Use processor bass test tone for calibration or Avia bass test tone....

Discussion in 'AV Receivers' started by Todd smith, Oct 22, 2004.

  1. Todd smith

    Todd smith Supporting Actor

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    When calibrating my system with the internal test tones of my sherbourn pt-7000 processor for the main 7 speakers I get almost identical trim levels as I would using Avia for the same speakers. However the sub level between Avia and my internal bass test tone on the pt-7000 is way different and I am verry frustrated. Avia is about 5-7 db quiter than the test tone in the processor. Considering all other levels are the same between the two that means one is wrong and one is right as far as bass levels are concerned. I would usually trust Avia but it seems verry strange to me that I have to turn the sub up as loud as I do using avia to get 3db hot. I am using a pb2-ultra in a 12 x 17 fully enclosed room and I need the gain up around 2/5 the way which is not completely wierd, but with the test tones of the processor it is only up about 1/4 of the way on the gain which seems more correct with accordance to my room size. Of couse the bass at the corners of my room is way louder than at the listening position with the test tones according to the meter and moving the sub does not seem to help all that much. I can not move my seating area. Why is there such a difference in bass response between the two tones (Avia vs processor test tone)? I noticed in the avia sub setup menu that the tones are meant for a single sub system, so would the pb2-ultra qualify for this since there is two drivers or would it be considered a dual sub system at this point and avia will not work???? The pb2 ultra manual says you can use Avia so I asume this is not a problem. Which test tone should I trust? The quiet Avia or the louder internal tone of the processor?

    This is frustrating because If Avia is correct than that means the processor test tone is 5-7db hot automaticaly and if you add the average 2-3 db hot calibration you will really be running the sub 7-10 db hot when you think you are only running about 2-3 db hot.

    What do you guys think? This can be one frustrating hobby....

    My room is 12 x 17 fully enclosed with all the equipment on one end of the room (small sanus equipment rack in one corner, 36" tube tv on stand in middle and jbl s-38 speaks on bar stools on either side of tv. At about the 2/3 way point into the room sits the couch and I have about 4.5 feet of space behind the couch so I can be out from the wall and get good surround effects. I have 4 more s-38 on shelves to the side and rear of the seating area. According to what I have read, 2/3 should be a good response area. What is going on here?
     
  2. Kevin C Brown

    Kevin C Brown Producer

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    Do you have the speaker sizes and crossovers set correctly in the Sherbourn? (That's about all I can think of.)

    I have a Lexicon MC-8, but its test tones are very close to Avia's including the sub.

    I also just got my PB2-Ultra 10 days ago! Just checked, and I am at 1/4 on the sub's volume. But that doesn't mean much because my room, speakers, and amps are different than yours. (Plus, I don't run my sub hot. I am running it at 0 dB right now.)

    I would say trust Avia, but what you could try, is to pick a few CDs and DVDs that you are more familiar with. Try both settings and see what sounds more correct.
     
  3. Brian L

    Brian L Cinematographer

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    FWIW, the bass tone in my NAD 762 (all speakers small, sub on) seems to be way low compared to Avia or the Chesky Ultimate DVD, meaning if I use it to calibrate, the bass would be too hot (have not quantified it, but its definetly too hot, and I am a guy who likes his sub a bit hot to start with).

    I would concur with KCB and go with Avia, then tweak a bit by ear.

    BGL
     
  4. Todd smith

    Todd smith Supporting Actor

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    My problem is the exact opposite. If I calibrate with avia it is much louder than if I were to calibrate using the test tone of my pre amp. Should I still trust Avia?
     
  5. Travis

    Travis Second Unit

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    I think one important aspect that hasn't been discussed is how the room is interacting with the test frequencies. Different manufacturers use different frequency ranges to calibrate subwoofers. I know that DVE uses a much higher frequency test signal then Avia. If the test signal that a certain program is emitting happens to be in a room null it could severely change how the subwoofer is calibrated. I would burn a disc with frequency tones on it and plot a graph to see how your room is interacting with them. This will help you to narrow down the culprit. As others have said also, I would adjust to suit your listening tastes. If you generally listen to movies at 15 below reference, being spot on is not as critical as if you listened at reference all the time. JMTC [​IMG]
     
  6. Todd smith

    Todd smith Supporting Actor

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    I have the autosound 2000 test cd #101, is this the kind of disk you are refering to? It has 30 sec freq seg of 10-98hz (tracks 10-98). Play these freq at about 80db?
     
  7. Travis

    Travis Second Unit

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    That one will work just fine. I would test at 1/6 octaves. I would try and keep it to around 70-80 db's. Plot a graph and see where you nulls and peaks are. This will help you better determine how your sub is interacting with your room. If you have a real bad graph you can always invest in a BFD to calm things down. [​IMG]
     
  8. Adil M

    Adil M Supporting Actor

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    How about this?
    When I calibrate w/ Avia I cannot get my Subwoofer SPL to be 3 db below the Right Front or Right Center SPL.
    I set the sub gain to the minimum and it just wouldn't go lower. I assumed I was in some room peak, but I turned that thing all the way down. I had already used Avia to equal out the speakers and then used the receiver test tone (*THX Select Onkyo) to make the bass the same level for now.
    I have the Avia faq by Guy Kuo in my laptop, so I know I was doing it correctly. Oh well.
     
  9. Todd smith

    Todd smith Supporting Actor

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    My graph was horrible. I tried the sub in all the possible spots in my room. The spot where I am getting the flattest graph is not my prefered spot for the sub. The worst graph ironicaly is where the sub sounds best to me on movies at least. This is because the 15-35hz region is peaked, but the 40-60 region is in a HUGE null. How can I bring up this null without moving the sub or seating postion? Is there a eq that can help with nulls and not just peaks? Are there freq specific bass traps that can target the 40-60hz region and how efective will they be? I need some other options here because I cant move my seating area and where the sub is the flattest I dont like because it is behind me (I dont like this for some reason) and the 15-35 region is considerably less even though the overall response is much flatter. What are some options?
     
  10. ChrisWiggles

    ChrisWiggles Producer

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    note that the sub tones in avia are via the main channels, so your bass management may be causing the difference. Avia may be revealing this behavior, which is why it's a good disc to use. The issue of room modes and things may also be involved.
     
  11. Todd smith

    Todd smith Supporting Actor

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    Thanks for your reply. What do you mean the bass management may be causing the difference?
     
  12. Adil M

    Adil M Supporting Actor

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    This is quoted from FAQ

    AVIA Calibration Tip #6 -- Subwoofer Test Tones and Bass Management

    AVIA users have occasionally wondered why nothing comes out of their subwoofers during AVIA's subwoofer setup test tones unless their speaker sizes are set to "small." The test signals are working as they should, but AVIA is probably the first test material you've encountered which starkly reveals the effects of bass management. The subwoofer test tones in AVIA do not DUPLICATE the low bass information from the five main channels (front left, center, front right, surround right, surround left) into the LFE track. We could have duplicated the low bass information into the LFE track. This would have yielded subwoofer output whether one set speaker size to "large" or "small," but would also completely obscure how bass management is actually working. With AVIA, what you get at your subwoofer is only what the bass management system in the receiver is doing, not what we put in the LFE channel. Duplicating the low bass information into the LFE channel would make more systems APPEAR to function as users expected, but wouldn't clue them into what is actually happening in their system's bass management.

    You may well discover that setting main speaker sizes to "large" completely stops a receiver's bass management from routing low frequency information in the main channels to the subwoofer. This means a lot of people are finding out that the bass management in their receivers isn't quite doing what they believed. Actually getting low bass information from the main channels to the subwoofer often requires one to set the speakers sizes to "small." Most users don't expect this to be true in their equipment and are shocked to find nothing coming out of their subwoofer when speaker size is set to "large." ----- > If your system behaves this way with the AVIA subwoofer test tones, this is also what it does to low bass in the main channels of a movie sound track. < ----- You may not have realized that you have been relying on only your main speakers to reproduce low bass in the main channels and the subwoofer has ONLY been producing low bass from the LFE channel. AVIA's subwoofer setup tones reveal this facet of bass management.

    Many receiver and speaker systems are actually more appropriately set to "small" size despite their having "full range" speakers. This allows the subwoofer to receive and reproduce low bass from all the channels rather than only the LFE. The "large" setting implies that the speakers are capable of reproducing the pounding LF effects one usually gets from a subwoofer in a home theater setup. At least try it both ways to see which yields better results in your system.

    Sometimes bass management limitations make it objectionable to set speakers to "small." Perhaps one has full range main speakers, a high crossover frequency in the receiver, and a sub which does not integrate well in the low-mid bass. The resultant gap in coverage is difficult to fix. A more flexible audio processor or some creative feeding to the sub of bass from main speakers (set to large) + bass from the LFE track may be needed. Two channel listening of music also comes to mind as a special situation.

    AVIA's subwoofer setup tones reveal how your equipment's bass management system actually deals with low bass. This gives you a chance to understand and optimize bass management on your equipment.


    --------------------------------------------------------------------------------

    Guy Kuo
    Director - Imaging Science Foundation Research Lab
    Video Test Design - Ovation Multimedia / Home of OpticONE Colorimeter, AVIA and Avia PRO
     

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