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TOPIC: Dirac live in car...a shared experience ;)

Dirac live in car...a shared experience ;) 4 years 5 days ago #31542

  • denver8me4dinner
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Hello,

I was hoping to help put together a info thread for Dirac use in car.

I would like to contribute info as well as a few others.
A friend of mine David aka grosso and I have been chatting quite a bit on another forum about our experience with Dirac live in car. I think jsconey2 is on here as well and would like to invite him to converse as well as anyone else that would like to ask questions or share experience as well and hopefully DevTeam chimes in too, especially when it comes to hardware questions and implementation advice ;)

Well leave it to anyone curious about Dirac please read all the pages and tech docs for different Dirac processors and educate yourself on the basics of Dirac and how the different models have different inputs and output topologies.

I use the Dirac live DDRC22DI which is a 2ch digital i/o box that requires a 5vdc power supply.

I use a 2A flush mount USB for car kit as a power source. It is a voltage divider which uses resistors instead of a switching power supply to power it and it works good. I also used a 12v-5vdc buck type switching power supply and it also worked just fine.

I use a toslink source that has volume embedded so I can control volume upstream. I can also control the volume on the Dirac box itself or through a wireless remote.

With minidsp wide selection of Dirac boxes one could use one or more ways to get Dirac to work in car. The use of a ddrc24 for a 4ch version, or the DDRC88 for a 8ch version.

All the multichannel Dirac boxes will have a different unique way Dirac will calibrate the system. Not all have the same algorithm, I will be talking primarily about Dirac live which is a 2ch version. So please educate yourself on the different Dirac calibration offerings available in minidsp.

The Dirac live room correction works well in a car environment, there are some things one will want to know when tuning with Dirac live and the way it responds to the car environment.

Dirac uses mixed phase filters. What that means is is will make linear phase and minimum phase filters to correct the room. I hope everyone already knows this by now but I'll give a short explanation between the two.

Minimum phase filters , in short mean when an amplitude change is made a phase shift occurs relative to the amplitude change.

Linear phase filters , in short mean a filter that either has an amplitude change and no change in phase or an arbitrary change in phase by use of a filter for phase. (Please see FIR vs. IIR filters explanation on minidsp pages)

With Dirac live it would use normal IIR we on frequency response corrections and FIR to fix phase response of system. Dirac may also use fir filters for some frequency domain issues as it sees fit during calibration.

Basically Dirac takes 9 measurements (as we should all know by now) what it does with the measurements really depends on a lot of things in the environment. In a car the reflections are so close to the mic position making Dirac a great tool for correcting this type of room problems.

The biggest problem which Dirac takes a look at reflections. Reflections create comb-filters in the acoustic space especially in a multiway. The reflections cause timing errors, amplitude errors, and reverbant interference in the acoustical signal. What Dirac can do is change the behavior of the speaker so these reflections are a part of the acoustical signal in a way that lessens the effect of these comb-filters.

These reflections and reverberations cause the system decay time to expand to a pretty large amount of time. As much as 50-60ms. As music is playing all these reflections are bouncing around the cabin and crashing into the original wave but depending on how many iterations of the reflections depends on what parts of one signal may crash into the newer signals radiating from the loudspeaker. This is time smear and in a car this time smear reverbant and it's audible. ;)

When you take measurements with Dirac the measurements are taken in one area in space than averaged. The measurement area is where it does it's magic.

In any room whatever sounds and reflected sound will eventually combine and at each different spot in space those combinations of summed energy will be different. Dirac hears only the summed info at each measurement point and forms its algorithms on the data collected.

One thing it does nicely is where someone may have dash mounted speakers and it can make the distortion caused by reflections linear.
Let's face it reflections are distortions to the original signal , if the timing is odd it will be nonlinear. Because Dirac can arbitrarily alter phase , the summed info that was at the mic location should be the listening position and therefore can alter the phase and calculate what is reflected sound and what is not and make the reflected sound a more linear type of distortion rather than a non linear. Of course it only fixes some of it in a car because some of the reflected sound during measurements maybe be louder than the original and Dirac wouldn't know because it only hears it's sum and has to calculate what it would assume are reflections based on timing differences and long post ringing in the impulse response. There are many technical document we can share that explain the in we workings of Dirac and discuss how it works in a car environment. All cars will have a different outcome so something's that may be true in one install may not be true in another.

As far as left and right integration Dirac does a fantastic job at getting left and right to have the same responce at the listening position. It is a calculated responce so it may vary a tiny bit on certain frequencies and there is definitely a learning curve as to understanding what it meant to do vs what you wanted based on the result it produced from your measurements.

It's definitely a assisted tuning tool and definitely needs the user on board to guide it a little with the use of pre Dirac tuning and post Dirac tuning via DSP.

One will basically want some extra dsp eq and level setting abilities at the least and some signal delay at hand.

You will want to set your car up the best it can be as far as level setting and pre tuning. If you prefer to let Dirac do all the eq work (which sounds amazing) you will want a sober approach to level setting between channels in a multiway to best setup for Dirac to take measurements and apply them to your electrical signal.

One thing I have done was slightly over gain my midrange to bring up the parts that have narrow high Q nulls. As Dirac will ignore any high Q nulls and not try to boost in its filter. By bringing up the midrange about 6db so that the null is it's loudest before it sounds distorted is perfect and let Dirac make large cuts in the magnitude based on the target you set. In this instance , the target should be set to ride right near the bottom of each null (about +\-3db). That way it has the best change at total spectral balance. By lowering the target below the 0db line on the filter making portion of Dirac however many do under 0db is how much Dirac will be allowed to boost any parts of the responce without having the need to add extra db for boost via the input attenuation.

For example if my responce is -8db at 80hz and -4db at 250hz I would draw my target (if I chose flat) to ride at the -4db spot at 80hz and at the -4db spot at 250hz, allowing it to boost 80hz 4db and no boost at 250hz because it would intersect at that point.

I have had better results this way.
But let's discuss it .

This is part one to my multi part post. I will write more in coming days.

Andrew
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Dirac live in car...a shared experience ;) 4 years 12 hours ago #31603

  • bobc455
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Hi!

Definitely been thinking about this as I drive around., so it's great to hear your experiences on this.

One thing I haven't come to grips with... Should you take Dirac measurements with the passenger in the car? My intuition tells me to put the driver and passenger in the car when measurements are made (assuming you'll want optimal sound when your passenger is with you, and are willing to submit a bit of a loss in quality when your passenger is not with you)

-BC
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31618

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Almost convincing me to go to DIRAC plugin instead of doing manual work on 2x4HD.... :)
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31708

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Andrew

What a great long post full of great comments! :-) It certainly sounds like lots of hours went into that tuning..
We look forward to hearing more and seeing measurements maybe? I'd love to see how that worked out for you. Dirac runs some algorithm for their automotive section however it's not Dirac live from what I recall. It's another technology they provide to their automotive customers only... :-(

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Dirac live in car...a shared experience ;) 3 years 11 months ago #31723

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Was seriously ready to purchase the DDRC24 unit in my truck along with my CDSP6x8.... but I'm having so many issues with my DDRC88BM and static popping noises - and Tech support doesn't seem to know anything about this issue - Im holding off until they figure out whats causing it ( others are reporting this issue as well)

LOVE my CDSP6x8 and have no issues with that unit !! would love to up grade to the 8x12
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31739

  • grosso
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Yeah great thread!
rts100x5 wrote:
Was seriously ready to purchase the DDRC24 unit in my truck along with my CDSP6x8.... but I'm having so many issues with my DDRC88BM and static popping noises - and Tech support doesn't seem to know anything about this issue - Im holding off until they figure out whats causing it ( others are reporting this issue as well)

LOVE my CDSP6x8 and have no issues with that unit !! would love to up grade to the 8x12

If you can, a ddrc22di would be better with the C-sp, so you can stay digital all the way, has accessible presets and more taps.
But a ddrc24 works too (tried both).
And no noise for me, as soon as power is clean, with some rem-in etc.
Your 88 is in the truck?
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31812

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rts100x5 wrote:
Was seriously ready to purchase the DDRC24 unit in my truck along with my CDSP6x8.... but I'm having so many issues with my DDRC88BM and static popping noises - and Tech support doesn't seem to know anything about this issue - Im holding off until they figure out whats causing it ( others are reporting this issue as well)

LOVE my CDSP6x8 and have no issues with that unit !! would love to up grade to the 8x12

I mounted a speaker next to my Dirac box.
My popping has all but vanished.

Very strange ......:/

But whatever it works don't care.
No popping in two weeks and am happy.
Try it...stick a speaker next to your unit and see...
Ya never know. ;)
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31813

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Thanks DevTeam! :)

Yes lots of hours and lots of REW measurements
and listening to confirm Dirac abilities.

Here's a few....sub and subless tunes












image hosting 20mb
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31814

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It's not going to make phase flat everywhere

It seems as if it does everything it can mathematically to make it the best it can be with its limitations on hardware.

But don't let that scare anyone, it fixes all the big problems pretty good.

A cdsp and a 22di is a pretty sweet combo.
Haven't tried the ddrc24 yet but have 3 2x4HDs
Using them as fir crossovers.

I don't know if adding rephase crossovers and than adding Dirac causes any ringings , the impulse on Dirac graph looks like a dam mess compared to "the Dirac impulse "
Might be the poor listening environment, but sure does sound a heck of a lot better.
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Dirac live in car...a shared experience ;) 3 years 11 months ago #31838

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Andrew

These measurements are indeed very interesting.. Isn't it quite odd to see how a car measures vs a speaker.. :-)
That hill slope is quite pronounced on your target curve isn't it?

So overall, it sounds great?

Gotta say you got a really neat setup! Great stuff and thanks again for sharing all your findings for Car Audio + Dirac Live to the community.

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Dirac live in car...a shared experience ;) 3 years 11 months ago #31842

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grosso wrote:
Yeah great thread!
rts100x5 wrote:
Was seriously ready to purchase the DDRC24 unit in my truck along with my CDSP6x8.... but I'm having so many issues with my DDRC88BM and static popping noises - and Tech support doesn't seem to know anything about this issue - Im holding off until they figure out whats causing it ( others are reporting this issue as well)

LOVE my CDSP6x8 and have no issues with that unit !! would love to up grade to the 8x12

If you can, a ddrc22di would be better with the C-sp, so you can stay digital all the way, has accessible presets and more taps.
But a ddrc24 works too (tried both).
And no noise for me, as soon as power is clean, with some rem-in etc.
Your 88 is in the truck?

No my 88 is in my Home Theater My truck has the CDSP6.8
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Dirac live in car...a shared experience ;) 3 years 10 months ago #31923

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devteam wrote:
Andrew

These measurements are indeed very interesting.. Isn't it quite odd to see how a car measures vs a speaker.. :-)
That hill slope is quite pronounced on your target curve isn't it?

So overall, it sounds great?

Gotta say you got a really neat setup! Great stuff and thanks again for sharing all your findings for Car Audio + Dirac Live to the community.

Devteam

Thanks DevTeam,
Yeah it is finally getting somewhere.

Yes a car measures very unusual. The combfilters are to the extreme and absolutely brutal punishment to try to deal with.

I think we're just getting started with how much dsp can fix in a automobile.

No the impulse won't ever be perfectly clean and tity, but can be very fun and enjoyable.

I've been getting some sweet measurements, and getting fine tuning time in as well.

andrew :)





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Dirac live in car...a shared experience ;) 3 years 10 months ago #32071

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devteam wrote:
Andrew
Dirac runs some algorithm for their automotive section however it's not Dirac live from what I recall. It's another technology they provide to their automotive customers only... :-(
DevTeam

Is there any possibility to see Dirac in C-DSP someday?
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Dirac live in car...a shared experience ;) 3 years 9 months ago #32620

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I emailed Dirac asking if the car version is something I could purchase,

No reply ......


I think they are just selling Technoligy to be used in a OEM type factory amp/dsp combo.

They should bring a car version to market , he'll I bet mini might even entertain the platform for such device s as a firmware option for existing dsps .... I would think they would do that for us (hint hint, nudge nudge ) ;)
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Dirac live in car...a shared experience ;) 3 years 9 months ago #32623

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Why do you suppose the miniDSP 2x4 HD comes with an option for a DIRAC LIVE upgrade and a 12v power supply ??? I wonder...
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