frequency for ported enclosure?

so i have been working with Alpine since i could drive and before that but yesterday after picking up my new Type-R 12's I was told that I tune my boxes too low? I have ranged 37 Hz to 31.5 Hz in the past but yesterday i was told 55-60 Hz is the best level for SPL enclosures? Anyone have comments? have i really been doing it wrong for this long? Thank you in advance.

It really depends on the vehicle, enclosure, placement in relation to the mic, power and subs. In a wall sure a Fb=55Hz+ with huge port area might be best. I just did a ford explorer subs in cargo area, port rear, and subs up. It was best when it peaked at around the 45Hz range. So with a more daily port it was tuned to FB=35hz to get us to peak at the sweet spot of the vehicle. My Navigators spot is right around 44Hz so with my SPL port of 200sq.in. for 2 15s it set to and FB= around 39-41Hz. The only real way to know is to trial and error to find the sweet spot of the vehicle and tune to peak in that range. Thats why when i do a true SPL build i start with more port area then i know im going to need an higher Fb then it should need. Then i can add pieces of mdf to close the port area down and lower the tune right into the sweet spot, running on the SPL mic untill it stops gaining. To get close and a good idea of where it should be. You can measure out the distance of the sound wave to the mic placement. the goal is 1/4 wave. So by measuring out you can get a good idea where you should be peaking. In a normal install this can be pretty basic. In a super mod project it takes a lot more care and thinking of the actual wave path.

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