best 3.1 speaker system image
alanfreefa
How long will a speaker system that uses 2 watts stay on for (it turns off at 12VOLTS) if i use 12 duracell batteries? The batteries are new, so lets assume each is 1.5 volts...
Answer
It depends on the impedance of the speaker and what power you actually use. Two watts is a very loud noise from an efficient speaker. If you are playing music with loud peaks of sound (drums for example), the average power will probably be much less than 2W.
Anyhow, assuming you really mean 2W, first find the current through the speaker. Power = I^2R.
For a 4 ohm speaker, I = 0.707amps (0.707 x 0.707 x 4 = 2)
For an 8 ohm speaker, I = 0.5 amps
A typical AA cell has a capacity of about 2.2 amp-hours. Assuming all the cells are in series, the total capacity of the battery is the same, 2.2 amp-hours.
For a 4-ohm speaker the batteries will last 2.2 / 0.707 = 3.1 hours
For an 8 ohm speaker, 2.2 / 0.5 = 4.4 hours.
If the cells are in series/parallel (two parallel sets of 6) that would double the playing time. That is possible, since 9 volts (from 6 cells) is plenty to produce 2 watts of power in a loudspeaker, you don't need 18 volts.
These are a very approximate estimates. In practice it will probably last longer because the average power will be less than 2 watts. On the other hand, it ignores the power used by the rest of the amplifier and radio, mp3 player, or whatever, which might be of the order of 0.5 to 1 watt.
It depends on the impedance of the speaker and what power you actually use. Two watts is a very loud noise from an efficient speaker. If you are playing music with loud peaks of sound (drums for example), the average power will probably be much less than 2W.
Anyhow, assuming you really mean 2W, first find the current through the speaker. Power = I^2R.
For a 4 ohm speaker, I = 0.707amps (0.707 x 0.707 x 4 = 2)
For an 8 ohm speaker, I = 0.5 amps
A typical AA cell has a capacity of about 2.2 amp-hours. Assuming all the cells are in series, the total capacity of the battery is the same, 2.2 amp-hours.
For a 4-ohm speaker the batteries will last 2.2 / 0.707 = 3.1 hours
For an 8 ohm speaker, 2.2 / 0.5 = 4.4 hours.
If the cells are in series/parallel (two parallel sets of 6) that would double the playing time. That is possible, since 9 volts (from 6 cells) is plenty to produce 2 watts of power in a loudspeaker, you don't need 18 volts.
These are a very approximate estimates. In practice it will probably last longer because the average power will be less than 2 watts. On the other hand, it ignores the power used by the rest of the amplifier and radio, mp3 player, or whatever, which might be of the order of 0.5 to 1 watt.
How to connect more speakers to my existing home theatre system?
swapnilvz
I have a 5.1 channel home theater system, all the 6 channel jacks are connected to speakers of 3 ohms each. I have 4 old speakers from a previous system. two main speakers are 6 ohms each and the other two satellite speakers are 16 ohms each. and to top it all my home theater system does not have a line out jack at the back. How do I go about wiring these 4 speakers to my existing system?
Answer
Strongly unadvised... I'm with the others on this one... Don't do it.
Guessing with this sort of thing, voids your warrantly... has the potential to fry things that are at this point working. However, since you're asking...
3 Ohms, I'll also agree is a rather peculiar load... it's usually 2,4 or 6 Ohms... regardless... this is what you posted... so...
If for instance your amplifier is Class AB and running 50% effiency at 3 Ohms, and say 50 Watts... when you double the Ohms rating you've lost power ouput capability by as much as 1/2... So at 6 Ohms the given channel is now only capable of producing 25 Watts. When you half your power you've halved your effective dB levels by half. It takes twice the power to increase output by +3 (+10 db SPL's) which is a doubling of effective loudness to the average listener.
Typically, you don't want to step up or down more than a single impedance load level... I've yet to see a standard amplifier that'll drive 1.5 Ohms, stabily for your average home theatre system, so that leaves you with going up a level, or trying to stay as close as you can to the existing impedance load... so the maximum target impedance load would be 6 Ohms, and the minimum would be 2. I guess what you're asking, are there any combinations that I can safely wire so I don't fry my gear.
-=[The math...]=-
I don't know if you have a Philips HTR 5000, but it was the only one I could find with 6 channels, and a 3 Ohm load on all those channels... so... we'll work off that one... for examples.
http://www.p4c.philips.com/files/h/htr5000_01/htr5000_01_dfu_eng.pdf
Running Series we Add... running Parallel we take...
1/(1/a+1/b+1/c+1/...)
Where a,b,c are the differnt speakers wired in parallel. Another things you need to make sure, is that the RE (Thiele-Small Spec - RE is the actual DC resistance of the drivers voice coil) be matched to all the other drivers. I'll guarantee you this is not the case... and you'll find that on the satellites, and the mains that were shipped with the system will be working harder than the other drivers at the increased output levels. The high impendance drivers that you're attempting to wire in are more resistive, so the drivers are going to be handling different power levels, and now you risk underpowering scenarios to the motors which is far more likely to fry speakers. Anyways... warnings aside... And you can pretty well guarantee, as mentioned above this this just voided your warranty... ;)
Front speakers...
checking them in series... 3+6 = 9 Ohms... that's likely not going work... or if it does, it'll sound very quiet.
parellel... 1/(1/3+1/6) = 2 Ohms... that might work... but make sure you're watching heat levels on your gear...
So on a hypothetical, you can run your mains in Parallel... and still be able to hear something... at the servere risk of, you guessed it... 'cooking your gear'...
Rears...
> What you could do is run the sats as a
> second set of surrounds in SERIES.
I have to directly contradict The Sound Broker on this one...
> You now have 4 speakers running off the
> rear surrounds at a higher impedence which
> is easier on the amp as far as load.
I'll agree with you to a certain extent... but let's do the math on this...
Running the Satellites in Series... 3+16 = 19 Ohms...
If the amplifier is functioning at 3 Ohms stable, or likely recommended optimum... this just critically underdrives the speakers. 3 Ohms, doubled... becomes 6 Ohms, to 12 Ohms... to nearly 24 Ohms...
If the Channel has a maximum output of 50 Watts... we just went to 25, to 12.5 to 6.25 Watts... Over two speakers... 16 Ohms, suggests they were possibly driven from a Class A, or AB, Tube at some point. The liklihood of hearing much of anything out of those speakers is slim... as the output stages of the Reciever probably aren't functioning at much past 6 Ohms... This is more likely to cook the speakers, and disable the output capabilities of the amplifier stages.
If you run them parallel... 1/(1/3+1/16) = 2.52 Ohms... that's pretty close to 3 Ohms... but... it's obvioulsy pulling more current, something you have backwards, as you state here, that current is stable, indifferent to the impedance load.
> What it won't do is lower the current demands
> since you now have double the drivers to control
This really makes it sound like you know what you're talking about... but come on???
You've got is totally backwards... almost all amplifiers are VOLTAGE DRIVE... NOT CURRENT DRIVE... the difference? A big one... I see an awful lot of crap posts being dished out to unsuspecting people expecting to receive a decent answer... This is nonsense...
Voltage Drive - As the impedance falls, the load voltage will remain constant, as the current increases, and more power is created...
Current Drive - As you are suggesting... a majority, if not all Solid-State amps do not work this way... As the impedance rises, voltage increases, to maintain the same level of current. So as the current rises, the power output level increases...
No matter how you look at this, varying the impedance on a Voltage Drive circuit will alter it's current! Sheesh... for an audio guy, I find this flabbergasting.
As for the last part of the question...
> so watch the heat and listen for audible signs
> of clipping. You will obviously have to
> recalibrate your surround channel levels.
As you have suggested to wire this up, heat is not likely the issue, as there's way to much impedance to even pull any current to the speakers.. so the output power has been critically damped. Without current draw, there's no amplification, so there logically wouldn't be any heat, because no work is being done... Clipping? Huh? And then to suggest recalibration of the surround channel levels... Too funny, I haven't laughed this hard in a long time.
> and to top it all my home theater system does
> not have a line out jack at the back. How do
> I go about wiring these 4 speakers to my existing
> system?
I'd say at this point, unless you understand what's been written so far, I wouldn't even attempt it... Otherwise...
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
http://www.rocketroberts.com/techart/spk_wire.htm
There is little chance this will increase the overall productivity of system. And the above mess is why... ;)
Strongly unadvised... I'm with the others on this one... Don't do it.
Guessing with this sort of thing, voids your warrantly... has the potential to fry things that are at this point working. However, since you're asking...
3 Ohms, I'll also agree is a rather peculiar load... it's usually 2,4 or 6 Ohms... regardless... this is what you posted... so...
If for instance your amplifier is Class AB and running 50% effiency at 3 Ohms, and say 50 Watts... when you double the Ohms rating you've lost power ouput capability by as much as 1/2... So at 6 Ohms the given channel is now only capable of producing 25 Watts. When you half your power you've halved your effective dB levels by half. It takes twice the power to increase output by +3 (+10 db SPL's) which is a doubling of effective loudness to the average listener.
Typically, you don't want to step up or down more than a single impedance load level... I've yet to see a standard amplifier that'll drive 1.5 Ohms, stabily for your average home theatre system, so that leaves you with going up a level, or trying to stay as close as you can to the existing impedance load... so the maximum target impedance load would be 6 Ohms, and the minimum would be 2. I guess what you're asking, are there any combinations that I can safely wire so I don't fry my gear.
-=[The math...]=-
I don't know if you have a Philips HTR 5000, but it was the only one I could find with 6 channels, and a 3 Ohm load on all those channels... so... we'll work off that one... for examples.
http://www.p4c.philips.com/files/h/htr5000_01/htr5000_01_dfu_eng.pdf
Running Series we Add... running Parallel we take...
1/(1/a+1/b+1/c+1/...)
Where a,b,c are the differnt speakers wired in parallel. Another things you need to make sure, is that the RE (Thiele-Small Spec - RE is the actual DC resistance of the drivers voice coil) be matched to all the other drivers. I'll guarantee you this is not the case... and you'll find that on the satellites, and the mains that were shipped with the system will be working harder than the other drivers at the increased output levels. The high impendance drivers that you're attempting to wire in are more resistive, so the drivers are going to be handling different power levels, and now you risk underpowering scenarios to the motors which is far more likely to fry speakers. Anyways... warnings aside... And you can pretty well guarantee, as mentioned above this this just voided your warranty... ;)
Front speakers...
checking them in series... 3+6 = 9 Ohms... that's likely not going work... or if it does, it'll sound very quiet.
parellel... 1/(1/3+1/6) = 2 Ohms... that might work... but make sure you're watching heat levels on your gear...
So on a hypothetical, you can run your mains in Parallel... and still be able to hear something... at the servere risk of, you guessed it... 'cooking your gear'...
Rears...
> What you could do is run the sats as a
> second set of surrounds in SERIES.
I have to directly contradict The Sound Broker on this one...
> You now have 4 speakers running off the
> rear surrounds at a higher impedence which
> is easier on the amp as far as load.
I'll agree with you to a certain extent... but let's do the math on this...
Running the Satellites in Series... 3+16 = 19 Ohms...
If the amplifier is functioning at 3 Ohms stable, or likely recommended optimum... this just critically underdrives the speakers. 3 Ohms, doubled... becomes 6 Ohms, to 12 Ohms... to nearly 24 Ohms...
If the Channel has a maximum output of 50 Watts... we just went to 25, to 12.5 to 6.25 Watts... Over two speakers... 16 Ohms, suggests they were possibly driven from a Class A, or AB, Tube at some point. The liklihood of hearing much of anything out of those speakers is slim... as the output stages of the Reciever probably aren't functioning at much past 6 Ohms... This is more likely to cook the speakers, and disable the output capabilities of the amplifier stages.
If you run them parallel... 1/(1/3+1/16) = 2.52 Ohms... that's pretty close to 3 Ohms... but... it's obvioulsy pulling more current, something you have backwards, as you state here, that current is stable, indifferent to the impedance load.
> What it won't do is lower the current demands
> since you now have double the drivers to control
This really makes it sound like you know what you're talking about... but come on???
You've got is totally backwards... almost all amplifiers are VOLTAGE DRIVE... NOT CURRENT DRIVE... the difference? A big one... I see an awful lot of crap posts being dished out to unsuspecting people expecting to receive a decent answer... This is nonsense...
Voltage Drive - As the impedance falls, the load voltage will remain constant, as the current increases, and more power is created...
Current Drive - As you are suggesting... a majority, if not all Solid-State amps do not work this way... As the impedance rises, voltage increases, to maintain the same level of current. So as the current rises, the power output level increases...
No matter how you look at this, varying the impedance on a Voltage Drive circuit will alter it's current! Sheesh... for an audio guy, I find this flabbergasting.
As for the last part of the question...
> so watch the heat and listen for audible signs
> of clipping. You will obviously have to
> recalibrate your surround channel levels.
As you have suggested to wire this up, heat is not likely the issue, as there's way to much impedance to even pull any current to the speakers.. so the output power has been critically damped. Without current draw, there's no amplification, so there logically wouldn't be any heat, because no work is being done... Clipping? Huh? And then to suggest recalibration of the surround channel levels... Too funny, I haven't laughed this hard in a long time.
> and to top it all my home theater system does
> not have a line out jack at the back. How do
> I go about wiring these 4 speakers to my existing
> system?
I'd say at this point, unless you understand what's been written so far, I wouldn't even attempt it... Otherwise...
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
http://www.rocketroberts.com/techart/spk_wire.htm
There is little chance this will increase the overall productivity of system. And the above mess is why... ;)
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Title Post: If i am using 12 duracell AA batteries in a 2WATT speaker, how long will it stay on for?
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