5-6" coaxials are getting quite popular, as a part of a three-way speaker. KEF, Elac, Genelec, TAD, Technics, etc. have them. There are also many raw drivers available for diy, one of the best and definitely not cheap is SEAS C18 E0060-08/06 C18EN002/A The diaphragm of the woofer is roughly 5", frame is 6,5" series
The 4-5" versions are perhaps not so good constructions, they often have non-optimal structure with tweeter integration (margins)
The 4-5" versions are perhaps not so good constructions, they often have non-optimal structure with tweeter integration (margins)
I would love to try out one of these coaxial one of these day. The theory is obviously good enough, but it seems like implementation of the tweeter can be tricky. Maybe there is good reason why high end speakers don't use coaxial. The only speakers that I know of that successfully done this is the Thiel CS2.4.
I have been considering coaxial too. I was searching around and I found a few additional entries to what has been mentioned; Emerald Physics and Spatial Audio. I believe the guy behind these designs is the same individual and he offers the Spatial Audio products at fair prices. The reviews are quite good (which makes me nervous/curious). I am sure I will dive in sometime in the not to distant future but I have no idea what I will be experimenting with at this point. Lots of good options on USSpeaker.com.
I've discovered there are just too many variables. Coaxial will help with image, but it's just one of many things to make the sound sounds good. A good coaxial driver may compromise in other areas that I find important.
One option (that I'm currently using) is JBL 328CT- it has a very well made crossover and JBL quality (though the compression driver's pretty low in their line) as well as a "waveguide" mounting system. It's a ceiling speaker by design but sounds superb as a mid/high. The horn tweeter uses the woofer as a waveguide.
I find that waveguide can be a double edge sword. A bad one will just beam the upper midrange that will make the sound almost unlistenable. I am sure there are some good ones out there but they all cost in some cases more than a car. I found that most of the
low end horn are just too poorly implemented.
Anything has to be an improvement. That is one harsh coax.
Do you like them with a better CD?
The 15" and now defunct 18" use a better compression driver, tho it wasn't the easiest to crossover. Very good on open baffle.
The new Hsu coax speaker is garnering some nice reviews, although mostly from home theater folks. Not diy, obviously, but not too pricey, and compact.
For home theater, I am not sure what's the point of coaxial? Other than maybe space? I guess that's why coaxial is popular in car because of space efficiency.
Excluding the options available in the sound reinforcement industry, coaxials limit the designer's choice of driver complement without commissioning their own models.
I'm listening to my 3" Kef coaxes right now. They're nice, but I'd speculate that they're pushing the 'practicality' of how small you can make a coax. I measured them, and found that the tweeter is just barely covering two octaves. A full range like the SB Acoustics SB65 probably makes more sense than the Kef coax.
Once the diameter approaches four or five inches, a coax starts to make more sense than a full range.
BTW, I think putting the tweeter on a 'bridge' works better than putting it in the neck of the woofer, particularly if you use a crossover topology that deals with the delay between the woofer and tweeter.
re: tweeter in front, here's a coax speaker I have that sounds pretty good - what might be done in their crossover ?
http://www.frazierspeakers.com/download/c40.pdf
http://www.frazierspeakers.com/download/coax.pdf
http://www.frazierspeakers.com/download/c40.pdf
http://www.frazierspeakers.com/download/coax.pdf
As mr. Bateman above put it, there's simply no point in small coaxials. Nor is there any point in a 2-way with a really small (read 2,5 inch or smaller) woofer.
Coaxial designs - as all loudspeakers - are always compromises. I guess it's a matter of choosing your poison. Now, as to why only a handful of so called 'high end' manufacturers have chosen to utilize a coaxial driver, I'm not sure. There are the classic Tannoy designs, KEF uses them, as does Devialet with their weirdly shaped active speaker.
I guess a part of it is what I perceive as the high end manufacturer's conservativity and lack of innovation and imagination. Really, when you go through a number of catalogues from even established companies, with models ranging from 2000€ to 50 000€, you basically see just variations on the same theme; 2,5 or 3-way svelte looking floorstanders. And almost always with a dome tweet and a 5,25" or a 6,5" bass/middriver. A 10" bass driver is considered large if not almost huge. The more expensive ones usually just claim to use more expensive, space-age materials either in their cones or cabinets. Fit & finish - though - is usually top notch. They might even sound ok.
Now, coaxials in general have their merits and downfalls. With a coaxial driver that uses the bass/mid cone as a waveguide/horn, you will have diffraction issues from the cone surrounds. How bad they'll be varies. And a clever designer largely goes around this issue by not designing the speaker to fire dead straight at the listener, since the FR ripples due to those diffractions usually smooth out pretty nicely when listening slightly off-axis.
Another way to work around those diffractions is to use a separate horn protruding it's way in front of the midrange cone. But this'll cause cavity resonances between the horn and the cone, and was thus abandonded by the likes of Tannoy in the nineteen fifties. And using a horn trades away the advantage of directivity patterns fitting together like a glove.
Again, using the bass/midrange cone as a waveguide/horn has the disadvantage of intermodulation of treble information by the midrange cone's movement. Something that's basically mitigated into oblivion by not moving said cone much. Which means you'll either have a large cone, not much SPL, or a 3-way design. The best would probably be a 3-way with large drivers, but a 2-way with enough cone area does seem to work well enough.
The advantages of a coaxial are that it's a point source, and when done right, the directivity patterns of the high- and low-frequency drivers match usually quite nicely together, which all works towards nice imaging and coherence of sound through slightly higher directivity compared to waveguideless designs, less distance needed to integrate driver response so as to not sound separate sources to the listener, and usually a slightly wider sweet spot.
To me, a nicely done coax usually sounds a bit more real, than most conventional designs. They're not in any way a magic bullet. But I'll put it this way: I could venture just a mile away from home to listen to a pair of Magicos or Audio Physics costing more for a pair than my used Alfa Romeo. And I've done that. And I still prefer my B&C 15-inch coaxials in their ugly birch plywood coffins. I admit, it's not just a difference between a coaxial and a conventional speaker, it's also a difference between a larger format driver vs. a smaller one. But still...
Coaxial designs - as all loudspeakers - are always compromises. I guess it's a matter of choosing your poison. Now, as to why only a handful of so called 'high end' manufacturers have chosen to utilize a coaxial driver, I'm not sure. There are the classic Tannoy designs, KEF uses them, as does Devialet with their weirdly shaped active speaker.
I guess a part of it is what I perceive as the high end manufacturer's conservativity and lack of innovation and imagination. Really, when you go through a number of catalogues from even established companies, with models ranging from 2000€ to 50 000€, you basically see just variations on the same theme; 2,5 or 3-way svelte looking floorstanders. And almost always with a dome tweet and a 5,25" or a 6,5" bass/middriver. A 10" bass driver is considered large if not almost huge. The more expensive ones usually just claim to use more expensive, space-age materials either in their cones or cabinets. Fit & finish - though - is usually top notch. They might even sound ok.
Now, coaxials in general have their merits and downfalls. With a coaxial driver that uses the bass/mid cone as a waveguide/horn, you will have diffraction issues from the cone surrounds. How bad they'll be varies. And a clever designer largely goes around this issue by not designing the speaker to fire dead straight at the listener, since the FR ripples due to those diffractions usually smooth out pretty nicely when listening slightly off-axis.
Another way to work around those diffractions is to use a separate horn protruding it's way in front of the midrange cone. But this'll cause cavity resonances between the horn and the cone, and was thus abandonded by the likes of Tannoy in the nineteen fifties. And using a horn trades away the advantage of directivity patterns fitting together like a glove.
Again, using the bass/midrange cone as a waveguide/horn has the disadvantage of intermodulation of treble information by the midrange cone's movement. Something that's basically mitigated into oblivion by not moving said cone much. Which means you'll either have a large cone, not much SPL, or a 3-way design. The best would probably be a 3-way with large drivers, but a 2-way with enough cone area does seem to work well enough.
The advantages of a coaxial are that it's a point source, and when done right, the directivity patterns of the high- and low-frequency drivers match usually quite nicely together, which all works towards nice imaging and coherence of sound through slightly higher directivity compared to waveguideless designs, less distance needed to integrate driver response so as to not sound separate sources to the listener, and usually a slightly wider sweet spot.
To me, a nicely done coax usually sounds a bit more real, than most conventional designs. They're not in any way a magic bullet. But I'll put it this way: I could venture just a mile away from home to listen to a pair of Magicos or Audio Physics costing more for a pair than my used Alfa Romeo. And I've done that. And I still prefer my B&C 15-inch coaxials in their ugly birch plywood coffins. I admit, it's not just a difference between a coaxial and a conventional speaker, it's also a difference between a larger format driver vs. a smaller one. But still...
Last edited:
Your 15in. will do things smaller drivers can't do, but my guess is in term of mid range speed and micro detail, a 15in. cannot compete with smaller drivers of the Magicos or Audio Physics.
Guess again... Effortless detail and perceived speed is something large drivers do really, really well. Smooth measured response is something smaller drivers tend to excel at.
Another thing that might be a problem with coax is that the woofer cone is basically just a shallow conical horn. In other words its profile isn't ideal, and not likely what you'd design if you used a seperate horn or waveguide. That may be one of the reasons Tannoy, Altec and others put a horn in there. Not without its problems, either.
Radian has got some new coax drivers as well. One with a planar driver mounted in front and the rest mounted at the rear like a more traditional compression driver. Thinking about playing with some for HT surround duties.
Ribbon Coaxial Archives - Radian Audio
Greg
Ribbon Coaxial Archives - Radian Audio
Greg
- Status
- Not open for further replies.