How many watts make it to the subwoofer?

[Amon37]

I'm having a hard time trying to find out how much power gets sent to the subwoofer. If I have a 7x100W system and I have 7 speakers plus a subwoofer into the sub pre-out how many watts are going to the subwoofer? manuals don't say.

[DavePS3]

Technically, none. It's a passive signal. The amp in the sub cranks the signal out. If you have a passive (non-amplified) sub, plugging it in to the "Sub Out" on the receiver won't give you jack.

[Amon37]

So then your saying I will get whatever the subwoofer watt rating is. If I only have 7x100 system but I have lets say a 150W sub, plugging it into the pre-out will net me the 150W because the sub is doing the work?

[DavePS3]

Yup.

[DavePS3]

If you had a passive sub, you'd hook it up differently so that the receiver was actually sending it a powered signal. In that instance, the receiver's wattage would drive the passive sub but you'd still be restricted by the actual rating of the passive sub. Like any speaker, you'd only be able to push so much through it before the driver started to fart. That's also true of a powered sub because a driver is a driver and can only take so much. Usually, it's distortion that hurts speakers and subs. If you have a clean signal, a speaker can usually take more amplification than a dirty one. That's where the classification of amplifiers comes into play... class A, B etc...

[Amon37]

Thanks for all the info.

[DavePS3]

Also... by taking an RCA cable from the Pre-out to the sub, you'll generally get more mid-range bass through the sub but running that cable from the Sub-Out will give you lower and better (cleaner) LFE (low frequency effects). For example... in Vertical Limit, where the girl is hanging onto the ledge and the guy above her is about to lower a rope to her, her eyes suddenly widen. With the RCA connected to pre-out, you don't hear a rumble for a few seconds. With the RCA connected to the sub-out, you hear the distant rumble the second she hears it.