Chained speakers signal connected in series

@fiesta75, 

Can we agree that Rt equals 16ohms in series?

Yes

Can we agree that Lt = L1 + L2 in series?

No, IMO, the first woofer will see the voice coil of second woofer as an inductor in series, same for the second woofer, it will see the voice coil of first woofer as an inductor.
I think the total inductance should be Lt = L1 + L2 + Lvc1 + Lvc2

Can we agree that 1/Ct = 1/C1 + 1/C2 in series?

Yes

it's yes to the above, then simply plug those numbers into the equations. f = R/2πLQ and f = Q/2πRC. 

May be a crossover design simulator software can give us a better answer.

Even if L1 and Lvc1 are present, L2 and Lvc2 are also present. If the frequency of the crossover is say 2kHz., it will remain at 2kHz., because L1+Lvc1 equals L2+Lvc2. Is that not correct? L1 = L2 and Lvc1 = Lvc2 for each speaker. Both inductances are present whether they are used to calculate the crossover frequency or not. Correct?
Perhaps a crossover design simulator would give us a better answer, I am willing to listen to your presentation. That could save me the hassle of posting sketches. I think we are both capable since we have been working to solve the problem with likklegerry's crossovers. I will be waiting.

 While you're listening through your pencils: you're going to simply ignore everything that a voice will induce to a signal, when actually presented with music?

                                        HILARIOUS (in a tragicomedic way)!

     Best broaden your horizons, as to what goes on (and can be measured/calculated) when certain elements (ie: caps and voice coils) are actually under the influence of *changing frequencies (ie: an actual audio signal) as opposed to DC (ie: a multimeter).

     *Ever looked at the impedance plot of a woofer, actually being used in a circuit?

       (https://audiojudgement.com/speaker-impedance-curve-explained/)    

           (https://www.apogeeweb.net/tools/reactance-calculator.html)

       Perhaps: even plug some of those facts, into your calculations?

  (http://oer2go.org/mods/en-boundless/www.boundless.com/definition/reactance/index.html)                
 
                       NAH, why bother with Physics, right? 🙄

          ps: I only bother posting such things, knowing they will be ignored by most, BUT: hoping someone out there remains interested in facts/learning.

                                             Happy LISTENING!

@fiesta75,
I think it was 7 or 8 years ago, my friend use Hornresp (http://www.hornresp.net/) did a simulation on his speakers and found that connect two speakers in series the low pass filter cutoff frequency get lowered, our conclusion was the first woofer will see the voice coil of second woofer as an inductor in series, same for the second woofer, it will see the voice coil of first woofer as an inductor in series, and caused crossover point lower than a single woofer alone.

If Lvc1 does not equal Lvc2 in a dynamic setting, then it maybe possible to perceive a change in the crossover frequency, maybe even measure it. I’m saying in a "grade school" math equation, the data does not support this. I personally don’t ever connect speakers in a series configuration, for MORE than one reason. It just would be nice to see some actual data from some physical testing or calculations that will support the crossover frequency change. Does anyone want me to post sketches or does everyone understand the circuit? I don’t want to spend more time on this subject unless someone has proof to show me. Enjoy the music!