View Full Version : Needs a hand

06-03-2012, 10:53 PM
Hey guys, I wasn't sure where to post this thread, so if it needs to be relocated, have at it. However, I just got my ssa zcon 18 in my car running off a crescendo bc2000d. The box is an estimated 7.5^3 tuned to ~34. Me being the ******* I am currently have the box in the cabin. At first the box was loud(quiet to most of you), but it smacked horribly due to lack of bracing. Flame me now, but yes, at first I put it in without a double baffle. I just redid the box, added sufficient bracing, and a double baffle. However the box got so much quieter, and I am confused on what could've changed that much.

With this all said, I have a few questions. Could lack of output be from my changes to the box, or is it something else? Also, I need a suggestion on what box set up would get loudest. I was thinking on just making a below window line wall sort of deal while sealing off the trunk. Which way should my port be facing for optimal output? Any feedback is greatly appreciated. Thanks

06-03-2012, 10:57 PM
is the box still in the cabin

06-03-2012, 10:57 PM
adding the bracing changed the net vol of you box which changed your tuning....

06-03-2012, 10:58 PM
define "i just redid the box"? what exactly did you do? Just stick some bracing in and an extra baffle on top? Because in that case it shouldn't have gotten quieter.

06-03-2012, 11:00 PM
I apologize, but yes, I only added a double baffle and 2 sections of threaded rod. I highly doubt that took much out of my net volume.

06-03-2012, 11:02 PM
is the box sealed up well??

06-03-2012, 11:02 PM
The threaded rod and double baffle shouldnt have affected the sound negatively. Maybe you wired the sub up wrong when you put it back in?

06-03-2012, 11:02 PM
Also yes, the box is still in the cabin. It won't fit in the trunk.

06-03-2012, 11:07 PM
I would double check your wiring, maybe didn't get something back on right when you put it back together.

06-03-2012, 11:12 PM
damnnn, it just dawned on me I wired to 4ohms. Thanks for the tip guys. But any other tips for the setup?

06-03-2012, 11:16 PM
get a sub that fits in the trunk, then people can sit on the back seat ;)

06-04-2012, 07:05 PM
I lied, the sub was wired correctly. aha but people can sit their ***' in the trunk if they must, at the moment.

Moble Enclosurs
06-04-2012, 07:50 PM
Actually it can make a negative effect on the sound and does have an effect on tuning. The box before resonated much like a roof in a vehicle, BUT the difference is, the resonating did shift the tuning (could be by as much as a 5-10Hz difference depending on the area that is moving) and caused it to shift the phase of the box's output also. My guess is the box was not designed correctly in the first place, and by allow it to move with the output, two things happened (being that it was in the cabin).......
1:It-the baffle- acted like one huge woofer moving at 1-3mm in the center which is like a 32inch sub moving 1-3mm overall. This is a small effect, but can increase pressure in the vehicle at a specific tuning.
2: The box was out of phase in the low end before, and the resonant baffle cause the response to change phase and allow the low end to reproduce at a more in phase response which can in fact add to the output! I have a model that can prove this.

SO, the moving baffle caused a resonance to occur, adding to the output MAINLY because it was in the cabin-BUT ALSO MAINLY at a specific frequency only, though adding output to a single frequency can increase the surrounding frequencies outputs depending on the band of the increased gain. In a trunk this might not be as audible.
I can't say whether this is rare or not, but I have experience it before a few times locally, and with my model that I created to induce pressure for checking my formulas.

So, here is the thing with the phenomenon...........it happens at a specific frequency of resonance. SO, once the baffle is tightened or loosened either way, that resonance shifts with it, and the previous resonance either increases or cancels out either way. If you take a box with one thin panel on it (like my model has to simulate a factory roof flex), then when you put your hand on it, it changes its resonance to a higher frequency, thus the output at higher frequencies are increased-always only to a point dependent on too many factors to mention right now. Then when it loosens up, it resonates at a lower tuning and increased output at that frequency range. You would think the opposite occurs where the stronger the box is, the more output you get, but that is ONLY dependent on the frequency range it operates in and if those resonances are within that range, you WILL notice the differences.

My guess on this is that it resonated quite well to be in the LF response range. Fixing that resonance is like putting a 45 in the port where certain peaks are cancelled a bit by pressure changes. Then when it was braced, those resonances went away, and the output technically improved by pressure, but not by intensity at the frequency range of interest due to the phase shifting that occurred.

it is possible to relate this to a passive radiation type of response where the radiator moves with the output by pressure allowing for more low end output. Very similar concept.