Does a Subwoofer give relief to my mains speakers?


My main speakers have two 12" woofers per cabinet and give great bass response for movies....though sometimes when the bass gets really low and powerful on dvd's (Gladiator battlefield scene), it causes the woofers to sound like they are coming apart....this never happens with music. Will adding a subwoofer relieve the stress on the woofers in my main speakers? Will the bass be as powerful? I'm considering the Velodyne HGS 18 or the Infinity HPS 1000. My room is 22ft wide and 70 ft long with 22 ft high ceilings....carpeted concrete floors and concrete ceiling....the building was once a beer brewery and has been converted to live-in lofts.

Preamp..............Audio Research LS-10 solid state (no phono input)
Preamp..............Carver C-19 Tube (I have it connected to the AR LS-10 and use it for a phono preamp)
Main Speakers............Infinity Kappa 9 (bi-amped)
Amp.................Carver Silver 9-t monoblocks (low pass)
Amp.................Sunfire Signature (high pass)
Rear Speakers.......Infinity Kappa 7
Center Speaker......Infinity Kappa Series II center
Amp (rears).........Carver TFM 42
Amp (center)........Carver TFM 42
Phonograph..........Oracle Delphi Mk-I
Cartridge...........Grado Reference Platinum
CD Player...........Carver SDA/360 5 disc changer
Tuner...............Sansui TU-X1
Surround Processor....Technics SH-AC5000
Convert?fit=crop&h=128&rotate=exif&w=128mitch4t
Hi Mitch, am I correct to assume that you have the signal to your Kappa 9s set to "large" and subwoofer set to "off"? I think by adding a sub and changing that setting to "on" you'll be relieving the Kappas of some of the explosive effects that are causing those over-excursions and letting the sub handle them. Have you tried this setting even without a sub just to see if there's a difference at your mains? Is there any mention of this in the manual for your Technics processor?
Subs definitely give relief to the mains on home theater use. Let the subs pick up anything below 80hz. In music mode if you have control lower that to 50 or less.
Gunbei...you are correct I do have the speaker setting to "large" and the subwoofer set to "off". Your solution makes sense. Now I have to go and buy a sub. Thanks.