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Cornish 7th February 2013 07:19 PM

Advice needed for construction of portable sub
Hi there,

(this first bit isn't an advert just an explanation)

I'm from UK, we have recently had a new portable product launched from a guy living over here called a mini-rig (rig being the term given to 5-30K soundsystems used in clubs / at unofficial outdoor events, not sure if this is the same in the US).
Its pretty impressive I've had sound engineers listen and they're blown away, anyway the one thing it lacks is some decent bass response (its a 3" neodymium driver) and I haven't been too bothered about it but I've recently been clearing out some stuff and found an old PC 5.1 system that had a faulty volume cable. it is the Yamaha yst ms30
so I figured as I know a little about things like this I'd rip out the pcb out from the sub enclosure and make it into a small rechargable portable sub to go with my speaker.

So here are my questions:

1) I would have to install a crossover into the sub enclosure right? so it would go ipod>sub crossover then one wire to sub amp and one to a 3.5mm jack which the minirig would plug into. This is one area I'm not great on, could anyone suggest a solution or product.

2) it would need an amp and battery installed, being an 18W speaker would this item work? Kemo M033N 18 Watt Universal Mono Amplifier Module 320-553

3) What would be the suggested battery pack to make this run for 6-10 hrs on normal volume

As I said I understand the basic working of stereo's and amps etc. But have never done anything like this before, am I missing something here...? and any other advice would be greatly appreciated

All the best


Mooly 7th February 2013 07:32 PM

Well subs aren't really my thing :) but to get you started...

The amp module specifies it will work over quite a wide range of voltages but of course you are only going to get max power with the higher supplies. (from the small size of the amp and the fact no extra heatsinks are needed I would say it is a Class D design).

The quoted current consumption is <800ma. (Music is much less demanding than sine wave testing). 0.8 amp over 10 hours would need an 8AH (amp hour) battery. For music it would be less and 6AH is a common size. Three 6 volt 6AH VRLA (valve regulated lead acid... gell batteries like in alarms etc) should be ideal or even a 12 and 6 volt in series.

The crossover would need defining but here's something similar and runs on 12 to 36 volts,

Cornish 7th February 2013 10:08 PM

Thanks Mooly

So it seems thats 3 of those batterys would be slightly more than I'd like for it to be portable but I did manage to find this Battery Masters :: Yuasa NP2-12, 12V 2Ah Sealed Lead Acid Battery (L(mm) W(mm) H(mm) 150 20 89) Which as it happens is the perfect fit for on the back of the unit above any inputs of dials. So with a smaller 6v 2ah battery (along with amp and crossover) inside it should give me about the same amount of space taken up inside as when standard but have a nice battery pack powering it. I hope.

As for defining the crossover, I would not have even the first clue as to how to do that. My knowledge of electronics is not as good as I'd like but I did have the idea that I might be able to use the crossover than exists on the original board, i just have to find out if this is plausible, and if not how I can get round it..

steep learning curve for me tho, any other input is appreciated :)


Mooly 8th February 2013 08:35 AM

As long as 2 AH is sufficient and that's really difficult to say with certainty on music. For continuos sine wave power output it wouldn't go the distance.

You quite possibly could use the existing circuitry (or part of) but you would need the circuit details.

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