Help With Enclosure for Single Treo 15

[323toslow]

Hey all, new here to the forums, and somewhat new to subwoofer enclosure building. Im working on some plans for an enclosure for the trunk of my e46 323i, but keep seeing conflicting information concerning port area per cubic foot. 

My audio equipment: Treo TSX 15” dual 4 ohm wired at 2 ohms and fed by an RE Audio DTS1000.1 (amp spec sheet says 560w @ 2ohms @ 14.4v)

My enclosure idea: 3.52 net cubic feet, subwoofer firing toward the rear end, and two 4” diameter aero ports tuned to 32hz pushing air through the “ski pass” hole behind my rear seat arm rest.

Torres box calculator shows with this specific setup that the total port area will be 25”sq with 7”sq port area per foot.

Is this feasible for a 15” subwoofer?

[323toslow]

Anyone? Any non negative input is welcomed and greatly appreciated. 

[Joe X]

Your box specs are fine for this sub but not for many others, the only thing to point out is that the way you intend to setup the box you will get the most output from the ports and not from the subs so you will get loud around 32Hz and rather silent above (and below) that.

[323toslow]

1 hour ago, Joe X said:

Your box specs are fine for this sub but not for many others, the only thing to point out is that the way you intend to setup the box you will get the most output from the ports and not from the subs so you will get loud around 32Hz and rather silent above (and below) that.

You said fine for this sub but not many others. What do you mean by that? Is it because manufacturer spec sheet for the sub says 2.5cubes? I like learning.

Is the reason it would only be loud at the tuned frequency of 32hz because the speaker is firing towards the rear and the ports toward the front?

 

[Joe X]

When porting through something a bandpass enclosure is best because the port carries the full bandwidth of the enclosure, not so in a ported box.

The sub handles low power and can work in very small enclosures, many of the subs used on here will have greater port area requirements/ power handling, most of them are not recommended for use below 3 net but your sub does, don't need to worry about this, it will work fine on the specs you have set.

[323toslow]

Ok. So when you say “porting through something” are you referring to the fact that it has to push air from my trunk forward into the cabin versus say a hatchback that doesnt have a “trunk” that is sectioned off from the cabin?

My biggest reason for the design of this enclosure being like this is i had a borrowed treo 15 dual 4ohm that was only running on one coil with a1.2k watt amp (i didnt know one channel of my amp was burnt) about ten years ago. If im remembering correctly the guy said it was a 3.5cube box (i never measured it  ) but it had a straight slot port not an L, that was about 3” wide and I think he said it was tuned to 35hz. Now, it was in my hatchback and it hit so hard with whatever music I played (late 80’s early 90’s gangster rap, heavy metal like Pantera). The song Shedding Skin by Pantera at 24 seconds in there is a low note that hangs for atleast 10 seconds and in my hatchback we thought it was going to pop the rear window out. Got 132db on an spl meter at the passenger side dashboard. I know that was a hatchback and my car now is a sedan, but I really want to mimic that pound I remember that got me hooked on a single Treo 15” years ago. Im kind of stuck with aero ports with a box this size in my current vehicle. If I had fold down back seats it would be slot port all the way since I would be able to get a larger gross cubic foot box into the trunk.

I really appreciate the feedback!

[Joe X]

Hatchbacks are among the best vehicles to get loud, and since you can't fold down the rear seats you are going to have a harder time to get what you want.

I was referring to your ski hole, if you were able to fold down the rear seats it would be so much easier, people with your problem can either open up the rear deck and build a conventional box or as I was saying building a 4th order bandpass to get all the output to the cabin without any obstacles.

[323toslow]

Im definitely going to research the 4th order bandpass setup. I have several months before we can start building and currently my 15 is jammed in a prefab  2.5 net cube at 44hz and holding me over for now. From what i’ve read about bandpass boxes already, building one seems a little intimidating.

But it might be the only way I can go since I would like to keep the vehicle looking stock. 

I greatly appreciate your feedback thank you!

[323toslow]

So i've been playing with Sketchup and came up with the following design if I decide against a bandpass box. How does this look? Is the inner port wall to long and/or to close to the magnet to be an efficient ported enclosure?

3.5cu.ft. Net , 17" Height X 28" Width X 21-9/32" Depth

Port: 15-1/2" Height X 3-1/2" Width X 29-3/64" Length

Port Area: 54.25in^2

Port Area Per Foot: 15.49in^2

Torres Calculator shows Fb = 33.64hz but WinISD shows Fb= 35hz

A question for you Joe X, I see in WinISD the volume drop for my particular setup from 34hz and lower, and also the drop from 38hz and higher. What is it that makes it drop there? Shouldn't my TSX15 be able to rumble good below 34hz? Is this just a characteristic of the woofer's parameters, or strictly the box or both?

[Joe X]

Plots below are for a 3.5 net @ 34 Hz box and the TSX 15":

The first plot should be similar to what you see on WinISD, the bump you see around tuning is a result of the port action on output, your also see that you output sharply drops  below tuning, this sharp drop is a result of the ported enclosure system not the driver.

 

 

Inside a car and as a consequence of cabin gain you get something like this roughly: 

 

 

You get to play 25Hz about as loud as 50Hz, thanks to cabin gain you can listen to rap and such properly.

On the calculators since WinISD is not compatible with slot ports you can just dismiss the result, Torres has it's own problems but in this case actual tuning will be closer to what Torres says.