Difference between 8 ohm & 6 ohm speakers

[srk16]

Are there any advantages or disadvantages of using 8 ohm speakers over 6 ohm speakers to home theatre a/v receivers ?

 

[Ed Seedhouse]

Are there any advantages or disadvantages of using 8 ohm speakers over 6 ohm speakers to home theatre a/v receivers ?

For all practical purposes there is no difference whatsoever.

 

[croseiv]

The only disadvantage I can think of is that assuming all else is equal between the two speakers, the 6 ohm speaker will draw more power from the amp. But that's not a major one. I think most receivers can handle a 6 ohm load pretty well.

 

[lsiberian]

The only disadvantage I can think of is that assuming all else is equal between the two speakers, the 6 ohm speaker will draw more power from the amp. But that's not a major one. I think most receivers can handle a 6 ohm load pretty well.

Is this really a disadvantage?

More power means more volume of course the difference is negligible.

Your best bet is to use the number of low drivers to determine impendance.

a 2 1/2 way speaker will almost always have a true impendance of 4 ohms.

Many specs are dishonest.

 

[adwilk]

While not completely useless, the nominal impedance ratings are.. well... They can be fairly misleading. Its very likely that some 8ohm "rated" speakers have impedance dips lower than a 6ohm speaker. These numbers just arent absolute. If your amp shuts off, make some adjustments...

 

[3db]

Is this really a disadvantage?

More power means more volume of course the difference is negligible.

Your best bet is to use the number of low drivers to determine impendance.

a 2 1/2 way speaker will almost always have a true impendance of 4 ohms.

Many specs are dishonest.

Can you substantiate this claim? And what is true impedance since impedance varies with frequency?

 

[3db]

Are there any advantages or disadvantages of using 8 ohm speakers over 6 ohm speakers to home theatre a/v receivers ?

One can't really answer that question accurately without knowing the impedance curves of the speakers? It can be that some 8 ohm speakers could have its impedance drop below 4 ohms where as a 6 ohm speaker may have a much tighter impedfance curve and barely drop below 5 ohms. There are just too many variables to answer that question correctly. What you may want to ask is what speakers you consider using with what AVR in a room with X dimesnions listening to low, moderate or loud listening levles. This would help us out alot more in answering your questions.

 

[Loren42]

Is this really a disadvantage?

More power means more volume of course the difference is negligible.

Your best bet is to use the number of low drivers to determine impendance.

a 2 1/2 way speaker will almost always have a true impendance of 4 ohms.

Many specs are dishonest.

Umm, that assumes that all things are equal. In other words, both systems have the same SPL per watt.

Power is simply Volts multiplied by Amps. You can use the old formula Volts = I * R, when I = Amps and R = resistance in Ohms, to look at it any way you want.

Any downside will probably be limited to the amp you use to drive the speakers, but if the amp is rated to drive 4 ohms, then it is probably capable to drive 6 and 8 ohms just as well.

 

[TLS Guy]

Can you substantiate this claim? And what is true impedance since impedance varies with frequency?

A 2.5 way speaker has to be 4 ohms or less effectively. The bass drivers can not be more than 8 ohms, or the speaker would be very insensitive on a 2.83 volt one meter rating. Progressively below 600 Hz the drivers are in parallel. The power divide, is 400 Hz and the impedance is dropping in half below that point, so 2/3 of the amp power will be delivered into an impedance of four ohms or less.

Speaker manufacturers impedance ratings convey no information of importance.
Looking at the design and driver configuration will give you much more insight as to what is really going on.

 

[highfigh]

Is this really a disadvantage?

More power means more volume of course the difference is negligible.

Your best bet is to use the number of low drivers to determine impendance.

a 2 1/2 way speaker will almost always have a true impedance of 4 ohms.

Many specs are dishonest.

Speaker impedance ratings are a nominal rating. Would you rather have the manufacturer show a graph and let you determine their impedance rating? Should they just rate them by DC resistance? How about Min, Max and Average?

Dishonest? How? Come up with a better way to indicate the impedance, if you can.

 

[davidtwotrees]

Specs for my Canton Towers.......

Type Floorstanding speaker
Engineering Principle 3-way Bass reflex system
Nom. /Music power handling 250 / 380 watts
SPL (1 watt/1m) 89 db (1 W, 1 m)
Frequency response 20...40.000 Hz
Crossover frequency 150 / 3.200 Hz
Woofer 1 x 310 mm (12''), Cellulose/graphite
Midrange 2 x 180 mm (7''), aluminum
Tweeter 1 x 25 mm (1''), aluminum-manganese
Nominal Impedance 4...8 ohms
Dimensions (WxHxD) 20 x 115 x 47.5 cm
(7.9'' x 45.3'' x 18.7'')
Weight 42 kg
Special Features DC-technology
Gold plated bi-wiring/bi-amping screwclamp terminals


So. Above find the spec for my Canton Karat L800DC towers. They list the nominal impedance as 4....8 ohms. What does this mean?

 

[Pyrrho]

Speaker impedance ratings are a nominal rating. Would you rather have the manufacturer show a graph and let you determine their impedance rating? Should they just rate them by DC resistance? How about Min, Max and Average?

Dishonest? How? Come up with a better way to indicate the impedance, if you can.

There is no standardization for the manufacturers' "nominal" rating, so I would say that it is not terribly meaningful. Minimum impedance is, however, a meaningful concept, though how much it matters will depend upon the frequency where the minimum occurs (basically, the higher the frequency, the less it will matter due to the fact that relatively little power is needed at high frequencies). I personally would prefer to see a graph and make the determination of compatibility with my amplifier for myself.

But since most people would not do well with such a method, it would be good if there were some standardization of the concept of "nominal" impedance so that it could be depended upon.

 

[Pyrrho]

Type Floorstanding speaker
Engineering Principle 3-way Bass reflex system
Nom. /Music power handling 250 / 380 watts
SPL (1 watt/1m) 89 db (1 W, 1 m)
Frequency response 20...40.000 Hz
Crossover frequency 150 / 3.200 Hz
Woofer 1 x 310 mm (12''), Cellulose/graphite
Midrange 2 x 180 mm (7''), aluminum
Tweeter 1 x 25 mm (1''), aluminum-manganese
Nominal Impedance 4...8 ohms
Dimensions (WxHxD) 20 x 115 x 47.5 cm
(7.9'' x 45.3'' x 18.7'')
Weight 42 kg
Special Features DC-technology
Gold plated bi-wiring/bi-amping screwclamp terminals


So. Above find the spec for my Canton Karat L800DC towers. They list the nominal impedance as 4....8 ohms. What does this mean?

It probably means that they are properly called 4 ohms nominally, but do not have any really nasty dips below that that will fry the typical amplifier designed for 8 ohm speakers. This is assuming that they are not simply evil bastards who are guiding people to destroy their 8 ohm minimum amplifiers, which, for all I know, they might be.

 

[Pyrrho]

Are there any advantages or disadvantages of using 8 ohm speakers over 6 ohm speakers to home theatre a/v receivers ?

Given the lack of standardization for the determination of nominal impedance, there is no way to know whether it would make any difference or not. In practice, it is probably of no concern whatsoever, unless one or both is really rated very improperly.

 

[3db]

I have a pair of PSB Image T45s which are a 2.5 way design and they are nominally rated at 6 ohms which infers that during most of teh frequency curve, they sit at or above 6 ohms. I would also think that would dip into the 4 ohm region as well but to state that 2.5 way speakers are 4 ohms or less is inaccurate.

A 2.5 way speaker has to be 4 ohms or less effectively. The bass drivers can not be more than 8 ohms, or the speaker would be very insensitive on a 2.83 volt one meter rating. Progressively below 600 Hz the drivers are in parallel. The power divide, is 400 Hz and the impedance is dropping in half below that point, so 2/3 of the amp power will be delivered into an impedance of four ohms or less.

Speaker manufacturers impedance ratings convey no information of importance.
Looking at the design and driver configuration will give you much more insight as to what is really going on.

 

[Pyrrho]

A 2.5 way speaker has to be 4 ohms or less effectively. The bass drivers can not be more than 8 ohms, or the speaker would be very insensitive on a 2.83 volt one meter rating. Progressively below 600 Hz the drivers are in parallel. The power divide, is 400 Hz and the impedance is dropping in half below that point, so 2/3 of the amp power will be delivered into an impedance of four ohms or less.

Speaker manufacturers impedance ratings convey no information of importance.
Looking at the design and driver configuration will give you much more insight as to what is really going on.

That is not correct. Since the impedance of the woofers varies according to frequency, the woofers could have a lower impedance at the higher range than the lower range, so it is possible for a 2.5 way system to have a higher impedance in the deep bass than 4 ohms without having any problems with insensitivity at higher frequencies. Also, the frequencies you specify would not necessarily be the ones used for a particular design.

If you really want to know what is going on, it is best to look at an impedance curve for the speaker, not make a guess based upon the driver configuration.

 

[lsiberian]

Can you substantiate this claim? And what is true impedance since impedance varies with frequency?

A 2.5 way speaker has to be 4 ohms or less effectively. The bass drivers can not be more than 8 ohms, or the speaker would be very insensitive on a 2.83 volt one meter rating. Progressively below 600 Hz the drivers are in parallel. The power divide, is 400 Hz and the impedance is dropping in half below that point, so 2/3 of the amp power will be delivered into an impedance of four ohms or less.

Speaker manufacturers impedance ratings convey no information of importance.
Looking at the design and driver configuration will give you much more insight as to what is really going on.

this is sadly the best answer I can give. I'm glad you agree evidence is our best way to discuss this. Most of the available bass drivers(non subs) are nominally rated a 8 ohms. When you put them in parrallel it cuts the impedance in half. Making the system as a whole rate at 4 ohms. This isn't always the case since there are 16 ohm drivers designed to avoid this. And woofer's can vary in impedance. But generally speaking the most common bass driver hangs out at 8ohms. If you want to use an FR tester on the speaker you could find out for yourself. The industry lacks good standards on this issue. However most amps I've seen can handle 4 ohm load just fine given the user sticks to reasonable listening volumes.

The simple solution is to always get a reputable receiver. Here I never see a brand recommended that I would doubt with a 4 ohm load.

I think practically speaking it's always best to get the speakers you like the most and not worry about nominal impendance.

 

[3db]

this is sadly the best answer I can give. I'm glad you agree evidence is our best way to discuss this. Most of the available bass drivers(non subs) are nominally rated a 8 ohms. When you put them in parrallel it cuts the impedance in half. Making the system as a whole rate at 4 ohms. This isn't always the case since there are 16 ohm drivers designed to avoid this. And woofer's can vary in impedance. But generally speaking the most common bass driver hangs out at 8ohms. If you want to use an FR tester on the speaker you could find out for yourself. The industry lacks good standards on this issue. However most amps I've seen can handle 4 ohm load just fine given the user sticks to reasonable listening volumes.

The simple solution is to always get a reputable receiver. Here I never see a brand recommended that I would doubt with a 4 ohm load.

I think practically speaking it's always best to get the speakers you like the most and not worry about nominal impendance.

I see your logic (8 ohms in parallel is 4 ohms) but its not as simple as that. There is the impedance of the crossover network to consider as well.

 

[gmichael]

About 2 Ohms

You got to see the graph to really know.

 

[TLS Guy]

That is not correct. Since the impedance of the woofers varies according to frequency, the woofers could have a lower impedance at the higher range than the lower range, so it is possible for a 2.5 way system to have a higher impedance in the deep bass than 4 ohms without having any problems with insensitivity at higher frequencies. Also, the frequencies you specify would not necessarily be the ones used for a particular design.

If you really want to know what is going on, it is best to look at an impedance curve for the speaker, not make a guess based upon the driver configuration.

In order to keep the impedance from dipping to four ohms, the speakers would have to be 16 ohms above 600 Hz, which would drop the sensitivity 3 db.

It is not the frequency impedance range you need to average, but the power
spectrum versus frequency The frequency power divide is 400 Hz. Below that area the impedance of a 2.5 way has to drop except for the narrow tuning peaks. As the impedance is halved the amp has to double the power output. So in a 2.5 way design the amp is providing around two thirds of its output into a four ohm load or less. That is the price of diffraction compensation. There is no free lunch.

The bottom line is that most receivers are only delivering half their rated output into properly diffraction compensated speakers. The good news is that this is only a 3db reduction in spl. The reason that the power is halved is that most receivers, although they may tolerate a four ohm load, they can not increase their current beyond what they can push into an eight ohm load at full power. Therefore there power output is halved into a four ohm load. A good external amp will be able to double its power into a four ohm load. This in a nutshell is the essence of the benefit of external amplification.