DSP's

Digital Signal Processors (DSP)

Welcome to the home of unpopular opinion and independent thinking.


If your vehicle is in sound competitions or you’re planning on entering your vehicle in sound competitions most of this article does not apply to your application.


DSP’s are not all created equal. Each model has its own set of features and specifications. This article is not about specific DSP models but about specific functions.


Some DSP’s allow to adjust each channel’s frequency curve output, commonly called an EQ curve. The problem with that is that by adjusting each channel independently you won’t know the final outcome until all channels are “viewed” together. That is why I don’t recommend adjusting each channel independently because it’s a waste of time. If all of the channels are adjusted simultaneously you won’t have to go back and adjust it – ever. If the frequency curve is properly adjusted with no dips or peaks within the curve and the desired overall curve is adjusted correctly you will never need multiple EQ settings for different genres of music, assuming the system was properly set up to begin with.


Some DSP’s offer time delay settings to be adjusted. Basically time delay is to ensure all frequencies arrive to the listener’s ear at the same time. Varying frequencies will arrive at your ears at different times within a vehicle because of the physics of sound. The amount of time delay is calculated by measuring the distance between each speaker and the listener’s ears. There is a huge problem with time delay adjustment in the real world, for every one adjustment made to correct time delay for the driver all other listener’s in the vehicle their music will be negatively affected by two adjustments. The better you make it sound for the driver, the worse it’ll sound to all of the other passengers. If that’s the sound you desire in your vehicle you should probably stop reading this article. You can also take the measurements for time delay from the center of the vehicle but no one sits in the center of their vehicle so there again it will be adversely affecting the sound depending on where you’re sitting in the vehicle.


Some DSP’s have built-in crossovers. The convenience of having a DSP with all of its functions within one unit is a huge benefit to car audio due to lack of room for equipment. Crossover points and crossover roll offs can have a huge impact on the sound quality.


Some DSP’s offer signal summing. Summing is connecting two channels (a left and a right) to create one mono signal. This mono signal is helpful in creating a distortion free listening environment because when competing stereo bass signal’s soundwaves cross it creates distortion. Bass at its lowest audible notes are already summed but higher bass frequencies are not always summed. A DSP with summed outputs for bass guarantees no distortion will be created by bass stereo signal’s soundwaves adversely crossing each other.


Some DSP’s have a surround sound processor. Surround sound was created for watching movies. Have you attended a small concert that didn’t have a stage but instead had speakers that played the entire frequency spectrum surrounding the audience? No you have not. The real world intent of high end car audio is reproducing the sound that a concert stage has at approximately 30’ from the stage and you’re not going to get that with surround sound. Surround sound will make your movies sound much better and more lifelike assuming you have the required equipment to reproduce surround sound in the first place.


Some DSP’s have a filter so that frequencies that the human ear can not hear aren’t reproduced which saves power for the frequencies the human ear can hear. It can be called the proper term of subsonic filter or any number of other marketing terms. Most humans can hear down to around 20 Hz so it’s a waste of energy to reproduce signals below 20 Hz. The higher frequencies the human ear can not hear consume so little power to reproduce it’s not a concern to filter those frequencies out.


Some DSP’s offer line output convertors which converts a speaker level signal to a low level or RCA signal. This is a very handy feature if you’re using a factory deck.


Some DSP’s have real time analyzers that allow you to see the frequency curve being played.


Some DSP’s have built-in Bluetooth which allows the user to adjust the DSP with their cell phone.

Rod Davis

 

Band limiting was initially introduced for the purpose of saving disk space. Back when digital files and audio were brand new, the cost of digital storage was exponentially more than it is now. The thinking was that since you can't hear it, why bother storing it digitally at great expense?

This is where the Analog vs. Digital topic can get deep into the weeds. Suffice it to say, experiments were done and it was conclusive through encephalography that, while humans can only "hear" 20Hz to 20kHz, there was much more brain activity observed on non-band limited recordings, and, when asked, people preferred the non-band limited recordings more than band limited recordings by much more than the margin of error.

Is it practical? Obviously not, but digital storage has reached a point of affordability, so now it's all about one's preference. Keep in mind, also, that while you may not be able to hear subsonic frequencies, you can definitely feel them. This is why benchmark recordings, where frequencies as low as 6Hz-8Hz exist, and are used to evaluate sound system performance.

Signal summing was born out of necessity and not related to how sound waves interact in the listening environment. People wanted to augment their factory system, which in a lot of cases had already split up channels into high and low frequency bandwidths. The intent of summing is not to combine left and right, it is to re-combine high and low from a channel that was split by the vehicle's premium audio system. By assigning the vehicle's tweeter output and woofer output into a summed input channel, you could restore the full bandwidth for processing by the DSP, and then configure for a new output configuration, like in the event you replaced the factory speakers and ended up with different crossover points, or wanted to split three ways instead of two (or the inverse).

Sound waves colliding can be beneficial, a primary example is what you get when stacking subwoofers together to not only create a baffle that projects the waves forward, but to also create constructive interference which boosts output at certain frequences, like what happens in a tuned port.

This is just absurd. It's like saying you're fine golfing with two clubs instead of a whole bag, or two wrenches is better than a full set. You're also making the assumption that all music is band/stage oriented and that's just not the case. There's a vast history of experimental and electronic music that doesn't follow a tradition of mixing to stage oriented reproduction.

All surround capabillity does is add more points in space from which sound can be reproduced. The more independent channels you have, the more tools you have to move sounds around the listening space. With a 5.1 system, it is possible to move a sound around you in a circular pattern. Will multichannel capability benefit most music commercially available? No. Can you buy 5.1 audio? Absolutely, yes.

 

Since DSPs are on the menu here, I'd encourage anyone interested to download the JL TuN application and experiment with it in Simulation mode, so you can get an idea about how powerful it is. I downloaded several DSP software applications from various developers and I really came to like the one from JL. Getting this kind of flexibility used to be unaffordable for consumers, and there's a LOT of professional gear out there right now running huge sound systems that can't do a lot of the stuff this does at more than quadruple the cost.

http://www.jlaudio.com/Info/TuN+DSP+Software/Discover+TüN™+-+JL+Audio’s+DSP+tuning+software+for+the+PC+platform!/8096706

 

This is a great topic. DSPs are like voodoo or witchcraft to me. It's definitely something to consider, especially if you are going to do a true SQ install, or even sub-SQ

 

I think if you want to go for a higher end system the DSP is the way to go. No complaints about my VXI! It's hard to tune yes, but that is also a learning opportunity.

 

100% agree. I purchased a VXI 800/8 and have just started unlocking all of the goodness it provides as I learn how to get the most out of it. It allows you to quickly experiment with different settings and see how it changes the sound.

For example, I was hearing an issue with the sound stage coming from the left. Just by dialing in delay, I could move the sound stage to center. It blew my mind!

If you have it in your budget, I would highly recommend VXI. JL audio has knocked it out of the park.

 

The sound stage is at center without any delay so if you adjusted delay you've moved the stage from the center.

 

I don't sit in the middle of my truck. It was easier to adjust the delay.

 

I just threw in a TwK-88 all dirty and reset some levels, tossed in a guesswork EQ using screen shots of the response from last time I tuned the stereo and set crossover stuff and muh gawd my shit came alive. I think it's pretty much a must have.

 

Ya, once you know, it's hard to go back. I own at least 6 now.

My faves

Helix DSP - amazing little units that can be found around a couple hundred bucks anymore



Also found a pro board for a song - next to the 4 x 8



Didn't have a case for it though so a really awesome dude turned this



Into this!



Anodized