Hey everyone, I'm trying to understand the speakers A+B setting on my amplifier.
I have a pioneer VSX-821-K, and also other receivers and amplifiers as well, and they all seem to follow the same idea.
When speakers A are on = Anything from 6Ω to 16Ω with 5 channels = Okay!
When speakers B are on = Anything from 6Ω to 16Ω with 2 channels = Okay!
When speakers A + B are on = Only 12Ω to 16Ω is okay, everything else = BAD!
I understand the reasoning behind this, but I can't seem to wrap my head around it. When using A+B, I'm not supposed to hook up my speakers normally? I can only use speakers with an impedance of >12Ω? Where on earth would you even find speakers like this? And what happens if you just use plain old 8Ω speakers on all channels?
I ran my receiver in A+B mode with 8Ω speakers on all channels for ~10 hours yesterday at 80% volume, and the receiver got warm, but nothing really happened. No smoke, flames, burning, anything!
If anyone has any ideas why they rated it like this, please let me know! 😀
I have a pioneer VSX-821-K, and also other receivers and amplifiers as well, and they all seem to follow the same idea.
When speakers A are on = Anything from 6Ω to 16Ω with 5 channels = Okay!
When speakers B are on = Anything from 6Ω to 16Ω with 2 channels = Okay!
When speakers A + B are on = Only 12Ω to 16Ω is okay, everything else = BAD!
I understand the reasoning behind this, but I can't seem to wrap my head around it. When using A+B, I'm not supposed to hook up my speakers normally? I can only use speakers with an impedance of >12Ω? Where on earth would you even find speakers like this? And what happens if you just use plain old 8Ω speakers on all channels?
I ran my receiver in A+B mode with 8Ω speakers on all channels for ~10 hours yesterday at 80% volume, and the receiver got warm, but nothing really happened. No smoke, flames, burning, anything!
If anyone has any ideas why they rated it like this, please let me know! 😀
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Use 16R speakers. 2 X 8R in series.
The amplifier can only produce a certain amount of power. any more and it might fail.
The amplifier can only produce a certain amount of power. any more and it might fail.
The amplifier actually just has 2 channels,and when you select a+b,you put both pairs of speakers in parallel.The amplifier here can drive down to 6 ohms,so if you want 2 pairs, each speaker must have 12 ohms or more,so when paralleling,the impedance get down to 6.Seeing as it is pretty new,it probably has protections against overload and overtemp,and altough not ideal, you can get away with your setup
Ok, just to get a myth out of the way - speaker amps don't really care about the load impedance, and they don't have under-impedance or over-impedance detection or protection. Vacuum tube amps are exceptions, but even then those are the badly-designed ones.
W.r.t. to whether the thing explodes anyway. Won't comment about that nasty IMD I measured on my Marantz under open-load conditions.
Transistors have maximum current ratings. But output current is determined by output voltage and load impedance, so if you exceed the limit, stuff happens. Hence the warning with low load impedance and never about high load impedance, although in both cases, maximum output power is reduced. As long as you don't overwork the amp, it'll be fine with whatever impedance.
W.r.t. to whether the thing explodes anyway. Won't comment about that nasty IMD I measured on my Marantz under open-load conditions.
Transistors have maximum current ratings. But output current is determined by output voltage and load impedance, so if you exceed the limit, stuff happens. Hence the warning with low load impedance and never about high load impedance, although in both cases, maximum output power is reduced. As long as you don't overwork the amp, it'll be fine with whatever impedance.
Manufacturers don't bother themselves with too much explaining. They are sort of saying that they can't vouch for any other use of amplifier other than the one for specified loads. You have observed how the amp warms itself by working with heavier loads. Don't overload it and it will be ok, at least for awhile.
A + B will be bridged mode.
This uses outputs of a and b.
However you need to double the impedance in bridged mode or the amp might fry on full power.
12 ohms is a bit odd so I would use two 8 ohm speakers in series.
This uses outputs of a and b.
However you need to double the impedance in bridged mode or the amp might fry on full power.
12 ohms is a bit odd so I would use two 8 ohm speakers in series.
Thanks for all the replies guys, I still think it's strange that they rate it as such. It makes it seem like you're supposed to use special 12Ω or 16Ω speakers. I'm not sure why they don't just have separate transistors for the B channel, or why not give you the option to only use certain speakers in certain modes, but I digress.
It would also be easier to just rate the amplifier to handle 4Ω loads, that way it would be rated to handle 8Ω speakers even in bridge mode. I guess nothing bad happened because I was only running a 4Ω load on my receiver, but maybe it would cause a problem if I used two 6Ω speakers in parallel.
It would also be easier to just rate the amplifier to handle 4Ω loads, that way it would be rated to handle 8Ω speakers even in bridge mode. I guess nothing bad happened because I was only running a 4Ω load on my receiver, but maybe it would cause a problem if I used two 6Ω speakers in parallel.
It's not bridged mode.
The amplifier still operates as a stereo amplifier.
The manufacturer is telling the user to use two 12ohms to 16ohms speakers on each left/right channel, if they want to use the A+B option.
if you want a 100W into 4ohms amplifier, then that is what you buy. It will operate into higher impedances. Typically a 100W into 4ohms will give about 60W into 8ohms.
But you can't go the other way. Using a lower than rated load impedance can potentially damage the amplifier.
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