I Was Told I Don’t Need a DSP
Since I’m Running Passive Crossovers
One thing that affects us all at some time is advice that is misleading, completely wrong, or half correct. A recent conversation with a client brought up a question that can be translated to “Which tools does my mobile audio system need to meet my goals?”. No, this isn’t about tools to install your equipment. Let’s get into the tools used to adjust the electronic signals to suit our goal of good sound quality.
Do I need a DSP?
What are passive crossovers? What do these have in common with a Digital Signal Processor?
Before I get into that let’s look at a list of some of our tools we need for good sound and reliability within an audio system:
Tools of the Trade (within a mobile audio system)
- Filters – low pass, high pass, shelving, etc.
- Level controls
- Tone controls
- Bass boost
- Signal delay aka time alignment
- Phase control
- Polarity switching
The Basic Reason for Passive Crossovers
Small speakers need to have the bass signals removed to reduce distortion and to protect them from damage. Do we need a DSP to do this? Certainly it is a powerful option. Many DSP solutions have the entire list of audio tools in one package.
Back to passive crossovers. At the most basic level they will have a high pass filter to protect a small speaker, usually a tweeter. As designs of passives scale up in complexity we next add a level control to reduce the loudness of the tweeter, in relation to a mid-woofer. This is a valuable tool to have as there are so many places we can install tweeters into a vehicle that adjusting levels is a must. Also, it may be necessary to bring down the loudness of the tweeter in relation to the woofer, such as in a 2-way component speaker system.
As frequency goes up we want no abrupt changes. The woofer and tweeter transition normally happens in the midrange. A passive crossover and a DSP both offer ways to ensure that transition happens smoothly.
Dividing the Signal
Why would the signal need to be divided? What signal am I referring to? Let’s look closer at the diagram pictured above. In the upper left corner the boxes represent passive crossovers, with blue lines representing the speaker wires carrying the output signals from the amplifier(the red box).
Ok. Two amplifier channels. Four speakers. The next vital reason for passive crossovers is to split an amplifier output channel to allow the use of 2 or more speakers. Does this sound like a familiar concept from your experience of audio systems?
Ok, but do I NEED a DSP??
Filters, level controls, equalizers, delays, and more. If I may make an analogy, there’s a lot that’s been done with very basic woodworking tools. Give a skilled builder a jigsaw and some sawhorses and you might be stunned at the quality and creativity of mobile audio system that can be constructed. Add more tools, such as a router table with a variety of bits, a table saw with a fence to cut perfect straight edges, and the build time is reduced and precision scales up rapidly.
When we can add more tools to the mobile audio system before and after the amplifier the potential to enhance the experience can be enormous. A DSP can be thought of as a complementary array of tools to give the system designer / builder many more options.
I want to mention also, as it can’t be ignored if you ever intend to master mobile audio systems, the undeniable influence of the interior of the vehicle on the sound system. Reflections happen off of every surface and we sit very close to all surfaces inside our vehicles. We can’t throw the toolbox at this problem, but in the “Passive Crossover vs DSP” debate it’s obvious the DSP route can give us a big advantage.
Do not underestimate the power. Do you need a DSP? I want you to let me know what questions you have from this article. Leave a comment below and subscribe to get updated of future posts.