I've added more to my complete overhaul of my sound system. I have the stock Infinity sound system, but it just wasn't loud enough for me with the top down. This summer I immediately put Polk Audio components & coaxials to an Alpine 4 channel M300 amp. This week I bought the Polk Audio MM840D (4ohm dual coil voice 8") sub to my stock enclosure and amp. Waiting to get an Alpine M500 mono amp for the sub so I can take out the stock Infinity amp. My last change will be the head unit (this summer when Sirius runs out).

It looks great, but it is not louder or as loud as the stock sub. Do I have my wires criss crossed? What I had to do was cut off the plastic housing for each cord (2 total). Each cord has a + and - wire. I have one cord routed to the top of sub + and - then one cord routed to the bottom of sub + and -. Is this making it 8ohm?


Thanks for looking and any advice would be greatly appreciated.

Attachment 253856

 

Any update on the sound? I was thinking of doing the same mod.

 

It might not be louder because you only replaced the sub which doesn't give your system more power. An aftermarket sub only accepts more power. So until you replace your head unit or larger amp or install a capacitor you gotta go with what you got. Do you have the ability to bridge your wires at the amp? I'm not familiar with the stock amp, all my stuff is aftermarket.

 

I haven't messed with the stock amp (only the sub is running off of it now). I have purchased the Alpine amp just waiting for shipment and I'll install it at the end of next month when I install my RK lift and Rigid Industries lights. Big changes come next month.

I was thinking that maybe it is because I didn't upgrade the amp, but wasn't sure.

Any other electrical wizards out there have any 2cents?

 

I'm not first hand experienced on this yet, but I hope to in the summer or at least warmer months. I read that the factory sub is dual voice coil and driven by two channels from the factory amp instead of the normal one channel. I'm not certain this is true or not but seems like the type of pita thing that comes from factory installs. In any case, if your sub is truly dual voice coil it should have 4 terminals (2 each of + and -). if you aren't wiring properly you can damage things easily so be sure to check.

If you've only got 2 wires from the factory amp then you need to find out what ohms the factory amp was driving to the sub, it could be written on the factory sub somewhere? Basically you need to determine if you wire the second voice coil in parallel or series depending on resistance. Personally if I don't have the info I wouldn't connect the sub unless you have a replacement warranty if you screw up. I'd suspect it's quieter because you aren't running both voice coils and getting half the power only. I'd imagine if you wire the second voice coil in parallel you'd get full power again, but I can't say that won't fry the amp if it tries to drive a lower resistance than can be safely achieved. If the sub is wired for series then you'd also be getting less power because of a higher resistance.

Bottom line for me would be wait until you replace the factory amp and know how to wire the sub to it for optimal power. Avoid unnecessary problems by going in blind and making assumptions.

 

I have each coil wired but for me to wire it in series to make it 2 ohm (which is what the amp is) I would have to hook up another wire to either top or bottom voice coil and wire it all the way to the factory amp. I'm just not going to do all that when my new amp will be here by next week. I don't want to go through all and do it all over again 2 weeks later. I have the bass down very low anyways. I'm sure it'll be fine for a few weeks since I only drive 50 miles a week anyways.

 

Ok quick lesson on series and parallel. Parallel lowers resistance, meaning your DVC sub with 4 ohm coils becomes 2 ohms overall in parallel. Series increases resistance, meaning your DVC sub with 4 ohm coils becomes 8 ohms overall in series. If you want a 2 ohm load you need to wire parallel which is easy, run the + and - input from amp to one pair on the sub, making sure it's for the same coil. Then run a wire from + to + and another wire from - to - and you're done. Is this how you are wired now? However, if the amp is driving 2 sub channels via 4 wires you can run each pair to each post pair on the sub and you'll have your parallel setup also.

Even if you wanted to do series you don't need to run additional wire from the amp. All you do is run from + to other coils - and then other coils + to first coil - and wire to amp as normal from the first coil. However, as above if you've got 4 wires from the amp but you want to do series, you can only use one pair of wires and you'll only be getting half the initial power running to double the resistance so it's not a great result as that halves the power again.

Again this is not first hand since I've not pulled my stock sub out yet and am not sure if it's wired with 2 or 4 wires from the amp.

 

Ok re-read the original post and guess I misread at first. It sounds like you do have 4 wires total meaning the amp is driving two channels as I've heard before. What I'm not sure of is if each channel is spec'd to 2 ohm or 4 ohm, I've only heard people say 2 ohm but not if that's per channel. What I do know is your new sub is 4 ohm per coil. If the amp is spec'd to 4 ohm per channel it should just plug and play with that sub. Since you're saying it's quieter, I'd have to guess then the amp is driving 2 ohm per channel but you've got 4 ohm on it, meaning you get about half the power leading to quieter sound.

 

The problem is the factory sub is a dual 2 ohm voicecoil. There is no way 2 wire a dual 4 ohm sub to extract the little bit of power that amp makes. You also could have used a single 2 ohm sub and wire it to see a 1 ohm load

 

Sorry...I missed typed I meant in parallel. I do know the difference though.

Also, this wiring won't be a problem for much long when I wire to in parallel for 2 ohm to my Alpine mono amp. Just have to keep the gain down so I don't blow the sub. I was just checking to make sure that I didn't wire it wrong. It's right but the stock amp is just not strong enough to push it.