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Discussion Starter #1
Got the measurement mic and a Marshal Mic-Mate (with phantom power) ready to go...



As some of you know, I use a carputer in my car, and it's doing my active crossover and all my DSP to my 2-ways...

Currently, I'm using a variety of plugins the accomplish this...basically, everything is done manually, as far as measurements and values are concerned...here is what the crossover plugin looks like...



But now, I'm going to use a program called (((Acourate))) to create Impulse Response files, to be loaded into Voxengo's Pristine Space...and THIS is the only VST plugin that will be needed...

Have a look at what Pristine Space looks like...



You can see the simplified routing with just the one plugin.
I'm continuing on using all the LEFT channels as my lowpass and all my RIGHT channels as my highpass...

As you look at this layout, keep in mind, each output (i.e. SoundOut) is a 6.5" driver and tweeter. SoundOut represents drivers side front speaker set, for example...

I'm using 4 'Slots'. A slot is a stereo IR file created in Acourate. One individual, and tuned IR for each driver/tweeter set.

Looking at the bottom half (output stage) of the plugin, it's configure like so...
Slot1 L/R (hi and low) are outputing the output 1 & 2...but also note, it's only passing thru LEFT channel audio to output 1 & 2. This is because, if you remember, output 1 & 2 are SoundOut, or drivers side front...
This way the driver and tweeter get the proper crossover, and only LEFT channel audio...

Slot2 (light green) is doing the same thing with it's own IR file, and only outputing RIGHT channel audio to output 3 & 4, which happend to be passenger-side front speakers...

And of course, the remaining 2 channels are rear LEFT and RIGHT, running their own IR files...

Now designing the IR files in Acourate takes quite a bit of know-how and work...I won't cover the procedure here...

BUT, it has the ability to make, starting with a crossover, up to 5-way design, using either Butterworth, Linkwitz or Neville-Thiele, up to 10th order!

Once you decide on what crossover you want to use, you take a direct mic measurement, called a logsweep, of each driver and tweeter (each enclosure will vary somewhat!) at a specified target frequency range, i.e. 100Hz to 3000Hz for the drivers...

Once you've recorded the logsweeps, it's time to Convolute them! Basically, this 'shapes' the output of each speaker to a flat response, within the confines of the crossover, in corrolation to each driver and tweeter. After you do this, normalize and correct for phase, you basically have a set of crossovers that correct the speakers to a flat response...

You could stop here, but Acourate allows for SO much more!

At this point, you might want to match the outputs of each driver/tweeter set. You make another logsweep, using your new crossover IR files, and record the drivers and tweeter seperately...
Load the two sweeps into Acourate, and instantly see any loudness differential. This is easily corrected with the normalize function.

Now your tweeters and drivers are outputing the same power...

Now your ready for 'room' correction!

With the mic setup in the listening position, you want to do a full range logsweep...you want to do stereo pairs together, so you run a sweep of the left channel, then the right. These can be manipulated (convoluted) together...
After you've corrected the front channels, you do a sweep of the rear pair, and make your corrections...
In this phase of the convolution, you also 'mark' the response in the time domain, for each tweeter/driver, and it makes adjustment of the time delay.

Once this is done, you use these files, and apply a 'difference' to the original crossover/driver response files...

What your left with is each individual speaker (8 in my case) adjusted for response, cross-over, normalization, time alignment and corrected to the listening space!

The IR files used in Pristine Space is a small WAV file, typically less than .5 second in length...
 

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Very cool stuff!
 

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Discussion Starter #4 (Edited)
Very intersting.

What kind of sound card are you using, and what kind of processing power is necessary?
I'm actually using 2 sound cards (well, 3...the onboard is used for mic IN and LINE IN for the HDRadio)...
They are 7.1 Asus Xonar sound cards...which gives me 16 channels.
I use 11...8 for the 2 ways, 1 for the subout and a pair for VUmeters...

From testing on my desktop PC, running 4 IR files thru 8 channels, CPU useage is around 17 to 20%...
With my old setup, I was anywhere from 20 to 40+%.

The car is a X2 AMD 2.2Ghz, which outta be ample...
 

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Discussion Starter #6
I plan on using a PC for my house audio as well, eventually...using this same principal of signal processing...

I'm thinking a kinda hybrid system...PC using optical output (instead of the cars analog) to a high-end DAC, then to a vintage tube amp...

Of course, with the ability to 'serve' audio from the in-house PC's thru Wi-Fi...
Possibly running Media Center, with a 7 or 8" touch screen as well...
 

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I'm actually using 2 sound cards (well, 3...the onboard is used for mic IN and LINE IN for the HDRadio)...
They are 7.1 Asus Xonar sound cards...which gives me 16 channels.
I use 11...8 for the 2 ways, 1 for the subout and a pair for VUmeters...
Wow! Thats a lot of channels.

I take it you're running 2 ways in each corner?

A normal car setup with 2 ways in the front and a sub would = 5 channels? This could possibly be done with 1 sound card?
 

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Wow, I'm really liking this idea. Amazing potential if I'm understanding correctly.

Could you describe a bit more on how the outputs on the sound card are configured? I realize each has its own crossover setup, but I'm assuming you just run each output into a reciever? Maybe an image if available.

Thanks a bunch for sharing this, I really like it.
 

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nice. I've been kicking the carpc idea around for a year or so now. Started getting more interested last week and think I'll give it a shot this summer. I'll have to start pinging you for advice. ;)

I am a bit confused... you said 2-way which shouldn't use 8 channels. :confused:
 

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Discussion Starter #10
Wow! Thats a lot of channels.

I take it you're running 2 ways in each corner?

A normal car setup with 2 ways in the front and a sub would = 5 channels? This could possibly be done with 1 sound card?
Yup, 2-ways X 4...
You could even run a pair of 3-ways up front with a sub for 7.1 channels :)
 

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Discussion Starter #11
Could you describe a bit more on how the outputs on the sound card are configured? I realize each has its own crossover setup, but I'm assuming you just run each output into a reciever? Maybe an image if available.
No reciever...straight from the sound card, to chassis mount RCA's and into the amps...
It helps to understand it if you forget about the whole typical L/R channel per jack configuration...
Instead, think of each sound card output jack as a hi and lo pass mono output. Kinda strange, but this is the awesome flexability of AudioMulch and ASIO drivers...
You could literally configure each channel however you want!

So, two sound cards and two amps for the main stage. I simply divided it so the driver gets a sound card and amp, and the passenger also gets their own sound card and amp.
So each output jack on the sound card goes to one 2-way, or one corner of the car...

Each card does a front and rear set...the drivers side gets only LEFT audio channel, the passenger sound card, RIGHT...

One of the outputs is sent to the sub amp, and on the other card, one of the outputs goes to the pair of VU meters...

Here is an earlier routing design I used in the past...it might make it easier to visualize. Remember, all the LEFT outputs (on the jack) are lo-pass, all the RIGHT, hi-pass...



And here, you can kinda see how each pair of interconnects go to each amp...one pair connects to one sound card, the other pair, to the other sound card...



I am a bit confused... you said 2-way which shouldn't use 8 channels. :confused:
2-ways yes, but remember, I have a front and rear setup...that's 8 channels right there, PLUS I need a sub out and I'm using a pair of VU meters up in the center console...

I s'pose I COULD of cheaped out and went with a single sound card and just patched in the sub/VU meters with a split, but that would of been just that...cheaping out! :)
 

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Could you break down the software that you are using and their purposes?

I noticed you mentioned Acourate to generate the test files?

I also see Audiomulch, Rubberfilter, and Voxengo.
 

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Discussion Starter #13 (Edited)
Centrafuse is the 'frontend'...

ASIO4All is what my PC is using for 'drivers'...of course, the hardware themselves need drivers...ASIO4All basically by-passes Windows mixer for a low-latency audio solution...

As far as the audio software, in order of delivery, I use Virtual Audio cable...
This is basically a pass-thru cable to AudioMulch. Because Audiomulch is outputing to my sound card jacks, my audio player needs somewhere else to send the audio signal, else it would just go thru and out the card without any processing!

So in Centrafuse, Virtual Audio Cable, or VAC, is my default sound device...Audiomulch picks up the audio from VAC, and then it's processed, then outputed to the output jacks...

Rubber filter is what I was using before as a crossover...this was all before I thought of using Voxengo's Pristine Space and IR filters as my all-in-one solution...

I then switched to LSFilter, which was a 4-way crossover able to handle all my patching with a single VST plugin, as opposed to two Rubberfilters...this took some load off the CPU.

Acourate is a powerful piece of software for creating the IR filters, as I mentioned, that corrects the speakers response, crosses them over and corrects for listening space...
There are some tutorials on the website...check 'em out!

(((acourate)))® - Room Correction, Speaker Optimization and Sound Improvement

Once you have your filter created, load it in Pristine Space, and your done! A single plugin that accomplishes all this!

On another note, I picked up a small tripod for mounting my measurement mic on...
I think this weekend, I'm going to do a logsweep and measure the speakers in the car! Then bring that data into the house and start off by making just my crossovers, then load it up in the car and see how I like it.
Once the logsweeps are done, and the speakers response is recorded and saved, it can be 'applied' to whatever crossover I wish. I just might try a few different types and cutoff points!

Once that's done, and I'm happy with the sound, I'll run a 'listening position' sweep, first with the front pair, then the rear pair, one at a time, and see what the response looks like...
This will be all the data I'll need to collect...
 

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just out of curiosity, you're using the behringer mic... which has been shown to be non-flat out of the box. Do you have a calibration for this so that the measurements you take with acourate are correct?
I can see a non cal'd mic totally wrecking your system; especially one that is used as a basis for all audio property settings.
 

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Thanks for the explanation, I'll be trying to digest it! I really appreciate you answering these questions.

AISO drivers are used in place of the manufacturers drivers? You get to bypass the dumb EAX and other effects filters? Is this how you end up with the low latency performance you're looking for?

Virtual Audio Cable enables any sound being played in windows to be directly routed to Audiomulch? Or only specific programs?

Acourate basically custom creates a filter/plugin for you? Took the place of rubber filter and LSF filter?
 

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Discussion Starter #16
just out of curiosity, you're using the behringer mic... which has been shown to be non-flat out of the box. Do you have a calibration for this so that the measurements you take with acourate are correct?
I can see a non cal'd mic totally wrecking your system; especially one that is used as a basis for all audio property settings.
It's not perfectly flat, no, but pretty close...
I DO have a calibration file for it from HomeTheaterShack forums, I just have to learn how to incorporate it! :)

Considering how a basic 'flat' setup would sound in a car, a calibrated 'room' would still be an improvement I think, even without a perfectly calibrated measurement mic...
In other words, a non-tuned car environment is probably WAY further 'off' than the mic would be, at certain frequencies, if that makes sense...
 

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Discussion Starter #17
Thanks for the explanation, I'll be trying to digest it! I really appreciate you answering these questions.

AISO drivers are used in place of the manufacturers drivers? You get to bypass the dumb EAX and other effects filters? Is this how you end up with the low latency performance you're looking for?

Virtual Audio Cable enables any sound being played in windows to be directly routed to Audiomulch? Or only specific programs?

Acourate basically custom creates a filter/plugin for you? Took the place of rubber filter and LSF filter?
Your welcome...

The ASIO drivers aren't a replacement for the hardware drivers...they are a replacement for the Windows audio mixer drivers...they by-pass the Windows audio I guess you could say...you still need to install the manufacturers drivers for the sound cards.

And yeah, all those nasty game effects and DSP crap on the sound card drivers are disabled...

The latency performance comes simply from by-passing the Windows portion of the audio control.

When you install Virtual Audio Cable, it's basically like adding another sound card, as far as Windows is concerned...except instead of outputing to speakers, it outputs to other input devices, such as AudioMulch...
In the Sound properties in the Control Panel, for example, VAC is listed under Playback devices...you simply set VAC as your default sound device, and this becomes your 'Speakers'...
So in effect, any sound played from Windows, goes to VAC...if it's not being routed to an output though, like in AudioMulch, you simply won't hear it.
Most good media players will let you choose which output device you prefer, such as Centrafuse...

The created 'Impulse Response' file that Acourate creates will replace ALL my current plugin, yes...I'll just need Pristine Space to load it, and let it do it's thing...
However, it'll only do for you what you create with it...I could simply make a cross-over IR file, and use that, or go all out, and do the works! It all ends up being the same file that you load in Pristine Space...
But don't be fooled, there is some work involved with Acourate!!
For example, to simply create a cross-over, and linearize your speakers, takes over 12 or 15 seperate steps...
 

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So in a nutshell you are running active, One sound card is completly devoted to the left channel and the other sound card to the right.

Could you use one 7.1 sond card and use the Front,Side,Rear Channels For a 3-way up front, and use the Sub for the sub ?

Is their time alligment issues ? or Because for lets say The Front Jack output you get two rca outputs (L/R), Have you tried it this way?

as far as sound cards i'm looking at

Creative Sound Blaster X-Fi Titanium Fatal1ty
ASUS Xonar D2
 

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Discussion Starter #20
Asus Xonar all the way!!! Creative only has a reputation because of the success of the SB16 many years ago...although the X-Fi processors is pretty nice, the hardware surrounding it sucks...
Maybe if you were going to use just the digital out, and setup some sorta processor along the way, but that kinda defeats all of this ^ :)
Auzentech are licensed to use the X-Fi chip...they are much better hardware IMHO.

So in a nutshell you are running active, One sound card is completly devoted to the left channel and the other sound card to the right.
Correct

Could you use one 7.1 sond card and use the Front,Side,Rear Channels For a 3-way up front, and use the Sub for the sub ?
Yes, you'd need 7 channels and the 7.1 cards have 8...with AudioMulch, you can configure any of the jacks/channels to do whatever you wish!

Is their time alligment issues ? or Because for lets say The Front Jack output you get two rca outputs (L/R), Have you tried it this way?
Not sure what you mean here...all my sound card jacks I'm using output to 2 RCA's. As far as alignment, I think with the ASIO drivers, and piping the audio thru AudioMulch, there is no noticeable alignment discrepancy....

I s'pose you could use the RCA's that come with the Xonar, but why would ya, when you can make your own? ;)
 
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