tower speakers and 80 Hz sub crossover: bass management?

Discussion in 'Archived Threads 2001-2004' started by Jeff Meininger, Nov 1, 2002.

  1. Jeff Meininger

    Jeff Meininger Second Unit

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    I'm thinking of upgrading my cheezy sattelites (crossed over at 120 Hz) to some floorstanding tower speakers at some point in the future. My Onkyo SR500 receiver allows crossover settings of 80, 100, and 120 Hz. If my towers are -3db at 40 Hz, wouldn't I want a crossover setting of around 60 Hz?

    In other words, with an 80 Hz crossover, aren't bookshelves with an F3 of 60 Hz every bit as good as towers with an F3 of 40 Hz (all else being equal)?

    I thought my entry-level receiver might simply have more limited options when compared with better receivers, but it turns out the Onkyo SR600 and SR700 also limit your choices to the same 3 settings.

    So what's up with bass-management and tower speakers? If they're too small to run full range and have to be crossed over at 80 Hz, are they a waste?

    I couldn't find anything that quite answers this question in the HTF "primer for home theater newcomers". It seems like this question would be in FAQ territory, though...
     
  2. GregLee

    GregLee Stunt Coordinator

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    Powered subwoofers generally have an adjustable crossover going lower than 80Hz, so possibly you could set up to use that, if you want to use more of your other speakers frequency range. However, I've seen the rule of thumb that the frequency response of mains should go down one octave below the crossover, so if you select an 80Hz crossover on your receiver and your other speakers go down to 80/2=40Hz, that may be about right.
     
  3. JohnDG

    JohnDG Stunt Coordinator

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    I concur with Greg's comment.

    In addition... it depends. I have a couple of smaller towers (Paradigm Monitor 7) that do +/- 2 dB to 47 Hz, so I defaulted to 80 Hz for the crossover.

    However it still sounded a bit boomy, so I checked the frequency response curve from 140 Hz down through the crossover. It turns out that I was peaking from 95 thru 75 Hz due to my limited options for placing the towers (corners) due to my room layout. By moving the crossover up to 100 Hz ( ) I found that the peaks lessened as the bass load in this range started to go over to the sub (SVS).

    The idea is: check out the crossovers for your room, and see which works best for your equipment and your room sound characteristics.

    jdg
     
  4. RichardH

    RichardH Supporting Actor

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    Jeff:
    You're not wasting the capabilities of the mains by running them as small (80Hz crossover). It's kind of like asking if you are wasting the capabilities of a Ferrari if you never drive over 100 mph. Well, in one sense maybe a little, but you still get great acceleration and handling, etc.

    Your towers will not be breaking a sweat to cover the stuff below the crossover point, whereas some bookshelf speakers might be.

    BTW, I'm from Austin too!
     
  5. Bill Kane

    Bill Kane Screenwriter

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    Buying speakers is like acquiring a boyfriend/girlfriend; everyone has his/her own ideas. So while a FAQ cud be prepared, is might not apply universally. I think it's good for A/Vers to rethink this process from time to time. I know I do it seems 2-3X a year, because it's a moving target.

    There's the "Cerwin-Vega" school that likes macho towers and likes to set LARGE. There's the bookshelf school that believes a really good subwoofer makes the difference in speaker system balance where mains can be left SMALL. There are the "just use subout line-level" connectors and the speaker-level "use the sub crossover control" school.

    It used to be we didnt have a crossover point choice: only what the receiver offered. Now there are choices. We can opt to set mains at LARGE temporarily for 2-Chl music, then return to SMALL for 5.1 DVD playback.

    As the above posters observe, much depends on room characteristics to sub peaks/nulls, the so-called room curve; conflicting bass phase betw mains and sub.

    Conventional wisdom tells us to just use the mains SMALL with a nice sub, and this probably applies to 90 percent of us. The argument goes:

    * The sub is far better at voicing the bass at 35Hz and below than most mains.
    * Sendng low bass to the sub relieves the mains from struggling and frees them to better voice the midranges.
    * Sending bass to the sub amp relieves a load on the receiver's amplifier/transformers.
    * An 80Hz crossover actually is a slope meaning the mains still will get a portion of the octave below that point.

    A bachelor may like honkin' towers in the room. A SO may object and prefer smaller boxes in the living/family room. So it goes.

    I dont think I am being too theoretical here. In practice, it's best to demo the different types of speakers and even get some take-home speakers for the weekend from a dealer.

    I ended up with mains rated 32Hz "low-frequency extension" or +/-2dB at 45Hz. Using a 25-31PC(Improved Driver) SVS, I prefer setting them to SMALL because the SVS is So Smooth and I get a sub response of +/- 3or4dB at 35-90Hz in my room, fortunately, sidestepping the need for an equalizer.

    Professionals, including Joe Kane of the new Digital Video Essentials test disk soon to come, are more and more emphasizing the need to take room characteristics into consideration when setting up the audio portion of our systems. So this is another aspect of why a one-size-fits-all FAQ wont work until we see what we have to work with.

    bill
     

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