Subwoofer and 2 channel system - need to use crossover at all?

I love my Velodyne DD10 powered sub. (I have two, but one failed.  As others have said, a second does not make a big difference in a small or medium sized room).

My question is whether I should use a crossover at all with my 2-channel configuration.  Velodyne recommends running the signal lines from preamp to the sub, thereby using its crossover, and then running the remaining higher signal from the sub to the main speakers.  They say the sub plays the low signals "better" and relieves the main speakers from playing low frequencies, enabling better mid- and high- performance.  My preamp (Bryson PB25) has two sets of signal outputs, so I CAN send a full signal to the sub and to the floorstanding speakers - B&W Matrix 803 S2.  The B&Ws are rated down to 35hz and have 2 bass drivers each, but do not have deep bass like a good sub.  The B&Ws are overpowered - 600W monoblocks, so rationing amp power among the drivers is not an issue.  Currently I am running a full signal to both the B&Ws and to the sub and it sounds great.  I know that I can play around with the other configuration, but what does theory say?  In a 2 channel system without power constraints, should one allocate the low signal (at 60 or 80hz or whatever) exclusively to sub or let the floorstanding speakers and sub each have a full signal, and overlap output as they may?  Thanks


In theory, theory and practice are the same. In practice, they aren’t.

I’d experiment and go with what sounds best.

You’ve got ’amp’le power (pun intended), so I wouldn’t worry about any claimed strain on the amps, or your speakers.

I’ve heard many systems that use a sub with full range speakers being given full range signals and they have sounded just right.

All this hand wringing over poor little speakers and amp strain is over blown.

Deal with the room, get your speakers and sub placed as best you can, spend the time to adjust the sub's phase and xover - then just enjoy the music and quit stressing.

imho, of course.

lots of great information here.

i’ve consistently found high passing the mains superior to letting them run full range, but as always, YMMV.  delaying the mains was also revelatory, as described in the article above. 

One of the benefits of using subs is to relieve the main speakers the task of reproducing the deepest bass. The speaker’s woofers then produce the upper bass with less distortion at higher SPL, using less power. But inserting a x/o into the signal path to your main speakers may slightly decrease the transparency of your system. An old way around this dilemma is to install a simple 1st order (6dB/octave) R/C high-pass filter on the input jacks of the amp powering the speakers. The values of the resister and capacitor define the corner frequency at which the low frequency roll-off begins. The formula for calculating the frequency is all over the net.

Those poor ’lil old 803s2s, you should neuter them at 100hz at god..think of the strain! And your mono blocks, best not even risk taxing their 600watt power with scary bass.