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Impedance Advice


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I've just picked up some new speakers for my old Hi-Fi system as the kids managed to destroy the old ones. 

My amp/receiver is an old Yamaha RX-596 that I love.
 

I replaced the old speakers with some Yamaha NS-F150. The impedance of these are rated at 6 Ohm which is not an issue. 

The speakers did come with a Sub (Yamaha YST-SW216) which I was intending to off load to a friend, but now I am thinking about adding it to the speaker B outputs. The impedance of the Sub is rated at 5 ohms. This is where my question comes from. 

Speaker output A on the amp required a minimum of 6 Ohms, which is fine with the new fronts. 
Using Speaker output A + B (can't see why I would run the sub on its own) requires a minimum of 12 Ohms. 

If I understand correctly, the impedance won't match that of the amp if I set the fronts to A and the Sub to B.

 

Ive attached a pic of the back of my amp.

 

post-147481-0-62629700-1406352244_thumb.

Would I be better to run everything from output A, that is the sub connected to the Amp, and the speakers connected to the sub? Or am I missing something obvious?

Any advice would be great.

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You have plate amps in the sub already with line inputs (rca), so you need change to a reciever that has rca sub line outputs. It's the only way if you want to use your sub.

As if you run the subs off you speaker terminals with the others on this reciever than you have the total load presented to the amp will be 2.7ohms and your amp will probably not like this, you could put resistors in line with the sub to raise the load but it will sound like crap. 

 

Cheers George

Edited by georgehifi
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I don't think it will matter about the impedance as your Sub is only using the speaker connectors for a signal and then it has its own amp for the sub.

So it should not be putting any load on your Yamaha amp.

Just connect it up like you say and see how it goes. Should work well. :)

 

Use Input 1 on the sub as this is used for exactly the way you want to use it. These are high level inputs unlike the RCA connectors (Input 2) which are low level and need a sub out on your Amp.

Edited by rocky500
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Thats whats thrown me George. The fact that the specifications of the sub say;

 

Output Power: 50W (100 Hz, 5 Ohms 10%T.H.D)
Dynamic Power 100W, 5 Ohms.

The manual for the sub though does explain setting up the sub in a hifi system using the standard speaker outputs. Whats not mentioned in the manual for either the amp or the sub, is the issue of matching impedance. 

Now I am writing this down, I have noticed that the Input Impedance for the sub is 12 Ohms, which possibly makes it all fine? 

I guess what makes me nervous is I know what an issue matching impedance is with tube guitar amps. I really don't want to be blowing anything up unnecessarily. 

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I thought the impedance was irrelevant for subs with their own amp. It will not be not using the Yamaha Amp for power. It has its own amp built in.

 

Did a quick google and this seems to be the general info I found

 

"Some subs do have a high level input so they can be used with stereo amps without phono sub outputs but these have very high impedances so do not affect the impedance the amp sees."

Edited by rocky500
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Just so we are all talking about the same thing, this is the way I was hoping to hook it up.

 

attachicon.gifScreen Shot 2014-07-26 at 7.24.32 pm.png

George, do you think the RCA impedance would be different to using the speaker inputs?

 

It is, but it is not important. You should connect it in the fashion suggested by Yamaha. 

 

IE: From amp to sub, then from sub to speakers. 

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Thanks for all the advice. 

Yamaha's manual for the sub says to set it up either way. As it turns out, I miss read the specifications, the input impedance is actually 12 K Ohms, so it should be no issue to the amp.

That said, I'll take the advice here and hook it up the way suggested. 

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