Impedance rise.... how to battle it?

[JakeW]

So we know it’s real, and it can affect a daily driving setup, just the same as competitive setups. The sub plays, and as the frequency changes, the impedance rises. If you’d like to get more technical that’s fine, but my question is who’s encountered it and who’s changed their system to compensate? I clamp tested mine today with 3 test tones. (1) -5db, (2) -10db and (3) 32hz tone off YouTube. The (1) & (2) tones got me 2234w @ 6.8 ohms! I’m wired to 2ohms so that’s a raise of 4.8! The (3) tone from sonicelectronix off YouTube got me 3013w @ 5.67. Still a ridiculous raise, but lowest no doubt. I only have 1.39cf per sub available in this enclosure, so I know that’s a restriction. But knowing now what we know, would I throw an md8 at them, so the power is more efficient or will it just be a forever clipping system? These readings are taken at a hard yellow clip

[Joe X]

The following are the modeling curves for a sealed box inside some car:

 

Output in dB (normalized) inside a car:

 

 

An then impedance:

 

 

As you can see at about 36Hz impedance is close to 30 ohm up from close to 4 ohm at the extremes.

 

You would expect a heavy dB loss around 36Hz due to the high impedance, right? But as you can see that doesn't happen, not at all. Not even a little bit.

 

And this is not power (W) but output (dB) which are not the same.

 

[liteblue]

Your enclosure has a huge effect on ohm rise, sometimes called box rise. Emf did a video explaining it. He clamped a subwoofer in a box and free air. 

 

You can try a few things. Jacob Viral made a video about box rise, you can check that out if you have not yet. Barevids talks about it aswell and why you should understand rise before wiring down below 1 ohm. 

 

Some things to try would be increase port area. You can potentially lower resistance at tuned frequency. Parallel vs series voice coil wiring. Amplifer nominal impedenace below 1 ohm. Bigger amplifier. 

 

Ohm rise is the same regardless of power until you hit thermal limits. Do some lower power testing for numbers. 

[Dafaseles]

On 2/27/2021 at 7:10 PM, Joe X said:

The following are the modeling curves for a sealed box inside some car:

 

Output in dB (normalized) inside a car:

 

 

An then impedance:

 

 

As you can see at about 36Hz impedance is close to 30 ohm up from close to 4 ohm at the extremes.

 

You would expect a heavy dB loss around 36Hz due to the high impedance, right? But as you can see that doesn't happen, not at all. Not even a little bit.

 

And this is not power (W) but output (dB) which are not the same.

 

I've always wondered how this works out. You don't hear a sharp decrease in volume with the rise, does it have to do with the resonate frequency of the vehicle or something?