Page 1 of 2 12 LastLast
Results 1 to 15 of 26

Thread: Going to active xover

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Senior Member
    Join Date
    Mar 2010
    Location
    Saint-Roch-de-l'Achigan
    Posts
    207

    Going to active xover

    Hi everybody! Just want some hints about time align via the Berhingher DCX 2495. There I is an option for the auto align between woofer and horn mid tweeter(JBL 2420) I was thinking that the dcx needs to listen or it is just misaligned coils measured in inches.... sorry for my English...

  2. #2
    Senior Member BMWCCA's Avatar
    Join Date
    Feb 2006
    Location
    Virginia
    Posts
    7,735
    I could give more credence to time-alignment if instruments and vocalists (and orchestras) were two-dimensional. Otherwise I just don't understand the extra layer of processing for what amounts to at most a 10-inch deviation. I'm sure I'm wrong and that someone will tutor me on its importance!
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

  3. #3
    Dang. Amateur speakerdave's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    3,734
    It does seem to be a debate. Time alignment, I think, was developed for, or was early applied to the UREI monitors, which used coaxial drivers, a very important detail. With drivers spread around a baffle alignment can at best exist in one spot.

    Single driver speakers are inherently time-aligned, though of course they have their own limitations. But to get a sense of the point source/time-aligned effect a listening session with some full range drivers might let you see what people are shooting for. Imaging can really be a lock with them.

    I have two sets of Tannoy 2558 coaxial drivers. One set is in the stock SGM10B cabinet, the other in the Manley cabinet with the time-aligned crossover. It really does make the music more coherent, if the recording is coherent.

    You get close to an important point when you point out different location of instruments, but I think it is actually the microphone placement which matters. Multitrack studio recordings of electric rock and jazz are unlikely to benefit much from time-aligned speakers, whereas simply miked stage recordings of acoustic classical, folk and jazz music very well could.

    Simply put, whatever coherence exists in the recording can be preserved in the listening with time-aligned speakers.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  4. #4
    Member Mitchco's Avatar
    Join Date
    Feb 2013
    Location
    Sunshine Coast, Canada
    Posts
    82
    Many years ago, I recorded/mixed for a living for 10 years. Loved those Urei 813 series time aligns better than any other studio monitor I used at the time (large format or nearfields).

    Today's audio DSP software is very sophisticated running on powerful computers. Time alignment can be achieved with a high level of accuracy and precision. Here as an article time aligning JBL 4722 cinema speakers: https://www.computeraudiophile.com/c...kthrough-r682/

    I performed many experiments with time alignment and if you know what to listen for, it becomes easier to hear the difference, especially with subwoofers which usually are delayed 3 to 5ms behind mains in a typical home stereo setup. Several of these experiments were blind testing of switching digital FIR filters in near real time in a music playback system, with one filter set with no delays, and the other time aligning the drivers. Frequency response was the same for both filters.

    The eBook in my sig goes into great detail and shows time alignment is not just for one mic position, as I was able to show time alignment in 14 measurements across a 6' x 2' listening area.

    If going active, worth the effort to time align as well. If using linear phase digital XO's one can time align so that the direct sound arrives at ones ears all at the same time, and in phase. All good listening fun!

    Edit: Go for it! Give it a try. Even try adding too much delay to get a sense of what it sounds like, not only timing wise, but tonally as well. I have found no amount of eq can get rid of a tweeter arriving first and always having that in your face sound...

  5. #5
    Member
    Join Date
    Mar 2012
    Location
    Sutter Creek, CA
    Posts
    57
    Ian, that was pretty clear!

    I noticed a good graphic put up by Frank23 in an earlier thread. Here it is:

    http://www.audioheritage.org/vbullet...-and-2420-2344

  6. #6
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,939
    Great thread

    It’s an interesting problem.

    In my own experience the realities or physical possibilities dictate how much movement can be tolerated.

    For example with a 15 inch woofer you can indent it about 50mm before everything goes to hell.

    The pink noise is a great idea in the absence of test equipment. Trust your ears!

    But like using 2123 is actually a bit tricky.

    The 2123 diffracts with any baffle or horn obstruction like hell in the 600-1200 range due to its wider dispersion.
    You hear it as ghosting. So the best option is to tweak the crossover rather than move the horn forward to get the reverse phase suck out.

    I agree with Mr Widgets comments in that thread.

  7. #7
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,939
    I have attached some images to illustrate the effect of correct summing at the crossover point.

    The first 2 images are vertical polar based on actual measurements at 10 degree intervals.
    Those measurement were then uploaded into LEAP to display polar response curves with the crossover.

    With a bit of screwing around I was able to obtain a uniform reverse phase notch at the design point.

    The left image is out of phase, the second image is in phase.
    The deep notch is the reverse phase at the crossover point (800 hz). The slopes are 36 db per octave so there is not much impact either side of the crossover point whom is what you want in theory.


    The deep nodes are normal either side of the central node and their location will depend on a number of factors.
    My design point was slightly below the centre point.

    The other two curves are out of phase frequency response and in phase. Green is the summed response.

    This is a 2 way design using a 15 inch woofer and a large horn.

    You don't need this precision but its kind of cool to see what happens.
    Getting it right does make a significant difference subjectively. The rules are the same for passive or active crossovers. Ideally you want an adjustable active crossover with independent adjustment of Low and High pass crossover points like the analogue First Watt B4 or a dsp crossover.

    BTW the acoustic centre can be deeper than the woofer voice coil due to the group delay of the low pass filter possibly 0.2 ms or more.

    So if your horn is deeper than the woofer don't stress.
    Attached Images Attached Images     

  8. #8
    Senior Member 1audiohack's Avatar
    Join Date
    Jul 2007
    Location
    Las Vegas Nevada
    Posts
    3,092
    Quote Originally Posted by BMWCCA View Post
    I could give more credence to time-alignment if instruments and vocalists (and orchestras) were two-dimensional. Otherwise I just don't understand the extra layer of processing for what amounts to at most a 10-inch deviation. I'm sure I'm wrong and that someone will tutor me on its importance!
    Since this train jumped the tracks right out of the station, what the heck. maxserg sent another.

    I think you have it right. On one side anyway.

    Mic or direct record something or someone and play it back through a speaker system with more than one radiating element and all sorts of issues creep in, time delay distortion being one of them. This is the other side of the coin.

    I am with Mitch, getting it right has value. Being familiar with the sonic signature of well aligned sources makes poorly aligned sources difficult for me to truly enjoy.

    Like any engineering project, one chooses what to pursue and how far to pursue it.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  9. #9
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,939
    Quote Originally Posted by maxserg View Post
    Hi everybody! Just want some hints about time align via the Berhingher DCX 2495. There I is an option for the auto align between woofer and horn mid tweeter(JBL 2420) I was thinking that the dcx needs to listen or it is just misaligned coils measured in inches.... sorry for my English...
    It’s a fun idea to play around with but simply attempting to time align the voice coils is not the whole issue

    Your only scratching the surface.

    Loudspeaker drivers, crossover network and a b c location of drivers all cause a culmination of delay and what is termed group delay.

    Fixing it is neither easy or in expensive if you don’t want to degrade the audio signal.

    On top of that you have the whole room interaction thing going on as well.

    There are systems like Acourate (or other DSP programs that generate FIR filters), the Dirac and packages like DEQX that combine the hardware and software. They are not easy to use for the average person and tend to over promise on benefits.

    Here is a simple approach

    Grab your 4 way Jbl and let your HT receiver do the full Monty on room and loudspeaker correction
    I did this with my Pioneer LX 83

    I then look at the corrections. The frequency response and group delay and levels were largely smoothed out.
    On some program material it was subjectively an improvement.
    But when compared to the unprocessed signal with high quality DACs and amplifiers there is a loss of fidelity with the processed signal.

    Not everyone cares or is concerned about the impact of signal processing so you need to pick the route and go from there. It’s entirely up to the user.

  10. #10
    Member
    Join Date
    Mar 2012
    Location
    Sutter Creek, CA
    Posts
    57
    Ian,

    Great images! The verticle images are really interesting, with the green line showing a really smooth response on those 10 degree intervals. Even if it is summed, that's got to sound smooth.

    Awesome!

  11. #11
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,939
    It’s tedious getting it just right.

    I always do reverse phase once the crossover slopes are good.

    Don’t rely on or aim for an in phase smooth response (only)

    If you can swing it buy a measurement device from like Parts Express and start on getting some measurements. It’s not hard and you will doing the real deal as opposed to talking to people about what works in no time

  12. #12
    Member
    Join Date
    Mar 2012
    Location
    Sutter Creek, CA
    Posts
    57
    Kind of been waiting for this topic. Driverack 260's have become pretty affordable and I'm thinking of stepping into this arena.

    Where the output of two drivers overlap at or near the crossover point, there is the possiblilty of a cancellation of sound waves. This assumes the drivers are not in the same plane. This would be most noticable if the high pressure wave of one driver meets a low pressure wave from another driver at the same frequency. Even if its slightly off, there will be some effect. The harmonics could also be distorted by this process. Half of the sound waves for the next octave could be cancelled.

    The type of xover and the rolloff for the lower and higher drivers would define the range of frequency affected. The steeper the rolloff, the smaller the range of frequencies affected, except for the harmonics. The perception of harmonics may be impacted outside this range. If a second harmonic is cancelled you my hear a fundamental and the 3rd harmonic more strongly, which would color an instrument somewhat.

    I would expect some soundstage and location information to be lost. However, I've noticed more of a tonal change to specific notes when bi-amping my bass. Moving the drivers (in separate cabinets) can change the tone for some notes. I'm crossing at 800hz, so its the harmonics getting cancelled. The fundamentals are all far below that.

    Barry, I remember seeing a thread on time alignment where you were trying to dial your system in. Sounds like you had some success.

    I'm guessing how intolerable this is depends on an individual's hearing and listening skills and whether they can pick off these effects. If so, it probably is worthwhile to do the alignment.

  13. #13
    Senior Member
    Join Date
    Feb 2009
    Location
    annapolis, md usa
    Posts
    702
    I have no experience with active crossovers, but have had the pleasure to watch 2 active systems (one a 4 way custom studio monitor, the other a 3 way diy planer/open baffle woofer array/subwoofer system similar to the Infinity IRS) that were installed by knowledgeable people and tweaked for many hours. Then, each was tuned by the deqx tech over the interweb, and significantly improved in about an hour each. Both involved slight adjustments to time alignment differently than the installers had performed. It's fly fishing.

    Learned about the service in this thread.
    http://www.audioheritage.org/vbullet...their-products

  14. #14
    Member
    Join Date
    Aug 2019
    Location
    UK
    Posts
    36

    4430 active crossover

    Has anyone measured the voltage drives to the 4430 transducers via the passive crossover. I have a pair of 4430's minus crossovers for which I'd like to create an active crossover. The voltage drives to the transducers via the passive network would be a useful starting point .

  15. #15
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,163
    Take a look here second post. This gives you the woofer curve. The top you are going to have to sim or look for this is a biamp with passive CD comp in place.

    http://www.audioheritage.org/vbullet...ight=4430+5235

    Rob
    "I could be arguing in my spare time"

Thread Information

Users Browsing this Thread

There are currently 2 users browsing this thread. (0 members and 2 guests)

Similar Threads

  1. 033 HF best hz xover?
    By midlife in forum Lansing Product General Information
    Replies: 10
    Last Post: 08-21-2009, 09:30 AM
  2. 075 - is xover at 5k too low?
    By robertbartsch in forum Lansing Product DIY Forum
    Replies: 8
    Last Post: 03-21-2009, 01:16 AM
  3. s38 xover
    By oldschool in forum Lansing Product Technical Help
    Replies: 0
    Last Post: 02-26-2006, 07:09 PM
  4. Impedance and active xover.
    By JuniorJBL in forum Lansing Product Technical Help
    Replies: 2
    Last Post: 02-27-2004, 05:49 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
  •