Just how big is that driver?

Unsound
Good point.

Truth in advertising is important too... "Whose truth" looks more and more like the real question.

Exactly, and many drivers are made outside of the USA. So as long as US manufactures feel the need to simplify things for their US customers, there a chance that the integrity of specs might be compromised.

Unsound...The world is metric...except for the USA and Fiji

Just a guess here, but, I wonder if some round up or down drivers made to metric proportions.

Gawdbless

Is this a 'never mind the quality, feel the width' sort of question?

No.

I’m in fact wondering where the truth is for one, and why such disparity exists in this ‘plain to see’ facet of the audio industry.

One can argue much about claimed parameters of just about any audio component. Are tube watts indeed superior to solid state watts? What’s the true maximum output of a 300B tube? How was that SPL number arrived at? …. And likewise, impedances, and sensitivity?

But how on earth can any despairity, difference, in critical or even subjective terms, alter a simple ruled result? It’s misleading and undermines consumer confidences. IMO

On one hand, I feel the driver has to be considered the whole of the active sound producing unit. The cage, voice coil, surround, magnet, vibrating element or diaphragm… the whole enchilada… the part that fills the hole in the cabinet.

On the other though, with such often made references to the type of cone materials being used, paper, reinforced this & that’s, Kevlar, titainium, aluminum, coated such & such alloys; it’s only that portion moving the air itself. In short, the part we can actually see working.

Years ago, when one speaker maker said they used a six inch midrange driver, you could count on it being six inches across the paper cone itself. I see that no longer being so much the standard and simply wondered “how come dat is?”

I must have missed that memo.

I have noticed the JM lab drivers are fairly accurate if you account tor the surround. If you add the frame then it doesn't work out so neatly.
The hole in the cabinet may only accomodate the basket spider and magnet assemblies with the whole shebang held securely in place by virtue of a mounting ring which must rest on the baffle. Since this is very variable from one manufacturer to another I would not consider it a meaningful measure.
It is generally not helpful at all to concern oneself with the size of the driver. I do not know pro applications and it may be relevent in big spaces. My 15 inch woofered speakers do not have the bass that my double 8 inch speakers does so again it boils down to a great many parameters working in concert. Uless you want to argue that 2 x 8 = 16" but in all seriousness the reactivity the resistance to movement as well as piston speed = magnet and voice coils along with cabinet geometry all make a big difference.
Its not important when considering a bass transducer. My current drivers are speced to a low of 30 cycles but I lived quite happily with others that made no claim below 50 and were falling fast below 80. Because that is where the music- my music - anyway lives. Save the rumble for HT please.

Is this a 'never mind the quality, feel the width' sort of question?

I am serious. IMHO, equipment should as much accurate specs as possible. This should help consumers narrow down the compatibility options.

The sub I have is sold as 12", which is the size of the mounting hole, so the size of the driver is a bit smaller.

I'm 5'10" but think I'm taller!

That is why women can't park their cars because we tell them 6 inches is really 12!

Nobody ever made a rule I guess that the size stated of a driver is of the cone alone(or cone and attached surround), most seem to think as a logical assumption the measurement provided is of the actual cone surface area, but it is instead of the Driver's entire assembly, which seems to coincide pretty consistentley with first hand experience shown here by the examples above.

I just happen to have a NHT 1259 "12" Woofer on hand.

Overall dimension..310mm which is 12.24 inches
Mounting hole......281mm which is 11.06 inches
Cone diameter.........................9 inches

Unsound
Well, yes, and no.

I'm serious as to the figures a maker uses for the products they sell which have other makers drivers in them.... Why should a given driver's specified dimensions then differ from those of the provider of the driver being used in the first place?

For example, If I go about building speaker systems... and am able to buy for instance, drivers from Vortex for ex., and Vortex says the drivers I want to use are 9inch, 5inch, and 1 inch drivers, should I be then compelled to say the Drivers in my speaker system are 10 inch, 6 inch and 1 inch?

Or merely pass along the orig drivers specs? this latter approach seems prudent and wise.

Unsound, are you serious?

Blindjim, are your serious? If so, I couldn't disagree more.

This is a good quest as my Silverline Audio SR-11s have a woofer specified at 4" while my Usher S-520's woofer is specified at 5". Why do I mention this? I've measured the woofers in both speakers and the Silverline woofer is actually bigger. They are both very close to 5 inches if the driver's frame is taken into account.

Most 10" drivers are at the outer most part of the frame measured(a bit deceiving for sure), normally the surround and cone make up only about 8.75" to 9" of it actually. And yeah they still consider them 10's commercially.. some european drivers these days seem to fess up and call them 9" drivers instead.

There is a high degree of variability in how specs are measured as well, which is why audiophile types generally prefer their ears over measured specs. Otherwise, everything that measures the same should behave the same and sound the same.

Tolerancess for connectors are also a bit loose which is why some bananas are, well, loose.

it's always refreshing to have exacting standards being employed in such an esoteric and affluent market, huh?

Spec sheets should only contain info on color, weight, size, and perhaps price. Everthing else is subjective apparently.

Size of the hole cutout in the enclosure.

For cone drivers, size may be the outside diameter of the frame, the diameter of the surround, or the diameter of the cone.