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DSP Xover project (part 2)
DSP Xover project (part 2)
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Old 3rd October 2019, 06:30 PM   #3381
Joao@AltheaMusica is offline Joao@AltheaMusica  Switzerland
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Join Date: Aug 2009
Quote:
Originally Posted by spalmgre View Post
I had miniDSP 2x4 (not HD) before Najda. Najda is a complete preamp DSP solution that your family can learn to use. Maybe you can understand why this is important.
But I can not really complain about anything with miniDSP.
The 2x4 line is ok if you have passive or active 2-way speakers. If you need more channels then there is the 4x10, 2x8, etc.
But all boxes have good features and at the same time they lack critical features. So I can not say witch box to buy instead if Najda.

As I like to get into developing FIR filters I don't think I will buy miniDSP products. The computing power of a PC computer is much cheaper. And I already use jRiver so I get the convolution engine there. So I only need to buy a multi channel USB DAC.
Till then I can develop FIR filter to correct room and phase and convolve them with jRiver. And use NajdaIIR for speaker driver linearisation, time alignment and xo.

Thanks for sharing your opinion / experience... and I agree that the Najda is so flexible. I use it with the analogue input for my phono stage and the SPIDF for my digital (currently Blue Sound Node2i).
For my horns, driven active, the ability of using the time delay is a mercy which I will not miss again. As well that Najda is providing all the filter slopes you need.

Is JRiver running on Macbook / Linux as well?
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Old 4th October 2019, 09:57 AM   #3382
spalmgre is offline spalmgre  Finland
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Join Date: Jan 2015
Location: Helsinki, Finland
Quote:
Originally Posted by Joao@AltheaMusica View Post
Najda is providing all the filter slopes you need.
?
Here how I go about when I adjust Najda. I have some new JBL VTX12 horns and did this procedure last weekend. It is much faster to do if you have decided on the order for each task.
But it still takes many hour to do it properly.

I use REW for measuring and then go to the EQ tab to let REW calculate the filter. I measure each driver separately and calculate the linearization filter for them.
I defind the house curve text file:
1000 0.0
20000 -3.0 (or -6.0 or whatever you like)
You can easily alter the curve up or down. This changes the QE for the treble and hi midrange.
It is important to understand that the best direct sound curve is not a straight line but a falling curve towards the hi frequencies.

EQ Match range a little wider than the xo range. Max boost 3db and flattens 1db or 2db. I recalculate until I find "EQ filters" that I think will not overload Najda.
I then manually add the filters to Najda.

-------------
The time alignment is tricky. You can find many recipes and I must say I'm not sure am I doing it right. This is how I do it.

I measure the left speaker about 1m from. In the "Measure" screen set "Timing" -> "Use acoustic timing" reference". The right speaker will produce a reference point in time.

Measure each driver separately. Each driver is measured with a narrow Freq Range around the xo frequency. This means two measurments for mid if you have a 3-way setup. The idea is that you are interested in the sound delay (phase) where the driver is working in parallel with the other driver close to the xo frequency.
Press the "i" (Info) button in the left upper part of the main interface. Look at "IR start time". The difference between these values is the difference in time that the sound is produced by each of the drivers.
Lastly, you need to choose which driver has the longest measured delay. This driver shall have 0 delays in Najda. Then you calculate the difference for each driver compared to this driver.
....................

When this is done I set the XO where I think that is good to start. Then I remeasure with REW and adjust xo frequency and slope until I find a good compromise.
Attached Images
File Type: jpg JBL VTX12 ox.jpg (114.4 KB, 185 views)
File Type: jpg JBL VTX12 linearisointi.jpg (198.1 KB, 185 views)
File Type: jpg JBL VTX12.jpg (631.5 KB, 184 views)
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Old 4th October 2019, 10:07 AM   #3383
spalmgre is offline spalmgre  Finland
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Join Date: Jan 2015
Location: Helsinki, Finland
Quote:
Originally Posted by Joao@AltheaMusica View Post
Is JRiver running on Macbook / Linux as well?
yeas jRiver is running on all platforms. I wonder if the new Raspberry Pi 4 is powerful enough to do FIR convolution. The PI 3 version already runs jRiver as a player.
When you rip CDs with jRiver or some other players you get a better bitstream on playback as there is no dropouts from the mechanical CD player.
The CD is reread until the bitstream is ok so the PCs CD player/reader is not important. This saves a lot of money as you don't need to invest in a good CD player.
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Old 4th October 2019, 03:00 PM   #3384
Joao@AltheaMusica is offline Joao@AltheaMusica  Switzerland
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Join Date: Aug 2009
[QUOTE=spalmgre;5934000]
The time alignment is tricky. You can find many recipes and I must say I'm not sure am I doing it right. This is how I do it.

I measure the left speaker about 1m from. In the "Measure" screen set "Timing" -> "Use acoustic timing" reference". The right speaker will produce a reference point in time.

Measure each driver separately. Each driver is measured with a narrow Freq Range around the xo frequency. This means two measurments for mid if you have a 3-way setup. The idea is that you are interested in the sound delay (phase) where the driver is working in parallel with the other driver close to the xo frequency.
Press the "i" (Info) button in the left upper part of the main interface. Look at "IR start time". The difference between these values is the difference in time that the sound is produced by each of the drivers.
Lastly, you need to choose which driver has the longest measured delay. This driver shall have 0 delays in Najda. Then you calculate the difference for each driver compared to this driver.
....................


Yes, there are some recipes for adjusting time delay...
I measure "on time" using pink noise and adjust it after setting the crossover points for each driver. For example, mid to high frequency - reverse the phase of one channel (mid or high) 180 and then look on the crossover frequency of the drivers in the measurement... there must be a break-in of the signal. Then adjust the time delay of the driver: time delay is correct when the break-in point is lowest.
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Old 9th October 2019, 05:45 AM   #3385
noviygera is offline noviygera  United States
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Join Date: Mar 2009
Anyone hear any good news about Nick?
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Old 9th October 2019, 06:55 AM   #3386
JLOP is offline JLOP  France
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Join Date: Sep 2011
Location: Luxembourg
Hi, unfortunately not, as far as I know here in Luxembourg. it’s been about 4 months now...
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Old 9th October 2019, 02:27 PM   #3387
spalmgre is offline spalmgre  Finland
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Join Date: Jan 2015
Location: Helsinki, Finland
Quote:
Originally Posted by chaparK View Post
I'm sorry to say but production is halted.
I have looked for a partner to take on manufacturing and distribution, unfortunately without success. I have no stock left.

Cheers,

Nick
All you who wonder will there be any more Najda production should read Nick's message.
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