Bandpass 100 sq in Port in a Sedan! New Pics on #2

[P-rez]

Nice...more pics!!!

[AmericanLegend]

From what I was told I should do a 4th order for my 15'' DC xl like 1.5-2cubes sealed side because that is the small part of a 4th order. and 3-4cubes depending on how i did my sealed side for the ported side. That is after all displacement as well. I would port it to something around 55-60hz and hope that it likes between 25-40ish hz..

I'm very curious as to how this box is going to perform for you tho considering it is totally different from anything i've seen done in the 4th orders.. The sealed side being 6cubes.. Idk I would be worried about blowing up those subs if your box is gonna be 10.5 cubes with most of it being sealed. Just my .02

You're right, bro. It's the am and I'm about to do work, so that's something I need to consider.

We're only running 1500 watts rms to the subs and they are still super stiff after a year of play in a 4.5 cubic foot-ish prefab. I don't think this amp really gives them the beans. Still, I don't want to blow them because, for some reason, they hit Hard!

I using ISD, I calculated the response if I shrunk the sealed side (that I'm about to build) to 4.5 cubic feet. It shows the box peaking at 49 hz or so, up 3db from reference. Here is the response plot:

Relative

Freq Gain SPL

[Hz] [dB] [dB]

20.00 -21.61 78.40

25.00 -16.56 83.45

30.00 -11.81 88.20

35.00 -7.03 92.98

40.00 -2.06 97.95

45.00 2.30 102.31

50.00 3.45 103.46

55.00 2.20 102.21

60.00 0.94 100.95

65.00 0.14 100.15

70.00 -0.28 99.73

75.00 -0.41 99.60

80.00 -0.31 99.70

As you can see, it makes 103.46db in free field with only 1 watt at 49.

[AmericanLegend]

Nice...more pics!!!

Thanks! And here are the rest of the ones I shot yesterday. As I build today I'll try to remember to take pics.

As you can see, the trim piece butts exactly up to the box. That makes it like a double baffle on the port side of the box. Im going to put some fiber fill on that inside of the box where you cant see it to give it a little damping i think.

[AmericanLegend]

Okay so I'm thinking about shrinking the ratio down to 1:1 to not blow the subs. The subs laugh at this amp and I know how to set gains, so do you still think they would have a problem in a 1:1.33 ratio?

The plot for a 1:1 show it peaking at 49 hz and dropping off from there. This box needs to play some low bass. The 9 cubic foot ported box catches the 1:1 bandpass at 34.52 hz. I would like for there to be more of a low bass advantage and tuning it lower doesnt seem to help at all, mostly take away from the upper bass (only down .28 db at 80hz).

The 1:1.33 box, however, has a signicant advantage over the ported box all the way down to 28hz.

[REaudioBuff]

let someone else chime in on that ratio cause im not sure what to tell you there but i'll give ya whatever advice i can lol. Looks good so far!

[AmericanLegend]

I didn't get much done today. Smoothed the port a little plus made the sealed box in the back. It is 5.14 cubic feet internal which is close to the 4.5 in the front. Getting it in there was a real pain and I even had to cut it in half to make it fit. Tomorrow, I have to cut the holes and put the sealed box together in the trunk. There are a couple small indentions I need to cut onto it also to make it fit properly.

Here's a question for some the SPL guys: If the box peaks at 49 hz free field, how much will being the car lower the peak response now that it's sealed off?

Nobody wants to see thes few pics, so I'll just upload them tomorrow...

[STEvil]

sealed side is the small side, ported side is the big side...

When I modeled it on the computer, it made more bass over more frequencies this way. Will it sound bad or something this way??

Depends on the sub. Some work ok in giant sealed boxes... some just flop around. I would suggest looking up sealed box specs for your sub from the manufacturer to see if you're near the recommended range.

[loudNlow87]

Nice looking car, waiting to see some more pics!!

Why does everyone go so crazy over this ratio thing? Tune one to spec and the other however you'd like..

You do know a 4th order bandpass has only 1 ported chamber right?

There is no way to "tune one to spec and the other however you'd like" since its a sealed chamber firing into a ported chamber.

Should learn the simple difference between 4th order and 6th order before telling people how or what to do.

Sorry, I should have chosen different wording. "Build" the sealed chamber to spec and "tune" the other to your liking. I know what a 4th order is. Twas just a simple suggestion, not 'telling' him what to do. Be easy...

[AmericanLegend]

sealed side is the small side, ported side is the big side...

When I modeled it on the computer, it made more bass over more frequencies this way. Will it sound bad or something this way??

Depends on the sub. Some work ok in giant sealed boxes... some just flop around. I would suggest looking up sealed box specs for your sub from the manufacturer to see if you're near the recommended range.

The sealed factory specs call for 2.2 cubes per sub. I'm at 5.14 before the subs on the sealed side 4.5 on the ported side wit 100 square inches of vent....

[STEvil]

thats not so bad then i guess. Could be a bit bigger on the ported side, but smaller just gives you a bit more power handling capability (not that its a huge issue with a 4th order).

Might want to put some filler in the sealed side and mount the subs inverted though, then you can smell the motors if they get hot