Power testing my 1500D

[3stagevtec 2]

I did a quick test today on one SAZ1500D.. i used a clamp on meter to measure current in the speaker wires and a digital multimeter to measure voltage..

i'm not sure if i measured this correctly, but i recorded the peak values seen and not the average.. I played a 48Hz test tone during testing and used a pair of dual 4ohm Audiopipe TXX series subs..

Re per coil - 3.6ohms

1st try.. (volume up high, but not maximum..)

Voltage - 57.5V

Current - 23.7A

Power - 1363W

Impedance rise 0.9DCR - 2.43ohms

Voltage at the amp dropped from 14.4V - 12.1V

I tried it again at a lower volume and got this..

Voltage - 38.0V

Current - 15.7A

Power - 596.6W

Impedance rise 0.9DCR - 2.42ohms

(I calculated power and impedance rise using formulas P=VI & V=IR)

Questions..

1) I noticed the impedance rise was the same at the different power levels.. is that normal? or can impedance rise be affected by power output.. (ignoring impedance rise due to temperature rise in the coils)

2) was i correct to measure peak values and not the average seen...

thanks..

Edited July 10, 2008 by 3stagevtec

[shizzzon 461]

no dont measure peak.

The peak values will not be taken at the exact same time!

When resistance rises, the voltage will too. When resistance is lower, the amps go up.

What you need to do is hook it back up, do not hold peak or get their values. Start your burp and wait until both meters level out. What i mean by that is wait until the numbers stop changing rapidly and start staying consistent. At this point, visually record both the volts and amps and write em down.

[3stagevtec 2]

i had a feeling i was measuring it wrong.. thanks..

what about impedance rise? would it be the same at different power levels, at the same frequency, ignoring rise due to temperature..

i would like to map the impedance rise of my enclosures, but i don't want to burp each frequency at max volume just to measure...

[shizzzon 461]

impedance rise shouldnt be the same at different power levels. At a lower level, the rise should be greater.

[sundownz 197]

If the coils haven't had time to heat up the rise will be the same at varying power levels - you can be sure that on the second burp the impedance rise should be higher on higher power due to thermal compression.

But yes, you can use the lower power figures to map impedance rise.

Just have someone watch the meters so they can get both figures at the same time and don't use the peak hold function.

Did you get any SPL numbers?

[3stagevtec 2]

^ excellent! was hoping so, especially as my tests pointed to that..

before, i had a Soundstream 2000D amp, the best score i managed with it was 145.5dBs with two Audiopipe 15" subs.. (yeah, i know is Audiopipe, but i'm a brand loyal person.. so i like them)

with 1 1500D, i managed 144.9dBs @ 48Hz

with the 2 strapped, i made 147.0dBs a personal best!

the excuses

-i neeeeed an extra battery! voltage dropped to around 10.8V at the amps!! yikes!!! plus, i will have to upgrade my wires as well.. i need power to make power..

-my current boxes are made of 3/4" mdf and are completely unbraced.. they were my 1st ever attempt at designing a loud box, not an SPL box. they were made about 2 years ago, and i've learnt quite alot since then.. so there's definitely room for improvement..

the flex in the enclosures was kinda funny during burping.. a pliers that was on top of them fell and almost hit one of the amps.. i almost cried yes...

these days i'm just experimenting with different box sizes, port sizes / placement, tuning freqs etc.. i usually use the local competitions to test any changes i make, so it's an ongoing / learning / fun process..

Edited July 10, 2008 by 3stagevtec

[sundownz 197]

Congrats on the score!

[shizzzon 461]

If the coils haven't had time to heat up the rise will be the same at varying power levels - you can be sure that on the second burp the impedance rise should be higher on higher power due to thermal compression.

But yes, you can use the lower power figures to map impedance rise.

Just have someone watch the meters so they can get both figures at the same time and don't use the peak hold function.

Did you get any SPL numbers?

I'd like to object, your Honor,

I've done tests measuring power output from an amp from volume 1 up to where it begins to clip and each time the volume increases, the impedance rise decreases taking for granted that their is no power compression.

The latest test i did, i got the notebook out in the garage somewhere, has all the specs wrote down from the last test i did.

I had 1 sub wired in series to 7.2 ohms. Test amp was a home audio amp rated to do 100w@8ohms.

At volume 1, the resistance was just over 20 ohms if i remember correctly but by the time it got to output around 110w, the resistance was low like around 10 ohms.

When i have time, i'll come back on here and post evert single volt and amp reading i got at every consecutive volume increase interval so you can see exactly what i got.

[3stagevtec 2]

the two tests i did showed that the impedance rise remained almost the same at 597W and 1363W, when the same frequency was used.. when i get time, i check it again..

[shizzzon 461]

I stand corrected for the time being.

The information i have wrote down is NOT for the same frequency at varying power levels so i'll remain dormant on this topic until my amps come back in working order for me to test myself.