My system_1

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pwatts

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Hello everybody,

Since there were a few requests, I've taken a few pictures of my humble system. Because it's in a constant state of upgrade and I'd rather wait until I have something excellent than get something mediocre in the meantime, some are a bit lacking in quality. I've posted some pictures next to each other to save space. http://s95.photobucket.com/albums/l139/pwatts_2006/ - just start from the bottom as I added the pics in reverse order ?:?

1) Part of my reference audio rig at work. Excuse the mess; it was in the middle of a massive cleanup... I built the ProAc 2.5 clones (one standing on the left) instead of buying a mediocre commercial speaker during a boring Christmas holiday. Its totally lavish crossover with Hovland capacitors, 12AWG foil coils etc. are mounted on the back to be easily bypassed for digital crossover experiments. The finish was quite simple - since they're carried around quite a lot and are bound to get bumped, the finish wasn't important. I simply used dark oak-stained varnish and applied it it in artistic strokes on the bare MDF. Came out quite nicely, but to use separate stains and varnishes works and looks better.
On top of it is the hub of an SB Audigy4 Pro. It was used as multi-frequency digital signal generator and spectrum analyzer before we got the Audio Precisions. Now I just use it to listen MP3's with while I work :)
In the middle is the reference rig. It's a TacT S2150 "digital" class-D amplifier and a Denon DVD3910 universal player. The TacT is used for side-by-side comparison to our research and the Denon since it can produce high-resolution formats as well as FireWire data transfer. Even though DVD audio is encrypted and will therefore either be downsampled or simply muted on the S/PDIF outputs, nobody's stopping me from plugging the ribbon feeding its DAC PCB into a little board of my own and from there to my own testboard...
On the the righthand picture is one of two speaker cabinets that was made for an all-out project but abandoned half-way when I realized that it will be too large for the room. ?
Since it took so much work and effort I couldn't get it over my heart to throw it away, and they're still standing around. They've loads of bracing, bitumen pads, body putty and damping material inside and only needs a baffle and rear panel. The multiple subenclosures can be sawed out to change the internal volume section per driver so if anyone's interested, they're yours for free.
The Audio Precision and all the other testing equipment is on a separate bench at the back of the lab.

2) My previous transmission-line speakers just before the trash lorry collected them :( They used Scan-Speak 18W-8542 woofers and D2905/9300 tweeters and sounded amazing. Bass extension was also very good. Unfortunately they were very large for the output delivered and were not well suited for home cinema, so with the prospect of a new multi-driver super-speaker in mind (the ones never finished hehe) I gave a few bergies some firewood for a night or two ;)

3,4,5) MY DIY 2.5-way reflex main speakers and a shot of the whole system. Not an easy task to build them.. took quite some time and a lot of effort. The drivers are Scan-Speak 18W-8543 woofers and D2905-9500 tweeters. The cabinet is extensively braced and the baffle decoupled with 9mm Masonite. The cabinets are painted satin black; the baffle is solid yellowwood. The red strips at the bottom is maranti salvaged from an old window frame - it wasn't intended for aesthetics but merely because the yellowwood planks were too short after they were planed ;)
The crossover was totally OTT with Jensen coils and caps. The frames for the stands were custom made and epoxy coated; the wood is solid cherry. The idea is to remove the crossovers someday when I feel up for it and place them in a box in the cavity under the speakers. The boxes, terminals and cabling are all finished and ready, just need to find the willpower to take out the woofers, remove the crossovers with a crowbar and sledgehammer and drill holes for new terminals in the back.

6) Mid-construction of the centre speaker; completed pics can be seen in the previous photo. It uses the same drivers, but the crossover was modified and the tweeter placed off-center to aid polar lobing issues. The entire box except for the internal bracing is made of 20mm African Iroko. The thing weighs a ton and has excellent bass extension, deep but not boomy. It can be used at THX volume levels set on "large" mode without ever overexcurting due to high sensitivity and power handling - provided there is a sub present so that the LFE channel isn't mixed into the other speakers. Despite using bucking magnets and optimally placed steel sheet shielding; the massive magnets are still too strong to be preserved from screwing around with my CRT TV. Since I was still not too happy with the sound anyway, I bought a McIntosh centre speaker on eBay that's on the ship to SA. Hope it arrives here in one piece as the total price was far above my means. No idea what will happen with this one, esp since I also have a superb B&W CDMC-SE centre lying around. Maybe I'll experiment with digital crossovers on it to find a more optimal crossover configuration but I really don't have the time or space to keep it, so if anybody's interested in buying and improving it with a new crossover make me an offer.. Same goes for the B&W too hehe.

7,8) My left and right subwoofers. They're based heavily on Siegfried Linkwitz's Thor, and consist out of Peerless XLS12 drivers in a 50l sealed box; actively equalized. The cabinets are heavily braced in the B&W matrix-style, and finished in the same method as described for the ProAc clones since I built them at the same time. The intention was to resand and having them painted eventually, but they look pretty enough for the time being IMO. I used two subs for a more even spread of sound and less bass nulls in the room, but also since the equalisation reduced power handling. Ideally I need four of them but I've never managed to push them beyond their capabilities. Say hi to the cat ;)

9) On the left picture are the system and subwoofer controller. At the rear is a 16A mains filter. Just ignore the crappy transport and stereo VCR...
The controller has two settings; hi-fi and home cinema. Depending on the setting, the proper equipment for the corresponding setting is powered on and configured correctly. For hi-fi, the subwoofers are fed with the lowpassed stereo signal. For home cinema it receives the discrete LFE channel. It also contains the equalisation circuitry, summing blocks, RF filers etc. The main speakers run full-range without any highpass filters. However, I'm already redesigning a more compact and improved version using only SMD components and a more elegant design. Following a few listening tests I could also not hear any difference between the 50VA toroid inside and a cheap wall wart.
Next to it is a Rotel RSP985 THX processor that also serves as DAC and preamp. Despite all the reviews, its DACs sound terrible with a super-bright top end. It's even evident on home cinema material, but not as distracting and actually sounds good... eish and to think I could have bought a Lexicon DC-2 for not much more. It's futile to use my RDP980 DAC since the thing passes all the analog inputs through an ADC and then through the DACs again, and to use a separate preamp would need some sort of switching box to the power amp that I don't want right now. I'm having a proper equipment rack built at the moment that has much more space and easy to access everything, and on that I will have two completely separate systems for hi-fi and home cinema. One of the following projects is also to bypass the processor's internal DAC's and transmitting the digital data to a dedicated multichannel outboard DAC.
The righthand picture is my amplifiers in use. The top one is a Rotel RB985 THX 5-channel power amp. It sounds surprisingly good for hi-fi and is also the reason why I haven't bothered over the years to replace it. It is scheduled to be replaced by a 3-channel 300W Leach SuperAmp which is almost finished (for three years now), but I just don't have the time or energy to build a proper chassis to house its 1.5kVA transformer :( I intend to replace everything with class-D amps anyway as soon as I'm happy enough with their performance.
The bottom amp is a very cost-effective subwoofer amp. It's a 4-channel 80W power amp, bridged to deliver two channels of 240WRMS into 8ohms; one channel per sub. It was rather cheap to build, the chassis is spraypainted MDF with 1mm epoxy-coated steel plates for the lid and faceplate, and the heatsinks with the amps were bolted to the side walls with a temperature sensor and fan at the back. The power supply for both channels share the same 625VA toroid and each channel has 20000uF capacitance per rail.

[continued in part 2]
 
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