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polyfill for small box what for a big


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cutlass013 
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Posted: October 17, 2006 at 4:11 PM / IP Logged  
i think my box is over sized and my subs are inverted would polyfill help me in that area too? just wondering if it wouldnt what is some suggestion that are cost effective
Flakman 
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Posted: October 17, 2006 at 4:47 PM / IP Logged  

Polyfill makes the box seem larger than it is. It causes the sound waves to slow down as they move through and around the fibers of the polyfill. This would only make your situation worse if your box is too big already.

I would glue and screw some layers of MDF inside the box. This would make it easy to figure out how much space you are taking up and would effectively reduce the internal volume of your box. Just make sure they are glued together well and glued solidly to the inside of your box. This would also help to brace walls that may be too big, if necessary.

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wvsquirrel 
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Posted: October 17, 2006 at 5:33 PM / IP Logged  
Exactly. Use polyfill to make a small enclosure perform like a larger one. Install bracing/baffles to make a larger enclosure smaller.
I hope you switched the phase on those subs if you mounted them inverted. If there isn't a switch on your amp to switch 180 degrees then switch the + and -.
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haemphyst 
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Posted: October 17, 2006 at 6:11 PM / IP Logged  
wvsquirrel wrote:
I hope you switched the phase on those subs if you mounted them inverted. If there isn't a switch on your amp to switch 180 degrees then switch the + and -.
Won't matter... Just because the woofers are inverted, that does NOT mean you have to reverse the phase. If you only invert one, then yes, you would invert the phase on the one woofer only, but it all depends on the overall system. For example, my crossover will allow me to actually adjust the phase of my woofers to ANY degree of lead or lag, to match (blend) the mid-bass in the doors. As long as they are in phase with each other, then it is not mandatory to reverse the phase, and in some cases it can actually improve mid-bass blending to reverse the phase anyway.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
forbidden 
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Posted: October 17, 2006 at 6:30 PM / IP Logged  

Do not confuse electrically out of phase with acoustically out of phase as those are two totally different things.

Electrically out of phase is best desribed as two subs and one is wired out of phase to the other. Thus if one sub is inverted, it needs to be wired out of phase to bring it back in phase with the other speaker again.

Acoustically out of phase, which the post may have eluded to and Dave may have overlooked, means that the drivers are now wired out of phase with the balance of the speakers in the system, being the front and rears. Some vehicles perform better when they are wired acoustically out of phase, others do not. Some cd players and amplifiers also have a built in 180 degree phase adjustment that does this very thing so that one does not have to rewire the subs being used. In some cases it may have drastic effects on the tonal response, in other cases you will be pressed to hear it.

As far as making a box smaller with the least amount of work, take some closed cell styrofoam and duct tape it real real good. This will help to make it air tight and extremely light as compared to blocks of MDF etc. Hot glue the blocks of styrofoam into place.

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wvsquirrel 
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Posted: October 17, 2006 at 6:40 PM / IP Logged  
Thanks Rob, you explained it a lot better then I ever could have.
Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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cutlass013 
Copper - Posts: 95
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Posted: October 17, 2006 at 10:12 PM / IP Logged  
thanx i will check it out and see what happens

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