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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
soundsrealaudio's avatar
soundsrealaudio
756 posts
 
Well I am a huge 2.5 way fan. My fav are the Wilson Benesch. As suggested they use the same size midrange as woofer and work very hard to create a woofer that is as fast as the mid range so there is no loss of coherence. The woofer does woof and the mid because it is 7" can go down to 500hz. I think unlike many 2.5 way speakers the WB's midrange goes all the way up to 5000 kHz and this covers almost the entire midrange with male voices and cellos sounding very full and rich.
erik_squires OP
16,052 posts
 
@timlub

Everything that Erik has quoted throughout this thread is correct.

Thank you kindly.

@marqmike

This has been a great thread for me to understand a little bit better about something I enjoy. Thanks Eric for the thread

Glad to be of service! What makes these threads interesting is the wide variety of experience and expertise everyone brings to them.

Best,

Erik

mirolab
208 posts
 
As a DIY speaker builder, I've logged many hours building & tweaking crossovers, and one big compromise of a 3-way design is the HP filter you have to put on the midrange.  This is, at the very least a large capacitor to roll off at ~350 Hz, plus a large inductor too for a 2nd order.  These components are now in the signal path of your crucial midrange frequencies, and they're also affecting the phase alignment of the midrange with the tweeter.  You may also need to invert the polarity of the mid driver (or not)... it just depends on other parts of the design.    The 2.5-way design has fewer crossover components in the way of the midrange, and has more low end capability than just a 2-way.  There still will be some phasey issues between the 2 woofers as the lower woofer rolls in to align with the upper woofer.   I admire the idea, but I've never built or owned a 2.5 way design.
timlub
2,039 posts
 
@microlab
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.
willmacc's avatar
willmacc
80 posts
 
Bump start this thread as I have just come across it

My take on 2.5 ways is that the benefits are only if using roughly 5.5" driver size. Plus points- covering 400hz and below is covered by the surface area of 2 drivers. So baritone vocal range can be surprisingly good with 2.5ways. Also as 2 drivers share bass duties the top midbass driver has less work to do (no bsc) compared to a 2 way and mids will benefit. Still, a 3 way is better in this respect.
Also cab size is kept compact. I dont like the term ’WAF’ but a small footprint with good bass output is attractive.
One disadvantage is a sometimes boomy bass which requires bringing the speakers out into the room. Which kind of defeats the purpose of compact and room friendly. This is due to the 6db gain from the bottom woofer. Typical room gain adds around 2db lift at lower frequencies, so the baffle step compensation of adding .5 woofer can often be too much.
Hence surprised we dont see more sealed design 2.5 ways imo.
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