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28th March 2003, 09:05 PM  #1 
Banned

2 Ohms stable Transistor Amplifier...
I would like to bridge a 4 ohm stable amplifier into 4 ohms.. that means 2 ohms per channel.... Are the only limiting factors the transformer and the power disipation of the output devices? I was planning on doing a 6 channel amplifier with 1 HUGE heatsink... Which means all the devices will be mounted on the one heatsink.... so, if I was to bridge 2 channels, the other 4 will be unused, and therefore generate no heat... also, the transformer will have all available power... So..... could I put extra transistors on 2 of the output channels so just those 2 channels will be used when bridging into 4 ohms?? Basicaly, i want an amp, that will give ~800watts RMS into 4ohms.. why?? Well, to totally trash all these peoples "1000watts RMS" subs.. lol
Could a subwoofer (15inch) really handle 1000watts RMS CONTINUOUS (sine wave) WITHOUT ripping itself apart? I know at some frequencies it will... but at the lower frequencies... ITS GOING TO BURN!!! lol "two ohm stable" "2 ohm stable" two ohm stable 2 ohm stable ^^^^^^^^ They are there so people can find this info if they search... I could't find ANYTHING!! lol 
30th March 2003, 11:07 AM  #2 
Design engineer, consultant
diyAudio Member

It is difficult to answer in general. Just take to the account that every branch of your bridged amplifier will have to deliver 2 x higher peak current into the load (compared to single, nonbridged amp).

30th March 2003, 11:36 AM  #3 
diyAudio Member
Join Date: Dec 2001
Location: Romania

I will answere at your second part question.
Yes , a single 15" speaker can do easy this job only if you can't run on clipping and if you will use a highpass filter ( 18 or 24dB/oct) at 20 or 25 Hz. But if you wanna be the best , use more speaker at less power. Four 10" /8ohm speakers at 2 x 500w/4ohm will give a better response . 
30th March 2003, 02:47 PM  #4 
Account Disabled
Join Date: Jul 2002

DJ DAN hii
what will be better ? sub box with 2x 18' subwoofers or 3x 12' subwoofers ?? 
31st March 2003, 11:47 AM  #5  
Banned

Quote:
I'm sorry, I don't really understand what you are saying... I would liek to be able to bridge 2 out of the 6 channels into 4 ohms... the other 4 will only be used bridged into 8 ohms minimum, or not bridged at all... so, double the output devices to increase the thermal transfer, or whatever.. lol anyway, yeah... thanx for teh help so far.. 

31st March 2003, 12:55 PM  #6  
diyAudio Member
Join Date: Mar 2001
Location: Brazil

Quote:
You probably know this, and maybe the way you put it is just that. But you do not "bridge" into a certain impedance like when you parallel speakers. In fact, if you could say that you "bridge" then you do it into the larger impedance really. Your bridged amp will not be as tolerant of lower impedances (i.e.: 4 ohms) as the unbridged amps, quite the opposite. You may have to do a bit more than doubling the devices, like lowering the supply voltage, correcting any internal protections or increasing the heatsink area. Carlos 

31st March 2003, 07:35 PM  #7 
diyAudio Member
Join Date: Dec 2001
Location: Romania

Dj BASS AMP ,
2x18" will be better . 
31st March 2003, 08:23 PM  #8 
Account Disabled
Join Date: Jul 2002

thanks

1st April 2003, 07:00 AM  #9  
Banned

Quote:
Ahh... not I am even more confused.. forget it, I'll just only bridge into an 8 ohms speaker.. lol 

1st April 2003, 07:49 AM  #10 
diyAudio Member
Join Date: Mar 2003
Location: Northwest

What's the application?
In general, bridged amps have a number of disadvantages some of which get worse into low impedance loads. Consider: A bridged amp has twice the Vce drop as a nonbridged amp which means it's going to run a lot hotter. Bridged amps have double the output impedance which means half the damping factor. This is especially an issue for a low impedance subwoofer. Roughly speaking a bridged amp has twice the distortion of the same amp not bridged. Most forms of distortion usually rise as the impedance drops. It's not uncommon for THD to roughly double at high power levels as you cut the imedance in half. A bridged amp multiplies that by two again. Bridged amps often don't clip as cleanly as nonbridged amps. So, if you don't mind two power supplies, it would make more sense to design a nonbridged 4 ohm amp to deliver however much power you need for the subwoofer(s) and then power the other channels from perhaps different rail voltages if necessary. In the car stereo world, a lot of guys have found they get significantly better bass by NOT bridging the subwoofer amp(s). Even though most of these amps are rated to run bridged into 4 ohms they're not very happy doing it. 
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