Explain graphs and specs please.

[sikcavy 10+ year member]

I've been building boxes for a few years but basically have been doing it through trial and error. my question is how do you read graphs and how do you design a box correctly? i don't know what to do with the speaker specs and am unsure of what to do with it. What does it take to make a very good sq box and what does it take to make a very peaky spl box? Thanks a bunch guys.

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[Immacomputer 10+ year member]

What does it take to make a very good sq box and what does it take to make a very peaky spl box? Thanks a bunch guys.

In both cases, it takes knowledge of the vehicle and its cabin dimensions/layout.

Trying to use any basic enclosure design software is not going to yield similar results as the vehicle's effects are not accounted for. About the only thing those are useful for is reading group delay and impedance plots but even those will change when the vehicle is introduced.

So unless you're building an enclosure for a very large room, the graphs you're going to get from enclosure design software are pretty useless.

 

[crash9201 10+ year member]

so what program do people use to actually map out the box; im sure you could do it with any

cad type program; but ive been looking for a program to use that is free(i never pay for software); ive been trying to design a box for quite some time and like OP i just get confused by the graphs etc.

 

[sikcavy 10+ year member]

so what is port velocity and whats the big deal with it?

 

[SSS 18734 5,000+ posts]

About the only thing those are useful for is reading group delay and impedance plots but even those will change when the vehicle is introduced.

And excursion... and port velocity... amongst others.

Far from useless. The only thing that really changes is the response curve because of cabin gain and resonant frequencies. And even so, you can somewhat simulate cabin gain.

 

[Immacomputer 10+ year member]

And excursion... and port velocity... amongst others.
Far from useless. The only thing that really changes is the response curve because of cabin gain and resonant frequencies. And even so, you can somewhat simulate cabin gain.

Excursion and port velocities are going to be off by up to 20% or more in Winisd. I'm not sure about bassbox but I know that winisd is pretty off with cone excursion as far as peaks. With port velocities, you can go by a relative scale but even then, I would rather rely on understanding the driver and enclosure I'm using. Winisd can't account for the port geometry, placement, or loading effects, all of which will affect port velocity.

The best way I've found to simulate cabin gain is by using Matlab and modeling it as a transmission line. It's tedious as you need many dimensions of the vehicle but I was able to get a very close model to my sub in my car by modeling it as a transmission line (windows down or up) and as a mass loaded transmission line (sunroof open and windows up).

so what program do people use to actually map out the box; im sure you could do it with any cad type program; but ive been looking for a program to use that is free(i never pay for software); ive been trying to design a box for quite some time and like OP i just get confused by the graphs etc.

For physical layout, Google's Sketchup is a great cad tool. This is not enclosure design though, it is strictly a layout tool and and easy to use one at that.

 

[sikcavy 10+ year member]

is port velocity good or bad? and whats it deal with inrelation to tuning?

 

[Immacomputer 10+ year member]

is port velocity good or bad? and whats it deal with inrelation to tuning?

High port velocity will cause eddy currents in the port which will result in a loss of output and an increase in port noise (that chuffing or wind sound) at high volume levels. Port velocity will be at a max at the tuning frequency of the port.