Understanding Tuning

[reclessantics 10+ year member]

I know how to get to a certain tuning (for the most part.. very rough) thats why i want to learn how it works better, so im more comfortable with it.

I know that you have to have 12 - 16^2" of port area per cube foot of box vol. i get that kinda ( not sure what changes as you go to 12, or go bigger to 16")

My question is, what actually changes tuning (higher/lower)? Say all variables are the same - box vol, port area ect... Would changing the port length change the tuning? ex - Longer port = lower tuning and shorter port length = higher tuning? (maybe im backwards, but what changes the tuning is just the port length essentially)

thanks

kyle

Click to read more...

 

[MONSONwarrior Premium Member]

you had it right with the port length.

 

[reclessantics 10+ year member]

word.. how about the recommended 12-16^2 of port area per cube ft? does smaller area have a different sound then larger area? or does it just keep options open to help with tuning? (more area, shorter port. or if you can have a longer port, you can go smaller area.. ect)?

 

[RAM_Designs 5,000+ posts]

word.. how about the recommended 12-16^2 of port area per cube ft? does smaller area have a different sound then larger area? or does it just keep options open to help with tuning? (more area, shorter port. or if you can have a longer port, you can go smaller area.. ect)?

Just think of the port like a radiating surface. The bigger the port, the more air you have moving when you get closer to tuning, and because of that a bigger peak. Larger ports also cause the woofer to unload easier below tuning.

 

[n2audio 5,000+ posts]

I'm not sure how the general rule of X sq in per cubic foot is derived, because to the best of my knowledge req'd port area is relative to displacement of the sub.

If the sub displaces a great deal of air (large cone and/or large xmax) then the port will need to be large to reduce port noise.

However, it is possible with a lower displacement sub the port can be much smaller than one might expect without any chance of port noise in the usable frequency range.

 

[reclessantics 10+ year member]

yeah that makes sense. how about box sizes? (little different subject) the recommended vol for ex of an FI Q 18, is 6-10 cubes. What would the changes in sound be? (smaller vs higher?)

ex. - would the smaller box be more efficient (ish) while the larger i make the box, the louder i guess?

Im debating on going with some q's for a new sub set up, i want to throw 2 18's in my ext cab silverado. But not pos if ill be able to fit a 20cube box in the back seat area. just curious

 

[reclessantics 10+ year member]

Larger ports also cause the woofer to unload easier below tuning.

Unloading? is that like a failsafe for the sub? where if it unloads easier, it will keep it from damaging itself? because it will be closes to free air. i guess? lol

 

[reclessantics 10+ year member]

Is bigger port area better?...

btw, if possible, is it better to go with the biggest box (vol) recommended? or do larger, vs smaller do different things (different pros and cons)

 

[n2audio 5,000+ posts]

Unloading? is that like a failsafe for the sub? where if it unloads easier, it will keep it from damaging itself? because it will be closes to free air. i guess? lol

The opposite.

At and above tuning the box acts more like a sealed enclosure helping to control the sub's cone movement. Once it gets below tuning the port has less and less of an effect and the sub can approach mechanical damage a lot easier. That is why a lot of amps have subsonic (infrasonic) filters - to low cut below the tuning freq of the encl.

Is bigger port area better?...
btw, if possible, is it better to go with the biggest box (vol) recommended? or do larger, vs smaller do different things (different pros and cons)

If you start messing with a modeling program (winisd pro) and looking at a sub in different box sizes what you'll see is that small boxes tend to plot "peaky" meaning they have a big spike in output over a very narrow freq range, usually on the high side. A lot of output at 50-60hz and not much down low.

A large box tends to produce the flatter response and go lower.

 

[reclessantics 10+ year member]

word, yeah im going to dl the winisd. but that makes sense. thanks

so what does that mean with port size? should i stick with smaller? or larger?