Sound you can see through
by Lance Dow
My current pride and joy - and un-doubted stars of the show - are my DIY electrostatic loudspeakers. These are a hybrid of ideas I got from reading articles by Roger Sanders and David Lang in Speaker Builder, with a few bits of my own thrown in (I may write this up, one day). More of these in a moment. First some background.
The PastMy DIY audio history goes back almost 30 years. A few years ago I wrote about it for our newsletter (it may appear here sometime in the future). It ran to over three pages - even though I left a lot out - so I won't repeat it here. I built my first amplifier around 1969/70 and my first pair of speakers around '72. In those days, though I wanted hi-fi, all that really mattered was that my system went louder than my friends systems! I built many different components to try and achieve this - my friends were doing the same of course.
I arrived at what should have been my ultimate system around 1975 - 4-way transmission line speaker system using KEF drivers, 70w/ch transistor amp, low noise pre-amp from a magazine project, Thorens TD150 turntable, Audio Technica arm, Shure M75 ED (second only to the mighty V15) tracking at 1 1/4 grams. I was so happy that I didn't change any part of it for over two years. It's never been that stable since.
I damaged the amp in '77 and decided to build a new one instead of repairing it. I built a Crimson Electrik 100w/ch kit, taking more than my usual amount of care as this was going to be my last amp! It sounded better than the previous one. It wasn't supposed to. Everyone KNEW that competently designed amplifiers all sounded the same. This design was a good one. The previous design was a good one - both had excellent specs. Yet this new one sounded better - at all levels. This was the start of a new quest for me, which continues to this day.
I had my first taste of high-end hi-fi around 1982 - Audio Research SP8 pre-amp, Krell KSA50 power amp, Magneplanar MG3 speakers (forgot what the front end was). This was a world away from anything I'd heard up to then and way ahead of what Linn and Naim were offering at the time (British high-end). Over the next few years I became exposed to the Apogees, the Audiostatics, the Martin Logans and realised that this was the type of sound I wanted, but no way could I afford it. By this time I'd developed a bit of confidence in my abilities and decided that if someone else could build it, I could! How's that for cockiness! So, around 1986 I decided to build the best system I was physically capable of. I'm getting there.
The PresentIn '92 I finally decided to build a pair of ESLs - something I'd always wanted to do but had felt was a little beyond me (despite my cockiness). After much fiddling I had a working PAIR - I had single units working on a number of occasions in between, but these all had 'problems' which needed to be ironed out before a matching unit could be built.
The system's performance level was lifted quite considerably when I installed these in place of my Magneplanar MG1s. Initially, I'd planned using the ESLs full range, which is why they're as big as they are. However, they proved difficult to drive in this configuration, even in my small room. After extensive e-mail discussions with Barry Waldron, I decided to add a woofer to the system and built a design he recommended. This lifted the performance to another level as the ESLs were relieved of the burden of reproducing the bass.
Drive to the ESLs was still a problem which, after considerable fiddling, I feel I'm close to solving by going to direct drive. The speakers are transparent enough for me to hear the results of many passive component upgrades I've done in other parts.
The system as a whole continues to surprise me. It's currently performing way above my original expectations. The good news is that it isn't finished, so it can only get better. The bad news is there are only so many hours in a day.
I go to the London hi-fi show each year and for the last three-or-so years I've come away from the show disappointed, having not heard much that I felt was better than I have at home. In time I realised that this was a compliment to my system rather than a criticism of what I heard. I feel a lot better - I'm getting there.
The FutureI haven't really done much work on the bass end of the system, so that needs to be addressed. I have a copy of Speaker Workshop from Audua, a comprehensive speaker design and a measurement system. I built a calibration jig for it and a copy of the Mitey Mike from Speaker Builder. One day I'll put them all together and sort out the integration of the woofers with the ESLs and the room. It sounds great at the night time levels I use most of the time, but sounds a bit disjointed when I crank it up to show off to friends!
I also need more transparent electronics and source components. These are coming.
Speakers - ESLThe ESL cells are 4 ft tall by 1 ft wide, with 1/16 inch gaps, similar dimensions to Roger Sanders compact design in Speaker Builder. The stators are made from fine mesh bonded to plastic 'eggcrate' - the stuff used for lighting in suspended ceilings. The cells are mounted on flat baffles 51" by 19", which are rigidly attached to heavy stone bases. Experiments with my previously owned Magneplanars showed me that this rigidity was essential.
Speakers - WoofersThese are based on a design from Speaker Builder by John Cockcroft called the Freeline. My version uses a Jordan 8-inch driver, mounted one-third the way down from the top of a 4 ft by 9 inch column. The top of the column is open, and there are two ports at the bottom too. The two column sections are heavily stuffed - to different densities - and Cockcroft claims that they behave as two over-damped transmission lines in parallel. Sounds good to me.
CrossoverThis operates at around 150 Hz. High pass to the ESL is a passive third-order CLC - to keep the signal path clean and simple. This filter is fitted at the input of the amp driving the ESLs. The values are adjusted to give a lift in the response of a couple of dBs, just before the roll-off starts, to compensate for the baffle's acoustic roll-off, which I guesstimated to be around that same frequency.
Low pass is fourth-order active. Currently this is in a separate box, running from batteries, but I plan to move it into the bass-amp enclosure at some stage - fewer boxes, fewer interconnects.
Power AmpsThe ESL amp is a push-pull KT88 design which delivers around 60w into 8 ohms. It started life as the Michaelson and Austin TVA1, but has been modified to incorporate the driver stage Joe Curcio designed for his ST70 modification in Glass Audio. This uses 6DJ8s/E88CCs in a differential cascode configuration with regulated HT. I retained the output and power transformers - designed by Tim de Paravacini and reputedly excellent.
The ultra-linear outputs stage has also been modified. Following an idea presented by Bill Kleronomos in Sound Practices issue 4, 75v 5w Zeners are fitted between UL taps and the screens, instead of the usual practice of feeding them directly or via a low value resistors.
The ESL stators are now driven directly (cap-coupled, actually) from the anodes of the KT88s, with a dummy load on the transformer secondary. (See "Driving ESLs Directly")
Bass is handled by a MOSFET amp - the Crescendo design from Elektor Electronics in the early '80s. This is built in dual-mono fashion on a single chassis using separate 650VA transformers for each channel. This amp was originally specified at 140w into 8 ohms, running from +/- 90v rails, but I used +/- 55v as I wanted to run them more Class A.
Pre-ampThis started life as Joe Curcio's Daniel, the original all valve design. Along the way I changed the linestage from the paralleled anode loaded design to a mu-follower, so I could safely drive my long interconnects. I later did the same with the second stage of the RIAA (same topology) - not for the same reason but because I thought it would sound better. It did.
The valve heaters are series connected and fed from a constant current source. This results in a very soft start - about 15 seconds before they start to glow red. No blinding switch-on surge.
I made various small mods to the HT regulators - bigger pass transistors, better filtering and remote sensing from the output of the slave regulator to the anode resistor. Master supply now uses ultra-fast soft recovery diodes followed by a CLC filter.
CD PlayerThis is a largely stock Pioneer PD-9700, the original 'stable platter'. The only mods performed so far are ferrites on internal power supply wiring and grounded copper foil screening around the analogue board. A valve output stage is planned.
TurntableHeavily modified early GyroDec. The pretty acrylic plinth was discarded and replaced by a not-so-pretty one I made using a large garden paving slab (24" x 18"), clad on all sides with wood (MDF and softwood). The edges were then trimmed with hardwood for a more domestically acceptable appearance.
The metal platter has an acrylic mat fitted. The original metal arm mount was replaced with acrylic, after the Oracle.
Wall wart power supply replaced with a 50VA transformer.
Tonearm and CartridgeRega RB300 with the exit cable replaced with a DIY bundle (meant to be a copy of AudioQuest's star-hex configuration) - internal wiring unchanged. Fitted with a Linn Karma.
TunerSony ST-J60 - their first digital tuner from 1980. Some PSU mods, audio op-amp replaced, fitted better coupling caps.
Interconnects and Speaker CablesDIY XLO-style single strand silver with teflon insulation for both.
ESL LinksIf you want to know more about DIY electrostatic loudspeakers, see the ESL section on our Links page.
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