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Amp over headunit?

Discussion in 'Audio' started by personaltrainer, Feb 24, 2005.

  1. personaltrainer

    personaltrainer 1/2 ton status

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    Obviously an amp at 50x4 is better than your average head deck at 50x4. The question is, how much better? Trying to decide of I want to spend about $150-200 on a new amp to drive my speakers (polk sep in frnt, and polk 6.5s int eh back - or just buy an new headunti (which I need anyway) that has goodp ower in it and go w/o amp.
    next question - what head unit put out the most RMS?

    thanks
     
  2. Jonny-K5

    Jonny-K5 1/2 ton status

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    since you already want a new headunit, i'd just get a good one and run your speakers off there for now. you can always upgrade to an amp later on.
    not sure which ones have the highest RMS. most all of them have around the same max tho, so you just gotta look thru a few in your price range that you like, and see which ones handle more. ebay is great for this.
     
  3. Z3PR

    Z3PR Banned

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    I agree, get the head unit now. I like JVC and Clarion alot. Here's a pretty good deal on a Clarion It's last year's modle, so it's a heck of a deal.[​IMG]
     
    Last edited: Feb 25, 2005
  4. spearchucker

    spearchucker 1/2 ton status

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    If you're going to be cranking it then I'd have to say get a good amp. Nothing destroys a speaker faster than underdriveing it. A headunit may clip output signal, i.e. Direct Current=bad, whereas a good amp won't until a higher level. I say, in your case, work your way back, speaker, amp then headunit.
     
  5. Z3PR

    Z3PR Banned

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    Personally I'd get the head unit first, then the amp(s), then upgrade the speakers. Well, I'd probley do the amp(s) and speakers at the same time. Anyways, that's just my thinking.
     
  6. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    The first thing you need to do (and what is HARDEST for most people) is to stop believing the manufacturers claims!!!! ;)

    THERE IS NO SUCH THING AS A HEADUNIT PUTTING OUT 50W/CHANNEL!!!!!!!


    The process of creating THAT much power requires that DC current be converted to an AC waveform that can then be manipulated to produce lots of "gain" (i.e. WATTS)... When you look at the inside of a power amp, the majority of those large components in there are for that very purpose. The other side-effect of converting DC to AC is HEAT! Power amps have a lot of heatsink area because they need to dissipate the residual heat of that conversion process.

    NOW:

    Think about a typical headunit....7" wide, 2" tall..... where is all that circuitry going to FIT? Where will all that heat go?? The answer is that it doesn't fit....the 50W rating is bogus marketing. I can get into the specifics of how they can "legally" claim 50W...but the bottom line is that EVERY headunit on the market is limited to a "REAL" output of about 8 WATTS per channel.

    I don't have an electrical engineering background, but I'm sure those that do can explain about gain structures and amplification using only DC current and a 12V source... :dunno:


    Sorry for the rant, but this is one of my BIG pet peeves about audio companies.... and it makes it really hard for most consumers to get what they really want.

    The bottom line for you PersonalTrainer is that if you want 50W per channel, you should be buying an outboard amp... :cool1:
    .
     
  7. cochino12

    cochino12 1/2 ton status

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    Couldnt agree more. Plus the easiest way for you to blow/damage the speakers you have already spent good money on is to leave them underpowered.
     
  8. personaltrainer

    personaltrainer 1/2 ton status

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    I was aware of the "bogus" marketing and that is why I refered to RMS of the head unit and not advertised rating. I always heard that the true wattage of most of the headunits was something like 12watts or so. Either way it's not any where near 50!

    Looks like i'll be running the head unit that is in there (JVC) "50" x 4 on some polk sep. up front in the doors and 6.5 polk in the rear area with 1 10" no name speaker in a ported box running off of a 200 x 1 JL audio amp. Messed around with the head unit and speakers and was able to make it work again. we'll see how long that lasts!

    That's what I got so that's what I'll use.
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Yeah, RMS is one trick....

    Look at the frequency response they use when spec'ing power too....I guarantee it's not full-spectrum (20-20,000Hz)! They may even spec it ONLY at 1000Hz for 10ms duration!!!! :eek:

    Also, look at distortion numbers (probably high)

    There's all kinds of ways to make a "big" number...... [/sigh]


    .
     
  10. personaltrainer

    personaltrainer 1/2 ton status

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    Greg - your way over my head here! You right though.

    on another note. any idea what would make the speaker work for 2 secs while hooked up then turn off (only that speaker?) I'll try a few other speakers to that same wire to see if it's just the particular speaker but it seems funny that it would not make ANY sound at all, no?

    did that make any sense? It's been a long day!
     
  11. tuffdogstudio

    tuffdogstudio 1/2 ton status

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    Depending on what your listening habbits are, you may not need an amp for the speakers you already have but rather should spend money on a Subwoofer and amp for it. In my allbeit non-professional opinion, most folks just want their car audio to have enough volume to let them jam and enough bass to feel it in their seat.

    Getting a good quality head unit will drive the speakers you have invested in already, especially if you arent trying to get deep bass out of them.

    If you do go the amp route I would suggest you look at high quality amps.

    So basically get the head unit and then make some decisions as to the next step if one is needed.
     
  12. tuffdogstudio

    tuffdogstudio 1/2 ton status

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    Sounds like a bad wiring connection somewhere or a bad channel at the source, most speakers, even trashed ones will make some sort of noise when connected to signal, especially a speaker that didnt have some sort of significant blow-out with lots of fan-fare.

    I suggest you try another speaker on the source wire and if that dosent work, first check your wiring... then test the suspect source wire with a meter and see if is indeed passing signal.
     
  13. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Could be a blown voice-coil in the speaker causing a direct short. The deck might just shut that channel down when it happens.... if you have an ohm-meter, disconnect the speaker and measure the resistance across the + and - terminals of the speaker....you should see something like 4 ohms, but NOT zero.


    TROUBLESHOOTING 101:

    When you have a component that you are unsure of, the best thing to do is substitute a different component and try again. In this case, try a different speaker temporarily. If the problem goes away, the "original" speaker is to blame, but if the problem persists....the problem lies elsewhere.

    This is a great technique for finding wiring shorts too. Just run a "bypass" wire around the suspected bad wire and see if the problem goes away. That way you only have to rip out and re-fish the wire once you've PROVEN to yourself that it's truly bad/pinched/cut/shorted.

    [/schools out] :cool1:


    .
     
  14. hawglet

    hawglet 1/2 ton status

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    If it happens with more than one speaker hooked up only on one of the channels, that particular channel is probably overheating quickly or is shorting out inside of the deck itself. Like you said try another speaker in that location. If it happens that is probably the case, if not the speaker has some problem obviously, who knows what's causeing that though.
     

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