canuckerjay

Okay, I used to be into this stuff, and am getting back into it. But it's been a while, so please forgive the ignorance.

Going with 2 10" Type Rs in an 03 Altima. Alpine offers dimensions for both sealed and vented enclosures. I have read all kinds of stuff on this forum that discuss what kind of box to build, but it all seems to differ depending on so many variables.

So if someone could just recommend to me what to build in laymen's terms, I'd appreciate it.

The two subs are 2 ohms, powered by an Old School MTX Blue Thunder 300.2.
The Altima will be sound deadened. I plan on doing the big 3.
I listen to all kinds of music, but love rock and metal. But I don't want this to sound so consistently tight that bass guitar is lost or the odd time I play some nintendo music that it sux.

Help/thoughts/advice are greatly appreciated.

Lord Huggington

iTrader: (1)

You're confusing tightness with output.

Ported can sound just as tight as sealed and vice versa, but ported has more room for error.

Ported is +3dB at the tune, rolling off at -24dB per octave (an octave is 30-40Hz ETC). Sealed might roll off early (10's tend to) and/or lack low or high end response depending on the QTC.

Go ported if you know at which frequencies you want bass. Try to tune to the lowest frequency you'll be listening to the most often. If you listen to whatever that has lots of 30 Hz input, than the safe thing to do would be a 30Hz tune.

Sealed is much better with drivers that are designed for sealed boxes. If a sub is made for "sealed and ported", it's more or less designed for people who don't know what they want, they buy and then later ask what box they should use.

Go ported. If you can't build the box, there's lots of people who can. It should come out to 2-3 cubes @ 30-35 Hz.

If you want a design than tell us the useable dimensions.

Denonite

iTrader: (1)

Go ported, net internal volume of 2-2.5 cubic feet and tuned to 34-36hz...line the box with polyfill and use large enough ports to avoid port noise at near max output. Just for an fyi..an octave is a doubling or halving of a frequency ie. 20 to 40 hz, 1000 to 2000 hz, 4000 to 8000 hz etc...so remember that even if a ported box drops off at 24db/oct and is tuned to 36hz, that means it's about 24 dbs lower in output at 18hz...but you also get a 20-30 db boost in bass output due to transfer function within a typical vehicle which means you really don't have to worry about the drop off...you'll get plenty of low low bass if you need it.

canuckerjay

Thanks guys; much appreciated; especially the offer to help design.

I'm pretty handy and could build it myself; it's the design that I'd have issues with.

From the manual, Alpine posts the following dimensions for the vented enclosure for one sub:

Dimensions: 12.5" x 12.5" x 20.5"
Gross Internal Volume: 1.4 ft3
Vent Area (dimensions): 11 in2 (11" x 1")
Vent Length: 18.5"
Vent Displacement: 0.24 ft3
Net Internal Volume (Vb)*** 1.1 ft3
F3, ripple, Fb: 26Hz, 4.2dB, 35Hz


I'm wondering about that 20.5" -- a bit ginormous, no??

Lord Huggington

iTrader: (1)

Depending on what you're driving. You should use what you have available, which is usually what you can fit through the door/trunk/rear-seat (when folded). In a trunk, rear-fire would do best. You'd get more output if everything was firing into the cabin, but only if the trunk and cabin were sealed off from eachother, which means fiberglass ETC.

[quote]octave is a doubling or halving of a frequency ie. 20 to 40 hz, 1000 to 2000 hz, 4000 to 8000 hz[quote]

Thanks.

What's "nintendo music"?

Denonite

iTrader: (1)

you don't have to use their dimensions, what's important is the volume...so in this case, if you want to use Alpine's recommendation, then you would want approx 2.2 net cubic feet of volume (that's after the subwoofer, port and cross brace(s) displacement) for two of those subs. That means the box can be any dimensions that will fit your car, accomodate the sub's minimum dimensions (approx 10.5" diameter, and about 6" deep each), and be approx. 2.2 net cubic feet internally.