Confused about Subwoofer plug on my receiver and subwoofer


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deck

I just got a new receiver (Denon AVR-789) to replace my one (Yamaha HTR-5750). It was time.

When I first setup my Yamaha I was fairly ignorant as to how receivers were to be setup and configured. I'm trying to become more adept with this new one, but something confuses me;

Both the Yamaha and now the Denon have a single RCA plug labeled 'Subwoofer.'

My subwoofer, which is a powered Polk Audio, has two RCA plugs for stereo in (Left/Right) and left/right plugs for speaker wire. No single subwoofer plug. In the past I've had bass by running the B speaker output from my receiver to the speaker inputs on the subwoofer, but I want to do better. Also, the auto setup on the Denon does not detect a subwoofer and is not calibrating things properly.

So the question is; what am I doing wrong? Do I need a Y cable to plug the subwoofer out on my receiver to the L/R line in on my subwoofer? Do I keep the speaker wire from the B output on my receiver plugged into the speaker inputs on the subwoofer?

I've looked around that box... there aren't any other inputs.

Thanks!

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kiwi89

Do you have the manual for the sub? That should have some info on setting the thing up.

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deck

Yeah... I'm a dummy who loves Neowin.

I hunted down the manual online and found that this receiver does not have an LFE port, but a Y plug will work just fine.

Any comments otherwise?

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Starbuck84

You're not doing anything wrong, some subwoofers use the Left analog input as the LFE input. In other words, just connect your amp's (receiver) subwoofer output to the Left input of your subwoofer and you're ok.

/Edit: The reason for the Left and Right input on your sub is because older receivers just outputted both signals to the subwoofer which in his case would filter out the low sounds (bass). Newer amps or receivers utilize a LFE (or sometimes refered to as plain 'subwoofer') output in which case the amp filters everything and only provides the low sounds (bass) to your subwoofer. Again, just connect the subwoofer out of your amp to the Left on your subwoofer and you should be ok.

/Edit2: Y-cables are unnecessary as a sub in itself is Mono. So when you use a Y-cable, you split a mono signal to 2x mono, and your subwoofer combines these to 1x mono again...

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deck

Ok... I've carefully read the manual.

It mentions that I can use 1 RCA plug into the left or right Line In, but goes on to say that a Ycable will also work.

I'm not understanding the difference and why a subwoofer, which should only deal with one channel, have stereo inputs.

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+spikey_richie

Perhaps to do with correct speaker oscilation?

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x3lumin8x

Is the sub dual voice coil? If it is, than you need a splitter at the sub end. Right is for one voice coil, Left is for the other.

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+spikey_richie

Also is the sub active or passive?

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x3lumin8x
Also is the sub active or passive?

He said it's a power sub. It also has speaker level inputs. If I'm not mistaken, you can bypass the amp on the sub with a separate amp if hooked up through speaker level.

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+spikey_richie
He said it's a power sub. It also has speaker level inputs. If I'm not mistaken, you can bypass the amp on the sub with a separate amp if hooked up through speaker level.

My bad - i'm not an audiophile :)

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shakey_snake

Your sub wishes to crossover the signal itself, but your receiver has already done it for you.

It's not really a problem to do so twice, I'd just set your sub's low-pass frequency to the highest possible value.

I'm not understanding the difference and why a subwoofer, which should only deal with one channel, have stereo inputs.
So that it can crossover both channels of a stereo. Edited by shakey_snake
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njeske

I can't speak much about Polk Audio subs, but my JBL powered sub has stereo RCA inputs as well. Either one will accept an input from the LFE output on my reciever. I just chose the left channel and it works fine.

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shakey_snake

^:ermm: well... of course.

There's nothing really special about a LFE channel once it is analog, it's just another line level signal.

It just happens to only contain low frequencies, as it's been low-passed before being stored on media like a DVD.

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