EQ setup and RTA vs manual method

Discussion in 'Archived Threads 2001-2004' started by Rick Radford, Jan 6, 2002.

  1. Rick Radford

    Rick Radford Supporting Actor

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    Looking ahead to getting the BFD1124p and using it with my RS SPL meter and SVS 20-39CS, I have a few questions.

    1) Should the receiver be in any particular mode? Stereo? Mains set to small or large? (normal is small) Does it matter here if the test CD is Autosounds, Stryke, or homebrew?

    2) As I anticipate limited use of an RTA, I'd guess that the rampup time to figure out how to use an RTA like Spectra+ will likely exceed how long it would take to just manually note the readings (10-100 Hz individually) and create an Excel spreadsheet. True?

    Plus, the next time I'd need to use it would be when the room is rearranged.. and I'd be outside the 30 trial period to boot.

    3) What does Spectra+ cost anyway?

    Also, to use an RTA, I'd have to get ~35 feet of cable and connectors to hook my SPL meter to the PC.

    4)Are there line losses with that length of cable to consider?

    All-in-all, it seems to me that a one-time use of an RTA would not be worth the effort (compared to the manual method). But, since I've never used an RTA, I may well be missing an important consideration. Whatcha think?

    (however, the geek factor in me says to use the RTA regardless of how long it takes to figure it out!)
     
  2. Wayne A. Pflughaupt

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    Rick,



    I can help with some of this.

    1. Since you’re using a test CD, I would use stereo mode. Leave the mains as you usually have them set. I prefer to leave them off until I’ve finished tweaking the equalizer settings for the sub. Afterwards you can turn the mains on and blend them with the sub, using the sub’s gain control in conjunction with the RTA or test disc. A little EQ tweaking of the sub around the crossover frequency might (but hopefully won’t) be needed as well.



      Any test disc with at least 1/6 octave resolution is acceptable. With pink noise I found I was able to get more accurate results by measuring filtered tones than I was by using the RTA and a broad-band signal. Pink noise is a bit random by nature, which can make precise sub adjustment a challenge. It’s doable if it’s filtered pink noise, but you’d be smart to pass on making adjustments using broad-band pink noise.
    2. I’ve never used spectrum analysis software (I have a stand-alone RTA), but I suspect you could be right. But for sure, the “coolness” factor is definitely there with a real-time analyzer! [​IMG] However, before you buy you might want to find out what the software’s resolution is. I don’t know about software-based systems, but stand-alone RTAs have only 1/3 octave resolution. If this is the case, you will definitely get better and more accurate results with a test disc and SPL meter.



      While the Spectra+ program might seem excessive for a single-set up, I’ll bet you’ll be surprised to find how much use you can get out of it. Do you have any friends? Do you plan to live where you are the rest of your life? Do you plan to have this sub the rest of your life? Do you think you’ll ever do a bedroom set up? Do you now have or might someday have a nice car stereo system? Ad infinitum.


    I’ll have to leave 3 & 4 to the computer nerds. I’m only an audio nerd. [​IMG]



    Good Luck,

    Wayne A. Pflughaupt
     
  3. BruceD

    BruceD Screenwriter

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    Rick,
    I've never used Spectra+, so I can't specifically say much about it's leaning curve or usefulness.
    I bought the ETF5 software program instead (it was cheaper) because of the extensive tutorial info on their website. It really helped me get a better handle on room acoustics quickly.
    I think the best way to understand how moving speakers, moving listening positions, or changing room acoustics affects what you hear is to see what changes on the various graphs and then correlate that to what you actually hear.
    Allowed me to zero in on a much better sounding environment quickly without a lot of random experimentation.
    I had originally started with an SPL meter and excel graphs, but it just took too long.
    Another benefit of ETF5 is that you don't need a test disk because it generates it's own test signal. You just need the RS SPL meter with it's RCA output port attached to your PC's LINE-IN port and a few other cables.
    ETF website
    BruceD
     
  4. Wayne A. Pflughaupt

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    Bruce, since you have it, what is the resolution of the ETF package, and what did it cost?

    Thanks,

    Wayne A. Pflughaupt
     
  5. Kevin C Brown

    Kevin C Brown Producer

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    I have *only* used the manual method, and it kind of sucks. :)

    I use the Autosounds 2000 disc for 20 to 98 Hz, and then Stryke for the remainder up to 160 Hz.

    To measure a "pass", (20 to 160 Hz complete), takes about 15 minutes. Might not seem like a lot, but when you think of all the things you can change, and that you could remeasure after, you can see how it compounds:

    1) phase adjustment

    2) physical placement (sub and/or mains)

    3) crossover freq

    4) setting filters in the BFD

    5) sub only, mains only, sub plus mains

    etc.
     
  6. BruceD

    BruceD Screenwriter

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    Wayne,

    Cost was $150.

    Accuracy:

    When displaying the logarithmic frequency graph, you are able to select among the following scales: 1/2, 1/3, 1/4, 1/6, 1/8, 1/10 and 1/12 octave frequency resolution.

    BruceD
     
  7. Wayne A. Pflughaupt

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    Very impressive. I paid $500 for my RTA!
     
  8. Rick Radford

    Rick Radford Supporting Actor

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    Wayne, thanks for jumping in. I appreciate your input. Those are good bonus questions to consider.

    BruceD, thanks for the link to ETF. Bookmarked! Unfortunately, even the $150 cost of this s/w will more than double my EQ investment.. and I can't do that right now. So either the free 30 day demo of Spectra+ or manual charting will have to be my choice for right now.

    Kevin, thanks for your thoughts about the manual method. I created my own test CD using the NCHtone generator. Unfortunately, each of the test signals I generated have a "pop" and I don't have any editing s/w to fix it. (that I know of)

    For test CDs:

    Autosounds has 1 Hz increments from 20 to 98Hz.

    Stryke has fractional octaves from 20 to 160 Hz.

    BASS MEKANIK v5.0 CD from Partsexpress. runs from 20-99 Hz. Unknown increments.

    I'd like to see a test CD that runs from 10-150 Hz or so. Although I can easily create one, I can't get rid of the pops.

    I still don't know about line losses for a 35 ft mic cable to the pc. Nor do I know the price of Spectra+ either.

    ... still mulling my options.
     
  9. BruceD

    BruceD Screenwriter

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    Rick,

    You can download the ETF software for free (no 30 day limit)and use it with your RS SPL meter's RCA mono output port, you just can't save the graphs to disk or print them out.

    When I looked a year or two ago, I think Spectra+ was $295.

    BruceD
     
  10. Rick Radford

    Rick Radford Supporting Actor

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  11. Kevin C Brown

    Kevin C Brown Producer

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    Rick- The Stryke disc goes from 20 Hz to 20 kHz, just that I only used up to 160 Hz. [​IMG]
    Yeah, I think that I have read that you have to make sure those test tones "cross at zero" or something to get rid of the clicks between tracks. Another thread floating around might address that.
     

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