epoxy resin vs polyester resin sealing inside subwoofer box

[mlstrass 5,000+ posts]

I wasn't really talking about how fast the driver forces air in and out of a vent (which is a wide open area, not was I was asking you to picture), I was mainly addressing structural integrity and sealed enclosures to discuss the principal idea here, MDF being porous or not. My guess is if you wanted to get into surface roughness, drag coefficients for the various types, and wind speed as it pertains to laminar air flow, you would still be a off a bit in your thinking.

I don't bother thinking //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif I build, test, and learn from that. Too many scientifice principles that make sense on paper, but don't transfer over to the real world when it comes to car audio.

Touching upon surface roughness I've done bare birch boxes and some coated with resin and sanded up to 1500grit and waxed. Sometimes you gain .1 - .2 on the meter and sometimes you don't. And you would never hear that little of a difference by ear...

 

[akadj 10+ year member]

Sometimes you gain .1 - .2 on the meter and sometimes you don't. And you would never hear that little of a difference by ear...

in my case as related to this thread you probably wouldn't want to hear it by ear cuz it sounds like garbage! box/wall is tuned to 60Hz 10 cuhes with a 220sq" port

 

[ciaonzo 5,000+ posts]

I don't bother thinking //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif I build, test, and learn from that. Too many scientifice principles that make sense on paper, but don't transfer over to the real world when it comes to car audio.
Touching upon surface roughness I've done bare birch boxes and some coated with resin and sanded up to 1500grit and waxed. Sometimes you gain .1 - .2 on the meter and sometimes you don't. And you would never hear that little of a difference by ear...

Yeah, I hear you. Trial and error is king. Myself, I probably wouldn't bother with much other than some sanding and a coat of resin inside for my applications. The glass in the corners is a great idea, too. Might try that next time.

 

[mlstrass 5,000+ posts]

Yeah, I hear you. Trial and error is king. Myself, I probably wouldn't bother with much other than some sanding and a coat of resin inside for my applications. The glass in the corners is a great idea, too. Might try that next time.

No reason to glass corners. If I wanted strength I'd add a small 45 wood glued in place. Of course that can help or hurt score also, but again nothing you'd hear...

 

[mlstrass 5,000+ posts]

in my case as related to this thread you probably wouldn't want to hear it by ear cuz it sounds like garbage! box/wall is tuned to 60Hz 10 cuhes with a 220sq" port

Ugh, I prefer loud musical set ups. I've played music with boxes/walls tuned around 42-43Hz and they still sounded fine. Not sure about 60Hz though....

 

[akadj 10+ year member]

Ugh, I prefer loud musical set ups. I've played music with boxes/walls tuned around 42-43Hz and they still sounded fine. Not sure about 60Hz though....

yeah this car is set up for spl only.. not daily driver.. and adding the resin is not for construction strength to keep the box together. . its glued, screwed, double layer wood, and has threaded steel rod for bracing.

 

[jackal28]

Just an FYI for all of you in hot states like Texas or those who intended on making a SEALED fiberglass enclosure. Do not use epoxy resin. Epoxy resin will begin to melt in the range of 135(slow cure)- 160 (fast cure) degrees unless you get high temperature resin which requires specific cure instructions, such-as oven curing. I learned of this AFTER I purchased two gallons of epoxy resin. I just wanted to save a few of those more fortunate souls. Yes, in Texas summer your car can reach these temperatures out in the sun. As for a sealed enclosure, it can reach up to 80 C or 176 F inside of the box due to heat from the magnet. I don't think that you want epoxy dripping on your subwoofer. Sorry, but you must use either Vinylester (my choice) or Polyester for a custom sealed enclosure. If you live in a colder state you can use Epoxy resin for a sealed enclosure, but only if you reverse the subwoofer (magnet out). I can't do this with my woofers as the design of the mounting ring does not allow it.

 

[hispls 5,000+ posts]

Yes, in Texas summer your car can reach these temperatures out in the sun.

I think the better solution would be to leave Texas. 176 is internal temperature of a cooked turkey, if your car is getting that hot you are literally in Hell.

Interesting info for a necro bump though. Thanks for sharing.

 

[audioholic 5,000+ posts]

MDF is porous, but there was/is a fundamental mistake being made in the logic in this old thread. The example of holding a vacuum to a sheet of mdf is not a valid comparison. When a speaker is operating inside an enclosure, its not trying to blow the enclosure up like a balloon, because half of the time its also trying to pull the enclosure inward. The speaker cone moves in and out, there is no suction being created like a vacuum produces. The mdf would need to be so porous that it would allow a noticeable amount of air to pass back and forth through it while the speaker is operating.

When you hold your hand over the mouth of a port, that wind you feel isn't air just blowing out, it is the same air particles being excited in both directions many times a second. An SPL competitor getting data from a meter might see some difference, your average enthusiast wouldn't be able to notice. And a change in meter readings would more likely be due to added rigidity of the enclosure which raises its resonant frequency similar to adding internal bracing.