can somebody help identify this anomaly for me?

Discussion in 'Archived Threads 2001-2004' started by Rob Michaw, Jan 11, 2002.

  1. Rob Michaw

    Rob Michaw Stunt Coordinator

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    Running my system analog direct vs. stereo (utilizing the sub and 80Hz XO) on CDs creates this anomaly that I am talking about.

    Equipment:

    Receiver - Integra DTR 7.1

    Speakers - PSB Image 4T

    Sub - Paradigm PW-2200

    When I run a signal in DIRECT mode (bypassing all) from my CD player, I am getting a distinctly fuller sound. When I run the same signal in STEREO mode (cutting mains at 80Hz and redirecting below to sub), my sound is less full...but the lows go deeper.

    My mains play down comfortably to 40Hz, but my sub plays to 20Hz. I have calibrated my sub to blend as well as I can at the 80Hz crossover point, yet my mid-bass seems lacking when using the STEREO mode.

    What is probably happening? Do I have a hole, or are my speakers exhibiting a hump in my room in the upper/mid-bass range that is eliminated by the use of a calibrated sub?

    Just curious...as this does not make much sense to me.

    Thanks.
     
  2. Clinton McClure

    Clinton McClure Casual Enthusiast

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    How are your tone controls set? It is possible the bass control is turned up a bit and is exciting certain frequenies in your room. Other than that, I do not know...
     
  3. Saurav

    Saurav Cinematographer

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    When you run things in Stereo, it's quite likely that your receiver converts the analog inputs on the RCA's to digital, does the bass management in the digital domain, and then re-converts things back to analog. It's quite likely that your hearing is sharp enough and your speakers are revealing enough that you can detect the effects of this back-to-back A/D and D/A conversion. Remember that there's already been a D/A conversion in the DAC in your CD player, so any subsequent digitization and un-digitization (I just made up that word) can only hurt the sound, not improve it.

    If you run things in Analog Direct, I guess you don't get any bass management, so nothing gets sent to your sub, which is why you get more bass the other way. You'd have to hook up your sub differently if you want to use it in Analog Direct more - use the speaker level connectors and feed it the full-range speaker signal from your amp, or use an external line-level crossover like the Paradigm X-30. Either of these would mess with the way you use your sub for HT though, if I'm not mistaken.

    Edit: The midbass dip may be due to phase cancellations between your mains and your sub when in Stereo mode.
     
  4. Rob Michaw

    Rob Michaw Stunt Coordinator

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    Tone controls are bypassed and set to 0 regardless.
     
  5. Rob Michaw

    Rob Michaw Stunt Coordinator

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    Saurav -

    Interesting thought. It never occurred to me. I thought the A-D-A conversion in the receiver would be more transparent and less destructive to the signal. Maybe not.
     
  6. Craig F

    Craig F Second Unit

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    One thing to check is when using the stereo mode (where the receiver is doing the bass management) that your sub's crossover is disabled or set to the highest position. The Integra does an 80 Hz crossover, if your sub were set lower than 80Hz the frequencies between 80 and the sub level would be missing.
     
  7. Pete Mazz

    Pete Mazz Supporting Actor

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  8. Saurav

    Saurav Cinematographer

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  9. Bob_A

    Bob_A Supporting Actor

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    Is it possible that the bass information below 80Hz coming from your two loudspeakers is leading to a fuller sound and more convincing or "coherent" soundstage than what you are getting from having everything below 80Hz sent to your external sub?
     
  10. Rob Michaw

    Rob Michaw Stunt Coordinator

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    Bob_A -

    If so, I was wondering why. It does sound fuller in the upper-mid bass...just won't go as low.
     
  11. Bob_A

    Bob_A Supporting Actor

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    I have always felt that the ability of a loudspeaker to reproduce bass is not irrelevant, even when used with an external sub. Let's consider blending between highs/mids/lows with your louspeakers...one, it is controlled entirely by the manufacturer...and two, the woofers are located literally right next to the other drivers. And having bass information spread out for both main channels as opposed to one point source is probably what leads to a more "cohesive" soundstage. I have suspected something of this sort for a while...but I do not have an external sub to use for comparison purposes. Thank you for sharing your experiences!
     
  12. Legairre

    Legairre Supporting Actor

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    Guys,

    I've tried my mains set to small, but I get a very thin sound. With my speakers set to large the sound is a lot fuller and the soundstage is better.
     
  13. Lewis Besze

    Lewis Besze Producer

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    You have bass cancellation,when you have your main set to "large".It seems like it occures around 50hz or so,and probably not too wide bandwith either.However it seems that you have other "problems" as well,since you not happy with the other setting as well[small].
    My recomendation is to move your'sub and read this thread as well:http://www.hometheaterforum.com/htfo...threadid=37784
     
  14. BruceD

    BruceD Screenwriter

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    Legairre,

    My guess is the issue with thin sounding mains on small is due to a crossover frequency that doesn't match well enough with the mains and sub.

    Does your receiver/prepro have options for crossovers? It sounds like the receiver/prepro's crossover may need to be set slightly higher let the sub do a bit more.

    Would you be re-directing the front bass and LFE to one sub or two? You could be experiencing a combing effect (cancellation) with two subs up front in different locations.
     
  15. Legairre

    Legairre Supporting Actor

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    Bruce,

    You could be right. Until I get a pre/pro with an adjustable crossover I'll have to leave them set at large. My plans are to get an Outlaw, Rotel, AT or one of the other new pre/pros when they come out. Right now I'm using my Denon 3300 receiver(fixed crossover of 80hz for the mains) with my Rotel 1095 amp. I shouldn't have to wait much longer.
     
  16. BruceD

    BruceD Screenwriter

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    Legairre,

    That should be fun.

    Good luck.
     
  17. Doug_B

    Doug_B Screenwriter

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    Hmmm, it was assumed by a few folks (and not specifically refuted by Rob) that the Stereo mode was used on the same analog inputs as the Analog Bypass mode. Is this true, Rob? If so, does your CDP have a digital output and did you try using this with stereo mode? You should, as you eliminate a D/A and an A/D conversion. If necessary due to constraints with the Integra (with which I am unfamiliar), connect/assign the digital input to a different device than the CD audio input.

    In any case, I would guess that room effects coupled with interplay between mains and sub are causing the observations reported.

    Doug
     
  18. BruceD

    BruceD Screenwriter

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    Rob,

    Answering these questions may help zero in on the anomoly:

    What is the manufacturer and model# of the CD player, and how is it connected to your Integra receiver ?

    What are the current control settings of your sub:

    1) crossover - On/Off

    2) crossover frequency - frequency #

    3) phase setting - 0, 180 or some other #

    4) volume - 9 o'clock, 12 o'clock or what

    5) any other control settings
     
  19. Rob Michaw

    Rob Michaw Stunt Coordinator

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    Doug_B -
    STEREO mode is used on the same analog input as DIRECT. My CDP does not have a digital out. My CDP sounds better either way than does a digital signal sent from my DVD to my receiver and then converted.
    BruceD -
    CDP is NAD 523 connected analog through Tara Labs Prism 55.
    Here are the settings:
    - Crossover on in STEREO
    - Crossover frequency set to 110Hz
    - Phase = 0
    - Volume = 1-2 o'clock
    My receiver's crossover is set at 80Hz. I have set the sub to what I think calibrated properly using an analog SPL meter and the Avia disc.
    This is a quick mock-up of my room layout:
    [​IMG]
    I have acoustic ceiling tiles, a cushy berber carpet with thick underpad, some furniture, and bookcases at the "open area" of room (left hand side).
    That is pretty much all I can think of. Thanks.
     
  20. BruceD

    BruceD Screenwriter

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    Rob,
    Have you defined your main speakers as small? I know you're using the 80Hz crossover in the receiver.
    I'm not familiar with the AVIA test disk, so I can't tell you how to calibrate the sub with it.
    You could use the Stryke bass test disk for $10 I think here and actually measure the bass frequency response in your room of the sub and main speakers by themselves. You could even measure bass frequencies in the STEREO mode vs the Direct mode and check the differences.
    This would also let you check for any changes in response due to you moving the sub or main speakers.
    You simply enter the SPL readings at each frequency on the test disk into an excel spreadsheet and then graph them with a logarithmic scale on the x or horizontal axis.
    This may still be a calibration issue, since the system sounds better to you with the Direct mode (analog pass-thru) and no bass management.
     

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