24" drivers

Sorry Elliot, I am well aware that headphones are loudspeakers, I prefer to feel my bass though! 

Forgot to say with 15mm Xmax suspension you got left 5^2 cm of Sd left

Crashpc wrote: Picking smaller excursion of the smaller driver doesn't make much sense, as the larger driver can stay in smaller excursiona too. That's no advantage of the smaller driver. Actially larger excursion driver has better potential to stay linear in higher excursion. Coil to cone ratio is fair note, but doesn't set absolute values. The idea of many drivers in one box is interesting, but we're not there - in the age of picking it over larger drivers.

Edited by 70,s hero - 23 February 2017 at 10:20am

Oh well image didnt post, was 8x10 bass cab

Edited by 70,s hero - 23 February 2017 at 11:09am

70,s hero wrote: Consider that, most 18" drivers are not very linear at all due to the high xmax required.A larger driver can stay at small excursion however the requirement is for it to produce sound pressure levels at the optimum amount which takes it out of any linear characteristics that it may have. The same sound pressure levels can be achieved with smaller multiple drivers but with a more linear result due to the ability of the voice coil to remain at its optimum efficiency (within the field). Think of this..the motor is essentially two magnetic fields one fixed and one created by the VC.the point at which non linear characteristics are introduced is when (given a single frequency) of say 30HZ is when the VC starts to leave the most intense part of the fixed magnetic field. This is a characteristic of most high powered 18 drivers where normal excursion produces variations in EMF within the motor that contribute to the non linear response or distortion. The cone flexing and power compression are also issues that smaller drivers suffer from less.

That looks very irrelevant to me. We´re looking at particular outcome. I.E. Linearity, excursion, displacement. Not at the datasheet data. There is no hard set higher requirement for 21" or 18" to have larger Xmax than what 12" drivers have. But while it HAS, it will work in more linear fashion under Xmas, while 12" driver would have to be AT its Xmax for the same output.
I.E.: 21DS115 has 36mm long voice coil and 14mm top plate. That is pure mathematical 11mm of old-school Xmax, where the coil doesn´t leave the gap. I note, that it is deep and thick gap, to use it later.
Then there is 12NW100 and 12TBX100 in the B&C line, which has 25mm long voice coil and 12mm thick pole pieces. That is 6,5mm of mathematical Xmax.  For the 21DS115, that excursion is significantly under its Xmax. I would not hesitate to say fully 2x. In that excursion, the 21DS115 will work in more linear fashion than group of 12"s. Also, the thicker the pole piece, the less distortion you have at, or past this Xmax, beccause less % of the gap is unused when you go lets say 2mm past Xmax. For example for 4mm pole piece, it is half of its thickness. Serious distortion. For 14mm pole piece, it is under 15%.  So for the linearity and displacement, larger speakers with larger possible excursions usually have the edge.
The idea of more voice coils is cool, but it doesn´t deliver yet. Only if you have serious money, and you put more drivers in the box, so the sd area is larger. Then it is superior.

A little off topic but does any manufacturer spec xmax correctly other than BMS?? Everyone else seems to add a varying degree of 'fudge' factor..