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SteveCallas wrote:
 My modeling for the ported version was done with 2600 watts, creating a max port velocity of 33m/s just below 11hz (are you using 70 cubic feet?). |
Yes, 70 cu ft, four 6" x 26" ports. With 2600 watts, peak port velocity is ~46.7 m/s at ~10.7 Hz. Which of us has his simulation wrong?
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If you knock power down to 1500 watts, speed stays under 26m/s at all frequencies and max output is still 120db+. Including room gain, I highly doubt he will ever come close to using much more than 1500 watts down that low. That said, I did advise to use fewer larger ports, - two 10" looks great - but Rodny wanted to stick with 6".
I gotta disagree with you on the highpass Ilkka. Much higher tuned LLTs with significantly less output capability have yet to bottom with the lowest bass scenes played at near reference levels, so I see no reason to change course. Excursion demands beyond xmech should tie in pretty closely to his ultimate electronics rolloff, keeping him plenty safe.....and again, I don't really foresee too much 120db prior to room gain output coming into play that low  |
I knew you were going to say this.
But whether 120 dB etc. is enough for his needs isn't the point. This is about how much SPL can each system (SLLT/IB) output before exceeding some specific excursion (Xmax, Xmech - doesn't matter). You limited (input power) the IB system to the point where it exceeded the Xmax at 11 Hz. Then naturally you have to do this also to SLLT. Of course I agree with you regarding the electronics roll-off (my own simulations included it), but when comparing two systems, you have to use the same rules, if you know what I mean.
Of course the ported version will have more output, especially in the 10-30 Hz range, but when optimizing both systems, the final difference isn't as large as you originally showed. And the extra output doesn't come without any expenses (added group delay and ringing around the tuning frequency, and port noises near maximum output level).