Questions on Surrounds

[DwK]

Alright

In the living room we have my grandfathers Yamaha Natural Sound Stereo Reciever set up.

It puts about.. 100 watts perchannel and has a A and B switch.

As far as I understand, when you have A and B on it sends half the power to A and half the power to B.

So if its 100 watts per channel. It would be 50 watts perchannel with A and B turned on.

correct me if I am wrong.

As for speakers..

We have his Klipsch Heresys hooked up to A.

To B we have my big Fishers my dad gave me.

And to B we also have 2 small fisher surrounds (I bought from friend for cheap)

Now.. will having the Surrounds hooked up there hurt them?

It says on the back DO NOT HOOK UP TO A OR B OUTPUTS

but.. I dont see why not.. especialy when its recieving less than the 60 watts handling power.

? Maby its because its 1 speaker about 3-4 inches big.. reciever HI - Low frequencies... and that may over load it ?

Any one know?

[Mighty Favog]

Pending on how you wired it, paralell or series, your now putting a 16 ohm load on the B channel.

[Mighty Favog]

Pending on ho wyou wired them, parallel or series, your now putting a 16 ohm load on the B channel.

------------------

Tom

KLF-20 Mahogany

Carver C-1

Carver Receiver MXR-150

Yamaha PF-800 Turntable/ Sure V15 Type V Cartridge

Carver TL-3100 CD

Yamaha K-1020 Cassette

dbx 1231 EQ

H.H. Scott 830z Analyzer

Monster Interlink 300 mk II

Original 12ga. Monster Cable

[DwK]

Could you explain all that to me please?

[WMcD]

My brother in law has a Yamaha "Natural Sound" amp. It has Dolby Surround. Is that your situation? You're writing about surround speakers, so it raises the question.

- - - - -

Returning to the "ohms" stuff.

A lot of receivers have A and B switches for speakers. Sometimes called main and remote.

However, it is not a matter that the amp is intelligent and sends half its power to each and will throttle back to make itself happy. This is because the switches just hook up the speakers, in parallel, to the same amplifier output. It can run it self into distruction.

This is like hooking up two appliances to the same outlet through an extension cord. Or even connecting the two appliances into the same wall box.

If you turn on both appliances at the same time, they get the same voltage, and draw current according to their resistance in "ohms". If you connect too many appliances they draw too much current and the fuse blows.

In the case of the amp, the output circuit will either, (1) start distorting, (2) trip out a current limiting circuit, or (3) burn itself out. Some amps can take two speaker in parallel. But three is pushing it.

Resistance is really describing the relation between the voltage delivered to the speaker (V) and the current (I) it will draw.

Resistance (Ohms) = V / I

So if you apply 8 volts to an 8 ohm speaker, the speaker draws 1 ampere of current.

8 = 8/1

Lets take a look at two 8 ohm speakers attached in parallel to the same amplifier (like the two appliances). Again we assume that 8 volts is applied. Each speaker draws 1 ampere, for a total of 2 amperes being demanded from the amp.

What is the effective resistance? We use the same equation, kinda backards.

8 volts/2 amperes = 4 ohms.

You can use the same principle assuming three speakers in parallel. Now there are 3 amperes drawn, total.

8 volts / 3 amperes = 2.66 ohms.

Now you can see how parallel circuits reduce the effective resistance.

In fact, 8 volts is pretty high to deliver to home speakers.

You often see speaker sensitivity tested at 2.83 volts into a presumed 8 ohm speaker. That is pretty realistic and equates to 1 watt.

Lets use the same form of the equation.

8 (ohms) = 2.83 (volts) / I

Doing some algebra

2.83/8.0 = 0.35 = I or current.

We also read that voltage time current equals power in watts.

V x I = power.

Lets plug in the numbers.

2.83 x 0.35 = 1 watt.

That is why the number of 2.83 volts is used.

The above is just to show you a simple way of calculating how parallel resitances can be calculated. The real equation is that

1/Rt = 1/R(a) + 1/R( + 1/R©

But what I've shown above is the same and makes more sense.

- - - -

So, is this a surround system? The surround channels use an additional amplifier.

Regards,

Gil

[DwK]

its a Yamaha Natural Suround Stereo Reciever.. only stereo .. nothing special.......... its like 20 + years old.

[RossVTaylor]

Uhhhh... yeah, what Gil said.

Seriously, though, DWK. It sounds like you're hooking three pairs of speakers to a receiver designed for two (at most, and maybe only one depending on speaker impedance) pairs of speakers. Some receivers and amps are more tolerant of low impedance loads than others. Although what you're doing is not recommended, it might work - the only way to know for sure is to try it out and see if the protection circuit cuts out your speakers. If you have no protection circuit, though, permanent damage could result.

Well, do you feel lucky? Well, do you? (say this in your best Clint Eastwood voice)

Ross

[DwK]

Thanks for the help