soniktoothe

Hi, I'm new here. I have been making some changes to my car that I got last month. I am currently thinking about putting a sub in my 2007 M3i sedan. I want to build a custom fiberglass enclosure to put behind the passenger rear wheel well. I really just want a little bottom end to round out my factory stereo. And i want to get something decent for as cheap as possible. Here is what I was contemplating:

Infinity reference DVC(4 ohm per coil) 10":
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

JBL 2 channel amp
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT
I know the amp is bridgable according to the info i found on it.

I have never worked with DVC subs before.
Option 1: If I wire each coil with its own channel I would get 60w x 2 to the sub. Probably enough power for me. Though I understand that it could damage the sub if the coils are working against eachother due to stereo input.
Option 2: I could bridge the amp then run the coils in parallel bringing the overall resistence to 2 ohm. Thereby increasing power, but would I fry the amp?
Option 3: I could bridge the amp and run the coils in series bringing the resistence to 8 ohm, deacreasing power. But would I then only have 60 watts total power? Or would I still be pushing 120 watts due to the amp being bridged.

I would really appreciate the help if I could clear these issues up. Thanks!

Jay

djs2571

option 1 - if you have two coils and only a single sub, and they are wired to fight each other, you'll know quick cause there'll be almost no output. Attach just one coil at a time and that will verify if it gets louder or quieter when the second is hooked up.

option 2 - the link to ebay is bad, but this still requires putting the coils in parallel, so still be careful with the polarity. If the amp is rated to a 2 ohm load bridged you'll have no problem, it should be a clear statement on the specs. Like 2x60 @ 4 ohms 1x170 @ 2 ohms, if it doesn't state a 1 by whatever wattage at 2 ohms you can't bridge it to your speaker.
I would just bridge the amp and get a normal single coil speaker. If you are just looking to match the stock system that's all you need... unless you're a bass head that wants to be heard, then you can go nuts for wattage.

Option 3 - bridge the amp and put the speaker coils in series - still have to make sure the polarty is correct. You will loose total output power of the amp.

You have the s-trim, so I assume 4 speakers, not a 6 speaker setup - which mine is, so the numbers below may not match your system.
But mine, the low end fell apart below 40 hz, so a very low low-pass crossover is needed for the sub - so you need a crossover at like 25 hz to roll off properly... unless you use a second unit like an EQ & crossover to run amps to all speakers and whatnot.

But back to just the sub... I installed a blaupunkt shallow mount flat subwoofer under the passenger seat, and measuring the power to it when it was just balancing out the way low end below the factory system it was under 10W with the system turned up, just cause it's got a very small frequency range to support, and the sub is sitting right next to you as well... so you don't need a huge amp unless you plan to use bass blockers on the factory speakers and use the sub for everything under 100Hz or something similar to that.

djs2571

Another friggin parrot, why are you here repeating posts?