Impedance Rise

[roarzorz 10+ year member]

How do you measure it? Any tricks to keep it down?

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[Skip01 5,000+ posts]

clamp meter and dmm

I think it has to do with box size....not sure though

 

[roarzorz 10+ year member]

clamp meter and dmm

I think it has to do with box size....not sure though

But how do I use them. What do I clamp? What am I reading with the dmm? I already know that the amplifiers are pulling 460a of current, the resting resistance is 1ohm, and voltage drops from 14.4 to 11.8. What else do I need to read , and how, to figure impedance rise?

 

[Skip01 5,000+ posts]

But how do I use them. What do I clamp? What am I reading with the dmm? I already know that the amplifiers are pulling 460a of current, the resting resistance is 1ohm, and voltage drops from 14.4 to 11.8. What else do I need to read , and how, to figure impedance rise?

clamp the + speaker wire and put the dmm on the speaker terminals on amp and read AC voltage....and AC amp on clamp meter

Than divide the 2 numbers for ohm and multiply for power

I dont think its exact but good idea of where ya at

 

[roarzorz 10+ year member]

I tested today. My amplifiers are strapped so I think the test is a little different than normal. The amperage output of one strapped amplifier was 48.6 & AC voltage was 37.5. That calculates to 0.77ohms but that has to be per amplifier since its resting @ 1ohm. If that is per amp then I'm getting rise to 1.54ohms and power output is 3644watts at around 67% efficiency

 

[Skip01 5,000+ posts]

resting at 1ohm before strapped?

So .5 each amp sees?

If so that sounds bout right....so each amp .5 and rising to 1.54 and both amps 3644 watts.....maybe

Id have to be there to see for sure...but who knows

My Sundown 1500 was wired to 1ohm, and rose to 3.* ohm and got 944 watts

 

[thch 10+ year member]

notes:

in a strapped or bridged configuration, the Voltage output of the amplifiers add -- so you get double voltage to the speaker. that's double current as well. this means 4x power, but also means each amplifier is passing 2x current for its share of the 2x voltage (eg the 1x it provides).

so impedance "seen" by the amplifier is half (1x Voltage / 2x current). But if you are measuring across the speaker, it is simply the impedance of the speaker, which is given by V/I.

impedance rise is caused by mechanical issues as the speaker will convert mechanical energy into electrical energy (and clearly will convert electrical energy to mechanical). so things like the moving mass of the cone (which needs energy to move faster or slower) and the suspension (which needs energy to stretch) and the port will contribute to the impedance seen by the amplifier.

then you have impedance rise due to the coil getting hot, as well as the cone moving further (beyond xmax, there is less ability to convert energy to/from mechanical/electrical values).

 

[Trey803 5,000+ posts]

so does a bigger volume enclosure=less rise or vice versa

 

[roarzorz 10+ year member]

resting at 1ohm before strapped?
So .5 each amp sees?

If so that sounds bout right....so each amp .5 and rising to 1.54 and both amps 3644 watts.....maybe

Id have to be there to see for sure...but who knows

My Sundown 1500 was wired to 1ohm, and rose to 3.* ohm and got 944 watts

Yes resting impedance is 1ohm before strapped. Each amp is seeing 0.5ohm. Each amp is rising to 0.77ohm and putting out 1822watts each. So that would be 3644watts @1.54ohms for the pair strapped.

I see the testing done by Sundown resulted in 3740watts @ 1ohm @ 68% efficiency for a pair of strapped 1500s. Thats really close to my results.

 

[Lakota 5,000+ posts]

so does a bigger volume enclosure=less rise or vice versa

I've heard that it does, but don't hold my word to it.