How do i measure the actual output of my amp?

[pimp86LX]

I was thinkin I cuold just hook up an A/C amp meter to my speaker output but i don't really know, and obviously don't want to damage anything. I'm a D/C taught electritian so A/C is kinda alien to me.

HELP! I have a feeling my amp is overrated and want to prove it


Paul Tha Pimp :pimp:

[AccordEpicenter]

well this is the way you can do it with home equipment to get a ballpark estimate, another way (and more accurate) involves expensive equipment. This is best done on a monoblock amp or an amp that is bridged. Lets take my Lanzar Vibe 1200d. Play a loud loud continuous bass tone that makes the system the loudest (but not into distortion, clipping!!!) and measure the ac voltage between the bridged speaker terminals (where the speaker hooks up). Most ac digital meters measure in RMS volts. So anyways, when i measured mine, i hit somthing like 36v (i forget, maybe it was more) so the voltage divided by your ohms, (my amp was into 1 ohms) so that gives us 36Amps of current, so the Volts times amps = 1296 watts. This particular way of measuring the amps power usually works out to a little more than the amp is putting (usually 10-15%) out because your banking on your subs being the exact impedance of whatever they are rated at but in actuality a subs impedance changes with the frequency of the signal being put in it and also the sub size/type/brand blah blah blah there are alot of variables... the subs arent a resistive load, they are reactive...

[pimp86LX]

gotchya gotchya. ill give 'er a try ! thanks

[pimp86LX]

hmm my digi-multimeter can't keep up with the changing voltage. its hard to get a reading.

Can anyone reccomend some test tracks and were i coudl get them?

[AccordEpicenter]

yeah it has to be a steady tone... you MUST use a tone cd like Bass mechanic or some other test cds.. somthing that plays nothing but a pure sinewave for bass

[pimp86LX]

hmm so something like a competition test track?


damn whats the damn of that org.? ISAC? ISCA? doh...stupid memory

[AccordEpicenter]

yeah basically... IASCA? Is that what youre thinking of?

[pimp86LX]

YAH!! :D

[AccordEpicenter]

oh i forgot to mention that this way of calculating the power only works when you actually have subs hooked up to the amp... they are your load

[pimp86LX]

yeah, that what i assumed. with the 4ohm in the formula and such

[AccordEpicenter]

well if thats what your subs are set up for... It kinda goes like this, maybe you know it, maybe you dont. You cant just use what ohms your sub is, you have to look at it and see what the amp is getting. For example, to get the one ohm load for my 1200d , i have dual 4 ohm subs, and i had both coils hooked up in paralell, with halves the 4 ohms and gives me 2, and then because i have 2 2ohm subs in paralell that gives me 1 ohm, because they are halved too. So if you have 2 single voice coil 4 ohm subs wired in paralell with the amp bridged the amp is seeing 2 ohms, and thats what you should divide the voltage by to get your current.

[pimp86LX]

k, with the deck volume at 20 (45x4 peak) and playing "SPL shootout-ss bass track" i acheived an average of 28v...wich if i follow your formula right translates to 196watts...minus say 10% would be
(196*10)/100=19.6 from 196=176.4watts

I don't think that is horrible considering i have an el-cheapo amp rated at 200watts. and it moves my single 4ohm sub ok. (sub is rated at 350rms but again i believe that is overrated)

[pimp86LX]

that sounds like a serious setup man...NICE :D

[pimp86LX]

HMM ...even better. I just did another 3 runs with a track called "350hz to 20hz sine sweep". one continuous tone. It faired better and got an average of 30v.

[AccordEpicenter]

yeah that sounds pretty good... what amp are u using? Also when i ran the 1200d to get those valued my battery voltage dropped to 10.7 V at the amp... thats sure to kill power output, so i bet it would have pushed out another 200-300w if the amp was recieving the full 14.5... Output power is affected by input power even if the amp is fully regulated, you will ALWAYS make more power with any amp at 14.5v then you will with 12v

[pimp86LX]

lol your going to laugh......Im using an audiovox rampage 300w.

it has a LPF 350-50hz, bass boost and internal cooling fan. :) i was looking for a cheap solution to power to my sub and boy-howdy this amp is a deal for $150can new w/warrenty

I was very suprised. I was expecting very shitty stuff but it turns out it does the job just fine

[AccordEpicenter]

yeah... i never liked audiovox, ive had alot of their stuff and it always broke. I had a profile clarus cl400... 300wms into 4 ohms bridged and the thing put out great power for the money (like $125) and i sold it to my friend who is currently running it at 2 ohms bridged, which the minimum its designed to handle is 4 ohms and it hasnt smoked... yet... it gets damn hot tho

[pimp86LX]

Check it out: I found this sweet program that will graph your subs performance based on the sub specs and box design.

heres how a sealed 1.0^3ft box and my sub will perform

http://www.angelfire.com/indie/accord/images/boxnumbers.JPG

the smaller curve is impedance and the larger SPL

[AccordEpicenter]

yeah some speakers are soo reactive that even tho they are 4 ohms they can be soo inductive so their impedance can swing from like 2-12 ohms or somewhere in there... The inclosure has ALOT to do with it too