Bass Driver Size - how much better is an extra inch?

@emergingsoul --

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Not sure why driver sizes tend to be smaller these days unless you pay a lot more.

Indeed, a lot more; size is progressively expensive in hi-fi, not to mention high-end, and for physics to be more closely approximated - taking a small, already expensive package and making it into a bigger one - it’s an expenditure eventually only the very few can accommodate. A shame really obsessing about painting that little corner of the canvas in the most minute of detail, when the rest of it, its sheer scale and totality, is neglected. That is, at least when one knows what’s missing.

Smaller size is by and large about convenience/practical considerations/interior decoration and spousal acceptance, from where effort is often invested to make it appear as if the smaller package is actually a desirable trait, or one overall sufficient sonically (some justification is obviously sought into buying small-ish products that expensive, or even less expensive). And who wants to pay $1,000 for a measly sound bar? Many, it seems; they’re selling like warm bread - go figure.

I’m not trying to negate the potential prowess of small(er) speakers in smaller spaces, but it’s when smaller sized speakers become excessively expensive that bothers me, because vital aspects of the sound only achieved thorough an adherence to physics (i.e.: sheer displacement area, high sensitivity, etc.), important to me, are still sorely missing. Why then bother, and at that price? 

Simplicity topologically (and what it in-effect leads to) is something to aspire to, a trait with smaller speakers in particular, but it’s likely a side effect of a purchase incentive here that’s not always consciously sought to begin with, at least not as much as seeking smaller size per se. Holding on to that trait, however - and for good reason, I’d claim - the question could be how to scale up in size without throwing out the baby with the bathwater, and I’m thinking mostly complexity and price here. It’s certainly possible to achieve, I might add, but not through the package one would usually expect, while also needing a healthy dose of change in mentality towards sound reproduction in a home environment.

@cd318 --

Horn loading like your Klipsch Cornwall’s will result in a different bass sound than ported designs which will sound different to sealed boxes.

The Cornwall’s 15" bass driver is ported. The sibling La Scala’s on the other hand are using a 15"-loaded folded bass horn, and yes that’s certainly a different bass presentation vs. a ported, or even a direct radiating sealed design.

@cd318 --

I rather suspected that my front ported Tannoy Berkeley’s didn’t go down that far despite their 15 inch drivers.

According to one site their frequency response is 35Hz - 20kHz. I strongly suspect that it barely scrapes 35Hz let alone being flat.

Come to think of it, wouldn’t FR stats be far more meaningful if they showed only the flat range, as opposed to -2db down or even worse?

Extension downwards is about the relation of bass driver size to enclosure volume (or horn path length in a bass horn) - unless we’re talking EQ’d sealed designs - and those Tannoy’s, from the looks of ’em, would seem to accommodate the response you point to - certainly in-room.

More important than extension per se is how they come about the bass that is, and I would expect it to be very satisfying here. Big paper coned woofers of at least 15" has a tuneful way with the lower frequencies that smaller units in multiples can’t replicate, and with the proper driver type (for this particular context at 15") they’re very good into the central midrange as well (though 900-1kHz is about as far as they get, I’d say), as you’ve no doubt come to experience with your Tannoy’s. Though, this would seem to go contrary to audiophile "wisdom" with the mention of beaming, cone break-ups, etc. My counter reply: try it out with actual listening, and if it isn’t one’s cup of tea - fair enough.

Regarding FR stats: Insofar the specs are trustworthy to begin with I suppose an -xdB number is meaningful in the sense of indicating the useful frequency extension, which goes beyond flat response and not least with the interaction of the listening room. I don’t really care about the bass stats of main speakers; listening will do the talking here, and in any case I’d by inclined to high-pass them in the bass, actively, for subs augmentation. Extension stats (or rather: tune/lower knee) for subs is another matter though, as this is specifically dealt with and important in the DIY designs I’m interesting in and use.

@steve59 --

All things being equal there’s no replacement for displacement...But use the sportbike analogy and the experienced will say smaller and lighter is better on a tight track.

The problem with analogies is finding the ones that apply properly and illuminates a matter. Given proportionately stronger motor force a larger diameter driver will see no lack of nimbleness compared to a smaller unit, within the constraints given re: upper frequency bandwidth dictated with the use of bigger cones. Moreover added surface area AND better efficiency to boot equals less inertia build-up in the moving system via less cone movement, not to mention the benefits of a surplus in headroom with all that entails in regards to lower distortion and minimizing thermal compression.

It’s also worth keeping in mind there are 5" woofers and 12" midranges; a smaller diameter low efficiency woofer in a 2-way system acting as well as a midrange isn’t necessarily the last word in performance prowess in its upper range (nor in the bass for that matter), whereas a suitable 12" or even a 15" high efficiency unit can do very well into the lower to central mids, not least when high-passed below 80-100Hz - something that would turn these drivers into "mitten raketen," as they say in German (i.e.: midrange rockets).

Even though bigger units are limited in regards to upper band frequency response they can be properly met within their safer operating range (typically between 500-1kHz) with a compression fitted to a horn/waveguide, something a dome tweeter would never be able to achieve unless mounted to a waveguide; the power response in the cross-over region between a dome tweeter and a woofer/midrange isn’t ideal, to say the least, something that can be attained quite successfully with the use of a waveguide/horn crossing over from a larger woofer/midrange - all in the name of a more (energy) coherent presentation.

My old fischers with 15’’ woofers would allow me to feel the air pressure in the radio studio move when the door opened and I’ve never experienced that from any other design, but I could also watch that paper driver flex and distort its shape when playing music. To make a 15’’ woofer that’s as rigid as a 6.5? is it even possible.

This should be relative to what I outlined above.