Settings speakers to SMALL, cut off at 90hz or 60hz

Discussion in 'Archived Threads 2001-2004' started by Dan Da Silva, Jan 31, 2002.

  1. Dan Da Silva

    Dan Da Silva Stunt Coordinator

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    Hey guys I have a quick question for you I have a Sony DB940 receiver, Paradigm Mini Monitors all the way around and a Paradigm CC-370 as my center. Now my problem is the DB940 has cutoffs at 60hz and 90hz, it doesn't have a cut off at 80hz which I know it THX standard. All of the Paradigm's go down to around 40-50hz. So what do you think I should set my cutoff at?? 60hz or 90hz. I have it at 90hz right now because I figured its closer to 80 and also 90 it will still roll off below that. Because I know its not a solid wall at 90. What do you think?
     
  2. Steve_Ma

    Steve_Ma Second Unit

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    I think you're on the right track. I'd keep em crossed @ 90.

    --Steve
     
  3. ling_w

    ling_w Second Unit

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    That depends how smooth the response your main speakers are in the 60-90 hz region. If it has massive peaks or dips, you could set the sub @ 90hz and try placements of the sub in which those anomalies would not occur. Otherwise, it would be better to cross @ 60hz. It will give you stereo bass down to 60hz, better integration of sub/main and less ability to localize the sub. A 90hz crossover means that it is only 3 or 6dB down at that freq, and 15 or 30dB (depending crossover slope) down at 180hz. 15 or 30dB below the primary signal @ 180hz is clearly audible and at that freq, localization at that freq will definitely occur.

    But if your mini-monitor can't handle the bass @ 60hz, then switch back to 90hz.
     
  4. BruceD

    BruceD Screenwriter

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    Dan,

    In my experience you will get a much smoother integration with sub and mains on most receivers if you give the xover a full octave to do it's blending.

    That means if 40Hz is the low point (-3dB) for the Paradigm Mini Monitors, then 80Hz would likely be the best xover. If 50Hz was the low, then 100Hz may be the best xover. I agree with Steve, and IMO the 90Hz xover is likely to be much better than 60Hz with your Paradigm Mini Monitors. Your sub will see a steeper crossover (roll-off quickly as frequency goes up) than your mains (roll-off slightly slower as frequency goes down).

    Your mini-monitors will produce even cleaner mid-range (less IM distortion) when they don't have to also try and reproduce lower bass notes at the same time which is handled better by the sub anyway.

    Room effects (called room modes or standing waves) can influence what xover frequency works best, but that is a more involved discussion for another time.

    ling's recommendation to use a 60Hz crossover for Paradigm Mini Monitors is rather unrealistic. His quote of, "It will give you stereo bass down to 60hz, better integration of sub/main ..." just doesn't make much sense.
     
  5. Bob_A

    Bob_A Supporting Actor

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    Didn't ling say it "depends how smooth the response [of] your main speakers are in the 60-90 hz region"? His statements seem reasonable to me.

    I say try out both crossover settings with a variety of your program material...and go with whatever works best for you. Good luck!
     
  6. Drew Eckhardt

    Drew Eckhardt Stunt Coordinator

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    IMHO, there are two paths to reasonable integration between mains & sub:

    1. Flat response 1 octave BELOW the cross over. This means half the frequency: -3dB at 30Hz for a 60Hz cross-over, 45Hz for a 90Hz cross over. Neither of these is the case, although the 90Hz cross over will get you closer.

    2. Acoustic + electrical roll-offs that sum-flat. IOW, the THX -12dB/octave @ 80Hz speaker roll-off mixed with a -12dB/octave @ 80Hz high-pass mated to a 24dB/octave electrical low-pass. I'm begining to think this is the ideal way to go, because you don't need to go to a ported system to get the necessary response (accepting the flabby mid-bass that goes with that) and don't need the larger cabinet (monitors seem to beat their floor standing counterparts in the upper registers, perhaps because of the smaller baffle and fewer resonances).

    IOW, try the 90Hz. If it offends you, try a flatter sub-woofer.
     
  7. BruceD

    BruceD Screenwriter

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    Bob,

    Take a dose of reality, we're talking about mini-monitors here.
     
  8. Bob_A

    Bob_A Supporting Actor

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    Bruce I'm not saying that 90Hz will not be preferrable in this situation...but it certainly can't hurt to try out 60Hz crossover as well.
     
  9. BruceD

    BruceD Screenwriter

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    Bob,

    You're right it can't hurt. It can be a real learning experience as well, clarifying what actually works in the real world.
     
  10. ling_w

    ling_w Second Unit

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    I don't think you could cascade 12dB/oct crossovers if they are not on the same electrical circuit. The phase shift characteristics might not be the same, they might be of different type, and the build in crossovers are terrible in terms of accurate freq centering. All these combined, along with others, you might end up with electrical nulls that will not be correctable with any equlization.

    The one octave extension is a good idea, I use it myself. But it cannot be the only determining factor. Bass integration is of higher importance, especially if the sub and main have different sound characteristics. You might also do the octave extension based on in-room response of your main speakers instead of the published specs.

    My mains has a dropoff @ 25hz (pre-shelf dropoff is around 36hz,) surround goes down to 70hz, center goes down to 160hz. I cross over the mains @ 50hz, surround @ 80hz and center to its own sub @ 150hz. If I use the 2x -3dB response for sub crossover, then I'll be crossing my sub for the center @ 300hz.

    Why do you think the better pre/proc all have adjustable crossover freq? People who buy them are not jumping for joy because they could adjust the freq higher. In almost all the cases, they want to bring it down.
     
  11. Lewis Besze

    Lewis Besze Producer

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    Ling,

    What kinda center you have?

    What Bruce is advocating is a good "rule of thumb"!

    Of course that bass integration is important,and find a good crossover point is good start.

    Having said that your center speaker has an unusualy weak lowend and it

    s crossed over to a sub directly,which could have aruably different characteristics then your main and surround speakers.Not too mention you croosed the center very close to it's low end[understanadably].Does the sub has any good usable output that high as well?
     
  12. ling_w

    ling_w Second Unit

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    Lewis,

    I have an all magnepan system. Center is MGCC1, Mains are MG-IIIa, Surround are MG-10.1.

    Center is rated to 160hz, it measure down to 150-155hz. Main is rated down to 35-40hz, but it shelfs down ~8dB from there, and drops off ~25hz. Surround is rated to 80hz, I get around ~70hz in my room.

    For the center sub, I would not compromise on crossing any higher than 155hz. If fact, the mfg specifies no more than 125hz due to the different type of bass that is produced. The surround is crossed @ 80hz. The mains are crossed @ 51hz. It is a compromise between 1 octave above cutoff and what it really should be. I was originally going to cross at ~60hz, but most people suggest crossing around 40-50hz, preferably 40hz. I stretched it to 50hz so that I could have a bit more headroom, but at a loss of bass integration with the mains.

    I had the mains crossover @ 80hz for a while along with the sub sitting in the rear. There were just too many instances where I though some part of the sound was coming from behind me.

    Plus, when I do freq sweeps, I could easily tell when the sound was moving from the mains (when crossed @ 80hz) or center to the subwoofer. The planar bass just sound different from the dynamic driver's bass.

    It would not have mattered if the mains went lower, since planar dipole rolloff is due to the rearwave wraparound effect, where the diaphram is still moving but is being cancelled by the out of phase wave coming from the rear. It is different from a ported design, where below the port resonance freq, it goes into a freefall, where the speaker could not handle anymore power. The center channel sub is a Hsu 10v, with dedicated high and low pass L-R 4th order crossover so that there is no deep bass subjected to the center when it does not have to. I would have gone for a 8", but none offers the flexibility of the Hsu 10v. But the Dr says the 10v is good for at least 160hz. Anyway, when I listen for integration, I might not be necesarily listening to something with very heavy center channel bass content (or even listening to it loud) where it might cause the center channel speaker to muck up the whole sound.

    Now magnepan is pushing the Outlaw ICBM magnepan edition. This way, the center would cross over to the mains, eliminating the whole bass integration issue completely for the center channel.
     
  13. BruceD

    BruceD Screenwriter

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    ling,

    I have never owned planers, but have listened extensively to a friends 6' tall magneplaners about 10 years ago and enjoyed them.

    Now I understand the context of your crossover comments, although I believe many of your ideas may work well with your planers they are not likely to work as well with direct radiator speakers. I'd guess >90% of HT systems use direct radiators of some kind (including horns).

    I do find your comments stimulating and thought provoking.
     

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