Ecasound is an incredibly versatile audio processing tool but it doesn’t have dither. I wish it did.
Category Archives: Software
I just posted version 0.0.4 of my LADSPA plugins for doing crossover/equalization of active loudspeakers. Just a couple of changes to note:
- First-order low- and high-pass filters are now available.
- The build system has been moved to cmake; hopefully this makes it easier to build the plugins on other platforms. Also some code cleanup and restructuring. (All thanks to Florian Franzmann.)
There’s no need to upgrade if these changes don’t affect you.
At some point the LADSPA API will become deprecated and my plugins will have to be migrated to LV2. Any volunteers?
Lateral Reflections in Rectangular Rooms (Code)
Several people have asked for the code that I used in a previous post to calculate and plot first-reflection delay times as a function of listener- and loudspeaker-placement. So here it is.
Running the script below will produce pdf or postscript graphics output that looks like this:
An R Script for ABX Testing
I couldn’t find a computer program I liked for doing ABX tests and so ended up writing my own. The full program listing (in the R language) is given below in case someone finds it useful. Continue reading
Pluto 2.1 with Software DSP
About a year ago I implemented a software-DSP version of the Linkwitz Labs Pluto 2.1. My aim was to replace the original analog signal processor (ASP) with a small, standalone PC that can double as a media server: like a Squeezebox that also performs xover/eq duties.
Pluto is an outstanding loudspeaker, and really deserves to be built/heard by more people. Part of my motivation is to provide a lower-cost, easier-to-build alternative to the ASP.
I own the original ASP version of Pluto 2.1 as well: in several hours of level-matched A/B listening tests I haven’t been able to hear any difference — except that my DSP version currently has a less powerful amplifier on the woofers, which limits the peak output somewhat.
If you want to go the software-DSP route yourself, follow the 2-way crossover instructions in my DSP how-to article. I’ll post the proprietary Pluto-specific configuration files in the Owners’ area of the Orion/Pluto Forum. Continue reading
Digital Crossover/EQ with Open-Source Software: HOWTO
The following setup can be used to implement a 2- or 3-way digital crossover (with equalization) for active loudspeakers. It runs on a linux PC and uses only free, open-source software. My design goal was a small, self-contained unit that can live on a shelf beside an amplifier: it runs without need of a display, keyboard, or mouse, and it looks like this:
The PC is the small box on the left. It’s silent, always on, and requires no user interaction.
One could use this system to implement the xover/eq for the Linkwitz Labs Pluto 2.1 or LX521. For those interested, I’ll post specific configuration files in the Owners’ area of the Orion/Pluto/LX521 Forum: together with this how-to, those files can be used to build a DSP version of the Analog Signal Processor (ASP) for those loudspeakers. I’ve written a long article detailing my development of the LX521 implementation; my Pluto implementation is similar. Continue reading
Using MusicIP with mpd
Lately I’m using mpd instead of a squeezebox as my network music player of choice. The only thing I miss about squeezebox is its integration with MusicIP. MusicIP is a great piece of abandon-ware. It analyzes your digital music collection to discover acoustic “similarity” between tracks. Given a seed song (or songs), it creates a playlist of “similar” songs — sort of like Pandora, but operating on your own music collection. (The notion of “similar” here is based on some undisclosed metric; MusicIP is most regrettably closed-source.) I’ve used MusicIP for years now and I’m still impressed by how well it works. It’s an integral part of how I navigate my music collection.
I wrote a simple script to act as a middle man between MusicIP and mpd. It gets the current song from mpd, asks MusicIP to generate a playlist with this song as the seed, and passes the result back to mpd. You can run it from any machine on your network. Linking this script to a desktop icon gives a nice way to generate a MusicIP mix with one click. Continue reading
LADSPA Plugins for Active Loudspeakers
Here are the LADSPA plugins I use in my software DSP approach to active loudspeakers. I mostly use them within ecasound, but they should work just as well in any other LADSPA host.
You can download the source code here. Install with the usual
make; make install. Continue reading
LX521 with software DSP
I’ve just finished building a pair of Linkwitz Labs’ LX521 loudspeakers. They’re everything I could want: 4-way, dipole radiation, with active crossover and eq. They sound amazing. Previously the best speakers I had heard were the Pluto 2.1.
What I’ve done differently is to implement the xover/eq with a digital processor, which runs in software on a small pc. I did this using only open-source, free (as in beer) software, plus a bit of code I wrote myself. Continue reading
Room-Mode Correction for Squeezebox with ecasound
I play most of my music through a Logitech (née SlimDevices) Squeezebox. It’s a networked music player that pulls audio files from a server running on a separate PC or NAS. The player runs embedded linux and the server is open-source, so this system is eminently hackable.
By messing with the contents of custom-convert.conf on the server (it lives in /etc/squeezeboxserver on my Ubuntu machine) you can manipulate the audio signal before it goes to the player. A popular use for this is to get BruteFIR to do “digital room correction”. Continue reading