I'm not talking about really hitting the volume, more just digging in or especially slapping, even at low volume but with intention.
Its actually one of the things I like about the 121P combo. I can make it sound like its working hard while still at a moderate volume.
Again, I may very well be wrong here but I'm thinking its kind of like when Genz Benz made the 6.0 head in their combo a bit attenuated in the lows so guys wouldn't blow the speakers in the little combo's. Only that's how they sold it even out of the combo. I'm thinking maybe Markbass only tweaks the combo heads, which might be why they say not to take the combo heads out of the box, even though it looks exactly like a regular LMIII with a square hole in the middle of the top.
I'm pretty sure that is not the case. One of the things that makes that little combo sound so good is the amazingly full, deep, low end. The bad news is, a single 12 that is tuned that way in that little box will give up the ghost on those strong transient peaks of slapping, etc. Actually, the Genz design of eliminating the deep low end of that earlier Shuttle combo resulted in a somewhat thin, brittle tone (IMO), but surprising volume with not that much compression, since the head wasn't pumping lows into that little box. There is no free lunch, only design decisons.
Also, remember (per your comment about 'not at full power) that the knob position of the master gives you NO indication of the power being put out by the amp. All the master volume knob does is reduce the gain going into the power amp, hence controlling volume. You can easily drive an amp to full power and limiting (or clipping) with the master set quite low with the huge transient spike you get when slapping (even with good controlled technique like yours). That will result in a small, low tuned single driver to compress like heck on those transients.
Unfortunately, those of us that use the slap technique at all, or those who like to really dig in but still stay relatively clean, need about double the rig of those who have a more polite technique, or who play only fingerstyle, to achieve the same non-compressed maximum volume using all those different playing styles.
That little combo can cover an amazing variety of gigs, at surprising volume... until (like most other small rigs other than a really good 210 or a 'super 12') you slap at high volume or really digging in.
Finally, like many combo's, the reason MB indicates you shouldn't take the head out of the combo is that it does not have a top on it.
IME!
