Why are coaxials so rare?

[dfuller]

Few reasons...
1, they're much more complex to engineer and build than a standard speaker - Everything is doubled and the concentric nature makes design and assembly trickier. This makes them more expensive.
2, They don't necessarily offer any benefits that make the expense worth it. Vertical dispersion isn't super important compared to horizontal, and horizontal can be made adequately good without the difficulty of coaxial design.
3, They require quite a bit of care in designing to not have the midrange/midwoofer throw off the frequency response of the tweeter.

 

[MattHooper]

I'm mentioned this before but...

I've found Jim Thiel's last coax-design speakers to be just about the most coherent sounding speakers I've heard. The sense of a lack of any transition points between drivers - I don't recall hearing better in that regard.

 

[HooStat]

Coaxials have particular advantages in center channel applications. However, there are equally rare there.

 

[sigbergaudio]

Emailing Genelec asking about disadvantages, the only thing that seems to be true anymore is that you can't get a massive magnet for a larger high SPL tweeter to fit, so for main monitors it's not as useful.

Not sure if that's true either? This is 50cm, so 111dB means 105dB@1m per speaker (111dB for two) and around 1% THD (mostly 2nd harmonic). This is a coax tweeter. I think it would comfortably play louder than you'd like even as a main monitor.

 

[HooStat]

Also, ME Geithain has a different approach to coaxial speakers, with drivers in front of other drivers. https://www.me-geithain.de/en/

 

[Sancus]

Coaxials have particular advantages in center channel applications. However, there are equally rare there.

Yeah, but centers are usually afterthoughts and even when they're not, they still need to match dispersion and FR as much as possible with the L/R otherwise they'll sound wrong(this was even studied). Designing a coaxial is already very challenging as shown by the more poorly executed designs we've seen, nevermind designing one that will work well with a separate non-coaxial design.

 

[stevenswall]

Not sure if that's true either? This is 50cm, so 111dB means 105dB@1m per speaker (111dB for two) and around 1% THD (mostly 2nd harmonic). This is a coax tweeter. I think it would comfortably play louder than you'd like even as a main monitor.

Personally, sure, it would likely be enough as all of my speakers go too loud for me. Are there measurements for pushing it to 120dB? The "JBL M2 is more 'dynamic', high SPL speakers sound better" crowd would probably consider 120dB almost loud enough if there were measurements of that.

The Genelec 1236 would be at 133dB at one meter with two of them, which should sound twice as loud, then twice as loud again. Not sure they could get that with one of their coaxial drivers, and if they used multiple there might be weird lobeing or beaming (which seems to happen with Tekton beaming a lot with the multiple tweeter models.)

 

[sigbergaudio]

Personally, sure, it would likely be enough as all of my speakers go too loud for me. Are there measurements for pushing it to 120dB? The "JBL M2 is more 'dynamic', high SPL speakers sound better" crowd would probably consider 120dB almost loud enough if there were measurements of that.

The Genelec 1236 would be at 133dB at one meter with two of them, which should sound twice as loud, then twice as loud again. Not sure they could get that with one of their coaxial drivers, and if they used multiple there might be weird lobeing or beaming (which seems to happen with Tekton beaming a lot with the multiple tweeter models.)

Not yet, but we're going to start prototyping a loudspeaker with a 12" woofer combined with this coax driver soon, then it will make sense to drive it higher. Not to 133dB though, that's beyond the intended application of anything we're building.

Here's an in-room measurement roughly 3 meters away (two speakers). We've been playing 110dB+ (continuous) music material with no audible compression whatsoever.

 

[Koeitje]

if you build the entire speaker out of compression drivers it's not far fetched at all.

Edit: I would love to put that bad boy on a Klippel but i live in Europe.

View attachment 155912

View attachment 155913

Not at a 100dB and that is not subbass. -3dB point for those speakers is at 70-80hz or something.

 

[mhardy6647]

I don't think they're rare at all; indeed two of the late Art Dudley's "speakers to hear before you die" are coaxes (Altec Duplex and RCA LC-1A, both of which are truly outstanding loudspeakers relative to my taste).

I have ahem a modest but nontrivial collection of coaxes, come to think of it.

604E by Mark Hardy, on Flickr

(sorry I didn't dust this 604E Duplex before I photographed it)

 

[abdo123]

I don't think they're rare at all; indeed two of the late Art Dudley's "speakers to hear before you die" are coaxes (Altec Duplex and RCA LC-1A, both of which are truly outstanding loudspeakers relative to my taste).

I have ahem a modest but nontrivial collection of coaxes, come to think of it.

604E by Mark Hardy, on Flickr

(sorry I didn't dust this 604E Duplex before I photographed it)

is the coax still considered a coax if the woofer didn't act the waveguide of the tweeter?

 

[mhardy6647]

is the coax still considered a coax if the woofer didn't act the waveguide of the tweeter?

Well, it certainly was for five-ish decades. The shared axis of the treble and low frequency drivers was/is referred to as coaxial.
That's all I've got.

That said, the classic Tannoy drivers would meet your criterion -- also very nice reproducers.

005 by Mark Hardy, on Flickr
016 by Mark Hardy, on Flickr

 

[dougi]

I think they are hard to engineer well. I have Elipson Planet Ls which use a Seas coaxial. Below are quick plots (0.5m not gated) which shows on axis suckout around 10kHz. Good off axis.

 

[thewas]

As some might know by now I like good coaxial designs and have owned a few as I like their advantages, there is one thing though that is easier to implement with non coaxial drivers, that is different horizontal (usually wide) and vertical (usually narrow) directivity which can be advantageous at some listening configurations. On the other hand you can do such with good pseudo coaxial configurations like below one, which are not easy or cheap though:

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[Newman]

Asking why are they rare and asking if they have any downsides is a completely different thing

Only if thread proliferation is your thing.

 

[ernestcarl]

A few of the last photos I took (can't quite undo my last little "experiment" unfortunately) of the S8:

Fully sealed and applied some extra damping to the boxes to reduce any ever slightly remaining "tubbiness" (edit: I think I mean the opposite?) in the bass.

These are a bit "bright" off-axis so cuts between 6-11kHz or the more general -1.5 dB HF shelf needs to be applied. With the HF equalized -- with mainly negative gain only -- similarly to the KH120s (in the same room), the S8 are by far much less fatiguing to my ears.

*Turns out one can actually rotate these if to be used as a center channel speaker.

 

[antennaguru]

Back in the 1970s Jensen Co-Axial 6" X 9" speakers were often installed in aftermarket "upgrade" car stereo systems. They were installed on the rear shelf of sedans using the trunk space as a large enclosure volume. Jensen also made a more expensive "Tri-Axial" model with an even bigger plate holding a Midrange and a Tweeter. However, Jensen's top of the line automotive speaker "system" consisted of 6 separate speakers: pairs of Woofers, Midranges, and Tweeters. They were all discrete drivers so more creative installation work was required than just using the generally standard OEM 6 X 9 rear shelf holes, but they sounded a lot better than the Co-Axials and Tri-Axials. Jensen was a leader in car audio speakers back then.

I had a part time job in the summers when I was in school, when I wasn't working at my primary summer job, working for a shop installing car audio systems and two-way radios, so I heard all sorts of car audio systems. In my own car I had the cheaper Jensen Dual-Cone Woofers on the rear shelf (they had Whizzer cones) and a separate pair of tweeters installed high on the driver and passenger doors. The tweeters were non-automotive tweeters from my side business building largish bookshelf bass reflex home stereo speakers...

 

[jhaider]

KEF made the first Uni-Q driver in 1988, it took a lot of time and effort for them to 'perfect' it to the way it is in the KEF LS50 Meta. And even now, hell breaks loose the moment you make the woofer bigger than 5.5 inches so you're limited in headroom.

Actually, the 8” UniQ from the old Q900 is a fantastic coax. The speaker itself had a crossover a little too simplistic for the driver, but tame the woofer breakup notch and you can get really good sound from it.

 

[tecnogadget]

When it comes to “pinpoint” imaging there is nothing a coaxial can accomplish that a discrete driver loudspeaker cannot.

Regarding pinpoint imaging, better overall directivity, specially in the vertical plane, plus time aligned tweeter/midrange voice coil meaning better step response...I'm sure you could find a few examples of well engineered discrete drivers speakers that accomplish this...but the list of measured speakers by Amir is accessible to anybody and tells a different story when looking at the bigger picture...

 

[antennaguru]

Regarding pinpoint imaging, better overall directivity, specially in the vertical plane, plus time aligned tweeter/midrange voice coil meaning better step response...I'm sure you could find a few examples of well engineered discrete drivers speakers that accomplish this...but the list of measured speakers by Amir is accessible to anybody and tells a different story when looking at the bigger picture...

Vertical directivity isn't actually all that critical when you're seated in the hot seat listening to two speaker stereo music, unless you suddenly get up from your seat to stand up. There are quite more than "a few examples" of loudspeakers with discrete drivers that deliver pinpoint imaging. I for one have owned many, including ones I have designed and built.