I found a solution...

A long Reverb?

Use more dynamite.

Boom, boom.

A long Reverb?

Even though I've found a solution, I'm interested in this suggestion, How do you do it?

Thanks

I would record with 2 mics, one set with a medium gain and the other with less gain. Use the one that sounds the best.

Late answer, but maybe useful: Open audio file in Audacity (freeware, nice program) then apply Effect > change speed or Effect > change tempo, extend your selection to encompass the now-extended timeline, playback and tweak as needed...This will change the pitch, which is probably good for an explosion, not so good for other sounds, perhaps. We once used this to good effect in a video about a gymnast; she did a triple something, flying through the air and when we extended the timeline to slow the audio and video down for slo-mo, the sound of her hitting the padded gym floor was attention-getting! / Battle Vaughan/miamiherald.com video team