[ProtegeManiac]

 
  I'm looking at the Audison processors for a Tablet/ipod as HU application and Im convinced they would sound superior to anything not using Optical.

 
It would really be best if you talked to a custom installer for this, that way they can wire it up properly. There might be some kind of relay circuit that has a switch to enable/disable charging, without plugging in to the 12v lighter in the cabin, keeping everything neat.

 

[WhiteKnite]

I highly recommend the MiniDSP if it works with your Nexus 7.  I use it just for the audio processing in my car and don't even use the DAC.  You can run Room EQ wizard off a laptop if you pick up a good calibrated measurement mic, and get very close to a pro SQ system fairly easily with the right setup.  If you don't enjoy tinkering and tweaking the audio or aren't electronically inclined you might want to get it done professionally for 3 times the price though.  I enjoy it so I did the full install, soundproofing, and tuning myself.  I went with a mirrorlink touchscreen headunit though and have regretted not going with a full tablet ever since...

 

[joe]

Guys -- let's be civil here.

 

[rebar]

Again, I apologize wrong forum.  But you guys know what your doing..
 
Can someone explain how to bypass the DAC of the nexus so I can send digital to the bitone and let it's DAC do the work?

 

[ProtegeManiac]

 
Can someone explain how to bypass the DAC of the nexus so I can send digital to the bitone and let it's DAC do the work?

 

You'll need to use a USB audio to SPDIF converter. It basically functions like a DAC, and some of them can work off the power the host device can put into it through USB. Check the Android DACs thread, at every fifth page (ends in 5 or 0) there's a link to the updated list of Android devices and known DACs. Some of the DACs listed have USB to SPDIF converters built in, while dedicated converters are mixed into the list.

I've seen an iPad Mini used in this fashion but with a Schiit DAC (owner had the USB to SPDIF converter before he bought the Schiit, so that basically saved him some cash on the USB input, not to mention he has something that he's sure works with his tablet).

 

[rebar]

   

You'll need to use a USB audio to SPDIF converter. It basically functions like a DAC, and some of them can work off the power the host device can put into it through USB. Check the Android DACs thread, at every fifth page (ends in 5 or 0) there's a link to the updated list of Android devices and known DACs. Some of the DACs listed have USB to SPDIF converters built in, while dedicated converters are mixed into the list.

 
Thanks! 
 
I might need a pro as my eyes just glazed over starting to read that Check the Android DACs thread,  way over my head..

 

[ProtegeManiac]

  Thanks! 
 
I might need a pro as my eyes just glazed over starting to read that Check the Android DACs thread,  way over my head..

 

If you're referring to a car audio pro, they might not necessarily understand the USB audio thing - you're gonna need someone who understands enough of Android/Linux. Not necessarily a programmer, just ask in that thread if there's any USB to SPDIF converter that's known to work specifically on your Android. Past that, you can check if your Android works on generic drivers, and if it does, then check the list of those DACs that do on the list and see which of them are, or have an, SPDIF converter built-in and won't require a separate power source.

 

In any case the goal will be so the USB audio signal passes through that converter, after which you can use either optical or coaxial to get the digital audio into the BitOne. Fortunately, and unlike the typical car audio processor, it has both. I've always wondered what it was that made optical the default choice (aside from proprietary connections, like Ai-Net) when it's too easy to break the glass fibers in an optical cable, what with the twists they have to go through when installed in a car. I mean, were all 75ohm coax cables back then as stiff as what is used on cable TV?!

 

[DJ The Rocket]

First off, you're better asking in car audio forums for two reasons: safety and if this is also your goal, proper sound quality. I'm going to guess the second is a priority because you are not saying that this is purely for convenience and you're willing to go out and use a DAC and line out converter. I'll address the tablet later and deal with your use of quotation marks up there first - even if you don't want to go as far as I describe, at least you'd get why they are there and what you should be really wary about.

Now, here's the reason why there are professionals, or more accurately, pros (who run shops), non-pros* (competitors) : you can install a $10,000 DAC in a car and power it somehow along with equally eyeball-gouging amps and speakers, but in no way have you managed to even scratch the surface of what really matters in a car audio environment. In sense, car audio is more like pro audio than home audio considering all the tweaking you have to do to minimize the negative effects of the car's cabin as your listening environment. If you have a speaker system at home, you can try this too. Place your speakers directly facing each other, then sit closer to the left or right speaker. Switch on another audio system in another room, like a TV, with its back a wall adjacent to that listening room. Now, replace the speakers, DACs/CDPs, amps. Did the sound get better? Nope, not really, because:

1. You're not sitting in a spot equidistant between the two speakers (and in a car your tweeters on the dash can be, what, at least 18inches away from the midwoofer low in the door)

2. You're sitting off-center, in a spot that is not equidistant to both speakers

3. Your speakers are directly firing at each other, with no sense of proper toe-in

Now ask yourself: does anyone actually listen that way at home? Have you ever seen a home set-up like that? No, not really, and this is where those "professionals" come in. They will install everything so that instead of throwing money at expensive gear without targeting the acoustic realities in a car cabin, they will allow you to split your money properly on gear and installation. Think of this as acoustic treatments in an audio room at home, except this time you're addressing noise as well as time alignment and phase issues. They will install, at minimum, the midwoofers so that they can be properly dampened and the front of the cone isolated from the rear of the cone inside the doors (and minimize the most basic type of cancellation) and tweeters at an angle to improve the center image and minimize glare for the seat nearer to each side tweeter. Past that, they might install the midwoofers outside the door panel, if not on the kickpanel, getting rid of cancellations caused by the soundwaves from the front of the cone bouncing around behind the interior door trim. The subwoofers also get installed in such a way as to minimize room modes depending on the car, as well as for aesthetics if you want or if you're a tweaker have the amps and processor if you have one installed in such a way that you can easily reach them.

Past the proper installation of your speakers, you could work on using a time alignment processor - this allows for a DSP to introduce custom delays for each tweeter, each midwoofer (or midrange and midbass, if you're using a 3-way system in front) relative to each other and the subwoofer at the back. Installs and time alignment (and other processor settings) done correctly, you can have along the dash properly centered main vocals with every other instrument spread out relative to it as you would on near field monitors, with the subwoofer's output (with the lowest safe high-pass setting in front and lower low-pass for the sub, so all it does is provide the low freq reinforcement for the notes) seemingly coming from the front despite being 4ft in the luggage compartment behind you.

Basically, what I'm saying is that it actually is a bad idea to ask about car audio outside of a car audio forum (unless I'm going to intervene), because it is inherently more similar to pro audio or professionally-installed home audio/HT systems. Worse still is asking about car audio in a headphone forum, where many of the regulars with authoritative reputations from high post counts don't even deal with room modes (and some don't even know what that is) by nature of headphone listening, and attribute changes in sound to "burn in" than earpad wear, hence they'll tend to think of lossless and GIGO instead of actually dealing with the acoustics and safety issues. At minimum your processor needs to have some kind of auto-tune using a reference disc, but back then we were manually measuring the response, and then USB mics just made that a bit easier since we can have the real-time analyzer running on a laptop (and we're not even the "pros" who do this for a living, just some people who would rather get stuck in traffic on the ground than pack into a sardine can on the rails above or below). The usual GIGO principle for the signal chain and throwing money at DACs isn't going to address what a proper DSP can - no ESS9023 will perform in a car better than simply addressing the inherent issues. Processors nowadays even take the signal off a factory-installed system's amp (so as not to fess around with the interface on the dash or lose GPS), using a high-level input with an auto-ranging volume control as in the Alpine processor with Audyssey that I just traded in an older HU+processor for. Even 320kbps through a time alignment DSP on a properly-installed system can sound better than expensive speakers just screwed in wherever they fit playing lossless/CDs.



This is the primary problem you are dealing with past the noise floor. Top view shows the different distance to each tweeter, midwoofer, and subwoofer (color coded); side view at bottom shows the height differential (color-coded) in midwoofer-tweeter height, plus the problem with how a sub in the trunk can be reinforced or reduced by cancellation depending on how many paths it takes into the cabin.











This is basically what the normal imaging in a car "looks" like: called a "rainbow image," as the driver you have the driver-side of the soundstage image with "bigger" and more up-front instruments vs the passenger side (and vice versa).





Using the balance control will only reverse that.













Here's an image just to illustrate why it got that name.







Now these are what you need those "professionals" for, unless you can DIY fiberglass.

Of course, yes there are things you have to look out for - not every professional installer is actually "professional" in conduct, nor transparent - they have to run their businesses and if it's a general car audio/electronics shop they are also dealers who have to push their own products. Car audio forums here divide and recombine and repeat thanks to heavy-handed marketing. For someone who doesn't fully understand all these, this is why car audio forums are also important - they will at least explain these acoustic issues better, and best of all, www.diyma.com. While that forum might sound like it's dedicated to DIY-ers only, the thing is they are less susceptible to marketing since the forum doesn't even have huge ad banners diplaying BeWith, DLS, Hertz, etc. Learn there, and they might be able to point you in the right direction when you have work done on your car - basically, you need to find an installer who is likely to tell you what I already did: split your money between the gear and the installation properly, instead of pushing more expensive $h1t and then just sticking them in there.

Over here an Accord once won the "budget" category in an SQ competition using an old Alpine HU+processor, cheap $35 speakers and a $40 subwoofer (from what essentially is a factory that is a bit like Parts Express) along with a counterfeit $40 Alpine subwoofer amp (why they let these compete still escapes me). How did he do that? He basically spent nearly all the budget limit on the receiver+processor, which also had a high-current built-in "V-Drive" amp that needed its own connection to the battery. He then used the internal digital processor to apply crossover and time alignment settings, running the front speakers off the cleaner (and authentic) Alpine HU's amplifier and driving the sub with the counterfeit amp. He undercut the budget limit and still imaged a lot better than the cars one category up with expensive speakers and "Burr Brown DAC"-equipped DVD receivers (yeah TI/BB DACs were a thing in the past decade) sporting huge multichannel amplifiers.





*Meaning those who take their own cars to EMMA and IASCA events, even against the people who built their cars (and sometimes they actually win against them, and it's still a plus to the shop that did the work, since the shop gets credit for isntalling everything properly)





------------------------------------------------------

Now, as to your installation specifically, you're going to have to deal with two problems when you permanently install the tablet in your car (and again arguably this is one of the reasons why you need a "pro"): how do you charge it? You could use an OTG and USB hub, then an inverter, but then be aware how easily this can be dislodged. However I've heard of them being installed properly, so again look in DIYMA - there might be kits or at least some ways to manage those problems.



Second, about bypassing the HU - how do you control the volume? You either use something like a UDAC, so it'll have a potentiometer hence a pre-amp output, but then how do you mount that? Again, unless you know what you're doing vis a vis the electronics as well as fabrication, you'd be better off just leaving this alone. Audiophile systems in cars built around a tablet instead of an HU are configured in two ways: either they are just a remote interface for a miniPC installed elsewhere (Google "headless audio server") or they run into a USB DAC. Either way, in both cases they employ some kind of integration processor, which would have otherwise worked on their stock sound system (as I described above) - the only real gain being that the tablet or headless PC+tablet can play FLAC.

There are easier ways of going about all this. First, if for example your car has GPS, then just install an integration processor - some can use the stock volume control while others require that you install one that connects to the preamp on the processor (mine can do both, depending on the source - high level inputs can retain the use of the receiver's pot).

Second, if you have an older car (still has the DIN slots, or converter kits are cheap and don't really affect the other controls, aesthetically or functionally) but don't care about GPS nor that much for SQ, you can get a proper media receiver - Clarion has one that goes for around $60 on Crutchfield and can use portable storage devices and 320kbps music. This will still have basically proper DACs and output stages, without the hassles of how to charge a tablet or USB cables getting detached. You can still use the GPS on the tablet via the AUX input on the HU if the app has voice commands like in car GPS systems.

Third, if you have an older car (still has the DIN slots, or converter kits are cheap and don't really affect the other controls, aesthetically or functionally) but want SQ as well (and again, the option to hook up the tablet to the AUX input if you want to use its GPS), then get the Alpine media receiver (around $200 to $300) and the PXA-H100 processor (around $150; even cheaper on eBay). These work together seamlessly using Alpine's Ai-Net protocol, originally used to control and transmit digital audio from the CD changer. This time the signal goes the other way and not back: digital audio leaves the HU+storage device, goes into the DSP, gets split into the appropriate outputs, then goes into the amps and then the speakers. You also control the processor from the HU itself, unlike integration processors that have buttons on them (which is inconvenient, especially if you already installed it, like below one of the seats) or a laptop (in which case if it's already installed you still have to reach under and plug in the USB cable).

Basically, what I'm saying is that bypassing the HU is too much work with too many considerations, and despite what money you'll throw at the DAC, it's not bound to sound that much better, especially if you're still dealing with the problems inherent to sitting off-center in a small space where the tweeters, midwoofers, and subwoofer are far apart from each other mounted on flawed baffles as well as having a high noise floor.

Fantastic, all-time great post! I'm working on building my first car stereo system, and I had it in my head to try something similar to the OP. This has helped me think things through more clearly. It also shed some light on what a "good" head unit does for you. The Accord budget class competition anecdote was especially illustrative.

@ProtegeManiac if you're still around these parts, where do you think the sweet spot on the diminishing returns curve is for head units?

And how important is DSP in car audio, really? How much will you gain from a mid-level HU's DSP over a regular two channel signal going through quality crossovers at intelligently chosen crossover points?

It's surprisingly hard to find good answers to these questions, even in the proper forums for it. (Obviously I didn't expect to find anything here of all places, credit google for that).

 

[ProtegeManiac]

@ProtegeManiac if you're still around these parts, where do you think the sweet spot on the diminishing returns curve is for head units?

The best mainstream, non-flagship, no screen HUs are your best bet for having at least almost as many DSP options as the video-capable units that have similar features (these aren't as common anymore) without spending 3x or more for the flagship audio-only HU that comes in a copper chassis.

And how important is DSP in car audio, really?

I'm going to assume that, unlike 300 or so people, you're not driving around in a Maclaren F1 or an //////ALPINE show car.

Sit in your car. Your driver side tweeter is less than 1m from you, your driver side midwoofer is around 1m away from you and lower, then you have the passenger side tweeter and midwoofer at roughly 1.5m away from you, and the subwoofer is around 1.5m behind you.

Now go home and listen to your system. Do you have your chair closer to one speaker? Is the tweeter on that cabinet 0.33m away from the midwoofer? Is your subwoofer behind your chair? On your headphone system do you have one earpad 3in thicker than the other earpad? No? That's what you need the DSP for.

How much will you gain from a mid-level HU's DSP over a regular two channel signal going through quality crossovers at intelligently chosen crossover points?

Your regular built in crossovers aren't any better than what you'd find on car audio amplifiers, just with the convenience of being able to change the settings without reaching for the amp. And a proper DSP has more than that - it should have 3-way crossovers and 6-way time alignment at least, plus additional preamp gain control.

In my car I have the tweeter high pass set to 4000hz at 12dB/octave to reduce midrange glare especially from the driver side tweeter (which are also mounted at a toe-in and upward angle), midwoofer bandpass set to 2500hz at 6dB/octave to gently reach up and meet the tweeter, and at a high pass of 70hz to put the hard upper bass squarely in front, with the subwoofer at 50hz. Gain structure has the tweeters getting a -4dB preamp signal and 0dB on the amp to compensate for the tweeters' high sensitivity, while the midwoofers are at 0dB and roughly 1/3 amp gain; subwoofer is set to 0dB on the DSP (I crank this up to +6dB if I play any bass-oriented music) and roughly 12:00 on the amp. Each tweeter and midwoofer are time aligned to have their output arrive at my ears at the same time as each other and the subwoofer.

 

[DJ The Rocket]

@ProtegeManiac I've been reading a little more about this, and I'm sold on the benefits. However, I only just realized that this is important: 90% of my music is played through the AUX jack.

But using the AUX input on a decent deck means running the signal through a DAC, ADC, DSP, and another DAC. Loading music to a memory stick is one workaround, and that's a great solution for the occasional long road trip, but unrealistic for daily use. That leaves Bluetooth.

I feel like I've come full circle here: I was looking for alternatives to a HU in the first place because I can't find a single HU with USB DAC functionality! That should require just a minor tweak to the HU software because all of the hardware is already there. But does something like this exist? A smartphone doesn't have the hardware to do the DSP on board without using the USB port, which is the entire problem.

Short of that, I would need a HU that passes the AUX input along to the amp/preamp untouched. Does any aftermarket HU allow that? I know my stock HU passes the AUX signal untouched, because modified it that way.

So unless I suddenly become the kind of person who plans his music playlist ahead of time, do I have any options at all? Is the stock HU I already have my best choice? Feels like anything I do is trading one problem for another.

Am I missing something? I have to be, because this Catch-22 I'm caught in is too stupid to be believable. I knew building an SQ system without being super deep into the scene would be challenging because everybody thinks they want SPL, but this is ridiculous!

 

[chillaxing]

Headunits now a days are compatible with android and iOS. Just plug inthe cable, choose thw option, and it will tuen your phone into a storage device. You still get all of thw phones functionalities. Checkout pioneer headunits. They have a built in dsp in them too. Not as good as an outboard, but if your not joining comps or if ypur just starting, they are a good starting point.

https://www.pioneerelectronics.com/PUSA/Car/DVD+Receivers/AVH-X391BHS

Oldie but goodie

https://www.pioneerelectronics.com/PUSA/Car/CD-Receivers/DEH-80PRS

 

[ProtegeManiac]

@ProtegeManiac I've been reading a little more about this, and I'm sold on the benefits. However, I only just realized that this is important: 90% of my music is played through the AUX jack.

But using the AUX input on a decent deck means running the signal through a DAC, ADC, DSP, and another DAC.

Again, don't get caught up in the GIGO process. The car has bigger problems than a pure and short signal path that only a DSP can fix. That's why DSP units now are designated sometimes as "integration processors," ie, they integrate with the existing stock system. They're designed to take high level (speaker output) inputs and run it through ADC, then the DSP to get around not having a Maclaren F1, then through the DAC and out to the amplifiers.

Loading music to a memory stick is one workaround, and that's a great solution for the occasional long road trip, but unrealistic for daily use. That leaves Bluetooth.

I really don't see how having a stick sticking out of the dash that you can see the contents on the dash itself would be a problem compared to using BT with a smartphone. When I was discussing the idea of using a tablet what I was talking about was how many cars now have the tablet mounted on the dash itself as a replacement for the HU, then feeding a signal to a DSP unit that you can just tune with a laptop and then leave it wherever its installed.

I feel like I've come full circle here: I was looking for alternatives to a HU in the first place because I can't find a single HU with USB DAC functionality! That should require just a minor tweak to the HU software because all of the hardware is already there. But does something like this exist?

What exactly do you mean? A lot of HUs have a USB port to use a storage device, even a smartphone, and some of the newer 2-DINs touchscreen HUs even use Android and can run Spotify if you have a WiFi hotspot in the car. Not like Tesla natively equipped with a tablet that has its own internet connection.

A smartphone doesn't have the hardware to do the DSP on board without using the USB port, which is the entire problem.

Actually they can, the problem is the DSP on the smartphone isn't equipped to output a six channel signal with 3-way crossover and 6-way time alignment since it's designed for two channel use with a symmetrically aligned seat (or head).

Short of that, I would need a HU that passes the AUX input along to the amp/preamp untouched. Does any aftermarket HU allow that? I know my stock HU passes the AUX signal untouched, because modified it that way.

DEH-P80RS has USB input and it own Network mode processor. Just not sure if iwhen a smartphone is hooked up it may just use the smartphone as a storage device, so streaming services might not work.

If you use a tablet with USB output, you can either use a USB DAC to feed an analogue line signal to a DSP unit (again, don't get caught up on the GIGO principle because your car not being a Maclaren F1 has bigger problems than that), or or use a USB DDC. Problem with the latter option is that USB powered DDCs are USB to coax, and standalone car audio DSP units use toslink. If you can find a way to run a USB to optical/toslink DDC in a car then that should work. Just make sure to keep the optical cable stationary so the glass fibers inside don't break, since rewiring a car system is a PITA.

So unless I suddenly become the kind of person who plans his music playlist ahead of time, do I have any options at all?

Tablet to USB DAC or DDC to standalone DSP to five channel amplification to 2x tweeters, 2x midwoofers, and 1x subwoofer on the mono channel.

Pioneer DEH-P80RS with several USB sticks containing 320kbps (AFAIK it doesn't run FLAC, but again, you have bigger problems in a car than that) if you can still find one.

Is the stock HU I already have my best choice? Feels like anything I do is trading one problem for another.

Isn't that always the case? You want better sound quality, you have to spend on a bulkier system with an open headphone and amplifier at home over throwaway earbuds and a smartphone.

Am I missing something?

Installing a tablet on the dash with a USB DAC or DDC to a processor which feeds five channel amplification that drives the speakers?

Just using several USB sticks with a P80RS, contents divided based on genre or artists alphabetically grouped?

I have to be, because this Catch-22 I'm caught in is too stupid to be believable. I knew building an SQ system without being super deep into the scene would be challenging because everybody thinks they want SPL, but this is ridiculous!

Well if you go into DIYMA you'd find people who go into the SQ competitions of EMMA and IASCA imaging the subwoofer up front than trying to crack their windshields.

https://www.pioneerelectronics.com/PUSA/Car/DVD+Receivers/AVH-X391BHS

This one has confusing specs. It says it can do Network Mode, but crossover specs only list "HPF, LPF" - doesn't say if it can do Bandpass on the midwoofer.

Time alignment only accounts for seat position, doesn't take into account distance between tweeter and midwoofer or enough fine tuning.

 

[chillaxing]

Been using the pioneer double din (on my second) for several years now and it does the job well enough for a newb. He'll be able to get the stage dialed in to the middle of the windshield with the time alignment.

Network mode is basically a 3way setup, it has the mids crossover point. but you do lose the rear speakers in network mode. He doesn't need to be in network mode and can use component sets and not worry about xovers and still keep the rear speakers for occasions.

Im strictly a bt user in my car and never play flac. With all the road noise and your attention on the road, your not gonna be able to tell the difference. This is with my car fully sound treated too. So yeah... Don't get to caught about the whole flac thing.

The op is a newb, and car audio can be intimidating. to me, its the hardest environment to tune music. Im just trying to keep it simple for him for now.