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Bottom End..

JamesBlackBandJamesBlackBand Posts: 2
edited August 2007 in PA General Discussion
We have a new DriveRack Pa.. Before we were splitting up our system by using a the subouts on the board.. We are running two JBL 118s subs and two JBL Jrx125 cabintes.. After going through the DBX and then Pinking the room with the Auto EQ, the bottom end has been reduced dramticaly. It doesnt HIT hard like it used to.

We are having a hard time sweeping the mids and highs on the 125's This DBX has seemed to make us go backwards in our setup... Can anybody give me some suggestions? Do I need to be adjusting the internal crossover on the DBX as well?

I thought thats what the AUTO EQ was supposed to take care of.

Thanks
Garrett

Comments

  • DraDra Posts: 3,777
    Garrett, Welcome and don't get discouraged. Go back to the main index and read the post in the FAQ section. Then, do a search on Auto EQ. There are a lot of posts that will explain what has happened and give you some pointers. Get that far and post back.
    DRA
  • bobdbobd Posts: 7
    Garrett,

    The auto eq is very good but not, unfortunately psychic. It can work out what it can hear but not why it can hear it. For example it can't differentiate between direct and reflected sound. Here's a simple equation which you will probably find elsewhere by searching. It gives you a frequency below which the auto eq can't work but doesn't know it can't work.

    Fc=3*(1128/d) where d is the room's smallest dimension in feet. Let it do it's eq and then flatten all frequencies below Fc. EQing below this frequency has to be done either by ear, an analyser like smaart or preferably both. You can't use a reference mic which is what auto eq does.

    Bob.
  • DraDra Posts: 3,777
    Bob, Assuming that what you say is true (I have no reason to doubt), that is excellant info to have. Do you know of such a formula for the upper range?

    DRA
  • bobdbobd Posts: 7
    The short answer is that there isn't one. Low frequencies have relatively long wavelengths so the smallest room dimension is going to have a greater effect on these. High frequencies have shorter wavelengths and are less affected by the smallest dimension.

    So the effectiveness of auto eq is always going to be ok at high frequencies; it's only the low ones that can't always be eqd.

    Bob.
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