View Full Version : Box Rise.. how to figure it out??

09-19-2005, 05:05 PM
ok so I figured out that my amp is giving 1800+ at 2ohms
my subs are wired up at 2ohms
now how can i tell if there is a rise in the independance due to the box. So i can find out my ohm load to the amp.

any easy way? searched it up cant find ****.. lol

asked this over at termpro to.

09-19-2005, 05:27 PM

thanks great info
but daaamn that just confused the hell out of me, and i still dont know what im doing

By now, you’re either heading to your amp with tools in hand –or- wondering where the heck impedance rise comes from.

started laughing when i seen this, cause i sat there with my mouth open like.. ummm i have to be missing something, how do u check this??:crazy: :crap:

09-20-2005, 01:45 AM
clamp the meter around the + or - wire, not both.

biiiiiiiiig spikes sometimes... crazy to see how much power your ACTUALLY getting.

it really sux when you think you wired your strapped amps down to 1 ohm... but in reality they are seeing a whopping 8 ohm load on a burp.

09-20-2005, 01:48 AM
1) Burn a CD with test tones in 1 Hz increments from 10 to 100 Hz.
2) Hook your system up as normal, but remove all filters and processing (Bass = 0, Mid = 0, Treble = 0, no SSF, no LPF, no Bass Boost, etc.)
3) Wire a clamp ammeter in parallel with the speaker(s)
4) Put in Tone CD and set to repeat.
5) Measure AC voltage at the amplifier's outputs. Write down the voltage for each frequency.
6) Write down the current flow measured by the clamp meter.
7) For each frequency, Impedance = Voltage/Current
8) Skip to next frequency and repeat steps 5 through 8 until finished.


Voltage shouldn't change with frequency, but amplifiers don't always have a flat response. You may also have messed something up or your tones may not be recorded at the same level.

The tuning frequency of the enclosure will be the lowest point between the two peaks.

ok ty much easier to understand.
now if i dont have a clamp meter. could i use another DMM or nah?

09-20-2005, 02:05 AM
gotta get AC current, gotta have a clamp meter for that :)

worth the investment... trust me... dam thing is INVALUABLE when you setup *any* system.

09-20-2005, 02:16 AM
ok thanks for the help

09-20-2005, 03:31 AM
This thread is great, i'm definitely going to have to do this when i get some time. Lol, by what people where saying, i didnt think it was possible to measure impedence rise.

09-20-2005, 03:39 AM
so extremely humbling... seriously.

its hard to get a grip on rise, too... takes some ingenuity.