Ported Enclosure Unloading?

[tinmanchris217 10+ year member]

Pioneer's website is lacking alot of specifics, but the 2502 is basically the same sub, with a shiny cone on it.

Small VAS, xmax, etc.

How do you do the gain-setting for your Opti's? with subs or without?

 

[n2audio 5,000+ posts]

W/o, but these are Zed's designs - stiff regulation -- there is almost NO difference in output from 14-12.8v.

 

[tinmanchris217 10+ year member]

So did some light burps today and recorded some interesting info.

resting impedance was 3.8 Ohms

40 Hz - 42.6V

50 Hz - 34.9V

60 Hz - 25.0V

65 Hz - 18.3V

Unless my meter (Craftsman DMM) was failing at Ohm readings, or I **** at life...

40 Hz - 2.6 Ohms steady.

50 Hz - began at 170 Ohms, and after the "Unloading" started 5 seconds in, the impedance rose to 3700 Ohms and was constant.

60 Hz - similar except 5,800 ohms.

Dunno guys, it's rather weird....

Oh yeah, and voltage drop is 1.4 V at the start, so we have surpassed alt power but not by too much.

 

[SomeDonnieDude 10+ year member]

I don't think you can accurately check impedance rise with a multimeter. Almost positive you need a clamp as well.

 

[tinmanchris217 10+ year member]

That would make more sense... and explain my weird numbers.

Ohm's Law as usual? Is that how everybody does theirs?

Impedance = Volts / Current

 

[tinmanchris217 10+ year member]

A new odd symptom to the list.

The unloading happens when the subs face forward. If they are facing UP, I can clip the living poo out of them, and no unloading.

New Hypothesis: Box IS too big, and subs reach xmax too easily. When the cone moves out of "magnet controlled" motion, and is vertical, the weight of the cone keeps things slightly more stable, when it is in line with the motion.... Horizontally, it flops like a fish, because the motion is not strictly linear anymore.

It's not adding up logically though...

 

[James Bang 5,000+ posts]

I love the sound of an unloading sub. fffFhhhhFffFFFhhhhhfffFFFFFFFffffhhhhh

 

[Volenti 10+ year member]

A new odd symptom to the list.
The unloading happens when the subs face forward. If they are facing UP, I can clip the living poo out of them, and no unloading.

New Hypothesis: Box IS too big, and subs reach xmax too easily. When the cone moves out of "magnet controlled" motion, and is vertical, the weight of the cone keeps things slightly more stable, when it is in line with the motion.... Horizontally, it flops like a fish, because the motion is not strictly linear anymore.

It's not adding up logically though...

I'd be putting my money more on the enclosure loading in the car better when facing up, increasing the mechanical powerhandling of the drivers, presenting a more friendly load to the amplifier, or a combination of the two.

This effect would be noticable in an impedance graph.

 

[audioholic 5,000+ posts]

Altering the front loading on the sub can certainly affect its excursion for a given power input. But this difference should not be drastic. Likely if this makes the difference between bottoming out and not, you were riding on the edge of doing it anyway.