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  • #16
    Re: Line array center channel

    Sydney, Thanks for the input and clarifications - I'm accustomed to people either "jumping in" on a thread to either (and in no particular order of relevance) A) replying for the sake of something to do B) replying to bump their post numbers c) trying to sound like they know something d) regurgitating information gleamed by methods other than experience, etc, etc.
    I have been considering an array for a center for a few years and gathering pieces to do so - now is the time for me to gather more of the info needed to accomplish the task - The CBT was also fuel for the fire.
    For some reason I was fearful of souunding like either the newb w/ head in arse, or the old guy that eveyone ignores. At any rate I've been "at it" since the mid 70's so I see you have a few years on me- good to know - I just know that many things in life that are found to be challenging some folk will shy away from for whatever reason. I'm more of the opposite and tend to jump in and give it a go and have spent much of my youth "figuring it out" My loudspeaker cookbook and other references are dog-eared and thread bare on the binding from the countless hours of thumbing through them. The older I get the more I consider it's "time" to just plain build the impossible end all final speaker system for my personal use. I'm not looking to attain perfection, just my own personal nirvana. (short of perfect forthe masses, yet perfect for me and my environment .
    I'll keep chugging along until' I find the answers - as usual-

    My intentions are to hopefully shorten the learning curve through the aid of others experiences and knowledge - Thank You all for the input, and I look forward to more exchanges on this thread
    "Over 50% of the people are below average" . . . Doug D.

    Comment


    • #17
      Re: Line array center channel

      [QUOTE=r-carpenter;1872890]There's no voodoo in building arrays and I am not trying to discourage you at all. While arrays are more difficult to build then a conventional speaker, it's not impossible and results can be stunning. I build a few..... But you need to look at line array specific design issues.
      Go on Tolvan web site and download their diffraction modeler. It'll give you an idea of how multiple drivers in the array will play together and how much of HF loss you will have, depending on the number of drivers.

      Thanks, I'll be looking there - Like I said , I've read most all of the white papers I can find on the subject and have considered all the issues to overcome or incorporate to attain the result- I have looked at directivity issues and response, however being new to arrays, I'm still getting a handle on some of the details involved. My initial post is based on all I have found for info and efforts to confront pitfalls prior to commiting hours on a design that will fail miserably. I can build anything, I'm just getting old enough to not want to be wasteful in my efforts, as I had been in my youth.

      I am in the process of gathering pieces software etc to aid in measurements. I had never been one to "measure" anything, just build it and listen- sound like crap ? toss it and re-design. I do however still have my Radio Shack 33-2050 SPL meter from the car-fi days. MOst of the drivers I am experimenting with have little if any specs attached so I'm sort of "winging it" for now in the design stage- if all goes well I'll bite the bullet and invest in some higher quality drivers. I have yet to end up with crappy sound simply because of poor driver selection (I have a good idea what NOT to buy so it helps alot) I've built some pretty impressive sounding stuff out of some not so impressive drivers in the past -
      "Over 50% of the people are below average" . . . Doug D.

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      • #18
        Have you checked out Monte Kay's center?
        https://www.google.com/url?sa=t&sour...oEASX8i5m4cgMg
        ErinsAudioCorner.com

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        • #19
          Re: Line array center channel

          I have seen a thread describing a curve CC line array build... can't find the link. Massive build as I recall...
          Frank

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          • #20
            Re: Line array center channel

            That's it!

            Comment


            • #21
              Re: Line array center channel

              Go to Monte's page to see the entire system http://www.mfk-projects.com/home_theatre.htm very impressive - this was actually what finally fueled the fire for me - If you go to DB Keeles page you can download a "goodies CD" chock full of way cool information and more.

              Tolvan site has some nice stoftwares - Good thing it's the weekend, I won't be getting much sleep -again-
              "Over 50% of the people are below average" . . . Doug D.

              Comment


              • #22
                Re: Line array center channel

                Dave you made some interesting points in post 16,17. Certainly being on a forum can be rough and tumble and I know many have misinterpreted the intent of my prior posts.
                My background has similarities to a others on the forum. My father was an electronics engineer for major consumer electronics firms and so I was surrounded by tubes/transistors and soldering irons since the 50's. That meant early electronics classes and latter college. This is why I post the natural of the links I do; Academic or from Industry.
                I can appreciate the rationale for understanding the underling principles even though it may strike others as unnecessary - indeed some may get the impression of condescension when a link is provided. In this case - impedance calculation is straightforward and can be resolved the same rules of circuit analysis I learned it the 60's. A calculator/spreadsheet is not really needed, and it's handy, but I really believe it pays to know how it works.
                Since I worked with polarized light in the 60's aspects of light behavior helped my understanding of acoustic behavior.
                I would also contend that it is possible to study and understand something without having to physically build it.

                As Roman stated ( and he has loads of experience ) there is a lot more than the electrical aspects ( such as impedance ) involved in speaker and array design.
                Marlboro also has built a lot of arrays, and ( not to offend anyone by omission ) others as well.
                "Not a Speaker Designer - Not even on the Internet"
                “Pride is your greatest enemy, humility is your greatest friend.”
                "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                Comment


                • #23
                  Re: Line array center channel

                  Sydney - Thanks for the input and info. Being I tend to see "forums" in a cynical light "I read it on-line it must be true" I appreciate your straightforward approach and back to basics train of thought, since as you stated it is basic math. I just didn't want to have to go back to hand calculating it all- I have notebooks full of old designs and formulas and - you know- Having a simple spreadsheet helps to expedite the design process - I agree, it can all be understood without having been built. Personally I like to do both since we all know that "in theory" can certainly come around and bite you from time to time.
                  "Over 50% of the people are below average" . . . Doug D.

                  Comment


                  • #24
                    Re: Line array center channel

                    I was a Department Head at a College teaching - so it's hard to turn off the notion that I might be depriving someone of a valuable learning experience :p
                    "Not a Speaker Designer - Not even on the Internet"
                    “Pride is your greatest enemy, humility is your greatest friend.”
                    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                    Comment


                    • #25
                      Re: Line array center channel

                      Originally posted by stereo_dave View Post
                      and nothing is "too difficult" if somebody figured out how to do it, then so can I.

                      I know anything is possible, mainly since I'm "the guy" a lot of people call on when they need something. Like I said , there's gotta be an array geek hiding somewhere that can add some value to this thread.
                      I assume the array is horizontal.

                      You need to model your midwoofers in a horizontal array and analyze the off axis results. This will tell you where you can cross at. A program like the edge is very valuable in planning this type of design. Typically for a driver this size it needs to be low to the tweeter. If you cross high to a tweeter then you will have a lot of off areas of interference in the horizontal plane between the midwoofers. As the midwoofer goes higher in frequency the interference issues become of greater concern. Try to use a tweeter that can cross at 1500Hz or lower. Not to say that 2000Hz crossover to the tweeter is the end of the world it will just start to get in the area of compromising sound quality.

                      Keeping the drivers as close as possible is always. best. Power tapering is not requirement. Splaying the baffle can help also in widening the horizontal dispersion of the speaker. But it also creates another set of issues.

                      Now as others have advised to be most successful at this it pays dividends to be able to measure.

                      I would try to use a single tweeter or a couple of small tweeters stacked vertically and mounted in the center a MMMMTMMMM arrangement, since using multiple tweeters in horizontal a horizontal layout is going to have very limited horizontal dispersion and a lot of interference that results in deep dips as you move along the horizontal plane.
                      Dave

                      If you can read this, thank a teacher.
                      If you are reading it in English thank a Veteran
                      .

                      Comment


                      • #26
                        Re: Line array center channel

                        Design of a line array is fundamentally the same as design of any other loudspeaker and you need to know the passband of the drivers. Even in the multiple numbers it is very important to look at frequency response and distortion numbers. Your tweeters may not go low enough clean or the woofers high enough. Given high frequency loss of the combine woofer response, you may need to deign the crossover to compensate and if the distortion numbers are highish which is usually the case with buyouts, you may need to either change the woofer or add a line of mids. Anyway, without solid data, it's only a guess.
                        My way of going about it would be first looking at the drivers. You can download ARTA/LIMP software (it's free without save option) and use that to look at acoustic output and TS parameters of your drivers. You will need a measurement mic like ECM8000 or slightly cheaper Dayton mic. You will also need phantom power for these. All in all, probably a $80 investment.
                        You will also need to make a voltage divider jig for LIMP which is another $7 in parts.
                        While learning measurement techniques you can play with "Edge" and see what will work for your concept.
                        Then the rough concept is developed and modeling is more or less completed, decision can be made about implementation.
                        There are some measurements here if you want to take a look: http://techtalk.parts-express.com/sh...buyout-project
                        http://www.diy-ny.com/

                        Comment


                        • #27
                          Re: Line array center channel

                          Originally posted by dthomas View Post
                          I assume the array is horizontal.

                          You need to model your midwoofers in a horizontal array and analyze the off axis results. This will tell you where you can cross at. A program like the edge is very valuable in planning this type of design. Typically for a driver this size it needs to be low to the tweeter. If you cross high to a tweeter then you will have a lot of off areas of interference in the horizontal plane between the midwoofers. As the midwoofer goes higher in frequency the interference issues become of greater concern. Try to use a tweeter that can cross at 1500Hz or lower. Not to say that 2000Hz crossover to the tweeter is the end of the world it will just start to get in the area of compromising sound quality.

                          Keeping the drivers as close as possible is always. best. Power tapering is not requirement. Splaying the baffle can help also in widening the horizontal dispersion of the speaker. But it also creates another set of issues.

                          Now as others have advised to be most successful at this it pays dividends to be able to measure.

                          I would try to use a single tweeter or a couple of small tweeters stacked vertically and mounted in the center a MMMMTMMMM arrangement, since using multiple tweeters in horizontal a horizontal layout is going to have very limited horizontal dispersion and a lot of interference that results in deep dips as you move along the horizontal plane.
                          +1........i initially refused to believe that this was a horizontal array. Using the tweeters in the horizontal will require a bessell array approach modified in groups of 5. It might actually work but i know of no software or sims to predict the outcome......

                          Comment


                          • #28
                            Re: Line array center channel

                            You know the center channel speaker sited above looks a awful lot like these: http://www.parts-express.com/cbt36/i...n=Catalog_2011

                            Could you build the kit and lay one on the side instead of standing it up?

                            Too simple?
                            Shaken, not stirred...

                            Classix II
                            OS MTM's
                            Digger 8 sub
                            Overnight Sensations Center Channel
                            Sprite Build
                            Wolf's PC Speakers
                            Minions III with Voxel Sub

                            Comment


                            • #29
                              Re: Line array center channel

                              Originally posted by kevin007 View Post
                              lay one on the side instead of standing it up?

                              Too simple?
                              Unfortunately that's too simple: The upright vertical CBT arc has the expectation of having a symmetrical mirror image created from the ground plane - so the base is the 0 reference, with progressive tapering with increase height, emulating a sphere.
                              http://www.xlrtechs.com/dbkeele.com/...%20Website.jpg

                              Now you could buy 2 and place them base to base with unshaded elements together and shaded elements on the outsides ( like the flown version ) :D
                              http://www.xlrtechs.com/dbkeele.com/...%20Website.jpg
                              "Not a Speaker Designer - Not even on the Internet"
                              “Pride is your greatest enemy, humility is your greatest friend.”
                              "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                              Comment


                              • #30
                                Re: Line array center channel

                                Ummm - thats pretty much what my thoughts were- minus the big price tag - Is everyone reading my original post correctly ? The CBT from PE has a 60 degree ars- I propose a 120 degree arc (60+60=120) w/ aprox 48" radius. At any rate- I'm knee deep in getting measurement software loaded and calibrating mic-lines, etc. Slight problem - following directions to the tee I still end up getting tons of ground floor noise - even with the mic unplugged - any thoughts? I won't lose any sleep over it- Tried arta and REW with the same results - I'm using my Rad Shack 33-2050 old school analog meter line out to the pc - line out to the amp- mic muted etc. still end up w/ response curve similar to pink noise. I should have a flat reading registering (close to) zero with no sound present in the test area, right ?? (when I say "no sound" I mean it is a silent room w/ no external noises present, I would assume a nice flat line to be the norm. I'm new to measuring , but not to the rest of it - long history of RTAing Car-Fi so I'm pretty sure I got it right ? ANy help appreciated- it's possible I missed something- I'm only a human
                                "Over 50% of the people are below average" . . . Doug D.

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