Sub Crossover

Discussion in 'Speakers' started by Christopher B, Sep 1, 2004.

  1. Christopher B

    Christopher B Stunt Coordinator

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    Hello,
    I have looked at all of the archived messages I could find about this, and checked other sites, and I am even more confused than before.
    I have JBL E90's as mains and a E250P sub and a Yammy RX-V 1400 receiver. I have it set up with the mains as small, and the crossover in the receiver at the recommended 80hz. Some sites suggest leaving them set to small but lowering the crossover to get more full range out of the mains. Other sites, and even the Yamaha receiver manual says to set them at Large because they are large, and set the crossover at 80hz. I am going to experiment with the settings which I know is the best way to determine what I like, but how do you "experts" have your systems set up?

    Thanks
     
  2. Tom D

    Tom D Stunt Coordinator

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    Hi, Christopher

    I have all my speakers set to small. 80hz crossover with the sub crossover at its max setting 140hz (?). If you set the mains to large may yield a fuller sound, however, the amp will work harder, which may cause distortion. If you set all the speakers to small all frequencies below 80hz will be redirected to the sub. In essence the amplifier built into the sub will be doing all the hard work of reproducing the bass and your rcvr will just have to deal with your 5 speakers.

    Regards, Tom
     
  3. Lee Carbray

    Lee Carbray Second Unit

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    Christopher, you are right the best way is to experiment and determine what sounds best to you. You can also download and burn some test tones to CD and plot the responce form about 100hz down. This will give you a good idea of how the sub and speakers are interacting throughout the crossover range. You will also be able to visually see what affect changing the crossover and adjust ing phase and such have, not to mention sub placement.
     
  4. Wayne A. Pflughaupt

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    Christopher,

    Experimenting never hurts, but in the end you’ll probably find that it’s best to set the mains to small. This way you only have one speaker, the sub, reproducing the bass.

    There are at least a couple problems inherent in running the mains full range.

    For one, bass frequencies interacts with the room in various ways to give peaks and valleys in response, cancellation, nulls, etc. There will be cancellation at the half-way point between a bass driver and a boundary as the soundwave bounces off the boundary and, now out of phase, meets the original signal. The cancellation is frequency-specific related to the distance between the driver and the boundary; there are mathematical formulas to predict and calculate this stuff. And since bass is omnidirectional you will get as many distance-related cancellation frequencies as you have boundaries – four walls and ceiling minimal.

    Add additional bass drivers and they will introduce their unique and specific boundary cancellation problems as well. Furthermore, bass drivers will interact with each other; the half-way point between two drivers behaves like a boundary.

    It should be easy to see, Christopher, the more speakers you have reproducing low frequencies the more ragged you can expect bass response to be.

    Second, for the sake of argument let’s put all that aside and assume you did have smooth bass response with all those full-range speakers going at once. I don’t know how deep your full-range speakers actually go, but let’s say 45Hz. And let’s say for the sake of argument that your sub is also flat from 20Hz-100Hz.

    Combine all that and what do you have? You have six speakers putting out bass down to 45Hz. Then five of them drop out and you only have one “carrying the mail” from 45-20Hz. So your response is going to be very intense above 45Hz, and then very weak from 45Hz-20Hz.

    Bottom line: Overall, your system is going to sound like it’s totally dead below 45Hz, and measurements will confirm it.

    So, what do you get when you set the main speakers to small? You get flatter response across the whole bass range because the sub is doing the job without the mains adding and exaggerating upper bass. And you get smoother response because you only have one driver interacting with the room, not six.

    Regards,
    Wayne A. Pflughaupt
     
  5. Christopher B

    Christopher B Stunt Coordinator

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    Thanks to everyone who has responded.

    It makes sense to have the subwoofer producing the lower frequencies and like Tom said, let the amp in the subwoofer do most of the work.

    Wayne,
    Thanks for the detailed explanation, I did play with my set up a bit and basically ran into the very things you are talking about.

    I am changing the crossover a bit to see what sounds the best. I tried lowering it to 60hz and it seems to fill out the sound a bit without taxing my mains. I guess it just seemed a waste to have some decent full range speakers and then have most of the lower frequencies coming out of the sub. But to produce a nice clean 5.1 sound, this is definately the best set up. I only listen to music with 2 channel stereo, so I do get to listen to the mains by themselves.

    Thanks again
     
  6. Wayne A. Pflughaupt

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    Please allow me to disabuse you of that “waste” thing:
    • Do you use all the inputs or features on your receiver?
    • Assuming you still have one, did you ever use all the endless features your VCR had/has?
    • Do you watch each and every channel your cable or satellite service provides?
    Feel better? [​IMG]

    Regards,
    Wayne A. Pflughaupt
     
  7. paul clipsel

    paul clipsel Stunt Coordinator

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    Have to agree with Wayne.I have tried every combo possible with my pre-pro's bass management settings.But in the end setting all of my speakers to small and redirecting all the bass to a good well positioned subwoofer always seems to give me the best sound.My speakers can play lower frequencies than what I am sending them, but the room modes cancellations mess up the balance.Moving the speakers helps but then my imaging and sound pans gets mucked around.

    PC
     
  8. Brian L

    Brian L Cinematographer

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    I am also "wasting" a chunk of my B&W 604's low end by crossing over at 80 Hz, but again, I think its the best way to go in my room.

    My local NHT/NAD dealer has a saying: "Don't buy bass twice". Which means, if you are going to do a proper sub, no point in buying big ass floor standers!

    Actually, in my case, I bought the 604s when my daughter was born because a pair of tipsy stand mounts (what I had at the time) was way too risky. And now that I have 'em, well what the heck, might as well use 'em as very expensive speaker stands for the mid/tweeter[​IMG]

    When I do sell 'em, I can say with honesty that the woofers are hardly used.

    BGL
     
  9. Christopher B

    Christopher B Stunt Coordinator

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    Well I have been experimenting with my set up as much as possible since I posted yesterday, and I keep coming back to the speakers set up as small and the crossover set at 80hz. I guess there is a reason why this is the recommended set up!

    Brian,
    The tower speakers also work well with our big Malamute, who has almost tipped the tower speakers over once or twice. They are also really cool looking mid/tweeter speaker stands.

    Thanks
     

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