Subwoofer set up

I have a REL B3 and you start by setting the rolloff at the low end of the speaker spec. Key word here is start

Even my bookshelves claim to produce lower freqs

Claim is a key word here

Wouldn't it be better to feed the speaker output to a separate Xover and then control the output to both the speakers and the sub. That way the speakers wouldn't get bass they can't handle well.

You can use a digital processor, as in a AVR, to separate the frequencies, or connect the speaker outputs to the subwoofer and the main speakers to the subwoofer, using the crossover in the subwoofer to divide the frequencies. Your manual should provide this information. Very few and very expensive floorstanding speakers can produce the low frequencies that good subwoofers can. Integrating the sub and monitors/floorstanding speakers is difficult without a proper crossover.

How is this? The preamp goes out to the sub with a Xover, then the speakers out of the sub to the main amp while the sub amplifies the low freqs.

The sub receives the output from the amplifier at the high level speaker inputs, and then the speaker outputs go out to the speakers, assuming you have the connections. Which sub is it?

Most people will dial the sub in where the speakers begin to naturally roll off. This can be done by ear.

-Rob

Neilmc,

If you have a subwoofer jack as your original post suggests, presumably your receiver or pre-pro has one or more crossover settings, e.g. it sends frequencies above 80 Hz to your main speakers and below 80 Hz to your sub. This is true even if you use separate amps, as I do. Typically, you specify this in the setup menu, often by classifying your main speakers as large or small. If using a sub, you want to select small, even though your main speakers are floor standers.

It's really quite simple; you are unlikely to need an external crossover filter to complicate things. I do recommend a sound pressure level meter, set to C weighting and slow trajectory. Radio Shack sells one very adequate for the application.

db

db

Before messing with a sub, I would suggest taking some rta measurements of the room, to see exactly where your speakers roll off in your room. Then, you can decide how to best go about integrating a sub, and objectively what you want to accomplish with it.