MiniDSP

This application note will study how miniDSP products can be combined to build a processed 2 way loudspeaker configurations. The target audience is expected to understand basics of miniDSP products along with basics of Digital Crossovers. Also note that this application note is only intended as a summary of the information already contained in miniDSP, miniDIGI and miniAMP User manual. For more information, please refer to our product datasheets, user manuals and technical notes available in the Download Section of miniDSP website.

miniDSP Standalone configuration

Systems Requirements

- 1 x miniDSP kit (Rev A or B, depending on your input source)

- 1 x Stereo 2 way crossover plug-in (PEQ, Graphic EQ or 2.1 version)

- Input source: Un-Balanced Analog audio Left & Right (L&R)

- Processed output signal: Un-Balanced Analog audio Left (Low, High) & Right (Low, High)

- Power supply: Single USB charger OR external DC supply connected to the expansion bus connector. See External DC application note for more info

Jumper configuration

- In standalone configuration, no jumper configuration is required. miniDSP is Clock Master and center jumper is on default Master position (M).

miniDSP + miniDIGI configuration

Systems Requirements

- 1 x miniDSP kit (Rev A or B, depending on your input source)

- 1 x miniDIGI (Rev A or B depending if you require isolation transformers or not)

- 1 x Stereo 2 way crossover plug-in (PEQ, Graphic EQ or 2.1 version)

- 2 x link cables provided with the kit

- Input source: Un-Balanced Analog audio Left & Right (L&R) OR Digital Audio source (SPDIF/Toslink)

- Processed output signal: Un-Balanced Analog audio Left (Low, High) & Right (Low, High) AND Un-processed digital audio output available for linking to other miniDIGI boards.

- Power supply: Single USB charger to the miniDSP will provide power to both boards OR single external DC supply (4.5 to 24VDC) connected to miniDIGI

- In a stacked configuration with a miniDIGI board, miniDSP needs to be configured as a Clock Slave (Jumper on S position) and miniDIGI as I2S Slave (Jumper in place). Please refer to the jumper chart for more information on the required board configuration.

miniDSP + miniDIGI + miniAMP configuration

Systems Requirements

- 1 x miniDSP kit (Rev A or B, depending on your input source)

- 1 x miniDIGI (Rev A or B depending if you require isolation transformers or not)

- 1 x miniAMP for 2 x 20W @ 8Ohms or 4 x 10W@4Ohms

- 1 x Stereo 2 way crossover plug-in (PEQ, Graphic EQ or 2.1 version)

- 2 x link cables provided with the kit

- Input source: Un-Balanced Analog audio Left & Right (L&R) OR Digital Audio source (SPDIF/Toslink)

- Processed output signal:

• Un-Balanced Analog audio Left (Low, High) & Right (Low, High)
• Un-processed digital output available for linking to other miniDIGI boards
• Depending on your miniAMP configuration, system could be configured as: 2 x 20W (e.g High Freq out of miniAMP, Low Freq out from miniDSP analog out to a more powerfull external amplifier) OR 4 x 10W (e.g.Low and High Freq coming out of miniAMP)

- Power supply: Single External 12-24VDC supply connected to miniAMP

- In such stacked configuration, miniDSP needs to be configured as a Clock Slave (Jumper on S position) and miniDIGI as I2S Slave (Jumper in place). Please refer to the jumper chart for more information on the required board configuration..

- Can I use both Digital and Analog outputs together in a stacked miniDIGI/miniDSP configuration? Yes, see our miniDSP plug-in datasheet for more information on how outputs are doubled up to both analog AND digital out.

- Can I connect an external DC supply AND USB together? Yes, it's not a problem since they are both surge protected.

- How can I toggle from Analog to Digital input in a miniDSP + miniDIGi configuration? Source selection is available both in software AND hardware using a toggle switch. See our miniDIGI user manual for more information.

- Having other similar questions about this configuration? Please check miniDSP FAQ's and Download section for more info.

This application note will study how miniDSP products can be combined to build a processed 3 or 4 way loudspeaker configurations. The target audience is expected to understand basics of miniDSP products along with basics of Digital Crossovers. Also note that this application note is only intended as a summary of the information already contained in miniDSP, miniDIGI and miniAMP User manual. For more information, please refer to our product datasheets, user manuals and technical notes available in the Download Section of miniDSP website.

With each miniDSP only allowing a 2xIN/4xOUT at max, the first basic reminder is that a 3 or 4way configuration will always require at the minimum 2 miniDSP kits. For a better understanding of each configuration, we would also recommend downloading the "4way Jumper chart" available here.

miniDSP Standalone configuration

Systems Requirements

- 2 x miniDSP kits (Rev A or B, depending on your input source)

- 1 x 4 way crossover plug-in (PEQ, Graphic EQ, Advanced)

- Input source: Un-Balanced Analog audio. Left for one miniDSP , Right for the second miniDSP

- Processed output signal: Un-Balanced Analog audio on each miniDSP kit, for example: Low, Mid Low, Mid High, High (4way) or Low, Mid, High (3way)

- Power supply: Single USB charger OR external DC supply connected to the expansion bus connector. See External DC application note for more info

Jumper configuration

- In standalone configuration, miniDSP is Clock Master and center jumper is on default Master position (M) for both boards. See 4way jumper chart for more info.

miniDSP + miniDIGI configuration

Systems Requirements

- 2 x miniDSP kits (Rev A or B, depending on your input source)

- 2 x miniDIGI boards(Rev A or B depending if you require isolation transformers or not) allow digital audio linking between Left and Right speaker stack.

- 1 x 4 way crossover plug-in (PEQ, Graphic EQ or Advanced)

- 4 x link cables provided with the kit

- Input source: Un-Balanced Analog audio OR Digital Audio source (SPDIF/Toslink)

- Processed output signal: Un-Balanced Analog audio Left (Low, High) & Right (Low, High) AND Un-processed digital audio output available for linking to other miniDIGI boards.

- Power supply: Single USB charger to the miniDSP will provide power to both boards OR single external DC supply (4.5 to 24VDC) connected to miniDIGI

- In a stacked configuration with a miniDIGI board, miniDSP needs to be configured as a Clock Slave (Jumper on S position) and miniDIGI as I2S Slave (Jumper in place). Please refer to the 4way jumper chart for more information on the required board configuration.

miniDSP + miniDIGI + miniAMP configuration

Systems Requirements

- 2 x miniDSP kit (Rev A or B, depending on your input source)

- 2 x miniDIGI (Rev A or B depending if you require isolation transformers or not) allow digital audio linking between Left and Right speaker stack.

- 2 x miniAMP for 4 x 10W@4Ohms or 2 x 20W + external amplifier

- 1 x 4 way crossover plug-in (PEQ, Graphic EQ or Advanced)

- 4 x link cables provided with the kit

- Input source: Un-Balanced Analog audio for each stack OR Digital Audio source (SPDIF/Toslink)

- Processed output signal on each board stack:

• Un-Balanced Analog audio outputs in the following template configuration:  Low, Mid Low, Mid High, High (4way) or Low, Mid, High (3way)
• Un-processed digital output available for digital audio linking between the 2 speakers
• Depending on your miniAMP configuration, system could be configured as: 2 x 20W (e.g High Freq out of miniAMP, Low Freq out from miniDSP analog out to a more powerfull external amplifier) OR 4 x 10W (e.g.Low and High Freq coming out of miniAMP)

- Power supply: Single External 12-24VDC supply connected to miniAMP

- In such stacked configuration, miniDSP needs to be configured as a Master Clock Slave (Jumper on S position) and miniDIGI as I2S Slave (Jumper in place). Please refer to the 4way jumper chart for more information on the required board configuration..

- Can I use both Digital and Analog outputs together in a stacked miniDIGI/miniDSP configuration? Yes, see our miniDSP plug-in datasheet for more information on how outputs are doubled up to both analog AND digital out.

- Can I connect an external DC supply AND USB together? Yes, it's not a problem since they are both surge protected.

- How can I toggle from Analog to Digital input in a miniDSP + miniDIGi configuration? Source selection is available both in software AND hardware using a toggle switch. See our miniDIGI user manual for more information.

- Having other similar questions about this configuration? Please check miniDSP FAQ's and Download section for more info.

In the world of DIY Audio, building good passive loudspeaker crossovers isn't for the faint-hearted!

From the filter simulations to building & assembling the crossovers, there will most likely be more than one revision to get it right. Why? For one, because the software package you may be using to provide acoustic modeling of an enclosure & driver combo is only a model. In other words, an estimation based on math equations, not the real world where, for example, an odd reflection inside the enclosure may modify the response. Your choice of drivers will also interact with the crossover components/filter configuration, making it harder to simulate the system performance. In the end, any experienced loudspeaker builder would agree that there will always be some unknown element that software simulation doesn't cover. The trial & error with different configurations then wins hands down over the pretty software simulations. So you better get yourself ready with an extensive set of passive components, build multiple PCB's, start learning electronic theories (basic & advanced) and try out your luck to fit the previously simulated configuration. Quite a daunting task!

Digital crossovers

Coming to the picture are digital crossovers such as the miniDSP kit. With their great flexibility, ease of use and accurate response, controlling the parameters of a crossover becomes a child's play. A digital signal processor uses cascaded filter banks (IIR or FIR) to provide the processing you need. Forget about electronic design or PCB prototyping with our products. miniDSP kit, a low cost  firmware upgradeable module,  breaks the misconception of Digital Signal Processors (DSP) being expensive.

If you ever thought of building an active bi/tri/quad-amped loudspeaker , you must have also realized how complex of a task it is. A miniDSP kit, a small 4 channel amplifier and off you go prototyping your ideas. Loudspeaker prototyping finally getting back to audio, not writting code or understanding math equations.

Time alignment

In a loudspeaker cabinet, time alignment of each driver is paramount to proper wavefront reconstruction. Think of a tweeter and woofer, mounted to the front of your enclosure,  their respective acoustic center will obviously be offset in space, so in time. The end result will be comb-filtering among other things. (Frequency response not uniform)

By combining time alignment along with the phase relationship from the crossovers, miniDSP kits can make acoustical outputs of adjacent loudspeakers to become coherent.One can easily prototype many configurations by modifying delay and crossover settings with a few mouse clicks.

Processed Active loudspeakers

miniDSP kits along with miniAMP modules are the perfect fit for DIYers in need of an easy solution to prototype small active loudspeakers. Neatly tucked inside the enclosure, the DSP + all digital amplifier combo will provide flexibility and useability DIYers always looked for.

Over are the days of passive filter prototyping, may the DSP fun begin!

The Problem

Mother nature gave us a lot of gifts, but a perfect acoustic space for our Hifi systems wasn't one of them!

Put it simply, acoustic theories are very complex to measure, analyze, model and unless your room was designed by a world famous acoustician, it will always be an uphill battle against the laws of physics. While a certain amount of audio filtering; also called room correction can help to perfect the audio performance, achieving flat frequency response by boosting the signal at certain frequencies will only solve the issue if problems are not time dependant (see more below). Of course, quality of your loudspeakers, amplifiers and any other devices on the audio chain matters, but in the end acoustic theories trump. Following this little disclaimer, let's have a look at what our miniDSP board can do.

Let’s take as an example the Hifi system of a living room illustrated in the below picture.

Many elements will affect quality of the audio system, such as:

•    The window that won’t absorb acoustic energy and will most likely reflect lots of high frequency energy from the left speaker
•    The imperfect free field frequency response of your loudspeaker system
•    The asymmetrical room layout which will affect the stereo field
•    Or simply the listener’s position by the sofa. So close to the back wall, he will most likely experience more low frequency than he should from the so-called standing waves. All together, the end result is an imperfect acoustic space where even the best Hifi audio system will hardly produce a flat frequency response.

How MiniDSP kits can help?

So besides taking down walls, moving your sofa around the room 5 times or considering changing the color of your speaker cable, there are few tricks which can help you improve the overall system performance. Digital audio processors like our MiniDSP Kit are one of them. Thanks to their configuration flexibility, they provide a low cost option to configure audio filters, equalizers and signal monitoring from a simple software interface. However note that there is a limit to how much digital signal processing can solve acoustic issues. In particular, equalization will only solve amplitude related issues.While room modes and other comb filtering (cancelations of waves) issues will require either time alignement or acoustic treatment.

What miniDSP can do, is provide you with a set of filters to easily improve the performance of your speaker system:
•    Graphic equalizer: This bank of filters will  increase or decrease the signal at a specific frequency. Depending of the MiniDSP firmware configuration, you may have 31 bands (also called 1/3 octave) or 15 bands (2/3 octave) available. By boosting/dampening the signal at certain frequencies, speaker equalization is the most common tool for system tuning
•    Parametric equalizer: Similar to the graphic equalizer, but this time with only a limited number of equalization bands that can easily be configured to better fit the needs of the application.
•    Delay: In order for loudspeakers to produce constructive wave front  and prevent as much comb-filtering effect as possible, time alignement of different loudspeaker are typically required. The delay blocks will also come handy in digital crossover applications.

So to summarize this application note, flat frequency response of a system will not happen by the magic of a DSP (no matter which brand it is). However, our boards will help you improve the speaker equalization by boosting/dampening few specific frequencies your enclosure + driver combo may not be able to reproduce.

For more information about digital crossovers, see this section of our website.