Comparing the Dayton Audio DSP408 and Minidsp 2x4
The DSP408 and Minidsp 2x4 are compact A/D-CPU-D/A units designed to be active crossover appliances with room correction. These are both pretty old but I had them lying around and decided it was time to test them carefully for a project.
Introduction
The Dayton Audio DSP-408 uses two ADAU1701 chips to provide 4 inputs and 8 outputs. The chip supports 48KHz 28bit audio though most of these systems use 44.1KHz sampling rate.
The Minidsp 2x4 uses one ADAU1701 chip to provide 2 inputs and 4 outputs. It was discontinued years ago and replaced by the 2x4 hd then the Flex. Nevertheless, the A/D and D/A quality are reasonable as is the noise level and this unit was a mainstay for many people as an active crossover for years.
Comparison
The primary differences between the units are in two categories — software support and analog amplification.
Software Support
The DSP-408 comes with a Windows-only application that’s pretty simple to use. It allows linking of channels (so only one needs to be set) and it’s a single screen so easy to deal with. In my use of it there were a few minor bugs but it was usable. There is also an Android Bluetooth application if you bought the Bluetooth module addon.
The Minidsp software is an extra-cost option (!) and is a little more audio-focused but definitely harder to use effectively because you have to dive into each option to see how it is set. It is multi-platform with few bugs. The worst missing feature is an inability to load the existing settings.
This is a 5-band equalizer (vs the 10-band DSP408) but it lets you manually set the biquad coefficients — if that makes any sense.
Analog amplification
These units need input preamplifiers and output buffers. The two units are very different here — mainly in what voltage range they support.
The minidsp 2x4, in my testing, started distorting badly at 1/2 volt input. The DSP-408, conversely, supported at least 2 volts of input — and is rated to 4 volts. So, the minidsp has low output and it’s not fixable — and thus it will distort unless you are very careful with levels.
Finally, the DSP408 has about 5dB of gain compared with the minidsp at 0dB gain— so if you A/B compare the two units it will sound way better — it’s louder. Set the output gain to -5dB to get approximately unity gain.
Bluetooth
The DSP408 has options for a bluetooth adapter for remote control and streaming. I don’t have one but online reviews are that they work. The minidsp has none of this.
Noise and Distortion
I did analyze noise and distortion for the two units and they are nearly identical. The Minidsp 2x4 has a slightly lower noise floor and slightly less distortion but they are very close.
Name Minidsp DSP-408
Voltage 358.5 508.5
THD 0.0026% 0.0049%
N 0.0075% 0.0075%
IN PERCENT
THD+N 0.008% 0.009%
2ndH 0.0025% 0.0048%
3rdH 0.00014% 0.0004%
4thH 0.00013% 0.00035%
5thH 0.00066% 0.000075%
6thH 0.00013% 0.000072%The above table was at equal input (.36V) set to 0dB gain but not equal output.
Conclusion
I’ve been loath to use the DSP408, assuming it was inferior quality due to cost. Well, that was a mistake — every test shows that it’s a good ADAU1701 implementation with more dynamic range than the Minidsp unit.
