We are talking about monitor loudspeakers of course…
In this context, 'tight' is a subjective impression of how much control the speaker has over bass, particularly impulsive bass like kick drum sounds. The amplifier and speaker cables have a say in this too, since it is the amplifier that in some part tells the cone of the speaker to stop moving, as well as start.
So let's suppose you have an amplifier with a high damping factor, which means that it can control very precisely the movements of the cone rather than just shoving it forwards and backwards. Let's suppose that your speaker cables are short and thick, offering hardly any resistance to degrade the amplifier's damping factor. Let's suppose also that the speakers are really well designed in this respect. When the cone stops, it just stops with no overshoot nor oscillation.
This combination of factors will give you a really tight bottom end. (So tight you'll find it difficult getting into it in the morning!)
So in the confines of your studio, you're obviously really enjoying this. Not only can you pile on the bass, you can craft the low end and achieve real expression and subtlety.
Your bottom end will be a wondrous experience for all to behold…
Except that once your mix is released from your studio onto CD, vinyl, broadcast or whatever, no-one is going to be able to hear any of that. All your work is wasted. Worse still, you haven't taken account of what real speakers do to bass, and your mix probably sounds like a mess.
So in truth, you really do need a pair of monitors with a rather saggy bottom end. If you work hard to make your mix sound good on these, it will sound good anywhere.
And paradoxically, it might even sound better on your super tight monitors than a mix actually made using those monitors.
Any studio has room for more than one pair of speakers.