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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? 

Best,


Erik 
erik_squires
erik_squires OP
16,057 posts
 
@Cedargrover 

Indeed, but this is what crossover designers must do anyway. In any multi-way system there is almost always some level matching that must occur, in this case that as well as the dimensions of the upper woofer enclosure must be carefully balanced. 

Best,

E
cedargrover
302 posts
 
Thanks Erik. I had assumed (perhaps wrongly) that in a 2.5 way, only the woofer physically closer to the tweeter plays up to the crossover frequency of the tweeter (say 3 kHz), and the other woofer has its low pass set to a lower frequency (say, 500 hz). I thought that was done to prevent lobing, but defer to you.

In such an arrangement, the level matching seems a bit complicated because some of the frequency range up to 3 kHz is covered by two drivers and some of it by one.

EDIT:  According to this article (http://www.bambergaudio.com/technical/2pt5.php) this complication can be taken care of by not adding baffle step compensation.  Pretty cool!
erik_squires OP
16,057 posts
 
@cedargrover I think you have it backwards.

The top two drivers are just a traditional 2-way.

The treble covers above 3kHz.

The midrange is only covered by the upper woofer. Say it has a low pass at 3 kHz.

Up to here, this is a normal 2-way. The added 0.5 is the lower woofer, which  cuts off at 500 Hz (for example).


cedargrover
302 posts
 
Think we're saying the same thing.  But thanks for reminding me that I know just enough to be dangerous....  :)
kijanki's avatar
kijanki
4,428 posts
 
What I mean to say is, there is no 1 ideal dispersion pattern. From ESL's to open baffles, to traditional multi-way speakers, some with horns. All have very different radiating patterns, and all have ardent fans.
It is not a dispersion pattern for particular speaker but for the group of them.  Speakers that have large membrane (2.5 way) will suffer.

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