Impedance (Ohms)

[mazersteven]

Impedance is the electrical characteristic of a speaker that restricts ("impedes") the flow of power from your receiver, or amplifier. The impedance value of a loudspeaker is expressed in Ohms.

So, is there any benefit to having a lower Ohm speaker?

And why are so many higher end speakers 4 ohms? Is there a sound quality difference? Is it the driver that causes the impedance, or the whole speaker design.

 

[Vaughan Odendaa]

That's a good question. I'm not sure why speaker designers choose an impedence of 4 ohm for their designs.

The other day, someone told me that 4 ohm speakers should be a light load for the amplifier because there is little resistance to current flow so more current should flow.

But the reality is that the amp will be stressed more at low impedence loads because it has to deliver more current, sometimes much more, and if it can't, then it will clip and produce severe distortion.

Besides, impedence varies with frequency.

--Regards,

 

[Adam]

You got me curious, so I did a Google search and came across this (among many other, but it's the only one that I've read so far). Pretty easy to follow.

As Vaughan said, lower impedance means that an amp has to supply more current. Perhaps higher end speaker manufacturers build their products assuming that the people who can afford them can also afford better amps. A lower impedance will allow a speaker to play louder, but it takes a better amp to drive it.

 

[mazersteven]

You got me curious, so I did a Google search and came across this (among many other, but it's the only one that I've read so far). Pretty easy to follow.

I have read that before. Good Stuff

 

[mazersteven]

A lower impedance will allow a speaker to play louder, but it takes a better amp to drive it.

Is that true? Because Klipsch are 8 ohms and play "Loud".

 

[Adam]

Is that true? Because Klipsch are 8 ohms and play "Loud".

Perhaps all other things being equal, a lower impedance would allow a speaker to play louder. I'm guessing that there are other factors involved.

This is one reason why I'm so happy that most consumer products are built for the masses (of which, I'm part). I buy speakers and an amp, I hook them up, and I don't have to be an electrician to get it to work.

 

[AcuDefTechGuy]

Impedance is the electrical characteristic of a speaker that restricts ("impedes") the flow of power from your receiver, or amplifier. The impedance value of a loudspeaker is expressed in Ohms.

So, is there any benefit to having a lower Ohm speaker?

And why are so many higher end speakers 4 ohms? Is there a sound quality difference? Is it the driver that causes the impedance, or the whole speaker design.

Yeah, I've asked that question also.

My BP7000, CLR3000, & SM450 have a stated nominal impedance of 8 ohms, 4 ohms, & 4 ohms, respectively. But according to Home Theater Magazine, the Minimum impedance were 2.9 ohms, 2.1 ohms, and 2.1 ohms, respectively. But a DefTech rep told me that you only need a minimum of 20 wpc/8 ohms amp to power these speakers because they have an efficiency of 92 dB.

The DT Rep also said that if you have a choice, use the smaller ohms amp, which I recall is the OPPOSITE of what The Audio Critic preaches. I think TAC says that if you have a choice, the higher ohms is better.

 

[Haoleb]

That's a good question. I'm not sure why speaker designers choose an impedence of 4 ohm for their designs.

The other day, someone told me that 4 ohm speakers should be a light load for the amplifier because there is little resistance to current flow so more current should flow.

But the reality is that the amp will be stressed more at low impedence loads because it has to deliver more current, sometimes much more, and if it can't, then it will clip and produce severe distortion.

Besides, impedence varies with frequency.

--Regards,

As you have been able to tell, Perhaps said person should be considered, Dare i say, Unreliable for advice!

The DT Rep also said that if you have a choice, use the smaller ohms amp, which I recall is the OPPOSITE of what The Audio Critic preaches. I think TAC says that if you have a choice, the higher ohms is better.

What exactly do you mean by "smaller ohms amp"? Are you talking output impedance? Also keep in mind that the impedance rating of a speaker is an average of the readings from the entire frequency spectrum. There are places that dip lower and places that go higher.

 

[Vaughan Odendaa]

In my opinion, I think the question of speaker impedence is irrelevant because taking impedence by itself is oversimplifying the issue.

Impedence varies with frequency and so even if a speaker has a nominal impedence of 4 ohms, that doesn't mean that its' 4 ohms across it's bandwidth. Power could drop to 4 ohms and then the impedence could spike to 8 ohms, or to 16 ohms and then to 2 ohms for a split second.

Just remember that music is dynamic and the signal is constantly changing, which means that frequency is constantly changing too and power demands are changing every single second.

Having an amp deliver lots of power into low impedence loads so that transients will be reproduced properly is a good thing though. Dynamic peaks are what require lots of power. Perhaps someone more knowledgeable can explain the possible reasons behind speaker manafactures churning out 4 ohm designs.

Cheers.

--Regards,

 

[mtrycrafts]

Is that true? Because Klipsch are 8 ohms and play "Loud".

No, that is not true. It is conditional as you showed with a good example.

 

[mtrycrafts]

As you have been able to tell, Perhaps said person should be considered, Dare i say, Unreliable for advice!
.

Yes, how true. One should run the other way from that person. Or, just yawn.

 

[mtrycrafts]

Yeah, I've asked that question also.

My BP7000, CLR3000, & SM450 have a stated nominal impedance of 8 ohms, 4 ohms, & 4 ohms, respectively. But according to Home Theater Magazine, the Minimum impedance were 2.9 ohms, 2.1 ohms, and 2.1 ohms, respectively. But a DefTech rep told me that you only need a minimum of 20 wpc/8 ohms amp to power these speakers because they have an efficiency of 92 dB.

The DT Rep also said that if you have a choice, use the smaller ohms amp, which I recall is the OPPOSITE of what The Audio Critic preaches. I think TAC says that if you have a choice, the higher ohms is better.

Nominal is just that, some sort of an averaged impedance. Minimum, again is just that, that at some frequency, the lowest impedance of that speaker is as you stated.

Well, the rep said minimum that may or may not be enough. Spl sensitivity is is measure as stated by the maker, at 1m distance with either 2.83V applied at the speaker terminal, or 1 watt applied. But, one needs to examine that too, since 2.83V on a 4 Ohm speaker is in fact 2 watts of power and 1watts on 8 Ohm speaker.

Also, the distance you sit from the speaker matters as spl level drops 6dB each time you double distance in an open space; normal rooms are less.
So, if you are 4m from the speaker, make it easy, that would be a 12dB spl drop. Your 92dB spl sensitive speaker would be 80dB spl at the listening position. If you drive it with 20 watts which is 13dB spl sound increase, you are back at 93 dB spl at the listening position and you are out of gas

I am not sure what the smaller ohm is referring to. If the speaker, then the rep is wrong. I have yet to find TAC to be wrong as he has/had an expert tech adviser, Dr. David Rich, now writes for the The $ensible Sound. You should read some of his articles. I think he works for Bell Labs.

An amp needs to be rated for 4 Ohms to drive difficult loads.

 

[mtrycrafts]

Perhaps all other things being equal, a lower impedance would allow a speaker to play louder. I'm guessing that there are other factors involved.

Well, we all guess at times.
You cannot make such a blanket statement though as it is very conditional as was shown by that very high sensitive speaker at 8 ohms, some going over 100dB spl, 1m/1w.
Some companies just cannot design with higher impedance as part of the speaker

 

[Ampdog]

A few additional remarks,

The question has been asked: Why 4 ohms?

It is in a sense traditional, but a lot of practice is also involved. About 50 years ago in the tube era 15 ohms was the hi-fi standard. It was something of a convenient number of voice coil turns not giving too much mass but not too low an impedance, for matching to tube output transformers.

Came transistors, with initially a maximum voltage of some 60Vp capable of up to 10Ap, only about 20W could be given to a 15 ohm loudpspeaker, while better use of the specs could be made with a lower impedance, and 8 ohms became the norm. But in car systems with 14V maximum, only about 3W would be possible with an 8 ohm loudspeaker, so 4 ohms would be better, and so on - a very general explanation.

Why not lower? Well, cable losses began to be meaningful, and for 70W into 2 ohms one would need transistors capable of 35Ap at only 30V safely. This is "unbalanced"; transistors come these days at say 100V and 20A easily, which favours a higher impedance. Again a very general explanation, just to give some perspective.