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Time aligning bass tapped horn

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    Posted: 18 April 2017 at 4:20pm
As the title says does anyone have any experience of integrating tapped horn subs with the rest of their rig .
I would like to try out something like a Tham 15 but how does one go about making sure its aligned correctly?
 With a box like a folded horn it seems easy because theres just the distance from the driver to the mouth to dial into the crossover to get things roughly right but with a tapped horn you have a driver sitting in the mouth of the horn, sometimes facing down the horn with the magnet visible so two 'path lengths' to deal with?
Is there a rule of thumb to get these type of boxes singing? Ive had a look around the net but I cant find much info.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 5:02pm
If you're using horn length / distance to driver, you are not aligned. Remotely.

You align a tapped horn the same as any other system, using dual channel FFT and adjusting crossover filters, EQ, and delay until the phase traces overlap within 30 degrees for one octave either side of acoustic crossover point.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rags Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2017 at 6:02pm
Thanks for the reply toasty ..is there a guide or thread that explains how to do what you say ?

In the past I've used horn length to approximate the
delay and then played around with a signal at xover freq to get min spl with out of phase drivers...is this wrong?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2017 at 8:46pm
For what it's worth, I did spend a lot of time fiddling with delay settings over the years with some SS15 tapped horns. I think I started with hornresp - group delay at the crossover point (120Hz to some 12" BR in this case). Then inverted phase, signal at xover point, then tweaks while out playing until the kick through the crossover sounded best. I can't remember exactly what it was, not that much though...less than HR suggested. 4.5ms seems about right. One day I'll get around to measuring them...love the sound though, 4 can belt it out. Not heard the Cubos... 

*edit* or tham15s either...


Edited by carlosdelondres - 20 April 2017 at 8:46pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rags Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2017 at 1:26pm
Thanks Carlos thats interesting what you discovered.
So this suggestion from toasty (Thank you)
<< using dual channel FFT and adjusting crossover filters, EQ, and delay until the phase traces overlap within 30 degrees for one octave either side of acoustic crossover point >> had me doing a lot of reading . I have a mic and a mixer (for preamp) plus external soundcard and am slowly working my way through REW in my spare time.( I was never any good at maths and graphs put the wind up me so I have to read everything a dozen times before it even starts to make some sort of sense )
So there seems to be several bits of software that will give me graphs of phase so I can compare and adjust but REW  seems to have masses of information on different forums to do with setting up, calibration etc so I thought I would work my way through this to get my head around the principals. 
I know it initially seems more to do with mains and subs and room response for home theater but I hope to be able to get my kicks and subs working together to start off with.
My question now is am I going round the houses a bit with REW when I could be using another bit of sw that is more suited to the job or easier or more accurate ?
Thank for your patience
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2017 at 6:30pm
I've always used ARTA which is shareware. www.artalabs.hr
You just need something that can read an accurate phase trace in 2-channel mode, save/print it on the screen and then overlay a live reading from the mic. You then adjust various things while the pink noise plays, and you watch the screen to see how what you're doing is affecting the live trace compared to the saved trace. The important thing is to set the measurement delay compensation (distance between mic and system) accurately, once, and then NOT move the mic at all during the rest of the process. So you want to do this outside, or in a relatively large space so the mic can easily be in a position where all the bands are summed nicely. 3 metres or more is a good distance. 

Adding delay to the driver you're measuring will move its trace backwards relative to the saved one, but not change the slope, so delay on its own is not enough if the trace is not already at approximately the right slope. 
You would adjust the electrical crossover frequency and slope to get the phase trace to the right kind of shape, then use delay to line it up with the other driver. You might find that actually what you need to adjust is the driver that produced the saved trace, at which point you would go back to step 1 and repeat.
And if you have to use PEQ points on a particular driver, those should be in place before you start aligning so that their effect on the phase can be taken into account. 
Of course, you may well find that you want to change the PEQ once the time alignment is done - especially if it was near the crossover point - so this can become an iterative process. After a few runs through, you should arrive at a nicely aligned and EQ'd system.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rags Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2017 at 7:23pm
I'll have a look at that thanks 54
If the weather is OK this weekend I have the opportunity to throw my stack up in a mates field....I'm just trying to be ready to take a whole bunch of readings so even if I don't get to make final adjustments I will at least have a load of info that I can sit down and go through to see what's happening around xover points and be able to make intelligent adjustments next time I turn on .
Ta   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2017 at 10:10pm
Originally posted by studio45 studio45 wrote:

Adding delay to the driver you're measuring will move its trace backwards relative to the saved one, but not change the slope, so delay on its own is not enough if the trace is not already at approximately the right slope.


Hmm not true I'm afraid. Adding delay moves the trace but it also changes how steep the slope is. You delay the part of the system with the gentlest slope. Slope direction will depend on whether the frequency is ahead or behind in time to the reference point.

You can see what adding delay does to a pure slope here, a real driver measurement will unfortunately be much less clean:
https://www.youtube.com/watch?v=ebaZXV_PdsM

Edited by toastyghost - 24 April 2017 at 10:11pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2017 at 4:44pm
You're right, I'd never really noticed that - for a real driver that already gives a complicated trace, the movement aspect is more obvious than the change of slope. I guess I've just been using relatively small corrections and not realised it was happening. Every day's a school day ;)
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