I'm building a new system using a SEAS 4" Full Range and a SEAS 6" woofer. I'm trying to determine the point on my preamp volume control that represents enough power to blow the 4" driver (coil melt or cone damage) so that I don't get to or cross that boundary during listening sessions. 90% of the time I'm probably listening in the 65 to 85dB range, which I know isn't close to the power handling of the speaker. However, I'm sure we've all experienced a time or two when very loud is very good and inhibitions aren't properly in place. 🙄
The speaker has a 3.3ohm voice coil resistance. Handles 40W long term and 100W short term. If I use the equation of W = V-squared / ohms then it looks like somewhere around 11V amp output is the stopping point. I'm wondering if I can put my voltmeter on AC mode across the speaker terminals and figure out where the volume equals 11V and don't exceed that number on the preamp. (I also have an oscilloscope if that is a better tool to use.)
I'm asking in the Class D section because I'm using an ATI AT524NC amp that puts about 350W into 3.3 ohms at full tilt.
The speaker has a 3.3ohm voice coil resistance. Handles 40W long term and 100W short term. If I use the equation of W = V-squared / ohms then it looks like somewhere around 11V amp output is the stopping point. I'm wondering if I can put my voltmeter on AC mode across the speaker terminals and figure out where the volume equals 11V and don't exceed that number on the preamp. (I also have an oscilloscope if that is a better tool to use.)
I'm asking in the Class D section because I'm using an ATI AT524NC amp that puts about 350W into 3.3 ohms at full tilt.
The volume control does set the gain, but it doesn't set an actual maximum VAC limit. The output is still proportional to the input.
Only clipping will set a hard limit. You might want some speaker fuses instead, especially if others will be operating this.
Also you would need a wideband true RMS meter for measurement, which few are.
What is your source? If its max VAC output can be defined, then divide that into your 11VAC to find the max total gain you want.
Next subtract the power amp gain from that, and then test the preamp volume control behavior for the remaining amount of gain.
For example, if your source puts out 1.1VAC max, then 11VAC/1.1VAC =10 times ( +20dB ) overall system gain.
Then if your amp has say 22dB gain, then 20 - 22 = -2dB gain left for the preamp.
So adjust the preamp for a max line stage gain (actually loss) of -2dB (relative to the 1.1VAC source level),
which is about 0.8VAC, and you're set.
Only clipping will set a hard limit. You might want some speaker fuses instead, especially if others will be operating this.
Also you would need a wideband true RMS meter for measurement, which few are.
What is your source? If its max VAC output can be defined, then divide that into your 11VAC to find the max total gain you want.
Next subtract the power amp gain from that, and then test the preamp volume control behavior for the remaining amount of gain.
For example, if your source puts out 1.1VAC max, then 11VAC/1.1VAC =10 times ( +20dB ) overall system gain.
Then if your amp has say 22dB gain, then 20 - 22 = -2dB gain left for the preamp.
So adjust the preamp for a max line stage gain (actually loss) of -2dB (relative to the 1.1VAC source level),
which is about 0.8VAC, and you're set.
