It drives me NUTS!

… when I can’t find something in my own house. I spent the whole of Sunday (I exaggerate, but only slightly) looking for the manual for my Pioneer AV Receiver/Amplifier. This receiver is a very sophisticated device. In particular it has a functionwhich sets the levels on all the loudspeakers automatically. To do this involves connecting a microphone to the receiver, then sitting in the listening position, and then invoking the level setting function using the remote. The receiver then plays white noise through all the speakers in turn (six in my case: two at the front, two at the back, a subwoofer and a centre channel speaker for voice), and adjusts their levels correctly.

Getting this function set up requires careful study of the manual. Which I cannot find. It is not with all the other manuals, in the standard place set aside for manuals. Where can it be? And where is the microphone?

Answers on a postcard, please, before I go stir-fry crazy and burn the house down in a fit of pique.

Stereophile

Hi-fi mags (as they used to be called) are a guilty pleasure for me. I picked up the December issue of “Stereophile” magazine in Austin airport, and read it on the plane.

Despite that fact that most of what is said in the text is a load of nonsense, it’s oddly nice to read: reviewers gushing about equipment interspersed with photos of high end loudspeakers, tube amplifiers, turntables and so forth.

The high end audio world has always been full of deluded individuals who have more money than sense. The hifi magazine reviewers say things like this:

“In our round up of best pre-amplifiers of 2008, the top position was hotly contested between the Naim Superbus Clarity XL/3i and the Architectural Audio Alchemy XTR. In the end the Naim’s uncanny ability to transport the listener to the recording venue won through.”

What a bunch of codswallop! Even the best test gear has trouble measuring the distortion levels in modern amplifiers, which have frequency response curves essentially flat from DC to several hundred kHz. Uncanny ability indeed.

Then we have the daftness surrounding audio and power cables. You can pay thousands of dollars for a special power cable that goes between the wall socket and your amplifier (or whatever). Yet they don’t mention that the house wiring to the wall socket itself would need to be of similar quality for the cable to make a difference. Despite this, such power cables are lauded as imparting “an astonishing clarity to the treble”, or removing “the woolliness of standard cables”.

My arse!

But what about the loudspeakers? Some of these cost upwards of $50,000 the pair and beyond! And you know what? When I’ve listened to such costly speakers they don’t sound any better than models at a tenth of the price – you are paying for a name, and the massive overheads these small speaker building companies have.

Having said all that, I would really like a pair of these in my living room:

The Planot Loudspeaker Prototype

I made a prototype of the Planot Loudspeaker this evening … and it worked. Actually, how could it fail to work – the principle is foolproof, it’s just a question of how well it works:D

I took an old Micropolis hard disk’s actuator arm and voice coils, together with the magnets, and mounted them on a board. (For some reason this disk had two voice coils, and two magnet pairs, with the voice coils wired in parallel.) The voice coil resistance was about 5 Ohms.

Then I cut a 15″ length of 1/2″ square balsa wood and glued it to the top of the arm, central to the bearings. Here’s a photo:

I attached a pair of wires to the voice coils, and powered them up with the amp. The music played surprisingly loud, and brightly. There was a bit of vibration of the board, and I suspect the balsa wood was fluttering a little at the top, since it was unattached there.

The thing works fairly well, and for a cobbled together experiment it’s great! I took a little movie which you can see and listen to here:

Electrostatic Loudspeaker

Take one 9V AC Wall Wart, and attach the output leads to the 0-8V taps on a 384V transformer you picked up at a surplus store years ago. Connect the 0-384V taps to a voltage quadrupler network you have fashioned from HV silicon diodes and .05 uF HV capacitors, so bringing the voltage up to around 1.5kV. Don’t attempt to measure the HV directly, but use a voltage divider built from a chain of a few 10MOhm resistors.

So far, so good.

Now take a sheet of 2ft by 4ft perforated metal, and super-glue to it strips of 1″ wide 1/16″ thick insulating plastic, so that the strips are along the edges of the sheet. Do the same to a second sheet of perforated metal and set the pair aside.

Purchase some plastic film for windows, the sort you stick on and then make tight with a hairdryer, cut a 2ft by 1ft piece and tape it to a board. Sprinkle the surface with powdered graphite, and rub it in with cotton balls. Place a couple of pennies on the film and measure the resistance between them, which should be a few hundred kOhms or greater, at which point you can stop rubbing in the graphite, and hoover up the excess.

Apply double sided sticky tape (provided with the plastic window film kit) around the edges of one of the metal sheets, on the insulating strips, and then place the plastic film down against the tape, so securing it. Remove the board, and trim the edges of the plastic film.

Obtain the use of a hairdryer, and carefully blow hot air over the film until it tautens to drum tightness. On the other metal sheet, super-glue a thin metal washer to one edge of the plastic insulating strip, then super-glue the whole sheet down onto the sheet with the plastic film.

Ensuring that the HV supply you made earlier is turned off, attach its +ve terminal to the centre tap of the high impedance winding of an audio tube output transformer, and the -ve terminal via a 20MOhm resistor to the metal washer and so to the plastic film diaphragm sandwiched between the metal sheets. Connect the other taps of the winding, one to each of the metal plates.

Turn on the HV supply, keeping hands well clear, and watch little sparks jump between the plastic and the metal for a while, until the dust has burned off. There should be no sound as yet.

For the moment of truth, attach your MP3 player to an amplifier, and the speaker output of the amplifier to the low impedance winding of the audio transformer.

Music! Clear, transparent, beautiful music. The sound of an electrostatic speaker is startlingly neutral. There is simply no distortion, unlike with normal speakers. The essentially massless diaphragm is especially good at reproducing the upper frequencies.

Just don’t touch *anything* while it’s operating.

Zzzzzzap! Try This At Home.

Take one 9V AC Wall Wart, and attach the output leads to the 0-8V taps on a 384V transformer you picked up at a surplus store years ago. Connect the 0-384V taps to a voltage quadrupler network you have fashioned from HV silicon diodes and .05 uF HV capacitors, so bringing the voltage up to around 1.5kV. Don’t attempt to measure the HV directly, but use a voltage divider built from a chain of a few 10MOhm resistors.

So far, so good.

Now take a sheet of 2ft by 4ft perforated metal, and super-glue to it strips of 1″ wide 1/16″ thick insulating plastic, so that the strips are along the edges of the sheet. Do the same to a second sheet of perforated metal and set the pair aside.

Purchase some plastic film for windows, the sort you stick on and then make tight with a hairdryer, cut a 2ft by 1ft piece and tape it to a board. Sprinkle the surface with powdered graphite, and rub it in with cotton balls. Place a couple of pennies on the film and measure the resistance between them, which should be a few hundred kOhms or greater, at which point you can stop rubbing in the graphite, and hoover up the excess.

Apply double sided sticky tape (provided with the plastic window film kit) around the edges of one of the metal sheets, on the insulating strips, and then place the plastic film down against the tape, so securing it. Remove the board, and trim the edges of the plastic film.

Obtain the use of a hairdryer, and carefully blow hot air over the film until it tautens to drum tightness. On the other metal sheet, super-glue a thin metal washer to one edge of the plastic insulating strip, then super-glue the whole sheet down onto the sheet with the plastic film.

Ensuring that the HV supply you made earlier is turned off, attach its +ve terminal to the centre tap of the high impedance winding of an audio tube output transformer, and the -ve terminal via a 20MOhm resistor to the metal washer and so to the plastic film diaphragm sandwiched between the metal sheets. Connect the other taps of the winding, one to each of the metal plates.

Turn on the HV supply, keeping hands well clear, and watch little sparks jump between the plastic and the metal for a while, until the dust has burned off. There should be no sound as yet.

For the moment of truth, attach your MP3 player to an amplifier, and the speaker output of the amplifier to the low impedance winding of the audio transformer.

Music! Clear, transparent, beautiful music. The sound of an electrostatic speaker is startlingly neutral. There is simply no distortion, unlike with normal speakers. The essentially massless diaphragm is especially good at reproducing the upper frequencies.

Just don’t touch *anything* while it’s operating.

The Acoustic Triangulators – contd.

The speakers are coming along. The next step is to mount the four oval drivers in each speaker, wire them up, stuff with fibre, and make some polarity checks, and then attach the bases for a first audition.

Pablo and Band Saws

We have a new fish! I haven’t had a chance to photograph him yet, but he must be settling in nicely because he has gone to sleep in a comfy hole in the reef. Here is one of his friends:

Thinecanthus Aculeatus

No prizes for guessing why we called him Pablo.

Tomorrow I am off bright and early (well, 9am, early enough on a Sunday) to the semioticbovrils for a bit of woodworking. On Friday bovril and I went down to Arroyo Expensive Wood Planks and I dumped 150 bucks on two nine foot lengths of cherrywood and a piece of cherry-faced plywood. The plan is to construct the Acoustic Triangulators! Of course, photos of the work will be forthcoming, especially resulting from opportunities for gory snaps showing bloodied ends of fingers lying in the sawdust.

The Acoustic Triangulators

Every few years I get the urge to build a pair of loudspeakers. This time I am doing something about it. I read an article in Electronics World that suggested a line array of elliptical drivers produces a very good sound: far better than the performance of the individual units, since the inhomogeneities between them are cancelled out by driving them in parallel.

So I ordered eight Onkyo units at about a buck fifty apiece from Parts Express, and they arrived on Friday. I made measurements of their response using Pink Noise with my IE33 handheld spectrum analyser, and they look quite decent … rolling off below about 100Hz, and above 10kHz, but still useful output beyond those limits.

Then I drew up a cabinet design. Each cabinet will be triangular in horizontal cross-section, and will be made from something like cherrywood. They’ll be about 4′ tall, sitting on circular wood plinths. I need to show the plan to bovril, because I’m hoping he can help me make them. I certainly don’t have the tools to make the 30 degree cuts required, not to mention the four oval holes in each cabinet, but he does. In fact his garage looks a bit like Norm Abram’s workshop in The New Yankee Workshop!

The speakers have already been dubbed “The Acoustic Triangulators ®”.