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Discussion Starter #1
I was doing some reading last night about these spl guys saying the box can alter the ohms.

How does this work?
 

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impedance rise happens with box or without box, anytime the coil travels through the motor the impedance changes. Mainly important if you burp for competitions, irrelevant if you are just playing music at SQ levels. Its the main reason why you have people say i can throw 1500 watts rms to my sundown SA 12. They will never get 1500 watts wired to 1 ohm if the amp is rated for 1500 at 1 ohm. They will see at best 2 ish ohms of power at certain frequencies at full tilt. which is right around the RMS rating of the sub which the sub should be able to handle for hours if the testing and R&D is proper and doesnt lie like some trash brands. Usually higher end SPL brands are extremely conservative on those ratings as well. but in general you are never using as much power and current as you think you are getting.
 

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A driver and a driver with enclosure has a maximum impedance, which would also be the resonant frequency. At this maximum, the driver will provide output with the least amount of power needed. And if you play a single frequency at this resonant frequency, the driver barely moves but be very careful because you’re putting power into the driver but it isn’t moving much to be able to cool the voicecoil.
 

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And if you play a single frequency at this resonant frequency, the driver barely moves but be very careful because you’re putting power into the driver but it isn’t moving much to be able to cool the voicecoil.

You're partially thinking of playing near the tuning frequency of a vented-alignment type enclosure where the port dampens the motion of the cone though. In free-air or sealed, Fs or Fc respectively, at resonance the cone excursion peaks, which is why the impedance increases due to back EMF, hence higher electrical resistance.
 

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You're partially thinking of playing near the tuning frequency of a vented-alignment type enclosure where the port dampens the motion of the cone though. In free-air or sealed, Fs or Fc respectively, at resonance the cone excursion peaks, which is why the impedance increases due to back EMF, hence higher electrical resistance.
You’re right, I got that confused. Thanks for the catch.
 

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Discussion Starter #7
The reason I asked was mostly out of curiosity.

Also I accidentally hooked my jl 1200/1 up to a pair of frog 10s at 1 ohm.

The amp is only rated to 1.5ohm. It played for 2 days before I realized the mistake. The jl put out a ton more power but eventually went into protect the on the second day.

When I first hooked it up this way it was in a ported enclosure and after moving the subs to a sealed enclosure the amp went into protect.
I thought it was odd.

Jl amps arent the greatest I know but they sure seem to cover the bases when it comes to protection.


On a side note can you raise the ohm load say .5 ohm, just using large amounts of speaker wire?

I mean I know you can but the amount of wire would need to be significant.

This is all theoretical. I'm not actually doing it. Just random thoughts.
 

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You can use a very thin wire between amp and sub....it will heat up and present some additional impedance.... but you probably wont do that...when I compete in dBDrag we use to try out every possible thing that we thought it might help us with result

yet again - model your speaker in WinISD or Speakershop or LEAP or similar software, change enclosure volume and tuning and observe impedance graph.....
 
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