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Crossovers and Stero Imaging - Basic Question

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  • Crossovers and Stero Imaging - Basic Question

    Hello all

    I've tried looking this up on Google and searching forums, but I haven't really found the answer.

    Exactly how does the crossover help with the stereo image, please?

    I know what a crossover does, and how stereo works, but as a newbie, I don't understand how they work together.

    For example, the recording mixing engineer decide which parts of the music go to each stereo channel. The source, amplifier and crossovers can't change that.

    The left and right speaker crossovers then separate the incoming signal for left and right channels into two or three components to go to the speaker drivers, and you get marvellous music.

    I've found that my DIY speaker builds give me a better "stereo image" than my older commercial bookshelves, e.g. I can better place individual instruments in the mix when I close my eyes.

    So why do some crossovers/speakers "image well", and others apparently not?

    Thank you and apologies for such a basic question!

    Geoff

  • #2
    That is by no means a basic question. I can't give a good answer, but there is a whole lot of psychoacoustics going on for what we perceive as imaging.

    ​Things I can think of, but am by no means an expert to expand on:
    ​Our brains rely in the timing of sound hitting our ears for directional perception and therefore imaging. The crossover can affect that somewhat, particularly in phase response and coherency between drivers. The driver offsets can also affect that, as well as the reflections in the listening environment. Dispersion directly affects the amount and range of the reflections, therefore the cabinet design and driver choices can control that a bit as well.
    Electronics engineer, woofer enthusiast, and musician.
    Wogg Music

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    • #3
      Symmetry is very important.

      Crossovers contribute by assuring good power response, and minimal difference between channels.

      Also, it helps if the music is mixed well. No amount of engineering on the front end or speakers will create holographic imaging from something like The Beatles stereo mixes where it is vocals in one channel and instruments in another.
      Don't listen to me - I have not sold any $150,000 speakers.

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      • #4
        The DIY designs might just be better. As you reduce distortion, flatten response, create even off axis response so that reflections are natural, etc, the clarity and detail will allow the imaging in the recording to show up best. Sent from my SGH-I337M using Tapatalk
        https://www.youtube.com/channel/UCm2...oSKdB448TTVEnQ

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        • #5
          Originally posted by Geoff Millar View Post
          For example, the recording mixing engineer decide which parts of the music go to each stereo channel. The source, amplifier and crossovers can't change that.

          Geoff
          With regards to the crossover you're right, but not for the source or amplifier. Please look up "cross-talk".

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          • #6
            Originally posted by johnnyrichards View Post
            Symmetry is very important.

            Crossovers contribute by assuring good power response, and minimal difference between channels.

            Also, it helps if the music is mixed well. No amount of engineering on the front end or speakers will create holographic imaging from something like The Beatles stereo mixes where it is vocals in one channel and instruments in another.
            True, the early Beatles stereo records are pretty primitive in this respect. And some Hendrix releases have truly strange balances and bouncing of instruments between the channels; and this sounds more pronounced on my good speakers!

            Thank you all for your comments, most interesting: it's not as basic a question as I first thought!

            Geoff

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            • #7
              I may have missed it, but don't recall seeing phase in the discussion. Suspect good linear phase response in the crossover region helps maintain the mastering engineer's balance.
              Live in Southern N.E.? check out the CT Audio Society web site.

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              • #8
                Originally posted by carlspeak View Post
                ... Suspect good linear phase response in the crossover region helps maintain the mastering engineer's balance.


                "Not a Speaker Designer - Not even on the Internet"
                "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                • #9
                  I'll dip my toe in the water . I think you'll get a lo​t of different answers to your question (great question BTW). I knew phase would come in as one of them, but I think there's a lot more to it than phase. 2 examples...

                  ​I did a T/M build, the F/R was super flat and the phase was respectable in my initial xover design... but the speakers sounded dull and lifeless to me. In the end, allowing for a less flat response and sacrificing a bit of phase made these sound and image better to not only my ears, but also to everyone else that heard them. I can't quantify why, but maybe it's as simple as a (mild) peak here and there enhanced the vocals and instruments in areas that weren't offensive, but made the sound a little more 3 dimensional?? Just a guess.

                  ​I did a different build (a 3 way) where the phase is pathetic, but the speakers image amazingly. Not to sound too audiophile-ish, but these speakers definitely "disappear" when I listen to them, and placing instrumentation and vocals is almost eerie. These do have a respectably flat response.

                  ​But, with regards to your question, from my experience the xover can have a HUGE roll in imaging. JR brought up symmetry... having 2 drivers that get along is definitely critical, but 2nd to that is finding the xover point that these 2 drivers like to play together at. For example, just because you're using a Revelator 15w midrange with a SS 6600 tweeter doesn't necessarily guarantee a home run, you can have a nice looking response and even decent phase, but maybe not have the best sound you >could< be getting from these 2 speakers paired with each other... you still have to play with the xover. And not just the xover points, but the slopes (the orders), the output of the tweeter, etc. All these things can effect imaging. This is the art of xover design and also why it takes me so long to do a build (I want to know I tried everything before I call it "good"). I think there are a LOT of legitimate reasons for how or why a xover can effect imaging. Think of the end result of good sounding speakers as being 100% due to the xover, and 100% due to the drivers used... I know that doesn't equate but you get my point.

                  ​FTR, I'm not trying to start a war or say anyone is wrong, just my observations along the way.

                  ​As far as imaging and DIY vs commercial... I've heard both do really well or very badly.
                  "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                  "Audio is surely a journey full of revelations as you go" JasonP

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                  • #10
                    Check out AES.org paper #2136 to read about crossover topologies on FR and phase. It's an older paper but speaks to the OP's question.

                    Author's abatract:
                    " Practical Applications of Crossovers in Real Loudspeaker Systems



                    Thus far, the development of loudspeaker crossover networks has not been primarily concerned with the actual acoustical performance as applied in real loudspeaker systems. We will show, through both objective and subjective analysis, a new dividing network design as an excellent choice over existing designs with regards to: polar response, electrical power requirements, imaging, and tonal quality of loudspeaker systems.
                    Authors: Klapholz, Jesse; Sohl, Allan
                    Affiliations: Klaphotz Technologies, Philadelphia, PA ; ProfessiOnal Audio Systems, Harbor City, CA(See document for exact affiliation information.)
                    AES Convention:76 (October 1984) Paper Number:2136"

                    Last edited by carlspeak; 09-07-2017, 05:10 PM.
                    Live in Southern N.E.? check out the CT Audio Society web site.

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