1 Attachment(s)
Re: Summing at crossover - LR24db/BU24db
Well, i just wanted to make sure that everything is correct and tbh... checking polarity again doesn't take a lot of time. ;)
More important thing is, that even over a full circle of testing (that's 20 measurements each side in 0.02 steps over the full 0.4ms circle) i couldn't get full summing at the crossover which makes me believe that due to the locations of the drivers it wont happen regardless of what i can do with the DSP amp right now.
I know that Mosconi is currently checking to implement allpass filters into their V1 GUI that is used for the whole Gladen One, Mosconi D2 line of DSP amps as the hardware is officially capable of doing allpass filters according to Frank Miketta, but tbh. i don't really know if this will help me.
edit: i might have a phase issue at 500Hz.
See the left and right and left+right measurement.
Attachment 11588
That big dip around 500Hz isn't there in either the left or right measurement.
Re: Summing at crossover - LR24db/BU24db
It fun to see all this discovery going on, but please remember your results are really good. You're well into splitting hairs territory now so don't get too frustrated if you can't fix every last little thing!
Re: Summing at crossover - LR24db/BU24db
If you want to play with time alignment to get the best summing, try the Alignment Tool in REW.
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Re: Summing at crossover - LR24db/BU24db
Quote:
Originally Posted by
B5I8
If you want to play with time alignment to get the best summing, try the Alignment Tool in REW.
Sent from my SM-N975U using Tapatalk
What, what? Is this a new thing?
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Re: Summing at crossover - LR24db/BU24db
Quote:
Originally Posted by
Justin Zazzi
What, what? Is this a new thing?
I don't think it's a new thing. If you have a set of measurements go to All SPL, click Controls at the upper right, then click Alignment Tool. A little window will open which is the Alignment Tool. Select the 2 measurements you want to align from the drop-downs. In the SPL window of the measurements, click your cursor where you want to align. In my screenshot I have it around 68Hz. Make sure you have Show Phase Traces checked in the Alignment Tool then click the Align phase at cursor button. It will calculate the amount of delay you need on one of the measurements and the white line in my screenshot shows what the response would be with that delay. You can play around with the delay slider and watch the phase and response change. It's a neat tool. I don't know everything about it but I've been playing with it to see the effects when I adjust delay. If you click the Aligned Sum button it will generate a new measurement.
Justin, you're the expert here being a sound engineer. Perhaps you can share with us how to best utilize this tool when tuning.
Attachment 11612
Re: Summing at crossover - LR24db/BU24db
Holy hotcakes that's new to me.
And dark mode? What!?
Actually I can't find those options.
What version are you using? I have 5.19
Re: Summing at crossover - LR24db/BU24db
Quote:
Originally Posted by
Justin Zazzi
Holy hotcakes that's new to me.
And dark mode? What!?
Actually I can't find those options.
What version are you using? I have 5.19
I use the latest V5.20 beta 53.
Sent from my SM-N975U using Tapatalk
Re: Summing at crossover - LR24db/BU24db
Quote:
Originally Posted by
B5I8
I don't think it's a new thing. If you have a set of measurements go to All SPL, click Controls at the upper right, then click Alignment Tool. A little window will open which is the Alignment Tool. Select the 2 measurements you want to align from the drop-downs. In the SPL window of the measurements, click your cursor where you want to align. In my screenshot I have it around 68Hz. Make sure you have Show Phase Traces checked in the Alignment Tool then click the Align phase at cursor button. It will calculate the amount of delay you need on one of the measurements and the white line in my screenshot shows what the response would be with that delay. You can play around with the delay slider and watch the phase and response change. It's a neat tool. I don't know everything about it but I've been playing with it to see the effects when I adjust delay. If you click the Aligned Sum button it will generate a new measurement.
Justin, you're the expert here being a sound engineer. Perhaps you can share with us how to best utilize this tool when tuning.
Attachment 11612
Nice!! yea I also did not know REW had this. I will DL the latest update tomorrow and check this out. I am also running Dirac so will test before and after to see how much of a diff it actually made! :D Either way, esp pre-tune I think this will help if it works right... or if I can figure out how to make it work right.
1 Attachment(s)
Re: Summing at crossover - LR24db/BU24db
I tried it today on my system.
It didn't really worked on my mid/tweeter crossover, probably due to fucked up phase by all the reflections in the car. Had some weird proposals for time adjustments, i.e. around 8ms on my right tweeter in relation to my right midbass before i did my time alignment.
Didn't do that, but instead went with impulse responses instead. After i set the time delays according to the impulse responses (measured several times after setting the delay to check if the measured responses were consistent) the proposed change for phase adjustment were over 2ms for the left tweeter and 1.5ms for the right tweeter. Didn't set the additional delay as it didn't seem to be right in that area compared to the measured distances.
First for both midbass drivers until the impulse responses were basically on top of each other between left and right, then the tweeters by doing the same, then tweeters to midbass.
Then i did the aligment tool to for the sub/midbass integration.
This is how i did this step.
- Midbasses/tweeters left/right were time aligned, so i linked everything together (4 channels)
- measured left/right midbass/tweeter and sub (on it's own) and made a average by the help of the trace arithmetic in REW ((a+b)/2) for the left/right mids/tweeters measurements. Measurements were done several times with acoustic timing reference. After first measurement i estimated the IR delay in REW in SPL+Phase tab and let REW set the delay into all following measurements.
- then i opened the alignment tool, put the average response into the first dropdown and sub measurement into 2nd dropdown.
- Then i clicked "Adjust phase" button.
- REW then proposed a delay of 2.2 ms for the sub.
- I put it in into my DSP, flipped polarity and did a ppn measurement to see the dip.
- Did some fine adjustments of only a few clicks and landed right at 2.08ms delay for the sub for the deepest null at 80Hz (my sub/midbass xover point).
- flipped polarity again and got a really good alignment in the sub/midbass xover region.
Attachment 11625
So instead of adding several ms of delay to the front drivers and flip polarity of the sub i added 2.08ms seconds of delay to the sub and got the response above. Above response is with flipped polarity on the tweeters as i had a deep dip although the impulse responses are spot on.
Re: Summing at crossover - LR24db/BU24db
Hmmm.... I've been seeing people "flip" the polarity of a single speaker lately, in order to correct a small dip in the overall response. If time alignment is set correctly, we shouldn't need to flip the polarity of any speakers, should we? I thought that the whole purpose of time alignment was to get all of the speakers 'in phase" at the listening position. If time alignment is set by measurements, how could the time alignment be *so* wrong for a speaker that we need to do a 180 degree phase shift for an entire single speaker? Wouldn't that suggest that the time alignment is way out of whack for that speaker?
I could understand maybe needing an allpass filter to correct a phase-related issue at one small area of the response (if it truly is caused by a phase issue), but having to do a 180 degree flip of the polarity of an entire speaker? That just doesn't make sense to me. I thought that was the best we could do before advanced DSP's were available, but that it wasn't really a common practice now that we have very powerful DSPs to help with timing and phase?
I'm sure that I'm just misunderstanding something though. Although, I've never had to flip the polarity of an entire speaker in my car, which is why I'm kind of curious...
Thank you!