optimal crossover freq.

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  • 09-24-2004, 02:50 AM
    beachcomba
    optimal crossover freq.
    Hi guys,

    Short time lurker, first time poster.


    I was just looking to get some advice on what to set the crossover to for my set up. I have a denon 1604 a/v receiver matched with Mission 701's and a Paradigm CC-170 center channel and a velodyne CT-150 sub. The denon lets me set the cross-over @80hz-100hz-120hz-150hz. I've set all speakers to small and was just curious on what I should set this to. Room is basically a shoe box 12'x15' with the sub tucked away in the corner.


    ATM I have it set to 80hz but I'm having the hardest time to balance the sub to the mains/center, with sub always sounding too prominent or too quite.

    I mostly watch movies, but I am also an avid music listener. Moreover I prefer the lower octaves to slightly over-pronounce themselves, if you understand my liking.

    I know my set-up is not exactly 'high-end' maybe even a little laughable, but it sounds nice (aside from the bass-management issue). So should I just keep moving my sub around the room(maybe closer to the mains?) or up the cross-over?


    As you can see I'm kind of a newbie to this bass management thingy, this is my first home theatre receiver. Any help or response would be greatly appreicated.

    Gracias
  • 09-24-2004, 05:14 AM
    kexodusc
    You have a perfectly acceptable setup, don't be embarassed by it at all. Gotta start somewhere, and it'll smoke any HTIB or cutesy offering by BOSE.

    I'm no pro at this by any means, but I have learned more than a few tricks over the years.
    Sounds to me like you've got room acoustic problems. This can make it very tricky to get the right blend with your main speakers. Don't get upset, I've got them, everyone's got them. Woochifer or someone could probably tell you how to deal with those, but in the meantime let's cover the basics.

    Setting your speakers to small is good. Make sure you don't set bass output to BOTH speaker and sub though if you do this (most receivers won't anyway). IMO, the lower the frequency cutoff, the better, so 80Hz is ideal in your setup. I use 60 Hz for music and sometimes 40...still haven't decided what's best, but I like the exaggerated bass of 80Hz for Home Theater. Make sure the dial on your subs crossover is cranked to highest setting possible (ie: 150 Hz or whatever). Don't worry, the receivers going to cutoff the bass. If the dial is cranked, it might cause some filtering of bass that you don't want.

    Sub placement could be your problem. Here's what I do. Place the sub in your listening position. Play some music with a good, sustained bass track. I like the Crystal Method or Norah Jones, but whatever you got. Wander around the room to the likely placement options you have for your sub and take notes of where the bass sounds best. Wherever the bass sounds best is where you place the sub.
    One thing to consider...closer placement to walls and corners will enhance the bass frequencies, maybe even making it too "boomy". This is a trail and error thing usually.

    Unless you want to open Pandora's box and start playing with the crossover on the sub itself, you are somewhat limited in what you can do. Parametric Equalizers are great for evening out the frequency response of subs, but they aren't all that cheap. You may find a home theater setup disc helpful to you. Do you have an SPL meter? If not, I suggest you find $40 or so and head to Radio Shack to get one...this is an absolute must for any home theater.

    Good luck.
  • 09-24-2004, 07:43 AM
    Woochifer
    Typically, the rule of thumb is to set the crossover frequency as low as your speakers can handle. The Mission 701s are floorstanders, right? In any case, if 80 Hz is the lowest setting, you should go with that one. The higher frequencies are more for small sub/sat setups. You don't want to go with those settings unless the speakers truly can't handle the midbass signals. Any decent bookshelf or floorstanding model not sold as a HTIB or sub/sat system will easily handle the frequencies down to 80 Hz.

    Keep in mind that the low frequencies are very tricky to get right, especially in a medium sized room like yours. The wavelengths are long enough so that they interact in different ways depending on what part of the room you're sitting in. Corner placement gives you maximum bass reinforcement, but it's also the most unpredictable alignment with how the bass sounds. Kex's guideline of putting the sub where you sit and going around the room to find the location where the bass sounds most extended and even is solid advice.

    In general, a room of your size will create at least one problematic frequency interaction. This will make the bass either sound overly boomy or anemic, depending on where your listening position is located relative to the subwoofer. If it sounds anemic, you might need to maximize the bass reinforcement with a corner placement. If it sounds boomy, then you need to identify the frequencies that are causing the bass to sound boomy. Ideally, you want to even out the bass response as much as possible. If it's uneven, it will sound boomy and will not integrate with the other speakers very well. In addition, if it's boomy, you'll set the levels based on the peaks rather than the prevailing average level for the entire bass range, which means that it will sound boomy only when certain the sound hits certain notes, and too low with all other bass sounds.

    Kex mentioned parametric equalizers, and IMO those are vital if you want to optimize your bass. The main role for a parametric EQ is to dial down those frequencies that cause the bass to sound boomy. In my room, I did some measurements using test tones and a SPL meter, and found two peaks larger than 10 db that caused my subwoofer to sound unbearably boomy. With the parametric EQ, I dialed down those peaks and now the bass sounds full and even. It also allowed me to more accurately set the level on the subwoofer.

    The most frequently recommended parametric EQ on this site is the Behringer Feedback Destroyer, which costs only $120. VERY steep learning curve, but the results are worth it.
  • 09-26-2004, 12:43 AM
    beachcomba
    thanks for the advice guys.


    Looks like I'll be getting a SPL meter some time soon.