OK I have all of the parts except for the one I need to get started! I decided to buy the plywood cut to size, and found this place: http://www.woodsheets.com/ Seems ideal - it cost £23 for seven small bits of ply cut to size. Their cutting will be way more accurate and clean than anything I could do. Unfortunately they still haven’t got round to doing it yet.
So instead, ten minutes on rePhase and building a linear phase crossover. I’ll talk much more later about getting an accurate crossover. To start, I just want something that works.
I need to create three files, which I’ll call B441.wav, M441.wav and T441.wav. These are the bass, mid and treble files at 44.1kHz. I’m also doing 96kHz for hi-res stuff. A linear phase crossover uses a convolver which effectively multiplies the music signal by another file that contains the crossover shape, producing a band-limited version of the music.
The options chosen in rePhase are very simple:
- I’ve chosen a 48dB/octave (8th order) Linkwitz-Riley crossover. Shown above is the bass (low-pass). I’m crossing over at 250Hz and 4kHz, which is about what the design points were AFAIK.
- I’m using 32,768 taps; more taps means a more accurate crossover. This number is overkill for the crossover I’m using here, but I want to see what the computer can do. I will need the taps when I start doing more processing (especially in the bass) later.
- The centering and windowing are the defaults and are the best settings for what I need. The output format is what is needed to work with JRiver.
You can see in rePhase how accurate the output will be - the target is a blue line, and the output is the red line that almost completely obscures it. The errors are at -130dB and below, so way below noise level, let alone audibility.
Once I have the rePhase files I need to create the config files to tell JRiver how it works. These look like this:
There is also a 96kHz version, which is exactly the same but 441 is replace with 96 (including in the name)
The important parts here are as follows:
- Name - JRiver will automatically change between 44.1 and 96kHz sampling rate if the files are named correctly.
- Top row - sample rate, number of channels in (2) and out (8). I use 8 as that is what the sound card has, obviously two of them will just be empty in a three-way (six channels needed).
- Bass, left channel - row 3 is the file to convolve, row 4 is delay (I’ll do that in JRiver not here), row 5 is the input channel (left) and row 6 is the output channel (main L).
- It then repeats for the six channels I’m doing anything with.
And that’s it. Next I need to set up the computer (which needs everything installed) and configure JRiver.