Why 6 ohm receivers and speakers?

[zuzu]

Why was 6 ohm introduced? If you have 6 ohm connectios on your receiver does that mean you must connect 6 ohm speakers?

[Trey Cannon]

You are asking about Impedance.

Well in truth there is no such thing as a 6 ohm receiver or speaker.

Impedance changes with frequency. So, unless your speakers only play one Frequency, they will have a "bandwidth" of impedance.

A speaker can have a min. Z  (Z = impedance) of 4 ohms and a max X of 60 ohms and still be called an 8 ohm speaker.

When audio started it was thought that the consumer would understand things better if an amp and speaker had a number that would help to "match" them.   8 ohms was a good number. 

For example, the forte was ratted at 4 ohms, 6 ohms and 8 ohms. They all were / are true.

IMHO we should use min Z for rattings.  It is the worst case / the most load on the amp. 

I hope this helps a little.

[colterphoto1]

Some understanding of this 'specification' can come from the meaning of the word commonly used with the impedence of a speaker, reciever, or amp.

NOMINAL generally derives from name.
A nominal quantity (e.g., length, diameter, volume, voltage, value) is
generally the quantity according to which some item has been named or
is generally referred to. Such a nominal value may have no real
relation to the item being referred to. For example, a type of battery
that has an actual voltage of 1.62 V but is commonly called a "1.5 volt battery" has a nominal voltage of 1.5 V (which cannot be measured anywhere).

The term has specific meanings in the following areas:

• In economics a nominal value indicates the listed value of an item in a monetary currency as opposed to the 'real' value in terms of purchasing power. See real versus nominal value. A nominal interest rate
  may refer to either a rate of interest that is not re-stated to correct
  for compounding, or an interest rate that does not take into account inflation (to derive the real interest rate).
• In engineering,
  nominal signifies the product is according to engineering
  specifications and not the common equivocation that it is "normal". The
  use of the phrase "all systems nominal" at NASA indicate that telemetry is reading as expected from historical data trends.
• 
  
• In linguistics, a "nominal"
  is a word or group of words functioning as a noun. The word is also
  sometimes used as a shortened form of "nominal phrase", a synonym for "noun phrase". "Nominal" can also mean a sequence of one or more nouns that do not form a complete noun phrase.
• In statistics, nominal data is a form of categorical data where the order of the categories is not significant. This is sometimes contracted to nominals.
• In law, nominal damages
  may be assessed by a jury or judge in a lawsuit when it is found that
  the defendant committed the act complained of by the plaintiff, but
  that no harm was suffered by the plaintiff as a result.

[zuzu]

Thanks guys. So with this nominal 6 ohm home theater receiver, that has 6 wire clamp-ons on the back of the receiver, I can connect five 8 ohm speakers and a 4 ohm powered sub.. The receiver also says 600 watts 100 watts per speaker. Now various speakers say things like nominal [there is our word] 40 watts to max 90 watts. What do I have to look for or watch out for regard to wattage matching?

[pzannucci]

You also have to wonder if it is to bump up the specs. Most amps put out more power (supposedly) into lower impedence loads. That looks 100watts at 6 ohms looks better than 65 at 8.[^o)]

[Trey Cannon]

Yes you can use the two products together. 

Peter, you are right on man.