Originally Posted by Cam Man
All is forgiven Can Man! As a fellow rabbit hole dweller--I have a few thoughts.
For the record, I don't own any coaxial speakers at this time, I'll be building a pair this winter for surround use because coaxials (or concentrics) fit my requirements.
OK, with that out of the way--yes, I'm just shooting from the hip here so have mercy upon me!
Coaxials--they do some things very well, other things they are decent but are not the "go to" speaker if you are talking LCR use. This is just my ponderings, my opinion but something to think about.
Coaxials work wonderfully well as near field or "desktop" speakers--work great in car audio also since they are near field. Nice to have a point source when listening at one meter on a desk (or mixer) or when very wide dispersion is desired in all directions both vertical and horizontal (unless it has a horn flare like some old coaxials or B&C 15 inch coaxials) The smaller versions can have really wide dispersion, think of 5 or 6 inch coaxials and work very well for surrounds and so on. Much easier to build with coaxials, be it a car, small monitors for your desk or oddly shaped surrounds (my use) The "perfect speaker"? Well, not so fast--have to read the fine print!
Coaxials have issues--from the first ones made by Tannoy to the ones made by KEF, B&C, B&C and so on. There are two problems that jump out immediately, first the treble will interact with the woofer cone which moves--not a good thing in itself. Can't avoid that although some coaxials I've seen with a huge horn flare that extends past the cone which helps. From what I gather, the obect is to minimize cone movement by either using woofers or subwoofers to minimize cone movement. Making the cone larger helps wit efficiency and demands less cone movement for the same SPL. So bigger is better? Well, there is more fine print!
Once the cone gets very large, say over 8 inches then the crossover point to the tweeter must go down to prevent off-axis problems. Say around 1600 Hz for a ten incher, around 1300 to 1400 Hz for a twelve and so on. This prevents beamig just like in conventional speakers. Now you need to find a tweeter/compression driver that fits in the threaded portion of the magnet--not too tough above 2000 Hz but it gets much harder and more expensive as you go lower. Not too tough to get 1200 Hz out of acompresion driver on a large horn, very tough to get one to squeeze in the restricted space of the coaxial woofer--wrie off 1.4 inch and 2 inch compression drivers from the start!
The fun is not over--now the cmpression drver has to work well with the small horn flare that fits behind the dust cap--no big 10 to 15 inch SEOS horns for you! Say you get that done, the measurements work well on axis and off axis--after plenty of crossover manipulation and testing. This is what I call "the dark art of crosover building"--I'm not putting words in MTG90's mouth but I would bet it is much harder to get a coaxial to work properly with the limited space provided, the smal horn flare and get it all to work properly with passive crossover components.
The big clue was the time it took to create such a beast. Somewhere around 3 years and I'm willing to put my neck out and state it was one of mtg's biggest headaches--but through determination, a touch of insanity and the cost to make it right--itt is done. I was actually surprised at the low cost of the kits considering the time, cost of parts and the beer bills must of piled up. OK, the last one might not be true--but I would understand if it did.
They did menion the 15 inch coaxial would be better for IB (in wall) because it could make it to 80 Hz and has more Xmax to deal with IB. Looking at the on/off axis charts--they are outstanding for a coaxial! Most coaxials get a bit weird at higher frequencies but those measurements look very smooth.
Would I use coaxials for LCR? No, I'm in a living room so very limited acoustic treatments allowed so SEOS horns work better for me to limit floor/ceiling reflections. That huge dispersion characteristic can reach around and bite you in the butt there. However, I would love eitght of those 12 inch coaxials for surrounds and Atmos--my wife would divorce me but it would rock. For the guys with the 1899's, 1299's and Titan 630 XLs...your surround coaxials are readay!
Hope that helps more than it hurt. Just an overview and ponderings about coaxials, what they do well, what they don't and the pain it would be to design larger ones. I heard mention of 10" versions, now THAT would be something I'd like to have. Light weight neo drivers, a smaller box and something new and fun to play around with before they took their throne as surrounds/Atmos speakers. My inner voice informs me I need to build a 2.1 channel boombox with a chip amp and a pair of Volt 6's...and an 8 inch sub. My next build will be playing with coax speakers--should be interesting.
As with everything, it kinda depends on what you want the speaker to do, if it's strong points overshadow the weekeness in the configuration and if coaxial is the best tool to fix your audio problems.
OK, somebody out there wants to make 12 or 15 inch "truck boxes" just because. Enough of my babbling, now to see those unicorn coaxials roll out and see what kind of madness the rabbit hole dwellers have up their sleeves. Have a great weekend.