Role of sub woofers?

I had begun thinking about changing out the KEF Reference 1s for floor standers, something like Wilson Sophias, Revel Ultima Studios, or the expensive KEF Reference 207/2s. Then I reset the crossover for a pair of Velodyne HGS-15s from 40 Hz to 80 Hz, and the sound stage size, sound stage depth, and sound stage detail improved so strikingly thoughts of changing anything vanished. I did redo the speaker setup extensively, including redoing all the SMS-1 bass manager connections, so I suspect the vast improvement was due to more than just adding 40 Hz to the range covered by the the subs — I must have fixed some previously unknown problem. Anyway, a setup that I thought was best for jazz and baroque now does large orchestrations convincingly with a sense of spaciousness I had previously imagined only floor standers could deliver. One detail I’ve noticed is that the power-on LEDs of the subs that were previously rarely activated are now usually lighted, suggesting the subs are playing a much more active role.

Well about not changing anything: I have a third HGS-15 I might install on the wall opposite the setup for a three sub distribution.

Ag insider logo xs@2xdbphd
@dbphd , subs are a very complicated, tricky issue. That sense of openness you like is being caused by the slight echo in the upper bass lower midrange occurring between your subs and the main speakers. With the subs set at 80 Hz there is a small amount that leaks through. A cross over is not a cliff, it is a slope. Many people like this. Adding high pass filters will always increase headroom and lower distortion more or less depending on the design of the main speakers. It will also decrease the amount of overlap and get rid of that "echo."  The higher you crossover the the greater the increase in headroom and the lower the distortion. I cross over at 125 Hz but my ESLs are "one way" and so benefit most from this. Whereas, in a two or three way speaker only the woofer's range is going to benefit from lower distortion. A high pass filter should always improve the sound.   
db, mijostyn's terrific description may be adjusted out after another Auto EQ. Then by manually adjusting the Low Pass Xover Slope and Contour Frequency.

Velodyne's later Plus Optimization has a simple visual and audible drag and drop Q adjustment for individual bandwidth parametric filter frequency and level.

When used in conjunction with its discrete multi-band gain settings allow for a much higher crossover beginning with tone that closely matches the mains presentation from the crossover region on.

This replaces the hard crossover point used by most other equalization programs or basic settings.

You might give a thought to setting some of your presets with differing crossover and slope settings to help narrow down an optimum while your at the listening position. 

Once I tailored my crossover region it's saved to all the presets while the equalization after the region varies. #6 is a polarity reversal.

Thanks, mijostyn & m-db, for the enlightening posts. Last night I played several Blu-rays, with balanced analog from the Ayre DX-5 DSD to the KX-5 Twenty preamp. I thought the sound quality superb, so I’m unlikely to mess with the setup in the near future.

Charles Hansen contended that nothing should be inserted between the Ayre preamp and amp, because of their fully-balanced zero-feedback design. Nevertheless I tired an elaborate Bryston high-pass and a balanced passive custom. I ended up conceding his point.