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Old 28th March 2003, 09:05 PM   #1
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Default 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
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They are there so people can find this info if they search... I could't find ANYTHING!! lol
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Old 30th March 2003, 11:07 AM   #2
PMA is offline PMA  Europe
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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, non-bridged amp).
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Old 30th March 2003, 11:36 AM   #3
djdan is offline djdan  Romania
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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 high-pass 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 .
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Old 30th March 2003, 02:47 PM   #4
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what will be better ? sub box with 2x 18' subwoofers
or 3x 12' subwoofers ??
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Old 31st March 2003, 11:47 AM   #5
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Quote:
Originally posted by PMA
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, non-bridged amp).

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..
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Old 31st March 2003, 12:55 PM   #6
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Quote:
Originally posted by SkinnyBoy

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

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
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Old 31st March 2003, 07:35 PM   #7
djdan is offline djdan  Romania
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Dj BASS AMP ,

2x18" will be better .
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Old 31st March 2003, 08:23 PM   #8
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thanks
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Old 1st April 2003, 07:00 AM   #9
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Quote:
Originally posted by carlmart



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

Ahh... not I am even more confused.. forget it, I'll just only bridge into an 8 ohms speaker.. lol
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Old 1st April 2003, 07:49 AM   #10
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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 non-bridged 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 non-bridged amps.

So, if you don't mind two power supplies, it would make more sense to design a non-bridged 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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