A+b?

[Cygnus]

Allright, I phoned the place where I got my receiver, regarding the A/B, A+B speaker setup on the Denon AVR-1705 that I have...the conversation went pretty much like this:
C = Cyggie
G = Guy that I talked to.

C: Allright, on the back of my receiver, it says for 'A+B', you need 12 to 16 ohm speakers. Is this true?

G: No, normal 6 to 8 ohm speakers will work fine, what that chart is saying is that if you have one set of speakers on the 'A' terminals and another set of speakers on the 'B' termianls, the ohms multiply.

C: Oh, isn't it the other way? That if you have four speakers hooked up, it makes the ohms less? Or does that apply only if you have four speakers hooked up to one terminal? [Meaning four speakers hooked up to 'A', as opposed to one set of speakers hooked up to 'A' and another set to 'B'.]

G: No, you should be fine using normal 6 to 8 ohm speakers hooked up to the 'A' and 'B' terminals, [just dont hook all four speakers up to one terminal!]

----------------------
Is this correct?

Thanks,
trav

 

[mtrycrafts]

Allright, I phoned the place where I got my receiver, regarding the A/B, A+B speaker setup on the Denon AVR-1705 that I have...the conversation went pretty much like this:
C = Cyggie
G = Guy that I talked to.

C: Allright, on the back of my receiver, it says for 'A+B', you need 12 to 16 ohm speakers. Is this true?

G: No, normal 6 to 8 ohm speakers will work fine, what that chart is saying is that if you have one set of speakers on the 'A' terminals and another set of speakers on the 'B' termianls, the ohms multiply.

C: Oh, isn't it the other way? That if you have four speakers hooked up, it makes the ohms less? Or does that apply only if you have four speakers hooked up to one terminal? [Meaning four speakers hooked up to 'A', as opposed to one set of speakers hooked up to 'A' and another set to 'B'.]

G: No, you should be fine using normal 6 to 8 ohm speakers hooked up to the 'A' and 'B' terminals, [just dont hook all four speakers up to one terminal!]

----------------------
Is this correct?

Thanks,
trav

Nope. Your impression is correct, his is incorrect. In thisa case, the info on the back is telling you that A+B are in a parallel connection that is why you need such high impedance speakers so when they are parallel, the impedance is between 6-8 ohms, most likely what the amp is rated for

 

[Cygnus]

Actually, my impression was that he was correct. Aww...this sucks..

 

[PENG]

I thought I explained that to you before, but it might have been someone else. I concur with mtrycrafts. When you select A+B, the A & B terminals are internally connected in parallel. That's why if you connect one pair of 8 ohms speakers to terminal A and another pair to terminal B the receiver will see 4 ohms and you will have to be careful not to crank the volume too high. In this case you will be relying on the receiver's protection circuit to protect the amps from overloading. If you really need to use A+B, get some 16 ohm speakers, it will be tough to find them.

If you still don't believe us, phone or email Denon, but make sure they understand your question.

 

[mtrycrafts]

Actually, my impression was that he was correct. Aww...this sucks..

Yes, email Denon and ask if A+B is a series or parallel connection of speakers?

 

[Aliixer]

Hmmmmmm?

Can the yamaha RXZ9 do this, run A+B. Without having to worry.

 

[Buckeyefan 1]

Can the yamaha RXZ9 do this, run A+B. Without having to worry.

Yes, it can. Think of it logically. When you run 5, 7, or a+b drivers with your new system, you are taxing the power supply that much more than simply driving 2 channels or basic surround sound. Running 2 channels with "a", and 2 channels with "b" is still taxing your power supply. Whether you are pulling 4 ohms or 16 ohms, the more drivers you push, the more heat will be generated by the power supply. You need to ventilate your unit well, and check the temperature when driving difficult loads. If the unit is extremely hot, shut it off and let it cool down. If it's not, then you are not pushing it and all is well. Your receiver would not have the option of a+b if it could not handle the load, but the receiver cannot judge the length of time, nor the volume you choose to play your material.

 

[kay]

I agree that the guy at the shop is incorrect. Technically, you should have two pairs of 16 ohm speakers in order for the amplifier to see 8 ohm load when you use A+B.

However, I also agree fully with Buckeyefan in that as long as you're not pushing the volume too high and keeping a close watch on the temperatures, all should be well. Dont *EVER* use A+B while you're having a party however. Chances are someone will crank the volume and you won't be keeping an eye on the receiver.

 

[Buckeyefan 1]

Here's another angle on this topic. Let's look at it from a practical standpoint. 98% of home stereo speakers on the market are 8 ohms. Receiver manufacturers know this which is why they design the amps for that load, but can probably run a 4 ohm load as long as you keep an eye on the temp. Cygnus' receiver showed "12 - 16 ohms for a+b". Another responded saying that's parallel so the 12-16 ohms with 2 speakers would come out 6-8 ohms. Not sure about you, but don't recall seeing too many 12 or 16 ohm speakers. Even car speakers don't come that way. Do you think a receiver manufacturer like Denon would design a product that uses an impedance that isn't available, or that is so rare? No. If you listened to two speakers on "a", and had another set on "b", as soon as you hit "b", the system would not get 2x as loud. Instead, the impedance would double and each set would be half as loud. Running two sets is meant to fill a room or multiple rooms, not double the sound. a+b are wired in series internally, so that when you buy a common everyday off the shelf 8 ohm speaker, in series you are getting 16 ohms.

You could accomplish the same thing by wiring each pair of 8 ohm speakers in series, then wiring the two pairs together in parallel and putting them on "a" and not even using "b". In other words 8+8=16 (series) and 8+8=16 (series) and 16/2=8 (parallel).

Confused?

 

[PENG]

Sorry Buckeye you are most likely off on this one, A+B is parallel, not series. However, we are saying the same thing about Denon can do 4 ohms, as long as you don't crank it too high. Denon clarified this point in the FAQ section. Well, I am done on this one. Would be nice if someone like Gene would say something about it, or else someone could email Denon.

Hey Buckeyefan1, how about this, to prove that A+B does not put the A&B speakers in series, simply select A+B without connecting the B speakers. If it is connected internally in series you will not get any sound because the circuit will not be complete. If you still get sound from the A speakers, then it must be in parallel. Right, Buckeyefan1?

I have several units from way back that have the A+B selection, and I know they are parallel. Unfortunately my 3805 does not offer that option so I cannot do this experiment, but still, I have no doubt I am right.

 

[Buckeyefan 1]

Sorry Buckeye you are most likely off on this one, A+B is parallel, not series. However, we are saying the same thing about Denon can do 4 ohms, as long as you don't crank it too high. Denon clarified this point in the FAQ section. Well, I am done on this one. Would be nice if someone like Gene would say something about it, or else someone could email Denon.

Hey Buckeyefan1, how about this, to prove that A+B does not put the A&B speakers in series, simply select A+B without connecting the B speakers. If it is connected internally in series you will not get any sound because the circuit will not be complete. If you still get sound from the A speakers, then it must be in parallel. Right, Buckeyefan1?

I have several units from way back that have the A+B selection, and I know they are parallel. Unfortunately my 3805 does not offer that option so I cannot do this experiment, but still, I have no doubt I am right.

Peng,

I have a Yamaha RX-330 2 channel receiver with A and B options. I just tried it and you are absolutely correct. Thanks for the correction. Great analogy, by the way. Apologize for the misdirection people.

 

[PENG]

Buckeyefan1, I never felt you misdirected anyone because clearly your comments were based on logically thinking. It just happened this A+B thing does not seem to follow logic. I have to agree with you about why manufacturers bother providing this option when they know full well most speakers are either 4 or 8 ohms. I thought during the tube amp days, 16 ohms speakers were more readily available, but nowadays they are hard to come by. You are always open minded for debates and I respect your contribution.

By the way, it is possible (though rarely, and certainly not Denon) that you are right in the sense that some receivers may in fact put A&B in series. In that case I don't know what the gain is, the sound quality will likely deteriorate and you won't get any more volume out of it. The current going into each speakers in that case would be halved.