi layer damping of the interior Door frame produces AUDIBLE RESULTS...this is not He she said ...theses are proven facts...Layering your door with multiple layers of brown bread or Dynamat...actaully increases the woofers ability to play louder at Certain Freq's without Diaphram Break-up....I expect to do the same with Closed cell foam also...