quick gain question

[ultimate157 5,000+ posts]

Here's the formula you'll need ...Sqrt(Power*Resistance) = Voltage

(i.e. If you bridge a 4 ohm subwoofer to your amplifier that is rated to produce 100 RMS @ 4 ohms in bridged mode, you would want Sqrt(4*100) = 20 volts)

Shouldn't Resistance be Impedance in that formula? I have a 4 ohm impedance subwoofer that reads 3.4 ohms resistance. Should I use 4 or 3.4 in the formula ?

Also, assuming thermal power handling is OK with the subwoofer, its OK to turn the gain up as far as I want as long as its not clipping, correct? I will be using an oscilloscope to make sure there is no clipping with a 50hz 0db tone.

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[thch 10+ year member]

yes nominal impedance. I didn't want to use "impedance" in the forumla as its not technically correct but the differences aren't important because nominal impedance is treated as a resistance.

as for power handeling. you must ensure the speaker does not overheat or overexurt. so long as you do this you can clip all you want with the only penelty being distortion. still, with no thermal probing or means to measure excursion, this goal may be difficult. so use the oscope and assume that the manufacturer accurately rated the woofer for your application.

 

[iceteebone 5,000+ posts]

Shouldn't Resistance be Impedance in that formula? I have a 4 ohm impedance subwoofer that reads 3.4 ohms resistance. Should I use 4 or 3.4 in the formula ?


Also, assuming thermal power handling is OK with the subwoofer, its OK to turn the gain up as far as I want as long as its not clipping, correct? I will be using an oscilloscope to make sure there is no clipping with a 50hz 0db tone.

you'll be fine using impedence because when playing music, you'll have impedence rise.

 

[ultimate157 5,000+ posts]

I guess Lanzar's don't like 4 ohm loads. I put the O-scope on it, and I actually had the gain set (by ear) right where it had to be. Perfect sin wave.

I also checked the voltage on the incoming B+ and speaker terminals. I was getting 14.03v from the b+ and only 42.3v on the speaker leads. Which @ 4 ohms is only ~450w. This amps rated for 700w @ 4 ohms //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif//content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif