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  • Dual Pro Sub Placement?

    I am running two similar "pro" type subs, exclusively for pc/laptop driven music and concert videos, not "live instruments", used here at home, typically outdoors on a screened lanai (wall behind, no side hard walls).

    Subs:
    (1) Dayton 15" pro sub PA380-8 in a ~2.9 cu. ft., ported/tuned to ~41 Hz
    (1) Peavey 15" Low Rider in a ~3.0 cu. ft., ported/tuned to ~38 Hz (being built now)
    Both are powered in mono from a QSC GX5, being fed from a Behringer CX2310 crossover, around 100-120 Hz low pass (assume 4th order LR), and a 25 Hz high pass (assume 2nd order BW).
    I just discovered the latest JRiver Mediacenter has some great built-in DSP functions. I am using the adjustable hpf, 4th order @ 33 Hz to supplement the hardware hpf. It gives me a little more peace of mind, and no other hardware is needed for driver protection.

    Questions:
    1. Is it OK to have the somewhat dissimilar (brand) subs operating together? The Peavey is a little less efficient, but they model very similarly in WinISD, and the cabs are almost identical.
    2. I am running two mains about 15 feet apart. What is the preferred placement for two subs of this type? Stacked, adjacent, or spread apart "X" feet? Close to the wall as possible?


    Thank you!
    Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
    Howard H

  • #2
    Re: Dual Pro Sub Placement?

    Originally posted by zhillsguy View Post

    Questions:
    1. Is it OK to have the somewhat dissimilar (brand) subs operating together? The Peavey is a little less efficient, but they model very similarly in WinISD, and the cabs are almost identical.
    2. I am running two mains about 15 feet apart. What is the preferred placement for two subs of this type? Stacked, adjacent, or spread apart "X" feet? Close to the wall as possible?
    #1 No; using speakers with dissimilar performance characteristics makes integration difficult and introduces issues.
    #2 Split subs ( fed a mono signal ) will introduce constructive and destructive interference and what is euphemistically called a power alley ( strong lobe between subs ) Placment requires consideration of surrounding surfaces and room acoustics if any. Sometimes cabs are placed to take advantage of the surrounding boundaries ( boundary loading ) or moved to spots to avoid exciting room resonance. The distance from cabs to reflective boundaries determines possible reflections and cancellations. A general guideline is to either have subs as close to boundaries as possible or at least 10' away
    http://www.padrick.net/LiveSound/CancellationMode.htm
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

    Comment


    • #3
      Re: Dual Pro Sub Placement?

      Originally posted by zhillsguy View Post
      Questions:
      Is it OK to have the somewhat dissimilar (brand) subs operating together? The Peavey is a little less efficient, but they model very similarly in WinISD, and the cabs are almost identical.
      It is not ideal in any sense, but I would doubt that for your intended use it will create too many problems.

      Originally posted by zhillsguy View Post
      I am running two mains about 15 feet apart. What is the preferred placement for two subs of this type? Stacked, adjacent, or spread apart "X" feet? Close to the wall as possible?
      Because you are outside, and only have one wall, it should make placement fairly easy. I would put them near the wall, with both on the ground, together. The exact placement from the wall can vary, but I would bet simply putting them right up against it would be best. Because you are outside, the bass will tend to dissipate very quickly with distance, so be reasonable with your expectations.

      Interesting placement option: Point them toward the wall, and find the distance away from the wall that sounds best. But ALWAYS keep them together and place them the same.

      Comment


      • #4
        Re: Dual Pro Sub Placement?

        Originally posted by AMC View Post
        But ALWAYS keep them together and place them the same.
        Don't want to start a debate, but the I feel the use of always is too absolute.
        Large areas often require that subs be split to get expand coverage to get the same dispersion aspects of the split tops.
        The last split sub setup I heard had flown arrays and subs were ground clustered below each array. There was over 60' separation which represents a large wavelength reducing cancellation issues. Separating the subs from the tops increases the ability to perceive isolation and requires time adjustment to correct which is a compromise in itself (NFL). As the spatial offset increases the integration becomes more difficult. ( See Bob McCarthy's books )
        Perhaps just a philosophical difference, but in numerous situations the operator is not able to set up a system as they might wish, and has to compromise to fit the particular situation. I believe it is important to understand the relationship and adapt accordingly. There are live sound techniques for minimize interaction ( and controlling ) with split and multiple subs.
        "Not a Speaker Designer - Not even on the Internet"
        “Pride is your greatest enemy, humility is your greatest friend.”
        "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

        Comment


        • #5
          Re: Dual Pro Sub Placement?

          Originally posted by Sydney View Post
          Don't want to start a debate, but the I feel the use of always is too absolute.
          You're correct, it is too absolute. Another aspect that comes in to play is the crossover frequency. The high you cross it over, the more important alignment becomes. That is one reason I like subs crossed over as low as possible (<<100Hz), for the average lay person, it makes all that much easier. Some of the line array units I have looked at, require x-overs as high as 150+, and that can require a bunch more work to get it to sound right.

          (But in his situation, I think always might be OK)

          Comment


          • #6
            Re: Dual Pro Sub Placement?

            Good to see agreement rather than controversy .
            Honestly I've seen guys ( who have been doing Pro Sound for years ) do things that when asked why - provide a reply like "that's they way they always did it" OR "that's the way ( famous person ) does it OR tried it once and it worked so"...
            None of these reasons are logical and situations change, so live sound can be like a guerrilla operation ( adapt and survive ). I know I've been given bad situations and had to "deal with it".
            One of the words frequently used in McCarthy's books is compromise.
            You'll have that :rolleyes:
            "Not a Speaker Designer - Not even on the Internet"
            “Pride is your greatest enemy, humility is your greatest friend.”
            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

            Comment


            • #7
              Re: Dual Pro Sub Placement?

              Thanks guys...now to the problem at hand. I tested the PLR 15 out of the box, and the t/s parameters are way off from published, my first Peavey product and I am disappointed. Specs are much more like a car sub than pro. I sent an email to Peavey but don't have high hopes......

              At least with Dayton or Eminence I know what I am getting.
              Attached Files
              Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
              Howard H

              Comment


              • #8
                Re: Dual Pro Sub Placement?

                Originally posted by zhillsguy View Post
                Thanks guys...now to the problem at hand. I tested the PLR 15 out of the box, and the t/s parameters are way off from published.
                Did you break it in? The test lead resistance is also suspiciously high.
                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

                Comment


                • #9
                  Re: Dual Pro Sub Placement?

                  Originally posted by billfitzmaurice View Post
                  Did you break it in? The test lead resistance is also suspiciously high.
                  Bill,

                  I just ran more calibration and tests with similar results. I have not broken it in, it has not seen power, hence "out of the box". I don't see how the Q and Fs could get near published after break-in. Isn't about 10% permanent change all that can be hoped for? I haven't modeled it with the true specs either, and don't have VAS yet until the box is built.

                  Just very disappointing that Peavey doesn't have tighter QC.
                  Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
                  Howard H

                  Comment


                  • #10
                    Re: Dual Pro Sub Placement?

                    Originally posted by zhillsguy View Post
                    Isn't about 10% permanent change all that can be hoped for?
                    Usually, but it can be more. In any event break it in to find out how it will spec in use. Out of the box readings aren't useful.
                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

                    Comment


                    • #11
                      Re: Dual Pro Sub Placement?

                      Originally posted by billfitzmaurice View Post
                      Usually, but it can be more. In any event break it in to find out how it will spec in use. Out of the box readings aren't useful.
                      As a follow up......I have been breaking this driver in, free air, cone up, in a makeshift stand. I have been running it at around Fs, 15 Volts. I couldn't measure the excursion, but it didn't look too excessive. The best I can calculate in WinISD it has been doing about 4 to 5 mm one way, for about 8-10 hours.

                      Well, this afternoon I came in to check on the progress to no speaker movement. The negative lead had popped off the back side of the spring terminal..... the ultra-thin-gold-plated-POS-lug had broken in half. Hmmm....the driver is rated at 800 watts RMS...at 8 ohms that is 10 amps. No way that paper thin connector would make that, let alone the mechanical stress of normal use. Another Peavey QC issue. It certainly was not being overdriven, and would have failed under normal use. Wow. I'm really a big Peavey fan now. That could be embarrassing to anyone, and what a let down it would be for someone performing live. I had to do a solder repair that wasn't fun.

                      It appears the suspension has loosened up a little bit, Fs and Q have dropped slightly, see attached snip. I am not sure how much more it will go, modeling it doesn't look pretty using the known measurements.

                      Naturally, I have not heard back from Peavey in reply to my initial email, and don't really expect to. I also posted it in the Peavey forums, but the folks there have other agendas.
                      Attached Files
                      Last edited by zhillsguy; 07-23-2012, 07:01 AM.
                      Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
                      Howard H

                      Comment


                      • #12
                        Re: Dual Pro Sub Placement?

                        I would see if you can return the driver to Parts Express (assuming that's where you bought it) and get a second Dayton PA-series woofer. That would resolve the question of dissimilar driver types operating together.
                        Best Regards,

                        Rory Buszka

                        Taterworks Audio

                        "The work of the individual still remains the spark which moves mankind ahead, even more than teamwork." - Igor I. Sikorsky

                        If it works, but you don't know why it works, then you haven't done any engineering.

                        Comment


                        • #13
                          Re: Dual Pro Sub Placement?

                          Originally posted by Taterworks View Post
                          I would see if you can return the driver to Parts Express (assuming that's where you bought it) and get a second Dayton PA-series woofer. That would resolve the question of dissimilar driver types operating together.
                          Thanks Tater.....unfortunately I didn't get it at PE. I got a "good deal" brand new from another website (wrong price, now corrected). In hind sight, I would have been better off and saved some dough. If I decide to get another Dayton later it is a drop-in for this box.

                          I am using it and it sounds good with the Dayton, but the specs never fell even close to published. This "taints" the brand permanently for me. I haven't given them the full run together yet, just in my small listening area inside.
                          Currently resigned to living in balmy Zephyrhills, FL with the snow birds.
                          Howard H

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