Go for sub or larger speakers?

For 2-channel audio, I prefer to avoid a sub. I'd rather that a top-rung speaker designer design my crossovers, than me.

I use the hardware Edorr identified, but in a different configuration. I filter the main signal with the NHT X2 and run the bass signal out of the X2 into a Velodyne SMS-1 room EQ unit, because:

My current room, like every other room I've measured, gets very ugly below app. 125hz. I can (and do) fix it down to app 75 hz with bass busters. Below that, active bass EQ is the only workable solution that I've found.

If you run main speakers that have any real output below 75hz, it will IME be very difficult to get seamless integration of the subs and mains because the main speakers are contributing very lumpy bass until their roll-off. If you filter the mains to remove bass below 75hz (or at whatever frequency your treated room dictates) you can get smooth response from the mains, smooth response from the EQ'd subs, and a neat hand-off that will hard/impossible to hear (for me anyway).

If your main speakers have little to no output below 80, 90, 100hz, (i.e. Sunfire cinema Ribbon Monitors)you can probably run them full range and "snug up" the subs from below. Otherwise, I prefer to filter the mains.

As Stanwal, noted, there are 2 schools of thought, and this is the school I'm enrolled in. Others take the alternate route.

Two more thoughts:

1) "Fast" is a descriptor I dislike for subs. People tend to think small drivers are fast, and - IMHO- that's not the case. I think "highly damped" probably communicates the idea at hand - tight bass with little overhang - but this characteristic is not related to driver size.

2) My set-up does put the NHT between my ARC LS-25 and my ARC 130SE, but it keeps the Velodyne SMS-1 out of the main signal path. The NHT seems to be benign (to my ear at least) but the Velo has no business in the main path.

Marty

Martykl, I'm sure in some systems your approach will work better than running the mains at full range. Its a trade of between smoother integration and the degradation of running the mains signal through an additional active filter. If I had gone down this path, I would personally not have used the NHTX2, but get a higher grade crossover like a Marchand XM44.

This may be pure snobbery because I have no proof whatsoever an XM44 sounds better than the cheap NHT, but I would not like the idea of running my main signal through a cheap crossover when I have some very high grade electronics upstream and downstream. (Sort of the "weakest link" theory). Your appear to be owning some fairly expensive kit yourself, so I would definitely try out a higher grade crossover sometime and see if you get any improvement.

Hi Sashav,
Alot of opinions here. My experience says, if you like the sound of your smaller speakers and your amp will power them properly for the room your are in, you are fine and can achieve wonderful results with a subwoofer. You can run into a problem crossing. If you do not us an electronic crossover to cross your satellite speakers where you want them to blend with your subwoofer, you will need to cross your sub woofer around the 3 to 6db downpoint of your satellites I use a subwoofer now and cross it @ 40hz (its lowest setting). My speakers are 3db down at 38, I set the woofer low and slowly added until it was smooth, played a bit with the phase switch, had to move the woofer a couple of times, but ended up with a very smooth transistion.
As far as woofer size... on a properly designed woofer, size does not matter. A designer should have more motor to match the mass. Good 15's are fast, but you should try to listen to the sub that you want first and consider your room size, an 8, even a 10 would not move enough air for my room.
On the other hand, if you really like the larger speakers.... your done.