Sydney ~ Melbourne Hi-Fi Odyssey, October 2013.

[kramered]

Awaiting your totally rebuilt dht supratek review!

 

Awaiting its arrival with bated breath... You listening Mick?

[Steve M]

(Sydney ~ Melbourne Hi-FI Odyssey, October 2013) continued ...

PART 6 "The Distortionless Loudspeaker ~ Modjeski OTL Valve Amplifier & Direct Drive Acoustat"

The title says it all and I realise that it is a big claim to make. To be honest, I am not really sure that there is such a thing as a 'distortionless loudspeaker', but this speaker may be the closest thing on the planet to being without distortion (other than a plasma tweeter which uses the air as the moving mass to produce sound waves). My Year 12 Physics teacher once told me that nothing in the universe is 100% efficient, there will always be some losses of energy, force and time with mechanical systems. A loudspeaker is a mechanical system and the inherent problem with a lot of them is that they are mechanically and electrically clumsy (that is, with heavy cone drivers, stiff and lossy roll surrounds, hard spiders, electrically imperfect voice coils, resonant boxes, miles of wire in the inductors for the signal to pass through leading to a phaseyness, DCR effects, inductance problems, impedence mis-matches etc) and not to mention it is VERY difficult to get a phase perfect, crossover perfected and time aligned conventional loudspeaker. With all this in mind, what if we could get the mechanics and electronics out of the way as much as possible, in a loudspeaker? If you would like to know the answer to this or, at best minimize these adverse effects in the common loudspeaker ...then please read on.

Before leaving Perth, through the intrepid and well connected Kajak12/Mario, I had become aware of Stereonet member Lansche Plasma Guy/Bryan's departure from his quite famous Azura Horn speaker in favour of a pair of Modjeski OTL amplifier Directly Driven four panel per channel Acoustat loudspeakers. The story goes that the Azura Horns backed up by 8 x 15" Eminence Beta A pro drivers in an Open Baffle array loaded into the corners of the room - was considered by all who heard it to be one of the most dynamic and realistic speakers. So, for Bryan to have replaced a respected and very dynamic horn loudspeaker for a (theoretically) wimpy electrostatic, must mean that the directly driven stat is really something special.

*Rab/Richard's System ...upon landing in Melbourne at 3.30pm on Saturday 19 October, I am quickly whisked off by taxi to Richard's house, located in a swanky little laneway (all the best action happens in laneways in Melbourne, in my experience). Richard is a quietly spoken, sophisticated, cool kind of guy ...I can understand why he might seek out the finer things in life (such as the refinement from an electrostatic loudspeaker). I hear he bought the Modjeski OTL amplifier and Acoustat speaker soon after hearing Bryan's system. Richard's system comprises of a highly modded Tram2 DHT preamplifier (excellent preamp when modded with Coleman regulators, Duelund caps etc), a professionally built Philips TDA1541 KIllerdac (by rawl99/Craig Connor) I'm told the internal layout and workmanship is beautifully done ...this Killer definitely does not have all its innards hanging out like Mario's one (just kidding there big-boy!), Digital Transport for 16bit/44.1kHz Redbook cd replay only (and proudly so) is a modded Wadia 3200. All top-notch boutique gear imo, simple in its approach and not too expensive ...chosen carefully for his personal preference in sonics above all else. Here are some pics of Richards system:

Sounds great, but not the safest loudspeaker in the world with 5000v DC floating around those terminals ...

Neatly constructed Killerdac on top of the Wadia 3200 CD Transport

I won't individually comment on the sound of Richard's system as it is similar to Bryan's, so will discuss the overall sound of both in the following report of Bryan's system. I liked the sound of Richard's room, I heard deeper more extended bass out of the stats there than at Bryan's place. I think because of the long length of the room (maybe 15m from one end to other?), the bass note/waveform was able to develop better in the lower registers. Richard felt that he still had a bit of further tuning to do with the stats to reduce what he perceived as a midrange prominence.

Edited November 11, 2013 by Steve M

[Steve M]

*Now on to LanschePlasmaGuy/Bryan's fabulous audio system. We get an invite to drop in on Bryan on our way to Melbourne's Tullamarine Airport on Monday 21 October - the last day of our little sojourn over East . The flight back to Perth departs at 8.00pm so we feel we have plenty of time to spend with Bryan (or so we thought until some airplane dramas unfold, but more on that later). The four of us Steve, Tuyen, Mario and Terry arrive at Bryan's place mid-morning and an enthusiastic speel is given by Bryan about the philosophy and technology behind the Direct Drive Electrostatic Acoustat loudspeaker. Historically, I think the concept was first tried by the famous British valve amplifier guru Tim de Paravicini of E.A.R, who in the 1980's designed and built a direct drive OTL (Output Transformer Less) amplifier to use with his much loved Quad Electrostatic loudspeakers. Harold Beveridge and Acoustat in the USA also tried the Direct Drive concept, with limited success (the Acoustat servo amps didn't sound good and were notoriously unreliable). Roger Modjeski was on the design team for Beveridge at the time. The whole idea being that direct drive eliminates the passive components in a normal electrostatic speaker, these components being the transformer, rectifier block and crossover ...simplifying things for the signal to pass though, but more importantly direct drive gets around the impedence problems and distortions caused by transformer saturation and, the wildly fluctuating impedence curve from 1-70 ohms (depending on the music signal being played) that all normal electrostats suffer from. Direct drive removes all the things that give the amplifier driving the stat a hard time, things that make the amplifier distort and struggle. With direct drive the speaker kind of sees the signal directly from the plates of the valve, as a 5kV voltage source, with no components in between the amp and the stat panel membrane making the sound like ...there is nothing purer. I may not have this part entirely correct, so someone else can add to this comment if they wish?

Bryan also talked about the elegance of motion of an electrostatic membrane, the coupling with the air, the lack of weight (like a plasma driver which is the ultimate transducer) and the lack of mechanical distortions with a stat as compared to the clumsy operation of cone drivers and boxes. This was like dejavu for me, it was like hearing myself speak, as I have over the years since 1995 expressed many of the same thoughts in my Blog Site and other ramblings on audio forums such as the old Apogee Users Forum (great ol' website with a lot of information, btw).

Bryan's audio system is like Rab's (who sourced his via Bryan), it consists of Roger Modjeski - Reference Audio Mods USA, Direct Drive OTL valve amplifier(modded by Bryan with better caps and bypassing parts of the circuit, for a cleaner signal path) for the electrostats; a highly modded Tram2 DHT valve preamplifier; a modded CEC/CDC TL-1 Transport (which was absent as it was being further modded); a TDA1541 Audiocentric/Killerdac; a highly pimped Lenco turntable that he had thrown about $7K at, with supreme bearings etc; a Reel to Reel tape deck(make unknown?) and on loan from Jaspert/SNA a 47 Labs Shigaraki CD Transport.

A couple of other points, firstly Bryan's system is set up in a large bedroom of about 4.5m x 6.5m x 3m high ceilings with random soft furnishings (including his lovely blue British Shorthair cat named Luna, who's on a leash so she doesn't get zapped by the stat ...a real little character that cat ). There are some homemade diffusers scattered around and, the room to me sounded very good, the music sounded inviting and was presented cleanly and in a focussed manner in the listening position.

Secondly, a few words about Bryan's Acoustat panels which have been tuned by him to great effect. The Acoustats were chosen over Martin Logan and other stat panels for several reasons. They are extremely robust and indestructable, they have moderately thick membranes for better bass, the membrane coating has very good damping properties, they have a good stator gap for better membrane travel (for better SPLs and bass output) and most importantly - Bryan is able to implement an electrical transmission line with these panels, because of the individual vertically arranged stator wires ( which are unlike any other stat on the market, which in the main have perforated steel plates). Over many months Bryan has experimented with and worked out certain resistor values on the Acoustat stator wires, that gives the exact sound that he is after. The resistors act like crossover filters on this design, allowing you to tailor how each panel responds to the music signal (there are four panels per channel on this Acoustat array), the electrostat is about 1.2m x 1.2m in surface area, which makes it quite big (impractical in a domestic situation) ,however it plays VERY LOUD and with IMPACT ...unlike any other stat that I have heard.

Kudos to Bryan on his excellent tuning skills of the Acoustat panels . It demonstrates good intelligence on his part and a great set of Golden Ears. That's two Golden Ears that I have met on this journey, I am beginning to think that between Bryan and Steve Garland's golden ears, that it is like a Shootout at the OK Corral between these two ...a very close thing and respect to both of them on two superlative music making systems.

Here are some pictures of Bryan's room and system:


Vintage Western Electric compression driver, worth circa $5K ...Tuyen knows what it is?

Bryan's diffusers, something tells me Bryan has been to North Africa or New Guinea ...

Spare set of Acoustat Model two spkrs


Bryan's CD transport of choice a modded CEC/CDC TL-1 ...generic web photo.


Well, as to the sound of Bryan & Rab's system (more so Bryan's because of the room and the proximity of the speakers, like headphones but the image is in front of you and not in your head, which is a good thing) ...in two words the sound is raw emotion, 'live' or very close to an 'alive event' in the best sense of the words. VERY, VERY low distortion, there is the instruments-the humanvoice-and YOU, no constructs or mechanics in the way, I have heard nothing like it except for a pair of Yamaha NS1000 monitors (at their best and in the right conditions), the ER Audio stats or Mick Maloney's Lipinski studio monitors (@ $9K+ RRP) or some of the finely tuned WAR Audio PHL/Accuton speakers ...and these other speakers only do it to a certain degree. On the one hand you want to talk about the accuracy of this speaker and on the other, about a connectedness with the music and reality. I am gobsmacked about the absence of the electronics, you don't think of boxes, materials, the science - or any contrivance or box contraption. My mind was thinking, this is about as REAL as reproduced music gets. Some may hanker for more impact, like Tax's awesome Duo/Trio system, or the sheer naturalness of SV's system, but for me the essential voicing and lack of distortion and purity was evident.

Anyway I am soap-boxing and harping on a bit here, but you need to have a listen to Directly Driven Stats if you can. I hope that it will be a paradigm shift for you as it has been for me, these set-ups are totally impractical in a domestic sense (and dangerous), but what the heck there's a definite future in these speakers for me so you will hear more about it from me.

Cheers,


Steve.


*This thread will conclude with Part 7, a brief photo essay of the Melbourne AV & HiFi Show.




*Our departure out of Melbourne to Perth didn't go too well ...firstly, at 5pm from Bryan's place we call a Melbourne taxi to the Airport for a flight at 8pm, plenty of time you would think. Two hours later and numerous phone calls (x8) and a taxi still doesn't turn up! So on to Plan B, LPG/Bryan will drive us to the Airport, of course with four guys + Bryan and copius amounts of luggage what car does Bryan drive? a Mini Cooper, go figure! We jettison one passenger, Tuyen, because his flight is later at 9.30pm, pile into the Mini Cooper, twisted and contorted in our seats, tyres and suspension scraping on the wheel guards because of over-loading. Mario checks his phone messages on the way in the car, guess what?? Virgin Airlines have cancelled Mario & Terry's seats on the plane, its overbooked, they leave at 5.55am in the morning instead! Mario is spewing! taking several pieces out of the Virgin Staff, I tell him to calm down, I arrive at Tullamarine with only 5 minutes to spare sitting in my plane seat, phew I'm all right, but what a joke! Mario and Terry get home one day late ...them's the breaks with cheap Virgin air tickets!

Edited November 28, 2013 by Steve M

[Steve M]

.......................post amended.

Edited November 8, 2013 by Steve M

[matt200sr]

 I am gobsmacked about the absence of the electronics, you don't think of box-material, the science- or any contrivance or box contraption. My mind was thinking, this is about as REAL as reproduced music gets. Some may hanker for more impact, like Tax's awesome Duo/Trio system, but for me the essential voicing and lack of distortion and purity was evident.

 

 

 

Killer post Steve!

 

The experience must have been mind blowing.

[tuyen]

Love it! Well written Steve. Thanks for the effort.

Loved the presentation from Bryan's setup. I reckon it's one of those systems that makes you think and reevaluate what you previously may have thought was not possible from stereo music playback setup!

The experience has piqued my interest in OTL based amps too. You are a bad man Bryan!

[Willco]

Great writeup and pics!--thanks again for taking the time for such a comprehensive posting--this harkened me back to a system I had in the early 80's

 

I drove my Dayton Wright XG8 ESL Panels from the Primary of the Transformer 0.25 Ohm impedance

 

I used two Electro Research A75's bridged-- drove them fine-unfortunately the Panels were never as rugged as the Accy's and failed after time-in spite of the SHFX Gas they were enclosed in.

 

Keep up the good work

 

Willco

[Dr Good Vibe]

Good shots of Bryan's direct drive he and Graham we reover quite a while ago talking about them hmmmmm still like to hear them B when ok.

[sir sanders zingmore]

This thread just keeps giving

Awesome write up Steve. Thank you.

[Steve M]

Thanks Steve for sharing with us the great journey you guys had.

This is the sort of thread one can read over and over again such is enthusiasm and great gears on show

Thanks Victor and others for the kind words. Sorry that we were not able to catch up this time to hear your Marten Bird speakers with Accuton ceramic drivers.

In case people are wondering, I did try and hook up with people like vmhf/Victor with VERY hi-end and high $$$$ systems, in order to try and expose my ears to some upper echelon audio systems. I do want to hear everything out there, things like Avalon Isis, YG Anat, Wilson Alexandrias, Evolution Acoustics etc.

Maybe next time ...

Regards,

Steve.

Edited November 9, 2013 by Steve M

[b.d]

Hey Steve. Really interesting reading.

 

Wanna ask, did either Brian or Rab run these with non-OTL amps at any stage, I'm wondering how much of the magic they credit to the OTLness of the amps specifically?

 

Also, do you feel the Acoustats are a better design in any way than Quad, ML, ER or Kingsound etc?

 

Last question if I may...do you know how easy and at costly an OTL approach to say DIY ER-Audio panel would be?

 

Cheers

Bevan

[David.M]

Great read, written with the same passion as that obviously held by the owners of the systems you visited

[hedalfa]

Very thoughtful write up Steve M

 

It worked well in conveying the unique equalities of each system.  A good sense of being there, assisted by the photos.

 

Yes feel your pain guys... Virgin has done that to me because the computer took me off the schedule even though there were seats on the plane and it was the same plane I had travelled in from Canberra which was delayed. They wouldn't budge and by the time they let me speak to a manager the plane had departed. I was furious!!! Not much help the manager admitting they had done the wrong thing. I lost a whole day off work and wait in Sydney of 6 hours till the next plane...

Edited November 9, 2013 by hedalfa

[ENIGMA]

Thanks Victor and others for the kind words. Sorry that we were not able to catch up this time to hear your Marten Bird speakers with Accuton ceramic drivers.

In case people are wondering, I did try and hook up with people like vmhf/Victor with VERY hi-end and high $$$$ systems, in order to try and expose my ears to some upper echelon audio systems. I do want to hear everything out there, things like Avalon Isis, YG Anat, Wilson Alexandrias, Evolution Acoustics etc.

Maybe next time ...

Regards,

Steve.

Great write up Steve, it is fantastic to experience and get to know other peoples journeys, from the vintage, exotic to ultra performance.

In the end, there is no one system over the other, they all have personality, emotion, character and wonderful memorable experiences - just like their owners.

And it is great to read about the interesting owners as well who were kind enough to share and open their doors.

P.S, you did miss one .......

[Steve M]

Hey Steve. Really interesting reading.

Wanna ask, did either Brian or Rab run these with non-OTL amps at any stage, I'm wondering how much of the magic they credit to the OTLness of the amps specifically?

Also, do you feel the Acoustats are a better design in any way than Quad, ML, ER or Kingsound etc?

Last question if I may...do you know how easy and at costly an OTL approach to say DIY ER-Audio panel would be?

Cheers

Bevan

Hi Bevan,

How's the weather in Copenhagan? It's predicted to be 37C here in Perth today.

You ask some trixie-questions there and I expect nothing less from you! ;-))

Those systems with the Modjeski OTL amp and direct driven Acoustats are not mine and I wasn't given any A-B testing with other amps etc. to consider the effect of OTLness/OTLosity(?) of the sound. All I know is that the idea of running stats directly using OTL amplifiers is one of those HiFi holy grails, supposedly the ultimate, as you are using a simplified valve circuit without the limitations that output transformers might impose. Certainly, the guys using them Richard and Bryan are convinced of the approach and from what I heard this is the nearest you are going to get to hearing a 'distortion-less' home hifi system. This set up is amazingly PURE sounding, like drinking from a mountain stream, it may confront some people ...but not me, I loved it.

As to the other types of electrostatics you mention, I've had or heard them all (not the Kingsound) including the big Soundlab A1 and while they do similar things - it is not to the same degree of the directly driven Acoustat. While I like stats a lot as you know, I am not stuck on any one technology, and will use and play with horns and conventional cone-box speakers from time to time. To be honest sometimes stats frustrate me with their limitations, they annoy me with their inability to play with full impact, to fully flesh out the lower midrange and upper bass region, the slight plasticky tone they all seem to have etc. All minor things really, if you appreciate their strengths which is purity and refinement?

The Modjeski OTL Direct Drive Acoustats essentially eliminates all of these perceived problems with stats. They will play bloody loud 100dB+ and with authority and force and the frequency response is 25Hz- 50kHz apparently. That said, they will not play at ear bleeding levels nor with as much impact as a pair of BIG capable boxes, but nearly. I saw some coronal discharges in the panels (an intergalactic light show) in the dark, while Bryan was playing his at very loud levels.

As to costs for this system, it is about $5K for the Modjeski OTL amps and about $2-3K to source the Acoustat panels and other bits.

Steve.

Edited November 10, 2013 by Steve M

[b.d]

Thanks Steve. The OTL amp approach might sweeten the deal enough for me to try stats one day, perhaps a big array of the ER diy panels would be a relatively cheap entry point (not the bad price you mention for the Acoustats, but out of production I believe). Would the amps need to be built specifically for the speakers I'm wondering...anyway hope someone else goes first, I've sworn of speaker projects for a while

[statman]

Bevan

I've been meaning to try the direct drive concept for years, Steve's enthusiasm for it has got me drawing circuits- probably use big power triodes though, and I need to speak to Rob at ERaudio re the panels. Might be my last big project.

Here's something interesting, a little different to what I have in mind, but food for thought. 

 

 

845-20B.pdf

[b.d]

Excellent Mick, thats the kind of thing I was hoping to hear. Glad you agree we can all blame Steve for this. Myself I just had a TPL-150 Synergy horn to go before hanging up my router, at least before this thread came along. 

[Steve M]

I am told the Modjeski OTL stereo amp can be used on any electrostatic up to a certain size. Unfortunately, it is the expensive part at $5K - no way around this for us plebs (Mick excluded as he can build one). Apparently, it is quite hard and dangerous to build a stable OTL amplifier outputting 5000v DC and the Modjeski amp contains some specislized transformer winding techniques to overcome this.

Roger Modjeski makes two Direct Drive amps, a stereo version able to drive up to four Acoustat panels per channel and, a monobloc version @ $8K able to drive twice that. I see one of these amps in my future, to explore all manner of stats including Acoustat, Quad 63, ML and ER Audio Acorns. As I understand it, the principle is that most stat panels are three wire systems, wires for the two metal stators and another for the moving membrane and you simply hook this up to the Modjeski amp. After this, you need to filter and tune the panel to how you like it, Modjeski recommends using an outboard equalizer a Behringer/DBX/DEQX/MiniDSP, whereas Rob Mackinlay and LPG/Bryan use resistors which act as filters attached direct to the panel. Rob also has a big properly done passive crossover on his ultimate Acorn speakers. Bryan is employing an electrical transmission line on his Acoustats. The panel has variable resistor values on the panel wires (you can only do this with the Acoustat), so that the panel focusses treble response at the middle and the mid-bass is transitioned to the outside of the panel. Rob reckons this might introduce some inter modulation distortion, IMD, whereas Bryan's ears are telling him it sounds better that way.

Anyway, I take no credit for any of this having contemplated doing it over the years, but it is Bryan who actually took the brave step and went ahead and succeeded with it.

Steve.

Edited November 11, 2013 by Steve M

[Dr Good Vibe]

Have built in the past 3 way panels with the treble in the middle not as good as one large full range but never tried the direct drive yet there are a number of circuits out there Sonorus has an excellent example have spoken to them on building, they have spent many years on getting theirs right very helpful guy.

Hard thing is the entire special hi voltage parts you need don't try the "that will do" you'll die or someone else will.

[Steve M]

Great advice from the Good Doctor, as I recall you are the guy with the beautifully built mega DIY stats that look like the Metaxas Emperor electrostatics ...well done.

The 5000v is very scary definitely, that is why buying a ready built amp like the Modjeski OTL is essential, though you still have to watch out for the 5kv coming out of it. This might be a silly question, but do you think the house ELCB (earth leakage circuit breaker) will protect you from electrocution - not that you ever want to test it ?!?!?

Steve.

[sir sanders zingmore]

Bryan can comment on this better than I, but he assures me that the difference when he went from transformers to direct drive was absolutely enormous. Makes sense too

[b.d]

Steve I've always been most interested in the idea of something approaching a floor to ceiling array of staked panels(if using the small ER ones) with a digital XO as a say 5-way system where one has the ability to digitally time align each of the panels..but these specialist amps would put that idea beyond my means if I needed 5 pairs of them...anyway I'm happy to sit back and watch for a while, hopefully other SNAers will pick up the ball. It might not be anything really new this OTL approach but its always interesting reading when speaker-building approaches outside of the ordinary start gaining traction, some excitement amongst the otherwise mundane. (would be also most interested to hear a conversation around possible benefits of the Amarra IRC phase and amplitude correction on these ESL after hearing what they did for Micks panels, and my dipoles, but I suspect we're still few in number)

[statman]

Excellent Mick, thats the kind of thing I was hoping to hear. Glad you agree we can all blame Steve for this. Myself I just had a TPL-150 Synergy horn to go before hanging up my router, at least before this thread came along. 

 Oh yeah I forgot about the Red Spade Synergy horns I ordered, but no idea when they will happen, gone very quiet.

The Sonorous looks VERY interesting, Steve I reckon you should start a new direct drive thread where we can form ideas, concepts. 

[strony]

Thanks for sharing this adventure - this thread has been one of teh best in SNA in a long, long time - what the hobby is all about I reckon.

 

Cheers

Andrew