Is there such a thing? I want to use it with powered speakers...preferably good quality (obviously), not too expensive (below US$3000?), and modest in size...or do I have to use a pre-pro for home theatre use?
There are several ways to add a subwoofer to a two-channel system.
1. Send a full-range signal to the sub and use the sub's internal high-cut controls to set the roll-over characteristic. send a full-range signal to your mains as well. This requires a pre with two main-outs per channel or using a signal splitter to get two feeds from each channel. I like to let the main speaker's low frequencies roll off naturally and add the subwoofer so it augments this natural roll-off rather than employ a bass-cut on the mains.
2. Send a full-range left-right signal to the sub and use the sub's cross-over to send the signal to your main speakers. Most subwoofers have connections for this sort of set-up. I find that this can degrade the mains signal but depending on the sub the effects can be very slight.
My own preference is for TWO subs; one for each channel rather than one mono sub getting both right and left feeds. Two smaller subwoofers can be placed in a room more conveniently for better response in terms of room interactions and more believable transient attack.
At our price point - less than $3K - you have many options so your budget shouldn't be a limiting factor.
Contributor to The Absolute Sound, EnjoytheMusic.com, Vintage Guitar Magazine, and other fine publications
Thanks Steve. I figured things out now. I using your 2...its for a desk top system. Mac Itunes into a benchmark USB DAC to (gulp!) a DartZeel Pre (left over from another system which will soon be integrated into another, thus the need for a preamp or upgrade the Benchmark to their new USB DAC/Preamp to Dynaudio Sub 250 to Dynaudio MC-15 powered speakers. Very good for this setting and more than satisfied now. Not sure what to do re getting a new amp. The Benchmark upgrade keeps things simple but also contemplating getting a tube preamp (something below USD 3000) as I never owned tubes so wanna try.