Sound And Torsion
There are a few approaches to speaker systems, (the current preoccupation here) and it's worth noting that dual-concentrics are only one. But if you're set on something like a single-source, full-frequency driver that need not compromise... or can't see trying to blend a stew of differing driver components, the Tannoy Monitor Gold dual-concentric is a reasonable starting point.
In all honesty, I'd rather be talking about esoteric phono cartridges and tube amplifiers, but you do need speakers. And, you need amplifiers to drive those speakers. Which should come first ?
Well, on the evidence of listening for half a century almost, I'd modestly propose that --- counterintuitively, and it didn't seem so to me at first, but--- the amp is the more "diva" component. Once you have an amplifier type with finite power and a given sound signature, it excludes a number of speaker-system types immediately. At least that's how it appears to me these days. In the early days I'd always gone with the idea of the speaker as the voice of the system, consequently the first choice to be made. It made sense that the voice of the system should be catered to, in the later choice of the amplification.
That was when the general premise was that the amp would be solidstate, possibly separately biamped, and endless watts simply a matter of running up the credit card a little bit further. And as it stands now, most of the world has lowered its standards to that steely, bleached solidstate sound. All theoretically in the interest of sonic cleanliness and reduced distortion. But like wheat-free muffins or decaf coffee, that reductive approach ends with an unsatisfying compromise -- in this case a lifeless or reanimated aspect to the sound. To my ear anyway.
We don't need to settle for all that, or take the ambiguous deal with the devil that offers thundering THX style body-blows, laserbeam high frequencies, and leaves the life and the heart out of the music.
This isn't ice-hockey or extreme wilderness adventuring-- it's a bit more subtle than that. Vacuum tubes offer a viable alternative, and one that hasn't got subliminal dissonances in its harmonics. Likewise, that familiar need to keep turning up the volume (with solidstate) disappears magically with good, small-scale tube amplification. The amplifier that renders a full-harmonic picture of the original recording --- (ruling out super-exotica highend solidstate).. is often enough a medium-to-low-powered vacuum tube unit. Of which there are many families and sound categories to explore. Simple enough, really, and just to be historically accurate, vacuum-tubed transformer-coupled amps are the original instrument that once powered all loudspeakers.
So as is often the case in system-building architecture, the least cooperative element dictates the terms to the rest of the chain. If it is a case of low-wattage vacuumtube amplification providing the least common denominator, or the lesser offender of all error-prone contestants, the interested user can do much worse than to consider a Dual Concentric driver. Tannoy alnico monitors are a well-designed and efficient solution to the speaker part of the equation. The Tannoys were designed in the tube era, and suit that kind of amp very well.
All that's left is to house those Tannoy drivers in appropriate enclosures, and that's where this project picks up. Along with cabling, stands, spikes, binding-posts, crossover components, construction, bracing, fiber-fill, finishes, and all the other countless considerations.
The entries here feature the most-recent on top.
If you want to read in sequence, scroll down and select the earliest,
February 2010 post, and begin there (just the way this template works).
Saturday, September 3, 2011
Only Seventy Five Hours
The run-in period here involves almost the whole signal-chain from the poweramp outwards : the kimber 8tc cabling with newly terminated, replaced postmaster spades, the cardas binding posts, all the new elements on the crossover boards, and the many newly-made solder connections. So 75 hours probably isn't time enough to tell.
We've been thru all the well known phases: the initial, coarsely blunt sound, that refines and refines till it's gone too far toward detail and brilliance (of the annoying kind) ... Then the few false 'settle-down' periods, where it will fall back to the middle but then goes off again on some other peaky or tilty drift ...
At this mid-point it's finally sounding really good but with one distinct drawback. Recordings that are known to be excellent are rendered in all-new 3-D technicolor, while recordings known to be so-so are sounding blah. This is the worst kind of performance, really, because it tempts you to play program material that is pretty flawless sonically, immune to the increased scrutiny of all that new-found focus and detail ... Rather than choosing material for musical quality.
I'm a firm believer that it should be entirely the other way around, with performance that gives it's best with middle-of-the-road quality recordings, only sounding a touch worse with poor ones and still sounding very good with much better ones. If your system promotes or incentivizes the choice of audiophile-quality recordings, your mind and soul may be at risk.
Half the most inspiring music ever recorded was done in a slapdash fashion, either due to cluelessness or neglect, but it can't be denied on "sonic" grounds. You should be able to feel your soul thrill to the high & lonesome thrum of an early Louis Armstrong horn solo, in spite of it's origins on non-audiophile mono recordings.
Part of the allure of the Tannoy driver system is it's effortlessly coherent yet forgivingly warm sound. Let's keep that as the goal and never get audiophile with this.
It is likely this all middles itself out, with a bit of oxidation and time, to a softer, more graceful but still dimensional sound. An older-but-wiser version of it's present self. That's generally the way it works-- newly-constructed generally equates with overly-detailed, which favors faultless recordings, where there's nothing to notice that's off. Once things have settled a bit, like a new car after a couple months of steady use, the sharp edges are rounded away and the real character of the thing is a little more honestly apparent.
4:55 pm pdt
Tuesday, August 30, 2011
New Crossovers In Operation
Burning in newly-constructed crossover boards, new photos at right.
Took about three challenging weeks to redesign positioning aspects, but then just a couple days to do the actual reconstruction. Shifting a 70's terminal-board setup with small industrial parts to present-day 3D approach with large audiophile parts was a lot to consider for the first time.
Crossover components are now working in closer proximity, and from both sides of the board; small wood enclosures have been built and fitted to backs of speaker cabinets to contain larger unit size. Crossover units are still physically external to the speaker cabs, but mounted piggy-back to lessen cabling.
Signal path has been shortened, unused terminals and jumper leads have been hardwired or eliminated. New high-current connections are a cleaner fit, and the physical mounts for components are way more luxurious. (I did leave in place a short set of leads on the small #3121 inductors, as a precaution for hum, as in the ability to rotate or tweak ... but no worries there, so next time those leads will be eliminated too...) Solens are running the lowpass duties, and Obbligato Golds comprise the high-pass arrangement; new Mills wirewound resistors have replaced three series-connected originals with two combined-value units. And the original Tannoy stock autoformers & inductors remain.
Every effort has been extended toward keeping to the exact values of the original Tannoy circuit. As a small gesture toward voicing, though, I cushioned the Highpass parts with 1/8" silicone closed-cell foam (as used in outdoor electrical boxes for gasketing) and strapped securely with nylon cable ties. The Lowpass parts were mounted direct against the boards with no compliant bedding. This arrangement seems likely to me to moderate Treble and soften the highs a tiny bit, while leaving Bass as is, an adjustment to be validated by listening. I'm very familiar with the previous sound of these drivers and cabinets, so have some expectation of making a reasonable judgement by ear. We'll see if this works as planned ... After about a hundred hours or more of burn-in.
Tuesday, July 12, 2011
Cabinet Extension In Progress
Spring-summer project: Photo has left-hand speaker upside down to show perfed areas. Newly added, some extension to cabinet backs, perforated previous back panels within. Also perfed bottom panels, which will get another layer of ply to form new base.
These changes shift the interior reflective surfaces again, making a more labyrinthine chamber to disperse direct reflection and standing waves. Also adds some valuable extra volume to deepen tone overall. As noted below, once I got the Tannoys up on their stands, I noticed that the bottoms were more resonant than they should be; sitting against the carpetted floor this hadn't been noticeable.
In a more elaborate rendition, I would have done at least the backs as torsion panels, but in order to get this on the road I just added backs of 3/4 inch baltic birch, which seems to suit the bill (and takes quite a bit less time, to be honest). The base panels are fine as a composited perf panel clamped & glued to another non-perfed ply panel, very rigid and non-resonant. Each little adjustment, whether complex or minor, seems to add to the depth and solidity of the sound image. So far, so good.
Now crossover again, enclosures for same, new cable, binding posts, and beyond......
1:53 pm pdt
Saturday, March 19, 2011
Dismantled the cabinets and shelved the Tannoys for the moment, in the interest of doing a few long-wished-for improvements. The end of the week was spent boring out mass-relief holes in the internal structure of the cabs and doing the same to the single-layer bases, which will now become double-layered, holes to the inside, clamped and glued. This will add a few more cubic inches to the interior of the enclosures, while lowering resonance tendencies of the base panels, only apparent since the cabs have gone up on their risers. In general another layer at the base will increase rigidity & stability.
At the same time I'm refitting the Tannoy Crossover units to accept Cardas binding posts, eliminating the relatively thin Tannoy speaker leads. Cabling from amp to crossover will now be a length of Kimber 8tc cable, which should be something of a clear improvement. Before we move on, thought, it should be said that if you use that thin Tannoy lead bare-ended, straight into your amps outputs, you could do a lot worse. Pre-highend cable-think though it may be, at a short distance it's fairly good quality. And it's free with the crossover, so why not start out using it. (Do cut back a few inches to get beyond the oxidation layer and start with freshly tinned bare ends.)
The crossovers will now be mounted to the cabinets themselves, on the outsides near the base at the back. What's left in this department is to ponder the four-pin Tannoy plugs on cross-to-driver leads, which I've elected to keep. There is too much uncertainty in all of this to hardwire there and remove the 'modular' ease of setup with the plug / play arrangement that Tannoy had in mind. After all, tommorrow I might find a pair of Westminster cabinets on the doorstep; it would be nice to be able to quickly remove and re-install my drivers in a new cabinet. (Unlikely as that is, I've found that the versatility with the plugging helps enormously, with even a short round of improving the existing cabs, so no hardwire there. Yet.)
The cross-to-driver leads themselves, though, as terminated in the plugs -- hmm. Those are also that thin and limited original Tannoy wiring, and just kind of beg for replacement. But the Kimber 8 is probably too stiff and difficult to route for that application... Maybe the best fix is to search out another set of the Tannoy 4-pin plugs, and then re-wire with something a bit more supple & flexible than the Kimber ...
For this rendition of the Tannoys, though, it will be the full-freq Kimber braid from amp to Cardas posts on crossover, and then a shortened-by-half length of the original Tannoy lead from there to the driver. With the switches and wiring for tone control adjustments already gone, this should be a lean, clean, short-path arrangement.
Well, for now, anyway, it's all about expanding (by a little), mass-relieving, and then stiffening with extra layers for the cabinet floor. A happy coincidence is that the crossover enclosures I've rescued from another project, made of layered woods just like the Torsion Boxes themselves -- are going to stiffen the lower backs of the cabs just by virtue of mounting them directly onboard there.
It appears that once you've got some kind of relatively solid enclosures to work on, there is no end to the little "tailoring" adjustments you can make, some of which may even assist in a couple of fields all at once. Some of which open further issues that will need solving. Hopefully these are all undertaken with a keen eye to the usefulness per effort involved, and with some critical listening informing the choices. Photos when I get somewhere with this round of projects.
11:49 am pst
Thursday, November 25, 2010
No Brace No Bracket, No Nail No Screw No Glue
The old Japanese carpenters believed in using the structure of the wood itself, in a myriad of ingenious configurations, to interlock and form the vital skeletal structure of their project.
The Master would spend his days drawing plans, sections and elevations; his assistant would choose and mark out the correct lumber for the journeymen to cut and fit. A section of wood would be deemed suitable for a specific role according to many aspects. Grain structure and direction, physical orientation of the tree to the sun and prevailing winds, even where it stood on the mountain... All of which came into play when sizing up timber for, say, a 22-foot roof beam that was expected to traverse most of that length with supports only at the ends.
Nails and screws, bolts, various kinds of bracing and plates were available, but looked upon as last-resort kinds of fixes. The structure was meant to be held in place by its own internal logic, the forces & counterforces of stress, mass, and gravity.
Steel was meant to cut wood, not intermarry with it. Joints were likely to be Mortise & Tenon, sometimes pegged or slotted to fit other elements in the design. The master builders liked a clean edge and yet weren't afraid of the slight asymmetry that comes from an experienced hand negotiating the work. Manual is preferred to electric powered. The story goes that they would look down on sandpaper too-- steel leaves the edge clean when correctly administered, sandpaper only blurs the errors and makes the grain furry. High standards.
Our little risers have no relationship with the master builders of Japanese antiquity, but they can dream, can't they ? Oak hardwood cross-bars rest in mortises hand-cut into heavy fir 2x4s. The fit there is tight enough --yes, without any fasteners or glues--- that it cannot be easily shifted by hand and must be adjusted with a rubber mallet. The spikes will be sharpened brass rod, as mentioned below.
To be a hundred percent honest, I don't know if this is strong enough to do what it's intended to do. The spikes will be at the very outer edges of the crossbars, and there will be no wood touching the floor. Hope the hardwood of the crossbars is up to the job. We will see.
Oh, and I have learned a little lesson in cutting the mortises with chisels. When you misjudge your aim and pop out a heartbreaking little chunk of wood that was never meant to go anywhere, don't get too upset; find the chunk, put it in a small jar that you hold till after the major cutting work is over. Then glue the little chunk right back where it went before the mistake. Nine out of ten times it's an invisible error once corrected.
Wednesday, November 24, 2010
After too long a pause, I'm back at the Tannoy Project.
There are two sub-aspects that have made really extravagant demands on the time-frame of the overall job. First, the removable grilles, to be seamlessly spun with a standard mesh fabric covering, and then time-consumingly tweaked to the occasion via a very closely measured 'interference fit' ... Meaning that they are hardwood frames just flexible enough to fit over the outer rim of the Tannoy driver, without impeding or blocking performance, but strong & rigid enough to stay attached. Great idea, infinitely fuckaround-ish in execution. Once done, pretty nice, would'nt have anything less.
Second, the speaker-stands, or more reasonably, speaker risers, since they only account for about a five+ inch change in height. I've described the concept in the entries just below, and there isn't much more to say other than the astounding fact that the speaker stand itself accounts for about half the performance value of the speaker. My experience is that the Stand manages to elevate the performance substantially, or waste the effort put into the speaker design-- it's the foundation of the speaker design, so obviously, really, an indispensible component. As the power supply is to the amplifier, or the antenna to the rf tuner, the speaker stand enables or disables the capabilities of the speaker transducer. Maybe the simpler example is the turntable support : get it wrong and there's no end of contradiction in the playback. Get it right, and there is a hundred-percent validation of the design strategy.
All that sounds a lot of unnecessary hype, but I believe that the six months expended on speaker risers wasn't at all wasted; the results are fairly self-evident. If you have a look, they are considerably different than the usual run-of-the-mill disconnected tower mounts. After a brief interval, more on the speaker riser evolution.
But while on the topic, for what its worth, my system --and maybe yours--- is intrinsically based on the ideas of the "Ultra Fi" renaissance, founded by the likes of Kondo-san, Hiraga-san, Kimura-san, Shindo-san, and of course Harvey-Rosenberg-San.
To say that the revanchist Japanese outlook on all things audio has been influential--- alnico-full-freq-drivers, direct-heated-triode-amplification, transformer-coupled amplification, idler-drive LP playback ... would be a fundamental understatement. None of these is a Japanese invention, per se, but it was largely down to interest in Japan that these 'obsolete' technologies survived and continuted to develop. The west had thrown them away in the headlong rush toward weight, size and cost reduction.
In that light, the corollary study of Japanese woodworking and joinery-- disciplines I can never hope to master, but whose vision is all-enveloping.... have long been a revelation, and a tradition I hope to honor in my further explorations.
Stay tuned ; konichiwa.
11:26 pm pst
Wednesday, July 28, 2010
Midsummer Update, Finally
Already a couple months along into listening to the Tannoys –(the ‘s&t’ blog lags behind real time by anywhere from a couple weeks to a couple months)-- I really like them, and have to say they’ve been one of the easiest ‘vintage’ items to incorporate into a modern system. Fact is, I suppose, they’re not like the 1955 garrard 301 I use, or really old tube amps or tuners or something—the Monitor Gold design is from the late-60s, legitimately the modern era, and the actual drivers I have date from about ’71, so, not such museum pieces, really. Bolt down into cabinets and connect the cables, and you start to get the picture immediately.
I am really pleased to have gone down the Tannoy-Alnico route, they absolutely reward low-watt-large-transformer tube-amp sources without a glitch or regret. But I’m using a kt-88 ultralinear amp, whose circuit puts out a really muscular 8 watts; if it was a 2a3 or 45 amp, I think something like the French PhyHp drivers would be much more to the point.
But that’s the deal, I guess, putting together a system that works within it’s own limitations and doesn’t ‘disagree with itself’ .. internally. The idea of matched gear producing a coherent sound without much added or deleted along the way.
As to my enclosures, I’d give them a C- for execution (since I’m no cabinetmaker), an A- for inspiration (since I think the potential is all there, just not in this first rendition), and a B for sound, which is full, warm, articulate, substantial, weighty, but isn’t 1oo% served by the enclosures, which could do with a bit of rigorous testing / re-bracing per tests, that kind of thing .....
Occasionally I hear something that seems a bit like a resonance mode being reinforced by the structures. Most people wouldn't hear anything, but I do since the Tannoys are being inserted into an already very familiar system context, in the same space, with the same program material, lp or cd. Simple in-room testing procedures could advance things a lot; but I don't want to right now.
It actually comes to the conflict between creativity and science (and budget, of course)--- I’d rather just build a Version 2.0 before investing in whatever (software, microphone, etc) testing gear that would serve to verify my work or offer corrections to adjust the direction. Obviously, I should do both, testing and building, side-by-side for the Version 2.0.
For now though, summertime, and the listening is easy.
1:57 pm pdt
Wednesday, June 30, 2010
At the right, a test of the mortise joint for the levelling bases. Above, another varnish coat, some enhanced veneer plying on the front baffles, and next, a long-delayed listen.
2:42 pm pdt
Monday, May 3, 2010
Drying And Damping
Almost five days now since the varnish fest here, and even though the surfaces feel hard, they're still airing out and can be noticeably aromatic in a closed room. So I'm giving them another couple days for the first buff-down that will precede the second coat.
With no action on that I've been working on how to use plane, bar-clamps, and an improvised bench to square up the two-by-fours for the stands. That's coming along, and I'm seeing that the height of these stands will still be about six inches or so shy of Tweeters At Ear-level. What they will be, though, is a substantial enough foundation to build on, later, once more nice lumber appears for the height extension. Aesthetically, gracefully proportioned low-profile stands are the desirable look; adding extensions will never be as nicely low-key, and so we'll just have slightly low tweeter position for a start. They will, of course, be able to be tipped back to compensate via the levelling spikes.
I've decided that the Cookie Torsion Box back panel is a project best left to the future; for now I've cut and fitted quarter-inch ply sheets to the back of the wine-crate structure. Perhaps a layer of felt will be included in-between to make the panels deader sounding, too. The Cookie idea is still viable, and can just build outward from the ply backs I've got now. These need to be listened to again-- I haven't heard them since they were single-wall crates --- before any more hundreds of hours of work goes into them. But I won't be tossing the cookies.
Having time to think while the varnish dries is allowing me to have increasing doubts about whether it was right to leave the center spaces open in the grid area of the speaker wall construction. I keep thinking I really should have put damping material in there-- if not sand or lead, then just something to take the 'hollow' out of the equation. Even corrugated cardboard inserts, contact-cemented into place, would have surely damped those open spaces somewhat. But the whole fitting, clamping & gluing extravaganza would have been much more complicated with trying to add that step, and the potential for getting something a bit lumpy would have been annoying. Ah well, can't do anything now, those numerous spaces are glued strongly and now varnished for eternity. Give or take a lifetime or so.
4:11 pm pdt
Thursday, April 29, 2010
1:57 pm pdt
Thursday, April 22, 2010
Tic Tack Toe
High winds and rain limiting finish & fit operations around here, so, thinking ahead a little toward the eventual height on speaker supports-- and what kind of supports or stands will get there.
I've settled on a large pair of front-to-back 2x4s that have a crossmember of a narrower hardwood that intersects them side-to-side. I think I'm at the point with chisels and block-plane that I can actually do a flush mortise joint between the two, where the hardwood actually passes directly thru the upended pine two-by-four. Looking down on the supports, they should look like a "#" shape, more or less. It's becoming clear that a few scans of sketches and diagrams are going to help here; I'll try and get that posted this week.
At any rate, the hardwood (side-to-side) beams will extend beyond the dimensions of the speaker cabs on the sides by a few inches, and be terminated there with tall threaded levelling spikes. After pricing various audio spike hardware, even generic cheap ones aren't very cheap at all. A regular trick to avoid the Audio-Price penalty is to use masonry fasteners from Ramset or other source, which are conveniently point-tipped on one end and threaded on the other... But these aren't quite tall enough to qualify for clearing the almost two inches of hardwood (and extending well beyond that to spike) that they'd have to encompass in my plan.
So in the true S&T spirit, let's make some spikes out of commonly available materials. A good hardware store will have a broad stock of "threaded rod" in many materials and dimensions. Since oxidation wouldn't be a plus here, I decided to look at stainless steel or maybe brass as the bolt portion of the levelling spike. Stainless is an impressive material that works very well, but I've filed stainless bolts before and each one takes hours. In going with the earlier brass-hardware approach on the MG drivers themselves, I think brass will be fine if it's thick enough. It appears that 1/4" brass threaded rod will be strong and rigid enough to position on all four 'outrigger' hardwood footer extensions. Above and below, the rod will be locked in position with brass washers & hexnuts. The resulting spikes will be four inches tall with very small points at the base. Assuming that I can bore squarely perpendicular holes in the hardwood --no guarantee of that-- this simple system should properly anchor and level the "#" shaped rig of 2x4 and hardwood crosspieces, and the speakers themselves. For now, cutting and sharpening tips of brass threaded rod is something of an excercise in watching a limited attention span evaporate every few minutes. But results should be worth it.
1:36 pm pdt
Monday, April 19, 2010
The guiding light and constant reference in this little project has been the thorough and patient voice of Mr. Gilbert A. Briggs, of Rank-Wharfedale Ltd, author of numerous speaker & enclosure guidebooks, and godfather to a million independent hi-fi adventures. Briggs founded Wharfedale in 1932 and his little books make good sense even in the next century. One of the many innovations at Wharfedale under Briggs was the design of double-wall loudspeakers, something related to the project here, but in that case with the internal gaps filled with sand for damping. Here we're opting for broad & blocky gridwork to damp the panels without the weight of something like sand, but the approaches aren't so far apart. Damping materials like soft polymeric foam or felt were considered, but they weren't immediately available so weren't included. Next time.
11:03 pm pdt
Saturday, April 17, 2010
Trying To See The Finish Line
Coming along, veneer ply skin is attaching beautifully to planed grid, glue is being poured with abandon. The most exasperatingly time-consuming part is attaching the pre-finished edge trim, which is taking dog-years to size, sand and fit. I've used a tinted varnish concoction to make it work better with the color of the veneer-ply, but it's taking forever.
Considering a "cookie" treatment for the backs of the cabs. I still have maybe five dozen cut-out cookies from the mass relief work I did on the crates originally. Thinking that perhaps they might be doubled up to extend the cabinets in the back. A double-height cookie torsion box in back would add a counter-balance to the front-forward weight of the drivers, too.
That approach, whether doubled or not, adds an intriguing possibility : what if I perfed the back of the existing box before adding the cookies + new back ? It would add a few liters in internal volume, and wouldn't sacrifice much in the way of structural integrity ...
This will take some tinkering on the drawing pad. For now, it's fitting & gluing sticks for cosmetic trim.
12:39 pm pdt
Monday, April 5, 2010
Poplar slats adhered in grid pattern; the veneer-ply will overlay this to form a semi-torsion-box arrangement. Top sections covered in "cookies" from the mass-relief cut-outs on the inside..... There will be half-inch-square pine edging laid in along all right angles, as borders for the t-box, and as cover for the scrappy woodwork within.
6:13 pm pdt
Sunday, April 4, 2010
Oceans Of Glue, Buckets Of Bordeaux
Using the standard carpenter's yellow woodglue throughout this effort, and using a lot of it. Glue is even cheaper than drywall screws, and I'm lavishing gallons on the now-joined crate constructions; I can't see leaving any joint or braced junction unfilled, and since what we see here will get covered anyway, why not ? I'm not really depending on it for structural strength, but it does close gaps and provide a tough plastic grip on brackets & bracework.
I'm noticing that the glue is much happier taking on a just-planed surface, clean but rough, than any more finished surface. Working now on the exterior walls and attaching slats of Poplar in a grid pattern that will form the substructure for the outer veneer-ply skin. And provide the honeycomb part of the torsion box effect.
Maybe now is a good time --before they vanish forever under the veneer-ply and edging-- to mention that we here at Sound & Torsion recommend St. Emilion and Margaux winecrates due to their classical, "bordeaux-box" dimensions, stout construction and relative uniformity. Emphasis on the relative.
1:05 pm pdt
Sunday, March 28, 2010
Swiss Cheese In A Parallel Universe
Moving along in fits and starts. The winecrates are finally screwed & glued together, never to be cracked open again. I had to remember to add a little doorway in the back panel so as to access the interior side of the driver fixing bolts. Cabinets are now more rigid with this step, as would be expected. There's more 'thud' and less 'boing' when the walls are tapped.
Decided to try a kind of outer-shell reinforcement along the sides and tops of the enclosures, comprised of a spacer / grid material on the outsides of the winecrates and a veneered ply skin. See the discussion of 'torsion box' elsewhere for more on this.
During the various bracing manouevers I cut numerous rounds out of the winecrate wood as Mass Relief. As they collected-- probably over a hundred-- in a shopping bag I wondered what they might be used for. Well, why not as the grid-spacer material between winecrate & veneer-ply. Trying this out is a bit time-consuming, since all the discs of crate-wood in question need to be carefully cleaned up and sanded flat so as to provide a uniform, planar spacer in between materials.
Once the discs are adhered to the exterior of the enclosures and the veneer-ply adhered to the bed of discs --- think opposite-of-Swiss-Cheese -- then square strips of dark-stained trim or beading will cover all edges. Multiple coats of tinted varnish will hopefully draw everything together. This could look reasonably nice or really amateur; the approach is to keep covering previous tracks with acceptably smooth & unobtrusive surfaces. The 'enclosed honeycomb' effect of the lamination should make for lightweight but damped walls that aren't reverberating (as much as any single-wall structure) or storing energy. We will see.
9:35 pm pst
Friday, March 19, 2010
For those keeping track of budget, the only cash outlay so far has gone to some woodscrews, brass fastening bolts for the drivers, and glue, lots & lots of glue. That's it. All materials free, found, or donated by winesellers.
3:10 pm pst
Grille Covers. Need 'em, can't quite decide how to fabricate them. Little word-joke there.
Box Up The Crossovers. Now that we've got halfway reasonable enclosures going, I think it's time to treat the crossovers to little boxes of their own. Just for looks, really, and to add weight so they don't get pushed around. Eventually they'll get sets of binding-posts mounted up, so I can use the real speaker cable; for now the thinnish tannoy stuff is fine.
Capacitors. These (electrolytics, 16uf) would have already been ordered, if they weren't such an impossible-to-find rating. There are fifteens, twenties, and twenty-twos out there by the millions, but not sixteens. Still researching there. Hard to imagine it will end up taking three or four paralleled caps to add up to sixteen.
Lead Shot. Got it, in a storage space, just need to pick it up. For now there is a ten-pound steel weight in the base of each cab. The lead will eat slightly less volume and do the same job.
Spikes. Not yet; for now I've got bars of hardwood along the front and rear, underneath the enclosures, with the front ones on edge for a litte up-tilt, and they seem right for the time being.
Those Treble Controllers. Really ugly but I can't see wiring them out of the system yet, until I've got real cabinets .... or until these get some hardwood outer shells ... They really are useful, though, in getting a feel for what is going on, at least in the treble driver halves of the dual-concentrics. As such they'll be another layer of extraneous electron run-around, that I can't eliminate quite yet. If I were to hard-wire today, though, I think I'd keep Rolloff at flat and Energy one notch to the minus.
Just now listening to Julian Bream's Nocturnal, a moody collection of modern (Britten, Frank Martin, Toru Takemitsu) pieces with the amp switched to triode. At a full five watts per channel ... for small-scale classical guitar suites, no more is necessary, I think.
2:52 pm pst
Wednesday, March 17, 2010
Fork In The Road
Moving along with the wine-crate cabinetry.
I had the idea that now that I've heard what I need to know about basics and functionality, that I might save some labor and just pick up some used speaker cabs locally.... there are no shortage of old American classic cabs roaming around the L.A. area, and finding something in the Jbl or Klipsch vein isn't too difficult. The problem is that most of those, once you get to usable sizes for a 12" MG, look pretty bluntly unpleasant, a little too-reminiscent of giant solidstate amps driving mega-driver arrays playing "Don't Fear The Reaper" or similar. Anything that starts looking a little elegant, remotely stylish-- seems to attract an entirely different market, and pricing approach, which undermines the nickel-&-dime philosophy here, as well as the budget. So for now, gleaming walnut vintage enclosures are out, winecrate modification is back in, in a big way.
To which end I've added thicker front baffle panels, comprised of nice 3/4" ply that I'd tucked away years ago, and a top layer of 3/16" hdf .. because the sheets of hdf were a find. So a layered baffle, easily the most rigid thing about the whole construction thus far. It's fairly certain that the crate/ply/hdf laminate --unglued for now and reversible- will be a less-resonant launching-board for sound, and I'm hoping the fairly-dead hdf surface keeps out any tendency to 'beam'. We'll see.
I'm putting all that back together, maybe adding a brace here or there internally, and looking forward to another listen. Having the tannoys on really rigid baffle support should be completely different, if nothing else, to having them installed in the forward-facing base panels of the crates by themselves in the 'make-shift' version. For now, here's a photo of the interior.....
9:40 am pst
Tuesday, March 9, 2010
The Substance Is There
Reminds me a bit, in casual listening, of the classic old three-way Spendors I lived with in an East Village sublet of 1985 or so. Just the weight, the timbral accuacy and the effortlessness...
The substance is there, the foundation, and no problem at all, so one can only imagine the eventual refinements.....
10:31 pm pst
When you get your hands on the MGs it's worth taking every precaution to preserve that paper flared-cone no matter what else you do. So while smashing up wine crates, for example, it's sensible to have the drivers away from the melee, preferably on a high shelf somewhere, face down & protected. My first chore was to get some mounting hardware, so on the idea that brass would be less hardened and non-magnetic, I found some 10/24 brass inch-long bolts that would suit the job; while having a later look at the backs of the drivers, I found that Tannoy themselves had used brass hardware, so a good omen.
Two other chores were electrical : after the first evening of "trying not to change anything at first", I felt that there was some connection dirt in the system somewhere. So first, a session with spray contact cleaner on the four-pin plugs, and a caution on the same process for the jack. The four-pin jack on the speaker chassis is completely open in the back to the paper cone-- so by all means slip something protective like soft paper or cloth behind the jack before having at it with the contact cleaner. No reason to think that contact-cleaning agent sprinkled on the back of the speaker cones would be a positive thing, so watch out for the internal wires, and slide a soft shield back there while you whisk away at the conductors of the jack. Make no mistake, though, signal transfer benefits from contact-cleaning forty-year old sliding connector parts.
The other electrical chore was that terminal strip at the amplifier end of the crossover cabling. Did I really need to be connecting my speaker cable to the terminal strip, so that in turn it could then connect to the Tannoy speaker cable entering the crossover ? No, my amp is within three feet of each speaker, and with crossovers laid out, the Tannoy cabling makes it easily. So unsolder the terminal strip, keep additional speaker cable coiled up elsewhere. A few less connections and cable lengths, here at the beginning of understanding the crossover, energy and rolloff controls -- removes a bit of unwanted haze. Simple, reversible.
Also, not sure that one wants to ultimately enshrine Tannoy's thin seventies speaker-wire itself in any finalized Monitor Gold setup, but it's a captive fitting for the moment, so it's taking the place of any more audiophile cabling for now.
My makeshift crate-cabs are getting more and more solid by the day, with new braces and crosspieces added, suitably mass-relieved, nearly every day. I imagine that the MakeShifts will have subsumed about eight or nine wine-crates by the time they are retired, which may be soon. They are constructed of about 2.6 crates each, and the remaining crate materials have gone to bracing. Photos forthcoming.
11:13 am pst
Saturday, March 6, 2010
Arrived : Two Reasonably Well-Behaved Rabbits
Arrived thursday, and there has been wine-crate sawdust, debris and splintered boxwood all over for days now. Just needed something to check that the Monitor Golds are operating, so, quickie boxes comprised of about 69 liters worth of volume, inadequate even by minimum standards. But enough to check that there aren't gremlins lurking around the rabbit hutch.
We have signal, and both elements of dual concentricity are feeling it.
Whoo, bass, too.
6:07 pm pst
Sunday, February 28, 2010
Top Hat, Drum Roll ... Rabbit ?
Got them. I think. Paper-accordion surround Golds. Shipping tomorrow.
Delivery this week.
A year and a half in the planning; we'll see what persistence amounts to in the face of the luck of the draw. Rabbit's feet out & ready for action.
8:36 pm pst
Monday, February 22, 2010
Before The Flood
This little journal starts before I've got my hands on the pair of Tannoys I'm buying over the internet. Thus far it is narrowed down to the area of 12-inch Monitor Reds, the expensive classics, or Monitor Golds with paper-accordion surround, the runner-up. The attractively compact 10-inch IIILz type I've ruled out on the basis that they're reported to be a shade less-rich than the 12-inch, though pacey & accurate; the fifteen-inch ones aren't matched to the small to medium space they're likely to end up occupying in the next decade or so.
And so as the search comes down to the final hours the pressure is on to design cabinets that will serve as competent first-efforts, something to give a minimum idea of what the very-expensive drivers can do. And yes, it involves wine-crates, the most minimal box that will suit the requirements. With modifications, of course.
2:47 pm pst
Friday, February 19, 2010
No more the puppet of the malevolent audio manufacturers.
This idea came to light over about a year and a half of guesswork & perplexity.
Simply put, really spectacular drivers, in boxes of increasing sophistication.
Starting, modestly enough, with wine crates as building blocks.
2:31 pm pst
© James Donahue 2011
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Tannoy loudspeaker project
Music, twentieth century analog audio, and
An amateur exploration of the mysteries
of signal and noise,
all on a nickel & dime budget.