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How do you wire a stereo amp for sub

Discussion in '80-Series Tech' started by lx450landcruiser, Dec 16, 2003.

  1. lx450landcruiser

    lx450landcruiser Moderator

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    i just ordered an amp and a 10in sub for a custom set up in the rear of my cruiser but to be honest with you i have no clue how to wire an amp.

    i know some of you guys have them so how would i go about doing this?
    can i just run the pos and neg wires from my stock sub in the lx and run them to the amp?

    thanks mike
     
  2. WolfpackTLC

    WolfpackTLC

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    Sure, if you like electrical fires. NO. You can't. You'll need @ least 8 gauge cable from the positive terminal of the battery to the amp. FUSE this wire. You'll need a ground cable of corresponding gauge to the neg terminal. DO NOT skimp on wire or the ground position. Ground to the frame whenever possible. Ground all amps @ the same point to avoid ground loops. Use the largest gauge wire you can afford. You can always get a distribution block to downsize the wire if you need. Run the power wire through a grommet in the firewall. Can't find one? Make a hole and use a grommet. Nuf' said for now.
     
  3. bkgiii

    bkgiii SILVER Star

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    I concur...8 Ga minimum..I run 4 Ga from battery to 100A circuit breaker, through the firewall, to a distribution block, then to fuses, then to the amps.

    What size is the amp?

    Also, use 'remote' wire to power up the amp when head unit is switched. The head unit should provide this wire, and the amp hopefully has a corresponding wire or terminal. Agree on the grounding, too: all wires, wherever possible, to common frame ground.
     
  4. 97cruiser

    97cruiser

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    We're gonna need to know which model amp and sub you have. SVC sub?(single voice coil), DVC (dual voice coil)? 2 ohm amp or 4 ohm amp? definately get 4 ga. power and neg. leads. If you ever decide to add an amp you will need 4 ga. , 8 ga. wont cut it for 2 amps and you don't wan't to re-run your leads so play it safe. Is this a dedicated subwoofer amp? If so, then you will most likely want another amp in the future since the aftermarket sub and amp will be WAY out of balance with the stock system and you will be turning down the gains on your amp thus not realizing the full potential of your new sub and amp.....Oh and don't ground to a painted surface,scrape that paint off!

    Just my .02, Vince
     
  5. lx450landcruiser

    lx450landcruiser Moderator

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    alright i have a 10" Subwoofer with Dual Voice Coils, 450 Watts, 70-oz. Magnet, 20-1200 Hz Response, 2" Coil, 95dB Sensitivity

    th amp is
    500-WATT 2-CHANNEL PYRAMID PRO PLUS SERIES BRIDGEABLE AMPLIFIER
    MOSFET power supply for cooler operation, maximum efficiency, quicker response. Peak output: 250 Watts x 2 (stereo) or 500 Watts x 1 (mono bridged). Bass boost control pumps up to 18 dB at 60 Hz. Treble boost control adds up to 12 dB at 10 kHz. Signal/noise ratio over 95 dB. Frequency response: 10-30 kHz. Size: 10"W x 2.5"H x 9.5"L.
     
  6. 97cruiser

    97cruiser

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    Ok I'll give this a shot. I couldn't find much info on your amp so I will assume there is a HI/LO pass crossover on it, set it to LO this will send only low frequencies to your sub. If there is a frequency adjustment set it to around 30hz. to 50 hz.(you can play with this adjustment later for best sound).If there is a gain control adjustment set it to about 1/4 so you dont send all available power to your sub when you 1st turn it on (or KABOOM).

    Now the wiring. Run 4ga. wire from battery to positive on your amp with a fuse (20 amp? manual will cpecify what amperage) about a foot from your battery. Next run a 4ga. ground wire from your ground (-) on your amp no more than 2 feet to a clean metal surface on the body of your truck. You will have a connection called (remote) on your amp, connect this to the remote wire from your head unit,typically the baby blue one. Then run your rca's on the opposite side of the car that you ran your power wire on. Try not to cross rca's and power or you will introduce noise (static) into your system. Now the speakers. You have a (+) and (-) for the left channel and (+) and (-) for the right channel. Connect the left (+) to the sub's (+) and the right channel (-) to the sub's (-). Now crank her up and enjoy!

    Vince
     
  7. WolfpackTLC

    WolfpackTLC

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    Pyramid? Ugh. Last I remember (this was circa 1996-1997 ) Pyramid didn't exactly make stellar amplifiers... You might want to look @ another brand when funds allow.

    J
     
  8. lx450landcruiser

    lx450landcruiser Moderator

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    so if i were to follow the stock subwoofer wire back to the face plate and run a high guage wire from that to the amp would that work or am i looking at a fire still? also what probs do you guys see with this since if i remove the factory lexus head unit it wont work least thats what the security system says.

    thanks mike
     
  9. 97cruiser

    97cruiser

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    Mike, Sorry I misunderstood your original post. You want to run this new amp and sub in conjunction with your stock head unit? Aint gonna happen. If you do rig-a-ma-jig it up somehow you wont' be happy with the sound quality either. I didn't want to say it in my earlier post but since it has been mentioned, pyramid is very sub-par equipment. You would be best served sending back the amp and saving about 300 to $400.00 and getting a 5 channel amp and another $200.00 for a aftermarket headunit with a dedicated 4-volt preout for the sub. Keep the sub you have and build your own enclosure in the stock location or where ever.

    Vince
     
  10. lx450landcruiser

    lx450landcruiser Moderator

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    im not looking to power any thing from the factory system just the sub
    i bought the amp to wire the sub thats it. so could i run the wire for the factory sub to the amp then power the amp from battery and then run wire to the new sub?

    thanks again
    mike
     
  11. Rookie2

    Rookie2

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    I just rig-a-ma-jigged a Fosgat Punch 250, keeping the factoy LX head unit. The problem I had was I couldn't get it to work by tapping into the positive signal and common signal ground at the head unit. I had to pick up the signal off the rear speaker lines, post factory sub signal, into RCA converter and then to sub. Sounds pretty good after working with the gains on the amp. Let me know if any of you all think I've jerry-ed it up too much/got any suggestions. I don't want to start a far.

    Concurence on the power and ground hook-ups. You can get decent sub wiring packages at Walmart for 20 bucks.

    You might call your local dealer to fax complete factory stereo wiring diagram and color codes. Must have. This things got more wires than Silicon Valley.

    Rookie2
     
  12. 97cruiser

    97cruiser

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    Yes you can get a signal from the stock amp to an aftermarket amp. Is that the correct way to do it? No. Are you gonna be happy with the sound the sound you get from this investment? I really doubt it. Is the equipment you just spent hard earned money on and configured in this manner living up to it's potential? Definately not.

    I guess I'm from the "old school". Do it right the first time or don't do it at all.

    Just my .02, Vince
     
  13. lx450landcruiser

    lx450landcruiser Moderator

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    how big of a box would you suggest for a 10 inch sub ?
     
  14. Sorry Dog

    Sorry Dog

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    Different subs will have different recommended box sizes. Also the type of box will affect the size too as ported boxes require more room than sealed and bandpass require even more. Which box you should choose has more to do with your listenling style. Ported boxes gain you 3 or more DB for the same power but the sound often isn't as crisp. Anyway, a guess would be .6 to 1.1 for sealed and .75 to 1.5 for ported. You didn't say what kind of sub you have, but you really should not scimp here. Sealed boxes are usually the choice for "adult listeners" but will require more power for higher volumes.
    Pyrimid used to be the basement of car stereo stuff but from what I hear their quality has improved somewhat, however, I don't have recent 1st hand knowledge. Cheap amps will often fudge on their numbers and be suspeptable to feedback, overheating, and some won't last long at 2 ohms plus 95 is a low SN ratio. The 250 watt number is probably a max power number which is bullshit. Real power ratings are done in RMS (root mean square) and at .1 THD (total harmonic distorsion) so your amp is probably 100-125 rms @ 4ohms. If you don't run it hard you'll probably be OK. If your just running 1 10" DVC then you got 2 ways to wire it. Wthe amp will have to be bridged meaning running 1 channel in mono. If you wire both contacts paralled directly to the amp, that will give you 2 ohms and more power, but greater stress and heat on the amp. If you run in series, the - of one contact to the + of the other and the other two to the amp, then you'll have 8 ohms and draw less power from the amp. Your amp may have speaker level imputs but if not, you will need a speaker line converter to convert radio's speaker outputs to a RCA type low level inputs.
    You may out volume your factory full range speakers but if you don't replace them now, you can help them out by getting some high pass bass blockers to wire to them will which increase their volume slightly before they distort badly.
    I like to keep factory units for the look too, but the problem is when running a sub you often to adjust to sub output level according to the type of music and most aftermarket unit let you do this easily without needing a separate EQ or manually adjusting the level on the amp.
    A couple of good places for getting stuff and especially good prices on wiring stuff is:
    www.thezeb.com or
    www.justwoofers.com