CMUpike

alright, so i installed my new subs the other day into a bandpass box. i'm not sure if my subs were meant for a bandpass box, but i have seen them sold as a package in a bandpass box, so i didn't think it was a big deal.

here's the problem: they're DVC (dual voice coil) audiobahn 1251T subs. the bandpass box is for 2 12" subs. the box is sealed between the two subs inside but not where the "glass" shows. the box also has 4 inline ports on top of the box, two for each sub.

when i first fired up the subs. they made a really bad fluttering sound. when i covered up one of the ports, the sound got much better. so i covered up 2 ports on one side (now one of the subs has no ports) it sounded great. however, when i covered up all 4 ports, it started fluttering again. I tried taking the plexiglass off, and it still fluttered. it also flutters when i cover up one port on each side, and with three of the ports covered up.

does this make sense to anyone? i'm not sure why it does this. i'm considering buying a new sealed box on e-bay since they're going for about 50.00 shipped.

right now, i have the two ports on one side duct taped. it's loud... and doesn't flutter, but i'm sure this is not an "efficient" setup.

if anyone has any input, please let me know!

Jason B

Your box sounds like my bandbass.



Try adjusting the ports higher and lower.

CMUpike

jason, did you build your own box?
i've really wanted to build my own box for the longest time, however, i neither have the tools (it would be a very difficult project to do with just a dremel tool, and a handsaw) nor the carpentry skills to design/build the thing.


did you have a problem with your subs fluttering before you adjusted your ports?

-Jay

BIGMOOI

I would say try a sealed box but you might not have enough space since it will need to be bigger. if you have a spec sheet on your subs it will tell you what kind of air space you will need in all box designs. if it doesn't tell you what air space you need for a specific box then the subs were not designed for that setup. you can also try to make the ports smaller but it all depends on how much work you want to do. you should be able to get the specs on there web site. covering 2 ports on one sub is ok you basically have the same setup as i had before in my old car i had 2 jbl gt 1200Ds in a single bandpass box from MTX. it was a push and pull setup, the 2 cones were face to face and i had DVCs so it was wired to 4ohm mono. worked great and sounded great. so if you like the sound then i would say keep it. the only thing that matters is the sound. looks are always nice but unless you are trying to compete then i would keep it out of you mind. and if you want it to look better copy the demesions of the box you got rebuild it your self and leave 2 ports out of it then.
just my opinion.
sorry it is so long:pat:

castrolSi

They are out of phase. Switch one of your wires around from - to + and that should fix your problem. Sounds right to me...


~castrol

KevyWevy

yeah try switching one of the speaker wires

williemon

Why not find out what box best fits these subs? If you just want to do it bandpass, then find out what the proper volume for both chambers would be and what size ports to use. If you cant find the specs, try to get the Theile Small parameters and plug them into some free ware box builder programs and it will show you what you need. If you already have the box, then you might can get the TS specs and modify the ports or the internal volume of the chambers of your box based on what the software says.

hell_on_ice

When I purchased my bandpass box, it came with instructions on cutting the ports to length to match the output of the subs. I don't remember the details, but I had to match the specs from the subs with a chart in the manual for the box that showed what length to cut them to. They sounded incredibly better after doing this.

CMUpike

thanks guys. i think i'm gonna tinker around with it tomorrow. the back/ported side of the box does seem a little small. i stuffed it with some polyfill, which did help a lot. which is leading me to believe that the volume of the box is too small. i will tinker around with the ports. i also may have the wiring messed up, since it's a DVC sub. i looked at some diagrams online, and i'll try to change that around too. worse comes to worse, a new sealed box on ebay is 45 bucks... shipped

again, thanks for the tips.