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Author Topic: 3TX goes active  (Read 1923 times)

Mark Wilkinson

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Re: 3TX goes active
« Reply #10 on: August 30, 2017, 09:02:34 am »

Hi Mark,
The Lake does have both 1st and 2nd order all-pass.
On 1st order only the frequency of the filter can be changed.
On 2nd order both frequency and bandwidth can be changed.
I don't believe there is a way to invert the filter although that would be handy as you said.
Hope that helps. Peter can contribute way more to this than I can.
Don

Hi Don, Thanks.   
I finally found the all-pass filters in the Designer Manual....there sure is a ton of literature for those Lakes.
I learn a lot from manuals...especially from gear i can't afford !
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Peter Morris

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Re: 3TX goes active
« Reply #11 on: August 30, 2017, 10:50:22 pm »

Hi Mark,
The Lake does have both 1st and 2nd order all-pass.
On 1st order only the frequency of the filter can be changed.
On 2nd order both frequency and bandwidth can be changed.
I don't believe there is a way to invert the filter although that would be handy as you said.
Hope that helps. Peter can contribute way more to this than I can.
Don

With the Lake there is no invert all-pass, the trick is to use of combination of delay and all-pass filters to get what you want ... its tricky
« Last Edit: September 08, 2017, 06:42:59 am by Peter Morris »
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Timo Beckman

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Re: 3TX goes active
« Reply #12 on: September 03, 2017, 02:02:29 pm »

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Mark Wilkinson

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Re: 3TX goes active
« Reply #13 on: September 03, 2017, 07:27:05 pm »

There is no invert all-pass, the trick is to use of combination of delay and all-pass filters to get what you want ... its tricky

Hi Peter,  I can invert all-pass with rePhase and FIR...it's really cool, and seems to be a very elegant way to correct the lower freq end / downward sloping phase end, of driver correction.
But alas, inverted via FIR brings the same old latency problem. 
And the only reason I'm even looking at all-pass is to use IIR to reduce latency.....soooo
Gotta study tricky :)
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Mark Wilkinson

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Re: 3TX goes active
« Reply #14 on: September 03, 2017, 07:28:16 pm »

Tricky it is for the first couple of times.....

https://timobeckmangeluid.wordpress.com/2016/10/24/once-upon-a-time/

Hi Timo,  thanks...will give a hard look.
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Timo Beckman

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Re: 3TX goes active
« Reply #15 on: September 04, 2017, 04:00:24 pm »

Hi Timo,  thanks...will give a hard look.

Good luck ;-)

It took me a while before i wasn't guessing anymore but it's not that hard If you know what to look for.
The only thing you'll run in to: higher filter orders need a "shit load" of AP2 filters to get phase flat if the x-vr is set at low frequencies on the high driver....
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Timo Beckman

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Re: 3TX goes active
« Reply #16 on: September 04, 2017, 04:26:32 pm »

Hi Timo,  thanks...will give a hard look.

By the way you might use FIR for the high's and after that use AP2 o the "low driver".
In doing so you can get really crazy results.


Because the FIR will introduce latency on the high driver the low driver's response will show phase going up and you can get it down again using AP2 filters. (It took about 8 AP2 filters if i remember correctly in this case. x-vr at 1K or 1K2 not sure about that since it's been a while since i did this one. Ofax needed a lot more work by the way).


The final response above had about 4ms of latency......
« Last Edit: September 04, 2017, 04:48:58 pm by Timo Beckman »
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Mark Wilkinson

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Re: 3TX goes active
« Reply #17 on: September 08, 2017, 07:40:23 pm »

Hi Timo, thx for the all-pass video.
 
I don't think I would have ever seen how to do that....work down from the high freq end, step by step. 
And yeah, wow can that process chew up a boatload of filters...especially when things get steep, or low.

I don't have a processor with on-the-fly all-pass capability.  I have to embed all-pass inside FIR files.
So, as you can imagine, it's impossibly time consuming for me to dial in all-pass like you showed,......
but really, I think the phase adjustment tools in the FIR generators are alot easier that the all pass method.

Your plot looks crazy good ! Nice work !!!

Here's my work today on a 3tx alone without sub (3-way, high-passed at 100Hz.)
Hope to tie in sub tomorrow,  and also check off axis verticals. Pretty sure horizontals are ok.

15ms latency....which is what I allow myself cause i use horn loaded subs that chew up about a dozen ms on their own.
This was with miniDSP....I'm checking out the Linea vs the miniDSP, but making the contest conform to a 15ms weight class :)


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Timo Beckman

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Re: 3TX goes active
« Reply #18 on: September 18, 2017, 06:07:21 am »

You might want to go less flat on the phase part in the low end.
Has to do with subs if you add them.

Since sub woofers are time stretched devices you'll see the phase trace go down under a angle  (the response it self will show The phase going down and implementing a low-pass filter at the desired x-vr will even steepen the angle.

I did a 5.1 surround set up using the RM25ac from fulcrum. The RM's are starting at 24Hz with the first and only wrap around at +/- 30Hz an after that the phase moves gradually toward the 0 line at about 500Hz.

If you add a sub woofer (at that time the only sub available was a 900LFC from Meyer) you have to alter the respons of the RM because of the sub.

(speakers in the 5.1 set-up where 2 x RM25ac (main lft/rght) 2 x FA28ac (surround lft/rght) 1 x UPJ1p center and 1 x 900LFC's for sub).

First the RM25ac solo(no processing):
https://timobeckmangeluid.files.wordpress.com/2016/10/rm25ac-strt.png?w=2000

And the full 5.1 set-up all speakers on measured at the gold mic position (all processed via a Galileo 6-16):
https://timobeckmangeluid.files.wordpress.com/2016/10/5-1-all-on-pink-noize.png?w=2000

As you can see the added sub forced me to implement a 2nd order allpass filter at about 100/125Hz to get every speaker to match.
(My training room is not measurement friendly sort of ;-) )
« Last Edit: September 18, 2017, 06:11:23 am by Timo Beckman »
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Mark Wilkinson

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Re: 3TX goes active
« Reply #19 on: September 27, 2017, 02:28:04 pm »

You might want to go less flat on the phase part in the low end.
Has to do with subs if you add them.


I do try to flatten phase as much as possible on the low end of the mains,
using however much latency I figure is ok. 
Just like I try to flatten the high end of the subs....

IMO, it's just a matter of how much latency can be allowed, otherwise I'd flatten all the way to 20 Hz  ;D
15ms has worked well on a half a dozen recent live gigs, which coincides with the latency using the SC-48's linear phase xover (LIR) @ 100Hz.

Below, are results after adding a sub to the 3tx, still set up 3-way active....
Purple is using the Danley SC-48, and its LIR filters for all three x-overs.
Green is miniDSP, with 15ms worth of taps performing all duties. (Windy day..ignore the HF phase rolloff)
So both have nearly the same latency...





 
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