View Full Version : How to decide which amp to use with which subs?

06-29-2009, 06:34 PM
Hey guys,

Well I'm planning on making a custom trunk enclosure. I'm just not sure about subs/amps. Like If I want to run 2 12" subs, say subs are rated at 600watts rms each. What kind of amp should I be looking for? Im debating on whether I should just get a conventional ported box instead of making my own enclosure but I'm still trying to figure out this whole power issue. I don't want to underpower nor overpower the subs.

Anyways thanks!


06-30-2009, 05:06 AM
You said it correctly. One thing I always did, was never buy an amp powerful enough to blow your subs, but powerful enough to run them good and blow its self.

Are the subs 600 watts, or 600 rms? there both different right. if it's watts, i figure ud be around 250-300 rms per sub, than your looking for a amp with 500 rms. it's going to depend on what rms they are. and trust me with this, build a box, or get one built what you fancy, to the specs of the subs. inside the sub boxes will be paper that has the sub info and sizing on it.
On that same paper there will be a chart that will give you sizes for single enclosure, single ported enclosure, double sealed and ported enclosure. Follow it it. I've made plenty of boxes of the years with friends and helping them. The one's that actually listen to me on the box sizes, weather it was right away or after the 1st ideal went to shit, loved they way they sounded. It's well worth the time to design the box and build it. You'll be thankful you did.

What subs do you have btw?

06-30-2009, 07:57 AM
Kinda what he said above......................

If you want to run two 12" subs that are rated 500 Watts RMS, here's what I think you need to know...............

If the subs are dual voice coil (VC) 4 ohm and you run the VC's in parallel (+ve to +ve and -ve to -ve terminals), then you have a 2 ohm load per sub. Then you run the two subs in parallel you end up with a 1 ohm load. If your amp is a 250 watt mono-block at 4 ohms, it may be 500 watts at 2 ohms and 1000 watts at one ohm (just making up numbers!!). Your subs are rated for 500 watts each.............. so the amp is making 1000 watts at 1 ohm and you are gold.

If the subs are dual voice coil (VC) 4 ohm and you run the VC's in parallel (+ve to +ve and -ve to -ve terminals), then you have a 2 ohm load per sub. Then you run the two subs in series you end up with a 4 ohm load. If your amp is a 250 watt mono-block at 4 ohms, that doesn't work so well !!! You need a 1000 watts at 4 ohms.

It's a similar game with single voice coil subs. You just need to decide on what subs you'd like to have and then try and find an amp to work with them. OR.......... find an amp you like and search out subs that will work with the amp. As long as everything matches spec wise, you are good. *smoke* It's all about playing with the sub's VC configuration (load) and making sure the subs RMS rating matches the specs on the amp for the load you are giving it.

Regarding BMW's, you usually have to give it them a little more if you're doing a trunk versus a hatch. BMW trunks are sealed up pretty good. Two 12" or a 15" in my opinion at a minimum (or four 10"!!!) ......... unless you are using 10's with big excursion. And if you're willing to give up your spare and are handy, there's a cool easy way to make a false floor enclosure with 2x4's and expanding foam *th-up* which can't be stolen like a box. The other choice with a sedan is free air (infinite baffle) off the rear deck. Also hard to steal and you save your trunk. But you need a subwoofer that is specifically built for this application............... usually has a stiffer spider and surround to control the cone movement as it doesn't have an enclosure per se to do that anymore.

Hope this has helped ........ somehow !!!

06-30-2009, 01:30 PM
^^^Thanks Guys!

Tom- little bit confusing but I'm going to read it over a few time's to understand it better. As for the Idea of using my spare tire well for false floor enclosure is what I'd like to do. Anyone have pics? I know I would have to make a double floor so that I could mount the subs and amps on the main mdf board. Then rip some pieces to put around the the amp or amps and subs to lift the second board. But would like some pics as an idea.

Thanks for the help guys!!!


Dado 540
06-30-2009, 02:20 PM
These are mailny concerning the E39s, but it may give you an idea or helpfull info






06-30-2009, 03:11 PM
Thanks for the pics! I like the very simple set-up, false floor holding the two amps, 2 12's in box. Looks very clean.

Would you guys recommend buying subs/amps, from major retailers such as best buy, futureshop..... or online, or smaller shops? I check out future shop and best buy and honestly to me, I feel like their stuff is way over priced! any input?



06-30-2009, 11:11 PM
I personally would not buy from BestBuy and Futureshop but their products will do the trick. They do not get into higher end, better quality stuff but they are not overpriced in any way as far as I can see from their website. I buy from a place called Radioactive in Burlington. Great guys who know their stuff. They will walk you through everything and help you with everything you could need. Service there is second to none. Here is their website www.radioactive1.com


07-01-2009, 01:51 AM
Thanks guys, well update

So I went to bestbuy on winston churchhill and dundas, Got to liking the Alpine MRP-M1000 Amp with the 2 12" Alpine Type R subs they had. I told the girl working in the audio department I wanted them. She started going on and on about how i should get their warrenty which i declined, since a friend of mine had very a very bad experience with their warrenty about 6 months ago.

Long story short he had a high end sub with full 3 year warrenty, but when the sub died, he went for an exchange, they didnt carry that sub anymore and would only offer to replace his $300 sub, with a $99 sony explode.

So anyways, she tells me to give her a sec because shes helping someone pick out a gps. I waiting 10mins, nothing, then she goes to help out 2 retards who had been playing with the speakers for half an hour, so I figured, wtf I'm about to spend over a grand, and I have to wait like an idiot? **** this. So I left went to futureshop.

The same amp was listed $150 more at futureshop, but when i brought it up to the audio guys attention he price matched it to best buys. Althought they didnt carry type r subs. I'm going to get them at another location..

Anyways thanks for everyones input, more input is defenatly welcome, especially ideas on making a false floor!



07-02-2009, 08:35 AM
are you going to buy a premade box for those subs? or are you going to make one your own?? if your going to make one your own and if it's a sealed box that you want, if you want send me the specs of the subs and the suggested cubic foot for the subs, and the dimensions of you trunk. and i'll put a box design together for you n email it back. unless your going to,lol..:P

07-08-2009, 09:40 AM
Man........... if you haven't bought anything, PM me. Or I'll PM you right now with my number and you can call me.