Winisd Question

In an anechoic setup, the best would be the 16 foot box. In car I would suggest that above the others as well. We don't want peaky transfer function and both the other boxes are indicative of that. What we are looking for is a smooth transfer function...

On an additional note, the car will naturally boost lower frequencies as well. A dip starting at 45 Hz is not very bad at all, as the vehicle will bump the low end around that point (as a general rule).

Depending on EQing and where you cross your subs, you can do some tweeking to level it all out.

However, there is more to SQ then TF as well. You also need to keep in mind group delay. The flatter the group delay, the more accurate the enclosure will be. If you model it up in a QTC .7 sealed, you will see very near the target delay you want to acieve. In a sealed box we increase the size of the enclosure to lower the delay. In a ported enclosure we decrease the enclosure size to decrease the group delay.

Also, what is the QTS/EBP of the driver in question. We may want to determine if porting them is a good idea

 

there is alot of tweaking you can do with a ported box in regards to the Transfer function, Like SandT38 said.... the 16cube box would give you the best sounding response, But just look at the huge box size... 16CUFT !!!, sure hope thats for a few subs and not just 1.
also... like already said, keep in mind the Group Delay, The lower you tune a ported box, the better(lower delay) the delay will be. This will help reduce how Boomy or muddy the sub will sound.

Ported boxes naturally will have a little bump in the low end frequencies that sealed boxes don't have, and in a car this may not be the sound you are looking for. So its possible that you might want to reduce the box size of a ported box to decrease its delay & give it a more "sealed box" like rolloff.

its just amazing how much tweaking you can do. What you will like best is hard to say... i'd suggest start building boxes, maybe 2 or 3 different alignments, spend some time listening and figure out what you like about each box, and what you don't like, and try go design the perfect box for your needs from what you've observed of your test boxes.

 

WinISD has to start you somewhere, right?
Too often, people see the plot WinISD starts them with and think that means WinISD is "recommending" something.
It's just a starting point. You have to tweak it to get it to be what you want.
WinISD has to start you somewhere.

Hoffman's Iron Law is something to keep in mind here, as it regulates what you are able to do.
It states that the following three items are mutually exclusive:
1) high efficiency (high peak dB number reached on your plot)
2) small enclosure size (box volume on the box tab in WinISD)
3) low frequency extension (how far down the elbow of your curve reaches on your plot)

You can only gain in one area by trading off in others, because they are mutually exclusive.
So state your goals, in these terms. And design your box according to that. B)
So you could build an enclosure that was tiny (maximizing 'small enclosure size'), which would inherently either not be very efficient (would require tons of power to reach full excursion and output), and/or would not play very low frequencies.

You manipulate the shape of the curve yourself, by manipulating either enclosure size, and/or port tuning frequency.

The lower you make this able to extend, anechoically (meaning in an infinitely large, open area with no reflections - which is what this plot simulates), the more you are maximizing 'low frequency extension'...
...and you'll see you need to either make the box bigger to do it (trading off 'small enclosure size'), or you need to tune the box lower to do it (trading off 'high efficiency), or both.

The more of an SPL 'peak' you build into it, the more you are maximizing 'high efficiency'...
...and you'll see you need to either make the box bigger to do it (trading off 'small enclosure size'), or have to tune the box higher to do it (trading off 'low frequency extension').

The smaller you make the enclosure to fit in your trunk, the more you are maximizing 'small enclosure size'...
...and you'll see you either need to tune the box lower to keep frequency response curve extending fairly low (trading off 'high efficiency'), or else you'll end up trading off 'low frequency extension'.

Hopefully this helps you!

Another thing to keep in mind is "cabin gain", which is simply a natural "bass boost" that occurs in your car's interior, since it's a small enclosed space.
Basically, below whatever frequency whose wavelength corresponds to your car's longest interior dimension, you get a 12dB/octave "bass boost", which will dramatically change (skew) the actual in-car response (how it sounds) from the anechoic plot that WinISD approximates.
Keep that in mind, because IT IS THE REASON that sealed boxes, that seem like they just roll off way early and steadily actually sound more flat in a car than a ported box can.

"Good" is whatever you personally desire. Design your box to that! B)