I see what you're getting at now Nigel, you are correct: bridging doesn't give you any more power per amplifier, it just eneables you to put more power into higher impedance loads.
I see what you're getting at now Nigel, you are correct: bridging doesn't give you any more power per amplifier, it just eneables you to put more power into higher impedance loads.
I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.
Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.
Bridging in that aspect is pointless, it's smarter to run two amps to the two loads separately. But it's a TOTALLY different picture when you're talking about one speaker being driven from a single ended amp vs bridged, the power does double, it however does require an amplifier made for bridging or for the two separate amplifiers to be isolated.
"Because I be what I be. I would tell you what you want to know if I
could, mum, but I be a cat, and no cat anywhere ever gave anyone a
straight answer, har har."
the amps don't need to be isolated, you just don't use the grounds. when you drive an amp in bridge mode, there's a "virtual" ground in the center of the load. basically, each amp in the bridge "sees" half of the load impedance. if one of the amps in the bridge were to lose signal and just sit there at 0V output, that amp output would become a "virtual" ground. in fact if you were to monitor the base drive of the "ground" amp, you would find that the amp is "working" to keep that output voltage AT zero. there's no real purpose in running an amp in this manner, but it does reveal some of the inner workings of amplifier feedback theory.
if you want to drive a 4 ohm load with a bridged amp, make sure the amps used are stable to 2 ohms. most of the time if a 100W/ch stereo amp drives 8 ohm speakers to 100W, you will only get 150-175W in bridge mode driving an 8 ohm speaker. this is because of voltage sag in the power supply and the higher voltage drop across the output devices due to the increased current.
.................................................. .................................................. .
E=mc˛ (+/-1dB)
"If a curl of smoke is seen, the technician will soon experience the cause of difficulty"........ CTX arcade game rgb monitor service manual 1985
DC-to-Daylight Blog (on this forum):
http://www.electro-tech-online.com/blogs/unclejed613/
No, the power quadruples, but only because it was running at half power from the single ended amp, as my example above - due to using the wrong impedance speaker.Originally Posted by Sceadwian
My PA amp will provide 400W RMS per channel in 4 ohms, or 800W RMS mono in 8 ohms for bridged mode. I generally feed 2 x 8 ohm speakers from it, so run at 'only' 200W per channel.
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk
That's because those speakers you mentioned became IN SERIES and so the impedance is doubled so the bridge had nothing to do. But suppose you bridge those amplifiers and connect just one of 4ohms speakers across them, now because you have feed the 4ohms speaker with a DUBLE voltage (I.e. the bridged amplifier) the current that is going to go into the speaker is doubled too and so the speaker works more powerful. My assumption would be wrong only if you tell when bridging the impedance of the load will be doubled automatically!.
I do not know why both speakers would be destroyed but it tells that my assumption is right.
in essence the 4 ohm load presents a 2 ohm load to each amplifier, because the center of the load is a "virtual" ground, even if it's not connected to ground (it can't be anyway, because it's the center of the voice coil). if you could connect it to ground, there would be no net current to ground, since there's no voltage there. let's assume that the output of amp 1 is at +80V and amp 2 is at -80V and we have a 16 ohm load (or for a better illustration two 8 ohm speakers in series) the net voltage is 160V and the current is 10A. the center connection of the spealers is NOT connected to ground. so 10A*8 ohms=80V across each speaker, and since the output of both amps is 80V of opposite polarities, the voltage at the connection between the speakers is 0V. the power can be calculated in two ways. each speaker has 80V across it at 10A for a wattage of 800W per speaker(x2=1600W). the total voltage is 160V, and current is 10A, equalling a wattage of 1600W. if we connect only one of the 8 ohm speakers across the amps, the current doubles to 20A, with the same total voltage of 160V, giving a power of 3200W. the load EACH amp sees is 80V/20A=4 ohms.
.................................................. .................................................. .
E=mc˛ (+/-1dB)
"If a curl of smoke is seen, the technician will soon experience the cause of difficulty"........ CTX arcade game rgb monitor service manual 1985
DC-to-Daylight Blog (on this forum):
http://www.electro-tech-online.com/blogs/unclejed613/
Reply With Quote
