Mono AMP with 2 wiring outputs to two 2ohm dvc subs?

Policies, Updates and News

Policies, Updates and News
What's going on in these forums and in the electronics industry

Mono AMP with 2 wiring outputs to two 2ohm dvc subs?

  • I've been here

    I can't seem to find exactly what I'm looking for. My amp is only 1 ohm stable, so I don't want to try for 0.5 ohm.

    Does anyone have a diagram for what I need?

  • I am guessing it would be about like this?

  • Correct, like this.

    However, that's but one piece of the puzzle. you need to get the gain set properly as well. Then if the subs are in a ported enclosure, a subsonic filter should be set no further than 5Hz below the tuning of the enclosure, to protect the subs.

    May I ask the model number of the subs and amplifier being used, as well as the size and type of enclosure?

  • Hate to say, I didn't buy from crutchfield this time. Only thing I bought was the amp, but I didn't find one in my price to go with the subs.

    Subs - Two Fosgate P2D2-15

    Box - Ground Shaker ST 2 15-BLACK

                 Dimensions: 8.25"TD x 11.5"BD x 36.25"W x 17"H

    Amp - Hifonics HFI1000.1D

    This is going in behind my seats of my 2013 F150 (regular cab). I'm hoping to be fine with this amp, because all the reviews on it are pretty good. It's not CES certified, but reviews are showing it's the true wattage. It may slightly under power the subs, but that's okay with me until I can get a really good amp.

  • Subs and box is brand new btw, but they wont fit my friends truck, so he passed them down to me :P

  • No, that amplifier isn't likely to produce rated power. It's got an 80AMP fuse, so for it to produce rated power, it's got to be 87% efficient and a solid 14.4V input voltage. Chances a re quite high that your car's electrical does not hold at 14.4V nor the amp being quite that efficient.

    A fair amount of testing has been done to some Hifonic amplifiers using using tools ranging from the SMD DD-1, DD-1, SMD AMM-1, and O-Scopes. The end results were that they do NOT produce rated power, at least no cleanly.

    That said, the use of the DMM method for setting gains is out the window. You're pretty much left with setting the gain by ear USING TEST TONES. This method is actually very accurate, however, it can be hard on any speakers/subs asked to play the test tone. So, it's not my first recommended method, as it can damage the equipment, not to mention the hearing of anyone in or very near the vehicle.

    What you do is set the volume of the stereo at 3/4 or the loudest you ever listen to it (using the lower value and never dialing past this point afterwards), then set the sub volume control  of the stereo to it's maximum level (if applicable), set the crossover's to through or the highest LPF setting , set the HPF's to their highest setting, or disconnect any full-range speakers, then have a helper play the test tone while you are at the amplifier ready to set the gain. Dial up the gain until the pitch of the test tone changes, then back down until it cleans up again. One can clearly hear when this happens, so it's quite simple. Once set, have the help end playback of the test tone and lower the volume.

    This should take no more than 10 seconds, from once playback of the test tone begins.

    And wear hearing protection, both you and the helper, as it is going to be quite loud.

    Also, the enclosure is a little on the small side, so use some polyfil in it. 1 pound of poly fill per cubic foot, so pretty much put 1.5 pounds in each chamber, stuffed in somewhat loosely.

    Oh, and don't read too much into CEA certification, I mean sure it's nice to see such, but that merely means an amp can produce rated power at 4 ohms with a 14.4V input voltage. It doesn't mean the amp can produce rated power at 2 ohms, 1 ohm, .5 ohm or with less than 14.4V power to the amplifier. Many quality amps are not CEA certified and are rated to produce their power at 13.5V or even 12.5V input power.

  • But is the amp okay to use for now? Also, which amp would you recommend?

  • Yeah, you can use the Hifonics, I'm just letting you know it's not going to produce rated power, though it may well prove to be "enough" power for you for a while. I'd expect that Hifonics to be capable of producing around 750-800RMS@ 1 ohm in your car, so at 2 ohms, more like 600RMS@2 ohms.

    Now if your car's electrical system could hold at 14.4V, then the amp may produce very near it's rated power, but again, an OEM electrical system won't do such.

    What would I recommend? Depends greatly on your budget. You're looking for an ideal 800-900RMS@2 ohms.

    It is recommended to be able to feed subs at least 70% of their rated power, which that Hifonics should surely do. It is also said that going from 70% rated power to 100% rated power doesn't yield but 2dB in gained output, which is noticeable, but not usually significant to most.

  • Thanks for all the info, but I still need help with how to wire it. I saw the diagram, but I have two outputs for speaker wire and the diagram only has one. What do I do?

  • The amplifier may have two terminals, but they are internally wired in parallel for ease of connecting multiple subs. You can use either + and - terminal on the amplifier.