fiberglassing the inside of the box

if i fiberglass the inside of my box dos that make the inside more reflective to the sound waves. iv heard of people doing it in there spl boxes but dos it do something that would be good for a street setup and sould i put fb on the inside and cover it up with soundproofing or sould i gust do the fb and then use polly fill. the outside has bine fg. thanks here is a pic


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Actually the main reason most installers use resin on the inside of the box is to seal the porus nature of the MDF most enclosures are made of. It helps assure the box is as sealed as it can be.

I would argue the "relfective properties" of resin on the inside of a box helping the performance of the box. Sounds like someone trying to be more knowledgeable than they really are.

Rob

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MECP Sales/Install
IASCA/NACA/CAN Cert. Install & SQ judge

If it were such a good idea to have "reflected sound" in a sub box, who would by Polyfil?  You really don't normally want reflected sound in a box, do you?

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Michael

that was the other part of the conversation iw as just going to let "be" LOL.... Most boxes today are too small.. so the reflective principle, while acoustically flawed, would also defeat the purpose for todays smaller enclosures... good point.

ROb

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MECP Sales/Install
IASCA/NACA/CAN Cert. Install & SQ judge

the purpose of filling a box is to reduce the possibility of destructive interference. if the sound is able to reflect freely in a box strong enough it may bounce back and hit the back of the speaker, causing it to distort. the resin put on the inside of boxes seals the wood keeping it from breathing. the less the wood breaths, the stronger the suspension of the box,the more power the speaker can handle.

interesting way to put it... not picking it apart, just hoping to clarify...

I just reread your post for the 5th time.. I think I got what you were trying to say... You are refering to using Poly fill... the Poly fill simply slows the back wave as it moves from the speaker, to the reflecting surfaces (the walls of the box) by slowing the wave you trick the speaker into thinking the boxis larger than it is & you reduce the possibiliry of a standing wave. This is why in the current world of big woofer/small box (no crude jokes please) the polyfill concept is important to understand corectly. 1 lb per cu ft is claimed, in theory, to be worth .10 cu ft increase in the woofer's percieved net enclosure volume. Example: 1 cu ft enclosure with 1 lb of polyfill appears to the woofer to be an enclosure of 1.1 cuft. the volume of the box didn't change, the wave timing from the speakerto the reflectec surface back to the woofer changed. Think like sonar/depth finders in the ocean.

there is no way to elminate the wave returning to the speaker, nor would you want to. that is part of the suspension action of the speaker & is needed for the speaker to work properly. Otherwise we would be adding a difusing baffle of some type to sheild the back of the speaker in all enclosure deisgns to block the back wave from the speaker.

& yes, as I said above, the resin seals the pourus material we choose to build thes boxes out of... Especially if using Particle Board instead of MDF.

the less the wood breaths, the stronger the suspension of the box,the more power the speaker can handle. while this is true as a PART of the equation, I would hate for people to suddenly think that sealing the box better is a sole contributor to better power handling. It is a component to better speaker control, which means less speaker distortion, & thus better voice coil alignment, which helps with power handling & speaker life... to be more specific.

Hope that makes sense... a technical topic is hard to break down into easy terms sometimes.

Rob

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MECP Sales/Install
IASCA/NACA/CAN Cert. Install & SQ judge

that was perfict thanks

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Want to know some good equipment- JL,Adire Audio,Mcintosh,Brax,Helix,Eclipse,JBL,RE,Dimoand Audio,Zapco, pritty much anything DYhon,Forbidden recommend
On the12volt you give some info and you get in