Dynamic loudspeaker

Claim 1

In a loudspeaker of the kind having a frame, a cylindrical center magnetic pole, an outer magnetic pole disposed around the center pole to form an annular flux gap therebetween, said outer pole and center pole being interconnected at their rear ends by a back pole plate, a speaker cone mounted on said frame in front of said poles for acoustically radiative reciprocation with respect thereto, said cone having an axially disposed dust cap thereon, a tubular voice coil mounted on the back of said cone and positioned in said flux gap, and an antifriction bearing member for said coil disposed in continuous sliding contact with said centerpole, the improvement comprising: a grille positioned on said frame in front of said speaker cone; a first bumper formed of resilient material mounted on the back of said grille, said first bumper being positioned and proportioned to lie forwardly of the largest desired forward excursion of said dust cap, said largest desired forward excursion being insufficient to displace said bearing member from said center pole, and to resiliently and quietly stop forward excursions of said dust cap which are larger than said largest desired forward excursion, said first bumper thereby affecting only those forward excursions which are greater than desired; and a second bumper formed of resilient material mounted on the forward end of said center pole, said second bumper being positioned and proportioned to lie rearwardly of the largest desired rearward excursion of said dust cap, said largest desired rearward excursion being insufficient to impact said bearing against said back pole plate, and to resiliently and quietly stop rearward excursions of said dust cap which are larger than said largest desired rearward excursion, said second bumper thereby affecting only those rearward excursions which are greater than desired.