resonant freq testing with a ported box.

[P4killer_]

So im going to seal off the trunk today and see what happens. I was thinking about testing for resonant freq. Could I simply just plug the port and test? And say it peaks at w.e freq.. say 45 hz. If you then tune the enclosure to 45hz won't there be some degree of cabin gain which would make it peak a bit higher? There usually is.. I mean I'm tuned to 37 Hz IIRC and I peak at 44 Hz sealed.. how does one figure for cabin gain?

[P4killer_]

no body tests resonant freq??????? bump

[ALPINE408]

single sealed ten and a term lab to find rez freq.

and yes your biggest number will almost allways be at res freq

[P4killer_]

i understand that you will peak score wise at res freq.. thats kinda the point in finding it. what im asking is.. if you tune to xx freq, usually with cabin gain your peak will rise.

so for example if you test and come up with 42hz res

build a box to 42hz, but with cabin gain the setup actually peaks at 47hz..

how do you combat this other than just guessing? im tuned at 37 i peak at 44 ported.. is it reasonable to assume 7hz of rise?

also i understand a single 10 will do the job. i dont want to build a sealed box... would it be ok to just plug my port effectively sealing my box and test that way? idk why that wouldnt work..

also most ppl mention testing for res freq at medium volumes... how is this effective? usually your peak will change a few hz from say mid volume to full tilt.. or is this only ported enclosures that do that? I dont really use sealed setups so idk..

i need someone to elaborate on the details.. i understand the basics

i appreciate the reply though,

p4

[ALPINE408]

if your car peaks at 42 you build a box at 42hz you will peak at 42hz cabin gain is where you have a setup like yours tuned to 37 but the car rez is changing the over all peak. the only way to truly test for peak res freq is a single sealed 10, if you test the way you are thinking it will be false results being that you will have cabin gain

there are the rare cases like my old truck no matter where you tunned to it would allways peak at 55hz build a box for 22hz it will still be the loudest at 55hz but you still lose output for tunning that low then i tuned for 55 and my numbers jumped up big time

[P4killer_]

so i will experience cabin gain even if it were to plug the port and make it sealed? I cant justify buying a separate 10" sub and building a box for just that.

But if you're saying it can only be done with a ten than it is what it is..

[bkolfo4]

If you are really serious about SPL, get ready to build multiple times and test.

I use a ported box to test and test different port lengths in 1" increments. Plotting the output of each and testing the true port tuning frequency will normally show you the frequency that stands out and the correct frequency to tune to (rarely do you tune to the same frequency as the peak, since the output peak of the sub will be above the tuning frequency).

[P4killer_]

so basically you just start with a long port and cut down untill the spl rolls off... i guess thats easier and yes i understand that it would take alot of time and effort i was just asking about this res freq procedure but basic spl testing yea you could spend many many hours on that.. im not that serious, no. i hardly have time or the energy to do what im working on these days let alone a serious spl build.