Anyone tried the Infinity RABOS EQ system

Discussion in 'Archived Threads 2001-2004' started by Stephen Dodds, Mar 21, 2001.

  1. Stephen Dodds

    Stephen Dodds Second Unit

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    I just picked up a pair of Infinity Prelude MTS and I was wondering if anyone has any experience with the RABOS system.
    Thanks
    Steve
     
  2. Tony Genovese

    Tony Genovese Supporting Actor

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    Steve:
    I ordered the kit from Crutchfield for $59. It includes a CD with 23 tones from 20hz on up to 100hz and a meter with LED's that show the level. The range is from 0db to -20db (I think).
    The meter seems more accurate than the RS meter. In fact I don't think it needs a correction factor, at least up to 100hz.
    The bugaboo of the meter is that since it uses LED's, it eats batteries for lunch (and breakfast and dinner, too). Figure a 9 volt alkaline will last one calibration. If you want to redo it, get a new battery. The instructions are very clear and I think you'll find it allows you to remove the main room peak you have. I don't own Infinities but do own a parametric EQ (Symetrix) with subs (2 Hsu TN1220HO's) and the RABOS helped me zero in the subs with very little fuss. Crutchfield offers a 30 day MBG, so what have you got to lose? BTW, I'm keeping mine - and signing up for Radio Shack's battery club : )
     
  3. Brian L

    Brian L Cinematographer

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    Finally, someone that has used this in comparison to the RS Meter!
    I posted a question about this some weeks back and got no takers. My hopes (and you may have confirmed it) is that the Infinity meter and Test Tones are designed to work together, and that the meter has appropriate averaging built in.
    The real PITA of the RS meter (as least the analog) is that for anything below 150-200Hz, the needle bounces around way too much (even on slow response). It makes taking room measurements an exercise in guesstimation! Its great to balance your overall speaker levels, but pretty useless (IMHO) to tweak an EQ.
    I read the write up at Crutchfields, and though there should be no reason that you could not use this to take room measurements and adjust an EQ; you don't really need the Infinity RABOS system to use the meter.
    FTR, I ended up using the demo of SpectraPLUS to adjust my Bijou, but the demo turns into a pumpkin after 30 days. It would be great to have a low cost handheld device to make adjustments in the bass region (the most critical area, IMHO). This sounds like just the ticket.
    Best Regards,
    Brian
     
  4. Patrick Sun

    Patrick Sun Moderator
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    This is why I got the digital version of the RS SPL meter, I don't have to deal with bouncing needle fluctuations. [​IMG]
    ------------------
    PatCave ; HT Pix ; Gear ; Sunosub I + III ; DVDs ; LDs
     
  5. Tony Genovese

    Tony Genovese Supporting Actor

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    But it evidently suffers from the same poor quality mic as the analog version.
    I was looking at a Gold-Line SPL meter for around $200. I called them and they said that it was really for broad band measurements and not tones and they could not guarantee the accuracy of the mic as they hadn't tested it for my intended use.
    So the Infinity filled the bill quite nicely for $60.
     
  6. Sundar Prasad

    Sundar Prasad Stunt Coordinator

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    When I run either pure sine tones or warbles (the warble tones move +/- 4 Hz around the centre frequency at a rate of 5 Hz, i.e. a 60 Hz warble will produce frequencies between 56 and 64 Hz), the RS Analog meter I use remains very steady when measurements are taken at the listening position. If there is any motion of the needle, it happens for the lower frequency (< 30 Hz) tones, and even then, the oscillation of the needle is never more than +/- 0.2 dB or so.
    Also, unless specific calibration curves have been provided for the Infinity SPL meter, it must be considered as accurate (or inaccurate) as the RS meter - IMO of course.
    Sundar
     
  7. Tony Genovese

    Tony Genovese Supporting Actor

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  8. Jack Gilvey

    Jack Gilvey Producer

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  9. Tony Genovese

    Tony Genovese Supporting Actor

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  10. Jack Gilvey

    Jack Gilvey Producer

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    I don't think I follow,Tony. If the Infinity is giving you the same readings as the corrected RS, I don't see how one can be considered more accurate (just given that evidence).
    (We already know that the raw RS is inaccurate, being that we have to add corrections. For the sake of argument, I'm considering the RS with corrections applied).
    The only "standard" against which it has been judged is the RS itself. I would think you'd have to compare it to the results from an RTA to see how close it gets.
    When considered as a system, as you say, I assume it should be accurate to eq those speakers, as any needed "corrections" should be accounted for.
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  11. Tony Genovese

    Tony Genovese Supporting Actor

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    Jack:
    Sorry if I was unclear. My point re the RS meter was that it was not necessarily accurate even with correction. I don't know whether the RABOS is accurate, but it has a better than fighting chance because it was designed to do what I'm using it for, measure low frequency sounds. The RS meter was designed to measure broadband noise (or sounds). I do find it interesting that the correction factor works with my RS meter, so perhaps the RS meters are fine for this purpose, provided you use the correction factor.
     
  12. Stephen Dodds

    Stephen Dodds Second Unit

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    The RABOS mike and the corrected RS mike through Spectraplus give similar eadings in my tests as well.
    The problem with RABOS is not the measuring, but rather that the EQ system in the subs doesn't appear to do a lot.
    Steve
     
  13. Jack Gilvey

    Jack Gilvey Producer

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    OK, Tony, I see, and I agree.
    There is a chance, I suppose, that they are both accurate.
    What I mean is that it would be quite a coincidence for both units , given that they read the same, to be off by exactly the same amount at each common frequency. It may be that they're both reading pretty close to reality, close enough for the purposes of home theater, anyway. I personally would think that more likely, but that's pure conjecture.
     
  14. Patrick Sun

    Patrick Sun Moderator
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    Here's a way to mod your RS SPL meter: Analog or Digital versions. The mod supposedly relieves the need for corrections down to 20Hz, but you'll need to mod the mic for anything over 10KHz or so.
    I have not tried the mod...yet.
    ------------------
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  15. Tony Genovese

    Tony Genovese Supporting Actor

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    I just bought an RS analogue meter. I will test it against the digital I own to see if they measure the same. Given the correction chart that is supposedly one size fits all, they should measure the same (prior to correction).
    Tony
     
  16. Jack Gilvey

    Jack Gilvey Producer

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    I'd like that comparison,Tony. I've got the digital model, and I've always just used the corrections as posted. Not really sure if that's correct,though.
    This thread has some info. on the corrections and their applicability.
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  17. Tony Genovese

    Tony Genovese Supporting Actor

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    OK, here are the measurements.
    Broadband pink noise:
    Analog 75
    Digital 75
    Freq Ana Dig
    100 83 84
    95 82.5 84
    90 80.5 82
    85 78.5 80
    80 77 78.5
    77 77 78.5
    72 75 77
    66 70 71.5
    63 68.5 70
    56 65 66.5
    52 64 66
    49 64 65.5
    46 64.5 66
    43 67 67
    40 69 69
    38 72.5 73
    35 72 73
    30 72 73
    26 72 73
    24 72 73.5
    22 72 74
    21 71.5 73.5
    20 71 73
    Well the two meters are within 2db of each other over most of the bass range. On broadband noise they measure pretty much the same. Not sure how useful this was, but there it is anyway.
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  18. Tony Genovese

    Tony Genovese Supporting Actor

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    Just reran the tests using the RABOS.
    Results as follows:
    Freq DB
    100 84
    95 84
    90 82
    85 80
    80 79
    77 79
    72 78
    66 75
    63 75
    56 73
    52 71
    49 71
    46 73
    43 75
    40 76
    38 77
    35 77
    30 77
    26 78
    24 79
    22 79
    21 79
    20 79
    I used the RS meter to set the initial sound pressure level and then adjusted my readings based on what the RABOS meter gave me for a deviation from the initial measurement. The RABOS reads in minus dbs not actual numbers.
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  19. Jack Gilvey

    Jack Gilvey Producer

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    Thanks for the results, Tony. You do get some lift @ 20Hz, don't you? [​IMG]
    I think that I must get some lift extremely low in my room, as the T-Rex footsteps from "Jurassic Lunch" (Telarc's Great Fantasy and Adventure cd) shook my room with a single 1220, and they're supposed to be 12Hz signals.
     
  20. Jones_Rush

    Jones_Rush Stunt Coordinator

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