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WillyD wrote:
 No, you're incorrect. You do not use the peak-to-peak xmax value when modeling. The one-way linear xmax is the standard way of measuring "xmax" and that is exactly what it means.
Put 38mm in the xmax data field, because that is the max linear excursion one-way, and xmax is almost always given for one-way, not peak-to-peak.  |
Xmax is often given as a one-way value, but that's an informal standard at best. There really is no standard, and one certainly can't just assume a particular program takes it one way vs the other. That's why it helps to do some manual calculations to see which way the program takes it. WinISD takes it as peak to peak. It is not doubling the Xmax to calculate the Vd, so you have to enter it as p-to-p. If you don't, you won't have the right value for Vd in your model.
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No, I was talking about the 5400. You're stretching what I said just a bit though. The 5400 does model well in a larger and lower tuned sub, but it doesn't need a 19ft enclosure.
The way the 5400 models, to port it properly in such a large/low tuned design you end up with way too low of a 1st port resonance, IMO. It is simply better suited to slightly smaller designs IMO, like 13ft^3 at 13Hz, or 14ft^3 at 12Hz.
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Yes, at 19 cu ft with a single 8" port tuned to 12hz, the 1st port resonance is a bit low at about 156hz, but not horrible. Steve's writeup recommends around 190hz, so it's a bit under that, but I don't think it's likely to be a deal-buster. If that's not good enough, by boosting the volume up to 22 cu ft and keeping the same tuning and port size, the 1st port resonance rises to over 184hz while only inducing about a third of a dB of resurgence in the shelf response around 13.5hz. This wouldn't be an audible effect and it gets the 1st port resonance right near the sweet spot.