Step By Step Sub Equalization using BFD and ETF

Discussion in 'Archived Threads 2001-2004' started by Jon M, Jan 9, 2002.

  1. Jon M

    Jon M Agent

    Joined:
    Apr 30, 2000
    Messages:
    27
    Likes Received:
    0
    Trophy Points:
    0
  2. James Mudler

    James Mudler Stunt Coordinator

    Joined:
    Feb 1, 2001
    Messages:
    207
    Likes Received:
    0
    Trophy Points:
    0
    Jon,

    Very nice layout. I'm at work so I did not have time to read it completly, but will. Nice job!
     
  3. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Great job!

    Here are a couple comments that might or might not help:

    1) RS meter microphone on tripod. For me, since the RS microphone is omnidirectional, I would place it at a position on my listening couch or chair exactly at the height where my ears would be when I'm sitting down and at a 45 degree up-slope angle facing straight to the front. I think this gives the best approximation of what both your ears are hearing. You can even move the tripod to different seating positions on your couch to see what other persons might hear and then average the results if you want.

    2) Mention you need a full-duplex soundcard to setup as you have graphically indicated. If the soundcard is not full-duplex (many notebooks) then you can use the test signal CD and menu setting for CD.

    3) The RS SPL meter correction file (text file format as shown is important) only works with purchased versions of ETF and the values are:

    frequency . . . SPL adjustment value . . . phase adjustment value

    4) When entering the filter settings on the BFD, start with the lowest frequency peak first, as it may also effect/change response peaks on subsequent higher frequencies.

    BruceD
     
  4. Mike Dr

    Mike Dr Stunt Coordinator

    Joined:
    Jul 30, 2000
    Messages:
    171
    Likes Received:
    0
    Trophy Points:
    0
    wow excellent start. Wish this was out when i was adjusting my sub [​IMG]
    Personally, i couldn't get the BFD software to talk to the BFD .. I have midi cables hooked up that I use once in a while to upload MIDI files to a Korg 01/W fd but it didnt seem to work with bfd.. oh well. Keep up the excellent work. I suppose if you know of some sort of free software like ETF those links would be good to include as well as links to spectraplus and the others.
     
  5. Ken Woodrow

    Ken Woodrow Stunt Coordinator

    Joined:
    Feb 12, 2001
    Messages:
    113
    Likes Received:
    0
    Trophy Points:
    0
    That is a fantastic start! Very timely too. A couple of thoughts:

    (1) Explain what graph you are looking at in ETF -- logarithmic, 200 ms gate time, low frequency response, 20 hz to 200 hz, for example. Because there are so many different ways to look at a measured response in ETF, it would be helpful to know which ones are the easiest and most intuitive to use for EQ'ing a sub.

    (2) Explain the relationship b/n the frequency spectrum and musical octaves. For those who don't come for a musician background, it might be helpful to understand how the measured frequencies correspond to notes on a scale.

    (3) Address how to integrate the sub and main speakers and how to set a crossover point and slope (assuming that its adjustable!). This is the subject of a nearby thread that I started. BruceD has been extremely helpful in fleshing this out.

    (4) It might be worthwhile to recommend running a second measurement after correction with the BFD but with both the main speakers and sub running (this will work if you use the CD inputs of your pre-amp and your pre-amp executes bass management). This might reveal additional peaks that are the result of the crossover and main/sub interaction that can be cured by either adjusting the crossover point or making further adjustments with the BFD.

    (5) Explain how the reference SPL level is determined.

    I've intended to write up a similar FAQ, but you beat me to it. Do you have any objection to me including a link to your writeup on my personal website? (See my sig).

    Thanks again for doing this.

    Regards,

    Ken
     
  6. Jon M

    Jon M Agent

    Joined:
    Apr 30, 2000
    Messages:
    27
    Likes Received:
    0
    Trophy Points:
    0
    Hopefully I will get all these additions added tonight. Does anyone know how to correlate bandwidth in ocatves to frequency in hertz? It would be helpful if I could explain this but I really don't know how they relate.

    Jon
     
  7. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Jon,
    In it's simplest terms, an octave is a doubling of frequency.
    For example, this is an approximation of an octave progression of frequencies, but is not exactly dead-on:
    20Hz -> 40Hz -> 80Hz -> 160Hz -> 320 Hz etc.
    Another reference:
    As you can see at the bottom of the page (in the link I provide below), for musical instruments like the piano shown they start at 27.5 Hz and one octave higher is at 55 Hz.
    frequency scale
    The interesting point about most magazine reviews is that they show frequency response in 1/3 octave logrithamic graphs.
    ETF does give you the opportunity to look at a finer scale, like 1/6 octave or even 1/12 octave (you can hear differences finer than 1/3 octave).
    This is why they recommend you never use a graphic equalizer with less than 1/3 octave steps (12 sliders per channel I think). I've never used one.
    BruceD
     
  8. Mike Dr

    Mike Dr Stunt Coordinator

    Joined:
    Jul 30, 2000
    Messages:
    171
    Likes Received:
    0
    Trophy Points:
    0
  9. Shawn Fogg

    Shawn Fogg Stunt Coordinator

    Joined:
    Oct 5, 2001
    Messages:
    223
    Likes Received:
    0
    Trophy Points:
    0
    Jon,

    Great article. I just got an 1124 yesterday so it will certainly help me get up to speed with it faster.

    A couple of additions you might want to consider to the article.

    When you talk about the R/S correction file I believe you aren't really correcting for a irregularity in the SPL meter itself but are correcting for the 'C' weighting that the meter applies to the signal. This is certainly the case when measuring with a test CD and the SPL meter alone. There are mods online that will make the R/S SPL meter meter flat response with no weighting.

    The second thing is you might want to talk about taking measurments from multiple locatings and building your filters around that. Say from three positions on your couch. Working from just a single spot can often make things worse at other seats.

    Using ETF you can create an overlay of your multiple response curves. From those you can see what peaks are common at all listening positions and build your filters around them. Takes much more time to do it this way but the end results will be more uniform over a greater area.

    Also, might want to consider a warning about trying to fix room nulls with bass boosts. You usually can't do all that much with them with an EQ but you eat up power and output of the sub with little gain. Sub/listening position adjustments are the way to go to beat nulls. Of course if you move either you need to start over on the EQ so it is by far better to work with positioning before EQ.

    Shawn
     
  10. Greg Lee

    Greg Lee Agent

    Joined:
    Dec 12, 2001
    Messages:
    30
    Likes Received:
    0
    Trophy Points:
    0
    The corrections suggested above are worthwhile, but I really have to say BRAVO to your initial effort. I just got my BFD last night, after having found your article in the afternoon, and it was IMMENSELY (sorry for all the caps but . . . ) helpful.

    Thanks very much for taking the time and effort to do this!

    Greg
     
  11. Sonnie Parker

    Sonnie Parker Second Unit

    Joined:
    Dec 11, 2001
    Messages:
    407
    Likes Received:
    0
    Trophy Points:
    0
    The ETF software actually looks like it's easier to use vs. Spectra Plus.

    Thanks for the time and effort in doing this....my BFD is on it's way. The site will really help. I read the entire manual and there's no way I can understand it as well as what you've written.

    Again, thanks!

    SP
     
  12. Rick Radford

    Rick Radford Supporting Actor

    Joined:
    May 12, 2001
    Messages:
    642
    Likes Received:
    0
    Trophy Points:
    0
    Fellers, please allow me to poke my newbie head in here for just a moment.

    Right now I just have the demo ETF5 software, and I just want to set it up and see what I have right now.. with no eq in the loop. (which I don't have yet anyhoo).

    My PC is in my office about 35 feet away from the HT room. I don't plan to move the PC for measurements. What I'd like to do is run a 50 ft RCA-RCA speaker cord to my RS SPL meter and connect to my SB Live card with a 1/8 adapter. Then I'd like to run a calibration disc like Stryke, etc. and record the results.. or at least, view them since I can't save or print them with the demo version.

    But the ETF5 s/w seems geared to using the internal tone generator which means I'd have to run a couple of 50 ft runs from the PC out to my receiver. Is there any reason why I can't just use a calibration CD and my RS meter as the mic? (ala the half-duplex method)? Or is there some reason to use the ETF tones?

    BTW, I d/l the CD test files from ETF, but it's just undefined noise on one file .. and nothing audible on the other. ?? (about 125 megs each)

    Also the setup has the sound card lineout feeding the linein of the sound card for test purposes.. and says the test is necessary. ?

    Naturally, I don't have all the hw needed to setup the test.. so I have to ask, is it really necessary?

    As you can see, I'm just stumbling my way through right now. Your site has been a big help in understanding some of this, Jon. You appear to have just used the internal tone generator from ETF for your tests, right?

    since I don't wanna do that, I wonder if I'm just trying to swim upstream on this software.
     
  13. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Rick,
    It appears from this blurb about CD use on the etf website that the CD and the RS mic may be all you need.
    CD use
    I know when I've used the program in full-duplex mode, the mls test signals produced by the software sound just like pink noise to me.
    Which means the noise you hear on the CD is probably the test signal.
    Cable for your RS mic will probably need to be some good RG-6 shielded coax with the F-connector to RCA adapters on each end, speaker cable will not work for sure. Even then I'm not sure it will work at a 50' length.
    BruceD
     
  14. Rick Radford

    Rick Radford Supporting Actor

    Joined:
    May 12, 2001
    Messages:
    642
    Likes Received:
    0
    Trophy Points:
    0
     
  15. Rick Radford

    Rick Radford Supporting Actor

    Joined:
    May 12, 2001
    Messages:
    642
    Likes Received:
    0
    Trophy Points:
    0
    Here's an update that may be of interest to others interested in learning how to use the ETF software. I emailed ETF this morning and received a quick response as follows:
    ********** 1st msg ******************
    ----- Original Message -----
    From: "Rick Radford"
    To:
    Sent: Friday, January 11, 2002 6:52 AM
    Subject: mic cable length?
    > Doug,
    >
    > I got a demo copy of ETF yesterday and would like to try
    >to use it by running a 50 ft cable from my RS SPL meter to
    >my PC in my home office.
    This may work well, but also may not due to excessive 60 Hz Hum from power sources. Your RS meter will provide accurate LF response measurements.
    > My plan is to use a calibration CD like the Stryke CD (or
    > homebrew) and use the CD/half-duplex mode.
    You must use the ETF test signal CD with the ETF program. It is much better for this type of measurement than any test CD, in addition to this, a standard test CD will not work.
    The best option is to use full duplex capability of your sound card and run cables from and to your computer in your office. THIS IS WHAT YOU SHOULD DO- especially for low frequency testing because ETF is very powerful for LF
    testing using (record+play) full duplex sound cards.
    > Is the 50ft mic cable too long? (It's just speaker wire
    >with an RCA male connector on each end to plug into my 1/8
    >adapter for my SBLive value sound card).
    I would use RCA phono type cable, you will probably get too much noise using an unshielded cable.
    I would first test for noise by buying a 2 * 20 ' or whatever length you need of the RCA phono cable and run your computer into your audio system to listen to computer sounds through your audio system and see if AC hum is
    excessive - if you can just hear it, but it isn't really loud than it will not really affect results. Maybe try it first using your simple wiring approach (although I'm quite sure this will not work - no one has tried this that I know of), then try it with phono cables.
    > Will this setup work to help me map my inroom sub response?
    Absolutely !
    You may only have the option of bringing your computer into the living room to take noise free measurements.
    Once you buy the program you can take a measurement and send it here, I can tell you if noise if affecting results.
    ********** end 1st msg ********************
    *********** 2nd msg **********
    > Are the differences between the demo and the purchased copy
    > the ability to save and print files?
    *Right.
    How about using mic
    > correction files? Other?
    *You can use mic correction in the demo. You cannot take more than two
    measurements without rebooting the software in the demo.
    >
    > It's gonna take me a little while to sort through all this
    > and decide how I'm gonna work it.
    *I would suggest just moving the PC into the livingroom and taking
    measurements after you do the loop thru test in the demo. FIRST DO THE TEST
    RECOMMENDED. It appears whenever you run an unlicensed version of the
    software.
    *********** end 2nd msg *******************
    This is almost SVS type customer service. [​IMG]
    Being pretty cable illiterate, I don't even know what RCA phono cable is. But it looks like I need to take back my 50' speaker wire and mono 1/8 adapter and get two stereo 1/8 adapters.
    Is the RCA phono cable easily found at Lowes/HD/Ratshack? I've never terminated them either, so if they need special tools for that, I'm outta luck.
    Can you guys advise me specifically what I need to get to set this up?
    Long RG6 for the mic with RCA ends to the 1/8 y adapter line in?
    Short RCA phono cable for the 1/8 y adapter lineout to y adapter linein?
    Long RCA phono cable for the 1/8 y adapter lineout to the receiver?
    What input on the receiver should this connect to?
    Thanks a bunch. (I may rescind my resolve to just do this manually). [​IMG]
    OTOH, looking at all I'd have to do to move the PC into the HT room gives me pause for thought. I'm beginning to question if the effort involved is worth the benefit. :/
    Just call me lazy. Perhaps I'm not the HT enthusiast I thought I was. [​IMG]
    Still ponderin' my options.
     
  16. Ken Woodrow

    Ken Woodrow Stunt Coordinator

    Joined:
    Feb 12, 2001
    Messages:
    113
    Likes Received:
    0
    Trophy Points:
    0
    Rick:

    I really think that it is worth it to lug the computer into the HT room. Taking measurements with ETF is ridiculously easy once you get the computer and system configured. It's also easy to take multiple measurements to see immediately the effect of speaker repositioning, crossover adjustments, and equalizer changes. If you leave the PC where it is and use a long cable, you'll have to run back and forth to make changes and execute measurements, AND you'll have to buy two long RCA cables for full duplex measurement(Rat Shack carries long cables with RCA jacks on both ends, but they're not well-shielded and may be prone to picking up RF interference as warned by the ETF folks).

    Setting up the PC to take measurements is not really that hard. If you have a standard consumer-type soundcard with 1/8" mini-jacks, you can go to Rat Shack and pick up two 1/8" to 2 1/4" stereo RCA adaptor cables (the ETF documentation gives you the exact part numbers and a pic). Given the short distances involved (if you move the PC), cheap adaptor cables should do fine.

    I say register the software and go for it. It will be a good investment, b/c you'll be able to measure and optimize your system as it evolves. Better yet, you can even do measurements at your friends' houses and improve their systems. They'll think you're a genius.

    - Ken
     
  17. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Rick,
    This is probably the third time I've mentioned this to you but the following is probably the best shielded "cheap" connection you can get quickly (all at radio shack or home depot) :
    1) RG-6 shield coax cable (like they use for cable or satellite) but just make sure it's not RG-59
    2) Typically this cable comes with what they call male F-connectors on both ends (this is what cable boxes and TVs use for the composite connection).
    3) 2 adapters called F-connector to RCA. These have a female F-connector and male RCA plug.
    4) If your sound card has a stereo female 1/8" mini-phono plug, radio shack also caries an adapter with 2 female RCA connectors and the male 1/8" mini phone plug.
    Try it and report results.
    BruceD
     
  18. Bill Catherall

    Bill Catherall Screenwriter

    Joined:
    Aug 1, 1997
    Messages:
    1,560
    Likes Received:
    0
    Trophy Points:
    0
    I looked and looked and looked but couldn't find the BFD at the link you provided.
    Also, I know your instructions are specifically for the BFD, but could you also provide links to other EQ's that would be good, sans instruction?
    I second the vote to provide links to other software (preferably freeware, or cheap shareware...$150? [​IMG] ) besides ETF.
    Other than that... [​IMG] Great work!
     
  19. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Bill,
    Here is the link, and by the way, the BFD 1100P has already been replaced (on dealers shelves) by the BFD 1124P.
    Same look, same features (I think just an upgradded DAC chipset).
    BFD Parametric EQ
    Many Parametric EQs may not provide the level of control available with the BFD;
    1) 12 Parametric EQ filters per channel (stereo)
    2) frequency selection down to 1/60th of an octave
    3) bandwidth of filter (frequency width) down to 1/60th of an octave
    I searched everywhere and can't find any software that even comes close to ETF.
    BruceD
     
  20. Bill Catherall

    Bill Catherall Screenwriter

    Joined:
    Aug 1, 1997
    Messages:
    1,560
    Likes Received:
    0
    Trophy Points:
    0
    Bruce - Thanks for the link, but that still doesn't tell me where to buy it and how much it costs.
     

Share This Page