16ohm midrange drivers

In order of preference

GR Research M130-16 -- nice driver, good mids, and apparently good bass, but I used them in a 3-way

Vifa M13SG-09-16- very easy to work with. don't think it would have the bass of the GR drivers, but very nice mids.

either way, think of your room size and if a pair of 5" a side is really enough. Bass will be your problem.

then look at

Both these provide a true full-range speaker, which you will not be able to achieve with a 5" mtm

(4 ohm drivers in series will work too)
Here is an interesting driver that should get you down into the lower midbass region.
Also with such a high Qts, I would think they would work great on OB as well.

I have not listened to these exact drivers, but have heard their fullrange cousin, and I like them. The price is not to hard to take either.

If you are not looking for a two way that goes down into the 30Hz region, this driver should be a good candidate.
Not sure if this is what you are looking for with a combined efficiency of around 88db and FS of 65Hz.
They should sound pretty good in an MLTL, or BIB cabinet if the Qts is not to high.

It might help others to make better driver suggestions if you tell us specifically what you want from your speaker. Things such as room size and what type of amplifier that you intend to drive them with, tube or solid-state, and output power.
You may need a pair of 10" to 15" pro-sound drivers from for all that anyone would know from your brief description.

Good luck in your search.