I know this isn't rocket surgery...

[slmcdonald7]

Hello all,

Reading B Panther's post about balanced subwoofer xlr connections got me thinking (which is never good) about something I have always wanted to know about the operation of my subwoofer. Since I have no idea what xlr connections (I don't even know if I got the name right) are, if that thread answers my question, then just let me know.

My question is:

I bought the sub when I was putting together my first 'real' sound system a couple of years back (early college). It is a little 8" Polk 250, I think I got it free (or at a discount, I don't remember which) for buying some crap at Circuit City (I am ashamed to admit it, but it was a pair of Bose speakers . Try to forgive me, I was young and ignorant). Well, anyways, on the back of the sub, there are two line inputs, L and R. I simply hooked a cable from my receivers subwoofer preout to the "L" input on the sub and when it played, I didn't think much more about it.

But I have always wondered, if there is only one subwoofer output on my receiver (it has been this way with both my Kenwood and Denon receivers, so I assume that this is the norm ), why are there two inputs on the back of my sub? Is there a difference between the two inputs? Should I be doing something different with my wire (split it or some such thing)? Do I just have a crappy sub?

As always, any and all input is appreciated,
Stephen

 

[markw]

They can sell more subs with two inputs.

Subs with only one LFE input would be great for HT units with only one LFE output. In fact, to use a sub with a HT receiver you don't really need too many controls at all. HT receivers control the signal sent to the sub so most controls on the sub are redundant.

Stereo systems don't generally have a LFE output buy many DO have L/R preamp outputs.

To run a sub with a stereo system with L/R outputs, you need both those inputs on the sub. You just can't put a "Y" connector on a preamp's output to combine them.

Likewise, that's why many powered subs come with so many other controls such as crossover freq, level controls and the like. Most HT receivers control this with some menu somewhere but to mate a sub with a stereo takes a little balancing act, which these controls allow.

So, they can sell to both markets now.

 

[Unregistered]

There are two inputs on the sub so you can send it a stereo signal. The sub will then sum to mono and apply its crossover. That's probably only useful for connecting the pre-outs of a stereo receiver to the sub (you'd then run the speaker wires from the sub to the two speakers.).

For HT, its a bit different. With bass management, the receiver takes care of combining the bass information from all speakers (according to how you've specified the speakers as 'small' or 'large') and then sends a mono signal to the sub. You can use a Y-connector to connect both inputs if you choose - it will result in a +6dB bass boost - but it is not necessary to do so and many advise against it.

Most subs say to use only one input and that input is nearly always the L input. JBL subs I've had have a switch that can be set to 'normal' or 'LFE'. The switch is independent of whether you use one input or two. If the switch is set to 'normal' then the sub's crossover is active and you should set the crossover as high as it will go if you are using the bass management of the receiver. If set to 'LFE' the sub's crossover is disabled and the position of the crossover dial is irrelevant.

For HT, the correct setting is to use the L input only, set the switch to 'LFE', and set your receiver's bass management properly.

 

[cam]

Rocket science and brain surgery not rocket surgery.

 

[Unregistered]

Rocket science and brain surgery not rocket surgery.

Yes, a bit of a mixed metaphor but we knew what he meant.