Here's the summary: that switch on the back defines the minimum speaker impedances you must use and really is only worth paying attention to when you're running four speakers AT THE SAME TIME. And, as Audioholics said, its real purpose is NOT this, but to pass a test.
About the switch: the amplifier MUST PASS tests to be able to be sold as specified at particular wattages. The idea that these switches are only for the purpose of passing the tests is a complete ripoff, but it's the only explanation for these switches that I've seen that makes sense!
I was around when they instituted the test procedures. They were supposed to make things more fair and create specs that were comparable from unit to unit and brand to brand. Leave it to someone to figure out a way to cheat the system with a switch.
On July 2, 2015 at 11:10, NEZBO said...
When reading the back of the switch on the amp, The switch wire diagram notes that when selected to 4 ohm, A and B channels will run on 4 ohm. Since I only have 2 4 ohm speakers being used, I will only need to use the A channel (left and right).
How about what looking at how the switch is actually labeled?
The overall box is labeled IMPEDANCE SELECTOR. Some have taken this to mean that some impedance inside the amp is being selected. Nope. The switch is to be put to the impedance of what you're going to
connect to the amp. (And as we learned from Audioholics, that's only relevant when you're testing or when you're putting the volume up to eleven.)
The left position of the switch is labeled LOW. There's a line to a box that contains these words:
A OR B: 4 Ohm min. /speaker
A + B: 8 Ohm min. /speaker
The right position of the switch is labeled HIGH. There's a line to a box that contains these words:
A OR B: 6 Ohm min. /speaker
A + B: 12 Ohm min. /speaker
The diagram on the back of the unit is confusing.
Read below.
It mentions nothing about testing purposes only.
True, and this is the big ripoff. To pass a test, they put something on the receiver that nobody in their right mind would use if they knew it was just for passing a test.
It simply says it is an impedance switch so that the correct ohm load will be selected for the speakers being used.
But you've got the purpose or the requirement backwards. It does not say the correct ohm load will be selected for the speakers being used. The speakers are the ohm load that they are and nothing can change that. The switch selects something inside the amp that they don't bother to tell us about. It selects something about the amp to go along with the load you present to it.
The misleading thing to me is that the switch claims it is an impedance switch only.
What else might it do? But remember that it's supposed to be set to match the impedance that you're connecting to it. Maybe that makes more sense.
Look, you can stop reading if you get this:
this switch tells you that it has to be in the proper place to match your load when you use BOTH A AND B.The diagram says to me that if you want to hook up (4) speakers that are 4ohm then select to 4 ohm. If you want to hook up (4) speakers that are 8ohm, select 8 ohm. If you want to just hook up (2) speakers, select to the proper ohm load on the switch.
Three points here:
1)It says nothing of the kind. It does not have a "select 4 ohm" or "select 8 ohm." It has "LOW" and "HIGH." If you say it says something different, how can you then come to any valid conclusions about what it says?
2)It NEVER says that you can connect 4 four ohm speakers... at the same time. The word "OR" is being ignored. That's a detail that's gone lost in this discussion up to now.
3)You are completely ignoring the OR and AND aspect of the labels.The note for LOW says that if you are going to use a speaker ON
EITHER A
OR B, but not both, then you must use 4 ohm (minimum) speakers. If you are going to use a speaker
BOTH ON A
AND B, you must use 8 ohm (minimum) speakers. Incidentally, in this case you could use just A
or B.
The note for HIGH says that if you are going to use a speaker ON
EITHER A
OR B, then you must use 6 ohm (minimum) speakers. If you are going to use a speaker on
BOTH A
AND B, you must use 12 ohm (minimum) speakers. And in this case, too, you could use A
or B if you like.
Highfigh mentions this to actually be a test purpose only switch. Good to know if that is correct.
True. It never occurred to me that it was. I just went with it and never had any problems, mostly because I do surround... and who the hell wants an extra left and right that won't have center information in a surround system? "Yeah, here's my new surround system! I've got 5.1 in the living room, and out on the patio I've got left and right, but you'll have to lean toward the screen door to hear the dialog and rear effects coming from the living room!"
Either that or your client has to put the system in two channel mode any time they want to use speaker B. Not worth the trouble.
