Is the 2.5 way speaker the ideal home speaker?

Time for what I hope is another fun thread. 

One type of speaker which is actually pretty common but which gets little press / attention here on audiogon is the 2.5 way. 

A 2.5 way speaker is almost a 3-way, but it isn't. It is a speaker with 3 drivers, but instead of a tweeter, midrange and woofer (TMW) it lacks a true midrange. The "midrange" is really a mid-woofer, that shares bass duties with the woofer. Often these two drivers are identical, though in the Focal Profile 918 the midwoofer and woofer were actually different drivers with the same nominal diameter (6"). 

The Monitor Audio 200 is a current example of the concept, but I am sure there are many others. It's also quite popular in kit form. One of the most high-end kits I know of is the Ophelia based on a ScanSpeak Be tweeter and 6" Revelator mid-woofers. I haven't heard them, but I am in eternal love with those mid-woofers. I believe the original plans come from the German speaker building magazine Klan Ton. 

However many other kits are also available

But regardless of kit, or store purchased, are you a 2.5 way fan? Why or why not? 



Showing 2 responses by timlub

Most of the human voice in singing operates from 80 for very low bass male voice to around 1500 which is above natural female vocals to maybe someone trying to hit an extreme note to impress.
Everything that Erik has quoted throughout this thread is correct.
A couple of things that I thought of reading through the thread.
**Crossing a tweeter low: sometimes its a no brainer, the mid has a dip or peak and you need the tweeter to cover that range for a smooth frequency transfer... Other times, I have listened to the mid and the tweeter both at a given frequency and thought the tweeter sounded better and chose to cross lower for that reason.
The rule of thumb for how low you can cross a tweeter is 2x its resonance at 12db per octave. This can be broken depending on tweeter, but it is a good general rule to follow.
For me an optimal in theory speaker would be a 3 way crossed somewhere around 80 on bottom and 2200 to 3k on top. This keeps the deep bass off the mid which really helps keep it clean and it also keeps the crossover out of any critical vocal region. Of course finding perfect parts to put into practice are not always so easy.
Erik, you’ve done a great job with this thread. Getting folks to understand a 2.5 way vs a 3 way isn’t always easy.
If you properly account for the resistance of a coil and use quality parts, I’ve not seen a problem with crossing at 350 hz. A simple cap will typically run between 50 and 150 mic’s. An inductor can certainly add phasing problems... using an inductor and porting can cause real phase issues in a woofer, but with proper crossover point selection, using driver compensation and quality parts, most issues can be avoided. I would highly recommend that when you can to just avoid using 12/12 slopes, that will normally stop the need of having to reverse polarity. 6/12 or 12/18 butterworth are both more phase coherent than 12/12 anyway. If you need to run 12/12, choose linkwitz slopes.