Tempest Results / In-Room Measurments

Discussion in 'Archived Threads 2001-2004' started by Kerry Hackney, Feb 5, 2002.

  1. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    I finally had a chance over the weekend to do some semi-serious measurements of the sub I built. I connected my multimeter and set the drive level at 3.02 volts @ 60hz. I wanted to get close to the 2.86 that is normally used. I could have fiddled with the sub amp and set it even closer but this should give you a good reference. This first set of measurements is with the SPL meter laying on the floor one meter from the edge of the cone. My 281s were also on, so you will see the hand off at 80Hz via the internal bass management of the receiver. I suspect I have some phase cancellation and will try reversing the input on the sub in the near future to see if things improve. I only have 180 degree options not variable phase.
    FrequencyCorrected Reading
    18Hz.104.29
    19Hz.105.35
    20Hz.104.50
    21Hz.102.92
    22Hz.102.38
    23Hz.102.88
    24Hz.102.42
    25Hz.103.00
    26Hz.104.62
    27Hz.104.27
    28Hz.102.95
    29Hz.101.65
    30Hz.101.38
    31Hz.101.12
    31.5Hz.101.00
    32Hz.100.97
    33Hz.100.91
    34Hz.101.84
    35Hz.101.78
    36Hz.102.72
    37Hz.102.67
    38Hz.102.11
    39Hz.101.55
    40Hz.101.50
    41Hz.102.26
    42Hz.103.18
    43Hz.103.09
    44Hz.102.99
    45Hz.103.90
    46Hz.103.81
    47Hz.103.73
    48Hz.103.66
    49Hz.103.58
    50Hz.103.50
    51Hz.103.50
    52Hz.104.00
    53Hz.104.50
    54Hz.104.00
    55Hz.104.50
    56Hz.104.50
    57Hz.104.00
    58Hz.104.00
    59Hz.104.00
    60Hz.104.00
    61Hz.104.00
    62Hz.103.50
    63Hz.103.50
    63Hz.103.50
    64Hz.103.00
    65Hz.102.50
    66Hz.102.50
    67Hz.101.50
    68Hz.101.50
    69Hz.101.00
    70Hz.100.50
    71Hz.100.50
    72Hz.100.50
    73Hz.100.00
    74Hz.100.00
    75Hz.100.00
    76Hz.100.00
    77Hz.99.50
    78Hz.99.00
    79Hz.98.50
    80Hz.98.50
    81Hz.98.52
    82Hz.98.54
    83Hz.98.57
    84Hz.98.59
    85Hz.98.61
    86Hz.99.14
    87Hz.99.66
    88Hz.99.68
    89Hz.99.71
    90Hz.99.73
    91Hz.100.26
    92Hz.100.78
    93Hz.100.81
    94Hz.100.33
    95Hz.100.36
    96Hz.99.89
    97Hz.99.92
    98Hz.99.94
    99Hz.99.97
    100Hz.99.50
    And here is the results at the listening position with a slightly higher drive output. Even this was indicated at less than 2 watts using the level meters on my amp. Also, my room is about 8000 cubic feet. This listening position is 15-16 feet from the sub/corner.
    FrequencyCorrected Reading
    18Hz.83.29
    19Hz.84.35
    20Hz.84.50
    21Hz.85.92
    22Hz.84.88
    23Hz.83.88
    24Hz.84.42
    25Hz.85.00
    26Hz.85.62
    27Hz.85.27
    28Hz.85.45
    29Hz.84.65
    30Hz.83.38
    31Hz.82.12
    31.5Hz.82.00
    32Hz.80.97
    33Hz.78.91
    34Hz.77.84
    35Hz.78.78
    36Hz.79.72
    37Hz.80.67
    38Hz.79.61
    39Hz.79.55
    40Hz.78.50
    41Hz.78.26
    42Hz.79.18
    43Hz.79.09
    44Hz.79.99
    45Hz.80.90
    46Hz.82.31
    47Hz.82.73
    48Hz.82.66
    49Hz.83.08
    50Hz.83.00
    51Hz.83.50
    52Hz.83.50
    53Hz.84.00
    54Hz.85.00
    55Hz.85.50
    56Hz.85.50
    57Hz.86.00
    58Hz.86.50
    59Hz.86.50
    60Hz.87.50
    61Hz.86.50
    62Hz.86.50
    63Hz.87.50
    63Hz.87.50
    64Hz.87.50
    65Hz.87.50
    66Hz.87.50
    67Hz.87.50
    68Hz.87.50
    69Hz.87.50
    70Hz.86.50
    71Hz.85.50
    72Hz.84.50
    73Hz.83.50
    74Hz.82.50
    75Hz.81.50
    76Hz.81.00
    77Hz.80.50
    78Hz.80.00
    79Hz.79.50
    80Hz.78.50
    81Hz.78.52
    82Hz.77.54
    83Hz.77.57
    84Hz.77.59
    85Hz.77.61
    86Hz.77.64
    87Hz.77.66
    88Hz.77.68
    89Hz.78.71
    90Hz.79.73
    91Hz.80.76
    92Hz.81.78
    93Hz.81.81
    94Hz.81.83
    95Hz.81.86
    96Hz.80.89
    97Hz.79.92
    98Hz.78.94
    99Hz.76.97
    100Hz.74.50
    I seem to have a very broad hump from about 41 to 80 hz and another spike down low. Phase experiments may cure part of it. Otherwise a BFD will take care of everything.
    I am very satisfied overall. I don't think I could have purchased a completed sub for anywhere near my investment on this. [​IMG]
     
  2. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Those look like really good numbers there, Kerry, and easily within the capabilities of the BFD to flatten quite nicely, methinks (oh, the temptation... I don't have one right now, and I just know it would do a world of good for my system. Haven't done an in-room listening position response, but I can tell just by eyeballing the SPL meter during sweeps that there are some humps and dips... Grrr!). Looks like you get some prodigious output even into the teens. Nice!
     
  3. jeff lam

    jeff lam Screenwriter

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    That response looks very good to me. Seems to be very flat. And all this is without an eq? I wish my room was that nice to my sub. Congratulations on an exceptional peice of equipment!
     
  4. Patrick Sun

    Patrick Sun Studio Mogul

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    Looks pretty good. Time to graph it, frame it, and stick on the wall near the sub. [​IMG]
     
  5. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Jeff, I think that being relatively "flat" is part of the double edged sword of big rooms. Big rooms "tend" to be smoother but it takes a lot of output to fill them. At one time I was considering going with horns for that reason. I have a full set of plans for a LaScala copy. Building a midrange horn lens from scratch isn't for the faint of heart. I still may try it someday. I'll have to build a different sub to keep up with 104db/watt mains however.
    That could be a fun problem to have. [​IMG]
     
  6. jeff lam

    jeff lam Screenwriter

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    I figured the room size had to play a huge roll in this. I guess that makes sense too. The larger the room, the flatter the response, but also takes a lot more bass to fill.
     
  7. charles_w

    charles_w Stunt Coordinator

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    Kerry,

    Perhaps this should be in another thread, I just finished my

    Sonosub using the Shiva, and would like to take some measurements as well.I have the RS meter.

    What do you use for frequency tones Avia?

    Thanks

    Lee
     
  8. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Charles - I have downloaded a trial version frequency generator program from PAS-USA.
    www.audio-software.com
    It is a very cool system that lets you output a sine wave from 1 - 20Khz. I hooked up my laptop to the AUX inputs on my receiver and let my daughter run the program while I measured. I highly recommend it if you want to do port tuning or measure response. I like it because you can vary the frequency without starting and stopping the tone, so there are no nasty pops or cracks as in another tool I have. The only downside of this particular generator is it does not output pink-noise. I have another shareware that does.
     
  9. Jack Gilvey

    Jack Gilvey Producer

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    Very impressive response, Kerry, nice job.
     
  10. charles_w

    charles_w Stunt Coordinator

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    Kerry,

    Thanks for the link, Did you set the spl at 75db at the listening position and then take both readings at the same volume?

    Thanks,

    Lee
     
  11. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Kerry,

    That is so close to flat you might consider not bothering with the BFD. Doupt it would make much difference, esp with HT.
     
  12. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Charles - I took the 1m readings first. When I moved to the listening position,I nudged the level up just enough to center the scale at 75db. In all it was a very small change. My amps output meters showed less than 2 watts. They are flourescent segments so it is not as easy to guess the in between levels. As for the BFD, I have to admit I am liking the sound pretty well as is. I have been listening to a lot of different kinds of music and haven't been able to identify what I thought was any exagerations. I think the levels have to vary a lot in the bass range because human ears just aren't that sensitive in the lower octaves. I thinks that explains too why a lot of people prefer their subs a little "hot".
     

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