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HD15 Time Alignment

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loophole View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote loophole Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 4:50pm
so rather than general sluggishness in responding to a signal, there is just a bottle neck somewhere in the system which holds it all back. and presumably this is the speaker rather than the amplifier we are talking about here... what exactly causes this effect and how can it be calculated?
thanks for the help mate, good to learn new stuff ;)
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Andrew View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 5:05pm
I seem to remember Rog did a very good explanation of group delay, like in reflex cabinets, and that band-pass cabinets were even worse.  Can you jog our memories?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 5:18pm

Of course I'm only talking about the speaker/box itself. An amplifier has a group delay that is so tiny it's really a waste of time talking about it. Other things that will introduce additional group delay are crossovers, no matter if they are actve, passive or digital....

The groupdelay with boxes can't be calculated that easy. Some simulation programs can calculate them (like WinISD for closed, vented and bandpass enclosures) but those calculations don't take the rooms in account. All values are for a 4pi enviroment, so no reflective surface at all.

After taking a long, close look at speaker/boxes group delay I can guess the group delay of a speaker when I know some other specs. But that guess is not necessarily right.... If it's crucial to the job I measure it.... for smaller events I use the Behringer UltraDrive. With the measurement mic it can measure and set the necessary delays by itself and it works pretty good..... Of course this measurement takes EVERYTHING in the signal chain into account: The crossover, the output EQs (yes, EQs introduce delay too!), the DA-converters, the speakers, the enclosures, the room up to the place where the mic stands....

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Dave Slater View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave Slater Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 5:40pm

check out smaart live and their tutorials

you can use it for 30days for free and it should give you the results you need

 

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norty303 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 5:47pm

JD01 - I've got an Ultradrive and I know that my bandpass sub will need some delay correction even when distance aligned but the manual instructions on how to auto set this up is sketchy to say the least.

Don't suppose you could give some quick pointers?   Is it just a case of plugging a mic (any type? would a 57 do?) into one of the inputs then running the setup tones at a certain mic distance?

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Andrew View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 9:36pm
Best go for a nice flat condenser mic.  The Behringer reference one only goes for a few tenners these days, half the price of the 57.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote norty303 Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 10:28pm
Does it need to go into a desk with phantom power or is the ultradrive able to take the mic directly?
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roborg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 07 September 2004 at 11:23pm
Originally posted by dave dave wrote:

check out smaart live and their tutorials


<FONT face=Arial>you can use it for 30days for free and it should give you the results you need


<FONT face=Arial> 


<FONT face=Arial>



assuming the group delay is less than 30 days
What I cannot create, I do not understand
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2004 at 5:58am

Originally posted by roborg roborg wrote:

assuming the group delay is less than 30 days

Which I question with some bp subs like the d&b B2. It seems to take several years to get a tone out of it....

@ norty303: The UltraDrive gives phantom power when in measurement mode, so a condenser can be plugged in directly.

You go to the auto align feature and select what values you want to align, like short delay and polarity. Then you press ok and selct the outputs you want to align. It would be ok to align only one side if both sides are set up identical. then you press ok again and now you can set the measurement tone volume by turning the knob. You should set it so it won't show the red LEDs at input c but all the others (or at least as much as possible). Now you press ok again and it will measure. Done. Just check that the values aren't insane. The device CAN be tricked..... but it  works in most cases and if not placing the mic somewhere else would work....

The distance should be at least the height of the stack to measure or if the tops are flown the hanging height of the tops. As I said if the values don't seem to be correct just place the mic 1m further away and some 10 centimeters to the left or right. Just don't put the mic near a wall or near the floor or the ceiling. It should be at ear height... 1,70m or such.... makes no sense to measure the correct distance for places where noone will be....

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