Power calculations for a subwoofer?

[SeanTheDalek]

Hi guys! So I'm going to install a subwoofer as a part of my bed frame and power it off my deep cycle battery/batteries but I'm in the process of calculating how much power I need for everything in my van before I buy what I need.

I don't have a whole lot that's going to be pulling power, just a fridge and a few lights. I already have an old subwoofer but I don't know the specs so matching it to an amplifier is my problem. If I were to buy a 200 watt (being the RMS rating) amp with say a 1,000 watt peak will 200 watts be what's being pulled from my battery, or do I need to know the ohms of my subwoofer to wire it properly? Any advice or resources is greatly appreciated. Thanks!

 

[John61CT]

Get a battery SoC monitor that counts and displays AH in and out. Run a device over a couple hours with the same usage pattern, volume, temperatures whatever you will normally, or a bit higher to be conservative.

Anything else is a rough guesstimate, and the BM will help you tremendously to manage your system overall, extend the life of your bank.

I like Victron's BMV-702, and Bogart's, but there are cheaper ones out there.

 

[rvpopeye]

1 The amp max RMS output will vary with the impedance of the speaker.

2 You will have to know the specs of both.

3 The output wattage is not the (input)wattage the amp will draw from a power supply/battery.

4 See line 2..........

 

[gargoyle]

Specs on your sub should be available on the 'net.
Or an owners manual. Or a good car audio shop.

Personally, I would only run the amp/sub while you are running the vehicle, or on shore power.
A friend of mine did crazy custom stereo installs. He'd install an extra alternator to power the LOUD set ups. Extra batteries too. His stuff won lots of stereo competitions.

Stealth has left the building. booooom, booooomm.

 

[highdesertranger]

what's the rating of the fuse? 80% of the fuse value will give you a rough idea. highdesertranger

 

[rvpopeye]

Writing as someone that has used severe amounts of amplification and large transducers as my job for many years ......I just want to remind those in search of ultimate loudness from your personal sound systems.
YOU WILL DAMAGE YOUR HEARING !
IT WILL BE PERMANENT!
The longer and louder you do it.
The worse it will be.

Don't be me dude!

 

[tx2sturgis]

Is this a powered subwoofer? (all in one)
 
Or do you have a 200/1000 watt amplifier that is a separate piece?

Either way you can figure about double the RMS due to heat losses...

But!

It also depends on your habits as to how loud you like to crank it most of the time.

Cranking it to the max for 10 minutes is a lot different than running it at max volume for 10 hours...

And at modest, normal, comfortable, volumes it wont draw very much power.

You also need to consider the use of power (thumper) caps but you probably already know about them.

 

[Putts]

I'd keep an eye out for the words, "class-D amplifier."

Class-D amps are a little complicated to explain, but they're extremely efficient. A regular sub-power amp will use quite a bit of current just idling. In class-D amps almost all the power goes to the sub itself. The only time you'll use 200W is when you're driving that much power to the sub---which would be rare. I'd guess most sub amps are class-D by now anyway, but look for it.

 

[MikeRuth]

RVpopeye, I'm that dude as well, 18 years of Rock N Roll drumming. 80 percent loss, nothing above 1K, gone nada.

to the OP how hard are you planning on playing your music? If moderate sound levels it may not be that bad of a draw.

Mike R

 

[SeanTheDalek]

So I've been able to find the specs. Does anyone have any amp suggestions or ideas on electrical set-up?
@MikeRuth I don't plan on playing music very loud for the most part but I'm sure they'll always be the occasional volume crank from time to time.

1,200w Infinity sub
300w RMS @ 4 ohms

 

[DLTooley]

The libraries in this area offer AH meters on checkout, the 'kill-a-watt' device. Measuring actual use and possibly adjusting same based on results is a good place to start. You can also make an educated guess and then adjust use or scale your well designed system, as time and money permit.