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Discussion Starter #21
:worried: Okay so (that was a joke BTW he he)


More coming soon.

Once I get going and get all my info organized so it makes sense we will see how things need to be invertable

Meaning , you have to be able to reverse the polarity and have the opposite happen. If there’s a reflection that has diffraction attributes to it , we will see that diffraction can not be un-diffracted.

We will be discussing how to pull phase around and get a reflection to behave a bit better so that it’s high and low air pressure spots are not in a offensive spot.

Keep in mind moving phase can act like moving sound forward or delay but it all comes out at the same time. Nothing is delayed , it’s just structured a bit different that’s all ;)

More soon
 

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So you are using rephase to generate the filters for the minidsp unit. How does it sound? I believe you used APL1 before. How does that compare with what APL1 does?
 

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Discussion Starter #23
So you are using rephase to generate the filters for the minidsp unit. How does it sound? I believe you used APL1 before. How does that compare with what APL1 does?
YES with minidsp 2x4HDs, I go over a few minidsp products in the first few posts that are compatible. But with focus on the minisharc (2048t at 96k or 4096t at 48k)

APL1 , almost had the trial up and running , still want to try it. Got massively sidetracked and had a revelation with rePhase. The APL1 trail is on back burner.

It sounds stellar (I hit the glory hole by gosh) (I’m such a nerd)


My car is definitely that car that sounds nothing like it should relative to where the speakers are placed. It definitely sounds like a ton of DSP is applied , but not in a bad way at all, quite the contrary in fact. Can tell lots of dsp is in use, but dsp done well. Very dynamic , no harsh spots, goes very loud with stage staying exactly the same at all volumes.


Once I went to a concert (smallish venue about 2500ppl) and it had a very similar effect. Except in the car it’s reproduction and has all the artifacts of a recording engineer, solid center , etc.... but anyhoo my car reminds me of that venue. I remember the concrete building it was in seemed to have no reverberations and seemed like i couldn’t hear any echo.




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Sorry for slow to post, been very busy at work, the holiday season in car audio is slammin , we’re doing a lot of installs working long hours,

But after January I should start having more time, I stepped down from management to move to a store closer to home, (5hr a day drive too hard on the Fam) so I’ll finish the year in my store than transfer. Makes me pretty sad, I love that position and worked pretty hard to attain it, but need to open new chapter. So, I’ll have more time for everything else. (Should be a good thing for now)



I saw this pic and stole it from a site and wanted to share it , it shows the different zones as far as acoustic behavior is concerned in a room. Each “zone” needs to be addressed separately as they all react differently to the overall manipulation of the audio signal.

I have a lot of screen shots made and am making posts in HTML and PHP , as soon as I feel the info is as accurate as I can explain I’ll post. I sometimes get ideas and thoughts mixed so I want to be careful to not have misinformation or convey a point that is right but comes across incorrectly. I assure everyone it will be through enough to make good use of it


 

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Discussion Starter #24 (Edited)
so, here are a few pics of some measurements at the listening position. I did a left and right , no-EQ just crossovers (mixed phase, some iir some fir and some half and half) you can see the phase wrap wheres there's iir crossovers or a time delay.

I added a 5cy IR window to everything. Than I rand Dirac Live , No pre-tune, with a flat response (cant remember if I had tilt, either way just for conversation. Lets look at what is going on before and after.

Ill post about it after so I can write from my phone instead of this bulky computer..Also a view of the rePhase files and minidsp configs
















 

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Discussion Starter #25 (Edited)
So ,
I used Dirac as a fast example of what one of the big goals is just for speed


If you look at the left and right no correction (can see what measurement I have open)
And left and right with correction it’s pretty easy to see what’s going on.

Phase is not pancake flat. There are wraps still , and that’s OK! You can not hear a phase change on a single speaker, and that’s the point of this post to get you going on what to do.
It’s when you introduce the other speaker/channel (depending on what your doing) the goal is to have left and right phase and magnitude to be as close as symmetrical as possible (at least for now, later we will go apeshit on APFs and shape the stage and completely disregard the symmetry, but that’s way way way down the road. For now, just get them looking symmetrical)

(Sorry for not making my limits the same but you get the drift)

As long as the Left channel vs right channel are making the same shapes in magnitude and phase it will be “phase coherent “ (not a real word but can be used)

Keep in mind if your spl meter is calibrated on your measurement software and you take measurements from the same point in space on the driver side , the passenger side will look like it’s phase is more “positive “ throughout the magnitude. That’s what you want. You don’t want to try to “correct” the magnitude of the phase to match the phase on the left by correction. I moved my scroll bar and so you can’t really see it because I added windows because I took these measurements a while back. The reason the right side will be positive is it has more delay, (time of flight, unless you window it out which you will) but at first the right will look a few degrees positive in the linear view and simply more positive in log.


If you were to try to correct for that the center image would be directly in front of you instead of between the speakers, you want to let the magnitude in “db” move phase for you throughout the FR magnitude. By simply reducing the output on the left side will move the phase with it in the opposite direction. After all your signal delays are done and FR is made to your liking and is symmetrical on both sides, let the minimum phase behavior move the phase magnitude. We will only be focusing on the shape of the phase vs Left and Right and how the shape relates to the FR magnitude.

If we look the Dirac Software made Left and Right look dam near exactly the same on Left and right in FR and phase (BTW FR means frequency response, but you knew that)

This view is in the linear axis just for viewing. Even in the linear axis you can see some issues where phase isn’t exactly the inverse of FR. It could be just the view , the measurements, the window, but it’s always a good idea to start to pay attention to those anomalies with each view window your in. Start to get a feel for the room.

But even with this , one could set the magnitude so that FR has the most symmetry as possible between channels, asymmetrical crossovers can be very useful and asymmetrical level setting between channels in a multiway can be very valuable before running to the eq.
Your crossovers can make a lot of good changes for you and save a lot of backtracking later down the road.

After EQ Left and Right you should have a good baseline on what to do next. There will be back tracking, be ready, trust your ears also, Ive skipped over hundreds of validation measurements by just using my ears, once you get a hang of what a phase change will sound like when played against its other stereo half you can get a knack for what’s off and needs fixed to get left and right to be more symmetrical.

Once you get some real symmetry happening with crossovers and levels and eq , than its time for a few more sets of measurements. The phase changes you make you will want to compare what individual drivers are doing as far as phase behavior vs when it’s paired with its fellow drivers on like channel and that will let you get an idea of what’s happening when they sum.
When you take your 2nd set of measurements, and have a decent flat (or reference target magnitude) between left and right its time to do a different viewpoint. You’ll want to get rid of the time of flight delay and generate the minimum phase response. Getting rid of time of flight delay I like to just remove samples from the IR, the acoustic timing method will use the HF driver as a dominant reference point. I like to loop back and move the IR manually, I like to see what happens as I move the delay out of the IR window. If you center before the peak, in middle of peak, or where ever , find out how long your foriour is, make sure Left and Right have the same windows applied and same settings in your analysis. That way if you remove 2 samples or 200 samples.

Once you generate a minimum phase you can now see inverting that’s happening as amplitudes change and how the phase should look a lot like the mag inverse.
In any spots that do not look the same between left and right and that do not follow the general inverse shape of the FR those are areas we will want to look deeper into.

For a two seat tune simply (ha simply it’s no easy thing) make measurements of the passenger side as well, the the driver and passenger to have the similar phase response that is a mirror of itself. Does not have to be perfect (it can’t!) just not swing to -180deg to +180deg between combfilters. Get it so they both +/-90deg on both sides to mirror each other. Some spots will be achieved some won’t be so much but just make it best you can. This will get into more later, let’s start with a one seat tune before we whip out our shlongs.


Any phase change will affect FR as well, and any phase change in one area will move phase all the way through the spectrum in some areas. After a correction is made its pretty important to listen and RTA with some noise and re adjust eq or levels. Once you change phase the way the speaker behaves in its space will change the FR as well. Could make some areas louder with reinforcement or quieteter with interference. A phase change will change the interferences all over the place and a new measurement must be made after levels are re balanced. Once you get few the first few you’ll notice some cancellations actually sound better and should be kept as it may add to the entire room character better it’s sound envelopment or spacial impression.

Next posts will be covering those types of views and how to import the measurements into rePhase and start making corrections!
 

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Hello, I run carpc win10, i have only 2 ch output (Essence ST card). I can play active with Amp xovers (arc audio SE4200 + 2300 amps) and run Rephase in my carpc? ,

my settup is tweter, midwoofer + sub. (seas magnum + seas W15cy001 + L26roy)
 

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But after January I should start having more time, I stepped down from management to move to a store closer to home, (5hr a day drive too hard on the Fam) so I’ll finish the year in my store than transfer. Makes me pretty sad, I love that position and worked pretty hard to attain it, but need to open new chapter. So, I’ll have more time for everything else. (Should be a good thing for now)
I knew you've eventually jump stores, the drive on 25 is absolutely insane.
 

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Discussion Starter #28
Hello, I run carpc win10, i have only 2 ch output (Essence ST card). I can play active with Amp xovers (arc audio SE4200 + 2300 amps) and run Rephase in my carpc? ,

my settup is tweter, midwoofer + sub. (seas magnum + seas W15cy001 + L26roy)

Yes in fact that’s a sweet way to do it (if your ok with car pc lag) but yes with
Jriver as a convolution engine and rePhase you get get a very high tap count.

Keep in mind CPU convolution and FFt convolution are a bit different, but a lot of ppl use a pc as a DSP and run half million tap filters with good success. I tend to like fft better with shorter impulses (the smearing stays manageable)
 

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Discussion Starter #29
I knew you've eventually jump stores, the drive on 25 is absolutely insane.


YES it is downright brutal !

1week at new store so far so good, it’s a bit tough at times going to a new store because no one knows how intense I am with car audio so I have to throttle way back to mind others egos and feelings to a degree. But so far so good ,
24hrs a week more with the fam...









——————————————————————————

More to come later , after the Super Bowl. I’ll be back on my game and get to more rePhase fun .
 

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Sound a lot like myself :D A little bit freaky about DSP

In all honesty Dirac is a excellent tool hands down ,

But for the guy that can settle on a set of speakers and settle on not changing out his or her equipment every month and spent the time with rePhase one could really nail down a correction that performance is better than a Dirac tune with no mods, a tweaked Dirac tune is very good , but for those with the manual fir rePhase can do wonders .


Can’t wait to use Dirac car platforms, not available as of yet but from what I hear is in the works, I have very high hopes for it.
If I run the DDRC-22D before a Helix DSP Pro and perform the Dirac Live measurements while the Helix is outputting a R+L summed center channel, will the output of the center channel be similar to the Dirac Virtual Center feature from their automotive sound systems?



“Dirac Virtual Center can be applied even when a physical center speaker is mounted. Depending on the input mix to the center speaker, the soundstage tends to be rather narrow, in particular when the center speaker is fed with a left + right signal. Dirac Virtual Center allows for a tuning process where the physical center speaker is used to stabilize the center image rather than creating it. This results in a more stable and wider soundstage and a more distinct phantom center compared to when only a physical center speaker is used.”

https://www.dirac.com/dirac-virtual-center/
 

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Nope, Dirac live doesn’t have all the fancy new stuff for oem yet.
And the 22d is only stereo so no way to create a filter for your center only.
But you could try an ms-8 for that, Logic7 works very well!
Best next step I guess would be the future Audiofrog dsp.
 

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I was hoping through some awesome Dirac magic that it could help alleviate the mono center channel that most DSP users are stuck with due to companies not investing the pricey licenses for center channel processing.

Something along the lines of:

Since the center is R+L...

Only the R signal would come out of the Center in conjunction with the right speakers when performing the right side tune. And only the L signal would come out of the Center in conjunction with the left speakers when performing the left side tune..

So when played together through some magic that oabeieo could explain we would in a way derive the Dirac Virtual Center

Sighs.. patiently waiting for that Audiofrog unit.
 

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Audiofrog is working on a unit that can upmix stereo to surround sound including proper Center channel by signal steering via Penteo. No details on whether it will have fir filter capabilities.

There are a bunch of differences. First, in the matrix upmixers, the center is a summed L and R and the steering angle computer turns the levels of the channels up and down according to the calculated vector to maintain stage width. Second, the rears are a L-R signal.

In our Upmixer, the sound field in the stereo recording is separated into mono (same in L and R), Intermediate information (similar but not exactly the same in left and right--the sounds between the center and the left or the right) and differential information (only right and only left). The mono info is sent to the center. The intermediate and differential info is spread over the left and right, the sides and the rears--kind of like a horseshoe if you were to turn all of the dials to 11.

This provides great stage width, a stable center and no artifacts in the sides and rears.
Only Andy has the knowledge of when it will be out for retail. So until then I guess let’s not stray too far since this thread is for RePhase and Dirac Live.

As far as the DDRC-88A, it does not have an up mixer to my knowledge. It can perform Dirac Live calibration to 8 seperate channels. I’m curious to know how many taps per channel? Same as DDRC22 divided amongst 8 channels or is itvmore like 4 DDRC22’s in one?
 

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Discussion Starter #35 (Edited)
Elgrosso is right , Dirac isn’t release anything for car as of yet

As far as a center ch. I would simply buy a logic 7 up mixer and insert that in the chain if you want a true center that has the proper decoding for what you want to do.

If you have a ddrc 22d before the helix i would run the correction without the center ch turned on (rears ok) so it doesn’t mess with the 1st measurement that sets delays, but also would leave the eq work improper. I would just use rew after your Dirac run and eq the center in the helix to match the response of the left and right summed response . Meaning play both left and right together, use PN and do a moving mic average and just manually eq the center to match that response down to 250hz.or so if tiny center at least to 400.

For your center you will want to insert a toslink splitter and get a signal split before the ddrc so you can add a 2x4HD or DDRC24 to not be a part of your Dirac run , you won’t want to try To upmix a Dirac correction as left and right will have different electrical responses respectively to the original source and up mixing is dependent on phase of left and right so that can’t be altered to get a proper upmix.

With that dsp you could get the center to shape the way you want, obviously your upmixer would have to go between the source and any Dirac


The ddrc88A or BM is ideal for a updstream upmixer as it’s seperate corrections tied to a single target. That how I would do it

Ditch the helix , use a ddrc88xx and a logic7 upmixer before it. Pretty easy and would be one hell of a sweet setup, and the BM add on you can get Dirac to use all the channels to make a dedicated sub output and also mix portions of each correction to any channel,
You could mix 25%of left correction and 25% of right correction on top of the center correction if there’s massive differences in the drivers FR pre correction and mix parts of each correction and send it to other drivers to blend the sound if the locations are radically different as far as sound characteristics go.

The same exact acoustic response can sound completely different if one loudspeaker is playing let’s say into glass and another is playing into carpet or a soft padded seat.....
So the 8&BM allows you to mix each Dirac correction onto other drivers to balance that in 1% increments. Pretty sweet. The combo of mixed corrections and seperate Dirac targets on each ch but tied to a single target would give you the ability to make it do whatever you want as far as how it sounds.

But again as far as upmixing , again just needs be done upstream than run corrections on each respective channel.
 

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Thanks!!

I couldn’t discern what effect would occur when performing the Dirac Live calibration while a mono sum center speaker was turned on.

It’s interesting you say to ditch the Helix. I’ve actually been toying with the idea of fitting a surround upmixer unit in my glove compartment. I snagged an Outlaw Audio 975 from eBay that I was thinking of powering off a mini pure sine wave inverter upstream of the DDRC-88A with the BM plugin.

If you can fit and power the Outlaw unit it opens the door to:

-Analog and digital inputs including Optical,coax, and hdmi (perfect for iPad or tablet source).

-192 kHz 24-bit DAC's for each of its 8 output channels that can be processed to a surround sound matrix galore such as:

Dolby TrueHD, Dolby Digital Plus, and Dolby Digital decoding

DTS-HD Master Audio, DTS-HD High-Resolution Audio and DTS decoding

Dolby Pro Logic IIz, Dolby Pro Logic IIx, Dolby Pro Logic II, and DTS NEO:6 processing/upmixing from Stereo in either Movie or Music modes

It can even set crossovers for each channel. Very tempting. As is your ms8 Logic 7 route. I’ve only heard BMW’s modified implementation of logic 7 for their vehicles. Not the true Lexicon or Harmon Logic 7 upmixing that’s often touted as the best.

Do you know how many taps are available to each channel on the DDRC-88A?

In regards to the DDRC-22D + Helix Route, could I perform the calibration while Helix sends R-L and L-R signals to the rears? Or is it best to perform the calibration with a stereo rear and then modify the matrix post calibration?
 

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Good stuff, thanks for posting. I'll have to download RePhase and play with it.
 

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Discussion Starter #39
So I’m back (after a year of hiding ) :D

So rephase is going good a new release is out 1.4.1
It has some new features worth checking out.


However on the topic of phase correction and phase manipulation I would like to chat about all pass filters

Many of your dsps have all pass filters and maybe I can shed some light on there operations


What is an all pass? It’s a filter. There’s a few different types , I’ll talk about 1st and 2dn order all pass (for audio)

So let’s dig in.

First we need to discuss a few things. First the complex plane. The complex plane is an imaginary line that is where each pole on the filter is placed. Poles are exactly what they say. Poles like positive and negative right....not exactly but close. If a input and output signal have a shift in phase to or more than 360° another pole could be said to be added , but in coefficients it’s dosent quite work like that , it’s the calculation that can add poles
For instance a filter with 90deg would have one pole at -1/rc and a zero at rc. Which makes them an inverse of each other. So the delay at the frequency would add the pole.

So in a 2nd order filter for instance the shift is frequency dependent. And the shift center frequency is at 1/4th the wavelength, which is called quadrature. So on your all pass control which is most likely a 2nd order all pass, the frequency you pick is when the input and output are 1/4th wavelength apart or 90° respectively . The Q of the all pass says how fast the input and output rise and fall from 0° to 360° .

So when you add a all pass filter , the signal goes in , and when it reaches its center it is like a mirror effect putting the output to 360° , so if it goes to 360 at lets use a center of 400hz , that means the input and output have a one cycle delay of the wavelength of 400hz right? Almost, it has a delay, but not quite a full cycle, it’s a quarter cycle delay between poles. So what’s the wavelength of 400hz 33.9 inches or 2.51ms a quarter of that is .62ms. So that added group delay can be a added or subtracted or by 1/2 from the input or output to “alignment “ with another crossover or speaker, but in a car , that’s not what ere listening for.

You could certainly measure your car, window the response and do all that playing around with measurements and apply the all pass and it could definitely make things worse sounding.

I would suggest using an all pass filter as something you can listen to real time.

So where do you place these all pass filters ?

You have to get to know how your car behaves. It’s not something rew can listen for it don’t know if your stage is high or the vocal is high and center. Is there that one annoying frequency that pulls your phantom center to the left or right, or is there a severe combfiltering notch that just won’t quit eating up all the ambiance and sucking the impact out of your system. An all pass might be a great help to solve some of these issues for one seat.

Knowing the all pass goes “in phase” at 360 degrees which is essentially zero degrees with added group delay, you can move only some frequencies phase in a line, how steep that line is is the Q. A Q of 50 would move the phase from zero to 360 inmaybe a span of just a few frequencies where a Q of .5 will slowly shift the phase over the span of maybe entire octaves depending on how high or low the center is placed so if you have a deep combfiltering notch at 350hz or 400hz or 500hz (wherever that critical midrange and midbass notch appears) you can add an all pass to one of the two speakers and play with the centering and Q and it may or may not cooperate with what your trying to do. There’s a lot of different things happening) if it does help great! You should now have either reinforcement at that frequency or you have shifted the aural cues on that frequency only to help support imagining and centering. Another trick is to use the all pass in the peaks to drive them out of phase , which will subsequently help fix the dips which are out of phase (that’s why there dips) so if everything is out of phase, it’s actually back in phase, sometimes a simple invert polarity switch along with an all pass is just what is needed.

I know the Macaroni .....I mean masconi and the JLvxi have all pass so does minidsp and a few others. Use the all pass , do it real time and listen.


Another cool thing with all pass, you can apply it at the knee of a crossover, as the crossover rolls off the phase moves , if you add a all pass at a frequency that is let’s say 15° from zero (could be 1db down or so on let’s say a high pass) then it would shift the entire pass Band by 15° +360 . Doing that and a little trickery between inverting the polarity you could shift the phase of the entire left or right channel , by small increments, that along with signal delay can really make them dash pods come together just great....


Or cascade several all passes with delay between them for reverb for that rear fill you always wanted to add space to ..... possibles are endless.....
 
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