A and B Channels on Receiver

[gcmarshall]

If I run both A and B at the same time, what impact does that have on my receivers output ability? In other words, for lack of a better way to ask this, does running A and B at the same time knock down my receiver's 130 watt/channel rating to 65 watts/channel for A and B? Also, does that cause my receiver to be driving a 4 ohm load instead of the 8 ohm load my speakers are rated at?

The reason I ask is I am considering trying out a bi-wire setup with my RX-V 2500, just to experiment. The manual says to use the A and B jacks to run the bi-wiring to my from speakers. My speakers are 8 ohm rated. By bi-wiring, am i reducing the output to my front speakers since I will have to activate both A and B channels and will my receiver "see" a 4 ohm load?

Thanks.

 

[MDS]

A+B on the vast majority of receivers puts the two sets of speakers in parallel so running two sets of 8 ohm speakers will present a 4 ohm load to the receiver. I can't say that that is true for ALL receivers, but it is true for every receiver I've ever owned, used, or read about.

 

[Seeker]

Good question. I'm running A+B full time for the most part.

I have 6ohm TimeFrame Speakers on A and a pair of older Hitachi speakers on B that are 8ohm. Hope that the mismatch won't harm the Yamaha 80watt per ch. amp. There's a switch for differnt ohm rated speakers on the back, but it doesnt make much sense.. I assume "at least 6ohms" means I can do what I'm doing.

It took me awhile to figure out why when I had only one pair of speakers on "A" on another amp and then hit the "B" button (without speakers on "B") that the A speakers would go silent. Now I understand that you have to have B hooked up too because they finish the circuit... otherwise I was just opeing up the circuit with no speaker hooked up. If that makes anysense....

 

[markw]

What you describe is the A and B speakers being connected oin series, not parallel.

Good question. I'm running A+B full time for the most part.

I have 6ohm TimeFrame Speakers on A and a pair of older Hitachi speakers on B that are 8ohm. Hope that the mismatch won't harm the Yamaha 80watt per ch. amp. There's a switch for differnt ohm rated speakers on the back, but it doesnt make much sense.. I assume "at least 6ohms" means I can do what I'm doing.

It took me awhile to figure out why when I had only one pair of speakers on "A" on another amp and then hit the "B" button (without speakers on "B") that the A speakers would go silent. Now I understand that you have to have B hooked up too because they finish the circuit... otherwise I was just opeing up the circuit with no speaker hooked up. If that makes anysense....

If they were run in parallel, either A or B would work wether or not the otherset was connected or not. When they BOTH need to be hooked up to get the B speaker to work, they are in series. The power is divided between the two sets.

 

[gcmarshall]

clarification

i think i asked my question poorly. here is a clarification. i was considering bi-wiring my front speakers out of my Yamaha 2500 (although i realize there will be minimal, if any, improvement - it's just for experimentation). the manual says to run one pair of speaker wire from the "A" left/right jacks to one pair of binding posts on the speaker. then, it says to run the second pair of speaker wire from the "B" left/right jacks to the other pair of binding posts on the same speaker. them, you have to have both channel (A and B) turned on.

what impact does this have on the receiver by running both A and B at the same time? does it cause the overall output of the receiver to be cut in half? Does it cause the receiver to "see" a 4 ohm load, where it would otherwsie see an 8 ohm load since my speakers are 8 ohm impedence?

Thanks for the help, as always.

 

[mulester7]

i think i asked my question poorly. here is a clarification. i was considering bi-wiring my front speakers out of my Yamaha 2500 (although i realize there will be minimal, if any, improvement - it's just for experimentation). the manual says to run one pair of speaker wire from the "A" left/right jacks to one pair of binding posts on the speaker. then, it says to run the second pair of speaker wire from the "B" left/right jacks to the other pair of binding posts on the same speaker. them, you have to have both channel (A and B) turned on.

what impact does this have on the receiver by running both A and B at the same time? does it cause the overall output of the receiver to be cut in half? Does it cause the receiver to "see" a 4 ohm load, where it would otherwsie see an 8 ohm load since my speakers are 8 ohm impedence?

Thanks for the help, as always.

.....GCMarshall, I'm going to get back on this one tomorrow....I just got in from bringing a loaded coal train back from Van Buren/Fort Smith, and I'm tuckered....I'll say this now though, if you want to hear your bi-ampable/bi-wireable 8 ohm speakers turned into full-range 4 ohm speakers, bi-wire them at the posts of the speakers with a small short piece of speaker-wire between the two +, and the two - posts, and just run one long run of speaker-wire from the receiver off of A L&R....saves wire, same effect, by paralleling at the speaker and not the amp section....you're taking two 8 ohm sections of the speaker and paralleling them with either hook-up, save wire....nightol.....

 

[jcPanny]

Biwiring with A+B

The speaker A and B terminals on your receiver share an amplifier. Connecting one set of speaker wires to the A terminals and another to the B (on A+B) is the same is connecting two sets of wires to the A terminals.

This will have no effect on the impedence of the speaker and likely no performance improvement either. Effectively you are doubling the gauge of the speaker wire. If you are already running 12 or 14 AWG then there is no point.

 

[t3031999]

This will have no effect on the impedence of the speaker and likely no performance improvement either.

I agree that there will likely be no performance improvement, but it will effect the impedence. If you are bi-amping 8 ohm speakers (removing the jumper) but connecting to the same binding post, you are running 2 8ohm speakers in parallel which presents a 4 ohm load to the receiver.

 

[j_garcia]

I agree that there will likely be no performance improvement, but it will effect the impedence. If you are bi-amping 8 ohm speakers (removing the jumper) but connecting to the same binding post, you are running 2 8ohm speakers in parallel which presents a 4 ohm load to the receiver.

The receiver will still see exactly the same total impedance as if the speaker were used with the jumper in place. Total impedance of that speaker does not change with the jumper removed, because each set of drivers presents only a portion of the total load that yeilds the nominal impedance of the speaker with the jumper in place.

I've tried the A&B biwiring, don't bother.

 

[t3031999]

My bad, I was thinking that both the mids/tweeters and woofers each had an 8 ohm impedence, then the jumper would make them 4 ohm.
My thinking was flawed.

so that would mean that each pair of binding posts is a 16 ohm load?

 

[j_garcia]

My bad, I was thinking that both the mids/tweeters and woofers each had an 8 ohm impedence, then the jumper would make them 4 ohm.
My thinking was flawed.

so that would mean that each pair of binding posts is a 16 ohm load?

No, they probably aren't each 16 Ohms each, the top and bottom may actually be different (ex: top end is higher and bottom end lower) and the total of the two combined is 8 nominal. However, we've seen with one member here who measured a Polk RTi tower and the measured impedance was lower than the claimed nominal impedance of 8 Ohms with the jumper in place. In either case though, the total load that the receiver powers is the same in the case of parallel A&B or biwiring off a single terminal. With bi-amping, the same load is presented, but each is handled by a completely separate channel.

 

[mulester7]

The speaker A and B terminals on your receiver share an amplifier. Connecting one set of speaker wires to the A terminals and another to the B (on A+B) is the same is connecting two sets of wires to the A terminals

.....and doing that, JCPanny, at either end, you're paralleling speaker elements....two 8 ohm's paralleled, produce a circuit of 4 ohms, period....takes more to drive them?....not as much as you'd think....but, if you're serious about the sound quality of which they are capable, you go to slave-power medium/big-rms-continuous....clean power, sure....and those who give no credence past 50 as a damping factor, you need to have been with me hearing the fruit of the two amps I had going against me, with me in the middle that day, pushing "same line" speakers......