Fun with RTi A speakers

Having been thoroughly impressed with the results of using Larry's rings on various SDA speakers I decided to do something similar to the RTi A7's, the RTi A6 and FXi A6's in my HT rig. As T-nuts were out of the question I looked around and found what are called Hurricane nuts at Parts Express with an 8-32 thread pattern. I also purchased a quantity of 8-32 x 7/8" stainless steel cap screws from Grainger. The Hurricane nuts are noted as working very well with MDF. They have 4 burrs cut in at the top of the post, which bite into the MDF from the twisting motion as they are drawn in place.

I knew before the start that this was not going to be an easy job and it turned out to be even more difficult than I imagined. There is not much of a mounting lip around the driver cut outs and the bottom front port cannot be removed entirely from the cabinet. As the round flange on the Hurricane nuts protruded too far into the driver cavities I used a Dremel with a heavy duty cut off wheel (a lot of them) to cut off part of the flange creating a flat side. I did these one at a time while held in a vise. This was not necessary for the tweeter or ports as there is ample MDF around the screw holes.

After removing the tweeter, drivers and small port from one of the RTi A7's, I used the recommended 13/64" drill bit to enlarge the existing screw holes. For the bottom port I had to hold it off on an angle in order to drill out the holes. Once the prep work was done I started with the easy ones, the tweeter and small port. While holding a nut on the back side of a new hole I used one of the new cap screws with a thick #8 stainless steel washer to draw the nut into the MDF. I used a T handle Allen wrench to start it off and finished up with screw gun set on high torque. For the drivers I used the same procedure, except that I had to start with part of the nut's flat side showing because as the nut is drawn in it twists. If done just right the nut will seat with none of the flange visible. Of course, this didn't always work 100%, so on some I had to use the Dremel with a grinding wheel to remove what little of the flange protruded. That all went smoothly enough, now the real fun began. The screw holes on the bottom port are extremely hard to get to from inside the cabinet. I had to reach in thru the bottom driver cut out, down past the bracing and contend with the tube for the port. Basically, my arm was inside the cabinet up past my elbow trying to feel around for a screw hole while holding a nut and trying like hell not to drop it. This part is not for those lacking patience or spacial relation skills. In reality, it isn't necessary to do this mod to the large port, but I wanted all the screw heads to match. After what seemed like forever, I was able to get the 4 nuts for the bottom port seated and started to remount the tweeter, small port and drivers. A few times the nut and cap screw wanted to cross thread. On those I used a 8-32" tap to clean up the nut threads. Keeping in mind that the bezels are plastic around all of these, I used caution when torquing down the new cap screws, but was pleased to find that I was able to snug them up tighter than I initially thought.

I left the bottom port for last and of course this is where things went very wrong. I had been starting the cap screws by hand, driving them in using the screw gun on low torque and then finishing with the T handle Allen wrench. On the very last hole of the port the nut and screw cross threaded (despite starting ok) while using the screw gun causing the Hurricane nut to strip out of the hole. I spent the next several hours trying to get a grip on the stripped out nut with various tools. After great difficulty, I was finally able to get a micro size vise grip on it and snap it off. Fortunately, I had a few of Larry's tweeter rings around and used the end of one as a substitute. I drilled out the hole a little larger to accommodate the larger diameter and used epoxy to glue it in place. The rest of the speakers went much smoother, thank God!

The end result made the effort worthwhile. There is more presence and weight to the mid-range as well as more punch to the bass.

Before anyone considers doing this to their speakers, I want to warn you that this is not an easy job, there is very little room for error and it will take a lot longer than you might think.



Link for the Hurricane nuts, http://www.parts-express.com/pe/showdetl.cfm?PartNumber=081-1080

The stainless steel cap screws are available from many sources.