In this application note, we show you how to 'time align' the drivers in your active DSP loudspeaker using the delay function of the miniDSP platforms.
There are two basic ways to carry an electrical audio signal. The first one is unbalanced.The signal is carried on a two-conductor cable. Unbalanced signal connectors have two pins, such as the RCA (also called Phono and Cinch, commonly used by home hi-fi equipment) and the unbalanced 1/4' (used in musical instruments and semi-professional audio).). Multi-pin connectors can also. My mac is stuck loading.
Why time-align?
In a multi-way loudspeaker, the sound from different drivers will take slightly different amounts of time to reach your ears. The figure below illustrates a typical scenario: since the woofer cone is 'deeper' than the tweeter, the acoustic center of the woofer is further away from the listener's ear than the tweeter. The sound from the woofer will therefore arrive at the listener's ear slightly later than the sound from the tweeter. This can have a detrimental effect on the speaker's response around the crossover.
One approach to this issue is to build a slanted or stepped baffle. In passive crossover design, the designer may use specific techniques to shift the phase of one driver or another to compensate. In a miniDSP crossover, we use the Delay parameter in the output channels to delay the signal from the tweeter by a small amount of time. The result is that the acoustic waveform from both drivers will arrive at the listener's ear at the same time.
Use this calculator to discover the delay needed between two sets of loudspeakers. Just measure the distance between them and hit Calculate. Having the correct delay will prevent noticable echo on your sound system. Essential for live sound and conferences. This calculator uses the theory Published on Wikipedia amongst others. May 05, 2016 Haas' findings can be applied to sound reinforcement systems and public address systems. The signal for loudspeakers placed at distant locations from a stage may be delayed electronically by an amount equal to the time sound takes to travel through the air from the stage to the distant location, plus about 10 to 20 milliseconds and played at a level up to 10 dB louder than sound. Speaker Signal Delay Calculator 1.02 is an effective audio recording tool which allows you to calculate the amount of signal delay needed to time align the subwoofer and the two separate arrays of main speakers in the sound system at Abundant Grace Church of Troy Michigan. Many amplifiers and powered speakers designed for complex, multi-speaker setups come equipped with digital signal processing (DSP) that includes onboard speaker delay. Often, this delay allows you to simply enter in the distance between speakers, calculating the delay offset automatically.
How much time delay?
Sounds travels at 343 meters per second, or 1126 feet per second. If you can measure approximately the distance between the tweeter and the woofer cone as indicated above, you can calculate the time delay with one of these formulae:
- Delay in milliseconds = distance in cm / 34.3
- Delay in milliseconds = distance in inches / 13.5
Alternatively, if you have an acoustic measurement program, you can calculate the delay by measuring the arrival time of the signal from each driver, and calculating the difference. The result is the time delay needed. The arrival time measurement can be done in Room EQ Wizard (REW) with the use of a two-channel soundcard - see the REW documentation for Use Loopback as Timing Reference.
Nexus mods for ps4. Another method is to run a measurement sweep on both drivers at the same time. If one driver is significantly delayed, you will be able to measure the time difference between the impulse response peaks.
How to set time delay
Almost all miniDSP DSP platforms will support time alignment, but for the sake of clarity, we'll use the miniDSP 2x4. In the interface to any of the miniDSP 2x4 plugins (Stereo 2-way PEQ, 4-way PEQ, and so on), click on the Delay/Gain/RMS block. Set the time delay of the closest driver as indicated in the screenshot below.
In the plugins with eight output channels (4x10, 10x10, miniSharc), all delays appear on the Output tab. With these plugins, you can implement three-way or four-way speakers and use time delays to time-align all drivers. Just remember to calculate delays relative to the furthest-away driver. This screenshot shows four channels of one of these plugins:
Wrapping up
Once you have delays set correctly for all drivers, your crossovers will be easier to design. Don't forget to ask on the miniDSP forum if you have further questions!
Signal Delay Circuit
Looking for an Audio processor doing time alignment?
Check out the miniDSP webstore.
Check out the miniDSP webstore.
This article was first published on the Sierra Circuits blog.
It is the second of the PCB Transmission Line series and follows the article entitled What is a PCB transmission line? It was written with the great help of Atar Mittal, Sierra’s Electrical Engineer and General Manager.
At high frequencies, transmission lines need to have a controlled impedance to predict the behavior of the signals and avoid signal reflections, crosstalk, electromagnetic noise, etc. which could damage the signal quality and cause errors.
This is the reason why you need to know at which speed signals propagate on transmission lines and the time they take to do so. I will give you a few equations to calculate the signal speed and the propagation delay for both striplines and microstrips.
Signal speed
Let’s first discuss the speeds at which signals propagate on a PCB interconnect.
Electromagnetic signals travel in vacuum (or air) at the same speed as of light, which is:
A signal travels on a PCB transmission line at a slower speed, affected by the dielectric constant (Er) of the PCB material – the relations for calculating the signal speed on a PCB are given below:
Where:
- Vc is the velocity of light in vacuum or air
- Er is the dielectric constant of the PCB material
- Ereff is the effective dielectric constant for microstrips; its value lies between 1 and Er, and is approximately given by:
Thus, the speeds of signals on a PCB is less than that in air. If Er equals about 4 (like for FR4 material types), then the speed of signals on a stripline is half that in air, i.e. it is about 6 in/ns.
Henceforth, you can use Vp to denote the speed of signals on a PCB.
Propagation delay (tpd)
The propagation delay is the time taken by a signal to propagate over a unit length of the transmission line:
Where:
- V is the signal speed in the transmission line
In vacuum or air, it equals 85 picoseconds/inch (ps/in).
On PCB transmission lines, the propagation delay is given by:
![Speaker signal delay calculator for kids Speaker signal delay calculator for kids](https://www.motorator.com/wp-content/uploads/2014/12/Audio_Control_DQ-61_1.jpg)
Speaker Time Delay Calculator
The signal speeds and propagation delays for a few PCB materials are given in the table below:
Speaker Signal Delay Calculator 2017
The next article of this PCB Transmission Line series will focus on controlled impedance. It will answer the question: When is the length of an interconnection to be considered as a controlled impedance transmission line?