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Thread: Subwoofer Crossover and Integration

  1. #1
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    Mar 2012
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    Default Subwoofer Crossover and Integration

    Get your popcorn. Sorry for the length.

    I sit here not knowing how to broach this topic. It's a discussion I've always wanted to have, but doing so in the venues I've had available to me before has always led to very dogmatic situations. Either live or on various internet forums, opinions vary wildly in content, and vary minimally in their passion.

    But I am amazingly curious about this topic because I seem to be, and always have been, a weirdo about this topic: I like my subs crossed over as low as I can get them because if I don't, I can localize the sub.

    So have any of your 80hz folks, 60hz folks, 50hz folks (depending on what your equipment allows you to do)... played with running your mains (in this case I'm presuming Ascend gear) full range and crossing over the sub as low as it will go? 40hz... or lower?

    I've been told that there's measured evidence that says under common circumstances, the localization of frequencies at or below 80hz isn't possible, and that the common explanation for when it happens is that psycho-acoustic cuing from higher associated sounds lends to the localization. I've also been told that that sensitivity to lower frequency sounds is higher in males over females because of simple biological size differences.

    Have I read a publication record of either of these two statements? No. At the moment I don't care to. I'm just putting them here as examples of conventional wisdoms that seem to be prevalent.

    But regardless, a subwoofer in a dynamic musical or home theater performance doesn't strictly play things only below it's crossover point. I don't think I've ever seen a infinite db/octave slope on a consumer product. This means that the sub will indeed play some material above the crossover point, and this brings me to the meat of my point.

    My sub (HSU VTF-3 MK4) is not in the far field with my main speakers. I'd love it to be, but the compromise is furniture layout and room design. Because of this, the sub is in the nearfield acting as a coffeetable to the left of the couch. Temporarily last year it was in the far field next to the television cabinet. When integrating it post-purchase, as usual an 80hz crossover point drove me nuts. So much material was coming out of the sub above 80hz that getting the levels on things matched up to where I had a relatively flat response down to sub-20hz was impossible. 50hz was tolerable, but only if the mains were left full range. If I let the AVR cross them over, I could hear the stereo image going to crap in the bass voices.

    The Sierra's I recently purchased, set up and am currently breaking in do so well in my room down to 40hz that I can now bypass the AVR's crossover entirely and use the one on my sub to drop it down ~35hz. With the levels on everything balanced up I have a very, very difficult time now localizing bass information outside of the front stage. I'm waiting until the break-in hours are done before I go in and do crazy measurements on everything, but right now it's in a good place.

    So anyway, like I said. Any of you tried this? Thoughts on it? Opinions on what you heard?

  2. #2
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    Default Re: Subwoofer Crossover and Integration

    I have seen many people run their speakers fullrange, and then let the sub fill in below the speakers. Nothing wrong with that if your speakers are capable of handling the fullrange signal without issue.

    One reason to have a crossover is to relieve the speakers from attempting the reproduce the fullrange signal.

    In the end, what matters most, is how it all sounds to you.
    -curtis

  3. #3
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    Default Re: Subwoofer Crossover and Integration

    Agreed.

    Another reason for a crossover is to protect a driver from playing below a safe frequency passband relative to its abilities and the enhancement an enclosure design provides.

    Further agreement is that anyone's configuration should by all means match to their preference based on their perceptions as the sound is delivered. I do believe this in the fullest. I was just curious if folks around here, having mains that will indeed drop down very low, had fiddled with this configuration for any amount of time as to come to an opinion on it. Just seeing what folks thought.

  4. #4
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    Default Re: Subwoofer Crossover and Integration

    Interesting discussion here, Alleric.

    I will admit I've never tried low crossover settings (~40 Hz or lower) or run the mains full-range with the sub filling in below. Perhaps I'm a traditionalist, but I have always approached subwoofer integration from the notion of compromise. E.g. by using a subwoofer, I can gain authority and control with low-frequency content, but I must compromise on (possible) localization and "speed" of the woofer compared to the mains.

    Since discovering Rythmik Audio servo subwoofers, my notion of compromise is nearly irrelevant. I have had great success integrating the sub/mains and it's difficult to pick out the sub now. I can choose just about any crossover point (within reason) and get superb integration. I believe that is a testament of the quality for both the Sierra-1 speakers and the Rythmik F15.

    With that said, I usually run full-range for most music and run the sub for most movies (80 Hz for mains/rears and 60 Hz for center). When I'm in the mood for loud and lively (> 85 dBC avg), I'll use the sub for both music and movies to ease the load on the amp/speaker.

    Anyway, you got me curious here, so I think I'll play around with the very low crossover options this weekend, as well as "fill in" mode.
    -Jacob

  5. #5
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    Default Re: Subwoofer Crossover and Integration

    Cool. I would be very interested in your thoughts.

    As for running the mains full range for 2 channel stereo. For the vast majority of my music catalog that would handle things just fine. But, and I realize I'm probably in a minority here, I have several selections that have very necessary material down below 30hz, some electonic, some acoustic. To get that passband at a balanced volume level with the rest of the bandwidth, I simply must include a subwoofer. I own recordings that have material that plays down into the low teens if you account for interference patterns in organ pedal pitches, harmonized double bass material, or just straight up Daft Punk or Trent Reznor/Atticus Ross getting surly.

    But I still want that to sound like it's coming from the front soundstage, and the only way I've been able to pull that off is the super low tuning.

  6. #6
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    Default Re: Subwoofer Crossover and Integration

    Quote Originally Posted by Alleric View Post
    I own recordings that have material that plays down into the low teens if you account for interference patterns in organ pedal pitches, harmonized double bass material, or just straight up Daft Punk or Trent Reznor/Atticus Ross getting surly.

    But I still want that to sound like it's coming from the front soundstage, and the only way I've been able to pull that off is the super low tuning.
    For the same reasons, I crossover at 40hz for nearly all music and push it up to 80hz for movies most of the time. I'm not sure why I didn't think of it early but setting the center to 60hz is a great idea for movies.

    I thought I was nuts, but when I moved my sub from the right side of my setup to the left, I could tell where the sound was coming from (and not happy about it). I'm glad to hear I'm not the only one. Moving it back is going to be a chore due to internet hookup, router, etc., but this gives me the motivation to get it done.

    Sheep.

  7. #7
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    Default Re: Subwoofer Crossover and Integration

    I wish I could find the source, I'm still looking. My understanding is that THX did tests to determine crossover frequency where there was no localization, I presume using a standard setup where the subwoofer was in the same field as the main speakers. Some people lost localization @120hz, some @100hz, but all lost localization @80hz. That's how it became the "standard" crossover frequency.

    One thing to keep in mind is that the crossover frequency indicates the point where one speaker starts to handle more of the load than the other. In other words, the sub is producing higher frequencies than 80hz. THX specifies a steep 4th order crossover, 24db/octave. If for some reason the crossover is more gentle, I can see output from the sub being high enough at higher frequencies to lead to some localization.

    Use whatever works for you, but I think your speaker placement is causing your localization issues, not necessarily your hearing.

    When I ran Audyssey Multi-EQ on my AVR, it chose a 40hz crossover for my SVS PB12-NSD and Ascend 340's. I manually adjusted it to 80hz, which sounds better without localization.

  8. #8
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    Default Re: Subwoofer Crossover and Integration

    When the sub was in the plane with the mains, the only localization type differences I noticed in the bass range (with higher crossover points) was a narrowing of the sound stage. It all still sounded like it was coming from the front stage, because it was. The stage just seemed to slur down to a point at times on material I knew should have space to it. 50hz crossover minimized this enough that I was happy with it.

    Then, the sub had to move to its final resting place, to the left of the couch. Even at 50hz, the stage was getting pulled way left, and close. Doing pitch tests, I found that once I descended into the low 40's/high 30's, localization definitely, definitely vanished, and it sounded like wide environmental pressurization.

    Add the Sierras into the mix, and their ability to run full range really well with a solid soundstage, and the sub keeping that sense of expansion down in the seismic realm, and a very nice, large soundfield is sustained.

  9. #9
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    Default Re: Subwoofer Crossover and Integration

    By the way, and I don't think what I've stated before this has implied this correctly, I do not mean by any means pinpoint localization issues. I do not mean that I was running into situations where I could say "HULK SMASH! SUBWOOFER IS SITTING 3 INCHES OUTSIDE LEFT MAIN SPEAKER RAR!!!!" while music was playing. On dynamic material, it was mostly a noticing of the soundstage shifting, narrowing. Once it bugged me enough to look into it, and I started running sweeps and pitch tests with the mains and sub going at the same time that I could really hear at what point it started shifting.

    Dropping the crossover point to 50hz in the AVR remedied this a lot, but the problem returned once I moved the sub. Problem was that even though my legacy speaks could run full range... they just didn't have quite enough umph down below 50hz to let me go lower using the sub's crossover. Sierras have now remedied that.

  10. #10
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    Default Re: Subwoofer Crossover and Integration

    Are your sub and speakers in phase at the crossover point?
    -curtis

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