Need suggestion on 2.5 way MTM crossover, please

[Misa A.]

I am about to finish cabinets for my speakers of the dream, which are MTM Scan Speak 8545-9500-8545 in a TL enclosure. Now it is a time for a crossover design after I measured drivers’ in cabinet SPL curves.
Initially I planned to do it classical D’Appolito – 2 way with woofers wired parallel. But there are 2 disadvantages to this design, which make me think of possible alternatives:

1. Nominal impedance of the system is 4 Ohm, just a half of a single driver, which is not exactly good for my amp, and

2. Directivity diagram in vertical plane is too narrow. The problem is that, because of the little size of the room, my main listening position is 15 degrees down from tweeter axis.
Classical 2 way design gives at this angle a big SPL deep in the crossover area of 2 kHz.

I know that some people prefer 2.5 way design. I saw some examples with series crossover for a tweeter – midbass circuit, but it is 1st order and I am not sure it will work with my drivers, as I want to keep the crossover frequency not higher than 2 kHz.

Could you please give me some suggestions on possible topology of a crossover for given set of drivers with wider vertical directivity and higher total impedance?


Thank you in advance,

Misha

[sreten]

15 degrees down from tweeter axis ? do you mean up ?


TMM is the usual arrangement for 2.5 ways with a better treble axis.

There's nothing you can do about the system impedance.

You could try this 2.5 way series c/o :

sreten.

[Misa A.]

Thank you, Sreten

I mean down 15 degrees, because I like to listen to a music in the night and I sleep on the floor because of my back..
I know TMM is better but it's too late to change cabinets. I think at lower frequences woofers in MTM layout will not produce too big phase shift.

There is a similar design to what you suggest

.

and it gives impedance of around 5 Ohm, as author says.

I just don't feel well about series crossovers.

Are there some 2.5 prototipes with parallel topology?

Misha

[sreten]

In that case you can choose which driver to use to reproduce
midrange, which will control the tilt of the polar response, unless
the drivers are exactly phase aligned.

Usually using the top driver has an upward tilt, the bottom down.

sreten.

[Misa A.]

OK, it looks I will have a lot of fun modelling and experimenting with this stuff..
The beauty of my cabinets is that I can go from one approach to the other because every speaker has it's wire going outside.