Originally Posted by
FOH 
Powering up Fi IB3-18's all depends on your ultimate configuration.
If you go all out and build the two manifolds with four IB3-18's each, then I'd buy two Behringer EP4000's, and series two drivers per channel. This will allow worry free operation, and ample output. Unless there's been a significant change to the design, the IB3-18's possess a nasty hard bottom characteristic if fed too much power at too low a frequency.
Unless you opt for a high pass filter,....which is somewhat counter intuitive with an IB, I'd limit the per driver power to about 300 watts. I've tested them extensively, and determined 500 watts per driver will hard bottom with big LFE transients. At an operational level of 225 watts per driver, there's no over-excursion issues with HT material. It's the deep, deep stuff that plunges them into trouble. They're so efficient in the bottom octaves that even at 225 watts per driver is ample to hit extreme levels, yet avoid a bottoming scenario.
An EP4000 would allow you to either operate at 500 watts each in a bridged, series/parallel config, ... or 225 watts each in a series config. This way you can perform your own bottoming testing and determine for yourself. Perhaps there's been a change I'm not aware of in the construction clearances of the former hitting the back plate etc,. I'm not aware of any however, who knows.
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Behringer (1)EP4000, (4) Fi IB3-18" 4ohm
Stereo;
8 ohm stereo=450w
Scenario #1.) 225w / driver (very stable @-4db Pmax)
4 ohm stereo=635w
2 ohm stereo=815w
Scenario #2.) 407w / driver (less stable @ -1db Pmax)
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Mono;
8 ohm mono=1336w
4 ohm mono=2000w
Scenario #3.) 500w / driver (stable @ Pmax)
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You'll be able to achieve acoustic output in the mid 120's (~125dB) out of each four driver manifold, this is even at the safe operational point of 225 watts per driver @1m@20hz. So summing two manifolds would hit +6dB higher, or 130dB or somewhat above.
A brief overview of IB powering;
With an IB, the conundrum always exists of how to implement your amplification structure. Without the typical small sealed air spring to lean on, the system is excursion limited, instead of thermally limited. When examining the small sealed, and IB, the IB's inherent advantage in is the native efficiency in the bottom octaves, all due to the driver having no air spring to lean on. When powering an IB, much less power is required to achieve X-max, than in a small sealed.
*So one must make decisions on determining the use of a less powerful amplifier, thereby limiting capability in the upper frequencies,.... or employ a more powerful approach to achieve full capability in the upper frequencies, however implement high pass protection to assure over excursions aren't an issue in the bottom octaves.
In the small sealed application, the entire potential of the amplifier is availed for frequencies both
above, and below the knee. With the IB, the ULF excursion will be the limiting factor. If you hi-passed the IB, things would equal out with more power now made available through the mid and upper subwoofer frequencies. But operating without a high pass filter, the power amount at which the driver hits it's Xmax is the limit,....so it's somewhat limited in the upper range. This is why proper IB systems have huge amount of displacement, via multiple drivers.
The Behringer EP4000 amps are well vetted, they have enough extension in the frequency response for IB duty, and as long as you don't operate into 2 ohm loads, or alter the thermal handling characteristics, they are an outright steal and should serve you well for years. In stereo 8ohm config, they'll draw less 10 amps each, even at ULF test tones, so instantaneous voltage drop concerns aren't a prohibitive issue if the circuit lengths aren't excessive. Typical operational levels of current draw would be much less.
Do you have any floor-plan drawings/pics?
Thanks
). The guys at Elemental Designs are in the process of building them now. The front three are upgraded versions of the cinema 12 with dual 12s and upgraded CD. The surrounds, rears and heights are single 12s upgraded CD as well. The are in the neighborhood fo 100db sensative witht he upgrades, so hopefully the will rip right along with the subs.
. Welcome to the dark side.
