Strange spike

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When modelling modern high mass drivers in vented boxes i often see huge narrow spikes at or near the f3/tuning.

Anywhere from 8-16 db spikes.

I notice that it is often in large volumes with low tunings and i tend to attribute it to Hoffmans iron law.

Is it an artifact to be ignored or can it be considered real due to high mass cones operating in vented boxes tuned near the fo of the driver?

Edit: i use Hornresp.
 
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2 of these drivers in a box this size is an example.

High mass, huge xmax drivers.
 

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I would suppose that would be considered a sub-optimal box.
Even with a sealed cabinet there are quickly diminishing returns to making the enclosure bigger. Its quite easy to use the Hornresp speaker wizard to tune up the enclosure and port to get a reasonable result. Unsurprisingly most drivers are optimised to work in small enclosures.
If you really want a big box maybe you should look at a driver like the Eminence Kappa-15LFA, or some vintage drivers that pre-date Thiele Small like the Tannoy Monitor Gold 15"
Tuning a box with a peak at the port frequency is usually done to increase bass output where its useful at the expense of bass extension as in the Fane 15" ported enclosure plan. In a small enclosure it can be used in tandem with a second order hi pass filter to get an extended response without exceeding x-max (QB5).
 
Its not my drivers...its a pair of sundown x12s. The grwy line is 2 of them in2.5 cubic feet. Not sure. Im not concerned about whether it sounds good...there are other drivers like you said. I just wanted to know if the spike was an artifact or actual output i could take advantage of.

If it were my box id build thr small vented box for scaring small children and have a plate i could install over the vent for those times i wished for sound quality at its maximum.
 
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