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Crossover Question

Discussion in 'Audio' started by MudFrog, May 13, 2003.

  1. MudFrog

    MudFrog 1/2 ton status

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    My amp (Lightning Audio B300.4) has a built in crossover. It is a 4 ch amp which I am running 1 sub (bridged through rear channels) and 2 6x9's (front channels), it sounds pretty good but I think I still need to work on the crossover a little bit. The range is 40-400, where should the sub be between the two and where should the 6x9's be? There was also a juice boost, etc. that I'm not 100% sure as to what it does and the manual was not a whole lot of help. I will read it again though, just wanted to get some oppinions.
     
  2. scrappy88

    scrappy88 1/2 ton status

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    I have my sub crossover set to 50hz or 80hz, I can't remember. Then I let my 6x9's get the full range, no crossover. Probably not the best setup but it sounds good. /forums/images/graemlins/cool.gif If I set the sub crossover to 100hz or higher it starts to sound like crap though.
     
  3. MudFrog

    MudFrog 1/2 ton status

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    [ QUOTE ]
    If I set the sub crossover to 100hz or higher it starts to sound like crap though.

    [/ QUOTE ]

    Thats what was happening with mine, at some pitches it sounds good but some it sounds like crap.
     
  4. jakeslim

    jakeslim 1/2 ton status

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    I also have a 4channel driving two 6inch speaker and a sub. I found the best way to find a setting is to take a cd of the kind of music you mostly listen to with good bass, turn down the small speakers, and adjust till you like. Then slowly bring up the small speakers to blend in. One thing to remember is that different music will usually demand a different mix on the amp.
     
  5. Greg72

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

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    Scott,

    The crossover point you choose will be based not only on the speakers you are trying to "blend", but also on the crossover SLOPE that's available on that amp.

    The better ones will have slopes of either 18dB/octave or 24 db/Octave so once you reach the cutoff frequency (say 80Hz) almost NOTHING higher gets through to the sub. If the amp uses a more traditional 12db/Octave slope, there will still be a lot of bass information coming through ABOVE the crossover point you have selected....

    More often than not, this is what causes the sub to sound like "crap" or to sound like some vocals are even coming through them. If you can't get a steep slope setting on your amp (18 or 24dB/Oct) then you may have no choice but to select a lower-than-ideal setting for the subs (Like 50Hz) so that the "blending" sounds more natural. Generally, when you have a shallow slope on the crossover, both the 6x9's and the subs will play a lot of the same frequencies (near the crossover point) so it will tend to make the bass sound exaggerated or bloated in that area.

    If you decide to get really serious, you can build your own crossovers with whatever slope you want (there are plenty of places online that should have schematics), then you can really dial-in whatever sound you want....or you could buy an outboard crossover with a more comprehensive selection of slopes and crossover points.

    /forums/images/graemlins/thumb.gif
     
  6. MudFrog

    MudFrog 1/2 ton status

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    I do have an external crossover but I was trying to keep from using it.

    I'm thinking maybe part of the problem is I'm turning the Gain high on both sides and keeping the volume on the CD Player low, I'm going to try turning down the Gain and cranking the volume.

    Here are the "Design Features"

    Crossover Filter Switch: High for High Pass - Mid- Tweeter
    Off for All Pass- Full Range
    Low for Low Pass- Subs
    (I currently have my 6x9 channels set to High and subs set to Low)

    Adjustable Crossover Frequency Control: 40-400HZ
    (6x9's set to 400, and Sub set to 40)

    Juice Boost Switch: Applies 12db of 50Hz Bass Boost.
    (Turned on for all channels, going to try turning it off on the 6x9's)

    Power Rating: 50w x 4 @ 4ohms
    75w x 4 @ 2ohms
    150w x 2 @ 4ohms

    Input Sensitivity: 150mV - 4V
    High Level Input: 1.5V - 14V
    Signal to Noise Ratio: >90dBA
    Channel Speration: 50dB
    Crossover: High/Low/All Pass Switch
    Crossover Type: Variable 40~400Hz

    Greg.. no laughing at the specs /forums/images/graemlins/rotfl.gif
     
  7. Greg72

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

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    Scott,

    OK I can give you a few pointers....some info is still missing though.


    1. Gain - This is where my whole "broken record lecture" about high voltage output on head units comes back! /forums/images/graemlins/grin.gif A powerful deck will allow you to use less "Gain" or "Input Sensitivity"....to achieve the maximum undistorted output level possible. If your deck is weak (or has poor signal-to-noise ratio) increasing the "gain" is also going to increase the noise floor of the system.....and that's when you get problems like alternator whine, etc.

    Generally, you need to determine the maximum clean output of each component and set the controls NOT to exceed those values. If you have and oscilliscope, this level setting is pretty easy to do.

    Sounds like you have TWO switches for the crossover and you can use one to run as a low pass (for the subs) and the other for the high pass (The 6x9s)....what's a little confusing is that you have them set quite far apart!! There is a HUGE gaping hole musically between 40Hz and 400Hz (even with a 12dB/Octave crossover) so your settings are probably creating a weird effect. If it were me, I'd set the low pass (subs) at around 60-80Hz and the high pass (6x9s) at around 100Hz to start with....

    SINCE I DON'T KNOW THE SLOPE OF THE CROSSOVER THIS IS ONE OF THE MISSING ITEMS...

    If the slope was steeper, you could set the low pass and high pass values closer together since there would be very little "overlap" of frequencies.

    I wouldn't be concerned about letting the 6x9's play down to 100Hz....it's not really "bass", more like "upper bass" and a speaker that size will handle it fine.

    "JUICE BOOST" <- Ha ha ha (sorry you said no laughing! /forums/images/graemlins/thumb.gif) That's a silly feature....in home stereos that would be the "Loudness" button on your receiver.....all it's going to do is create an obnoxious exaggeration of bass at 50Hz. You don't need that adding to your problems. You'll never get believable sound with that switch turned on. 'Nuff Said

    Anyway, try the settings I suggested, and keep the JUICE BOOST off (on ALL the speakers)....and the sound should start to open up and start sounding better.
     
  8. MudFrog

    MudFrog 1/2 ton status

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    Will do! Thanks /forums/images/graemlins/thumb.gif
     
  9. MudFrog

    MudFrog 1/2 ton status

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    Took your advice and so far so good, on occasion the bass still sounds funky but I probably can blame that on the cheap amp or the ripped MP3s.

    Also, to get any significant bass with the "Juice boost" turned off I had to back off of all of the gains (bass gain a little bit higher then the 6x9 gain) and crank the head unit. It's a pretty good head unit though (Kenwood KRC-S505 I think?) so the sound is pretty good.
     
  10. HarryH3

    HarryH3 1 ton status Author

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    [ QUOTE ]
    or the ripped MP3s

    [/ QUOTE ]
    Try playing standard CD's and see if you still get the muddy bass. I've played with MP3's on my computer and don't like the way they sound. The music just sounds distorted to my ears. /forums/images/graemlins/frown.gif If I play the same song direct from the CD and then from an MP3 ripped from the very same CD, I can tell a very big difference in the sound quality. You may be chasing a ghost... /forums/images/graemlins/wink.gif
     
  11. MudFrog

    MudFrog 1/2 ton status

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    I thought the same thing so I popped in a regular CD and at times the bass was still distorted. I think I'm going to hook up my other sub, bought 2 used 1, and see if maybe it has to do with the sub.
     

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