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  • Sydney
    replied
    Re: Murphy Corner Line Array (MCLA)

    Not yet...
    The material on Keele's "Goodies CD" had me pondering variations on a hybrid CBT for small venues. This is not an original idea so I'm still doing recon to see where younger sharper minds ( and bodies ) are on this concept.

    Leave a comment:


  • r-carpenter
    replied
    Re: Murphy Corner Line Array (MCLA)

    I think Sydney has a "line array" bug and about to build one if he didn't already. :D

    Leave a comment:


  • Sydney
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by John L. Murphy View Post
    The "focus" you describe is probably a reference to the narrow beam width that arrays exhibit in the FAR-field (distances large compared to the array length). This thinking applies to concert line arrays which are designed for far-field use. The MCLA does not behave this way because you listen to it in the NEAR-field where the sound field does not change with listening height. There is much confusion in casual speaker discussions about this very important distinction between how line arrays perform in the near-field versus far-field. The two situations are quite different and it is important to understand the distinction. Much of the analysis that applies to concert line arrays does not apply to line arrays in small rooms. Concert lines are almost always heard in the far-field.
    An important distinction is that concert line arrays are both physically articulated and the segments have signals that individually electrically conditioned to create a desired acoustic pattern.

    This is when the acoustic magic happens.
    A Physicist using the word "magic" :eek: ;)

    Leave a comment:


  • superspeeder
    replied
    Re: Murphy Corner Line Array (MCLA)

    Subscribing... I find this project very interesting, though I must admit I'm a bit skeptical since the project has been out there for over two years (I think) and not one person beyond the original creator has duplicated this system and reported on it with real detail.

    It really does sound like an awesome system, John. To your knowledge has it been duplicated AND documented anywhere else?

    Leave a comment:


  • lasse
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by John L. Murphy View Post
    The Behringer DCX2496 is a fine crossover but it may not offer enough EQ flexibility to correct the 3 dB slope of an array. If it is an existing EQ you could always try it out before getting the DEQ2496 which has the real EQ power you need for line array projects.

    Yes, it is precisely the floor and ceiling bounce (reflections) that make the effective array so long. Because the listener is at a listening distance small compared to the (effective) length of the array he is said to be in the near-field.

    The "focus" you describe is probably a reference to the narrow beam width that arrays exhibit in the FAR-field (distances large compared to the array length). This thinking applies to concert line arrays which are designed for far-field use. The MCLA does not behave this way because you listen to it in the NEAR-field where the sound field does not change with listening height. There is much confusion in casual speaker discussions about this very important distinction between how line arrays perform in the near-field versus far-field. The two situations are quite different and it is important to understand the distinction. Much of the analysis that applies to concert line arrays does not apply to line arrays in small rooms. Concert lines are almost always heard in the far-field. Small room line arrays have the potential to create infinite line sources if they are used in a room with parallel ceiling and floor and the array covers essentially the full floor to ceiling height. With the infinite line array the listener is fully immersed in the near-field of the array. This is when the acoustic magic happens.

    With most point-source multi-way loudspeakers there is an audible change in sound with a casual sit-down/stand-up test. I have observed that in a casual sit-down/stand-up test the sound of the array is completely unchanged...as expected. The behavior of the MCLA array is essentially ideal with respect to vertical directivity. However, the horizontal directivity is precisely that of a 2.5" piston. Many people would consider this to be too large for use up to 20 kHz but with corner placement the listening angle is automatically restricted to +/- 45 degrees which allows the 2.5" piston to illuminate the complete listening area very nicely...even in the top octaves. If I listen carefully as I move from the listening area forward to the front wall I can hear the highs fall as I approach the wall. If you think about it, the arrays probably maintain a better response near the front wall than any point source speaker placed away from the walls because you would be about 180 degrees off-axis for the point source speaker at the front wall but only 45 degrees off-axis from the corner line array. The geometry nicely compensates the largish diameter of the driver regarding high frequency dispersion.



    Regards,

    John
    Hello and thanks for the feedback.

    Yes, I have a lot of understanding to catch up with in this field, and that is a part of the fun, I think, to try to fully understand why the system is working the way it is.

    Is it fair to say that there could be a problem with the doppler distortion, using the same driver in the whole range? Is that the main trade-off with the liberty from XO phenomena?

    Mind you, I understand that there are more on the up-side with this system.

    A detail from your material on the system, John. I cannot track the applied EQ in appendix 1 to the measurements in fig 5-7. Perhaps the process of coming to the EQ is a iterative process and not just a measure-and-adjust??

    Regards//lasse

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)


    The Behringer DCX2496 is a fine crossover but it may not offer enough EQ flexibility to correct the 3 dB slope of an array. If it is an existing EQ you could always try it out before getting the DEQ2496 which has the real EQ power you need for line array projects.

    Yes, it is precisely the floor and ceiling bounce (reflections) that make the effective array so long. Because the listener is at a listening distance small compared to the (effective) length of the array he is said to be in the near-field.

    The "focus" you describe is probably a reference to the narrow beam width that arrays exhibit in the FAR-field (distances large compared to the array length). This thinking applies to concert line arrays which are designed for far-field use. The MCLA does not behave this way because you listen to it in the NEAR-field where the sound field does not change with listening height. There is much confusion in casual speaker discussions about this very important distinction between how line arrays perform in the near-field versus far-field. The two situations are quite different and it is important to understand the distinction. Much of the analysis that applies to concert line arrays does not apply to line arrays in small rooms. Concert lines are almost always heard in the far-field. Small room line arrays have the potential to create infinite line sources if they are used in a room with parallel ceiling and floor and the array covers essentially the full floor to ceiling height. With the infinite line array the listener is fully immersed in the near-field of the array. This is when the acoustic magic happens.

    With most point-source multi-way loudspeakers there is an audible change in sound with a casual sit-down/stand-up test. I have observed that in a casual sit-down/stand-up test the sound of the array is completely unchanged...as expected. The behavior of the MCLA array is essentially ideal with respect to vertical directivity. However, the horizontal directivity is precisely that of a 2.5" piston. Many people would consider this to be too large for use up to 20 kHz but with corner placement the listening angle is automatically restricted to +/- 45 degrees which allows the 2.5" piston to illuminate the complete listening area very nicely...even in the top octaves. If I listen carefully as I move from the listening area forward to the front wall I can hear the highs fall as I approach the wall. If you think about it, the arrays probably maintain a better response near the front wall than any point source speaker placed away from the walls because you would be about 180 degrees off-axis for the point source speaker at the front wall but only 45 degrees off-axis from the corner line array. The geometry nicely compensates the largish diameter of the driver regarding high frequency dispersion.


    Hey Chromedome2000,

    I like your suggestion of just a pre cut baffle. I'll mention this to my potential source and see if we can get at least a pre cut baffle offering. So far it is still just loose talk...

    Regards,

    John

    Leave a comment:


  • Sydney
    replied
    Re: Murphy Corner Line Array (MCLA)

    and thus limiting the bounce effects from ceiling and floor.
    Not necessarily; some arrays are designed to use floor/ceiling ( boundary reflection ) to become a virtual extension of the real line.
    Some are amplitude shaded depending upon whether being free flown or boundary loaded.

    Leave a comment:


  • lasse
    replied

    Leave a comment:


  • EricTheBlue
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by Chromedome2000 View Post
    I too would be interested in a cabinet kit. However, as I posted earlier, I would have to place them a fair distance from any corners. So, if possible, an out of corner cabinet kit would be appreciated. I realize EQ would have to be done on an individual basis but a kit would be nice to get started on a set of these speakers. If an entire kit is out of the realm of possibility, just a precut baffle would truly be appreciated as this would be the most difficult part to fabricate. Keep the info flowing.
    +1: I suspect many (myself included) who will want to build this kind of speaker will not have symmetrical corners available, and even if they did, may prefer traditional off-rear-wall placement. With this though in mind I have a few suggestions:

    Develop at minimum two basic enclosure types: One with the size and shape of the original corner loaded, 25 driver array, and a more traditional infinite baffle design approximately 6 feet tall using 16 drivers. It is understood that the infinite baffle version will likely not have much extension below 80 hz but that's what subs are for.:D Because I've spent more time thinking about the the infinite baffle enclosure than anything else, I have a few more suggestions for it:
    • I recommend an enclosure height of approximately 6 ft. because if the driver placement is right (see next bullet), owners should hear a more or less identical tonal balance when seated or standing.
    • The bottom driver of sixteen should be place approximately 1 foot above the ground for a few reasons. For starters, doing so fulfills the previous item because 16 ND90 drivers should form an array approximately 5 feet tall. Second, when seated, no one is going to be listening to drivers within a foot of the floor so it makes more sense to get the bottom driver closer to ear height so the entire driver array can be taller. Third, when you raise the height of the driver array closer to the ceiling the listener will get the benefit (IMO-it's a big part of the reason why I prefer tall arrays) of a tall sonic soundstage and images when seated. I know this to be true from owning AV123's LS9 array up to a year ago. Finally, though I wouldn't necessarily recommend this for the first generation of enclosures, if one inserted a solid horizontal wall within the enclosure just below the bottom driver, the enclosure would essentially be split in two. The upper chamber would hold the array drivers, and a lower one could incorporate a shallow depth, side firing woofer (8-12 inches assuming the enclosure is deep enough) to allow for a close to-if not full range-speaker via external crossovers and bi-amping.
    • Make the enclosure as narrow across the front as possible. Given the diameter of the ND90, I would think the enclosure need not be more than 6 inches wide. Having a tall skinny enclosure offers three benefits: Better SAF, a design that can be used in smaller rooms because the speaker isn't in the owner's face physically, and a speaker that disappears better than a typical tall, wide line source like Magnepan's larger planars. The enclosure can be as deep as necessary within reasonable limits (12-14 inches?).
    • Brace the internal enclosure well.
    • Optional but recommended-include internal damping and absorbing material.
    • Ensure the front baffle can be user removed for driver installation and repair as necessary.

    Leave a comment:


  • russ_L
    replied
    Murphy Corner Line Array (MCLA) Enclousure Kit

    Originally posted by John L. Murphy View Post
    Hi John,

    The front panels were definitely a pain to make...especially the cutouts for the 25 drivers. I am in discussions with a supplier to offer an enclosure kit and will announce any progress toward that offering right here. Any readers who might be interested in an enclosure kit should let us know by commenting here.
    Hi John- I've been following this thread since its beginning. I'm most interested in your MCLA as it should adapt very nicely into my 13'x22'x7'3" basement home theater. The room is currently being built, but is a year behind schedule (life always seems to get in the way of things).

    In that regard, I'd be interested in two enclosure kits, but perhaps not at the moment. I hoping in the interim that you might work out a center channel solution.:D

    Regards,

    Russ

    Leave a comment:


  • Chromedome2000
    replied
    Re: Murphy Corner Line Array (MCLA)

    I too would be interested in a cabinet kit. However, as I posted earlier, I would have to place them a fair distance from any corners. So, if possible, an out of corner cabinet kit would be appreciated. I realize EQ would have to be done on an individual basis but a kit would be nice to get started on a set of these speakers. If an entire kit is out of the realm of possibility, just a precut baffle would truly be appreciated as this would be the most difficult part to fabricate. Keep the info flowing.

    Leave a comment:


  • acousticspeaker
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by John L. Murphy View Post
    Hi John,

    Yes, I would expect the arrays to sound better at 30' than the point sources. I like to crank mine to an extreme level in the music room and then step into the adjacent kitchen and enjoy the music while I make pizza from scratch. I've had occasion to cover my ears and turn it up to the threshold of clipping and then step out of the room to evaluate the sound quality. From the next room I could hear that there was no audible distortion even at levels that were so high I could not comfortable stay in the same room with the speakers without guarding my ears. At these levels and with a little EQ tweak (more bass typically) they can provide a fair illusion of a live band in the next room. (If you could ever believe Fleetwood Mac was really performing in the next room!) But they can reach those kinds of level comfortably with just my small amp with no signs of stress.

    Have you ever had a loud party where people wanted to dance but because of the loud crowd you could barely hear your stereo when you cranked it up to clipping and beyond? I have. How embarrassing. That will never happen with the MCLAs. They have enough output to totally dominate any loud party that might unfold at your place. But truly powerful dynamics are just one facet of the outstanding performance of these speakers.

    I have a design completed for the all-analog EQ with voicing options but have not completed a circuit board layout yet. That will happen as time allows.

    The front panels were definitely a pain to make...especially the cutouts for the 25 drivers. I am in discussions with a supplier to offer an enclosure kit and will announce any progress toward that offering right here. Any readers who might be interested in an enclosure kit should let us know by commenting here.

    Regards,

    John
    John - I would definitely be interested in an enclosure kit. The enclosure is what is holding me back from building your speaker. It's not like I have to build a pair tomorrow so I look forward to progress in your discussions.
    p.s. I didn't mean to turn this forum into a discussion of Allison speakers - they were my alternate choice - but I am going to hold off for now.

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by acousticspeaker View Post
    Thanks for reply, John.

    The Allison Ones, although not meant for the corners, were another consideration of mine, as they would be backed up to the wall. However, I don't know how they would work on an 11' wide wall without getting to close to the sidewalls. The Allison IC20s, although no longer available, did have a small line array of MTTM on each panel to supposedly help with the floor ceiling reflections you spoke of - but I don't see how just adding one more tweeter and midrange on each panel would help that much. The "room" that my speakers would be in is about 11' x 18' - but the other 11' end is really a half height entryway wall with a 3' opening in the middle. On the other side of the entryway is the kitchen. So one could actually be on the far wall of the kitchen, some 30' away from the speakers, and clearly see at least the top half of the speakers - the halfwall would block the view of the bottom half. In other words, people could be listening to music some 30' away. I would then think that your line array would have an advantage over the Allisons. In your earlier posts, you had talked about designing your own equalizer with some preset hardwired settings. Are you still considering doing that? If yes, would you be able to switch between some different EQ curves depending on the music?
    Finally, has anyone come forward to offer to fabricate (for a price of course) the front panel of your MCLA? It appears making all of the routered holes is the most difficult part of the project for the builder.

    John

    Hi John,

    Yes, I would expect the arrays to sound better at 30' than the point sources. I like to crank mine to an extreme level in the music room and then step into the adjacent kitchen and enjoy the music while I make pizza from scratch. I've had occasion to cover my ears and turn it up to the threshold of clipping and then step out of the room to evaluate the sound quality. From the next room I could hear that there was no audible distortion even at levels that were so high I could not comfortable stay in the same room with the speakers without guarding my ears. At these levels and with a little EQ tweak (more bass typically) they can provide a fair illusion of a live band in the next room. (If you could ever believe Fleetwood Mac was really performing in the next room!) But they can reach those kinds of level comfortably with just my small amp with no signs of stress.

    Have you ever had a loud party where people wanted to dance but because of the loud crowd you could barely hear your stereo when you cranked it up to clipping and beyond? I have. How embarrassing. That will never happen with the MCLAs. They have enough output to totally dominate any loud party that might unfold at your place. But truly powerful dynamics are just one facet of the outstanding performance of these speakers.

    I have a design completed for the all-analog EQ with voicing options but have not completed a circuit board layout yet. That will happen as time allows.

    The front panels were definitely a pain to make...especially the cutouts for the 25 drivers. I am in discussions with a supplier to offer an enclosure kit and will announce any progress toward that offering right here. Any readers who might be interested in an enclosure kit should let us know by commenting here.

    Regards,

    John

    Leave a comment:


  • acousticspeaker
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by John L. Murphy View Post
    Hi John,

    The Allison Threes, as you note, are one of the few speakers designed for corner placement. You can imagine the top view of the speaker with its three corner reflections and see that it is a good configuration compared to placing the same point source speaker away from the walls. A point source corner speaker could be a good fit for your room. While the point source in the corner would bring the front wall and side wall reflections together in a controlled way that group would not be particularly well integrated with the ceiling and floor reflections. Also the point sources would not have the slow falloff with distance that you get with the arrays. I think this slow change in level with distance is responsible for the "walk around image" effect that people talk about with line arrays. The image of the performers across the soundstage is nicely consistent as you walk about the room. I guess it largely depends on whether you are interested in a speaker building project or want something ready-made. If you play a wide variety of music the arrays will offer the advantage of variable voicing (via the EQ) where you can use a flat response for the latest reference recordings or have a more traditional voicing for older recordings so that they sound good also. Keep an X-Curve voicing at the ready for movie playback.

    If you do decide to build the arrays please report on your progress and results.

    Regards,

    John
    Thanks for reply, John.

    The Allison Ones, although not meant for the corners, were another consideration of mine, as they would be backed up to the wall. However, I don't know how they would work on an 11' wide wall without getting to close to the sidewalls. The Allison IC20s, although no longer available, did have a small line array of MTTM on each panel to supposedly help with the floor ceiling reflections you spoke of - but I don't see how just adding one more tweeter and midrange on each panel would help that much. The "room" that my speakers would be in is about 11' x 18' - but the other 11' end is really a half height entryway wall with a 3' opening in the middle. On the other side of the entryway is the kitchen. So one could actually be on the far wall of the kitchen, some 30' away from the speakers, and clearly see at least the top half of the speakers - the halfwall would block the view of the bottom half. In other words, people could be listening to music some 30' away. I would then think that your line array would have an advantage over the Allisons. In your earlier posts, you had talked about designing your own equalizer with some preset hardwired settings. Are you still considering doing that? If yes, would you be able to switch between some different EQ curves depending on the music?
    Finally, has anyone come forward to offer to fabricate (for a price of course) the front panel of your MCLA? It appears making all of the routered holes is the most difficult part of the project for the builder.

    John
    Last edited by acousticspeaker; 03-21-2011, 04:15 PM. Reason: correction

    Leave a comment:


  • John L. Murphy
    replied
    Re: Murphy Corner Line Array (MCLA)

    Originally posted by acousticspeaker View Post
    John,

    Glad to see you back answering on this forum. I joined specifically because of what I read about your MCLAs. I think I have an ideal room for some corner speakers - the room is rectangular and the speakers would be placed in the corners on the short wall which is about 11' wide. I was all ready to purchase some Allison Threes which would fit in the corners quite well also. But then, in searching corner speakers, I came across your MCLAs. So now I am torn as to what to do. Tha Allisons would seem to take advantage of many of the corner loading advantages that you speak of - but they are not line arrays - but they are already built, etc. Any comments that you have that would help me would be appreciated greatly.

    Thanks,

    John

    Hi John,

    The Allison Threes, as you note, are one of the few speakers designed for corner placement. You can imagine the top view of the speaker with its three corner reflections and see that it is a good configuration compared to placing the same point source speaker away from the walls. A point source corner speaker could be a good fit for your room. While the point source in the corner would bring the front wall and side wall reflections together in a controlled way that group would not be particularly well integrated with the ceiling and floor reflections. Also the point sources would not have the slow falloff with distance that you get with the arrays. I think this slow change in level with distance is responsible for the "walk around image" effect that people talk about with line arrays. The image of the performers across the soundstage is nicely consistent as you walk about the room. I guess it largely depends on whether you are interested in a speaker building project or want something ready-made. If you play a wide variety of music the arrays will offer the advantage of variable voicing (via the EQ) where you can use a flat response for the latest reference recordings or have a more traditional voicing for older recordings so that they sound good also. Keep an X-Curve voicing at the ready for movie playback.

    If you do decide to build the arrays please report on your progress and results.

    Regards,

    John

    Leave a comment:

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