DIY sub: massive driver needs big amp for cheap!

I found a steal on Infinity Reference 12" subwoofers, and am interested in building my own subwoofer for my home theater. The drivers are a massive beast, intended originally to be used in a car audio application. They take 300W RMS, 1200W peak and have a 4 ohm impedance (which may cause problems).

My original thought was to use a car amp to power it, and using an old PC PSU to get the 12VDC to the amp, but I quickly realized that adequate ampres would not be fed to it in this manner. Further, professional DJs I know assure me that trying to convert power to feed into an amp is just a Bad Idea(tm) to begin with - out goes the idea of using a bridge rectifier to get 120VDC and stepping it down massively!

So, understanding that the concept behind this project is cost-effectiveness, can anyone suggest to me a realistic way to power this woofer in a home theater setup? Be it a particularly cheap amplifier that has gained a reputation for being halfway decent, or some homebrewed scheme for driving big woofers like this one, I'd like to hear everything you guys can throw at me. Bear in mind the impedance will likely cause some problems... alternative suggestions welcomed. I really want to make a DIY-project out of this one.

Regards,
Peter Bourgon
 

leroy

Member
2001-10-31 10:52 pm
First: BIG and CHEAP never come together.

I suggest something with multiple integrated amplifier IC's in a bridge configuration. You only need to add a few more components (and supply of course). That will certainly do for a sub-amp.
Look for application notes and datasheets for more information.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
levine said:
I found a steal on Infinity Reference 12" subwoofers,....

I am not really any amp expert, but for others in the forum, I would just like to establish one thing: how many drivers are you hooking up? I noticed the plural in your post, and it seems unclear whether you are powering one driver, a pair, or four.
 
Re: Re: DIY sub: massive driver needs big amp for cheap!

kelticwizard said:


I am not really any amp expert, but for others in the forum, I would just like to establish one thing: how many drivers are you hooking up? I noticed the plural in your post, and it seems unclear whether you are powering one driver, a pair, or four.

Apologies. The sub will contain only a single driver.

Thank you all for your suggestions - I'll look into what I can.

Regards,
Peter Bourgon
 
If you want BIG clean reliable power at 4 ohms for not a lot of money, check out QSC's RMX 1850HD. At 4 ohms, it will put out 550 W (FTC) or 600 W (EIA) continuous per channel. Bridged into a single 4 ohm load, it will crank out 1800 W!

I got mine for $455 shipped. I use it in a bass guitar rig with some inefficient speakers (Acme Low B-2).

[Edit: clarified specs.]