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Discussion in 'Speakers' started by steveHo, Dec 24, 2004.

  1. steveHo

    steveHo Auditioning

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    Hi all- I'm new to this forum. I'm looking forward to learning a bunch from all of you. For now, here's my setup:
    Mitsu 26" standard tv
    Onkyo TX-DS 595
    Panasonic R31 DVD
    Sony VCR (cheap)
    Infinity RS-2000 front speakers (L/R)
    KRK Rock-it Rear surrounds (L/R)
    no center channel
    QRx 218s subwoofer

    I want to go with a Sony XBR 34" tube HDTV eventually, along with matching speakers for L/C/R and RL/RR. I also would like to upgrade to the Onkyo TX-SR702, but that can wait as well.
    I think the sub is fine but I'm only pushing it with 1/2 to 1/4 of the rated power. It only goes down to 31 hz, is there much more below that?

    My room is 12' wide, 20' long, 11' high.

    Looking forward to plenty of discussions!

    Thanks.
     
  2. Arthur S

    Arthur S Cinematographer

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    Steve

    Welcome to the Forum and happy holidays.

    Yes, there is significant bass below 31Hz. At a minimum, you want a sub that can deliver 105 db (in room, not groundplane) from 25Hz to 63Hz with less than 10% Total Harmonic Distortion (THD).
    I will let some of the other sub enthusiasts run with the ball from here.

    Artie
     
  3. steveHo

    steveHo Auditioning

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    How much is below 31hz? 31hz is the -10db drop off point for these subs. If I had the appropriate sized amplifier, this sub will do 139db. Is that ok enough, even if it doesn't go down much lower than 31hz? I'll try to find a sweep and see how low it goes.
     
  4. Arthur S

    Arthur S Cinematographer

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    Don't know what kind of sub is rated for 139 db. That sounds like a mistake. 109 db is more like it. 139db would require something like a dozen 18 inch drivers in a cabinet literally the size of a room.

    Also, if your sub is down 10 db at 31Hz, the useful response is really about 40Hz. The only thing I can think of that might do 139 db is a large professional stage speaker, the kind used in live concerts in substantial spaces. So you are missing at least an entire octave (40-20) plus some.

    What is the name and model of your sub?

    Thanks

    Artie
     
  5. steveHo

    steveHo Auditioning

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    Yes it is rated for 139db peak and 133db program. It is a pro sound speaker. I run a small sound production company and we use two of these subs for about 5,000 sq ft. I only use one in my 240 sq ft living room, the other sits in the garage.

    I am only running it off about 1,200 watts, and it can handle 4,800 watts peak.

    I just wasn't sure how much material was below the 31hz on dvd's. Sounds like I may be missing a bit.

    It is an Electrovoice speaker, QRx 218s dual 18" subwoofer.
     
  6. Arthur S

    Arthur S Cinematographer

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    Yes

    Rated -10db at 31Hz means the usefull response is 40Hz. You are missing the entire 40-20Hz octave plus everything below 20. Volume is great, but instead of thinking that you are only missing 31 and below, you are missing a lot in that 40-20 octave.

    If you search this forum using the word "waterfall" you might find some interesting stuff about content well below 20Hz on DVDs.

    Artie
     
  7. Eric C D

    Eric C D Second Unit

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    You may think this sounds rude now, but once you look into it, and maybe try out a sub that gets down to 20 hz fairly flat, it should make more sense:

    I think you need a subwoofer for your powered pro-woofer. [​IMG]

    Yes there's a lot on DVDs in the 20-40 Hz octave. I think you'll find that your pro-subwoofer should stay used for musical performances, and that you should look at a different product for your audio system at home.

    Best of luck,
     
  8. steveHo

    steveHo Auditioning

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    I agree that I should do that as well. But since I already own the pro-sound subwoofer, it'll do until I have more funds next year. Then I'll look at something that'll do 20hz.

    I know that I speak from more of the prosound side of things, but what about the Bag End series of subwoofers? With their controller, they claim 8Hz. I know that you'd spend at least 2k on their products, but I've been considering them for my prosound gear as well. In the prosound arena, they are known for going very low.
     
  9. ScottCHI

    ScottCHI Screenwriter

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    stage subs are not the same as ht or hifi subs
     
  10. Parker Clack

    Parker Clack Schizophrenic Man
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  11. Arthur S

    Arthur S Cinematographer

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    The Bag End claim of 8 Hz is smoke and mirrors. Due to the design, Bag End has to apply a tremendous amount of bass boost. The driver can't really handle it and output below about 32 is compromised. The ear needs about 105 db at 8 Hz to be audible. The Bag End can do about 70 db. So it is only about 35db short of useful at 8Hz.

    You need something that is strong from 40 down to about 16Hz. The Bag End is exactly the wrong thing for your home use on a limited budget. If on the other hand you had the resources of a major movie studio, you might choose to use rows of Bag End. The studio that did Black Hawk Down used 22 Bag Ends to mix the sound track.

    Bag End has one design philosophy, but what they can do in the pro sound arena I can't say. I have a feeling they don't do the bottom octave any better. You may think this sounds rude now, but the pro sound realm is not big on the bottom octave. It is much more about high volume from 35Hz up as your current pro sound woof demonstrates well.

    You don't have to spend much to get a sub that can do 20Hz.
     
  12. steveHo

    steveHo Auditioning

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    I am coming quickly to that conclusion based on what is said here, as well as looking at the waterfall charts.

    My pro sound sub doesn't need to do the lower octave because most of the music doesn't get that low. 35hz on up is ok. But with the synth sounds on dvd's they can get that low. Well, when I get the funds, I'll pick up a sub that goes down to at least 20hz. But for now, I can still shake all the walls in my house with this sub.

    Just for kicks, I played an audio track that has a fundamental bass note of 23hz (as shown by that waterfall software). It shakes the walls and I can feel it in the couch / floors / walls, but it probably isn't at the correct levels compared to the rest of the spectrum.
     
  13. Arthur S

    Arthur S Cinematographer

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    That's good Steve. but remember you are probably hearing the harmonics of the 23Hz fundamental, especially the 46Hz second harmonic. Your woof would put out a lot at 46Hz and since down 10 db at 31, next to nothing at the true fundamental of 23. As the fundamental goes down, woofs put out more and more harmonic distortion. At 23Hz you are probably getting several hundred percent harmonic distortion. A ton of 46Hz second harmonic will shake your room. There are excellent woofs starting at about $430.

    Artie
     

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