Let's talk everything DSPs.

For the newer guys just jumping into this car audio game, you might have seen this acronym thrown around but not really understand what it is or what it means. I hope this thread will help clarify some things for you. "DSP" stands for Digital Signal Processor. Depending on which model you get, it's general purpose is to allow a much larger tuning capability over the typical amplifier pot switches and head unit options available on standard aftermarket audio gear. They aren't very expensive (for the most part), but the flexibility/adjustability they provide makes them mandatory for all high end builds. In fact, adding a DSP to even a basic system can increase sound performance exponentially.

So how does it work? I'm glad you asked. Here's a basic video to explain it's function. While the video shows a DSP used in a room setting, the same is true for automotive applications.

Personally, I use JL's TuN software included in all VXi series amplifiers. Now you pay a bit more for these amps, but the additional cost is because it has the DSP integrated in. This isn't always necessary, especially in bigger cars/vehicles...but for me in a Corvette...minimizing packaging was very important to me. ALso, the functionality of TuN is quite impressive to me. I like that I have 10 bands or parametric EQ PER CHANNEL. That allows me to adjust every driver with 10 bands, control time alignment, +/- decibel output, etc. Between the awesome functionality and super compact packaging, I gave VXi the nod for my install. Here's a quick video about a basic setup of a entry TuN program. He's using a 600/6 VXi...I run the 800/8. This make my system a full "active" 9 way system.

Active versus passive:
Put simply, "Active" means that you're running an external (or integrated) DSP to control the "slopes" or "filters" for all of your drivers or pairs of drivers.
"Passive" means that you are allowing the amplifier or HU to control the signal going to the driver. Usually, passive component speaker sets use an external "crossover" which is a mechanical device containing capacitors and other electronic devices that passively provide the slopes/filters for a driver set as a way to protect them from damage.
Please don't think "passive" is bad. There are some truly amazing passive component sets out there. And also, you can run both active and passive in a system. I maybe fully active in my ZO6, but I'm completely passive in my truck, and it sounds quite amazing in it's own right.

How do I "use" a DSP?
Typically, you need a RTA (real-time analyzer) with a microphone to see your systems "curve." What's a "curve" you ask?

This is a curve. This is a picture of one of the earlier attempts at audio nirvana from my ZO6. My setup has changed several times since this was taken. But it highlights the end goal of the DSP's function and purpose. This "curve" (the dark blue line on the screen) is a baseline for a sound quality standard available used in the industry. There are hundreds to choose from, and you can even make your own if none of the basic ones strike your fancy. The different colored lines on this chart depict the different drivers actual output and how they line up with the desired target curve.

I believe that's enough to break the ice on DSP's, and I hope I wrote this vague enough to spawn questions...so let the chat being!

 

You just couldn't wait could you, LOL! This is a great idea, to dive into everything DSP. You made a couple great points in explaining the difference between an active and a passive system. Active systems have been around a lot longer than you might think. I did a 100% active build in my '85 Thunderbird back in 1986 with Boston Acoustics components, Mids and separate tweets in the door panels, and Three way in the rear deck with mid-bass, separate midrange, and separate tweeter, with four 8's firing into the back seat. This was all fed by an Alpine active dividing network and Alpine amps. Guess what it didn't sound that great or at least as great as I thought it would. If I could've hopped into the Delorean and gone back to the future, grabbed me a good DSP unit and a laptop, I bet it could have sounded a hellluva lot better. My point is, many forget that 90% of home speaker setups, I mean high high end setups, too are multiple drivers with a passive crossover network. Yes, there are active systems, also, but some of the most beautiful sounding speakers in the world are passive. So it stands to reason, as Ronin points out that you can still have a fantastic sounding passive system or passive/active combination. If you simply have subwoofers and using the Xovers in your head unit you have a partiallly active system using the electronic Xover built into the head unit and possibly the head unit's internal DSP, albeit not as versatile as an outboard.

I am using the built in DSP in my Kenwood but a good DSP is on my short list, along with updating my amps. Now who has some experience with these babies to steer a guy in the right direction? Ronin, what's your opinion on the various offerings out there?

You bring a whole new meaning to flattening the curve dude!!

 

Well, because I've got a few dozen hours behind the computer with TuN...I like how versatile and well packaged it is. It's also switchable on the fly between presets. You can also have up to 20 presets (which is a TON) and 6 of them active at any time. Great for competitors. I've got some seat time with Helix, and it's also really good. Thus far, those are the only two I've played with. I will admit that my exposure time with the Helix is nowhere close to the deep in depth time I have with TuN. But Forest and I can compare notes between those two. But like anything, there's pros and cons for each. I'll talk more to some folks with specific products as this thread digs deeper into Q&A, but for now the ONLY one I can recommend from experience is TuN/VXi.

 

Great write up Ronin! Just for the sake of comparison, here are some pictures of the program for my AudioControl DM-608. Actually the DM-810 shares the same program. Once I connect the DSP to the laptop, it takes away 2 of the channels and then says DM-608 in place of the DM-810.

 

Thanks Torch for posting that. Man...I would need a few hours with that software before I felt comfortable for sure.

 

Nice write-ups guys

 

80's / 90's Signal Processor Flashback!! Good times!!

 

Hey Torch, can you use a crossover OTHER than Linkwitz with the AudioControl?

 

I was a little more partial to this.....

 

I believe that is the only option. I clicked on it and I don't see any option to change it.

 

I still have one of these https://www.pioneerelectronics.com/P...izers/DEQ-9200 don't currently have it hooked up to anything though.

 

Nice! What model is that EQ/Processor? I used to have the 3339.

That's a nice Pioneer. We used to sell one of their headunits that was single DIN, had all this built in. It was over $1K back in the day. Very complicated to use, didn't sell a lot of them.

 

Man...that's a deal breaker for me. There are a few drivers I have that only get the sound we're after using a butterworth filter. Yes, we do typically use L/R on the highs/mid-range...but not being able to adjust the roll-off is very crippling IMO. That just spawned an idea. We should put together a detailed Pro/Con list of the DSPs that we have experience with (open to everyone of course). That may eventually compile enough data for the readers to find a DSP to fit their needs most accurately. While there are a bunch of pros...there are also several cons that come with using VXi. I suppose I could start.

 

Cool thread, but I'm not sure you're communicating all of the concepts correctly. Don't take any of this as an attack - just want the message to be clear.
The easy differentiation between active or passive systems is where the filtering takes place. Before the amplifier = active. After the amplifier = passive.
I don't know why you say "slopes" or "filters" - slopes are a component of a filter - so maybe some terminology is in order?
filters consist of:

• A Frequency - the point in the audible spectrum that you wish to start rolling off power output - IE 80hz, 5khz, etc
• A Slope - how quickly the response should drop off, 6db/octave, 12 db/octave , 18db/octave. 24 db/octave etc
• A Type - based on response from specific passive circuits and dictate how the signal behaves at and below the crossover frequency. ex: Linkewitz Riley, Bessel, Butterworth

You can use a filter to remove low frequencies and we call that a high pass filter.
You can filter out high frequencies and that is a low pass filter
You can use both to slice out a section of bandwidth and that is called a band pass filter.
You might also hear of a subsonic filter - that is just a high pass filter at a very low frequency, like 10, 15 or 20 hz

In all cases the purpose of the filter is to keep frequencies outside of the capabilities of the driver from reaching it. You slice up 20hz to 20khz and assign the different bandwidths to drivers that can handle them. For example, Low pass at 80 hz for your subs, band pass between 80hz and 5khz for your mids and high pass 5k and up for your tweeters.

Passive has nothing to do with allowing the amplifier or HU to control the signal. More like you are allowing the amplifier to play full range, and depending on a passive crossover (analog coils/caps/resistors) to split the frequencies between your components.

Quote:

Usually, passive component speaker sets use an external "crossover" which is a mechanical device containing capacitors and other electronic devices that passively provide the slopes/filters for a driver set as a way to protect them from damage.

Yeah OK, but... there are inherent flaws to passive crossovers. The most glaring problem is that you are stuck with whatever the manufacturer chose to use. Some better kits offer dip switches or the like to tweak with, but ultimately you are very limited in the choices you can make. While at home this is not a big deal, in the varying environments that a set of car components can be installed into - what do you think the chances are that they got it right for a Corvette? (or whatever other car you are installing into) This is the draw to using active crossovers. You can tailor the crossover to the environment on the fly with the twist of a ****, or a simple software change. Of course the drawback to an active system is that you need a channel of amplification for each speaker playing in a given bandwidth.

And of course all this being said the true power of a DSP, it is not just about setting crossovers. As you mentioned - lots of bands of parametric EQ per output channel allows for asymmetrical equalization - which is very important in a car where the interior is asymmetrical! Also many units allow for input EQ to tame factory equalizer settings in addition to output EQs. Time alignment to make sure everything is in appropriate phase. The tools that even the cheapest modern DSPs put in our hands are absolutely phenomenal. Coupled with other tools, like a 100 dollar measurement mic and Room EQ Wizard software, and the ability to see what the sound is doing and make corrections in almost real time is mind boggling.

I honestly would NEVER install another passive system in a Vehicle that I wanted to sound good.

DSPs I've used:
Alpine Bass Engine Pro CDA 9833
Alpine Bass Engine Pro CDA 9887
Precision Power DCX-730
MiniDSP 2x4
Dayton DSP-408
Also in prosound the Ashley Protea

You'd be surprised how good you can do with just one of those alpine bass engine pro head units. They have their limits and can be tedious to set up, but they are still great bang for the buck. The only reason that I am going to use the Dayton DSP over the 9833 that I am currently using in my 94 is that I want 3 way fronts plus sub, and the Alpine doesn't have enough outputs.

 

[QUOTE=VinceC5;1601568006]Nice! What model is that EQ/Processor? I used to have the 3339.

3342. I had the 3339, also. Both were awesome. A couple of my favorite all time pieces. Wish I still had one of them and a 7909 for a throwback system.

 

You do realize that the difference between the two is that butterworth filters have a 3db bump at crossover frequency? Would be pretty easy to just eq that in.

 

For me there was a learning curve, but in all honesty the software is not that difficult to work with. Looks more complicated than it is, but you spend most of your time on the one screen, the "output view" screen. I'm sure in 10 minutes you would have it figured out. But when you are seeing a DSP for the first time, you will spend some time scratching your head trying to figure out where to start, lol. Also, in my case, I blew my shallow 10" sub the first time using the DSP.

 

Dave, You said everything accurately. I gave the super truncated version because I just wanted to get the thread going. I only had a few minutes when typing it up initially. I knew that the terms and definitions would come soon enough...

 

Damn man. That suck to hear. I'll bet you wont make that mistake again though huh? Note for the newbs, ALWAYS set your filters BEFORE playing any music from your drivers.

 

I knew what you meant, man!