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Thread: Do you time align your drivers ?

  1. #46
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    Quote Originally Posted by 1audiohack View Post
    I hope not! That would end all our fun.
    I can't type in a hurry, yes I meant Baja 1000.
    The Klipsch review is, in typical Richard Heyser style, very informative, Nyquist plots are so cool. Thanks Grumpy, I didn't have that one.
    As easy as it is to do, I'll bet no one does the two small speaker experiment.
    It is hard to believe how much a couple of inches, or micro seconds of time changes the sound when two drivers are radiating the same sound in close proximity to each other.
    It colors what you hear to a degree that will surprise you.
    Try it,,, I double dog dare you!
    Have a good weekend all,
    Barry.
    Thank you very much Barry for your very kind and interesting advice
    I think that the all issue is very fascinating
    Kind regards,
    gino

  2. #47
    Senior Member 1audiohack's Avatar
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    Say Hi to my bud Vince at VMAR Racing if you see him.
    I have not seen him in some time. Those old cars were cool for sure. The grommet in the top of the Parker Pumper with the label that said "For Fatties" still makes me laugh every time I think about it.



    Perhaps the point to appreciate is that you can only time align in one point is space. Ian
    Well,

    Critics of synchronization often say that full synchronization can only be achieved at a single point in space. What's overlooked is that signal synchronization, when performed at the overlaps between devices, results in the patterns retaining their directional integrity whereas just inches of missynchronization cause the polar responses of both devices to be corrupted.
    The above from Don Davis and Eugene Patronis Jr. Sound System Engineering, Third Edition 2006, page 336.

    Unfortunately other factors come into play that cause the sound stage to collapase other than time alignment such as "how" the power response of the woofer and horn sum at the crossover point. Ian
    Absolutely.

    To be truely time aligned I guess the front baffle would have to be curved to focus the sound on one point......Allan.
    Pass, then you would also be locked in to a fixed listening distance.

    I find some of the most interesting work on the subject is in the array studies by Ralph Heinz of Renkus-Heinz, the Quadratic Throat Waveguide work of Charlie Hughes of Peavey, and the way out front work currently under way by Tom Danley with the Synergy Horn. Those I can't wait to hear!

  3. #48
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    Good Morning from Italy.

    All in all I think it is a pity that the coaxial scheme (I am referring to Altec 604 and similar driver) has been abandoned lately.
    Nevertheless I understand that this old driver keeps a wide group of admirers even today, with technology evolving
    There must be a reson after all ... and I think it could be correlated to its geometry
    By the way I do not know if the time alignment issue was considered in design its crossover
    In a 2 ways coaxial driver with fixed displacement between the the center of emission of the W and the TW, the W can be easily delayed (I suppose) just designing correctly the inductor in series to it ( not sure about this), passively I mean.
    After starting this 3D I look at time response in some speakers review (at Sterophile usually they perform this test)
    A correctly time aligned speaker is usually an exception more than the rule
    Nevertheless I have become a believer in time alignment worthiness
    As usually I do not even try to explain why ... it's a sensation
    Have a nice day
    gino

  4. #49
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by ginetto61 View Post
    All in all I think it is a pity that the coaxial scheme (I am referring to Altec 604 and similar driver) has been abandoned lately.
    The Altecs and Tannoys are not really time aligned since the compression driver is so far behind the woofer. Of course with a simple delay they can be brought into alignment... group delay and all notwithstanding.

    As for a lack of modern coaxial drivers? KEF, Thiel and Pioneer/TAD are all making very good coaxial drivers that are intended to replicate a point source type of sound. All of these are fare more accurate than any vintage design though admittedly they don't have the dynamics or the vintage coloration that some prefer.


    Widget

  5. #50
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    Quote Originally Posted by Mr. Widget View Post
    The Altecs and Tannoys are not really time aligned since the compression driver is so far behind the woofer.
    Depends on where the acoustic center of the horn/c.d. is. Aligning the top plates of the woofer and horn/c.d. doesn't necessarily count.

  6. #51
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by 4313B View Post
    Depends on where the acoustic center of the horn/c.d. is. Aligning the top plates of the woofer and horn/c.d. doesn't necessarily count.
    Agreed, however as I recall they all require a delay on the woofer. They all place the compression driver several inches behind the woofer.


    Widget

  7. #52
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    Agreed, however as I recall they all require a delay on the woofer. They all place the compression driver several inches behind the woofer.


    Widget
    The classic Tannoys, yes. Not the 2558R used in the SRM and SGM 10's and Manley/MasteringLab 10b.

  8. #53
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    Quote Originally Posted by Mr. Widget View Post
    The Altecs and Tannoys are not really time aligned since the compression driver is so far behind the woofer.
    Of course with a simple delay they can be brought into alignment... group delay and all notwithstanding.
    As for a lack of modern coaxial drivers?
    KEF, Thiel and Pioneer/TAD are all making very good coaxial drivers that are intended to replicate a point source type of sound.
    All of these are fare more accurate than any vintage design though admittedly they don't have the dynamics or the vintage coloration that some prefer.
    Widget
    Thank you very much for your reply
    I said this because in this 3D someone states that a woofer first situation in the time response test is less critical than a tweeter first, that usually is the common situation with bookshelf where the tweeter is mounted on the same baffle of the woofer
    Pulling back the tweeter or use a horned one could be an interesting solution, one that I am studying with a great interest
    Basically my point is that this kind of Altec drivers, but I could be wrong, keep a very high fame even today ... there must be something of intrinsically very good in their geometry, at least in some situation, like near field listening
    This near field situation maybe is quite common in European cities where people live in small flat one over the other ... more or less
    Warmest regards,
    gino

  9. #54
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by 4313B View Post
    Depends on where the acoustic center of the horn/c.d. is. Aligning the top plates of the woofer and horn/c.d. doesn't necessarily count.
    Agreed,

    A woofer can be seen as alow pass filter and a horn/driver as a high pass filter. If the drivers have a flat phase response beyond the desired crossover point then the top plate might be near enough.

    The reactive aspect of the driver motor will effect the phase response.
    A horn will also effect the phase response at the low end due to the varying acoustic impediance. It pays therefore not to run your woofer too high or the driver and horn too low but diy peole do it all the same.

    With suitable equipment a phase shift of a driver can be measured however its easier to measure the phase integrity by measuring max cancellation at the crossover point with the drivers out of phase.

    So its reasonable to conclude that aside from physical alignment any phase shift of the drivers in the crossover overlap region is going to upset any attempt at time / phase alignment and the response regularity. Add to this the group delay of certain crossover types and it makes the whole topic far from simple.

  10. #55
    JBL 4645
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    Quote Originally Posted by 1audiohack View Post
    Real quick a couple of easy experiments to try with suprising results.

    The issue at crossover with two drivers emitting the same frequency can be demonstated with the help of a friend, two small speakers like a pair of pro II's and a pink noise generator.

    Drive the speakers at a comfortable level with pink noise, have your friend hold both speakers, one in each hand right next to each other with the sides touching and the front faces even with each other while you listen 10 feet or so away. Have him (or her) slide one speaker forward a few inches then back and observe the changes in what you hear, and let us know. Some say on the alignment issue, if your going to miss, miss big. You will see why.

    The issue with the effects of the room, or some of them.

    While listening in your usual spot, simply cup your hands behind your ears (giving your self Micky Mouse or Dumbo ears) and note the difference when your not hearing as much of the back of the room. When you do that out doors (like if you have a patio system) the sound does not change that much, in most "living rooms" the change is , well,,, try it. You might end up with a thick fiberglass pillow for you listening pleasure.

    I have a pair of Altc 604 8-G's that I haven't listened to in some time and do have the desire to set them back up and get active with them. My real job and life just keep getting in the way.

    Best,
    Barry.
    Now that seems make sense.

    I have time alignment delay on the Behringer DCX2496 for my modified JBL control 5 that have had the passive crossover disabled and the DCX2496 takes over for the rest of their function.

    I have tinkered around with the delay to get the best possible sound right down to crazy wild dialogue panning shifts over the matching LCR.

    Also if, one of the speakers (left and right has mismatched frequency too much or too less of the other) then its going to sound misbalanced. The centre phantom will be off my so much db and you’ll find yourself sitting in an awkward listening position.


    Quote Originally Posted by jcrobso View Post
    Time or phase alignment sounds very good if you can do it correctly, but alas it is not easy to do. Aligning the voice coils may not be the only problem, don't forget about phase delays caused by the crossover. There are many things to consider, without the necessary test gear you will just be using the SWAG* method.


    *Scientific Wild Ass Guess.

    Now that was funny SWAG!

    What about real life then? How is that aligned in terms of time delay I’m just curious?

  11. #56
    Senior Member jblsound's Avatar
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    While listening in your usual spot, simply cup your hands behind your ears (giving your self Micky Mouse or Dumbo ears) and note the difference when your not hearing as much of the back of the room. When you do that out doors (like if you have a patio system) the sound does not change that much, in most "living rooms" the change is , well,,, try it. You might end up with a thick fiberglass pillow for you listening pleasure.
    I don't know that's right. I've held my hands behind my ears and the difference is I hear more of the high end, as those frequencies are more directional.
    I don't see that the back wall is the difference, as I sit in fairly high back seats with no full walls directly behind the seat (a large 8'-8" x 7'-0" archway centered on the room's centerline). And with another archway 12 ft behind the first. So any full walls, directly behind the seats are about 35 ft behind the seat.
    Living in the Land of the Sun

  12. #57
    JBL 4645
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    Even holding your hands next to ears and moving them in and out from distance of 4” makes for phasy like sound as the pressure changes on the ear.

  13. #58
    Senior Member duaneage's Avatar
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    I've built systems where the drivers ended up in close time alignment and others where they were seriously off. Most alignment errors can be compensated and corrected in the crossover but it's a tedious task. The closer the drivers are to each other on the baffle, and the nearer the voice coils are in the baffle plane the easier it will be.

    Plenty of great systems had poor time alignment to begin with. Tannoy concentric drivers have near perfect time alignment but that doesn't make them perfect speakers for some people. A single full range driver, while limited in range , offers natural time alignment as well.

    Headphones have perfect TA and can be a good reference. They eliminate the room and outside influences, although the coloration is a matter of preference.
    Why buy used when you can build your own?

  14. #59
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    Quote Originally Posted by duaneage View Post
    I've built systems where the drivers ended up in close time alignment and others where they were seriously off.
    Most alignment errors can be compensated and corrected in the crossover but it's a tedious task.
    The closer the drivers are to each other on the baffle, and the nearer the voice coils are in the baffle plane the easier it will be.
    Plenty of great systems had poor time alignment to begin with.
    Tannoy concentric drivers have near perfect time alignment but that doesn't make them perfect speakers for some people.
    A single full range driver, while limited in range , offers natural time alignment as well.
    Headphones have perfect TA and can be a good reference. They eliminate the room and outside influences, although the coloration is a matter of preference.
    Thank you very much for your reply, very interesting
    Your point that plenty of great systems had poor TA put a serious question mark on the importance of this property
    At Stereophile they perform the TA test and TA speakers are the exception more than the rule.
    Nevertheless, as you state, this speakers get very good reviews-
    On principle TA seems a nice and "right" property
    I have a pair of old but nice Tannoy DC100 sporting a coaxial of 8"
    I have also a Behringer cx3400 electronic xover that allows a time delay of up to 2ms on the low output
    My idea would be to do some test, when I will find the time
    Maybe even with only a mono signal on one channel only, changin the delay on the woofer.
    It would be very interesting to hear from coaxial speakers Owners like Altec or Tannoy if they have any experience in this regard.

    Thanks again and have a nice day !
    gino

  15. #60
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    Quote Originally Posted by duaneage View Post
    Headphones have perfect TA and can be a good reference. They eliminate the room and outside influences, although the coloration is a matter of preference.
    I agree with headphones but I don’t care to use them but I do agree since the audio isn’t going to be disrupted by objects that stand in its path. Its good sense to listen on headphones then go back to the loudspeakers and see what is missing in terms of sound imaging detail that makes up for the sound stage.

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