Subwoofer Test

Discussion in 'Subwoofers' started by Ian J, Jun 14, 2003.

  1. Ian J

    Ian J
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    I have been playing about trying to setup my SVS 20-39 PC Plus and have come up with the following graph.

    It looks to me like my next upgrade will be a BFD as the position of the sub is fixed due to it's size.

    I hope that you've got good eyesight as this is the maximum size that the software will allow
     

    Attached Files:

  2. nathan_silly

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    Ian have you got a CD with test tones I can use to plot a graph? I've got DSL connection so I can download a CD ISO.

    Cheers
     
  3. Ian J

    Ian J
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    The test tones can be downloaded from here

    Also available from the snapbug site is the draft spreadsheet which includes compensation for inaccuracies in the SPL meter
     
  4. tan1415

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    What does the graph mean?
    I don't understand it...is it good or bad?
     
  5. nathan_silly

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    My CD player doesn't playback MP3's. Are there any CD's with various frequency tones?

    I can't understand why the BFD doesn't come with a CD, or with built-in tones. I would be interested in the BFD it came with a CD, or a microphone auto EQ thingy like the DD-18 Sub or the Pioneer 2011 MACC.
     
  6. nathan_silly

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    Tan, what Ian or anybody using a BFD is a flat response on the subwoofer- a perfect subwoofer/room diagram will be have a straight line at 75dB (or 85dB, whatever volume is used) from 20hz to 80hz, with no peaks or troughs. From Ians graph I (can't quite make out the numbers) is two peaks at 22hz and 40hz.
     
  7. tk2001

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    Ian J,

    Do you have your sub positioned in a corner of your room? I know SVS advises corner placement if possible for their subs.

    Are you playing those sine-waves at reference levels and jotting down the numbers?

    If you could iron-out the peaks at 22hz, 40hz, and 63hz then you'll be left with a very nice house-curve with very strong output from 16hz all the way up to 160hz, which only very good subs are capable of doing.
     
  8. Ian J

    Ian J
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    Sub is a foot out from the corner of the room and due to the size I am fairly limited as to where it can go anyway.

    I played the tones at reference level, wrote down the results and entered them into the Excel chart available from the snapbug site and that automatically compensates for the spl meter inaccuracies.

    I did the same thing with my old Storm but I am annoyed as I can't find it now :(
     
  9. Phil Hinton

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    Ian,

    That still looks like a very good response, a bfd will certainly be of great use and going by your graph it doesn't look like you should have too many difficulties taming the three peaks i see.
     
  10. bob1

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    Can't you just put the tones onto a cdr,just make as an audio cd.
     
  11. Tom Vodhanel

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    Hi guys,

    Be CAREFUL with test tones of any sort. A sweep done at moderate levels is OK...but you'll need a RTA to plot that. (you can DL free RTA software now though if you have a PC near the HT system) Sine waves can fry a driver in a matter of seconds...so please, use very low output levels and try to get your measurement in a couple of seconds. (don't play the tone for 5 minutes while you are on the phone in the next room for example) and rest the subwoofer for 10-15 seconds inbetween each frequency you check.

    Tom V.
    SVS
     
  12. tan1415

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    Oops.....
     
  13. Steve.EX

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    Ian
    I would agree with Phil, that, is NOT (by a long chalk) the worst native response curve i have seen, a BFD will certainly tidy it up but it's not going to overheat from workload.

    Steve.
     
  14. Tom Vodhanel

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    Hi guys,

    When you look at the graph, look for the maximum differences. In this case, I think it is 8dBs (forgetting about the big null in the 70-90hz range for a second). So that would be listed as +/- 4dBs...for in room response, that is actually VERY good. Adding an EQ to tame the two peaks would make it closer to +/-1 or +/-2dBs I think...even better. The 70-90hz null might be caused by some destructive interaction between the mains and the subwoofer. Try adjusting the phase control to see if you can tame that.

    if anyone wants to DL a kick-ass RTA, goto

    www.soundtechnology.com

    and DL the v4.32 software.

    It will work for 30 days on your PC, after that you need to buy the *key* to keep using it...I think I paid something like $3500...so be sure to take all the measurements you want within 30 days..:) 1/96th octave resolution, and ALL KINDs of capabilities....RT60, RTA, 3-D waterfall, ect. With this and a simple RS SPL meter, you can find out a LOT about your speakers/listening environment over a few weekends!

    Tom V.
    SVS
     
  15. nathan_silly

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    I've downloaded SpectraPlus, I'm currently creating some Wav test tones.

    What type do I use? (pink, white etc) and shall I start from 10hz and do 20,30,40,50,60,70,80,90,100?

    What else shall I put onto a CD-R?

    [edit]

    I'm totally confused. Why aren't there CD's available with the tones you need for setting up a BFD & subwoofer available?

    I can use my PC from the optical output. What do I do to create the .Wav files I need?

    Thanks
     
  16. avanzato

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    I bought 'My Disc' a test CD from sheffield lab many years ago and it has helped me set up several systems.

    A long time ago I used it and a 31 band equaliser to do a rather crude EQ on a sub.

    You could try amazon for test CD's or your local Car audio shop.
     
  17. Tom Vodhanel

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    www.autosound2000.com

    test CD #101. $15

    It has sine wave from 10hz to 98hz (tracks 10 thru 98).

    Tom V.
    SVS
     
  18. petrolhead

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    Nathan

    Apocalypse did a site re the BFD. On it was agreat link for the tones. All you did was download them (MP3) but then cut them to Music CD using Nero which converted them to CD format.

    I have found the origional post but the link no longer works so I have PMd him
     
  19. Steve Bate

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    Sineways download page here and this is the comprehensive setup guide originally in Apocalypses thread

    Hope this helps

    Steve
     
  20. JSW

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    Hi Ian,

    you can post a larger image is just how you reduce it that matters.

    If you reduced its size in a paint program so you could then save it with a low Kb count to be able to attach it then you get a small pic.

    The other way is to leave the size of the pic and reduce its dpi.

    Or upload your image to an image hosting site.

    Either way have fun with your new sub.
     
  21. NicolasB

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    Really? How? I can see how a square wave would toast it, but a sine wave?
     
  22. bob1

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    Yeah that is strange considering the tones last 10seconds and nobody as killed a sub yet.Well and not told us.If you want to see what response i got from the velo vx10 look here
     
  23. jag77

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    Sine waves can indeed kill the sub's VC. After a few minutes of playing sine tones at 80dB, the center of the SVS's metal cone feels warm to the touch. I can't imagine how hot it will be at the VC itself if I was playing them at 90dB longer than a few minutes.

    I read that when hot, the VC can vapourise its enamel, warp and permanent damage. Apparently, its not the case with normal sounds.
     
  24. tk2001

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  25. martintyler

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    what software are you guys using to take these measurements?
     
  26. Ian J

    Ian J
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  27. martintyler

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    I actually meant the software to record it and produce the graph... or did you just do that by hand, measuring each level and entering the spl into a spreadsheet?
     
  28. Ian J

    Ian J
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    Yes - measured by hand and entered into a spreadsheet that is available from the same website and automatically corrects for inaccuracies in the spl meter at low frequencies
     
  29. nathan_silly

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    Ian have you fiddled with the variable phase, sub-sonic filter adjustments yet?

    So how much better is the 20-39 PC Plus compared to the Storm? For example, my Yamaha YST-SW40 is utter rubbish compared to the Storm. Is it the same again, Storm is rubbish to the SVS? Or is it slightly better?

    How many dB is it louder, does it chuff with Toy Story 2 intro logo, how much deeper etc?..

    Downloaded the tones, I'll be doing a graph today.

    [edit]

    Do I enter my results into the RAW values and leave COMP alone?

    Shall I use C weighting? fast or slow response?
     
  30. Ian J

    Ian J
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    So many questions :D

    I haven't fiddled with the phase or filters yet but will have a go today. Sorry to be so slow but I watched Durham v Notts yesterday in between sunbathing and barbecuing instead.

    For movie use the 20-39 is in a different league to the Storm as it is much more powerful, deeper and produces cleaner bass. I don't play much music so am the wrong person to ask about that but the one or two tracks that I played sounded good. The Storm will be more versatile to connect up as all RELs can use the high and low levels connected together.

    You enter the values in the first column of the spreadsheet.

    I am hoping that Orbital, who lives locally and owns a Paradigm Servo will come round for a listen shortly and will report back to you all and Deckard who doesn't live that far away and owns a Velodyne CHT15 is also more than welcome to come round.
     

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