In order to get the subwoofer working I would need a crossover filter and a single channel amplifier for the subwoofer. There were a variety of options; buy a dedicated “plate” amplifier which has everything built in, maybe buy a dedicated subwoofer filter and a hi-fi amp from somewhere, perhaps build a kit or even build the electronics myself from a circuit diagram (or schematic).

I changed my mind quite a few times. Originally I intended to build the electronics myself from G. Randy Slone’s book “The Audiophile’s Project Sourcebook” but the filter I built was not up to the job with a totally undesirable frequency roll off below 50 Hz.

My friend who is building the other WO32 subwoofer decided to buy a good quality plate amp but I was worried about the signal going through this before reaching my beloved Decware Zen Triode amp – no point in playing your music through a fantastic amp if the signal is trashed in the crossover stage.

I settled on building everything from kits, specifically kits from Ampslab. I was impressed with the audiophile angle on the web site and the kits looked very high quality. It would give me the right balance between cost and quality – the ability to build audiophile quality components for a reasonable price with less chance of making self-design/self-build mistakes.

Ampslab’s owner and designer, Michael Chua, helped me with selecting the right kits which were the XO2 crossover and the Hx200 power amplifier. I also purchased the power supply board for the amp so the only things I had to purchase were the transformers, fuse holders, switches, hook up wire and a box of course.

The kits arrive

When the kits arrived they were all bagged up and neatly labelled. The only problem I had was the instructions were on a floppy disk and I didn’t have a floppy drive but Michael emailed me the PDFs.

Building the boards was very simple. The biggest problem I had was with identifying some parts but if you are used to building your own electronics you are very unlikely to have any problems here. I found that a couple of the capacitors did not have straightforward markings but we managed to measure them on a multimeter to discern their values. Also I emailed Michael at Ampslab to check on the orientation of the op-amps.

Michael had also replaced some of the listed components with better ones which was the kind of personal touch you just won’t get buying from a shop!

The circuit boards took a couple of evenings, they are actually fun to work on. I think I put together the power supply board and the amplifier board in one evening and the crossover in another evening. The crossover has quite a few components.

Chassis Construction

Compared to soldering the PCBs, building the chassis for the kits is a lot of work and it always ends up taking a long time, much longer than I anticipate.

I decided to use some aluminium sheets I had bought on eBay to construct a rigid base board for each component. I bent the sides down and the ends up to make each chassis rigid and also give me something to screw the box to.

Then, it’s just a matter of arranging the circuit boards, transformers, and other components on the chassis to make sure everything is located in the best possible place, drilling holes and screwing things down. I wanted these kits to be as neat as possible and also wanted to keep the audio path away from the transformers and power supplies.

If you are doing this for the first time, you need to also ensure that you have room for the things you will not be mounting on the chassis – such as the switch, fuse holder, control potentiometers and sockets. In the case of these kits, I decided to mount the sockets on one plate of aluminium, the control pots on another and the switch and fuse holder on another. These would then be screwed to the case which I would be making out of MDF.

With the power amp, I also had the task of mounting the heat sink to the power transistors. I used my Dad’s tap and die set to tap the holes into the heat sink. This worked beautifully and as you can see from the photograph, the kits were now mounted onto the chassis in a neat manner.

Wiring

Next came the task of hooking up all the PCBs and components. This wiring can be hard work, and I had my share of problems with it.

Wiring up the power supply side – the switch and fuse holder to the power supply board – was actually pretty easy, just make sure you leave enough room to get your fingers in there! I use a piece of terminal block to take the mains cable in and also use spare terminal block for any wires which need a home – such as the centre taps of the transformer.

The signal path side was more of a nightmare. I didn’t know what to use because I wanted to use something of a good quality so I started off with some old IXOS interconnect, stripped back the shield and used that for the signal wires. The problem was these signal wires were fine stranded and quite heavy. During the remaining construction of these projects – getting chassis into boxes, wiring up signal wires to sockets – the wires took some flexing and eventually one of them broke off where it met the PCB. I wasn’t happy at all with my choice of signal wire so I decided to “roll my own” using some high purity 18 AWG silver wire in a PTFE tube, wrapped with stranded wire as a ground. This was a much better choice and didn’t snap off!

Boxes

I don’t want this to seem like a trend of mine, I have looked around at various other projects and seen the lovely boxes people construct for their self build audio projects and then I go and stuff mine in some MDF, but I just wanted to do something quick and easy so I could listen to them!

I just cut some MDF on the table saw and for the panels in the sides I cut 2″ diameter holes with a hole saw so the panel openings are long with nice rounded ends. Hopefully I will make nicer boxes soon, but I’m not promising anything. I intend to spray these black to offset the nice aluminium control panel plates.

Testing and listening

Once everything was wired up I was ready to test. I am pleased to say that I didn’t make any huge errors. Well I made one but it was not a disaster – when I powered up the amplifier I tested first the power supply on its own and then hooked it up to the amplifier board and both fuses blew. Looking at the board, which I had so carefully built, I discovered that I’d got two of the power transistors in the wrong locations. So instead of making a tiny mistake I made a large one, but thankfully, the components were fine and, upon resoldering them in their proper locations, the amplifier powered up fine.

Michael’s notes about setting the bias of the amplifier were very clear and it was an easy step to follow. The crossover powered up perfectly first time and nothing blew up! That’s a first for me.

The hard part was over, the enjoyable part was starting. I plugged the new components into the system and powered it all up. Unfortunately the first thing I heard was not music but some rather noticeable 50 Hz hum which Michael has since helped me to (mostly) fix.

The subwoofer sounds absolutely awesome, that is my first observation. I have heard a few subwoofers in my time and this is not like any of them. It has an amazing speed, which is what you’d expect from the horn loaded drivers, and it goes really deep with an amazing amount of power.

This gives the most amazing controlled, articulate bass imaginable. You can hear all sorts of detail and subtlety to low keyboard notes, weird subsonic noises and stuff whereas a regular subwoofer would just turn it into a low thud. The power is also astonishing, so the low notes can sound incredibly powerful, thunderous, if necessary.

I should point out, at this point, that overpowering bass is not the object of the project. The crossover is, as far as I can hear, of a really high quality and integrates the two speakers seamlessly. I did some listening tests and find it pretty hard to hear the difference between music through the crossover and my Zen amp and the Zen amp on its own but I need to get another top quality interconnect to come to some sort of conclusion.

The end result is that, the Decware WO32 subwoofer and Ampslab electronic kits deliver an incredibly refined, integrated bass which fills out and completes the system – two friends of mine say that it sounds “perfect” now. But the power and speed of the subwoofer is such that it continues to shock me, and probably the neighbours. Music with loads of bass or subsonics sound absolutely incredible, with this thunderous, controlled, detailed rumble.

But when I listen to classical music and balance the main speakers and subwoofer you forget what’s playing the music and simply enjoy the depth and range of the whole. Then there’s a sudden kettle drum which actually does sound like thunder and I can’t help but smile.

Conclusion

I’d recommend this project to anyone who has got some woodworking and electronics experience. The Ampslab kits are not so complete that you can just buy one and you have all the parts you need – you do need to get your own transformers, heatsinks and know how to hook up all the parts properly and safely. But, assuming you have that ability, I think the quality of sound is stunning from these kits. Also, Michael Chua is extremely helpful every step of the way with any questions you might have. That personal service really makes me recommend Ampslab.

The Decware WO32 again is something I’d recommend to anyone who has some woodworking skills (maybe they should call it MDF working skills) and something suitable to make the angled cuts. It is not a hard thing to build at all, but you do need to be able to cut the internal angles with some accuracy.

I love Decware very much, their small cottage industry audiophile approach which means that you really can get a high end sound for little money, but it is much harder to get support from them. Recently my emails have received no response and I have had to use the Decware forums to get help with any questions where you will find lots of people ready to help but also you will have to sift through a lot of varying opinions and advice.

The whole thing must have cost about £500. The WO32 subwoofer cost £250 for the drivers, £20 for the plans and about £35 for the MDF. The Ampslab kits cost about £170 for the amplifier and about £80 for the crossover – this includes things I had to purchase like transformers and heatsinks.

And if anyone is in the area and wants to hear how awesome it all sounds…just drop me an email!

This entry was posted on Wednesday, May 2nd, 2007 at 4:24 am and is filed under Hi-Fi. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.