• 04-01-2009, 07:34 PM
    noidle22
    wiring up a kinda complex system. any help please
    Hey, hows it going.

    I recently obtained a fairly old Realistic MP-80 amplifier (mono, 80W, 4 ohm) and i want to install it into sound system. i basically want to use it to power a Optimus Pro SW-12 subwoofer (150W, 8 ohm) (itll be massively underpowered, i know, but anything is better than the 10 watts im running it on now). The problem i have though, is that the optimus sub has 2 sets of spring clip terminals as the input, instead of just one set. and my amp is only mono, so therefore i can only use one of the two inputs on the sub. i hope you can visualise what i am saying.
    i dont know how to combat this situation. i am thinking that because the sub also has two outputs, wiring up only one input, (if that would work), would result in only being able to use one output. that is ok, cos i have 2 Teac 2 way mids i want to use as well and i can wire them in series or parallel.

    it would be greatly appreciated if anyone could give me some advice or help, about anything i have described. thank you.
  • 04-01-2009, 07:44 PM
    bfalls
    I'm trying to visualize your sub. A model number would be helpful. What it sounds like are speaker level inputs designed to accept your receiver's main (L, R) speaker outputs into the sub's input terminals and the main speakers are connected to the high-pass outputs. The sub will play the low frequencies and pass the mid/high frequencies to the main speakers.

    You should be able to connect the sub-out RCA connector from the receiver to the M-80s RCA input and connect the speaker out from the amp to one of the subs input pairs. Since the sub-out is mono, you shouldn't compromise anything.

    If connecting to a stereo receiver, connect as I said in the first paragraph. Connect the L/R speaker cables to the subs two input pairs and speakers to the subs output.
  • 04-01-2009, 08:57 PM
    RoadRunner6
    Here are the specs. It is a passive sub with a crossover set a 200Hz and a low and high pass filter thru the speaker in and out connectors.

    SPECIFICATIONS
    Frequency Range .................................................. ............................29 Hz–200 Hz
    Power Handling.......................................... .......................................100 Watts RMS
    Maximum Power .................................................. ......................................200 Watts
    Sensitivity .................................................. ...................................... 88 dB @ 2.83 V
    Impedance .................................................. ...................................Nominal 8 Ohms
    Speaker .................................................. ............................ 12-Inch, Dual Voice Coil
    Crossover Frequency ............................................... 200 Hz with Built-In Crossover
    (Low-Pass Crossover for Internal Speaker)
    (High-Pass Crossover for External Primary Speaker Systems)
    Connections .................................................. ...............................Push-In Terminals
    Enclosure Type .................................................. ................................... Bass Reflex
    Enclosure Finish .................................................. ...............Black Wood Grain Vinyl
    Dimensions (HWD) ......................151/4 ¥ 17 ¥ 16 inches (38.3 ¥ 42.8 ¥ 40.2 cm)
    Weight .................................................. ..............................................26 lb (11.7 kg)

    Is this is a home system or a car? Do you have a different amp for the other speakers?

    I believe these passive sub usually have a dual voice coil and you should run the mono power into both left and right channels on the sub.....I think.
  • 04-01-2009, 09:13 PM
    noidle22
    http://www.herminlalefar.com/sellabl...DSCF5028_O.jpg

    this is the sub i have. its epically old but it still kicks hard enough running on 10 watts to feel at the other end of the house.
    it has 2 inputs, as i said, left channel and right channel, and 2, corresponding i think, outputs. what you said is right, it passes the high frequencies to the outputs. this is the rear view of my amp:
    http://www.aaaseller.com/imgs.asp?im...lor=60c060.jpg (pic wont show for some reason, go to link if you want to see it)

    as you can see, there is one output for speakers from the amp and the sub requires 2 sets of inputs. i just made this post to make it a bit clearer.
  • 04-01-2009, 09:22 PM
    noidle22
    this is just a home system. i am doing as an experiment kind of, just to see if i can make it work. i was running it off a cheap GM stereo, 10 watts per channel, and was using the left and right from the stereo to power the sub, and then using the subs two outputs to run some teac 2 way's. and, i was using the left channel of the stereo AS WELL to power a MTX 150 watt car sub. a bit risky, but it was working fine. i was getting pissed off with the mega distortion at high volume, so i got this amp off my uncle (Realistic MPA-80) to try and thump it a bit louder :)
    how do you run the output from the amp, which is mono, into the sub, which requires two channels?? do you split the wires to run into both terminals? eg. split the positive wire running from the amp into two and clip one into the left positive and one into the right positive?
  • 04-02-2009, 12:03 PM
    markw
    Two thoughts, no guarantees.
    1) From your first post,the MPA-80 appears to be safe for four ohm loads. Also, it seems that each side of the speaker is eight ohms. If those two sides of the speaker inputs were connected in parallel (red to red, black to black), that would present a four ohm load to the amplifier; Problem solved, as long as the amp is truly stable under the duress that very low frequencies can put on an amplifier.

    2) If all else fails, simply connect the amp to one set of input terminals. You only have one channel of information to begin with. You'll send all 80 (or whatever it is @ 8 ohms) watts to one channel and lose nothing.