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Featured Replies

Are the merlin mono blocks .5 ohm stable?

usamps dont reccommend it but with the right electrical system, yes.

well I got to Fi SSD D2 going to them and they are just fine they only get warm

FYI the DCR of the FI is .7 so that's pretty close to the .5

After around 30 mins of cracking the volume i feel my amps and they are warm

they would be 10xs cooler if i put the back seat down but i wanted to know how much abuse these amps can take..... and yes they take it well

I beat on my amps like a rented mule and they keep on smiling...

I'm about to up my subs since the RMS of the SSD is only 800 (I am getting a Fi Q maybe) then i can really unleash the beast...

well I got to Fi SSD D2 going to them and they are just fine they only get warm

FYI the DCR of the FI is .7 so that's pretty close to the .5

After around 30 mins of cracking the volume i feel my amps and they are warm

they would be 10xs cooler if i put the back seat down but i wanted to know how much abuse these amps can take..... and yes they take it well

I beat on my amps like a rented mule and they keep on smiling...

I'm about to up my subs since the RMS of the SSD is only 800 (I am getting a Fi Q maybe) then i can really unleash the beast...

DCR is not impedance so I'd guess that yours are closer to 1 than .5, but either way.

I'm running my Xterminator @ an impedance of 0.67 ohms (before impedance rise), and it doesn't even break a sweat.

I am sure the Merlin series will have no trouble.

Although, warranty won't cover it. ;) Remember that.

I run my amps in pairs strapped to 1 ohm coils without any problems. But, I have also tested my impedance, and it actually only dips to 2.2 ohms per coil with the system in the enclosure. If I change subs again, I am going to drop down to .7 ohms on each strapped pair and see what happens.

Brian

I run my amps in pairs strapped to 1 ohm coils without any problems. But, I have also tested my impedance, and it actually only dips to 2.2 ohms per coil with the system in the enclosure. If I change subs again, I am going to drop down to .7 ohms on each strapped pair and see what happens.

Brian

That makes no sense.

You run your amps in pairs per one ohm coil, or in lamens terms .5 ohms per amp, than in the next sentence you say your impedance dips to 2.2 ohms per coil? Are you saying that each amp is running .5 ohms or 1.1 ohms?

it actually only dips to 2.2 ohms per coil with the system in the enclosure.

That makes no sense.

You run your amps in pairs per one ohm coil, or in lamens terms .5 ohms per amp, than in the next sentence you say your impedance dips to 2.2 ohms per coil? Are you saying that each amp is running .5 ohms or 1.1 ohms?

When you put a sub in an enclosure, you get an impedance rise. . . .in my case, the actual lowest impedance of each coil with the sub in the enclosure and power running through it is 2.2 ohms.

So, while most people woudl look at my setup and think I am running each amp at .5 ohms, I am actually running each amp at 1.1 ohms.

Brian

  • Author

So what causes the impedance rise when putting a driver in the enclosure? Is it just from the addition of speakerwire from the sub to the amp?

Edited by Puggsley456

An easy explaination: Impedance rise is due to the fact that the input to the subwoofer coil is AC, and the subwoofer coil has a resistance and reactance (it is a coil). The speaker's impedance varies with frequency even in free-air with a peak at Fs. Put the speaker in a box, and you now have the Fs of the driver, the Fb of the box (impedance hump on each side of Fb) and the change in the driver reaction to input power due to the enclosure. All these contribute to the actual impedance the amp will see at a given frequency.

An easy fairly acurate way to measure "impedance" is to wire a high power resistor in series with the driver. Input enough power to get some air flowing in the enclosure, and measure voltage output of the amp and across the resistor for single frequency tones.

With these voltages you can find:

Current = Votlage across the resistor / the value of the resistor

Voltage across the driver = votlage at the amp's terminals - voltage across the resistor

driver impedance = voltage across the driver / current

This is a fairly accurate way to measure the impedance.

You can get a better measurement if you have a variable resistor that can handle high power:

For each frequency, measure the voltage at the amp's output and across the fixed resistor that is in series with the driver. Replace the driver with the variable resistor. Adjust the variable resistor until the voltage across the fixed resistor is the same as it was while the driver was connected (keep the same voltage on the amp's output). Once the variable resistor is set correctly, remove it from the circuit and measure the resistance. That is a close estimate of the impedance the amp sees when the driver is connected.

These measurements are also handy for finding your true box tuning. If you plot the impedance vs. frequency, you will see two humps in the impedance with what should be near your lowest impedance between them. That low is the port tuning frequency.

Brian

  • Author
.5 ohm is not a problem

Good to know thanks. Are we talking a .5 dcr or .5 nominal?

Any ballpark ideas on output or amperage draw at that impedance?

Edited by Puggsley456

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