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Thread: Simple Time Align ?

  1. #1
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    Simple Time Align ?

    I run an active 4 way system using Ashley 4001 and there 31 channel Eq but want to time align the speakers. I can do two physically but not the Urei coax unit and horn loaded bass.
    Is there a simple stand alone unit that would do this without all the hassle and complexity of going digital?

    Dave

  2. #2
    J.A.F.S.
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    All pass filter

    There are many analog active crossovers that feature "all-pass" filters that allow user selectable time delays. Even some of the el-cheapo units like Behringer have that feature.
    Amazed I'm still alive!
    Tim

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    Anything that would give the same quality as the ashley?


    Dave

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    Keep your eye on ebay for Brook Siren crossovers. Easy to change frequencies, time alignment and they can also adjust the phase at the crossover point. They also have built in limiting as well.

    Allan.

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    Super Moderator yggdrasil's Avatar
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    I have been looking into all-pass filter for time delay, and I simply cannot understand that it will work as intended.

    It is my understanding that an all-pass filter shifts phase, and a phase shift will give different time delay at different frequencies. To me that means that the all-pass filter will delay a 20KHz half as much as a 10KHz tone, and the delay will be 1/10 compared to a 2KHz tone.

    Don't know if this makes any sense, or if it is correct understanding of the all-pass filter. If it is wrong, please try to educate me!

    Johnny

  6. #6
    Senior Member grumpy's Avatar
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    if the phase shift were able to be fixed at one value, then yes, one would
    see a linear relationship between frequency and delay. If the all-pass filter
    is designed to have a linear relationship between frequency and phase shift,
    then the delay can made to be constant (over a reasonable frequency bandwidth).

    One described fully-passive example (many other topologies exist
    including active [still analog]):

    http://en.wikipedia.org/wiki/Bridged_T_delay_equaliser

    Note in the article that 33uS of delay is accomplished with one such filter stage
    when a 15kHz bandwidth is required. More delay can be introduced (per stage)
    if the maximum frequency is reduced (such as in a low pass filtered crossover).

  7. #7
    Senior Member 1audiohack's Avatar
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    In short you only get up to one rotation or up to one wave length of delay per all-pass stage right? One would first have to determine if that would even be useful.

    Charlie Hughes has a couple of good papers on all-pass uses including the demystifying of all-pass crossovers on his Excelsior Audio website, look in the publications pages, when I get near a computer I will post a link.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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    In the late 70's and early 80's everyone was hell bent on time alignment. All very nice doing so but after the various frequencies propogate, they will be further and further out of phase. They sure start off in phase but after that it becomes abig jumble. IMO spend your money on some improvements that you can hear.

    Allan.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Allanvh5150 View Post
    In the late 70's and early 80's everyone was hell bent on time alignment. All very nice doing so but after the various frequencies propogate, they will be further and further out of phase. They sure start off in phase but after that it becomes abig jumble. IMO spend your money on some improvements that you can hear.
    I agree 100%.

    I would put it in a slightly different way though: After you have addressed everything else, experiment with time alignment. The effects are both measurable and audible, however improving the system with time alignment isn't plain or simple.


    Widget

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    Well I suppose Ive solved my own problem. Im running a 4 way system using A Heil tweeter crossing at 5000hz down to a JBL 2344 bi-radial horn down 1.2hz to a Urei 801 (its the stunning mid unit out of my 813Bs) down to 1850 horn loaded bass 120hz. All run through an Ashley 4001 analogue active crossover with 4 Musical Fidelity amps.
    Everything but the 1850 horn is moveable and it is just incredible the difference speaker placement makes. I have spent many days trying things in different configurations and in the end have ended up with everything stacked vertically on top of the horn lying on its side except for the Heil tweeter which is alongside the JBL 2344. So everything is aligned vertically but the Heil tweeter and of course I have aligned the speakers as near as possible to get the voice coils in line. When its right the sound becomes quite ethereal with the speakers just disappearing. Time align does matter. I think there is a lot of confusion mixing time align and phase shift my understsnding is they are not the same.
    Dave

  11. #11
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by David Ketley View Post
    When its right the sound becomes quite ethereal with the speakers just disappearing. Time align does matter. I think there is a lot of confusion mixing time align and phase shift my understsnding is they are not the same.
    I am glad that you got a sound that is working for you... I'd love to hear it and I bet it sounds great, but I doubt that if you measured the impulse response that you would have anything close to the singular pulse of an actually time aligned speaker system.

    I am not suggesting that you are wrong about what does or does not sound good, but based on my experience, getting a four way to be actually time aligned and not using test equipment and DSP to get it there is a near impossibility. I would suggest that you consider making your next system upgrade in your crossover. I have used the Ashly and it is good, but if you are going to this level of care, you would very likely hear the improvements in using a Marchand or one of the other really great crossovers.


    Widget

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    Iím sure your right Wigit I was reading somewhere its possible to get near to perfect using a signal generator at the crossover points and checking the response and moving the speakers . I donít have access to test equipment but brought the Ashley crossover as one highly thought of by the Forum but we always seem to be trying to hit a moving target in this obsession with music!
    Is the Marchand analogue or digital? Im really trying to keep things as simple as possible
    using the Heil tweeter allowed me to get the EQ out of the signal path I was trying various JBL horns with EQ but the Heil just sounds right.

    Dave

  13. #13
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by David Ketley View Post
    ...the Ashley crossover as one highly thought of by the Forum but we always seem to be trying to hit a moving target in this obsession with music!
    I bought and used the Ashly several years ago but as I tried better equipment I felt the need to change it out of the system. I am sure some people do play follow the leader, believe the latest reviews and itch to get something newer and "better". For me it is always a matter of what sounds better. I have been lucky enough to be in a position to borrow a lot of gear and I have found that at a certain level cost and how new something is do not always correlate to better sound. I have a fairly pedestrian system, but I think it sounds pretty darned good and the core hasn't changed in a few years, the speakers came along last year and have settled in nicely. I am currently looking for the right preamp. (The right preamp is the most transparent one I can afford. )

    Quote Originally Posted by David Ketley View Post
    Is the Marchand analogue or digital? Im really trying to keep things as simple as possible...
    Marchand makes quite a few different models. I believe they are all analog. I really like their top tube model.

    I agree, no EQ is the best EQ... but your system and room need to cooperate. I haven't used an EQ in quite a few years. I do still have a pair of Whites in storage, but I'd only bring them out if I decided to revisit a 43XX system.

    Widget

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    I try and keep the signal path as simple as possible I use a SPL 2602 Volume 2 Volume control after the DAC to the Ashley and direct to the power amps. Its a surprise to most people that a volume control can be an relatively expensive piece of equipment and itself can have a profound influence on the sound.



    Now I have got the speakers to my liking Iím looking at the signal going in after all rubbish in rubbish out!


    Dave

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    Senior Member richluvsound's Avatar
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    Deqx

    David,

    not such a bad idea for what your trying to do . You are getting pre-DAC , crossover , etc.etc in one box. It is hard work at first , but you do learn fast . If I can get my head around it ,anyone can .

    Rich

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