many questions

[afrakes]

I've got a few questions all pertaining to a built I'm helping a buddy with. We are looking around the 5k power range over 2 15's ported or 2 12's in a 4th order. The vehicle is a 2009 BMW 335I sedan;

1. He is set on a trunk build as he needs his back seats, problem is there is a firewall between the back seats and the trunk. No ski hole, no nothing. If we don't port through the rear deck, will there be any bass in the cabin, or just all audible rattles?

2. If we do a 4th order, how hard is it to design a decent enclosure? I have built many ported/sealed boxes, but never tried my hands at a band pass box.

3. If designing a box myself will be too difficult, what's the going rate for a full design including cut sheets?

4. I have never done an external port (if we go through the rear deck). How hard is it to do this and get the rear deck cut out lined up with the port opening? Any tips/tricks?

5. If we port through the rear deck but go with a basic ported design, would subs up or subs back be best?

I'm sure I'm forgetting a couple questions, so more may be on the way, but as always, I appreciate any and all feedback.

[crw092782]

1) Yes there will be bass in the cabin. I was running 2 SA-12's in the back of my Cadillac Seville and it had a similar metal wall behind the seat. Still got plenty loud.

2) Most 4th orders on here are 2:1 or 3:1. This means that whatever your sealed total is, you need 2-3 times that for the ported area. This can make for some very large boxes when you are considering 2 15" subs. I don't know how big the trunk is but that might not fit.

3) Depends on who you go through. Many people on this site will help with design just for the love of the game. If you have the specs, you should be able to figure out the cut sheet.

[afrakes]

Ok great. If we do a 4th, it would be a pair of 12s. We've got about 7.5 cubes to work with if I do a double baffle all the way around. That's before.displacements. And the reason I ask about how much I should pay for a design is I need this to be quality the first time. I don't have the time or money to be building a bunch of boxes, so I'd rather pay for a high quality design from somebody who has been there, done that. And get it right the first time.

[afrakes]

Was thinking around 2.25 sealed and around 5 cubes ported (or a hair under) if we do a 4th, of course depending on the woofer selection he makes.

[Triticum Agricolam]

Double thickness walls anywhere but the baffle are just a waste of material and add needless weight IMHO. If you want more strength add more/better bracing.

[Aj11]

imo nothing sounds like a 4th. its allot harder but worth it! 2 12s in a forth ported up threw the deck will be devastating! the 15s might be just as loud and will be much easier to build.

i went threw the same issue a few weeks ago.

really wanted 2 15s mostly because i never owned 2 at a time. then i really wanted 2 12s in a forth... then 4 8s in a forth.

i finally made up my mind and went with one really really... really good 15. mostly to save a Lil space. all the amps batteries.. wires... deadner... takes up allot of room. if you take up your ewhole trunk with a box you need to plan for amps (NOT MOUNTED TO THE BOX!) and enough bats to handle that 5k. so your own planning first.

still wish i went with the 4 8s

[afrakes]

Lol thanks for the replies. Yeah my buddy was really jet set on 15's, we may go that route. And electrical is a whole other set of restrictions with questions coming later on that. (in the right section, of course )

new question, if we go 15s in a standard ported box, not ported through the rear deck, would it be beneficial to put subs up port back suv style, but have the woofers as close to the back seats as possible so they are basically firing through the rear deck?

[timc31610]

If you do subs up prepare for a lot of rattle. Sound deadener will be your friend. Also if you have speakers in your back deck you may damage them if the subs are directly under them.

[afrakes]

If you do subs up prepare for a lot of rattle. Sound deadener will be your friend. Also if you have speakers in your back deck you may damage them if the subs are directly under them.

no speakers in rear deck. And the reason I ask about placement of subs is the rear deck is deep enough that of the subs are all the way towards the back seats the entire cone area would be resting underneath the deck and wouldn't be pushing directly on the lid.

[timc31610]

The rear deck can rattle as much as the lid if not more. Just cover it in deadener on top and bottom and that should help.