Grant Bunter wrote: ↑Mon Mar 22, 2021 2:42 am
If money is no object, and you can get them, in a T48 the 15" driver with the greatest displacement voltage limit (you'll get used to that term), and hence the greatest output, is the 18Sound 15NLW 9300
Now that you mention it, I seem to recall a conversation about the 18Sound 15NLW9300 and Bill saying that they measure and rate their Xmax in a way that is conservative compared to how Eminence rates their drivers. And with an 80 volt limit, all else being equal, could/should have about a 2.5dB advantage in maximum output over the 3015LF.
Singtall,
To put that into perspective, perceived volume is somewhat subjective. Each person has a different perception of what double or half a given volume is. What's generally accepted as twice as loud is a10dB measured increase. 1dB is a perceivable increase when playing single tones and comparing A:B, but not so easily perceptible in listening to actual musical content. A crowd isn't likely to notice if you increase or decrease the PA's output by 1dB in the middle of a song. Where a 3dB change would likely be noticed by some, depending on how abruptly the change was made.
To achieve a 3dB increase, it takes twice the power. +6dB 4x the power, 9dB = 8x
A 10dB increase requires 10x the power
A 13dB increase requires 20x the power
A 20dB increase requires 100x the power
A 23dB increase requires 200 x the power
A 30dB increase requires 1000 x the power
A 33dB increase requires 2000 x the power
36dB... 4000 x the power... And so on... If your starting figure was one watt and you wanted a 39dB increase, it would take 8000 watts.
Every doubling of cab count gives you an increase of 6dB (generalized breakdown; +3dB for doubling the radiating plane area and +3dB for doubling the system power)
For instance, if you built 24" wide, 3015LF loaded, T48's you'd have the following result for one, 2, 4, and 8 cabs... at 1, 2, 4, and 8 watts total system power, measured at a distance of 1 meter outdoors.
Some people like to look at the average sensitivity, but I prefer to base my calculations on the point of the lowest sensitivity within the target bandwidth. Between 40Hz and 125Hz, the lowest point is 40Hz. So, that's what I base everything on. Whether you EQ your system flat or with a boost on the bottom end, it's that frequency that will limit the overall volume your system can attain without engaging the limiter. That assumes you're actually playing content that low. If you're not DI-ing your bass player and just mic-ing his cab, chances are there's not going to be much down there anyway, which potentially means you can get more out of the complete system, at the expense of not fully utilizing what the cab is capable of... Which then leads into a conversation of using the T39, which in my experience is very worthy of covering your needs as well, even with DI'd bass guitar. But, that's another conversation.
Anyway, back to the point...
Cabs are typically measured at one watt at a distance of one meter (3.3 feet) in half-space unless otherwise noted. Half-space is typical outdoor conditions where there are no boundaries to the propagation of soundwaves other than the ground (picture outer space kind of space, with a floor so sound energy can't propagate downwards). For every doubling of cabs you get +6dB. For every doubling of distance you get a -6dB reduction in volume. Indoors, with the mouth of the sub aimed at a wall +6dB (requires half the amount of cabs as outdoors for to create same output(or the same amount of cabs but at 25% of the required outdoor power)), indoors aimed in a corner +12dB.
Putting all this together, you can calculate your actual cab count and power needs for a given venue and whether or not you think the additional 2.5dB premium the 18Sound driver offers is worth the additional cost of the drivers as well as the additional cost of the amps to drive them (800 watts per cab with the 18Sound driver vs. 450 with the 3015LF). 4 cabs is 3200wats to get only 2.5dB more output than 1800 watts with the 3015LF drivers. That's a lot of amplifier money for 2.5dB. But, if your pack space is more limited than your cash, it could make sense.
Just to clarify, that 2.5dB is not cumulative. It's
not +2.5dB per cab, +10dB for 4. It's +2.5dB no matter how many cabs you use, period.
4 24" cabs penciled out assuming a wood cost of $100 per cab looks like this...
Wood, 18Sound drivers, 800wpc amp = roughly $4000 (give or take) for a maximum output of 138dB at 40Hz at 1M outdoors.
Wood, 3015LF drivers, 450wpc amp = a little below $2000 for a maximum output of 135.5dB at 40Hz at 1M outdoors.
Add a v-plate? Add 3dB to that figure for an extra $30.