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  • noobie needs advice on buying a car amp

    ok, if you tell me go assemble a computer from scratch, it will take me less than an hour or so.

    if you ask me if i changed my radiator in my car, yes, i did it in a couple of hours or so.

    if you ask me if i am an ebay powerseller, then yes, i am.

    ok,let me cut the crap. now, i am totally unaware of car amplifiers. my vigor has an alpine cd player and alpine speakers and i will be removing the cd player completely from mine to install in my bro's car/ now, i need something to power up the speakers.

    so, i go to ebay and am confused to find different types, some say the ohm's has to match or else ^$%RT%&. then some say, it depends matching with the speakers too to get the perfect sound reproduction like http://www.realcaraudio.com/forums/a...opic/9187.html

    can someone tell me what to look for to get excellent sound reproduction i got with the alpine HU
    400W Power Amplifier -$25
    P3 laptop mobo-$30ish
    128MB RAM-$10
    6GB+80GB 2.5" HDDs-$130
    GPS-$60
    7" TS Lilliput-$280
    10" pioneer 500w sub-$55
    sony xm-3020 30W amp-$10
    jensen 340W A34XP amp-$40
    mp3car.com resources and members- priceless

  • #2
    Almost all amps will sound better than head unit powered speakers... Head units put out 25Wx4 or less RMS... almost all amplifiers put out more power...

    Almost all non-woofer car speakers are 4 ohms... when you get into subs, there are wacky type wiring configurations, crazy ohm loads and such like the guy in that line was doing... Assuming that you have 4 speakers and no subwoofer, you probably just need a standard 4 channel amp amplifier... not sure what speakers you have, but check the specs for the max power/rms power and get an amp in the same power range... if those speakers sounded good on head unit power, you can probably get like a 35Wx4 RMS amp and have it sound better/get louder w/less distortion

    Here's the ebay listings for multichannel amps...
    http://electronics.listings.ebay.com...stQQsofocusZpf

    Alpine 4-channel Amps
    http://iweb.alpine-usa.com/pls/admn/...=120&p_main=10


    Best way to figure out how certain amps sound is to go to a car audio store with your model of speakers or specs similar to your speakers and try the different amps with it (Cartoys usually doesn't mind if you try out their demo room stuff)... then buy the amp you like online

    Personally, I'd recommend you with some of the more "Name" brands and buy from an authorized dealer (for the warrenty)...

    Cardomain always has crazy deals going on:
    http://www.cardomain.com/shoptype/Multi-Channel+Amps

    I got my Phoenix Gold Ti500.4 from them for less (~$270) than I could have gotten it for on eBay (~$350), plus it has the full manufacturers warrenty since Cardomain is an authorized dealer.

    Comment


    • #3
      great.

      thank you very much
      400W Power Amplifier -$25
      P3 laptop mobo-$30ish
      128MB RAM-$10
      6GB+80GB 2.5" HDDs-$130
      GPS-$60
      7" TS Lilliput-$280
      10" pioneer 500w sub-$55
      sony xm-3020 30W amp-$10
      jensen 340W A34XP amp-$40
      mp3car.com resources and members- priceless

      Comment


      • #4
        wait joo removing the head unit form yours to give oyur brother.. u ARE buying another deck or building pc right?

        just to clarify

        Comment


        • #5
          pc

          :-)
          400W Power Amplifier -$25
          P3 laptop mobo-$30ish
          128MB RAM-$10
          6GB+80GB 2.5" HDDs-$130
          GPS-$60
          7" TS Lilliput-$280
          10" pioneer 500w sub-$55
          sony xm-3020 30W amp-$10
          jensen 340W A34XP amp-$40
          mp3car.com resources and members- priceless

          Comment


          • #6
            I bought a 4 channel amp which gives 4 x 75W rms for 100, I'm still running my standard speakers at the moment so am not running at that power.
            Not sure about the make but will find out and post if you like.
            Its down!!!! Sold the Golf so took it out, it's still alive but not installed.

            Progress [-----------] 0%
            Who the Daddy Iz!

            Comment


            • #7
              Originally posted by paradoxblue
              wait joo removing the head unit form yours to give oyur brother.. u ARE buying another deck or building pc right?

              just to clarify
              just to clarify
              Attached Files
              PC Components:
              Lilliput; XPC/FLEX mobo; 1.7 ghz P4 Mobile;512 DDR; 160 gb HDD; opus 150; slot usb dvd-rw
              My work log

              Comment


              • #8
                Quick question: How will it be if I purchase a less wattage amplifier say 40W X 2 to drive speakers which are 80 W X 2?

                Will the amp fry?
                400W Power Amplifier -$25
                P3 laptop mobo-$30ish
                128MB RAM-$10
                6GB+80GB 2.5" HDDs-$130
                GPS-$60
                7" TS Lilliput-$280
                10" pioneer 500w sub-$55
                sony xm-3020 30W amp-$10
                jensen 340W A34XP amp-$40
                mp3car.com resources and members- priceless

                Comment


                • #9
                  speakers that are 80W x 2? do you mean two speakers that are rated at 80W?

                  You need to be concerned with two factors, RMS power and peak power. In short, your amp's RMS and peak power numbers need to be less than or equal to the rating of your speaker. It's ok for your amp to put out less power than your speaker is rated for ... but putting out more can damage the speakers.

                  some people will say underpowering a speaker is a bad thing ... that statement in itself isn't really true. What damages speakers is clipping (i.e. saturating the transistors on the amp's inputs or or outputs will cause clipping).

                  Anyway, if your speakers are rated for 80W RMS at 4 Ohm, and your amp will do 40W RMS at 4 ohm, that'll work just fine.

                  Since you seem to like alpine, you might want to look at the alpine v12 series amps. They've very clean and plenty powerful. I use them in my jeep with my PC. I have a 4 channel for the components and a 2 channel for my sub ... got them new off ebay for about half what circuit city/tweeter sells them for.
                  My JeepPC Install

                  "there are no stupid questions, just stupid people."

                  "it's been agreed the whole world stinks so no one's taking showers anymore"

                  Comment


                  • #10
                    If you run the speakers at closer to the recommended RMS wattage, they will have full excursion (Woofer cone will be out as far as it can go)... and should sound better especially in the lower end frequencies... Underpowering speakers is kindof like pouring a bottle of beer into a 36oz glass... The beer is drinkable and tastes good, but you really are not using the glass to it's full potential.

                    My amp is rated at 125Wxchannel RMS, speakers are 75Wxchannel RMS... Why? Found a good deal on the amp after I had already ordered the speakers...

                    There is a lot of talk about "overhead" too with amps, with more power than you need/use, you supposedly will keep at the lower end of the THD curve (Most amps operating at max power have a slightly higher total harmonic distortion than they would if running at 50% power)

                    It's really about what you want to spend / what you have planned for future upgrades... if you get a higher output amp, you could use it in a higher watt speaker setup in a new car or upgrade the speakers in your current one without having the replace the amp... Especially since Amp technology does not advance very quickly, as the last "great" advance in Class A/B amps, in my opinion, was MOSFET Amplification circuits about 10 years ago... The current "next big thing", in my opinion, are digital input interfaces on amps.

                    Comment


                    • #11
                      he speaks the truth ...

                      i did forget to point out that if the amp is rated for more than the speaker can handle, it's ok as long as you don't turn the gains up too high and give the speakers more than they can take.

                      there's some calculations you can run to figure out the proper output voltages when adjusting your gain. i have mine set to reach the speakers full potential at about 60% volume. works great since I rarely have mediacar pushed higher than 40%
                      My JeepPC Install

                      "there are no stupid questions, just stupid people."

                      "it's been agreed the whole world stinks so no one's taking showers anymore"

                      Comment


                      • #12
                        Originally posted by guavo
                        If you run the speakers at closer to the recommended RMS wattage, they will have full excursion (Woofer cone will be out as far as it can go)...
                        Since when? The excursion depends on the power partially, but its MORE effected by the install... its very, very easy to make a speaker or sub reach full excursion with much less than full power, and its also very easy to make a speaker or sub unable to reach full excursion without many times its rated power flowing into it...

                        For example, an Adire Brahma (rated at 1600wRMS) can reach full excursion with as little as 400w, and as much as 7000w, depending on the enclosure... of course, once it gets past its thermal rating then any more is pretty dangerous...

                        You give me a 100w speaker, and a 20w amp, and i'll show you how easy it is for a bad install to make that 20w slap the 100w speakers balls on its backplate

                        Comment


                        • #13
                          Originally posted by Blackrazor
                          Since when? The excursion depends on the power partially, but its MORE effected by the install... its very, very easy to make a speaker or sub reach full excursion with much less than full power, and its also very easy to make a speaker or sub unable to reach full excursion without many times its rated power flowing into it...

                          For example, an Adire Brahma (rated at 1600wRMS) can reach full excursion with as little as 400w, and as much as 7000w, depending on the enclosure... of course, once it gets past its thermal rating then any more is pretty dangerous...

                          You give me a 100w speaker, and a 20w amp, and i'll show you how easy it is for a bad install to make that 20w slap the 100w speakers balls on its backplate
                          Yes, the install is always a big part... But since these are probably just free-air door mounted coaxials, the enclosure air volume is less important to speaker operation... Subs are a much different beast IMO, it is more important to set a HPF on door speakers, so that they aren't trying to play 40hz bass tones at full volume...

                          Or are you talking about poor quality interconnects, ground loops, running RCAs next to power wire, 24GA speaker wire instead of enclosure size in regards to installation? (Because obviously all of those will cause issues with SQ/distortion) Was just speaking in general terms of "Closer to RMS generally equals better and more full sound reproduction" as well as "Running amp at 50% max RMS power gives lower THD than running at 100% max RMS power" assuming that all of the other variables in the installation equation are consistant with a proper installation.


                          Back to excursion.. .Technically, doesn't complete excursion occur at maximum rated power though since at that point it is at Xmax and as such the peak for linear travel of a driver? Since that is more of a the physical limitation on the mechanical device, whereas RMS power deals more with the maximum average power that can be dissipated due to the resistance of the voice coil and the related cooling generated by the cone movement... With subs, in a sealed enclosure, there are limitations on the amount of air available for excursion, so full excursion is related to the power and air volume values... But with free air speakers, isn't there an inifinite baffle and thus no relationship between air volume and excursion?

                          Comment


                          • #14
                            If you want something no nonsense and something space saving, wire saving time saving etc saving... go for a 5 channel amp.

                            I got a 600.5 Rockford Fosgate (they dont make em anymore ) and its 75x4 and 100x1 which bridged into 2 8ohm subs 100Wx2. It works awesome and is one amp not 4 or 3 like ive had in the past...

                            Had 2 Punch 45.2 running 1 10" sub a piece and a punch 125.2 running 6x9s in the back. 2 half caps and a ****load of wiring and fuse blocks. Then a 4 channel amp replaced the 125.2 and then a 250.2 replaced the 45.2s and now I got the 600.5 and have no caps (though ill get a yellow top when the carputer goes in) and its just attached to the top of my dual 10's box, sucha space saver.

                            my 3cents
                            (All done)
                            iPad Mini 128GB, RF 600.5 amp, JL12W0V2, 8 Infinity Components

                            Comment


                            • #15
                              ok., I am back after one week of exams :-(

                              anyways, does it really matter if I mix up the + and - terminals on the speaker? does the sound quality matter or is there anything else to it?

                              I never really cared before about the polarity of the speakers, but would like to do a decent setup.

                              thanks
                              400W Power Amplifier -$25
                              P3 laptop mobo-$30ish
                              128MB RAM-$10
                              6GB+80GB 2.5" HDDs-$130
                              GPS-$60
                              7" TS Lilliput-$280
                              10" pioneer 500w sub-$55
                              sony xm-3020 30W amp-$10
                              jensen 340W A34XP amp-$40
                              mp3car.com resources and members- priceless

                              Comment

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