The Subwoofer Units Arrive...

These are BIG, at least, in a normal home! And heavy... They look like very big brothers of the fiddly woofer units, with their aluminium cones and magnet setups.

Boxed - you can just see the cunning cone/surround protector plastic lid

Even the hole in the box looks like a dormant volcano...

Top view - A4 sheet of paper for scale

Side view - note the suspended spider and open voice coil

Costs so far

As of 2017-02-24, updated to include Subwoofer costs:

Thing	Cost
Speakers	£212.40
Pipes	£74.56
Wadding	£18.28
MDF (6mm)	£8.99
Fixings	£13.20
Cables, Plugs, Sockets	£34.17
MiniDSP	£93.00
Sony Amp	£35.00
Linkwitz plans $105 (forgot this earlier!)	£72.65
Wickes 4" clay to PVC couplers	£19.96
Push-on tag connectors	£2.00
Wire	£6.00
S/W Cables, Plugs, Sockets	£25.33
S/W Speakers	£393.00
Linkwitz plans $55	£44.84
Paint	£15.98
Total	£1,069.36

Ouch. Still, cheaper than a Quad rebuild, and remember, this includes the DSP and amp, unlike Dr. Frank's kit. And also the plans from SL!

24 Feb 2017:  Subwoofer adds about £450 to the cost, most of which is the enormous drivers, at nearly £200 each! They are astounding impressive though. Let's hope the sonic effects are as massive.

Remote control?

I'm also fiddling about with RPi audio. I'm not sure where this info should go, but it's here for the moment.

The cheap Chinese Hifiberry Digi+ knock-off board has an IR sensor on it, which in principle can be used to allow a remote control to do things to the system. Interesting...

A bot of research, and it seems you have to use lirc, the Linux IR Controller module. Acting on some hints/instructions in various fora, I've

• Modified my config.txt to include 
• dtoverlay=lirc-rpi (load the right module)
• dtparam=gpio_in_pin=26 (enable the GPIO pin IR sensor is connected to)
• Rebooted the RPi (took a couple of attempts, with an edit of config.txt for GPIO 26 from 27 - oops)
• Run mode2 -d /dev/lirc0
• Pointed my old Virgin Media TV box controller at it...
• Result! lots of pulse/space codes....

[root@Frontroom ~]# mode2 -d /dev/lirc0

Using device: /dev/lirc0

Using device: /dev/lirc0

Warning: Running as root.

space 16777215

pulse 10974

space 4670

pulse 753

space 577

pulse 731

space 551

pulse 726

space 586

Now I have to teach the lirc software the remote control buttons. It's a wet afternoon.

Update

I did managed to record something from the controller, a post on the runeaudio forum said irrecord didn't work on ArchLinux, but it seemed to for me. At least, it generated a file. I subsequently foundered on a number of errors from the lircd, like "can't find IR thing" and so on. Poo. Maybe I need to get it to work with another platform first, like Raspbian. At least I can now see how it could control the Rune player - it's basically scripts that use mpc, invoked when a specific event is detected.

Digital Ins and Outs

The miniDSP 2x4 kit, miniDigi and cheap Chinese Hifiberry Digi+ knock-off have arrived. Hurray! Let's see if any of this works...

The first thing is to get the Digi+ SPDIF/Toslink interface going on an RPi. I happen to have a spare one (of course!), so I've cloned the SD card from one that works, popped the Digi+ hat on top, and wound it up. Oops - no sign of the Digi+ in the MPD config menu... So time for a quick SSH onto the RPi, vi /boot/config.txt, edit the dtoverlay param so that it includes the hifiberry_digiplus, and now it's recognised. Hurray. You might think the smart money would be on trying something known to work first, like my Focusrite Firewire audio interface with SPDIF out, but hey.

miniDSP 4-way Advanced application

Now for the miniDigi and 2x4. The miniDSP documentation is a bit dodgy, and needs careful reading. I rigged up the miniDigi and 2x4 using the provided 30-way headers, connectors and ribbon cables - there are two sets of connections, only one of which is documented much. This is the I2S interface, I assume the other is about power connections and so on. Time to select 1) input - Toslink initially because they gave me a cable! 2) output - looks like it's ok. I powered it all up from the Mac USB connection, and cranked up the 4-way Advanced configuration application. Bleuch - nothing!

Check the manual - oops, need to ensure I2S Master and Slave relationships set correctly. Set miniDigi to Master. Now there's sound, but a horrendous crackling that drowns out music, and it's constant. 

Check the manual again - check 2x4 MCLK master/slave setting, which is currently Master. Poo - should be Slave (this is not intuitive, but hey... what use is intuition in these matters?). Switch to slave, re-stack boards. Hurray!! Sound, clean, no noise, expected selection of Left/Right on 4-way Advanced interface.

RPi SPDIF i'face, stacked miniDigi/2x4

miniDigi (top) and 2x4 stacked (SD card over bright blue LED!)

Summary

1. RTFM properly!
2. miniDigi - I2S Slave
3. 2x4 - MCLK in Slave position (I2S signals coming from miniDigi)

See what I mean about it being non-intuitive? I guess the difference is between MCLK - the signalling rate indicator, and I2S Slave - who's boss on the interface.

Next Step

Make up the custom connectors, since the provided ones only allow for a single 2x4 to be connected to a miniDigi. More on this to come...

Now for the Big Boys...

Right. I like the LXMini. Could it be better? Apparently yes - there are various flavours of subwoofer available, all of which offload the (fairly small, TBH) lower mid/woofer for the last couple of octaves, and thus allow it to perform better. The SEAS drivers are pretty amazing (see here for some info on that), but the laws of physics will not be denied!

The choices are:

1. Relatively cheap omni subwoofers in 1 cu ft boxes - ok, but does their directivity or lack of it really match the carefully planned LXMinis? They're not a Linkwitz design, but from one of the guys on the OPLUG forum, people seem to have good results, but they would say that! About £130 for the chassis speakers (Peerless 830668), so a bargain
2. LXMini + 2 subs - these are from the Linkwitz design stable, and require the stonking Seas L26RO4Y D1004-04 woofers, at a wallet-busting £370 the pair!! However, they are dipoles and thus more amenable to room placement and more fitting with the LXMini directivity
3. LXStudio - again, from the SL stable, basically the LX521 woofer setup running in parallel to the LXMinis; these require 4 of the aforementioned WFW (Wallet Busting Woofers) at £740, and thus very much a nice to have... Again, the directivity is more fitting with the LXMini

All of these require 

• 2 more DSP outputs i.e. 2 more than I currently have, bummer
• 2 more power amps - now those I do have! The trusty Sony has two spare channels, hurray! You'd almost think I planned it. I don't have enough  power the LXStudio, since that's 2 massive 4ohm woofers per channel

DSP options include, but are not limited to:

1. MiniDSP 4x10HD: SL's choice, a very useful bit of kit, which includes analogue and digital inputs, volume control, selection between multiple stored configs; however, it's another WBO (WB Option...), at a stonking €650 from Audiophonics (not including shipping, but no customs duty (yet!), or $500 direct from miniDSP, in which case no idea about customs, but certainly VAT i.e. $600 before any customs/shipping! No. Not this time.
2. MiniDSP 2x4: Supported by Dave Reise on OPLUG, this is another of the DSP units I already for this project, paralleled by using one each for Left and Right channels, so it gets the same analogue input as the current one. Fairly cheap option, €85 from Audiophonics in board-only form, or boxed from CPC for £95 as last time. This gives me a total of 8 channels of DAC/DSP, which is plenty.
3. Hypex DLCP: excellent 6-channel DSP from these guys, but requires some building work; it has 6 (6!) analogue inputs (balanced - super!), USB/Toslink/SPDIF/AES-EBU digital inputs, loads of horsepower, and it's the basis of a much superior setup, including the Magic521 Powerboxes. It's about £530, without shipping and a good box to put it in. Hmm. I can also get it from Magic521 with the DLCP config file already loaded. If I was starting from scratch, or thought it would sounds loads better (it might :-( ) I'd be tempted. 

I've purchased the LXMini + 2 and Studio subwoofer plans, because they're fairly cheap ($55). Call me impulsive, but I've also bought a miniDSP 2x4 board from Audiophonics in France. Hey, useful anyway, right? It's a good way to try things out, without the massive expenditure of the other options. 

I've also purchased, because it looked interesting, and provides an alternative input mechanism, 

• A miniDSP miniDigi; this provides a digital input to the miniDSP 2x4, resampling the input to 48kHz using standard chips. I'm not sure if it does more than 16 bits, that would be interesting, but I think unlikely
• An Audiophonics digi+ for RPi; this provides a digital output capability for a Raspberry Pi, using S/PDIF or Toslink, and therefore avoids a DAC/ADC cycle when using RPi with the digitally-enabled 2x4. Worth a try, and I can in principle use both inputs with a bit of switchery in the 2x4

The miniDigi also provides a dual 2x4 capability, in that cunning use of its internal switching matrix and outputs will allow me to drive the two 2x4s from a single digital input, in fact that's the only way to do that. Some cunning-ness required, but hey, let's keep this complicated.