Results 1 to 12 of 12

Thread: 4345 Bi-Amp Crossover Questions

  1. #1
    Junior Member
    Join Date
    Mar 2020
    Location
    San Diego, CA
    Posts
    9

    4345 Bi-Amp Crossover Questions

    Good day all,

    I have a stock pair of 4345. Currently I am running an electronic JBL 5235 urei crossover with the 4345 cards. Both high-range and low-range going through it.


    Recently picked up a Minidsp SHD. It has 4 analog outputs for bi-amping and I can digitally setup the crossover points.

    How do I set up crossover?

    For low pass I found the recommended 310hz cutoff with a LR 24dB/oct filter. Going to the low range amp.

    But what about for the high-pass section? Or should I just run it full range into the 4345 high-range?

    Any help will be much appreciated. I am quite young and inexperienced, but this is so exciting falling down the JBL rabbit hole.

    After this I will be running Dirac room correction through the SHD with the minidsp measurement microphone. Any other useful softwares to conduct measurements?Name:  IMG_20200509_111017.jpg
Views: 297
Size:  75.8 KB

  2. #2
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,235
    No you should also high pass as well. Try the same and see it you like it.

    Here is the schematic. You can see the biamp switch takes out a couple of poles in the high pass

    network http://www.jblproservice.com/pdf/Net...%20Network.pdf



    Rob
    "I could be arguing in my spare time"

  3. #3
    Junior Member
    Join Date
    Mar 2020
    Location
    San Diego, CA
    Posts
    9
    Quote Originally Posted by Robh3606 View Post
    No you should also high pass as well. Try the same and see it you like it.

    Here is the schematic. You can see the biamp switch takes out a couple of poles in the high pass

    network http://www.jblproservice.com/pdf/Net...%20Network.pdf



    Rob
    Thank you for the response. The sound isn't dynamic or attractive when I use this minidsp to bi-amp. Tried a few combinations but not doing it.

    Next in line is the bryston 10b crossover.

  4. #4
    Senior Member
    Join Date
    Jul 2003
    Location
    Orange County, CA
    Posts
    3,304
    Quote Originally Posted by Robh3606 View Post
    No you should also high pass as well. Try the same and see it you like it.

    Here is the schematic. You can see the biamp switch takes out a couple of poles in the high pass

    network http://www.jblproservice.com/pdf/Net...%20Network.pdf



    Rob
    What is the value of the choke on the 18"?

  5. #5
    Senior Member Ian Mackenzie's Avatar
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    5.4mH

  6. #6
    Senior Member
    Join Date
    Jul 2003
    Location
    Orange County, CA
    Posts
    3,304
    Quote Originally Posted by Ian Mackenzie View Post
    5.4mH
    Interesting, thanks. Seems like a lot of capacitance for a 5.4 mH choke. For a 2nd order Butterworth, 5.4 mH would go with 42 mfd for a frequency of 335 Hz. I guess they wanted to increase the rolloff above that frequency.

    An 8mH/62.5 mfd is used for a second order Butterworth at 225 Hz. I have been using 8 mH/77 mfd on the 2241H.

  7. #7
    Senior Member Ian Mackenzie's Avatar
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,409
    Hi Todd,

    This is off topic. If you want to start a new thread by all means....

  8. #8
    Senior Member
    Join Date
    Jul 2003
    Location
    Orange County, CA
    Posts
    3,304
    Quote Originally Posted by Ian Mackenzie View Post
    Hi Todd,

    This is off topic. If you want to start a new thread by all means....
    Not necessary. Thanks.

  9. #9
    Junior Member
    Join Date
    Mar 2020
    Location
    San Diego, CA
    Posts
    9
    I was doing some measurements with pink noise. Is it easy to blow up the high frequency components by doing this? I thought the crossover has some filtering to prevent this. But now my high-end sounds strange, there is sound coming out of all the drivers but more weak and compressed sounding.


    Or... did I blow my hearing

  10. #10
    Senior Member grumpy's Avatar
    Join Date
    Oct 2003
    Location
    SoCal
    Posts
    5,477
    Let it rest (particularly your ears) What levels were you testing at?
    Unlikely to blow those speakers at levels where you can stay in the room (factory crossovers).
    Much more likely to pop with sustained tones.

  11. #11
    Senior Member
    Join Date
    Apr 2003
    Location
    Covington, Ohio
    Posts
    709
    Quote Originally Posted by jbljr View Post
    I was doing some measurements with pink noise. Is it easy to blow up the high frequency components by doing this? I thought the crossover has some filtering to prevent this. But now my high-end sounds strange, there is sound coming out of all the drivers but more weak and compressed sounding.


    Or... did I blow my hearing
    If you some how hit the tweeter with full range or almost full range pink noise at a high level it could have damage the diaphragm, same goes for the compression driver.

    If your using the word "what?" a lot in conversation lately after your testing then maybe the testing was too loud!!!

    You may want to apply a high pass filter as well on the low output channel.
    Maybe 35 hz. at least a 18db BW filter.

  12. #12
    Senior Member
    Join Date
    Apr 2014
    Location
    Europa Union
    Posts
    111
    Quote Originally Posted by jbljr View Post
    Good day all,

    I have a stock pair of 4345. Currently I am running an electronic JBL 5235 urei crossover with the 4345 cards. Both high-range and low-range going through it.


    Recently picked up a Minidsp SHD. It has 4 analog outputs for bi-amping and I can digitally setup the crossover points.

    How do I set up crossover?

    For low pass I found the recommended 310hz cutoff with a LR 24dB/oct filter. Going to the low range amp.

    But what about for the high-pass section? Or should I just run it full range into the 4345 high-range?

    Any help will be much appreciated. I am quite young and inexperienced, but this is so exciting falling down the JBL rabbit hole.

    After this I will be running Dirac room correction through the SHD with the minidsp measurement microphone. Any other useful softwares to conduct measurements?Name:  IMG_20200509_111017.jpg
Views: 297
Size:  75.8 KB

    When using LR24 for Low and High filtering, in bi-amp mode, supposing that you have one amp for LF and one amp for HF, you have to reverse the polarity either at the output either of the HF amplifier or the LF amplifier, to keep loudspeakers in phase.
    When using a 12dB crossover (easy with your 5235, just find two 12dB/oct blank cards and fill them with the values for JBL 4350) polarity shall not to be inverted. This is also the case with the original 53-5145 board for 5235, as per JBL set up, whereas you can try listening with the inverted polarity on one of the amps, as the two possibilities are working. I prefer the version with HF amp or LF amp polarity inverted.

    If you used minidsp for LF and HF LR24 filters and didn't inverted the polarity of one of the two amps, the sound wont be good.
    For 24dB/oct crossover you can also try JBL M552, or Rane AC22 (that has a delay that you can apply to the 18" to perfect the time alignment with mid.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. 4345 With 4355 Crossover Help
    By robertg in forum Lansing Product DIY Forum
    Replies: 4
    Last Post: 05-05-2020, 11:06 AM
  2. 4345 Crossover Parts FS
    By RC Driver in forum Lansing Product Technical Help
    Replies: 11
    Last Post: 09-25-2018, 11:59 AM
  3. Jbl 4345 Consensus best passive bi-amp crossover?
    By cgregory4 in forum Lansing Product Technical Help
    Replies: 7
    Last Post: 09-10-2014, 08:04 PM
  4. 4345 Project Questions Again...
    By JBLCanuck in forum Lansing Product DIY Forum
    Replies: 4
    Last Post: 01-23-2009, 06:07 PM
  5. 4345 Questions
    By sourceoneaudio in forum Lansing Product DIY Forum
    Replies: 17
    Last Post: 05-18-2007, 01:14 PM

Tags for this Thread

Posting Permissions

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