power explained

[moves]

I found a cool article that explains power very well... I have a question though.... why would someone make a 4ohm resistance speaker when the 4 ohm needs more current and volts than the 8 ohm speaker to pass the energy through the wire? Wouldn't it be more efficient to make 8 ohm speakers with less resistance and have current pass through more easily? Is there a benefit to making a more resistant speaker impedance?

Anyway, here is the article I found:

HowStuffWorks "What are amps, watts, volts and ohms?"

 

[Irvrobinson]

You need to reread the article again. Lower impedance means more power is transmitted at the same voltage level.

Setting the impedance of a driver and a speaker system involves multiple factors, but among them are setting impedance to make crossovers easier to build, and using lower impedance to draw more current to make up for heavier cones or suspensions. Since solid state amps without output transformers are the most popular type, speaker designers know that these amps generally put out more power into four ohm loads than into eight ohm loads, and that extra power can be used as a tool for allowing them to optimize other design parameters.

 

[psbfan9]

I found a cool article that explains power very well
Anyway, here is the article I found:

HowStuffWorks "What are amps, watts, volts and ohms?"

Thanks for the link moves. A very nice article.

 

[markw]

Wouldn't it be more efficient to make 8 ohm speakers with less resistance and have current pass through more easily?

That's kinda like saying that rain wouldn't be so bad if it wasn't for all that pesky water falling down.

 

[moves]

You need to reread the article again. Lower impedance means more power is transmitted at the same voltage level.

Setting the impedance of a driver and a speaker system involves multiple factors, but among them are setting impedance to make crossovers easier to build, and using lower impedance to draw more current to make up for heavier cones or suspensions. Since solid state amps without output transformers are the most popular type, speaker designers know that these amps generally put out more power into four ohm loads than into eight ohm loads, and that extra power can be used as a tool for allowing them to optimize other design parameters.

So question for you... or anyone for that matter.... Here is my scenario: I would like to purchase a new centre channel and the one I am looking at comes in a 4ohm and an 8 ohm version. The website says that the 8 ohm plays at a louder level... which I don't really care about because I am sure the 4 ohm would be loud enough. Would it be better to get the 4 or the 8? The 4s are more popular and I think I would have to specially order the 8. I have a pioneer SC 27 that, from what I know, does not talk about playing 4 ohm speakers... what should I do?

 

[Irvrobinson]

So question for you... or anyone for that matter.... Here is my scenario: I would like to purchase a new centre channel and the one I am looking at comes in a 4ohm and an 8 ohm version. The website says that the 8 ohm plays at a louder level... which I don't really care about because I am sure the 4 ohm would be loud enough. Would it be better to get the 4 or the 8? The 4s are more popular and I think I would have to specially order the 8. I have a pioneer SC 27 that, from what I know, does not talk about playing 4 ohm speakers... what should I do?

I've never heard of such a thing, impedance options in a speaker, and since you haven't named the speaker it is impossible to judge.

 

[moves]

I've never heard of such a thing, impedance options in a speaker, and since you haven't named the speaker it is impossible to judge.

Please refer to the following link as it explains what I am talking about: http://totemacoustic.com/en/hi-fi/center-channels/model-1-signature-center/?surround=forest-model-1

I also have this to go with it: SC-27 - THX Ultra2 PLUS certified 7-Channel A/V receiver using class-D ICEpower amp (2 HD zones) | Pioneer Electronics USA

 

[markw]

One uses shoelded drivers for placement near CRT based TV screens, the other doesn't. They might look the same externally but they are different drivers.

 

[moves]

One uses shoelded drivers for placement near CRT based TV screens, the other doesn't. They might look the same externally but they are different drivers.

Would this affect sound?

 

[fmw]

Probably not much. It sure would affect the TV, however.

 

[moves]

So there is no point going with the 4 ohm load then? Would 8 be better for the receiver?

 

[Irvrobinson]

So there is no point going with the 4 ohm load then? Would 8 be better for the receiver?

I think it's irrelevant.

 

[moves]

I think it's irrelevant.

So then you are saying it's also safe to use this receiver with the 4 ohm version... even if the receiver is rated to 8 ohm loads?

 

[Irvrobinson]

So then you are saying it's also safe to use this receiver with the 4 ohm version... even if the receiver is rated to 8 ohm loads?

Yeah, I would think so, for a center speaker. I doubt you'll pump more than a few watts into a center.

 

[3db]

So then you are saying it's also safe to use this receiver with the 4 ohm version... even if the receiver is rated to 8 ohm loads?

I think the article needs to go further and skip the water analogy. I don't know how aware you are of impedance and receiver power so I'll try and just broad brush this in simple terms. Lets start with the 8ohm/4ohm thing.

Speaker Impedance
Speaker load or impedance is comprised of two electrical characteristics; one is resistance which is independent of frequency and one is reactive which frequency dependent is. Let’s take a woofer as an example. The resistive component, the resistance of the wire itself maintains its value from dc to well beyond the audio frequency range. The reactive component is the coil winding found inside a woofer. It will change values depending on the frequency applied to it. The overall impedance is a mathematical combination of both the resistive and reactive component. The same thing applies to the tweeter and to the cross over network, where the crossover network is used to separate the frequencies sending the lows to the woofer and the midrange and highs to the tweeter. So you can see that the speaker’s impedance will vary with the signal applied to it at that specific instant in time.

The behaviour of reactive components does one more thing. It delays either current or voltage signals relative to the resistive component. So if the resistive component sees the voltage and current simultaneously, the reactive component may see current before the voltage or vice versa. The difference between the current and voltage delay is called phase angle and is measured in degrees. The large the phase angle, the more difficult the load is to drive for the receiver. If the phase angle is largest in the bass region, it’s far more difficult for a receiver to drive a speaker whose phase angle is largest in the bass region compared to that if the phase angle was largest in either the mids or the highs.


Receiver Power
The amount of power that a receiver is required to put out depends on a few factors: a) speaker sensitivity (call it speaker efficiency), b) the size of the room, c) how loud you want to hear what’s being played, d) the impedance of the speaker and its phase angle. A large room with inefficient speakers and low impedance speakers is your worst combination and demand the most power from the receiver. If the room is smaller or the volume required is low, then it eases the load somewhat. Speaker efficiency also eases the power demands of a speaker.