To ensure that your voicings create a clear impression and that the intervals they contain will be heard distinctly, do not include intervals below the limits shown in the chart below. There are always exceptional cases in which these limits may be adjusted downward. But if you follow them strictly, your voicings will never sound muddy

Whenever the bottom note of a voicing is not the root, "assume" there is a root and then check that the voicing follows the low-interval guidelines. In the example shown below, the C7 voicing confirms to the guidelines. But in the A-7 voicing, after we assume the root, the resulting minor third interval falls below recommended low interval limits (LIL).

References

"Arranging for Large Jazz Ensemble" by Dick Lowell and Ken Pullig, Berklee Press, Boston, 2003, page 8