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rv295

Linn Exakt Design Digital Active Crossovers with DIY speakers plus other crossover related stuff including FIR.

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Bit confused here, the phase should run along the 0 line. -180 is a speaker connected out of phase. Has it gotten confused with the impulse centre perhaps?

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34 minutes ago, edd9000 said:

Bit confused here, the phase should run along the 0 line. -180 is a speaker connected out of phase. Has it gotten confused with the impulse centre perhaps?

I hadn't spotted that Edd, REW isn't set to invert the phase of the measurement and the drivers aren't wired up wrong.  I'll take another measurement and see if it's reading it out of phase again.

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1 hour ago, edd9000 said:

Bit confused here, the phase should run along the 0 line. -180 is a speaker connected out of phase. Has it gotten confused with the impulse centre perhaps?

My fault, REW was set to invert on the laptop, I checked the default settings on my PC as I've never intentionally changed it.  Not that it seems to make any difference. 

I've taken a new measurement with invert turned off.  Exactly the same result but no longer out of phase.   Here is a close up measurement, part of the mid driver without any gating.  Forgive the photo of the laptop screen, I'm using my phone and I'm too lazy to do it properly. 

WP_20170524_20_57_55_Pro.thumb.jpg.ee8459602c8d26fbfdeec03db6b855a0.jpg

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1 hour ago, rv295 said:

Not that it seems to make any difference. 

Just makes the graph easier to read :D 

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Indeed it does, I can't believe I hadn't spotted it myself.  I was excited to see the result and concentrated too much on the fact it had worked.

If I was going to be picky, I'd like to know why the phase drops off in the high tweeter frequencies when the mid response was predicted near perfect.  I know the tweeter naturally rolls off after 14 or 15KHz but the phase is rolling off before that.  I question how much difference this phase roll-off would actually make in real terms, at those frequencies but it would have been nicer to have it flat all the way up to 20KHz, even with the natural roll-off from the tweeter.

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You can add a phase only filter to correct it. 

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Super Dealer

Have you applied any model to the top end of the tweeter?  I generally set the roll-off model for the tweeter to be phase only.  This should help to linearise the phase but avoid sending too much current into the coil as the SPL dies away.  It will never be perfect with the current simple inductive model but it can always be tweaked with some model filters.  As Edd suggests adding a phase only filter may fix things.

Take an axial measurement of the tweeter in isolation, apply a filter and re-measure to see how well it has fixed the issue.  Once you have a good measurement try at 30 degrees and make sure you have not just corrected for the cabinet...

Phil.

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3 hours ago, edd9000 said:

You can add a phase only filter to correct it. 

Cheers Edd, I was hoping to see it done automatically via the figures from the impulse measurement.

6 minutes ago, Philbo said:

Have you applied any model to the top end of the tweeter?  I generally set the roll-off model for the tweeter to be phase only.  This should help to linearise the phase but avoid sending too much current into the coil as the SPL dies away.  It will never be perfect with the current simple inductive model but it can always be tweaked with some model filters.  As Edd suggests adding a phase only filter may fix things.

Take an axial measurement of the tweeter in isolation, apply a filter and re-measure to see how well it has fixed the issue.  Once you have a good measurement try at 30 degrees and make sure you have not just corrected for the cabinet...

Phil.

Cheers Phil, 

You are right...  The last time I had an issue updating the speakers; I had to remove the roll-off correction on the tweeter otherwise it wouldn't load the filters in the exkatbox. (I simply forgot I'd done this).

I have now loaded a set of filters with the tweeter roll-off (phase only) included in the model.  Oddly though, I couldn't load these filters in the exaktbox unless I reduced the number of taps well below the maximum available.  I'll try another measurement tonight and see if it works. 

Edited by rv295

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Super Dealer
14 hours ago, rv295 said:

I have now loaded a set of filters with the tweeter roll-off (phase only) included in the model.  Oddly though, I couldn't load these filters in the exaktbox unless I reduced the number of taps well below the maximum available.  I'll try another measurement tonight and see if it works. 

Odd.  Not a problem I have encountered before, in fact this was the way the system was run for Scalford with all processing allocated.  I will mention this to Jim.

Let me know if you get it working.

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19 hours ago, rv295 said:

I have now loaded a set of filters with the tweeter roll-off (phase only) included in the model.  Oddly though, I couldn't load these filters in the exaktbox unless I reduced the number of taps well below the maximum available.  I'll try another measurement tonight and see if it works. 

Ross,

Would you be able to send me a Konfig UserLog.txt that was captured during a session when the filters refused to load onto the Exaktbox? That should help us figure out what's going on. The UserLog.txt is started afresh each time Konfig is restarted - so you would need to grab a copy before Konfig is restarted to avoid the interesting bits getting lost.

Cheers, Jim.

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5 hours ago, Jim Liddell said:

Ross,

Would you be able to send me a Konfig UserLog.txt that was captured during a session when the filters refused to load onto the Exaktbox? That should help us figure out what's going on. The UserLog.txt is started afresh each time Konfig is restarted - so you would need to grab a copy before Konfig is restarted to avoid the interesting bits getting lost.

Cheers, Jim.

Thanks for the reply Phil and Jim and no problem, I may not get chance until this evening though. 
Regards

Edited by rv295

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5 hours ago, Jim Liddell said:

Ross,

Would you be able to send me a Konfig UserLog.txt that was captured during a session when the filters refused to load onto the Exaktbox? That should help us figure out what's going on. The UserLog.txt is started afresh each time Konfig is restarted - so you would need to grab a copy before Konfig is restarted to avoid the interesting bits getting lost.

Cheers, Jim.

Sorry for the delay Jim, Info sent to you by private message on here.
Regards

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Should I have to consider "compatible speakers"? With DEQX, all speakers are compatible, for both speaker correction and room correction. The former may be limited in part by the presence of a passive crossover, but these can be removed at some point once enough amps are on hand for driving each driver from a monoblock.

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2 hours ago, acheter said:

Should I have to consider "compatible speakers"? With DEQX, all speakers are compatible, for both speaker correction and room correction. The former may be limited in part by the presence of a passive crossover, but these can be removed at some point once enough amps are on hand for driving each driver from a monoblock.

You can use whatever speakers you like, the comment about compatible speakers was based on a misunderstanding of how the software worked.

If you go back and read the thread then you'd see that you can use exakt.design with any speaker.  Even unknown speakers. 

I've tested this myself by measuring and modelling some 20 year old bookshelf speakers without knowing any manufacturer specifications at all.  Just read the page before this one to see how it's done. 

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