Equalizers, Why or Why not?

Discussion in 'Archived Threads 2001-2004' started by Steve Morgan, Oct 25, 2001.

  1. Steve Morgan

    Steve Morgan Second Unit

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    Okay here's the deal.I have 2 subs a SVS20-39cs and a Paradigm Servo 15a.My speakers L/R/C are capable of bass to the mid 30hz,the surrounds are capable of bass to 40hz. My Pre/pro is the B&K REf 30 with good bass management.With the help of a HT member I tracked my SPL levels from 70hz which is my crossover point down to 20hz.A spread sheet was made and my problem was in the 50hz to62hz range with the notch fliter in the Ref 30 I applied a -8db nothch to the 51.3 to 66.7 range. My other problem was at 22hz where I was 15db below average.The most I could do was add a 6db boost to the 20hz range.Chris's spread sheet showed after I applied the notch and the 6db. boost my average was 76.76db.My question is do I need a equalizer such as the Bijou or the Rane 44 or something more simple? My room is 27'x14' with 8ft. ceilings a open dining room that is 13'x13' on one end and a hallway on the other.Due to SO and room contraints my speakers are not in the ideal spot. Any advice and feedback is appreciated
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  2. Wayne A. Pflughaupt

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    Steve,
    I outlined most of this in an e-mail I sent you a couple of weeks ago, but I never heard back from you. Did you get it?
    Once again, Steve, your information is too vague to be really helpful. There are some questions we need answered in order to help you:
    First, are you running your mains and surrounds full-range? If so, this is a bad idea. Five full-range speakers plus two subs makes for disastrous low frequency response in almost every case. The half-way point between any two full-range speakers will behave like a boundary and cause cancellation at a specific distance-related frequency. For instance, two subs or speakers with low extension placed 12-feet apart will exhibit a null at about 56 Hz. Even at 20 feet a pair of full-range speakers or subs will display a dip in the 33-Hz range. A third that is not exactly the same distance apart as the first two will display a null between the other two speakers. Thus with three you will have cancellation at three specific frequencies. The problem compounds the more low frequency speakers you add: Four of them positioned at unequal distances will deliver cancellation at six frequencies. Five will see cancellation at 10 separate frequencies. Six will display cancellation at an astounding 14 frequencies.
    So things will improve greatly if you let just the subs do the low freq work, Steve. And that will eliminate the need for an expensive seven-channel equalizer. All you will need then is a dedicated parametric EQ for each sub, which should set you back at most $350 for the pair, if you get a budget Behringer product or a couple of used Rane PE-15 or -17s on e-bay. With the parametric you can set the bandwidth you actually need instead of using the fixed notch filter in your processor, which probably does not have the optimal bandwidth.
    Next question:
    Do you have your subs in two different locations? Again, bad news if you do. Where exactly are they located? Your room, including the dining room is 4376 cubic feet. It is hard to believe that your response with these subs is so far down at 22Hz. By comparison, my listening area is 6200cubic feet. I only have a pair of 12” Shivas in 2.5 cubic ft. boxes, which is really too small for optimal extension. Yet with EQ I have good response to 20Hz, and I easily hit over 100dB with those depth charges scenes in U-571. Your room is 30% smaller than mine, and your subs are better. You should be able to make pictures fall off the wall!
    I’ll cut to the chase, Steve: For optimal sub response, you need to set all your mains to small. You need matching subs, and they both need to be located in the same corner. This will give the maximum gain and extension. You can expect at least one, maybe two humps in response, but a parametric EQ can eliminate these. Forget all those stories you’ve heard about moving a sub around to get the best response. That’s for people who don’t have EQs. Ultimately they end up sacrificing extension and maximum output for response characteristics they can live with. The equalizers will take care of that, and then you will have it all: The highest SPL, the lowest extension and the smoothest response.
    The reason I recommend matching subs is because it makes EQing much easier. It will take 3-4 times as much trouble to properly EQ two non-matching subs in the same corner. Matching subs in two different locations is 10 times the trouble to properly EQ. Trust me, I’ve done it! And I don’t even want to think about trying to EQ two different subs in two different locations.
    However, if you at least place both non-matching subs in the same corner (preferable the one with the most uninterrupted wall length in both directions) and get a parametric EQ for each of them you be able to get satisfactory--probably even excellent--results with a little help from your HT forum friends.
    I’m going out of town for the weekend, so I won’t be able to follow this through. If this doesn’t help, hopefully someone else will be able to.
    Regards,
    Wayne A. Pflughaupt
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  3. Brian L

    Brian L Cinematographer

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    I think Wayne has provided you with a boat load of useful info. I will add a couple notes in response to your questions.
    1. Although the Bijoux is a pretty good EQ (actually, as far as EQ's go, its very good) with 1/6 octave adjustments for the bass (most non digital, non parametric units are 1/3 octave) it is still too coarse to replace a proper parametric at kiing peaks. (I own a Bijoux, and as luck would have it, spent part of this afternoon playing hooky and tweaking it!)
    2. EQ's are good at cutting peaks, but not filling nulls. If you are in a null, adding more energy at that frequency will normally do nothing but drive your amp harder.
    Best of Luck,
    Brian Leduc
     
  4. Mickey Brown

    Mickey Brown Stunt Coordinator

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    Audio Control makes some great gear...
    Just thought I'd throw that in.
     
  5. Steve Morgan

    Steve Morgan Second Unit

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    My subs are in 2 different locations.One is about 2/3 along the back wall and the SVS is in the corner.I have set all speakers as small and crossover at 70hz.The Paradigm servo 15 has its own amp, the SVS is being driven by 1 channel of a Parasound 2205at (300 watts @4ohms).So what I hear is that I will need 2 equalizers. One for each sub? I guess I can try to put them both in one corner and go from there. Where can I pick up 2 parametric equalizers for $350? Thanks Guys for all the info.
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  6. Steve Morgan

    Steve Morgan Second Unit

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    By the way where should the volume contol be set on the Servo 15? Currently it is at the 11:00 position. Should I open it up all the way? Steve
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  7. Wayne A. Pflughaupt

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    Thought I’d check in one more time before I hit the road…
    Steve, sorry about what I said about your information being vague. What I should have said is that it wasn’t the information I was looking for. Again, sorry for that.
    Yes, you will need two EQs for your subs. If you had two matching subs, and if they were both in the same corner, you could get away with only one EQ. But since your subs are different you will need an EQ for each one for optimal results, even if they are both in the corner.
    Before you ask where to get an EQ, you need to make a descision as to what model you want. If you post a new thread asking for recommendations you will get plenty of responses.
    It might be difficult to get a pair on new parametrics for under $350. If you don’t mind used equipment, you can get great prices on e-bay. I checked on the Rane models, and you can get the PE-15 (five band single-channel) typically for under $125 (saw one recently go for $87). You might also look at Symmetrix for another quality brand that can be had used at low prices. I picked up a nice single-channel Ashly parametric on e-bay last year for $165.
    As for as the volume setting on the sub, it will ultimately figure into the total equation when you set the equalizers up. For the time being, just set it where it sounds best.
    Regards,
    Wayne A. Pflughaupt
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    [Edited last by Wayne A. Pflughaupt on October 25, 2001 at 10:54 PM]
     

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