posted
I want to match up my two 2500d's, which I know basically how to do, and its not just look @ the gains and see how close they are...
I have a DMM and I want to make sure that when my amp is @ full tilt I get a certain amount of AC voltage from the speaker terminals; some say 90v and some say 120v, but we can talk about that later.
I want to test this WITHOUT a sub in the equation... is this possible? or do I need to have resistance (@ a specific impedence, namely my subs which would be .8ohms) to figure it out... thx
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posted
You can match the voltage without subs hooked up. Run the same signal (test tone) to both amps at the same time, measure AC voltage on one and then do the second amp adjusting the gain until the voltage matches.
You're only matching the voltage and not power, so it doesn't matter if the sub is in circuit or not. The amp voltage will drop some when the subs are hooked up, but they will both drop the same amount and still be matched.
Posts: 2575 | From: GA | Registered: May 1999
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thx jc2, but what I want to do is get an exact PEAK output reading from the amps... i know some big names get their voltages to a certain point and that is where they burp it at, like 90vac or 120vac, whatever...
i'll probably put my system back in tonight and go from there, see if I can get that correct #
-------------------- back in the 50's... Kicker is 'Livin Loud' Marriage soon, new house in the works, new baby, and no money! Posts: 2497 | From: Gardiner Maine 00420ville | Registered: May 2000
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actually it doesnt matter if the amps are level matched or not, so long as they are playing the exact same thing.
Ideally they both should be just below clipping, even if they aren't matched.
Remember that if both amps are playing the same material, you are only changing the amplitued, and that the signal is 100% additive even if the amplitude is different.
What is critical is making sure that the material is 100% identicle
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-------------------- 2006 Bass Race 149.9 World Finals 2nd place H.O. Alts FI If you dont like what I have to say, just contact Boomingcreation he will erase it for you Posts: 16058 | From: tx | Registered: Dec 2003
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The voltage isn't really important. You are better off to use a oscilloscope and check were your amp is clipping. Also check the headunit to see what volune it clips at. A small amount of clipping will increase SPL. But be warned clipping is the biggest killer of speakers.
-------------------- Street C 147.1dB 1 X ddz1 1 X AUDIOBAHN 18 Posts: 14 | From: Australia | Registered: Aug 2004
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In order to be able to set your gains correctly (maximum level before clipping) with a DMM you need to know the impedance your amp will be seeing when its all hooked up.
To find the correct voltage is pretty simple.
Say you want 2500wrms and you are showing your amp a 2ohm load.
You take the square root of 2500*2 and thats your AC voltage.
Eg. 2500*2=5000
sqrt of 5000=70.71
So the voltage you are looking for is 70.71. Just hook your DMM up to the output terminals on your amp and turn the gains until you get 70.71 or as close to that as you can.
Changing the impedance your amp sees will change the number by quite a bit so you need to know your sub configuration before you can figure out the AC voltage.
Also, make sure your subs are disconnected from the amp when doing this and make sure you have all equalization, crossovers, etc. turned off or make sure the tone you are playing is in the area where the crossover will not effect output.
Eg. If you have your subs crossed over at 50hz play a 40hz tone not a 60hz tone.
Going above the correct AC voltage is fairly dangerous even if its just a little bit when your dealing with power levels like 2500wrms so try to be fairly accurate or you will see the magic smoke after a few burps.
I should also say that this does not tell you where clipping starts. It just gets you the amount of wattage you plugged into the formula at a given impedance.
So, if your amp is rated for 2500wrms and it can't meet those specs, you will be into clipping at that voltage. Your amps will probably be fine but some low end brands tend to exagerate their specs so you need to watch for this.
And this concludes today's lesson. Posts: 340 | From: Trenton, Ontario | Registered: Dec 2003
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posted
When you say "I want to get 90v or 120v from the terminals" you are not taking into consideration the fact that all amplifiers have different power outputs, as Frosty said either you pick a goal or you pick the highest possible voltage.
1: When reading a 60hz tone, any DMM will provide you a moderately accurate RMS voltage reading.. Use this to match your amplifier outputs to each other.
2: To run over the clipping point of your amplifier is a topic of debate-> Some people say a square wave holds more power so you need to hit it just right. Others contend that a square wave contains energy over the fundamental wave only in the form of harmonics and that this energy contributes very little to the actual SPL reading at the fundamental frequency.
ShadowStar
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It's all about knowledge, love and respect. Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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