I wasted two and a half hours building a single 12" box and when I was all done it sounded perfect.

Lessons learned:
- equal distances to walls makes for bad sound
- sound deadener really helps
- slotted ports are easier to build
- 36hz is the perfect tunig frequency for a sedan


Liquid nail > * ----- I used the weatherproof one cuz it was only 60 cents more

1x12.5" slot is the same thing as a 4" diameter port



Super secret sound deadener (hint: it costs like 9$ for 100 sq ft and is cusiony and waterproof doubles as thermal insulation in its original aplication)



Same material triples as a wonderfull gasket for air tightness and doesnt lose compression like foam/caulk do.


Obsessive soldering



Obsessive sealing even around the terminals



sounds better than the box it replaced... BTW couldnt use the 25 degree angle because my amp is gonna be mounted on the side of the seat and the only way to modify the settings will be the passthrough. But I was thinking maybe I would put two removable triangles on either side to seal the sub against the seat...


weird facts - the sub manual calls for 1.75cuft ported to 41hz while the thelie small parameters optimize at 2.15cuft ported to 38hz

I built to 1.95gross, 1.80cuft net ported to 36hz (aproximately) because I like low bass.


Tomorrow: the fun of carpeting and amp rack construction.

 

my experience that particle board is good - but mdf is much denser and cuts, glues, and nails, screws alot easier....

 

I know & agree.. but the closest MDF is at home depot and thats like 25 minutes away and when you build a new sub box every week you dont have time for that. plus the longest side is only 24" and I cross braced it. I doubt a ~400wrms amp will be able flex enough to make me complain.

 

You know liquid nails breaks down over time? And for such a soldering freak....I'm surprised to see the wire nuts....

 

it will last the week it will take me to get tired of the box being tuned so low. My rock music sounds like gangsta rap and my gangsta rap sounds like an earthquake...

plus it doesnt break down any slower than wood glue and it about 100x as strong.


and I forgot to groove & glue the wire in on the top panel because I was being rushed by my damn wife.

 

Couple notes:

Your 'obsessively sealed box' isnt. MDF and particle board are very, very, porus. We were moving some sheets with a vacuum loader once, and you could pick up 3 or 4 sheets by putting vacuum to the top one. Vaccum at sea level can not exceed the equivalent of 14.7 psi, so your sub is capable of pushing air through it. You really should seal the box with resin or varnish. Carpet and glue won't to it. Overkill? Maybe, but its easy and cheap, and leakage will affect the overall Q, even in a ported box. I do like the gasket, though...a step many people leave out.

I've found a new wonder adhesive for box building. Its called PL Premium Polyurethane Construction Adhesive. Its like $3 a tube (big caulk sized tube) at Home Depot. This stuff will stick anything to anything, and guarantees that the glue will last longer than whatever you are sticking together.

I've got to echo the thumbs down on the wire nuts.

Just curious what you used to calculate the ideal box. I use Bassbox, and it often disagrees with the manufacturers specs. Usually, though, if you plot the manufacturers spec against the bassbox, there isn't much difference, and its usually based on what is each system considers 'ideal'. Bassbox tends to want smooth curves and low F3, while manufacturers often take into account the transfer function of the car, and give up F3 in favor of a hump in the 50-80hz range.

You have hit on another issue with ported boxes...cars have resonant peaks, that can play hell with tuning. When you're down here on the 8th, maybe we'll throw a 'test box' in your car...like a 10 in a small sealed box, for example, and run a frequency sweep to find the resonant frequency range of your car, and define the transfer function. This is definitely overkill, but somehow, I think you'd like to have that data

Toby

 

wires nuts, i was going to let that go.

 

Jesus christ you people go way over the top when building boxes. What ever happened to the 3/4" MDF wood held together with liquid nails and screw sealed with silicone.

 

A true freak would fiberglass the inside of the box.

 

You guys are seriously swayed by urban myths or peer pressure to make such a broad claim as plywood is "pourous" can anyone happen to supply the presure/release decay formula for plywood compared to MDF? I cant either but with common sense I am assure you that a single 250wrms 12" in a box < 2cu ft will not leak any significant amount of air though the "pourous" wood. Toby I would expect more from you

The walls are coated in insulation & LN, thats the most effort I'm willing to put forth until I find the perfect box.

The res freq or my car is 58hz with the seats in.

The lug nuts make it incredibly easy to remove the box when I have an install (unlike you shop owners I have to load every tool I'll need into my car alone with an inverter to run them) and again, at the low power output of my amp & sub there will be no significant leaking there either.

I use a TI-83 with lots of formulas programmed into it for box calculations and a little of the old noggin to put it all together. I used to use winISD but it disconnected me from my brain so I dont any more.

MDF is close to 30% heavier than plywood and since the box is sitting right over my rear wheels that doesnt make me happy.

I might give the polyurethane glue a try but I like quick and non-toxic fumes so I can throw it into my car faster which I doubt that can offer.

Bumpin Expo - I forgot the silicone so I just doubled up on LQN

but really I have to point out again that "porus" wood only become porous over a long period of time or under extreem air pressure.