Problem with two dd1508's running unevenly

[kvalvik]

Hello, im new here
I recently finished my new vented box for my two DD1508's:





Im running a RF t2000.1 on them.

I have a problem with the subs running unevenly. When i play with the engine off this problem is almost gone. but when im driving im not able to turn up the music much, because when it starts running unevenly it feels like the subs are gonna jump out of the box :S
doesnt sound healthy at all..

I tried filming the problem in action, but its hard to capture it properly.



The camera wouldnt pick up how much they jump. but towards the end of the film you can see it starting to change waves. In this song the bass is supposed to be mutch more even.

No matter what song, as long as it hits some low waves, it starts jumping. Sometimes it doesnt even help to turn the volume down, the subs will just go on blowing this loud, uneven wave, like the volume is WAY too high..

I also have a 2nd battery in the rear with a fused 35mm2 wire to the front battery, with the minus running to ground. and the amp is currently wired to the rear battery with 35mm2 wires(going 50mm2 as soon as i can afford it).

I dont know what to do. I cant really turn up the volume without it sounding like im blowing the subs. Kinda sucks since i put so much time and effort into this box :/

[bbeljefe]

Get the sub on the right as far away from the port entry as possible. It's unloading where it's at and you're taking a pretty good chance of damaging it.

If need be, mount them diagonally on the baffle in order to keep them away from the port entry.

[kvalvik]

Get the sub on the right as far away from the port entry as possible. It's unloading where it's at and you're taking a pretty good chance of damaging it.

If need be, mount them diagonally on the baffle in order to keep them away from the port entry.

Do you mean i have to redo the whole front of my box?

But if its in the wrong place, why would it be such difference from when im playing with my engine on or off? because there isnt any jumping or uneven bass when im running them only on ignition.

And if you see to the right on the photo of the finished box, you can see parts of the old temporary box i used for these subs, only porting on these are two pipes running about 20cm into the box. And i had the same problem with this box.

I do understand now that the sub on the right shouldnt be placed on top of the port entry like it is, but if thats the problem. i dont see why my old box had the same problem :S

[CleanSierra]

Listen to the man above, you're likely unloading that one sub that had the rear wave firing DIRECTLY into the port. The reason is not as noticeable with just the ignition turned over is because you're only getting around 12V like that, maybe less. When you turn the vehicle I , you're getting 14V+. You'd be amazed the difference that a couple volts can make.

[CleanSierra]

It could also have to do with the orientation of the enclosure in the trunk. You appear to be firing forward. One sub looks to be pointed at the hole entering the cabin and one is not. Again, loading appears to possibly be a factor but instead of it being off of the port, it could be happening with the backside of the seats.

[Soccerballzs]

The guy above is right sub in front of port has sound waves bouncing back up and hitting driver.

[n8ball2013]

So how much did that design cost you and who designed it

[bbeljefe]

Looks like the other box suffered from too little port area, but who knows.

Like Clean said, there is a remarkable difference in the amount of power an amplifier can generate at 14 volts as opposed to 12. Plus, when you're running with the vehicle off, there is nothing there to replenish the voltage so every time you hit a good, strong bass note, the the amount of current available lessens considerably. This isn't the topic of the post but I strongly advise against running a high powered audio system hard without the vehicle running. Just a few dips to 10 volts and you can do some serious damage to your amp(s).

Another thing to look at, if you were indeed having the same problem with the other box (not saying you weren't, just hard to tell exactly what's happening from your description), is the impedance of the subs. If the coils are wired in parallel, one may be open, causing an uneven load. And... sometimes a sub gets marked with the wrong impedance, so you may have different coils.

[kvalvik]

oh :s Does this mean that my boxdesign is rubbish? I can probably remove most of the front plate(exept the port opening) and make a new one where i place the subs as far to the side as possible. i dont know if it would be enough, now that the box is not really that high.

So how much did that design cost you and who designed it

Well i made the design myself. The thing is that the guy i bought the subs and the amps from seemed to know a lot about box building and such. So he gave me these specs:

elements should have about 30L each.
Port opening: 400cm2
Port length: 85cm


So from this i calculated the box and did it myself. And he approved the design, so i went on and built it.

Another thing to look at, if you were indeed having the same problem with the other box (not saying you weren't, just hard to tell exactly what's happening from your description), is the impedance of the subs. If the coils are wired in parallel, one may be open, causing an uneven load. And... sometimes a sub gets marked with the wrong impedance, so you may have different coils.

Well the guy i bought it from made sure i had to wire theese in parallel, witch makes 1 ohm(?).

[bbeljefe]

oh :s Does this mean that my boxdesign is rubbish? I can probably remove most of the front plate(exept the port opening) and make a new one where i place the subs as far to the side as possible. i dont know if it would be enough, now that the box is not really that high.

So how much did that design cost you and who designed it

Well i made the design myself. The thing is that the guy i bought the subs and the amps from seemed to know a lot about box building and such. So he gave me these specs:

elements should have about 30L each.

Port opening: 400cm2

Port length: 85cm

So from this i calculated the box and did it myself. And he approved the design, so i went on and built it.

Another thing to look at, if you were indeed having the same problem with the other box (not saying you weren't, just hard to tell exactly what's happening from your description), is the impedance of the subs. If the coils are wired in parallel, one may be open, causing an uneven load. And... sometimes a sub gets marked with the wrong impedance, so you may have different coils.

Well the guy i bought it from made sure i had to wire theese in parallel, witch makes 1 ohm(?).

Your design isn't rubbish, it just needs some improvement.