6 ohm speakers

[walter duque]

I must admit I know nothing about speakers when it comes to the technical side. Almost all speakers I see have a 4 or 8 ohm rating. Mine are rated at 6 ohms. Is there a reason for that?

[FirstReflection]

The impedance rating on your speakers (given in ohms) is almost always the nominal impedance - which is roughly just an average. The actual impedance at any given frequency can vary greatly. A speaker might have a 3 ohm impedance at 200 Hz, but a 32 ohm impedance at 8000Hz. So the nominal rating is just an average taken over the entire frequency range of the speaker.

A lower impedance means that the speaker will call for more amps from your amplifier. This is very rough, but it is generally easier to deliver more volts and tougher to deliver more amps.

You can think of it like water being pushed through a hose. The impedance is like the size of the hose. A big, fat hose does very little to prevent the flow of water - so that would be low impedance. A skinny hose will make it tougher for water to flow, so that would be high impedance.

Volts are like the water pressure. It doesn't take a lot of pressure to get a lot of water to flow through a big, fat hose. But it takes lots and lots of pressure to get a lot of water to flow through a skinny hose. For most amps, it's pretty easy to increase the "water pressure" (ie. volts), so a skinny hose (high impedance) isn't a problem for amplifiers in general.

Amps are like the actual amount of water. A big, fat hose lets lots of water through - even without a lot of pressure. A skinny hose doesn't let very much water through.

Think of the amount of water being like the number of electrons. Lots of amps means lots of electrons. So a big, fat pipe (low impedance) means lots of water (electrons/amps) even with low pressure (volts). It's tougher for amplifiers to deliver lots and lots of electrons - much tougher than simply increasing the water pressure (volts).

So, in a general sense, it is easier to power a speaker that has higher impedance.

The ohm rating is just basically an average, so there are several ways that your speaker could wind up with a 6ohm nominal impedance rating.

One way is that it has several drivers (tweeters, woofers) that are wired in both series and parallel. When things are wired in series, it's like making a longer hose without making the hose any wider. Thus, the impedance goes up - still the same width of hose, just longer. When things are wired in parallel, it's like adding a second hose right beside the first hose. So impedance goes down - you basically have a fatter pipe (two hoses instead of one), but they aren't any longer and they didn't get skinnier all of a sudden.

So when you have a combination of things wired in series AND parallel, you can get some different and a little bit more unusual impedance ratings by the end of it.

Another reason why your speakers might be rated at 6ohms instead of the more typical 4 or 8 ohms is because your speakers vary A LOT at different frequencies. Maybe your speaker dips WAY down low to just 1 or 2 ohms at certain frequencies, while at other frequencies, it stays around 8 or 16 ohms. Remember, the nominal rating is an average. So if your speaker has certain frequencies where it dips really low, that's going to lower the overall average and you'll wind up with a speaker that would normally get an 8ohm nominal rating, but due to those few really low dips, it winds up with an average impedance that is closer to 6 ohms or something.

In general, for the sake of your amplifier, it's best if the lowest dips in impedance at any given frequency stay above 3ohms or so. THX calls for no dips lower than 3.2 ohms at any point. That way, the amplifier never has to try and deliver a crazy number of electrons all of a sudden. Keep that hose fairly skinny and it's easier to control the flow of water

Hope that helps!

[TLS Guy]

I must admit I know nothing about speakers when it comes to the technical side. Almost all speakers I see have a 4 or 8 ohm rating. Mine are rated at 6 ohms. Is there a reason for that?

What the manufacturer says usually means nothing. If it's not a bookshelf assume it is a four ohm speaker and you won't go wrong as a rule. Even with bookshelves they are often a lot lower than stated.

[walter duque]

The impedance rating on your speakers (given in ohms) is almost always the nominal impedance - which is roughly just an average. The actual impedance at any given frequency can vary greatly. A speaker might have a 3 ohm impedance at 200 Hz, but a 32 ohm impedance at 8000Hz. So the nominal rating is just an average taken over the entire frequency range of the speaker.

A lower impedance means that the speaker will call for more amps from your amplifier. This is very rough, but it is generally easier to deliver more volts and tougher to deliver more amps.

You can think of it like water being pushed through a hose. The impedance is like the size of the hose. A big, fat hose does very little to prevent the flow of water - so that would be low impedance. A skinny hose will make it tougher for water to flow, so that would be high impedance.

Volts are like the water pressure. It doesn't take a lot of pressure to get a lot of water to flow through a big, fat hose. But it takes lots and lots of pressure to get a lot of water to flow through a skinny hose. For most amps, it's pretty easy to increase the "water pressure" (ie. volts), so a skinny hose (high impedance) isn't a problem for amplifiers in general.

Amps are like the actual amount of water. A big, fat hose lets lots of water through - even without a lot of pressure. A skinny hose doesn't let very much water through.

Think of the amount of water being like the number of electrons. Lots of amps means lots of electrons. So a big, fat pipe (low impedance) means lots of water (electrons/amps) even with low pressure (volts). It's tougher for amplifiers to deliver lots and lots of electrons - much tougher than simply increasing the water pressure (volts).

So, in a general sense, it is easier to power a speaker that has higher impedance.

The ohm rating is just basically an average, so there are several ways that your speaker could wind up with a 6ohm nominal impedance rating.

One way is that it has several drivers (tweeters, woofers) that are wired in both series and parallel. When things are wired in series, it's like making a longer hose without making the hose any wider. Thus, the impedance goes up - still the same width of hose, just longer. When things are wired in parallel, it's like adding a second hose right beside the first hose. So impedance goes down - you basically have a fatter pipe (two hoses instead of one), but they aren't any longer and they didn't get skinnier all of a sudden.

So when you have a combination of things wired in series AND parallel, you can get some different and a little bit more unusual impedance ratings by the end of it.

Another reason why your speakers might be rated at 6ohms instead of the more typical 4 or 8 ohms is because your speakers vary A LOT at different frequencies. Maybe your speaker dips WAY down low to just 1 or 2 ohms at certain frequencies, while at other frequencies, it stays around 8 or 16 ohms. Remember, the nominal rating is an average. So if your speaker has certain frequencies where it dips really low, that's going to lower the overall average and you'll wind up with a speaker that would normally get an 8ohm nominal rating, but due to those few really low dips, it winds up with an average impedance that is closer to 6 ohms or something.

In general, for the sake of your amplifier, it's best if the lowest dips in impedance at any given frequency stay above 3ohms or so. THX calls for no dips lower than 3.2 ohms at any point. That way, the amplifier never has to try and deliver a crazy number of electrons all of a sudden. Keep that hose fairly skinny and it's easier to control the flow of water

Hope that helps!

Thanks for taking the time to explaining this to me. Now I have a better idea how it works.

[Pyrrho]

The impedance rating on your speakers (given in ohms) is almost always the nominal impedance - which is roughly just an average. The actual impedance at any given frequency can vary greatly. A speaker might have a 3 ohm impedance at 200 Hz, but a 32 ohm impedance at 8000Hz. So the nominal rating is just an average taken over the entire frequency range of the speaker.

A lower impedance means that the speaker will call for more amps from your amplifier. This is very rough, but it is generally easier to deliver more volts and tougher to deliver more amps.

You can think of it like water being pushed through a hose. The impedance is like the size of the hose. A big, fat hose does very little to prevent the flow of water - so that would be low impedance. A skinny hose will make it tougher for water to flow, so that would be high impedance.

Volts are like the water pressure. It doesn't take a lot of pressure to get a lot of water to flow through a big, fat hose. But it takes lots and lots of pressure to get a lot of water to flow through a skinny hose. For most amps, it's pretty easy to increase the "water pressure" (ie. volts), so a skinny hose (high impedance) isn't a problem for amplifiers in general.

Amps are like the actual amount of water. A big, fat hose lets lots of water through - even without a lot of pressure. A skinny hose doesn't let very much water through.

Think of the amount of water being like the number of electrons. Lots of amps means lots of electrons. So a big, fat pipe (low impedance) means lots of water (electrons/amps) even with low pressure (volts). It's tougher for amplifiers to deliver lots and lots of electrons - much tougher than simply increasing the water pressure (volts).

So, in a general sense, it is easier to power a speaker that has higher impedance.

The ohm rating is just basically an average, so there are several ways that your speaker could wind up with a 6ohm nominal impedance rating.

One way is that it has several drivers (tweeters, woofers) that are wired in both series and parallel. When things are wired in series, it's like making a longer hose without making the hose any wider. Thus, the impedance goes up - still the same width of hose, just longer. When things are wired in parallel, it's like adding a second hose right beside the first hose. So impedance goes down - you basically have a fatter pipe (two hoses instead of one), but they aren't any longer and they didn't get skinnier all of a sudden.

So when you have a combination of things wired in series AND parallel, you can get some different and a little bit more unusual impedance ratings by the end of it.

Another reason why your speakers might be rated at 6ohms instead of the more typical 4 or 8 ohms is because your speakers vary A LOT at different frequencies. Maybe your speaker dips WAY down low to just 1 or 2 ohms at certain frequencies, while at other frequencies, it stays around 8 or 16 ohms. Remember, the nominal rating is an average. So if your speaker has certain frequencies where it dips really low, that's going to lower the overall average and you'll wind up with a speaker that would normally get an 8ohm nominal rating, but due to those few really low dips, it winds up with an average impedance that is closer to 6 ohms or something.

In general, for the sake of your amplifier, it's best if the lowest dips in impedance at any given frequency stay above 3ohms or so. THX calls for no dips lower than 3.2 ohms at any point. That way, the amplifier never has to try and deliver a crazy number of electrons all of a sudden. Keep that hose fairly skinny and it's easier to control the flow of water

Hope that helps!

Nominal impedance is NOT the average impedance. Generally speaking, listing the average impedance would be totally useless. The nominal impedance is supposed to be what you can safely pretend the overall impedance is. As such, it tends to be near the minimum impedance of the speaker. If the speakers reached your hypothetical 1 ohm, it would probably be an extremely difficult to drive speaker and absolutely ought not be rated at 6 ohms nominally. Of course, some companies are run by worthless liars who incorrectly rate their speakers, but good companies rate them properly so that one can use the nominal rating to judge whether a particular amplifier can deal with the speaker or not.

(I don't know what their current policy is, but McIntosh used to have a policy that their nominal impedance ratings for their speakers would be such that they never had a minimum impedance lower than 10% less than the nominal rating, or in other words, no lower than 7.2 ohms for a nominally 8 ohm speaker. That is the sort of policy that a good company will have, but evil lying bastards abound in business, so you should try to find a professional review in which they measured the speaker to find out the minimum impedance of whatever speaker you are considering [some manufacturers also state the minimum impedance of a speaker, and then you need not find a review for this information]. And pay attention to which companies are liars about this sort of thing for future use, in case you can't find a review of the particular model in question, to have some idea of which companies are not generally trustworthy.)

In any case, the nominal impedance is not determined by the average of the impedance curve.

[PENG]

[QUOTE]

This is very rough, but it is generally easier to deliver more volts and tougher to deliver more amps.

Good thing you say this is very rough. I don't think you can generalize this so much. I am not sure if it is easier for the output transistors to deliver more volts. They are not transformers. If an amp cannot handle 4 ohm speakers it likely cannot handle 16 ohm speakers either. Obviously there are far more 4 ohm speakers than 16 ohm speakers on the market but that does not mean high voltage requirement is not a problem for amps.

It's tougher for amplifiers to deliver lots and lots of electrons - much tougher than simply increasing the water pressure (volts).

Not totally correct, it is not easy to increase the voltage either, not beyond what the device is rated for.

So, in a general sense, it is easier to power a speaker that has higher impedance.

That is correct if you are comparing 8 ohm nominal and 4 ohm nominal speakers. To me, while 8 ohm is a higher impedance than 4 ohm, I would rather consider 8 ohm as the norm/average, while 4 ohm as low, and 16 ohm as high. So it is easier to power a speaker with nominal impedance of 8 ohm, but difficult to power 4 ohm and 16 ohm speaker. An average AVR will not do a good job driving 4 ohm and 16 ohm speakers.

Don't get me wrong, you did a great job explaining something complex in a way most people can understand. I just don't want people to think that it is easier to drive high (as opposed to higher, meaning higher than 4 ohm) impedance load without defining what is "high".

Just to preamble TLSG, I agree with him the rated impedance given by manufacturers are of little use. Whenever I say 4, 8, or 16 ohm I am assuming they are nominal and in each case they have exactly the same impedance vs freq curve. I do this just so there is a base line for comparison purposes.

[FirstReflection]

Thanks to those who have contributed more info and clarification to what I wrote.

Yes, I should have been clearer in saying that nominal impedance is not the same thing as just the mathematical average. I tried to sort of convey that by repeatedly mentioning that everything I was explaining was very "rough". I was simply trying to give a very basic idea that someone without any technical knowledge could understand

When I wrote that the nominal impedance is very roughly just an average, I only meant to convey the idea that something like an 8 ohm nominal impedance speaker doesn't simply perform with 8 ohm impedance regardless of the frequency that it's playing. Instead, it might dip down to 3 ohms at some points and go up to 30 ohms at others, but still be given an 8 ohm nominal rating. Most people are familiar with the idea of an average, so I simply used that language because I figured it would be easier to grasp to just get a very basic understanding of why a speaker might be rated at 6 ohms nominal instead of 8 or 4 - sorry for any confusion that I might have caused

Same sort of thing with how I tried to explain - very roughly - how the amplifier reacts. I just meant to convey the idea that, in general, you are more likely to have a problem trying to drive low impedance speakers or speakers that dip to extremely low impedances at certain frequencies vs. driving higher impedance speakers or speakers that have high impedance peaks at certain frequencies. For someone who's just trying to get a basic idea and doesn't have a lot of technical background, I just wanted to convey the general idea that a very low impedance is more likely to give your amplifier some problems. In general, that does hold true and it's a good, basic "rule of thumb" to keep in mind is all

[KEW]

I must admit I know nothing about speakers when it comes to the technical side. Almost all speakers I see have a 4 or 8 ohm rating. Mine are rated at 6 ohms. Is there a reason for that?

I don't think anyone has yet pointed out that many companies (or perhaps your speaker company on a different day) would take a speaker like yours and call it either 4 ohm or 8 ohm to stick with more common conventions.

It is pretty curious that on that spec. sheet, there are many numbers which are measured and specified with a decent degree of precision - then there is the impedance rating which can vary as much as 50% based on marketing preferences or whatever whim is at play that day!

[PENG]

Same sort of thing with how I tried to explain - very roughly - how the amplifier reacts. I just meant to convey the idea that, in general, you are more likely to have a problem trying to drive low impedance speakers or speakers that dip to extremely low impedances at certain frequencies vs. driving higher impedance speakers or speakers that have high impedance peaks at certain frequencies. For someone who's just trying to get a basic idea and doesn't have a lot of technical background, I just wanted to convey the general idea that a very low impedance is more likely to give your amplifier some problems. In general, that does hold true and it's a good, basic "rule of thumb" to keep in mind is all

I did recognize that you were only "roughing" things out and tried to make things simple. I might have sounded a little like nit picking while I was truly trying to make clear the point that both high current and high voltage present a challenge and one is not necessarily easier than the other. It really depends on how low is low and how high is high.

Thank you for taking it in well.

[TLS Guy]

It's tougher for amplifiers to deliver lots and lots of electrons - much tougher than simply increasing the water pressure (volts).

PENG

Not totally correct, it is not easy to increase the voltage either, not beyond what the device is rated for.

That is true.

For transistor amps the power supply rail voltage to the output devices determines the voltage available. It can never be higher than that and is always a little lower. The design voltage must be less breakdown voltage of the output devices selected.

The current available is determined by the devices selected and the adequacy of the power supply.

Now in a good amp as the impedance drops current will increase and voltage remain constant to a certain point. So a really powerful amp will double its power when going from 8 to 4 ohms and if it is really good double it again when driving a 2 ohm load.

The build and design quality will determine the point where current becomes limited and the voltage drop and or the trigger protection and risk blowing the output devices.

If power is only quoted into 8 ohms, it is a good bet the device is severely current limited, to the extent that power will be halved when driving a four ohm load rather than doubled. There will of course be all scenarios in between.