Page 3 of 3 FirstFirst 123
Results 31 to 35 of 35

Thread: S3900 S4700 dbx DriveRack 260

  1. #31
    Senior Señor boputnam's Avatar
    Join Date
    Apr 2003
    Location
    northern california
    Posts
    7,007
    Quote Originally Posted by 4313B View Post
    I then applied the necessary crossover slopes and frequencies to get the acoustic measurement to match the electrical target as closely as possible. It doesn’t matter what electronic slope and frequency is used so long as the actual acoustic response is close.
    There is is in a nutshell, sports fans. Genius in it's simplicity and correctness...
    bo

    "Indeed, not!!"

  2. #32
    Senior Member
    Join Date
    Nov 2008
    Location
    Gothenburg, Sweden
    Posts
    759
    Quote Originally Posted by 4313B View Post
    "I haven’t gotten back into working with the DBX or with any other speaker models. I am using an AllDSP model PLP226 Signature. It is basically 2 in and 6 out which works for my Tri-amp system I am not using the UHF at all. I actually did my design with my speakers in place in my living room. I put in a 4 th order LR crossover target (750 Theoretical) and made 4 mic measurements of each of my woofers and HF units. Averaged the 4 positions for each transducer and used those 6 curves as the transducer measurements. I then applied the necessary crossover slopes and frequencies to get the acoustic measurement to match the electrical target as closely as possible. It doesn’t matter what electronic slope and frequency is used so long as the actual acoustic response is close.

    Next I applied the necessary EQ to get the crossover slopes tuned in. Once done, I turned everything back on and made a Left (or Right) channel measurement using the same 4 mic positions averaged. The summing came out nearly perfect, as it should. I did the time delay by choosing one of the mic positions that gave the smoothest curve through crossover and inverting the polarity on the HF. I adjusted the delay for the deepest and most symmetrical notch at crossover. Flip the phase and all goes flat again. Finally, I applied some global EQ to the entire system to clean up any remaining room of summing issues. It is very simple to do, but it takes forever due to the multiple measurements and repetitive nature of things. My results were awesome.

    The DBX Driveline 260 can do the job nicely although it is a little limited in PEQ filters. You have to be pretty efficient. I am currently looking at other High End solutions which incorporate built-in Preamp functions so I can ditch my analog preamp. Among the contenders are the Ground Sound DCN28 and the DEQX HDP-4. All are pretty pricey. The DBX is cheap at about $1000."
    Anyone having a guess which kind of mic-positions Greg used here?
    I would like to try this procedure.
    Mic close to speaker, or at listening positions?
    Mic at ear levels, or ground-plane?
    EXACT same mic-positions all the iterations?

  3. #33
    Senior Member NWCgrad's Avatar
    Join Date
    May 2015
    Location
    Frederick, MD
    Posts
    107
    That would be great information. I will be fine tuning a large DIY three-way speaker in next couple of weeks. I was planning on hauling them outdoors for the initial measurements, but they will be very heavy and if in room is good enough for an engineer the caliber of GT it is more than good enough for a geneticist like myself.

    Does anyone know of any useful references for setting up digital XO's and EQ? The D'Appolito text on measuring loudspeakers is about all I can find. I know Self has a giant book on digital crossover design, but I believe it is for the development of the device and not its implementation.

  4. #34
    Senior Señor boputnam's Avatar
    Join Date
    Apr 2003
    Location
    northern california
    Posts
    7,007
    Quote Originally Posted by bubbleboy76 View Post
    1) Anyone having a guess which kind of mic-positions Greg used here?
    I would like to try this procedure.
    2) Mic close to speaker, or at listening positions?
    3) Mic at ear levels, or ground-plane?
    4) EXACT same mic-positions all the iterations?
    1) Use a quality measurement mic which comes with a response curve measure for it. Earthworks M30 is suitable.
    2) I prefer measuring where the listening will be done. In the field, we move the mic(s) around to different locations and average. In the home, I fix one position - the sweet spot - and pin it down. The adjacent positions won't be so different (unless you have really beamy horns).
    3) Ibid
    4) Ibid.

    Quote Originally Posted by NWCgrad View Post
    That would be great information. I will be fine tuning a large DIY three-way speaker in next couple of weeks. I was planning on hauling them outdoors for the initial measurements, but they will be very heavy and if in room is good enough for an engineer the caliber of GT it is more than good enough for a geneticist like myself.

    Does anyone know of any useful references for setting up digital XO's and EQ? The D'Appolito text on measuring loudspeakers is about all I can find. I know Self has a giant book on digital crossover design, but I believe it is for the development of the device and not its implementation.
    For a three-way that is tri-amped, you must do each band pass separately. DO ONLY ONE SIDE OF THE SYSTEM; copy to the other side. However, first, establish your delay(s). The LF will have the most retarded acoustic arrival time due to the LPF. Measure it's impulse and delay the other band passes to match. Then, tune each band pass separately, striving for flat reproduction of Pink noise. Then, open all band passes and measure the overall reproduction of Pink. Look at the response at the crossover points - if you see summing or subtraction (cancellation) try toggling the phase for one band pass or another. Do not worry your little head about this - just listen to the result and how the response curve looks.

    Have fun.
    bo

    "Indeed, not!!"

  5. #35
    Senior Member NWCgrad's Avatar
    Join Date
    May 2015
    Location
    Frederick, MD
    Posts
    107
    Quote Originally Posted by boputnam View Post
    1) Use a quality measurement mic which comes with a response curve measure for it. Earthworks M30 is suitable.
    2) I prefer measuring where the listening will be done. In the field, we move the mic(s) around to different locations and average. In the home, I fix one position - the sweet spot - and pin it down. The adjacent positions won't be so different (unless you have really beamy horns).
    3) Ibid
    4) Ibid.

    For a three-way that is tri-amped, you must do each band pass separately. DO ONLY ONE SIDE OF THE SYSTEM; copy to the other side. However, first, establish your delay(s). The LF will have the most retarded acoustic arrival time due to the LPF. Measure it's impulse and delay the other band passes to match. Then, tune each band pass separately, striving for flat reproduction of Pink noise. Then, open all band passes and measure the overall reproduction of Pink. Look at the response at the crossover points - if you see summing or subtraction (cancellation) try toggling the phase for one band pass or another. Do not worry your little head about this - just listen to the result and how the response curve looks.

    Have fun.
    Thanks for the advice...it should be a fun adventure getting the big beast dialed in for optimal performance. Will start off bi-amped (have passive XO for the HF/MF), next year will upgrade my Peavey VSX to the DBX Venu360 and go fully active. The Peavey has some weird software controlled gain structure that induces noise if used to attenuate the signal for the HF unit. Makes it a poor choice for this application, but it is what it is.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. S4700 for sale in the USA
    By Valentin in forum Lansing Product General Information
    Replies: 64
    Last Post: 12-16-2015, 08:24 PM
  2. S3900 is better than S4700???
    By martin_wu99 in forum Lansing Product General Information
    Replies: 440
    Last Post: 01-06-2014, 09:56 AM
  3. S3900 now part of JBL Synthesis US lineup.
    By Dave_72 in forum Lansing Product General Information
    Replies: 22
    Last Post: 01-13-2013, 09:56 PM
  4. Jbl S4700
    By 10 Watt Street in forum Lansing Product General Information
    Replies: 14
    Last Post: 10-04-2012, 11:27 AM
  5. New JBL model S4700 debuts at Audio Video Logic
    By jpw in forum Lansing Product General Information
    Replies: 10
    Last Post: 03-28-2012, 07:25 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •