Amp for subwoofer

[mahal]

Hi everybody,
Maybe i am not in the correct forum but i'm asking anyway.
I bought a house theater and the subwoofer is passive ( no amp in)
and it doesn't sound very loud.
What kind of amp i can build to feed the speaker witch is 3 ohms.

Thanks

Yves

[Nasse]

Off topic or not, a good subwoofer can do wonders for your stereo, home theatre system, home or more professional studio, bass rig, band PA et cetera et cetera.

But you asked a question. Passive subwoofer crossover filter does indeed suck much power, and adjusting its level can be impossible if it is used with some system that it is not matched for. And records and movie and TV soundtracks have variable levels of bass.

If your system has ready made line level output for subwoofer and that signal is already filtered, all you need is suitable power amp. If suitable signal is not ready available, you need active crossover filter. You can make it do-it yourself principle or buy it ready made. Check car stero accessory shops for quite cheap ones. Ready made 100-300W modules that have connectors, filters and amplifier in neat package are available at some hifi retailers, and all you need is cut suitable hole in your box and screw the module in and connect wires and switch the power on.

Sometimes suitable amp may found at home, perhaps you have an old stereo or mono amp lying around that may do the job. They say more power and good damping factor are what to look for. I made for myself a LM3886 amp, and and it gives quite nice amount of punish for my 15" self-made 120 liters closed box. But I am not sure if 3886 is happy with 4 or 3 ohms, because it is optimised for 8 ohms. For my 8 litres vented bass box with 100 mm element I used TDA7370 chip which gives 2x22 W r.m.s power and it is enough loud with my 21" TV and small living room, of course lowest notes can not be heard with it.