Car Amp and Sub specs: Plz explain to me :)

Discussion in 'Audio Visual' started by jinxhavoc, Nov 4, 2004.

  1. jinxhavoc

    jinxhavoc Member

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    Hey guys, im looking at buying an amp with specs like this:
    - Power/channel @ 4 ohm: 150 W RMS x 2
    - Power/channel @ 2 ohm: 230 W RMS x 2
    - Power output (Bridged 4ohm): 450 W RMS x 1

    I was wondering exactly what it all means, i know that the Watts is its Max power capacity and the RMS rating is its power rating for what its good for all day long. I know the channels can be bridged also but i dont really understand how and what the 'ohm's are? 2 and 4 ohms, whats the diff? Quality?

    Also how does this impact the Sub? Could i also run my other speakers off this Amp? -I have Lightening Audio 6x9's in the back and i am getting 6"s in the front.
    Thanks, Matt
     
  2. Volenti

    Volenti Member

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    Ok the scale kinda goes like this;

    Lies > damn lies > statistics > amplifier/speaker power ratings :p

    For amplifiers the RMS rating is the only thing you should care about, any other claimed power rating is less trustworthy than what comes out of the mouth of a used car salesman.

    Think of 4 ohm and 2 ohm as different "loads" on the amp, the lower the number the harder amp has to work and the more power it will deliver (if it is capable)

    Bridging is simply making the 2 amplifier channels work together to drive one speaker, since their working together they each see only half the load, and work harder and produce more power (4x the per channel rating in theory, usually 2x in practice)

    tri-moding the amp is possible but I would recommend a smaller seperate amp to run the speakers, it's really less hassle and makes for a better end result.
     
  3. break

    break Member

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    Using dictionary.com

    So, with that... lowering electrical resistance of a channel will allow more electrons to flow through the channel, hence why the lower ohm will produce more power. Note, not all audio gear will run at lower ohms than they are rated, and the standard ohms for most audio gear is 4ohms.

    You can buy gear that is 1ohm, 2ohm, 4ohm, and 8ohm... and using different combinations of these you can get all sorts of figures.

    The amp details you have put up I am assuming are of a Jaycar 2x150wrms Response amp. With that amp, you have two options. Run two channels at 150wrms into two separate speakers (maybe 6x9's, maybe splits, maybe just coaxial speakers... and if you want.... two subs), OR you can bridge the channels into the single speaker (ie. sub) and run the sub with a nice chunk of power. I would suggest the latter of the two options.

    Another thing to remember, its always better to over-power a speaker than underpower a speaker. The reason, you can turn down the gain on the amp... and keep a nice clean signal going to speaker, at its maximum stable RMS. So for example, if you were to buy a sub rated at 300wrms, and run the full 450wrms from this amp into it... that would be fine... but you would just have to keep the amps gain around 1/2 to 3/4 to keep the power levels suitable for the sub. This will help improve sound quality as the amplifier won't be anywhere near its clipping point at those power levels... so the sub will have a strong and clean signal to it, giving you excellent dynamics from the sub.
     
  4. OP
    OP
    jinxhavoc

    jinxhavoc Member

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    Thanks guys, that great info :)
    Matt
     
  5. flu!d

    flu!d Never perfect, always genuine

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    Actually, RMS power ratings can be fudged also,

    The power rating that counts is the 'Continuous' RMS power rating.
     
  6. FuK[NuTz]2k

    FuK[NuTz]2k Member

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    and even that can be fudged :p . well not so much fudged, but more adjusted so that people who don't care about the finer points won't know

    just remember that often people get swept away by power ratings (even accurate ones), when in real world , the difference may make 3/4 of a donkeys ball difference (eg. between 400 and 450wrms)
     
  7. OP
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    jinxhavoc

    jinxhavoc Member

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    Hey guys,
    Those specs again as i will refer back to them:
    - Power/channel @ 4 ohm: 150 W RMS x 2
    - Power/channel @ 2 ohm: 230 W RMS x 2
    - Power output (Bridged 4ohm): 450 W RMS x 1

    From the look of those specs is obviously has 2 channels, which leads me to my next question:
    Could i run a 800W-1200W (Max) 12"Sub off one channel leaving one to run my 6x9's off?

    And with that, my head unit, Kenwood (dunno model) that has 4x50W output could power some 6" speakers pretty good?

    Thanks, Matt
     
  8. pavlos

    pavlos Member

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    I'd recommend not running 6x9s if your going to run a sub as well, they both produce bass and they bass that comes out of both sounds different, so overall it doesnt sound to flash...

    Instead get some 6.5" splits or just 6.5" coaxials for the rear and run them in conjunction with the sub if you want some nice sound...

    and, its really recommended to run a 'dedicated' amp just to power the sub, because not only will it have a sufficient amount of power going into it, but also you can set the low pass filter on the amp properly to cut out the high frequencies from going to the sub...

    so ideally, you would have 6" splits for the front, 6/6.5" coaxials for the rear and sub in the boot (10, 12, 15", your choice), the sub powered by either a monoblock or 2 channel amplifier bridged and a 4 channel amplifier to power the front and rear speakers... (or you can just get a 2 channel amplifier for the front speakers and run the rear speakers directly from the deck...)
     
  9. OP
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    jinxhavoc

    jinxhavoc Member

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    Hey its been ages since i have posted here i know, thanks for your help so far. Can anyone explain the difference between 2ohm and 4ohm and what they stand for etc?

    And is there anyway i can get something to (neatly) fit the 6x9 hole in my back parcel shelf so i can put some 6's in?

    Because i have those expensive 6x9's that i forked out for and now i wish i had of got some 6's. I have the stock 4"s in the front dash, they get replaced later on, i think i will just get an amp, the one i mentioned earlier if its still availible, a sub and somehow put some 6's in the back, probably sell of the Lightning audio 6x9's that i have.

    Thanks a million :)
     
    Last edited: Dec 8, 2004
  10. Jackson Ho

    Jackson Ho Member

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    ohms are the impedance that the speakers are rated at. Most car speakers are at 4 ohm, home theatre is at 2. Generally (loosely worded) the higher the ohmage the better the speaker produces sounds based on the watts available, plus wear. The main reasons behind 4 ohm in car is.

    Inefficent use of 12v in cars.
    Cars will never sound as good

    Now back to the question.

    Speakers (subs mostly) generally need more power to get louder. 4x the power = double the noise. So a way of cheating is to run your amp at 2 ohms impedance where you will run the speakers harder, messier but they will be louder.

    How do you make a sub run at 2 ohm?

    Parallel and Series modifies the load on the amp.

    2 4 ohm subs in series (r = r1 + r2 .. + rn) means ohms of 4 + 4 = 8
    2 4 ohm subs in parallel (1/r = 1/r1 + 1/r2 ... + 1/rn) means ohms of 1/4 + 1/4 = 1/2 inversed = 2 ohms.

    Now modifications possibly try speaker mounts like you can get at Strathfield or Jaycar.
     
  11. OP
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    jinxhavoc

    jinxhavoc Member

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    Hmm, could you really simply the ohm's bit? And i want to get some sort of plastic mould i guess that neatly makes the 6x9 speaker hole be filled with a 6-6.5" speaker.. hmm
    Matt
     

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