I've often wondered about the real value of a large Xmax.
Manufacturers research cone data and use materials with best results. I suspect paper is superior to rubber. When it comes to small sub drivers there is often a large area of surround and very little actual diaphragm. The small membrane size possible accounts for the low sensitivity of these drivers. But has anybody considered the quality of these drivers? Rubber / Neoprene / Foam are probably not producing representative sounds.
Manufacturers research cone data and use materials with best results. I suspect paper is superior to rubber. When it comes to small sub drivers there is often a large area of surround and very little actual diaphragm. The small membrane size possible accounts for the low sensitivity of these drivers. But has anybody considered the quality of these drivers? Rubber / Neoprene / Foam are probably not producing representative sounds.
I have a mantra for good bass: Move a Lot of Air - GENTLY!
Any drivers, particularly small ones, flapping around at high excursions have never impressed me, so huge Xmax numbers interest me not one iota. Take a look at slo-mo videos of car speaker suspensions at absurd excursions to realise that this is not a means of accurately producing LF. Added to this is the improved acoustic impedance matching to the surrounding air which comes with large cone area, and small cones see yet another disadvantage. Generally they are a waste of time and money if trying to reproduce LF with fidelity and efficiency at any kind of worthwhile level.
Any drivers, particularly small ones, flapping around at high excursions have never impressed me, so huge Xmax numbers interest me not one iota. Take a look at slo-mo videos of car speaker suspensions at absurd excursions to realise that this is not a means of accurately producing LF. Added to this is the improved acoustic impedance matching to the surrounding air which comes with large cone area, and small cones see yet another disadvantage. Generally they are a waste of time and money if trying to reproduce LF with fidelity and efficiency at any kind of worthwhile level.
So this is better then
https://www.precision-devices.com/products/all-products/pd-24603br/
https://www.precision-devices.com/products/all-products/pd-24603br/
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Like the rest of the undereducated public I probably would understand a Purifi white paper. However, in balancing efficiency and output there must be a general "bore x stroke" golden ratio?
e.g. This driver has a dust cap and surround but virtually no diaphragm.
https://www.soundimports.eu/en/tang-band-w5-1138smf.html
For performance, distortion, and cost i would rather go for 3 x 15" drivers. More area, better control of the membrane.
thing is that PA speaker are rolled out with just one or 2 drivers
you seldom see 3 or 4 driver units in commercial PA speakers,
i mean subs
you seldom see 3 or 4 driver units in commercial PA speakers,
i mean subs
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Overkill for home hifi, but yes, in terms of physics, and likely to give better performance. A large cone barely moving generally gives better bass than a small one moving violently.
PA speakers are generally packaged to be easily transportable and used in stacks if required so single, huge, multiple driver single boxes are rare.
A really good smaller driver might well sound better than a poor quality larger one, but all other things being equal, lower cone excursion is usually a good thing. More important is not expecting a speaker to properly reproduce frequencies up to, say, 1kHz whilst also dealing with high-excursion LF signals. Cost and size are the most usual factors precluding the use of properly sized low frequency drivers in a domestic setting, plus the fact that for some unknown reason many folks still seem unable to consider using PA drivers for home hifi.
Traditionally PA drivers were designed focussing on different criteria. A Peavey 12" Black Widow, for example, didn't do well below 50Hz but created an exception SPL and was virtually indestructible. The 15" Fane Colossus offered similar specs, none of these drivers were particularly adept at sub-bass. A recall RCL offered a 12" driver - good down to 30hz. But like and F1 engine, after a couple of hours at full power the Grim Reaper received a work order.
Any single 12" driver can never reproduce sub bass at high level for any length of time, it's just not got the cone area and is really a midrange in the PA world.
The dust cap counts as diaphragm, because it is rigid and moves with the diaphragm.
You sound like the proprietor of my local reggae sound system. He maintained 12" drivers were only good enough for headphones.
I think dust cap counts as diaphragm and it moves with the diaphragm
That's a bit of a cop out . . . The brochure's telling you the cone is manufactured from high-quality super-efficient Propex polypropylene when really a concave 160gsm card disc is doing most of the work.
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AFAIK the low sensitivity comes from more of the voice coil being out of the magnet gap for more of the time on a high-excursion driver (and the higher mass of a small diaphragm having to be quite heavy to reproduce low frequencies). I don't believe there is any link between diaphragm material and efficiency (assuming equal shape and mass).
Yes and no. It's just not very 'good' diaphragm. If you search this forum you'll find a discussion on whether or not a driver's performance is impacted by the removal of a dust cap. But in the instance of small subwoofers some are virtually all dust cap.