A+B in same terminal


New member
Username: Stephen

Amherst, Nova scotia Canada

Post Number: 1
Registered: May-04
Hey everyone,
Would it be OK to put A+B speaker wires into the same terminal on one speaker. my yamaha amp boasts that when both A and B speakers are on -you get twice as much wattage, so if I put A+B left speaker wires in the same terminals of my left speaker would it fry the amp or give the speaker twice as much power. The only reason I'm thinking this is because I believe my Cerwin vegas are being under powered with my present set up.
P.S. I don't want to purchase a new amp.

Jan Vigne
Unregistered guest
What do you mean by "under powered"? Be specific. What do you want that you presently do not have? The situation you have asked about will gain you nothing but the cost of extra speaker wire.

New member
Username: Stephen

Amherst, Nova scotia Canada

Post Number: 2
Registered: May-04
A channel = 85 watts
B channel = 85 watts
total =170 watts

capability =200 watts
A channel alone - 85 watts un-utilized power 115 watts
A+B would take you to 30 watts of capacity

J. Vigne
Unregistered guest
Sorry, Stephen, it doesn't work that way. Not unless Yamaha has created an amplifier unlike anything ever placed on the market before. Their information sheet that gives the impression that the amplifier has two power amp sections for each speaker selection may be somewhat misleading, that would not be a first for the industry. But no one has put two power amps in one reciever which is what your statement really implies. There is one amplifier which will produce 85 watts of power, period. How you decide to distribute that 85 watts is up to you. I would suggest you read my response to "I need professional help" as to how power distribution works out. The answer is a bit more complicated than your situation but I think you can learn from the examples of distibuting power and the impedance changes as more speakers are added to the load of the amplifier.

In your case the 85 watts can go to either A or B speakers but not both at the same time. If the amplifier is stable enough to run less than an 8 Ohm load (many are not) you will half your available power to each speaker as you add each successive pair. Which means the 85 watts to one pair will become 42.5 watts to two pair. Now, how the amplifier handles the aditional pair of speakers will be determined by essentially three factors: how the additional speakers are wired into the system(in parallel or in series), what the impedance swing of the combined speakers amounts to and the stability of the amplifier to respond to this new load.

First, when you wire additional speakers into a system you must decide how you will make the connections. Series runs from the + on the amp to the + on the first speaker then from the - on that speaker to the + on the next speaker and finally from the - on the second speaker to the - on the amp. If you wire in series you will double the impedance (8 + 8 = 16 in this case). Parallel is simply both speakers connected + to + and - to -. If you run the speakers in parallel, which is how 98% of the recievers and power amplifiers have done A/B switching, you will cut the impedance in half (8 + 8 = 4 in this case). This assumes the speakers are always at 8 Ohms, which they are not. Speakers, unlike the power resistor that is used to test and determine power output for specifications, do not stay at a single impedance. They wander around based on several factors and can be substantially higher and, most importantly substantially lower. To a certain extent most amplifiers are not bothered by a slight increase in impedance but many freak when they are presented with a lower impedance than say 8 Ohms (which has become, for some stupid reason, the industry standard to build for and measure at). This topic has been covered in this area of the forum before, please do some further reading to understand this. Suffice it to say what you see in a speaker's test measurement is the speaker's impedance curve which can be a very significant piece of information. As you combine speakers you will want to know the cumulative load you will show the amplifier. So, in short, there are no "8 Ohm" speakers, that idea is just too simple.

Now the biger topic is how does your amplifier respond to the issue of impedance. This topic has also been covered in the replies in this section so, again, you should do some reading. The way an ideal amplifier works is to double its power output as the impedance is halved 85 watts at 8 Ohms will become 170 watts at 4 Ohms. (This is probably what Yamaha was implying in their statement of how your amplifier operates.) This continues as the impedance drops. As the impedance (remember we are talking a theorectical here not a realistic) rises the amp will produce less power. 85 @ 8 Ohms = 42.5 @ 16 Ohms. This is true for an ideal amplifier under ideal conditions. It does not happen for many reasons. First, it seldom happens with tube amplifiers because most tube amps use output transformers which keep the impedance more or less constant to the output devices. Second, it is expensive to build an amplifier that approaches theorectical perfections. Most (not all) recievers are designed to operate to specification at 8 Ohms, anywhere else in the impedance swing they are unhappy (read about power supplies in amplifiers). So as the impedance rises or falls they will not react in the ideal fashion. In fact, most will go into protection and simply shut down. The major reason this is the norm today is cost of building a really good amplifier (also cover in the forum) and the reliance upon specs to sell a piece of equipment (also covered in this section). Your Yamaha is not known, as were the original Yamaha designs of the late 70's, as an amplifier that will drive difficult loads. Finally the connection you will be making by combining the two speaker outputs still shows the amplifier one pair of speakers so you are not changing the impedance in any way. (Ok, OK! You're lowering the impedance of the speaker wire by changing its overall guage but, come on, that ain't gonna change the real equation we're discussing here.)

Let me also say that speaker capacity, or power handling or whatever you wish to call it, is one of the most ridiculous numbers ever created by a marketing person. It is totally meaningless. Unlike a basketball that won't bounce if you do not fill it close to capacity a speaker will play no matter how much or how little power you put into it. If you take a speaker and put in 1/4 watt you will get sound. How loud the speaker will play is determined by its efficiency. A speaker rated at 83 dB @ 1 watt @ 1 meter ( a small minimonitor) will not play very loudly while a speaker rated at 104 dB @ 1 watt @ 1 meter ( Klipschorn) will fill a room. If you take a 40 Hz signal it will require tens of times the power to drive a woofer than a 15,000 Hz signal that goes to a tweeter. Therefore, if you drove a tweeter with the same amount of power that was being sent to the woofer you would no longer have a tweeter. Duration of the signal also is a determining factor in power handling. A short burst of power (depending upon its type of initial power requirement) is not too hard to handle but play the same frequency for twenty mintues and you may come back to find your speakers are now sushi. And this opens the discussion to amplifier clipping which is way beyond the scope of this answer. Now that said, the next comment is the ever popular "speakers don't got no watts". Only amplifiers have watts so the idea that there is "un-utilized" wattage in your speakers is absolutely incorrect. The more appropriate idea is that your speakers can handle a certain amount of wattage (that will vary depending on frequency and duration) and you want to stay well under that limit. Kinda like your speedometer says the car will reach 150 mph, you don't want to run at more than 20 mph in a school zone for safety reasons. An 85 watt amplifier with a speaker that "can handle" (how stupid that comment is) 200 watts is pefectly acceptable and better than the other way around.

Bottom line here, what you have asked in your first querry is acceptable to do. You can place both A and B speaker outputs to one speaker but you will still end up with 85 watts of power in your amplifier (hopefully).

You are using Cerwin-Vega speakers which are reasonably efficient speakers. That means they produce a good amount of volume from the amount of wattage you put into them. If you are not getting the volume level you want you should find an even more efficient speaker. If you are not getting the amount of bass you desire you should look into a different position for your speakers. Move them into the corner on the floor to se what you think of the sound. If the overall quality of the sound is not what you want you should start saving up, this could get costly.

Does that help?
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