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Yamaha A-S700 oddity! (BiAmp)

3404 Views 2 Replies 2 Participants Last post by  LDBennett
I just got a Yamaha A-S700 integrated Amplifier. I have yet to hook it up (waiting for my speakers to arrive). In reading the Yamaha instructions I found a "BI" hookup for the speaker listed in the instructions. This was the first I had heard of this. It is where you separate the speaker's tweeter/midrange from the woofer and drive each with its own amplifier. The instructions tell you how to do it. You remove the shunting bar on the speaker and run separate wires to each part of speaker for a side (left or right). So Speaker "A" out drives the tweeter/midrange and Speaker "B" out drives the woofer. Sounds good!

But there's a rub. I found the schematic on the internet as part of the Service Manual and there are two Amplifiers, left and right. The Speaker A and B are connected to a switch from the amp for a side which make the BI connection meaningless. The removed speaker shorting bar is replaced inside the amp! The A and B speaker terminals are for local and remote speaker control: A on, B on, both A and B on, or both off. There can be no improvement in performance from a BI connection to the speakers on this amp.

I think it a little disingenuous for Yamaha to try to fool users into thinking they are doing something special when they hook up the speakers BI when it only allows the tweet/ midrange and the woofer to be turned off and on separately. That's not even a usable idea.

Did I miss something?

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Further reading revealed Bi-Wiring and Bi-Amplifier. Yamaha's A-S700 instructions are for Bi-Wiring which does nothing. Bi-Amplifier is not all that effective unless you do the crossover before the amplifier instead of at the speakers. Now that does something as it limits the frequencies in each amplifier, reducing harmonic distortion and keeping heavy base out of the tweeter/mid-range channel. That can help!

But for Yamaha to promote a meaningless Bi-Wiring scheme is wrong when they obviously know it does nothing for sound quality. That was my point.

In a slightly different vein is the use of expensive speaker wiring of hugh gage wiring. Unless your speaker wire runs are long, it is a waste of money, in my opinion. If my amp is putting out 120 watts (which would be impossible to stand near in any normal sized home) the actual current in the wire would be about 2 amps. Any 16 gage wire (like you get in good zip cord) can easily handle that with minimal line loss.

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