DIY sub: massive driver needs big amp for cheap!

levine · 22nd March 2002, 08:57 AM

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 · 22nd March 2002, 12:04 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.

scopeboy · 22nd March 2002, 01:47 PM

Why don't you look at the cheapo brands of PA amplifier like Limit or SoundLab. These are normally used by bedroom DJs and such like. You should get a fairly high-powered bridgeable stereo amp for less than it would cost to buy the parts.

scopeboy

kelticwizard · 22nd March 2002, 02:33 PM

Quote:

Originally posted by levine
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.

levine · 22nd March 2002, 03:39 PM

Quote:

Originally posted by kelticwizard

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

Dustin Haug · 22nd March 2002, 06:49 PM

Not sure what you consider a big amp, but you might want to check out www.apexjr.com or www.adireaudio.com they have plate amps that'll put out 200-300 watts, which is probably adequate for your 300W RMS sub. They are very resonably priced as well.

I've got an AVA250 from Adire. I really like it.

Chucko · 22nd March 2002, 07:52 PM

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.]

22nd March 2002, 08:57 AM	#1
levine diyAudio Member Join Date: Mar 2002	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

22nd March 2002, 01:47 PM	#3
scopeboy diyAudio Member Join Date: Mar 2002 Location: scotland	big amps for subs Why don't you look at the cheapo brands of PA amplifier like Limit or SoundLab. These are normally used by bedroom DJs and such like. You should get a fairly high-powered bridgeable stereo amp for less than it would cost to buy the parts. scopeboy

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22nd March 2002, 12:04 PM	#2
leroy diyAudio Member Join Date: Oct 2001	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.

22nd March 2002, 06:49 PM	#6
Dustin Haug diyAudio Member Join Date: Feb 2002 Location: Charleston, SC	Not sure what you consider a big amp, but you might want to check out www.apexjr.com or www.adireaudio.com they have plate amps that'll put out 200-300 watts, which is probably adequate for your 300W RMS sub. They are very resonably priced as well. I've got an AVA250 from Adire. I really like it.

22nd March 2002, 07:52 PM	#7
Chucko diyAudio Member Join Date: Jan 2002 Location: Silicon Valley, CA, USA	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.]

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