Question about odd sub movement?

[vehementSPL 10+ year member]

How does dampening factor affect the way the sub moves. And I don't mean the number persay. I mean overall. If your dampening factor is way to low does it cause the subs to move more than normal without producing the extra sound in ported enclosures. ANd what affects this number besides the amplifier. The reason I ask this question is because I have noticed in the past sometimes when you severely underpower subs in ported enclosures sometimes they seem to move a lot more than they should for the amount of power going to them

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[vehementSPL 10+ year member]

ttt

 

[helotaxi 5,000+ posts]

Frequency matters a lot more than power with a ported enclosure. The damping of the enclosure has a much larger effect on the cone movement than the DF of the amp. Play right above or below tuning and it doesn't take much power at all to really get the sub moving.

There's no such thing as an underpowered sub.

 

[Immacomputer 10+ year member]

What you're noticing isn't a change in the damping factor but just how power scales. The damping factor of the amp will help control cone movement around resonance (system resonance, not the tuning frequency of the enclosure) but it won't change much with increased power.

The relationship between power and cone movement is not linear and neither is the relationship between power and output.

My sub gets moving pretty nicely on a 100 watt amp I have and doesn't move a whole lot more on the 300 watt amp but the difference in output is noticeable. That's completely normal but not because of the damping factor.

 

[vehementSPL 10+ year member]

Thanks. That makes me feel a lot better. i didn't want this to be another one of my "out there theories". Today my friend with 250 watts on his 2 se 12's have them moving about an inch each. And we were talking about this theory but I was thinking maybe his box is just huge. And then he told me he had 1400rms on the pair and only had 30 percent more movement. And I could have swore many times in the past I had ported enclosures that the sub moved decently with little power then when i trippled power didn't really move any further. . there again I wasn't sure if I was just remembering incorrectly or if that was fact. . That makes me feel a LOT better about upping the power to my 8 12's. Off a clamped 560 watts each sub moves like 1/2inch or a hair more through most of the range. And I wanted to do 4 to 6 times the power daily... But the issue had started to become well crap these things aren't going to take 4 to 6 times the excursion without issues daily. But then this last week i had been stuck on this theory and now with this post and seeing what i saw today and talked with a few others and they had same exp I feel better

 

[vehementSPL 10+ year member]

What you're noticing isn't a change in the damping factor but just how power scales. The damping factor of the amp will help control cone movement around resonance (system resonance, not the tuning frequency of the enclosure) but it won't change much with increased power.
The relationship between power and cone movement is not linear and neither is the relationship between power and output.

My sub gets moving pretty nicely on a 100 watt amp I have and doesn't move a whole lot more on the 300 watt amp but the difference in output is noticeable. That's completely normal but not because of the damping factor.

Ok. so what exactly causes a sub to not move a whole lot more when you triple power but yet still triple volume. From the physics aspect how does it work?

 

[helotaxi 5,000+ posts]

You're doing more to excite the air in the port. Around tuning, the port is responsible for most of the output. At that point the inertia of the air in the port greatly ups the force it exerts on the cone and keeps it from moving any more. You will notice that the port velocity increases a great deal though the cone isn't really moving much more.