Need advice on building a 4th order bandpass

[themachinist]

If the subwoofer manufacture says that a speaker has an f3 of 46 hz in a sealed enclosure will a 4th order bandpass enclosure play lower that that??? sorry if this is a dumb question

[cashmonkey38]

My advice is to go with someone like Ram Designs or a professional box designer so that its a design that will work. He will charge you for a design but he will give you a picture and a cut sheet so you can just make your cuts and assemble the box. If this is your first bandpass, I'd highly suggest having someone like Ram Designs or Bass Heads Ent. design you up a box. BHE is kind of backed up right now but you can email them nonetheless. I don't think Ryan at Ram Designs is backed up currently but I'm not sure.

You want to calculate the tuning to be higher than a normal bass reflex box. Typically, tuning on a bandpass 4th are in the mid to high 40s and even into the low 50s. Your low end response comes from the sealed chamber and your high end roll off comes from the ported chamber in a bandpas environment. I'd suggest looking into Aero ports since you're wanting to kind of port through the deck. id sound deaden like crazy on that shelf to avoid rattles as well.

Port area suggestions will vary if you search around the forum and you'll find much debate. if you had a 2:1 ratio and had 1 cubic for per sub sealed(2 cubes total) you'd get 4 cubes ported. If you wanted to tune at say... 48Hz, I'd do two 6" aero ports. After port displacement is where you want your 4 cubic feet net(and subs depending on if you wanted them in the ported or sealed chamber). 2 ports that are 6" diameter and for 4 cubic feet would need to be JUST a little over 12" long. That should be enough port to avoid any kind of noise and perform well.

Alright thanks for that, so at the moment I have a design right now that's got 1 cu of space for each sub in separate chambers for the sealed section, subs will be facing with magnets in the ported section so have that done out accounting for displacement of subs and bracing, only thing is I haven't factored in is port displacement because I don't know much much port area I need and therefore length. At least 12" and probably more of port will be outside of the box so I was thinking of doing one big port up out and into the dash. I have WinISD at home so I'll see if I can figure out how to get some info off that tonight, how much would it usually cost to have someone design this type of box?

[CortezDTV]

If the subwoofer manufacture says that a speaker has an f3 of 46 hz in a sealed enclosure will a 4th order bandpass enclosure play lower that that??? sorry if this is a dumb question

4th orders play low tune to 48

I've had mine up to 55 hz and I would still play into the low 30s high 20s

I miss my 4th

And nice car; bitch of a trunk to actually get loud I had been living in a trunk like that for a long time

[CortezDTV]

2 12s hmmm

I'd do

2 sealed 6 ported

Tune to 48 put the 2 6" areos thru the speaker holes

If ur a badass make them 8" ports lol

[Joe X]

Your rear deck is somewhat obstructed in that vehicle, you are going to need a lot of port area to reach the rear deck and still tune in the upper 40s.

[CortezDTV]

Somewhat obstructed is almost a understatement

That shit is solid

Only car ever to be regularly tested for rear impacts at 70mph

[cashmonkey38]

Yeah it will be a separate job but I'm going to look into it, what do you think the minimum port area should be? From there I can figure if it's feasible to make larger and longer

[cashmonkey38]

Bump

[CortezDTV]

As big as you can fit

Look at build log

I cut the entire back deck out re welded a shape I could use

If I was you I would do 2 8" ports thru the speaker holes in the rear the is the least amount of cutting

If you don't want to cut your doing to be stuck with 2 6" areos thru the rear deck speakers

There is really no other option

If your armrest has a blowthru you can do a ski hole style, it works but rear deck in that car is just kinda a better option

I had 2 15s 4th order

3 cues sealed 7~8 ported

187" or port tuned high to 55 it would still tear it up down low even into the 20s

I didn't give a fuck, lesser subs would have crumpled under that amount of power (AB 750.1 at .35 iirc. Clamped 3300 each sub)

I did loose a surround once but that was with n2s and due to the fact that I had a 2x4 across the top I my box because I was too lazy to use metal

[CortezDTV]

To give u an idea

http://s121.photobucket.com/user/SC1975Silent/media/2012-05-11_17-01-00_810-1.jpg.html

Edit I clamped 3300 each sub when I had 2 dc 5ks

Totally forgot!!!