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Kb86 said:
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This is my example. my tweeter and midrange 120 degree shift and sum at 2450hz with 0db gain. on what frequency should i attempt to use first order all pass filter? thank you.
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Can you post your actual data. A picture of that would be worth 1000 words. I understand what you are saying about your summing (you get 0 summing) but without seeing the data, anyone that gives advice on using all pass would just be guessing.
 
Justin Zazzi said:
If your speakers sum together flat, then what problem are you trying to solve?
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Not flat… zero summation, none… he is only ever guessing that he has 120 degrees out

put simply no he needs a phase graph to accurately see how the best way to tackle it is…

Also I’d question how he has set the timing?
 
dumdum said:
Not flat… zero summation, none… he is only ever guessing that he has 120 degrees out

put simply no he needs a phase graph to accurately see how the best way to tackle it is…

Also I’d question how he has set the timing?
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Yup, and for those that don't have access to real time phase, this is where the JL target curve stuff is SUPER powerful. You can take your speakers measured response, use that to create an identical target, then view the phase and make adjustments to your system based on those targets in the jl tun software.....which all of that is free!

You can even mimic reflections and what they will impact with the tun software by having a similar acoustic response just different levels.
 
Like this example here: This is a "perfect" tweeter response, with a "perfect" reflection that is -6db and delayed in time by 1.04ms (or about a 1ft)

Yellow trace is your sum, red is your original, and white is the reflection

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now if I throw another "reflection" into here that is now -12db and delayed by 2.08ms.. Now green is the second reflection

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Kb86 said:
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Just very crudely making your measured results, I can get a fairly similar graph if I delay the midrange a little bit more than it should be. Not saying this is your issue, but it could be. The closer you could get to having your exact information into Jl tun, the better the model would be and you could then use that to make changes to your measured system.....very powerful stuff right here people!

If one didn't have access to smaart or open sound meter, you could use your usb microphone and measure via tun, make a target curve so you can then get phase information, and line up everything that way. Obviously all this becomes easier and quicker if you have smaart or open sound meter (I don't expect many on here to have a jl max like I do now...for reasons)


 
i tried adjust timing, not better sum. Could be reflection at that frequency.
i tried phase slider on helix dsp, around 20 degree adjust on tweeter, sound much more smooth at high and definition at drum/kick drum. but it screwed my imaging.
i move crossover point out of that problematic zone. Move to 2800hz acoustic xover. Happy result. - thanks @dumdum for advice.

im still asking/messing with 2450hz xover zone for a sake of learning how to do first order all pass filter using only RTA and ear.

Nick demo that technique but it was easy when there is big cancellation. just use 2nd apf at that exact frequency dip.
for around zero summation, how to determine what frequency should i attempt to use 1st order apf?
 
I'm trying to integrate a factory head unit with a Helix Ultra. The car is a Subaru Outback 2020 with Harman Kardon. When I use digital straight to the Helix all speakers are in phase and sum at the crossovers. This indicates to me that everything in the car is setup perfectly. When I use the factory head there are issues. Nick A has looked at this a few times and the best we could come up with in a brief setup was to add delay of 14-15 ms on the left side. This definately helps me to get a decent tune but there are still issues. With polarity set to normal on all speakers my mids are out of phase with each other left to right. In this configuration the left side is in phase and the right side is in phase. If I keep playing the game of polarity flipping something always ends up being out of phase. I recently upgraded the software on the Helix to the newest update because I saw there were updates to the ISA (input signal analyser). There is a glitch in the software that doesn't allow that page and only that page to fully show up on my laptop. I called Audio Tech Fisher and they said they are aware of the problem and are working on it. I'm sure there is also a learning curve o be able to detect these fancy integrated cars. In the meantime does anyone know how to integrate a factory 6th gen Subaru Outback. There is no Nav-tv or Pac that I am aware of. I even considered getting the Kicker key loc. That would be wrong considering I have this Helix Ultar with fancy integration that I don't know how to use properly. What sort of measurments can I take that will help my situation. I have REW and a USB mic.
 
You probably have all pass filters on that system and will need to look more into that. The ISA can help when you play each indivual signal and then play the combination signal (both left and right together) and see what frequencies are impacted. You can then play with all pass on those bands to where it sums better. This is why flipping polarity does not work. It isn't the entire signal out of phase, it is a certain frequency band and the only way to fix that is all pass filters, otherwise flipping polarity will always have that band out of phase.

The easier and better way would be able to measure the phase of each speaker in real time using smaart, open sound meter, or JL tun software with the max.
 
Thank you. I figured as much. I will try some all pass filters. I think it might be in the 250 Hz area. Audiotech Fisher updated the ISA section and they claim its much easier to detect timing and allpass filters. This is an area that I'm not all that familiar with. That ISA page is only half visible right now until they update the software again or I try a different laptop(I only have one) Is there some literature I can read or videos that explain how to look for these factory integration factors. Or is there a way for me to provide REW measurements on this site for an EASY-BUTTON. I wish there was someone at Subaru that I could call and ask what the Heck they did.
 
Stycker said:
Thank you. I figured as much. I will try some all pass filters. I think it might be in the 250 Hz area. Audiotech Fisher updated the ISA section and they claim its much easier to detect timing and allpass filters. This is an area that I'm not all that familiar with. That ISA page is only half visible right now until they update the software again or I try a different laptop(I only have one) Is there some literature I can read or videos that explain how to look for these factory integration factors. Or is there a way for me to provide REW measurements on this site for an EASY-BUTTON. I wish there was someone at Subaru that I could call and ask what the Heck they did.
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If you play an individual speaker and meaure it's response, then play the other speaker and measure it's response. Then play them both and see where it is not +3-6db above the individual responses. Where there are big dips is where you will need all pass filters. Start playing with frequency and width (q) until the problem area is fixed without impacting other areas. This is more or less a guessing game without being able to actuall see the real time phase of each speaker.
 
OK thanks. I'll do some more measuring and evaluating. In the three years I've had this car I keep getting closer. I have it to the point where I enjoy how it sounds and images but its still far from my competition tune with direct digital into the processor. Right now I have it set up with the left mid and left midbass out of phase with everything else being in phase. This is the best setup so far. Imaging is centered with a slight right bias. Sounds fuller on the right. I also think finding the right allpass filter will work.
 
Hi, how to avoid digital clipping?
Source is iphone, wired carplay to head unit, most adapter 150 (nav zen tv) toslink to Helix ultra.

I see Andy explain about digital clipping but only with high level input to dsp.

I cant find anything about digital clipping when feed digital source to dsp directly. Any infor or articles regarding this in car audio? thank you.
 
Kb86 said:
Hi, how to avoid digital clipping?
Source is iphone, wired carplay to head unit, most adapter 150 (nav zen tv) toslink to Helix ultra.

I see Andy explain about digital clipping but only with high level input to dsp.

I cant find anything about digital clipping when feed digital source to dsp directly. Any infor or articles regarding this in car audio? thank you.
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If you can find the quote where Andy is talking about digital clipping then I might be able to help you understand it better. My best guess is he is talking about input clipping the high level input of the dsp. If you feed an *analog* signal into the dsp that is too large then it will not be able to cope and the signal will be clipped or distorted.

If you send a digital signal to your dsp, then you cannot clip it by sending a signal that is too large. This is one of the nice benefits of digital signals, they just work. The toslink connection you are using cannot create digital clipping so there is nothing to worry about, and there is no information or articles about this in car audio because it is a problem that does not occur.
 
Thank you Justin. Its weird i heard distortion doing that way. While bluetooth directly to dsp sound fine. Guess there is something wrong in that chain.
 
Cathul said:
Probably this one:

https://www.audiofrog.com/are-scopes-and-sine-waves-useful-when-setting-up-dsp/
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Thank you Cathul, good find. I think I understand your question better, @Kb86 It looks like Andy is talking about different sources of clipping: input, output, and digital.

If you're interested in determining if this is happening in your system, there are a few options:

Input clipping:
To hear what input clipping sounds like, you need to overdrive the input of the DSP with an analog signal that is too hot. At the same time, you want to turn down the *output* of the DSP so that you can still listen to the speakers at a medium/low volume and not blow them up, but you still want to be able to hear the music and be able to listen for the distortion. Try turning the output trim on the DSP to something very low like -60dB and then turn the DSP input to maximum, and the DSP's input gain knobs to maximum. Then play something on your radio at very low volume level (like 5%) and slowly turn up the radio. At some point you should turn it up loud enough that you get distortion to occur and it should be obvious eventually, but you will hopefully still be at low/medium listening volume level so your speakers won't be in danger of blowing up.

Digital clipping:
Similar to above. Disconnect your tweeters before you do this as digital clipping has a lot of energy that can fry a tweeter instantly. This is risky for any speaker so be very careful about doing this while speakers are plugged in, maybe disconnect all but one speaker just to be safe. Do the same as above, but raise the radio volume level to just below the point where the system is distorting. You should have music that sounds clean but at a low listening level. Then go into the DSP and boost everything you can find (other than input gain), one setting at a time. If you do enough boosting inside the dsp, *and* you are still listening at low to medium volume levels, then you should get digital clipping. It will sound absolutely terrible and be 100% obvious. Don't forget to disconnect your tweeters first!
 
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