M100 bridged @ 3ohm

paulbfd · Post by **paulbfd** » Fri Jul 20, 2007 12:38 pm

Could anyone tell me what sort of power will an M100 bridged into a 3ohm load? It'll be happy enough to do that, right?

1moreamp · Post by **1moreamp** » Fri Jul 20, 2007 1:35 pm

At 4 ohms mono it is rated at 355 watts at 12 volts and 455 watts at 14 volts.

So a fair guesstimate would be around 500 watts at 3 ohms mono at 14 volts power feed

Post by **fuzzysnuggleduck** » Fri Jul 20, 2007 2:22 pm

Doesn't the PG literature state the the M series will produce pretty much the same power at 2 ohms as it does a 4 ohms? Isn't this due to some voltage limiting or what not?

1moreamp · Post by **1moreamp** » Fri Jul 20, 2007 2:47 pm

I quoted the PG site pdf file for this info bridged at 12 and 14 volts, So they might be fibbin but its what they printed in the pdf ?

You own one of these don't you ?

Post by **fuzzysnuggleduck** » Fri Jul 20, 2007 3:30 pm

From http://www.phoenixgold.com/webfaq/M.htm:

Q: How much power does my M series amplifier make at 2 ohms bridged?

A: The continuous power at 2 ohms or 1 ohm bridged remains about the same as it was for 4 ohms bridged.

When designing the M series amps, we wanted a design that made its best power at normal loads. By normal, we mean 4 ohms bridged. We know that no matter what we say, or how loud we say it - People will still hook the amp up to lower impedances trying to get more power. So, our number one goal is that the amp continue to operate at lower impedances. The only way to do that is to limit the continuous power output of the amp when it's hooked up to lower impedances. Here's why -

Wattage is equal to voltage times current. Running the amp at 2 ohms bridged means more output current. Current makes heat. We can't allow the amp to make more heat than the heatsink can reasonably dissipate. With the addition of cooling fans, the heatsink can manage a more heat than what's generated from a 4 ohm bridged load so there's some room for a bit more power. Here's how we limit the power increase to what's manageable:

The M series amps have a circuit that detects the amount of current leaving the speaker terminals. If the current is high enough, AND lasts long enough (longer than 50 milliseconds), the circuit limits the amount of voltage that the power supply can produce. This in turn limits the power output of the amp. So continuous power output remains about the same with the power composed of more current and less voltage.

There is a bright side to all this. Remember I said that the excess current demand had to last longer than 50ms. The dynamic peaks in most music last less than 20ms. Therefore, the circuit never has a chance to affect the power supply voltage for musical peaks. All this means that the amp is allowed to make more power with musical peaks while continuous power remains about the same. You could say that the "headroom" of the amp is increased.

If you want to run the amp 2 ohms bridged, go for it. Just understand that it will run warmer (fans may be necessary) and will pull more current from your car to make those musical peaks (add more capacitors). I wouldn't recommend running it 1 ohm bridged. The amp will shut down (red LED) if the output current gets too high (looks like a shorted speaker).

1moreamp · Post by **1moreamp** » Fri Jul 20, 2007 3:52 pm

The PDF file in the manuals section says different, thats where i got the numbers from. C

paulbfd · Post by **paulbfd** » Fri Jul 20, 2007 8:40 pm

That'll do for me, I'm just exploring all avenues for my new install using the M44 & M100.

Been eyeing up a W6v1 which is a dual 6, didn't want to risk breaking anything at 3ohms.

Post by **fuzzysnuggleduck** » Fri Jul 20, 2007 9:14 pm

paulbfd wrote:That'll do for me, I'm just exploring all avenues for my new install using the M44 & M100.

Been eyeing up a W6v1 which is a dual 6, didn't want to risk breaking anything at 3ohms.

I don't think breaking anything is a problem unless you pull a dumbass move... much like I did. I have a 2 ohm bridged load which was pretty much at maximum for music volume due to over-line driving (which I was planning on fixing but simply forgot), then I RTA'ed the system before turning down the line driving and the 1-20Hz range of the RTA curve made the M100 cry and did damage to the amp

It's going to see Pappa Cecil soon and all will be well again

1moreamp · Post by **1moreamp** » Fri Jul 20, 2007 9:39 pm

marko · Post by **marko** » Fri Jul 20, 2007 11:35 pm

i ran my old m100 @2ohms mono for years and years with no issues what so ever, you just got to not do anything silly like mount it upside down and poor power supply/bad set up etc.. 3ohms mono will be a walk in the park