Jump to content
midnightE39

I did something wrong with my box. SSD15

Recommended Posts

So I built a 3 cube box (net) tuned to 31 hz for a new, Fi SSD15 with standard options.

port area is 34 in^2

sub up, port back. slot port, 11.5h x 3w x 24d

box is 13h x 32w x 20d.

11 sq inches of port per cubic foot of the internal enclosure volume.

I'm getting great low end, but the output begins to drop sharply at 55hz, being hardly noticeable at 65hz. I did a tone sweep and the output drops off sharply between 55-65hz, picks back up a little bit in the 70's until it begins to roll off around 90hz where i have my crossover set.

My old pair of kicker cvr 12's hit this range wonderfully tuned at 40hz in the same car.

I think my box and port are the wrong sizes. ive watched my subwoofer as it attempts to play this range, I've been told i just may be experiencing an exaggerated low end, but I don't think this is the case, as I have observed the subwoofer attempt to play notes in these trouble zones and it doesn't seem to move right when it tries.

I have extensively read over these forums and I cannot seem to find anyone with any similar problems. I've used winISD and it tells me that my response curve should be covering these areas, unless I didn't use the software correctly.

I've wondered that since this problem zone is at double the tuning frequency of the enclosure where the woofer cone should be moving most of all (as opposed to at vent tuning, where it moves least? tell me if i'm wrong) Would this indicate that the pressure inside the box at this frequency range is preventing the cone from moving the way that it should be? because that's what it looks and sounds like is happening.

how does an L shaped port affect tuning?

does this make sense? could the wrong port size relative to the box size create enough back pressure on the woofer cone to cancel out frequencies?

some insight would be appreciated.

EDIT: just realized, the port is 3 inches wide all the way through, it extends 4 inches into an L shape, but the width is only 3 inches throughout, leaving only 3 inches from the back of the box. Is this too small of a space for the air to try to push through? I figured I was supposed to keep the port width consistent all the way through.

Edited by midnightE39

Share this post


Link to post
Share on other sites

Your port area is very small. I would definitely add more port area. Box size seems pretty small. Idk the box recommendations for the ssd though.

When you tune low like 31hz, the high bass like 55hz and up will not be as loud as if the box were tuned to 40hz.

If you want I can design you a box. I can make a 3d sketch up and a cut sheet for you so you know it will be built right.

Share this post


Link to post
Share on other sites

that would be great. but i thought when you tune lower, it means you'll get faster response at the expense of overall SPL. This is not correct? 3-4 cubes @ 33hz is what Fi recommends for the SSD15.

 

this is a rough sketch of what i have to work with. 

 

e39trunkdimensions.jpg

 

How much of a difference would a 35 hz tune make? I was planning to go up to 35-36hz I often hear that is the "sweet spot".  when i was using WinISD, it showed that lower tuning would just give me a flatter response, not that i would lose any. the way it is right now, 45hz is where my bass peaks (cabin gain?). I just want widest frequency range I can get out of a ported box.

Edited by midnightE39

Share this post


Link to post
Share on other sites

looks like im aiming for a box around 3.8 cubes tuned at 35hz, WinISD projects that if i do this, and i add 2 db @ 80hz with a q factor of 1. I'll see very good response.

Share this post


Link to post
Share on other sites

It's called cabin gain.

 

If your box has a flat response, it won't past the ~60hz range due to inefficient gains in the environment.

Share this post


Link to post
Share on other sites

Good luck, it is hard to get the bass up front in that car. I have had the best luck porting through the ski pass.

Share this post


Link to post
Share on other sites

Good luck, it is hard to get the bass up front in that car. I have had the best luck porting through the ski pass.

 

do you mean walling off, or do you mean just building a box with the port aimed forward through the ski hole?

 

also it used to hit this range well with 2 kicker cvr 12s @ 40hz i do think my box isn't allowing enough excursion after watching it during a tone sweep.

Share this post


Link to post
Share on other sites

You need to build a closed rear chambered bandpass and port it thru the ski hole

Share this post


Link to post
Share on other sites

Here's an example of what some of the others are recommending as far as a bandpass enclosure ported through the ski-hole/rear armrest..

 

Build I did last year in my 2002 530i...

 

It was for experimental purposes and not permanent so don't mind the ugliness..

 

Bandpass1.jpg

 

BP5.jpg

 

BP4.jpg

 

BP7.jpg

 

BP6.jpg

Edited by A.SMALL

Share this post


Link to post
Share on other sites

What I liked about this enclosure was that it played the upper bass lines better compared to being ported in the trunk and no annoying trunk rattles. Never got to test it's full output against the ported enclosure though but for a permanent system in this car I will probably be running this same enclosure style with 2 12's.

Share this post


Link to post
Share on other sites

What I liked about this enclosure was that it played the upper bass lines better compared to being ported in the trunk and no annoying trunk rattles. Never got to test it's full output against the ported enclosure though but for a permanent system in this car I will probably be running this same enclosure style with 2 12's.

 

And this is the same results us competitors get in the real world vs on graphs.

 

4th BPs have a wider active passband than what vented enclosures have when built for that bandwidth but less overall amplitude compared to a vented enclosure.

Share this post


Link to post
Share on other sites

You didn't get hi-qts option did you?

no i did not. 2012 SSD 15 standard options. i just opened up the old box today and made the port 3.75 wide and tuned to 36hz and it definitely sounds better than it did. now i have 43 sq inches of port area and exactly 3 cubes of internal volume. it is definitely hitting the 60-70hz range much better, but its still lacking some of the output that the 2 CVR12s had in that range. though it does blow them away below 50 hz in both SQ and SPL. I still feel like something isn't right. i've created a crude illustration in mspaint of what my frequency response would look like on a spectrum analyzer. 

 

keep in mind that with my old setup, there was no such dropoff in the middle, it just didnt get much lower than 40hz with any authority.

 

 

http://www.mediafire.com/view/myfiles/#

Share this post


Link to post
Share on other sites

What port and sub orientation did you have with the kicker 12's? Was it the same sub up and port back as your current setup?

 

I've noticed in all of trunk setups I've ran that with the cone facing up there is some funky cancelation of certain frequencies in the 40+ range when compared to having the sub firing at the back of the car.

Share this post


Link to post
Share on other sites

kicker's were sub back and port back, i went sub up on the 15 because it was the easiest way to fit it in there. the general consensus on this forum that led to me to choose the 15 was that bigger is always better if you have space for the box, after my recent changes to the box; increasing the port volume up to roughly 14.5 sq inch per internal cubic ft up from 11 and thereby lowering internal net volume down to the 3 cubes minimum everything seems to sound better. considering that i may need to build a larger box with a slant to face the sub back. when i really crank up the volume i noticed that box itself actually jumps around the trunk, moving an inch or so in one direction or another. im thinking that is indicative of too little internal volume.

 

there's no noticeable distortion in the cabin, but the subwoofer cone is moving with so much force under high power and it makes a little bit of rattling noise, though cant tell if its port noise, lead slap, or just other things in the trunk rattling or the woofer itself distorting slightly. then again, i've never had such a powerful subwoofer, only a pair of 2 kicker comp12s and CVR12s. might just not be used to seeing one move so much.

 

i'm  told Fi subs are tough as nails and i would have to be feeding it in excess of 1100 watts to truly put it into a danger zone. with standard options that is.

 

my subsonic is set around 33hz. lpf is at 100hz~, i set the gain with the remote from the amp, just cranked it up with that until i reached a point where more gain didn't yield more SPL. so i think i have it set to the right sensitivity, which would be 4 volts for my head unit. phase knob i have left alone at 0, no bass boost. amp never gets hot, hifonics glx 1400.1d. 4 gauge wire, 150a ANL fuse connected to an 1100 amp battery. only about 2.5 ft between power cable and amp, 1.5ft from amp to negative terminal.

 

TL;DR : sounding much better with larger port area and higher 37hz tuning. suspecting box volume is a bit too small, suspecting that sub up port back is causing some cancellation issues. should i try putting the box at the back of the trunk near the headlights and facing the port towards the cabin?

Share this post


Link to post
Share on other sites

The fact that you had the kickers tuned to 40hz, the natural design of the cvr's, and the sub/port orientation is probably what gave you that amount of output at 40hz+. You swapped a setup that was loud above 40hz for one that offered better low end and a better overall sound. Its hard to get the best of both worlds out of a real trunk setup due to the amount of sound that is being trapped inside of the trunk. So its either tune low, tune higher, or find some middle ground between low end and upper end extension.

Have you modded the trunk any to allow more sound into the cabin?

Also I was able to get a 4.4 cube net enclosure in that trunk with 50 square inches of port for my XCON. Sub up port to the side. Experienced the same situation you're in but, I'd rather have my low end extension than a hefty 40hz+ .

Share this post


Link to post
Share on other sites

Moving the box around wouldn't hurt. Maybe it'll improve performance, maybe it won't. You won't know for sure until you try.

Share this post


Link to post
Share on other sites

im thinking maybe there wont be as much cancellation if the box is all the way at the back (next to tail lights) port facing either toward the cab or against the wall?

 

the only opening is the ski hole in the back seat, but ive been thinking about modifying the rear deck, creating an opening in the back of it maybe.

Edited by midnightE39

Share this post


Link to post
Share on other sites

Try moving it around and see.

 

As far as the rear deck goes, cutting out two 8 inch holes in the rear deck and modifying the rear deck cover did increase my output across the board but there was still a dip in frequency response above 40hz +.

 

I don't think modding the rear deck would solve your frequency response problem completely as much as it would give you a little more output. If you decide to mod the rear deck just ask yourself if going through the extra trouble of butchering your car is worth what you might gain.

Share this post


Link to post
Share on other sites

Ok I moved the box all the way back towards the taillights, there's enough room for air to escape and its a 43 sq inch port, but I've read some site posted on here that this way the secondary waves "bounce" back towards the cabin much closer in phase with the waves being produced by the cone. the cancellation has been reduced a great bit, though i think the orientation is to blame for that and beacause of it i shouldnt be able to get the response perfect. will be building a new box with both woofer and vent on the same plane. May even attempt that bandpass style box that was demonstrated if it would actually provide  a smoother transient response. but i want my subwoofer visible somewhere I like how it looks :)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×