I've never used poplar as a wood for a pot call. Something I have found, which may be something to consider in your sound. The softer and lighter of the wood, the more muffled and dead sounding it will be. The harder and denser it is, the louder and crisper it will be. The sound waves created by the surface from you striking it, are absorbed by the softer wood, and reflected more in the harder woods, in which they make the soundboard vibrate to produce the sounds your looking for. You did not mention the depth of your call from the bottom of your soundboard to the back wall, or bottom of the call. This "Volume" of air space is important to the sound created in the call. Too much volume, the lower the tone, too less, and it will be screachy. Think of it as a musical instrument. Let's use brass as an example, a trumpet pruduces a much higher tone, than a trombone, which is higher than a tuba. Catch my drift? Understanding what influences your sound, will go along way in what you have to do to change to get your end result. Hope this helps.
