Speaker impedance

[Muse]

I have a minisystem that came with 2.7 ohm impedance speakers, a Panasonic RX-DT600. The manual on the last page has specifications and it shows the output to be 2.7-8 ohms. I have another mini-system whose 6 ohm speakers I'm not using, am using Yamaha 6 ohm bookshelf speakers instead. Can I use its 6 ohm speakers with this Panasonic? They are a lot bigger than the ones that came with the Panasonic. Can I even use 8 ohm speakers? I have even bigger 8 ohm speakers from a different minisystem!

 

[jtvang125]

They'll work but they won't be receiving the full power from the stereo because of the increased resistance.

 

[JAG87]

Yes, you can always use higher impedance speakers with an amplifier that supports lower impedance speakers. It's the other way around that you can't, or you will burn the amplifier.

 

[Railgun]

...to a certain extent and if it's in the range of the amp.

 

[donfm]

They'll work but they won't be receiving the full power from the stereo because of the increased resistance.

Huh? Actually it's not resistance it's impedance which is a function of the inductance, capacitance and the resistance of the speaker. As I recall from my days in electronics school the amp will output the same power with either speaker but at different volume levels...the power limitation of the amp is the same for each only the current will be higher on the lower impedance speaker. Somebody correct me if I am wrong here.

 

[Muse]

Well, it's going in a small room. I'll try them and see how they sound. If I have to use the 2.7 ohm speakers I'm going to have to solder on extension wiring anyway, so it's actually less work to use the 6 ohm speakers. Their leads are long enough already to reach the places where the speakers are going.

 

[Gibson486]

Huh? Actually it's not resistance it's impedance which is a function of the inductance, capacitance and the resistance of the speaker. As I recall from my days in electronics school the amp will output the same power with either speaker but at different volume levels...the power limitation of the amp is the same for each only the current will be higher on the lower impedance speaker. Somebody correct me if I am wrong here.

It is all about impedance matching. If you have a low output impedance, then having in even lower input impedance will result in overdriving. If you put a higher input impedance at the load, all the power will not be absorbed by the load and the excess not absorbed gets reflected back. Also, power is a function of voltage and current. You cannot simply say, current will be higher. You need to do everything in terms of power because having current be higher can also result is voltage going lower, which could mean power stayed the same.

 

[donfm]

It is all about impedance matching. If you have a low output impedance, then having in even lower input impedance will result in overdriving. If you put a higher input impedance at the load, all the power will not be absorbed by the load and the excess not absorbed gets reflected back. Also, power is a function of voltage and current. You cannot simply say, current will be higher. You need to do everything in terms of power because having current be higher can also result is voltage going lower, which could mean power stayed the same.

You are incorrect in a couple things you said. You can ABSOLUTELY say the amp current will be higher with a lower impedance load than a higher impedance load. I = E/Z where Z is the impedance of the load. Physics doesn't lie. I'm not sure what you are talking about the excess power being reflected back. There are no magical properties of power reflection like that. In the end it all behaves by Ohm's Law. If you don't use the power it just isn't used. Just because an amp can output a certain amount of maximum power doesn't mean it needs to in all circumstances. If power were always constant than the volume would always be constant as well.

Yes impedance matching between speakers and amplifier is important. I liken a low impedance speaker using a high impedance amp to a guy peddling his ass off in first gear on a bicycle. He's expending a lot of energy but getting no place fast. The internal voltage drop within the amplifier increases when a low impedance load is connected. The more current being drawn the greater the internal amp voltage drop. This equates to a lower output voltage at the amp terminals. This voltage drop is a direct function of the current being drawn from the amplifier. This higher output current with lower impedance loads transmits to a lower output voltage and less amp power available to the load. Thus it is wasting power better known as an impedance mismatch. The optimum transfer of power between an amplifier and a speaker occurs when the input and output impedances are identical.

 

[alkemyst]

It depends on amplifier design whether changes in impedience will affect output power.

 

[Howard]

In terms of "will anything blow up", you'll be fine. Don't turn it up too high since who knows what the minimum impedance of the Yamaha speakers is.

 

[Railgun]

It depends on amplifier design whether changes in impedience will affect output power.

Nearly every amp in existence will provide more power to lower impedance. You decrease the impedance, your current goes up thus power goes up. The problem is whether it can handle the heat generated from the additional current. Or you just fry the amp altogether.

 

[alkemyst]

Nearly every amp in existence will provide more power to lower impedance. You decrease the impedance, your current goes up thus power goes up. The problem is whether it can handle the heat generated from the additional current. Or you just fry the amp altogether.

Thanks Capt. Obvious.

However; it doesn't change the validity of what I posted that one first has to look at the reciever/amp they are dealing with. The spec sheets will show all the information being guessed at here.

 

[Railgun]

It's a statement that doesn't need to be made. In the context of this thread, every single amp that someone will buy will increase power as impedance is decreased. In fact, I will retract my previous statement and make it a blanket statement. Find me an amp that DOESN'T increase power when impedance is decreased.

 

[donfm]

It's a statement that doesn't need to be made. In the context of this thread, every single amp that someone will buy will increase power as impedance is decreased. In fact, I will retract my previous statement and make it a blanket statement. Find me an amp that DOESN'T increase power when impedance is decreased.

There isn't one.....

 

[alkemyst]

There isn't one.....

http://www.jlaudio.com/hd750-1-car-audio-hd-amplifiers-98220

JL Audio is well known for this.

I don't know of a home setup that is the same off the top of my head, but there was discussion of them on AudioKarma a few times and they do exist.

 

[donfm]

http://www.jlaudio.com/hd750-1-car-audio-hd-amplifiers-98220

JL Audio is well known for this.

I don't know of a home setup that is the same off the top of my head, but there was discussion of them on AudioKarma a few times and they do exist.

This only says that the amp is capable of outputting that power at various impedance levels. That does not disprove anything we've said. It does not state anything about the overall power consumption of the amp at the various impedance levels. There is no magical amp that consumes the same amount of power for all loads.....at AudioKarma or anywhere else.

 

[alkemyst]

We were referring to output power to the speakers.

Seriously how much the amp consumes is irrelevant.

 

[Gibson486]

You are incorrect in a couple things you said. You can ABSOLUTELY say the amp current will be higher with a lower impedance load than a higher impedance load. I = E/Z where Z is the impedance of the load. Physics doesn't lie. I'm not sure what you are talking about the excess power being reflected back. There are no magical properties of power reflection like that. In the end it all behaves by Ohm's Law. If you don't use the power it just isn't used. Just because an amp can output a certain amount of maximum power doesn't mean it needs to in all circumstances. If power were always constant than the volume would always be constant as well.

Yes impedance matching between speakers and amplifier is important. I liken a low impedance speaker using a high impedance amp to a guy peddling his ass off in first gear on a bicycle. He's expending a lot of energy but getting no place fast. The internal voltage drop within the amplifier increases when a low impedance load is connected. The more current being drawn greater the internal amp voltage drop. This equates to a lower output voltage at the amp terminals. This voltage drop is a direct function of the current being drawn from the amplifier. This higher output current with lower impedance loads transmits to a lower output voltage and less amp power available to the load. Thus it is wasting power better known as an impedance mismatch. The optimum transfer of power between an amplifier and a speaker occurs when the input and output impedances are identical.

Dude, you are talking to an EE. If you do not understand about power being reflected back to the source, then you should not even be discussing it. Ohms's law is just the basis of all circuits, but when AC is involved, you have to take into account more than just v=ir.

 

[Howard]

It's a statement that doesn't need to be made. In the context of this thread, every single amp that someone will buy will increase power as impedance is decreased. In fact, I will retract my previous statement and make it a blanket statement. Find me an amp that DOESN'T increase power when impedance is decreased.

Most tube amps. Any amp with a relatively high output impedance.

 

[donfm]

Dude, you are talking to an EE. If you do not understand about power being reflected back to the source, then you should not even be discussing it. Ohms's law is just the basis of all circuits, but when AC is involved, you have to take into account more than just v=ir.

I'm not discussing it YOU are. I have never even heard of it in this context......lol...I don't even see where it's a relative issue here. Sure there are other forces at work to be considered like inductance...capacitance...resistance. I just assumed that was a given in this discussion. These are all taken into consideration with impedance. But in the end it all basically behaves by Ohms Law in an amplifier. Obviously there are other forces at work in an audio circuit but my Ohms Law example was just a simplification not meant to be a total explanation. You made that assertion not me.

Seriously you didn't just play the lame I have a degree in EE card did you?.....I have a degree in EET and have studied audio amplifiers down to component level as well as building them in the lab. Nowhere in my experience was there ever any mention of "power reflection" in the context of this discussion. In fact my freind is an EE and I ran this by him just for kicks. He never heard of power reflection being an issue in a simple audio circuit. Show me a link that supports your statement concerning "reflected power" in audio amplifiers and I will capitulate. Dude.

In all fairness to you I did a search on "power reflection" and nothing came up. I was fully ready to admit I was wrong if something came up. The only thing that even came close was power as it applies to "wave reflection" and that only pertained to RF and Microwave transmission signals. It has no real bearing on the topic at hand presently that I can see.

 

[donfm]

We were referring to output power to the speakers.

Seriously how much the amp consumes is irrelevant.

Who is this "WE" of which you speak?
you are not qualified to speak for anyone but yourself please...maybe that is what YOU were rambling about. I was talking about the overall amount of power drawn from the amp. The lower the impedance the greater the power the amp must output to maintain that load at a constant output. I'm not sure how much more relevant it can get. If it can't maintain that power output it simply burns up.

As your history here has shown you just get off on arguing with people here and I have no interest so I'm done with you.

 

[alkemyst]

Who is this "WE" of which you speak?
you are not qualified to speak for anyone but yourself please...maybe that is what YOU were rambling about. I was talking about the overall amount of power drawn from the amp. The lower the impedance the greater the power the amp must output to maintain that load at a constant output. I'm not sure how much more relevant it can get. If it can't maintain that power output it simply burns up.

As your history here has shown you just get off on arguing with people here and I have no interest so I'm done with you.

Wow, Broheim, or Mr. EET I should say.

When you and your brahs were building all your amps from scratch in a lab, you guy's were really focused on the power draws as the spec people give a crap about and not output power at whatever ohm rated speakers?

HOLY MOLY, I HAVE BEEN DOING 20+ YEARS OF AUDIO WRONG!

All bow down to Mr. EET.