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Port area. what does it affect?


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Im trying to make you think clear, but you will not do it.

You keep trying to compare this video of all woofers wired together at .35 to each woofer wired at .7, and still think you have a rise to 1.5, when actually your starting dcr is .7 and your rise is going to be someplace in the mid 2s per amp due to the higher dcr unlike the dcr in this video you posted.

But you cant seem to wrap your head around that.

i need to read this a few times.......

and thanks for "sticking with me"...

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Impedance doesn't change with power other than the heating of the voice coil causing the impedance to increase slightly. Exceptions to this would be there is so much power that part of the voice coil is being driven out of the strongest part of the magnetic field. A box that starts flexing or leaking with added power. Stuff like that

Power compression (causing the voice coil to heat up) isn't the only thing that will raise impedance.

If your port is undersized port compression will raise you impedance too.

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^Yep.

My original post was referring to real world system "tuning" resonances and how that will change with power applied.

Kyle, you can tune your box to 37hz on paper but if you were to measure the "tuning" of that box it would change with every different sub you tried in it because of the difference in their parameters. Woofer parameters can change over stroke and with power applied so you can see how that translates into a change in "tuning".

Its nothing really to worry about tho, just an interesting note.

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Impedance doesn't change with power other than the heating of the voice coil causing the impedance to increase slightly. Exceptions to this would be there is so much power that part of the voice coil is being driven out of the strongest part of the magnetic field. A box that starts flexing or leaking with added power. Stuff like that

With the power levels we run to our equipment we are running our voice coils out of the strongest part of the magnetic field. A woofer operating at or near xmax is seeing maybe 80-50% of motor strength at its travel limits and will have notably different parameters than one being driven with 10 watts of power where the coils sees 100% motor strength the entire time.

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Fine then.

It can happen, but whatever.

woah woah woah, others may be curios as well. I'm curious as to your reasoning because I've never heard of it being possible but i also don't know jack shit lol.

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Awesome thread guys!
I'm also curious about the lower impedance, Krakin.

Also, is clamp metering a somewhat reliable method of calculating impedance? I know the thing about phase shifting between V and A, abnormal readings when distorting, etc., but is it that bad?

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There was a thread some years back that had this conversation. It ended with "unless you are burping don't try to factor in impedance rise"

Seems to apply well here.

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Fine then.

It can happen, but whatever.

woah woah woah, others may be curios as well. I'm curious as to your reasoning because I've never heard of it being possible but i also don't know jack shit lol.

It is just an anomaly that can happen at tuning if everything about the environment for the speaker is correct. Don't really remember past that.

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Krakin, are you some sort of mad scientist?

I would have replied earlier, but I was measuring the output of my amp with a yardstick . . .

What you hear is not the air pressure variation in itself

but what has drawn your attention

in the two streams of superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space

Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears,

thus no formula can achieve a definite effect for every listener.

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you cant drop lower than coil nominal. no such thing as "box drop". the impedance response will always go up or stay the same as the coil. if you are wired to 1 ohm on the dot. your amp will never see lower than 1 ohm.

for those that think it can drop below coil nominal impdance, why do you think that? under heat does the resistance o up or down? while playing the sub did the coil get shorter in length? did the coil conductor size grow to allow less resistance?

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I tried to look for dropping below in one of the scientific journals I thought it was in and couldn't find it. I could have been remembering something else dropping below something else, if I was then I'll admit I was wrong.

I'll look again if I care this weekend, but for now I'll go with I was wrong.

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Krakin's Home Dipole Project

http://www.stevemeadedesigns.com/board/topic/186153-krakins-dipole-project-new-reciever-in-rockford-science/#entry2772370

Krakin, are you some sort of mad scientist?

I would have replied earlier, but I was measuring the output of my amp with a yardstick . . .

What you hear is not the air pressure variation in itself

but what has drawn your attention

in the two streams of superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space

Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears,

thus no formula can achieve a definite effect for every listener.

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