Opinions on MTM or tower layouts

[stevem]

I have no experience listening to MTM or D'Appolito design speakers. I have always owned tower or tweeter-midrange-woofer type speakers. Has anyone here had experience listening to both styles with the same or similar drivers? Do you have a strong preference as to which approach sounds better?

[duaneage]

The MTM gives great dispersion if the crossover network (3rd order) is properly designed. That is the key to the design. Dual midbass drivers also are more efficient so sometimes the tweeter can be run without an l-pad network.

Most MTM designs use 6 inch or smaller drivers. The distance between the two drivers needs to be tight to give proper imaging or there will be problems. I am working on a MTM system design now with two audax 6 inch drivers and I have to design a proper network for them.

[Ian Mackenzie]

Its nice in theory but in practise an MTM is never really a true MTM, particularly when using large drivers.

You might actually find more success with MMT or M1/2 MT using JBLs. The problem being the conflicting requirements of the distance b/n say a two 15 inch driver centres and a horn mouth in the middle versus crossover frequency. The woofers will lobe with comb filter effects unless the crossover frequency is low enough and that invites other problems. Imagine the size of 500 hert conical waveguide.

That's why you see small dual MTM 6 inch systems out in the market place crossing over at 2200-3500 with a Vifa Ring Radiator. A 6 inch woofer / midrange driver is at best 88 db sensitivity and with two you get another 3db so its quite workable in that sense.