Diy jambox help?

The MM651 speakers were designed as "infinite baffle" type components, meaning all that has to happen is that the sound wave coming from the front of the speaker needs to be isolated from the sound wave that comes from the rear of the speaker. This is done because that kind of speaker is used in door panels and car rear decks with different internal volumes. The speaker's suspension provides the necessary stiffness. So, there isn't any specific tuning required by the enclosure volume, just make it as large as possible and no porting is needed.
The other factor is that tweeters used in car audio application are designed to have their best frequency response when measured off-axis. This is done because in car audio installations the tweeter placement is rarely level with a person's ear. It is either lower on the door or mounted on the top of the dash. So, when you install these speakers in your jambox it might result in an overly bright quality to the sound since the listener will be closer to having the tweeter at ear level.
I hope this is helpful information.