Originally Posted by
HCSGuy
I'm running off memory here, so forgive me if my advice is not perfect. The AC-3RF input on your receiver is only for an old laserdisc with an AC-3 RF output. There is no other use for this from any component. However, your TX-DS939 should have other digital inputs (Optical/Toslink and Coax) that are capable of handling a bitstream dolby digital signal. Some receivers let you assign these around to different inputs, so make sure yours are assigned to whatever input you turn the receiver to for listening. Also, go into the setup menu of your DVD player and make sure the digital output is set to bitstream and not PCM. Many of them default to PCM output which your receiver will decode with Dolby Pro-Logic.
If you change your surrounds to butyl rubber, expect the performance changes from a heavier cone - your transient response will be slower and freqency response at the top of the drivers range will roll off sooner. I have not done this, so my input is purely theoretical.
Hope this helps!