There isn't a specific pitch/pressure/tension, but there is a proper tuning range for a djembe for it to sound best. You can hear this if you listen to some recordings of djembes or hear them live played by experienced players. Perhaps you can find someone with some experience with hand drums in your area who can help.

If you're experimenting on your own, make sure to keep the tension of each of the tuning rods relatively even. If you stretch a goatskin or calfskin head unevenly and leave it that way for long, it can be a very difficult thing to correct.

Also, try posting in the percussion forum one below this. The hand drum types frequent that area and may have missed this thread. They may be able to offer more help.

Good luck!

As mentioned, traditionally the Djembe is tuned so the drumhead is very taunt ... table top tight. This makes the slaps (Pa/Ta) crisp and easier to play while reducing the amount of "ring" in the resonance of the drum.

Take care when tuning. Make small adjustments moving around the drum from lug to lug.

I wanted to mentioned that the Drummer Cafe is now an affiliate of African Drum Store. I'm going to be reviewing one of their Djembes, which is an incredible instrument, especially for the money ... which is comparable to the Aspire Djembe price wise. In fact the current Drummer Cafe contest is giving away one of their Djembes ... so check it out!