My response measurment results....am I there yet?

Discussion in 'Speakers' started by JimmyK, Apr 7, 2003.

  1. JimmyK

    JimmyK Second Unit

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    I've been working on reintegrating my SVS 46-16PC+ with my main L&R speakers (ADS L1290's) since purchasing an Anthem AVM 20 v2.xx.

    The lowpass crossover on the AVM20 is set to 80hz and the highpass is set to 50hz. Setting both crossovers to 80hz resulted in a deep hole centered at 80hz, so I lowered the high pass filter to minimize this effect. I guess I could have raised the low pass filter instead, but I don't want to end up with easily localized frequencies coming from the sub.

    All speakers (including the sub) are set to read 75db on my Radio Shack digital spl meter. I am using an Audio Control 10 band graphic EQ on the L&R speakers only (no EQ on the sub) to tame a nasty bump between 85hz-125hz. Sub is located in the corner next to my L speaker.

    Measurements were taken using sine waves at fequencies 1/6 octave apart. If I measure frequencies in between, the response gets a little more ragged looking, but I expect this is normal. I ran the signals in stereo mode with both sub and L&R speakers on, since this is how I do most critical listening.

    Setting the meter to it's lowest setting revealed no response from background noise, so I'm pretty sure my measurements are not poluted.

    I am unable to post a picture of the resulting graph, so here are the numbers I came up with. The numbers include the correction values for the Radio Shack spl meter.

    16Hz....70.0db
    18......70.2
    20......70.5
    22......71.0
    25......72.0
    28......73.5
    31.5....74.0
    36......74.0
    40......73.5
    45......71.0
    50......70.5
    56......71.0
    63......69.5
    71......71.0
    80......67.5
    89......71.0
    100.....69.0
    111.....66.0
    125.....58.5
    142.5...61.0
    160.....59.5

    From 160 and up, the response stays around 61db until about 300hz or so, then rises to about 64db the rest of the way up.

    So my questions are:

    1. Does it appear my method of measurement is sound?

    2. Does this represent a good response? (It sounds good, but I always wonder if it could be better.[​IMG] I'm sure many of you here know what that's like!)

    3. What would you change, if anything?

    Thanks in advance for your input/advice!

    JimmyK
     
  2. JimmyK

    JimmyK Second Unit

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    OOPS! I meant for this to be posted in the Speakers section. Sorry!:b

    Could someone please move it?

    Thanks!
     
  3. Wayne A. Pflughaupt

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    Hi Jimmy,

     
  4. JimmyK

    JimmyK Second Unit

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  5. Zack_R

    Zack_R Stunt Coordinator

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    If it were me, I wouldn't sweat those numbers (100 hz and lower)! Unless you listen to pipe organ music the 4 db drop from 31.5 to 16 hz is not serious, IMO. Then again, it could be fun to try and flatten.[​IMG]

    If you had a 4db loss in slope between the 50-80 hz range I would say that's a different story. This is because most music has frequencies in this range. If your 4db hole was narrow then even in the 50 - 80 hz range I dont't think it would be a big improvement if fixed.

    Keep in mind that few DVDs have extremely low bass and if there is bass present it is probably LFE and LFE can be boosted by 10 db by the engineer. So I think you'll feel and hear those frequencies just fine.
     
  6. Edward J M

    Edward J M Cinematographer

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  7. JimmyK

    JimmyK Second Unit

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    Thanks for your response.

     
  8. Edward J M

    Edward J M Cinematographer

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    Jimmy:

    I didn't know you could select different filter points for each speaker. My experience with the Anthem is that it has a 4th order low pass (80 Hz) to the subwoofer and a 2nd order high pass to any main channel set as "small". The filter point is selectable in 10 Hz increments from 40 to 160 Hz, but I thought it applied the same filter point to all high passed speakers. Must be a revision in the bass management design (Version 2)?

    Regardless, setting the sub low pass and the mains high pass filter points to different frequencies is non-conventional, although I understand why you did this (to remove a hole at 80 Hz).

    Do me a favor if it's not too tough. Set the sub low pass and the mains high pass both to the same frequency (try 80 Hz again to start) and set the phase control on the 16-46PC+ to 180 and run the sweep again and report the results, particularly at the filter point.

    Regards,

    Ed
     
  9. JimmyK

    JimmyK Second Unit

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    Thanks again for the response.

     
  10. Edward J M

    Edward J M Cinematographer

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    I had a similar cancellation (8 dB) at 80 Hz with my 20-39PC+. I got lucky - setting the phase control to 180 completely eliminated the dip at 80 Hz, and also filled in the curve slightly (up 1-2 dB on average) from 80 down to about 60 Hz. I was hoping the fix would be as easy for you. Sorry I couldn't help more.

    Clearly, picking a 50 Hz high pass for the mains and an 80 Hz low pass for the sub will help "cover" that hole at 80 Hz, and I follow your logic here, and agree with the method.

    Overall, it's a decent looking curve for sure.

    Regards,

    Ed
     
  11. JimmyK

    JimmyK Second Unit

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    Edward,

    I certainly appreciate you taking the time to suggest a solution. That is one thing I love about this forum.

    In my particular case, I found that the hole at 80hz wasn't being caused by a cancelation, which would explain why it was there whether or not the sub was on. It seem to be cause by the particular crossover settings in the AVM20.

    Just as an experiment, I might try creating an overlap above 80hz instead of below. I'd like to see what happens if I raise the low pass crossover to 90hz or 100hz and the high pass to 80hz. We'll see if that causes some of the bass to become to localized from the sub.

    Thanks again![​IMG]

    JimmyK
     
  12. JimmyK

    JimmyK Second Unit

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    I tried some more experimenting, this time using 1/6 octave warble tones on the Stryke disc to get an average response rather than using specific sine waves. Am I correct that I shouldn't be overly concerned about very narrow notches in response that can show up when using sine waves?

    I started by turning the EQ off and trying different crossover settings. With both the sub and L&R speakers set to 80Hz, the large bump reappeared between 85hz-125hz. Out of curiosity, I started raising the crossover point for the L&R speakers while leaving the sub at 80Hz.

    This is the response I achieved with the sub set at 80Hz, L&R set to 150hz, and the EQ off. (includes Rat Shack meter corrections)

    16Hz........80db
    18..........80
    20..........77.5
    22..........76
    25..........77
    28..........78
    31.5........79
    36..........79
    40..........78
    45..........76
    50..........76
    56..........76
    63..........73
    71..........72
    80..........75
    89..........75
    100.........76
    111.........74
    125.........71
    143.........71
    160.........71
    201.........71
    254.........71
    320.........72
    403.........69
    507.........71
    640.........73
    806.........73
    1150........75

    Above 1150hz the response remains pretty flat around 73db up to 10khz then rolls off smoothly up to 20khz.

    A few things I observed this time.....

    I was surprised that setting the L&R crossover points to 150hz didn't result in a large hole between 80hz-150hz. As a matter of fact, it seems to have tamed the very large bump I was experiencing between 85hz-125hz without having to use the equalizer as before.

    Also, when using the equalizer to tame the large bump, I was ending up with a depression between 125hz-300hz as pointed out by Wayne. Looking at the graph I drew, it seems that depression has been improved considerably.

    I did some listening and didn't notice any holes between the sub and the main speakers. I'm sure if I used some specific sine waves I might be able to find some narrow ones, but I'm not sure if I should be concerned about it.

    I would appreciate any additional comments you may have about these new results (Wayne, are you still out there?).

    Thanks!

    JimmyK
     
  13. MingL

    MingL Stunt Coordinator

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    I've inserted your figures into the spreadsheet, interpolated some portions of the graph. Its easier to visualise whats happening this way.

    The graph below gives a graphical representation of how JimmyK's sub's response is (in blue).

    Mine's in red and green, one of them in stock 16hz tune, and the other tuned to 12hz.

    Both of us are using the exact same sub.... except in different rooms in opposite sides of the globe.

    [​IMG]

    I hope this is of some help.
     
  14. JimmyK

    JimmyK Second Unit

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    Thanks MingL!

    I have a graph I use at home, but do not have a way to add it to my posts. I really appreciate you posting the graph. You're right, it is easier to see what's going on looking at a graph.

    I have one question. According to your graph of my results, it shows a 91db level at 16hz. My results at 16hz was 80db including the correction for the Radio Shack meter. When you plugged my numbers in, did the graph add in the meter corrections in again? It appears as if the corrections were added twice.

    Thanks again!

    JimmyK
     
  15. MingL

    MingL Stunt Coordinator

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    dang, my mistake.......... didn't realise its been compensated...... right. Here's what it really should look like.

    [​IMG]
     
  16. JimmyK

    JimmyK Second Unit

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    Thanks!!! I really appreciate your help![​IMG]


    So what do you think? Should I forget about the equalizer at this point? Or is there anything obvious you see that would improve the sound?

    JimmyK
     
  17. MingL

    MingL Stunt Coordinator

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    Looking at your curve and comparing to mine, I'd say you can live without a BFD. I got the BFD so that I could remove any room-mode-induced peaks. You don't even have a peak to start with!

    Based on your curve just like that, I'd say no need for a BFD since there's no peak to tame away, coz thats the main purpose of getting one in the first place.
     
  18. Wayne A. Pflughaupt

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    Jimmy,

    Ming is right, that is excellent - indeed, amazing - response for not having a parametric equalizer in the picture.

    The only thing I can see that might need attention is the house curve. The start and end points are fine (100Hz and 36Hz) but the curve is relatively shallow – only a 5dB differential. You would have to have a really huge room – say, much larger than 6500 cubic ft. – for that curve to sound right.

    You might want to take a look at this link for some info on how to determine and achieve the right house curve for your room.

    Regards,
    Wayne A. Pflughaupt
     
  19. JimmyK

    JimmyK Second Unit

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    Thanks guys! I really appreciate your help!

     
  20. Wayne A. Pflughaupt

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    Judging from the chart Ming posted and your satisfaction with the way it sounds, I’d say you’re there!

    Regards,
    Wayne A. Pflughaupt
     

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