speaker setup: a bass management question

Discussion in 'Speakers & Subwoofers' started by PaulDA, Feb 28, 2004.

  1. PaulDA

    PaulDA Cinematographer

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    This may be a silly question, but for anyone who's seen my recent, lengthy post about speaker shopping, you might understand my brain cramp.

    As I auditioned some Paradigms, (Monitor 5s at four corners with cc-370 as centre) the salesguy suggested setting them all to LARGE on my receiver and using the sub crossover setting at just about roll off (somewhere around 50/60hz, depending on the sub's variable settings) rather than the often suggested "standard" of 80hz, speakers to SMALL all around. For music, this worked beautifully, as the blend between mid-bass and lower bass appeared seamless. I did not test this with movies however.

    Later on I auditioned some B&W CM2s as mains, with DM600 S3s as rear surrounds and CMC centre (the DMs are necessary to stay in budget). I really focused on the CM2s in stereo mode w/o a sub and though their frequ. resp rates them at a higher cutoff on axis than the Paradigms (65hz vs 58hz), I found their bass phenomenal despite lacking a sub. The DMs are rated even higher at 75hz. I realize that it comes down to trying and hearing what I like. (I also know that these are two very different sounding speakers, see my lengthy post on my sonic epiphany for more details). Ultimately, though, I'd just like to know what's happening to the bass if I set all of these to LARGE, and set the sub crossover at 80hz, in this case. I know that each speaker will receive a full range signal but does this mean they will simply be overwhelmed by the lower frequency or will they play the frequencies they can and let the sub fill in the bottom (this applies to both sets of speakers)? This latter scenario is what the Paradigm dealer says will happen. If so, then why would anyone set their speakers to SMALL, unless they are truly tiny and would implode from the pressure? I have a vague understanding of crossover slopes and etc., but not enough to answer my own question.

    My concern here is to avoid the phenomenon of "double bass" that I've read about, though not experienced, when full-range towers are said to double the bass of the sub in certain bass management situations (over on the Outlaw Audio forum, there was quite a discussion of this about a month ago but I didn't understand all of it). Parenthetically, I'd like avoid abusing which ever set of speakers I end up purchasing.
     
  2. Philip>L

    Philip>L Stunt Coordinator

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    One reason for setting speakers to small when using a POWERED subwoofer is to take the stress off of the main amplifiers which work their hardest when driving very low frequency sound. By allowing the sub's amp to do the low end grunt work you will probably produce a better mid-woof through treble sound from the mains.
     
  3. Zack_R

    Zack_R Stunt Coordinator

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    IMO, the best way to determine what combination of settings offers the best sound and best response is to take matters into your on hands.

    Get yourself some test tones and a sound meter. I prefer 1/12 octave spacings but many enthusiasts use 1/6 octave spacings with good results. Set your speakers and sub any way you want and then play the test tones and record the results.

    The test tones I use start at 100 hz and go down to 10 hz. What I do is play the 100 hz test tone so that the sound meter records 80 dbs at the prime seat. Then, without touching the volume control, play each descending tone and record the results. Once you are done you can graph it manual on paper or in a spreadsheet program. Then try another combination. When you are done there will be one graph that will stand out as the best.



    I have done this with my mains set to large and sub off, mains set to large and sub on and mains set to small and sub on. I have tried crossover settings from 40-120 as well. After spending an enormous amount of time I concluded that mains set to small and the sub crossed over at 80 hz works best.

    With few exceptions, most equipment combinations will yield the best results with the mains set to small and the sub crossed at 80 hz in the receiver. My main speakers house 15 inch woofers and I don't feel bad at all about crossing them over at 80 hz. The crossover is not a brick wall and they are still producing bass, albeit at a reduced level.

    I'd purchase the best sounding main speakers I could afford and not worry so much about where you may end up setting the crossover. I know I haven't explained that much about crossovers to you, I only know enough to be dangerous[​IMG]. But if you try this technique you will at least know which combination gives you the best results in your room.
     
  4. Jason D.

    Jason D. Agent

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    Zack,

    What speakers do you have. I have Def's 2000tl's which have 15" 's in them as well and are tri-wireable. I am struggling to pick the best setup for them. Just curious what you had.

    -Jason
     
  5. Zack_R

    Zack_R Stunt Coordinator

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    Jason,

    My speakers are very old (25+ yrs. I'm guessing)acoustic suspension Sansui's. They are actually a 4 way design that has a total of 7 speakers in each cabinet. Two horn tweeters, two 4 inch mids, two 6.5 inch mids and one 15 inch woofer. If I were not using a sub I would have purchased some other speakers by now. I still would like to upgrade at some point but the desire is not strong enough to get me interested in speaker shopping.

    The woofer itself has a very nice sound but does not extend flat below 45 hz without eq in my room due to the design.

    The other advantage of crossing over at 80 hz is you can really open up the clarity in upper bass and mid-range. When I run my speakers set to large the bass is fuller but the overall sound suffers. The same is true if I crossover the mains between 40 and 60 hz. 80 hz seems to really open them up in my room.

    A simple way to experiment with your ears is to turn your sub off, set the speakers to small and listen to different songs while experimenting with crossover settings. If you have a sub then you need not listen so much for which setting delivers the best bass but rather which setting opens up the clarity of sounds without sounding tinny.

    If you play back movies at or near reference level and crossover at 80 hz your mains will need to play bass uncompressed, unstrained down to 40 hz. This is due to non-LFE 105 db bass peaks in some movies. Even though your receiver may employ a cross over slope of 12 db an octave, the end result is that the main speakers will be asked to deliver bass from 90-102 dbs at the seat between 40 and 80 hz. Depending on your room size and seating distance, this can be no easy task for many speakers.

    My receiver uses a 6 db per octave slope and as such the requirements are even higher for bass in my speakers, 96-103 dbs over the same range at reference.

    There are some pretty killer high output non-LFE bass in movies. One such example is LOTR:TT during the marsh scene when the dragons wing's flap. I can turn the LFE off on my receiver and boy this scene contains a healthy dose of re-directed bass. There is LFE in this scene too, it just that I was really surprised at how much was re-directed bass.
     
  6. Dustin B

    Dustin B Producer

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  7. ScottCHI

    ScottCHI Screenwriter

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  8. MuneebM

    MuneebM Supporting Actor

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    Zack, I'd like to do what you've suggested with my set up. I am currently running my JBL towers (10" woofers) set to "large" because I'm afraid if I set them to "small" I won't be making the most use of those 10" woofers. I'd like to do this measurement test, I have an SPL meter but don't have the test tones (they're not on DVE and Avia as far as I know and I haven't seen them on either of my discs). Are there 5.1 test tones for this that I can burn onto a DVD-R or do I have to download wav/mp3 files and burn them onto a CD and play them back as 2-channel audio? Thanks.
     
  9. Philip>L

    Philip>L Stunt Coordinator

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    I did a quick search on the JBL website, and it says that the lower crossover frequency for your speakers is 850hz. If you set a sub crossover anywhere below 120hz and your speakers to small you'll still get A LOT of use out of your floorstanders. See my post above about why this might be a good idea...
     
  10. MuneebM

    MuneebM Supporting Actor

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    Thanks Philip. I understand why its a good idea to set the fronts to small as it takes a load off the receiver. However, with my fronts set to large, my AVR's crossover set to 80 Hz, and my sub's crossover set to 80 Hz, I really like the way everything sounds; its very full, with absolutely no holes in the frequency range (as with my old home-theater-in-a-box).

    I'd just like to know where I can get those test tones (preferably in 5.1 DVD format) so I can do the chart plotting Zack suggested. Can somebody please point me to the files I need, thanks.
     
  11. Philip>L

    Philip>L Stunt Coordinator

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    You might want to consider dialing the crossover on the sub up to its maximum, or using the crossover bypass if one is provided.

    Your AVR and Sub might have different crossover slopes, and it's also possible that even if they have the same slope that the slopes add together (positively or negatively) in an undesirable way.

    I don't know where you can find the kind of test disk that you're looking for...
     
  12. Nathan Stohler

    Nathan Stohler Second Unit

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    Try the NCH Tone Generator. It's shareware, and I used it to create test tones, and then I burned them to a CD.

    You can only do mono and stereo, but to test frequency response for your other speakers, you can connect the analog inputs of your CD player or DVD player to the multi-channel inputs of your receiver (if you have them) and use the multi-channel mode. Connect one of the analog outputs to the center channel input to test your center. Then connect both analogs to the L/R surround inputs to test your surrounds.
     

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