6 ohm amp driving 4 ohm speaker ?
I'm shopping for a Sony HT-DDW700 5.1 Home Theater system ,
with 6 speaker outputs : 100 watt 6 ohm . With 6 ohm speaker outputs , is bad driving 8 or 4 ohm speakers ? Thanks , Jim D |
6 ohm amp driving 4 ohm speaker ?
On Feb 20, 1:22 am, Jim Davis wrote:
I'm shopping for a Sony HT-DDW700 5.1 Home Theater system , with 6 speaker outputs : 100 watt 6 ohm . With 6 ohm speaker outputs , is bad driving 8 or 4 ohm speakers ? Thanks , Jim D You only get max power transfer if you match the speaker impedances exactly. If you use a lower speaker impedance than the source you can overload the amplifier and damage it. If you use a higher impedance speaker than source you will not damage anything but you will get some reduction in maximum volume obtainable. This advice is brought to you by Sirkituk -- please visit my site at www.geocities.com/sirkituk |
6 ohm amp driving 4 ohm speaker ?
|
6 ohm amp driving 4 ohm speaker ?
On Tue, 20 Feb 2007 18:09:55 GMT, "Jack"
wrote: Since the source impedance is near zero - That's exactly what will happen. The 4 ohm speakers will draw 6 amps from the amplifier and overload it by 50% which it may or may not survive. --- Please bottom post. Well, yeah, if he's putting a CW signal on the input and cranking the amp up to 11, but that wasn't the point. The point was that audio amps aren't designed to provide a power match to the load. -- JF |
6 ohm amp driving 4 ohm speaker ?
On 2007-02-20, Jack wrote:
Since the source impedance is near zero - That's exactly what will happen. The 4 ohm speakers will draw 6 amps from the amplifier and overload it by 50% which it may or may not survive. only if you turn the volume up too far. -- Bye. Jasen |
6 ohm amp driving 4 ohm speaker ?
On Feb 20, 1:20 pm, John Fields wrote:
On 20 Feb 2007 03:42:58 -0800, wrote: On Feb 20, 1:22 am, Jim Davis wrote: I'm shopping for a Sony HT-DDW700 5.1 Home Theater system , with 6 speaker outputs : 100 watt 6 ohm . With 6 ohm speaker outputs , is bad driving 8 or 4 ohm speakers ? Thanks , Jim D You only get max power transfer if you match the speaker impedances exactly. --- Not true. the amplifier looks like voltage source with close to zero source impedance. If it's rated to drive a 6 ohm load to 100 watts, then that means it can supply: P 100W I = sqrt --- = sqrt ------ ~ 4 amperes R 6R through the load, and place: E = sqrt (PR) = sqrt (100W * 6R) ~ 24.5V across it If you use a lower speaker impedance than the source you can overload the amplifier and damage it. --- Since the amplifier's source impedance is near zero ohms, that's not like likely to happen. Hoewever, damage can occur if there is no overcurrent shutdown and you try to pump more than 4A into the load. --- If you use a higher impedance speaker than source you will not damage anything but you will get some reduction in maximum volume obtainable. --- That's true -- JF In my days of playing with audio, the output impedance was important. It was usually marked on the back of the equipment, ie 4ohms, 8ohms etc. I was not aware that domestic audio equipment could have "almost zero" impedance. Can you explain further please. What kind of output device is this? Sirkituk |
6 ohm amp driving 4 ohm speaker ?
|
6 ohm amp driving 4 ohm speaker ?
On 25 Feb 2007 01:09:01 -0800, wrote:
On Feb 20, 1:20 pm, John Fields wrote: On 20 Feb 2007 03:42:58 -0800, wrote: On Feb 20, 1:22 am, Jim Davis wrote: I'm shopping for a Sony HT-DDW700 5.1 Home Theater system , with 6 speaker outputs : 100 watt 6 ohm . With 6 ohm speaker outputs , is bad driving 8 or 4 ohm speakers ? Thanks , Jim D You only get max power transfer if you match the speaker impedances exactly. --- Not true. the amplifier looks like voltage source with close to zero source impedance. If it's rated to drive a 6 ohm load to 100 watts, then that means it can supply: P 100W I = sqrt --- = sqrt ------ ~ 4 amperes R 6R through the load, and place: E = sqrt (PR) = sqrt (100W * 6R) ~ 24.5V across it If you use a lower speaker impedance than the source you can overload the amplifier and damage it. --- Since the amplifier's source impedance is near zero ohms, that's not like likely to happen. Hoewever, damage can occur if there is no overcurrent shutdown and you try to pump more than 4A into the load. --- If you use a higher impedance speaker than source you will not damage anything but you will get some reduction in maximum volume obtainable. --- That's true -- JF In my days of playing with audio, the output impedance was important. It was usually marked on the back of the equipment, ie 4ohms, 8ohms etc. --- You're probably referring to audio amplifiers with output transformers, where the transformer was used to match the plate-to-plate impedance of the final to the speaker impedance. Here's a good link: http://www.vac-amps.com/Technical_Monograph_90-9.htm I was not aware that domestic audio equipment could have "almost zero" impedance. Can you explain further please. What kind of output device is this? --- Usually a couple of transistors operating AB1 or AB2, which are lowish-voltage high-current devices which can drive low impedances like speakers directly. what makes their output look like an almost zero impedance is feedback which causes the output voltage to remain constant regardless of the load impedance. That is, if we had an amplifier with an output voltage of 10 volts RMS, open circuit, and we then placed an 8 ohm resistor across the source, the voltage would remain at 10VRMS. -- JF |
6 ohm amp driving 4 ohm speaker ?
On Feb 25, 5:23 pm, John Fields wrote:
On 25 Feb 2007 01:09:01 -0800, wrote: On Feb 20, 1:20 pm, John Fields wrote: On 20 Feb 2007 03:42:58 -0800, wrote: On Feb 20, 1:22 am, Jim Davis wrote: I'm shopping for a Sony HT-DDW700 5.1 Home Theater system , with 6 speaker outputs : 100 watt 6 ohm . With 6 ohm speaker outputs , is bad driving 8 or 4 ohm speakers ? Thanks , Jim D You only get max power transfer if you match the speaker impedances exactly. --- Not true. the amplifier looks like voltage source with close to zero source impedance. If it's rated to drive a 6 ohm load to 100 watts, then that means it can supply: P 100W I = sqrt --- = sqrt ------ ~ 4 amperes R 6R through the load, and place: E = sqrt (PR) = sqrt (100W * 6R) ~ 24.5V across it If you use a lower speaker impedance than the source you can overload the amplifier and damage it. --- Since the amplifier's source impedance is near zero ohms, that's not like likely to happen. Hoewever, damage can occur if there is no overcurrent shutdown and you try to pump more than 4A into the load. --- If you use a higher impedance speaker than source you will not damage anything but you will get some reduction in maximum volume obtainable. --- That's true -- JF In my days of playing with audio, the output impedance was important. It was usually marked on the back of the equipment, ie 4ohms, 8ohms etc. --- You're probably referring to audio amplifiers with output transformers, where the transformer was used to match the plate-to-plate impedance of the final to the speaker impedance. Here's a good link: http://www.vac-amps.com/Technical_Monograph_90-9.htm I was not aware that domestic audio equipment could have "almost zero" impedance. Can you explain further please. What kind of output device is this? --- Usually a couple of transistors operating AB1 or AB2, which are lowish-voltage high-current devices which can drive low impedances like speakers directly. what makes their output look like an almost zero impedance is feedback which causes the output voltage to remain constant regardless of the load impedance. That is, if we had an amplifier with an output voltage of 10 volts RMS, open circuit, and we then placed an 8 ohm resistor across the source, the voltage would remain at 10VRMS. -- JF- Hide quoted text - - Show quoted text - Thank you thats a big help. Ed |
6 ohm amp driving 4 ohm speaker ?
On Feb 25, 5:21 pm, PeterD wrote:
On 25 Feb 2007 01:09:01 -0800, wrote: I was not aware that domestic audio equipment could have "almost zero" impedance. Can you explain further please. What kind of output device is this? Impedance is 'directional'. That is the impedance that an amplifier (or whatever...) drives does not necessarly equal the back impedance of the amplifer. Say a signal goes to teh speaker. For whatever reasons, some of that signal is reflected back towards the amplifier. The ideal goal is that the amplifier appear as a very low impedance to that signal, to help prevent its being reflected a second time back to teh speakers... Same basic concept as batteries--an ideal battery has an internal impedance (resistance, since it is DC) of zero or almost zero. Were the battery's resistance be any significant value at all, then its current supplyling capabilities would be rather limited. Thanks that's a big help Ed |
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