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Thread: Center channel designs for home theater

  1. #1
    slxrti
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    Center channel designs for home theater

    Hi for the New Year I would like to build a great center channel for my home theater system. The mid bass driver (pairs) options are 2218H, M203H, 2123H or a pair of 8” morel drivers, for midrange a single 2416H and maybe a single 2404 for the ultra high freq’s. The speaker configuration could be either a MTM or MT, depending or each merit's.





    Before I let the wood chips fly I have a few questions:



    What sonic qualities create a great center channel?



    What should the low end freq response (-3db) to shoot for?



    Which mid bass would you choose (why)? And what would be your crossover freq (why)?



    My current center channel (Citation) requires vertical placement for producing a narrow sound field for dialogue. Can a rectangular cabinet/MTM configuration, but horizontal placement achieve the same results?



    As far as cabinet shape, rectangular is ok, but I prefer the mid bass drivers to be angle

    inward. What are the liabilities with such a design? Is there a range of angles to stick to?



    The horn I’m using has a very wide dispersion, what are the repercussion for center channel usage?



    More question’s on the way,



    Thanks, Slxrti

  2. #2
    Senior Member edgewound's Avatar
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    In a 5.1(7.1, 10.2...) all the speakers should be identical in response....so anything different will be a compromise. Other than that try to design your center channel to be as close a match as possible to your left/right channels.

    Probably not the answer you wanted to hear, but that's how it's done in the movie theater.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  3. #3
    Senior Member Don Mascali's Avatar
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    I am using 2, 2123J and a 2426H on a 2342 horn in a horizontal MTM. They are crossed over at 1600 hz.

    Some opinions;

    What ever you use should be a match in "Timbre" (Damn I hate to say that and sound like one of them Golden Ear types) for your front speakers. Three of the same accross the front would be ideal. Even Pro installations don't use all identical on the surrounds.

    I don't run mine below 80 hz because they sit almost on top of two 4546C subs. I don't feel that extreme highs or lows are that important.

    They do mostly dialogue on movies. When the action pans across the screen, it is obvious where the sound changes as each speaker picks up the sound, IF they are too different in Timbre. I use a projector wih an 108" screen and this requires some continuity to make it flow smoothly.


    A good system should image well enough to fill in the center in stereo mode. I use Pro Logic II 7.1 for music and the center helps. A lot of people find that heritical but it sounds good to me and that's the whole point isn't it ?

    Good luck in whatever you decide,

    Don M
    4406, 4412A, L100, L100t3 (3 pair), L1, L7, 4645C, 4660A, 4695B, SR4735 and various DIY JBL Pro loaded systems.

  4. #4
    slxrti
    Guest
    Quote Originally Posted by edgewound
    In a 5.1(7.1, 10.2...) all the speakers should be identical in response....so anything different will be a compromise. Other than that try to design your center channel to be as close a match as possible to your left/right channels.

    Probably not the answer you wanted to hear, but that's how it's done in the movie theater.
    I did not consider front speaker matching. Realizing that I don't design loudspeaker for a profession, I may have to lower my expectation to a
    good center channel.

    Slxrti

  5. #5
    Administrator Robh3606's Avatar
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    What are your mains??? Don't skimp on the center channel it's over 50% of your movies audio content. Match it as close as you can to your L/R. If you go horn try to keep the horns on the same plain vertically so the pan doesn't dip or go up. Try the 2342 alone and see if it works for you. If you drop a 2404 over it you will have to deal with integration issues like comb filtering. On the low end make sure your F3 is low enough so you can get through the crossover region without a drop in level caused by to high an F3. Depends on your slopes and what choices of frequencies you have in your processor.

    Rob

  6. #6
    slxrti
    Guest
    Quote Originally Posted by Don Mascali
    I am using 2, 2123J and a 2426H on a 2342 horn in a horizontal MTM. They are crossed over at 1600 hz.

    Some opinions;

    What ever you use should be a match in "Timbre" (Damn I hate to say that and sound like one of them Golden Ear types) for your front speakers. Three of the same accross the front would be ideal. Even Pro installations don't use all identical on the surrounds.

    I don't run mine below 80 hz because they sit almost on top of two 4546C subs. I don't feel that extreme highs or lows are that important.

    They do mostly dialogue on movies. When the action pans across the screen, it is obvious where the sound changes as each speaker picks up the sound, IF they are too different in Timbre. I use a projector wih an 108" screen and this requires some continuity to make it flow smoothly.


    A good system should image well enough to fill in the center in stereo mode. I use Pro Logic II 7.1 for music and the center helps. A lot of people find that heritical but it sounds good to me and that's the whole point isn't it ?

    Good luck in whatever you decide,

    Don M
    The 2123 is one of my options, what type of enclosure did you use?
    As far as shape, is the enclosures a rectangular box?

    What crossover slope did you use and why did you chose 1600hz as the crossover Freq?

    btw, people should be allow to make choices without
    criticism especially if it impact no one else, Enjoy what you have.

  7. #7
    slxrti
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    Quote Originally Posted by Robh3606
    What are your mains??? Don't skimp on the center channel it's over 50% of your movies audio content. Match it as close as you can to your L/R. If you go horn try to keep the horns on the same plain vertically so the pan doesn't dip or go up. Try the 2342 alone and see if it works for you. If you drop a 2404 over it you will have to deal with integration issues like comb filtering. On the low end make sure your F3 is low enough so you can get through the crossover region without a drop in level caused by to high an F3. Depends on your slopes and what choices of frequencies you have in your processor.

    Rob
    My main are 4430's, but in the future they will be replaced.

    To make sure I understand matching, does this implied only to freq
    response? If it does not, are there any other major design considerations?

    My thought was is to allow the natural roll off of the driver to determine the low end response. The slope would be either 12 or 24 db, depending on box type. If response below 100hz is not needed, than a close box maybe appropriate.

    The crossover to the horn would be handled passively, slope and crossover
    Freq have yet to be determined.


    slxrti

  8. #8
    Senior Member edgewound's Avatar
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    Quote Originally Posted by slxrti
    btw, people should be allow to make choices without
    criticism especially if it impact no one else, Enjoy what you have.
    My apologies to you for my expedient post....I wasn't intending any criticism of you or your abilties....rather, it was a quick guide on how HT systems are designed for the most pleasing theater experience in your home. You're right....you should use whatever you have available to you to complete your project. Maybe we can save you a little time and frustration by leading you down the right path for your center speaker to better integrate with what you currently have....others would rather do it their own way and learn along the way and have a never finished...or should I say " never ending".... project.

    And lately, some members just want to fight....whatever....

    Happy New Year to all.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  9. #9
    slxrti
    Guest
    Quote Originally Posted by edgewound
    My apologies to you for my expedient post....I wasn't intending any criticism of you or your abilties....rather, it was a quick guide on how HT systems are designed for the most pleasing theater experience in your home. You're right....you should use whatever you have available to you to complete your project. Maybe we can save you a little time and frustration by leading you down the right path for your center speaker to better integrate with what you currently have....others would rather do it their own way and learn along the way and have a never finished...or should I say " never ending".... project.

    And lately, some members just want to fight....whatever....

    Happy New Year to all.
    Oh Gee, I agreed with you!!! I didn't take what you wrote personally.
    I'm open to suggestions, thought's and word's of wisdom.





    btw, I read several other threads before posting this, they were to personal for my taste.



    Take care, Slxrti

  10. #10
    Administrator Robh3606's Avatar
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    Hello Sxrti



    I understand what you are saying about the roll off due to the box design however when you set a surround processor for a “small” center channel you have an electrical crossover that overlays the box response. If you don’t know where this is and the slope you can design in a nice hole into your system response. So at the very least you need response below where your processor does the crossover. If you can select the crossover point your fine. You don’t want the set point 20 hz below where the F3 knee on the box is. What are you replacing the 4430’s with???

    Match as in driver types as well. Don't mix domes and compression drivers. I have tried it and certainly didn't work for me. You want systems that have similar frequency response, which room placement will affect anyway, and transient characteristics. Movies are all about dynamics and good deal of it is front and center in the center channel. You don't want a slacker as the main event in your HT system. A good center can make or break an HT set-up. It should also have excellent powerhandling and enough power behind it to reach THX levels where you sit and not clip the amp.

    Rob


  11. #11
    Senior Member Don Mascali's Avatar
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    Please don't get discouraged or overwhelemed by this task. We all started somewhere and I have never heard a speaker sound better than one "I" designed. Some of them were total crap but I loved them anyway. Kind of like children.

    Some of the guys here think they are geniuses and some of them really are! The group here will see you through it and you will enjoy the most important part, DIY like the forum says.

    Any manufacturer who can't design a good speaker with all the resources available to them won't last long. We get to have the all the joy of creation and if we miss the mark we can start over. No big deal, it will still sound better than "Worst Buy" ect.

    It would help to know what you are going to change to. As for the 4430s match, Zilch has a thread bigger thn "War and Peace" with tons of options. Start reading that and you will think of something. The drivers you mentioned are all a good start.


    Remember, "It's a Journey, Not a Destination", enjoy the ride.
    4406, 4412A, L100, L100t3 (3 pair), L1, L7, 4645C, 4660A, 4695B, SR4735 and various DIY JBL Pro loaded systems.

  12. #12
    slxrti
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    Quote Originally Posted by Robh3606
    Hello Sxrti



    I understand what you are saying about the roll off due to the box design however when you set a surround processor for a “small” center channel you have an electrical crossover that overlays the box response. If you don’t know where this is and the slope you can design in a nice hole into your system response. So at the very least you need response below where your processor does the crossover. If you can select the crossover point your fine. You don’t want the set point 20 hz below where the F3 knee on the box is. What are you replacing the 4430’s with???

    Match as in driver types as well. Don't mix domes and compression drivers. I have tried it and certainly didn't work for me. You want systems that have similar frequency response, which room placement will affect anyway, and transient characteristics. Movies are all about dynamics and good deal of it is front and center in the center channel. You don't want a slacker as the main event in your HT system. A good center can make or break an HT set-up. It should also have excellent powerhandling and enough power behind it to reach THX levels where you sit and not clip the amp.

    Rob
    Hi Rob, I just checked my preamp, I have two choices. The "small" limits the low freq range to a f3 of 100hz, 18db slope. The large setting pass's full
    range info to the center.

    Using LSPCad I plotted the freq response of the 2123 and 2218. The response of the 2118 is down ~3db @ 120hz and the 2123 ~3db @ 170hz.

    What is the freq range necessary for a center channel?




    In the future I plan to replace the 4430's, with a 4 to 5 way system.
    Subwoofer's: 1500
    Lower Midbass: 2217
    mid base: 2123
    middle range: 375
    ultra high: 2404 or 2405.

    When I was younger I thought I would double up on the 2123 and 2404.
    I since scale back, one of each driver should be enough!!

    But, before I begin the 4/5way project I thought I should have at least one loudspeaker under my belt.

    slxrti

  13. #13
    Administrator Robh3606's Avatar
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    Well 70Hz seems to stick in my mind but obviously fullrange would be the best option. Have you looked at the 2118 spec sheet?? Run them in .5 cubic Ft tuned to 70Hz. With that tuning the knee is down but at 70hz and with room gain it may work out OK.

    http://www.jblpro.com/pub/obsolete/2118.pdf

    Are you stuck on these drivers??? I would look real hard at what your mains will be and use that to determine the driver set for the center channel. Do you really need 2217 and 2123??? Seem's the 2217 could cover the gap just fine between the 1500 and the 375. Don't make it any harder than you have too. Using the same drivers in the same ranges as the L/R is a good thing.

    http://www.jblproservice.com/pdf/Dis...ls/2217HPL.pdf


    Have Fun

    Rob

  14. #14
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    slxrti,

    Many people get worked up over the centre channel..I am not convinced it works all that well for music DVD's but might be impressive on Terminator 3.

    Another member is considering a similar idea in progress with 4 way sides and so he is using dual 2122H for the centre with a 2307/2308 horn/Plate assembly and a 2405. The sides will be the same with single 2122H mid cones crossed over at 300. You could opt for a LE14 woofer for the centre woofer.

    This is basically the mid / horn and top end of a JBL 4344..the dual 2122H should in theory have sufficient oomp down to 100 hertz or a bit lower due to its X max and heavier cone than the 2123.

    The hard yards on the crossover have already been done (some modification of the centre will be required) so you would have a good proven design and don;t have to start pioneering there.

    The 2235 or 2245 would round out the design for the bass in the left and right front channels and everything would match.

    Done properly this system would stand the test of time and play not just movies but music very nicely!

    Ian



    Quote Originally Posted by slxrti
    Hi Rob, I just checked my preamp, I have two choices. The "small" limits the low freq range to a f3 of 100hz, 18db slope. The large setting pass's full
    range info to the center.

    Using LSPCad I plotted the freq response of the 2123 and 2218. The response of the 2118 is down ~3db @ 120hz and the 2123 ~3db @ 170hz.

    What is the freq range necessary for a center channel?




    In the future I plan to replace the 4430's, with a 4 to 5 way system.
    Subwoofer's: 1500
    Lower Midbass: 2217
    mid base: 2123
    middle range: 375
    ultra high: 2404 or 2405.

    When I was younger I thought I would double up on the 2123 and 2404.
    I since scale back, one of each driver should be enough!!

    But, before I begin the 4/5way project I thought I should have at least one loudspeaker under my belt.

    slxrti

  15. #15
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    Hello i have one 2446j 2" driver + 2382a horn and 2 2226h 15" in a horisontal MTM config. The box is 2,4 meter wide . Crossover is 700 and 40 hz.

    2 closed chambers 140 liter each.

    regards mats

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