box for two 18 BL's in a tahoe

[rcmobile 0]

what size box should i build for two 18's the BL's with 1600 rms each going to them.

i want to do i square port and subs facing up. dose anyone have any box plans i could use or ideas.

it is in the back without rear seats so i have room can go up to 48 wide.

thanks for any help

[tejcurrent 13]

I don't know what the difference is between the btl and bl for box recommendations, but I know the btls were 5-8cubes each with 12-16sqin of port per cubic foot, tuned between 30 and 35hz for daily driving. I'd shoot in those perameters. Look in the 'anyone running 2 18s' post for some pics and more info. When I find the plans from my boxes I'll put them up with the cut sheet if you want, but I think I'd tune a little lower.

Do you want one box for both subs or two seperate boxes? Do you go to comps, because my boxes are a little over the window line and that is not good for some comps. what kind of music do you listen to? Are you willing to sacrifice the rear of your tahoe entirely?

[tejcurrent 13]

I don't know what the difference is between the btl and bl for box recommendations, but I know the btls were 5-8cubes each with 12-16sqin of port per cubic foot, tuned between 30 and 35hz for daily driving. I'd shoot in those perameters. Look in the 'anyone running 2 18s' post for some pics and more info. When I find the plans from my boxes I'll put them up with the cut sheet if you want, but I think I'd tune a little lower.

Do you want one box for both subs or two seperate boxes? Do you go to comps, because my boxes are a little over the window line and that is not good for some comps. what kind of music do you listen to? Are you willing to sacrifice the rear of your tahoe entirely?

[rcmobile 0]

hey thanks for getting back to me, i listed to lots of rap and rb. so tuned low is great.

i will go to some comps but not much so if it is a touch above window line im ok with it.

yes in one box

[tejcurrent 13]

I think if you made one box 48wx18hx42L you'll still have about 6 inches or so between the seats and the doors (You should probably measure that though). What year tahoe? I'm basing these numbers off my 99 yukon, so if yours is newer there might be a difference.

If you make your port 5" high across the bottom of the box, and the entire width of the box you'll get about 233sqin of port, which should be good.

I believe you'll want to make the port about 28" long to get a tuning freq of somewhere in the 32hz range, don't take my word on that yet let me run that through a few calculators first. (or if someone else could).

I believe you'll end up with a net around 14-14.25ft^3 after port and sub displacement, which at 7ft per sub that should be good, tuned around 32hz you should really get those lows good too.

again, let me check on those numbers this afternoon, I just figured that up real quick and I'd like to check the accuracy of my statement on the port length.

Hope this helps give you a general idea of the size though.

[Fi Car Audio 64]

Solid recommendation above, but Im getting about 22" of port after end correction for 32 Hz. With a 5" X 46.5" port and approx 6" of space between it and the back hatch (going from tejcurrent) it will load and most likely drop the tuning even lower (itll act as somewhat of a port extension). This is where some trial and error comes into play. Worst case with an extra 18" of port, youd be in the 26-27 range... which in most cases is too low of a tuning. But... like I said, some trial and error on port length might be in order since the port size and space between the back wall are so close (it will act like a 90 and a continuation of the port to a certain extent).

Thanks...

Scott

[rcmobile 0]

yes it is a 2003, i can go up to 36 deep and still be about 4 inches from the back hatch,

so after looking a few min ago, i can go 48 wide, 36-38 deep and 21 tall and be at window line.

just deeper puts me closer to the back hatch, would it be better to do a square port in the back middle? kinda like steve meade did?

thank you very much for the ideas and help

[rcmobile 0]

the 42 deep would fit but it would be not very much room at all between the back hatch and box

[tejcurrent 13]

Yesterday I wrote a very indepth and lengthy response, but because of poor internet connection and the time it took to write this lengthy post the connection timed out and I gave up for the night. This is the very brief replacement.

I'd listen to scott, 22" for your port. I'd do 48x21x36, and you sould be fine. I can make you a cut sheet if you want, just let me know. I don't have program to do this anymore because of computer problems, but I can make you up a sketch or something if you want. Good luck

[rcmobile 0]

ok that will work for a good starting point then i will built the box with that size, the box will be a little higher than 21 tall because to make a little more room i will make the side walls 21 then a double top baffle.

so my port from what you are saying will take up the whole bottom run but be only 22 inches deep

o that how many cubes will that be

thank you greatly for the help

[tejcurrent 13]

If you have a router and can bevel the inside edge of that port I'd make it more like 22.5 because my bit that rounds the edges takes off almost a 1/2inch. If you don't plan on doing that then you're fine with 22. The whole port is really just adding one more board to get the top of the port (in this case 46.5x22).

With the port 5"hx22dx46.5=

2.96cubes of port from the internal dimensions of 46.5x19.5x34.5=

18.1cubes internal gives you a net around

15.14, then just subtract the sub displacement and whatever bracing you decide to put in.

Too lazy to look up the bl displacement, but I figure the 2 subs is somewhere near 1/2ft, so that will leave you with about

14.5 after bracing. I'm sure I'm leaving something out, but that's a pretty close estimate imo.

I agree 100% on that double baffle, I said something about that in the post that messed up last night.

Go to the pic of my single btl box that faced back and look close at the surround- because of how bad it flexed with single baffle it actually would blow the rubber gasket out weird under high pressure-now that box had some flex.

Good luck, be sure to post some pics on how it goes!

[rcmobile 0]

thank you very much i will start on it tonight

[rcmobile 0]

well due to some after hours work i wont get to start till this weekend but i will take plenty of pics

[rcmobile 0]

been working too much but while i couldnt build i been asking around, i am ready to build in the morning but wanted to ask one more question if i make the port all the way across this bottom will the make any port noise being so big as just one port.

i am ready to get busy so i can be the next the break the mirror that FI's seem to break these days.

[tejcurrent 13]

I'm sorry I didn't quite understand what you meant, but I think you mean will you hear any noise from your port.

Because of the size of the port you really shouldn't have much/any audible port noise imo. Only box I ever had port noise in just had way too small a port area. I have ~230sqinches of port and when the rear doors are open and I'm looking right at it I can't hear any port noise-and since you'll have a little larger port you should be fine. I did router the edge of the port to bevel the edges, so if you can do this I would.

I think you'll be fine.

[tejcurrent 13]

I'm sorry I didn't quite understand what you meant, but I think you mean will you hear any noise from your port.

Because of the size of the port you really shouldn't have much/any audible port noise imo. Only box I ever had port noise in just had way too small a port area. I have ~230sqinches of port and when the rear doors are open and I'm looking right at it I can't hear any port noise-and since you'll have a little larger port you should be fine. I did router the edge of the port to bevel the edges, so if you can do this I would.

I think you'll be fine.

[rcmobile 0]

well that is what i wanted, i will finally start the build tomorrow

I'm sorry I didn't quite understand what you meant, but I think you mean will you hear any noise from your port.

Because of the size of the port you really shouldn't have much/any audible port noise imo. Only box I ever had port noise in just had way too small a port area. I have ~230sqinches of port and when the rear doors are open and I'm looking right at it I can't hear any port noise-and since you'll have a little larger port you should be fine. I did router the edge of the port to bevel the edges, so if you can do this I would.

I think you'll be fine.