bi-amping

howie777
howie777 Posts: 357
edited February 2006 in Car Audio & Electronics
I am considering some components for my car. If I go with a 400.4 and bi-amp the fronts, is the max RMS rating for the driver that can handle the least about of power?(tweeter usually). Polks fit guide doesn't have anything listed for my vehicle (2005 altima) and crutchfield only lists DB6500 for the fronts but I would like to use SR6500s and maybe a 10 SR sub later. My other amp choice is the 300.2 but I'd like use the 400.4's built in x-over so I don't have to mount the SR's crossover.

Howie
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  • audiobliss
    audiobliss Posts: 12,518
    edited February 2006
    If the db6500 will fit, I would assume the SR6500 will, too, but I'd ask Polk about it. It may require some light modification, such as cutting out some sheetmetal or using a wooden mounting ring. As for biamping, that'd be a great match (imo) to biamp the SR6500 with a C400.4.

    As for the RMS rating for the SR6500, since the crossover divides the power between the mid and the tweeter, I would think the RMS rating is for neither the mid nor the tweeter, but rather the 'set', determined by the crossovers distribution of power.

    If you just set your gains very conservatively at the start, and tweak them with some common sense, you should be fine with biamping them.
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  • neomagus00
    neomagus00 Posts: 3,899
    edited February 2006
    in the 400.4 / SR6500 case, that amp provides plenty of power, so set the gains normally on the mid, then just tune the tweets until they sound right - you're feeding them very clean power, so it'll take a ton of it to blow the tweets
    It's not good, very fundamentally simply not good. - geolemon

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  • MacLeod
    MacLeod Posts: 14,358
    edited February 2006
    Im bi-amping my beloved SR's with 75 watts per channel and they sound better every day.

    So the 400.4 will be a fine match for the SR's but like Neo said, set the gains properly and use common sense with the volume and youll be fine.
    polkaudio sound quality competitor since 2005
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  • Toxis
    Toxis Posts: 5,116
    edited February 2006
    using the stock x-over does not divide the power. It divides the frequency range but not power.
    Never kick a fresh **** on a hot day.

    Home Setup: Sony VPL-VW85 Projo, 92" Stewart Firehawk, Pioneer Elite SC-65, PS3, RTi12 fronts, CSi5, FXi6 rears, RTi6 surround backs, RTi4 height, MFW-15 Subwoofer.

    Car Setup: OEM Radio, RF 360.2v2, Polk SR6500 quad amped off 4 Xtant 1.1 100w mono amps, Xtant 6.1 to run an eD 13av.2, all Stinger wiring and Raammat deadener.
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  • MacLeod
    MacLeod Posts: 14,358
    edited February 2006
    Right. The power will divide regardless if the x-over is there or not. Just like water. You have a hose running to 2 faucets, an equal amount will flow to each faucet.

    However, a crossover can have resisters and such thatll only allow a certain amount of power thru to a certain speaker. Like say 1/3 going to the tweeter and 2/3 going to the mids.
    polkaudio sound quality competitor since 2005
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  • audiobliss
    audiobliss Posts: 12,518
    edited February 2006
    MacLeod wrote:
    However, a crossover can have resisters and such thatll only allow a certain amount of power thru to a certain speaker. Like say 1/3 going to the tweeter and 2/3 going to the mids.
    Well, that's what I was *trying* to talk about. What's the difference, in all practicality, in that and in what I said? Being serious here...I wanna understand...
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  • neomagus00
    neomagus00 Posts: 3,899
    edited February 2006
    none, functionally...

    an xover, though, does divide the power... half (or 1/3 or 2/3 or whatever) to one speaker, half to the other... divide the frequency spectrum into 20-3500, and 3500-20000. Say the total power in each band, coming from the amp, is 100 watts (not a bad assumption - the high band has a larger frequency spread, but there's less energy per unit frequency the higher you go)... then you have 200 total watts going into the xover. but, you only have one band (plus some bleed-off) coming out of each channel of the xover, with about 100 watts each. 200 in, 2 x 100 out - the xover has split the power.

    for the more mathematically inclined, think of integrating the power per unit frequency over each frequency band, where the power is also frequency dependant (exponentially decreasing with rising frequency)... the sum of the separate integrations is the same as the integration over 20-20000 Hz... power in is 20-20, power out is the separate bands individually...
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
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  • Red230SX
    Red230SX Posts: 211
    edited February 2006
    Also lots of crossovers purposely pad down the tweeter to match the sensitivity
    of the woofer. If you just slam a tweeter and woofer together and put a
    generic crossover circuit in, the tweeter will always by nature be louder since
    tweeters are more sensitive to power than the woofer. That is why a good
    crossover will pad the tweeters output to match the woof/mid so you have
    balance in the amount of output you get. And some xo circuits also use a
    fuse in the tweeter side of the XO to protect it from too much power.
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  • neomagus00
    neomagus00 Posts: 3,899
    edited February 2006
    true... or a lightbulb instead of a fuse...

    btw, for those who care, the pseude-mathematics above is a fairly-well-educated guess, but it is still my own ideas, so if it's wrong, no attacking me :p
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
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  • PoweredByDodge
    PoweredByDodge Posts: 4,185
    edited February 2006
    Red230SX wrote:
    That is why a good
    crossover will pad the tweeters output to match the woof/mid so you have
    balance in the amount of output you get.

    actually i've found it to be the other way around - pads the woofer.

    my old dx crossovers had " -3, 0, +3" for the tweeter... which was a slider switch that changed resistors for an L-pad on the woofer... at "+3" the woofer was padded -6 db's... at 0, it was padded -3, and at -3, it was not padded. (i think thats how she went).

    my audiobahns are the same way pretty much... i've got to tri amp (or pad if i'm lazy) so as to get the mids in the dash to shut up in relation to the tweeters that are not quite getting loud enough to overcome them.
    The Artist formerly known as PoweredByDodge
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  • PoweredByDodge
    PoweredByDodge Posts: 4,185
    edited February 2006
    neomagus00 wrote:
    none, functionally...

    for the more mathematically inclined, think of integrating the power per unit frequency over each frequency band, where the power is also frequency dependant (exponentially decreasing with rising frequency)... the sum of the separate integrations is the same as the integration over 20-20000 Hz... power in is 20-20, power out is the separate bands individually...

    i hate you... i despise all things math, and you just gave me a headache.

    but i've got a question for you - as much as i did understand what you were saying, some of it is beyond me... so here goes.

    if you have a 100 hertz wave and a 10k hz wave... superimposed on each other...

    woofer x'ed at 500 hz low pass... tweeter x'ed at 500 hz high pass (not practical, jsut for the sake of this question).

    now that superimposed wave is pumped at a magnitude of 100 w into 4 ohms -- say we have 4 ohm speakers...

    so...

    does the woofer get 100 hz @ 100 w .. and the tweet 10k @ 100 w? or are you saying it is divided differently?
    The Artist formerly known as PoweredByDodge
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  • Red230SX
    Red230SX Posts: 211
    edited February 2006
    I am not sure why it would vary that's why we have what is reffered to as
    "Full Bandwidth" but I also understand the angle Neo is comming from where
    you are filtering out everything except within a certain band. Yeah just what
    I need.. A Headache!

    And PBD,

    Sometimes they do indeed pad the woofers, I guess in most cases it would
    be the woofer that gets padded if the tweeter being used is a typical dome
    unit. I would think if the setup was a midwoofer and a compression horn then
    the horn it's self would be on an Lpad because compression drivers can get
    WAY louder than a point source driver. :)
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  • neomagus00
    neomagus00 Posts: 3,899
    edited February 2006
    the woofer would probably get like 65, the tweet like 35, if the frequencies were mixed at equal loudness (if it was just an amplitude-1 wave for both, then it'd be 50 W to both, but it'd sound way treble-heavy)...

    consider a 100 Hz wave of amplitude 1, and a 10 kHz wave of amplitude 1... the total power from 20-20k Hz is 100 W, that's known... consider two separate bands now, 20-500 and 500-20k... the sum of the total power in those two bands must equal 100 W, but each band only has half of the original information, so each band has about 50 W.
    It's not good, very fundamentally simply not good. - geolemon

    "Its not good enough until we have real-time fearmongering. I want my fear mongered as it happens." - Shizelbs
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  • Red230SX
    Red230SX Posts: 211
    edited February 2006
    Ok Spanky!

    I will take your word for it! :D
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  • MacLeod
    MacLeod Posts: 14,358
    edited February 2006
    Ya see, thats why I buy the expensive speakers. This way, the Polk engineers get all the headaches over trying to figure all this crap out. All I have to do is install them and listen!
    polkaudio sound quality competitor since 2005
    MECA SQ Rookie of the Year 06 ~ MECA State Champ 06,07,08,11 ~ MECA World Finals 2nd place 06,07,08,09
    08 Car Audio Nationals 1st ~ 07 N Georgia Nationals 1st ~ 06 Carl Casper Nationals 1st ~ USACi 05 Southeast AutumnFest 1st

    polkaudio SR6500 --- polkaudio MM1040 x2 -- Pioneer P99 -- Rockford Fosgate P1000X5D
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  • howie777
    howie777 Posts: 357
    edited February 2006
    Thanks all, just FYI Best buy has V12s clearenced by me. I think it was 269 for the 75x4 and 250 for 600 watt mono (original 399 each I think).

    Not sure I should go for it or not but I would love those amps + sr components and sub :-)

    Howie
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