Originally Posted by FOH
You can't compare like this, ie., an IB to small-sealed comparo. Due to the way sealed box mimics a HP, and how the amp power comes into play, it's just different. Will it matter here, no, not really. Because either config got you the clean SPL you wanted. For my money however, there are other considerations too.
For example, the eD drivers were so very small in diameter, I think you notice a higher quality sound with a more linearized inductance,..as 8 of these will not encounter the excursion the drastically smaller drivers were seeing. Also, the wave-launch will be more purely executed into the space with the baffle wall. Your box subs had acoustic energy leaving the cone, both launching forward, and hitting the wall behind, then launching forward ... thus some summation less than optimally with regard to phase response at the top end of their coverage. This is critical due to blending optimization with mains, etc. It'll just be a more optimal wave-launch wrt time/impulse, phase integrity etc.
Unfortunately you will not have the theoretical ideal infinite backspace. But as far as latent backspace energy encountering the cone, they'll have a fighting chance if you damp the hell out of the volume with fluffy.
This is nice, the lack of structural moans and groans.
Once properly blended, etc, I'd bet it'll be better. Aside from the latent energy component, the more idealized acoustic transfer and wave-launch at the top end of the subs range should allow this iteration to shine a bit better than before. Also, those little eD drivers are beastly, but compression will be less an issue here for two reasons; dramatically more swept area, and dramatically more sensitivity in the bottom octaves.
I disagree with most all of the IB hype I've read over the centuries.
Here are excerpts from one of the flowery IB advocate speech writers:
The absence of distortion from the IB allows the fundamental to be clearly exposed rather than obscured by false harmonics. No single low frequency tone is ever involved in the reproduction of sound so the false harmonics (of other subwoofers) are as complex as the input signal itself.
The unwanted and artificial hash produced by most subwoofers has its own frequency response and phase superimposed on the speaker's output. The greater the clarity of the subwoofer the greater the sense of realism because nothing is added which wasn't in the original signal.
If any proof were needed of the IB's greater clarity, realism and low distortion then one only needs to listen to the great pipes of the organ being reproduced.
Wow. It would certainly be boffo to see some measurements of an IB that even approach proving this sort of wild claim, which is, sad to say, typical of the IB hype I've read over the years.
All of the Fi drivers that have been measured to date show very high inductance, just as you would suspect they might. The IB has more VC than those that have been measured (and used in small boxes by myself) and no additions to counter the inductance, so the conclusion must be that it has the highest inductance of all of the Fi drivers.
The size of the box the IB3-18s are placed in has zero effect on the roll off or harmonics that result from high inductance, thus, it's crossover region sonic signature will be unaffected by placing them in an IB vs an in-room closed box.
"Will it matter, here, no, not really." <===This is the part I agree with.
I've posted in the past that inductance problems are easily overcome, but the point is that they aren't overcome by increasing the size of the box.
What we hear is frequency response. Group delay, phase and the majority of harmonic distortion are derived from the FR in-room. Match the FR and there is no audible difference, much less anything near what is being described by the IB-ers.
Compression is the result of poor design, the size of the box being irrelevant. Push any sub beyond is normal operating parameters and it will compress.
8 x 18" driven by 14KW burst power in 2000 cubes is the key design here. Box size makes no difference.
Sensitivity resulting from box size is a see-saw. Increase box volume and the low end is easier to drive to Xmax, but the top end will never reach its potential for lack of available power. Increase available power for the top end and the low end will be driven beyond Xmax. If limiters are employed to remedy the situation, compression is the result. If HPF is employed to remedy the situation, FR (thus, BW, GD and everything derived from FR) suffers and 'more realism' disappears.
That leaves 2 choices; a) Decrease box volume or b) Increase displacement/power handling.
The choice for most IB-ers is add displacement. Good choice, as it is for any system.
Since we hear FR mores than any other parameter, having placement options is a big. Even if one takes the time to painstakingly locate the IB manifold, there's an assumption that the room acoustics will never change (furniture, furniture layout, monitor type/size, hardware rack, flooring, seat position, etc.) or the type, size and parameters of the driver compliment and that those optimal manifold locations are logistically possible.
I'm sure James will like the result. Fi drivers are well designed and built for the $$ and the inductance will not be an audible problem, in the final analysis.
Another important parameter for proper in-room FR is the signal being fed to the drivers. James has recently changed pre/pros and noticed an immediate improvement, but, like most everyone who posts in this forum, fails to measure the signal chain response. I hope he does instead of the usual blame being placed on some other part of the equation.
Here's a simple guide to how to do that for anyone interested: