A Tannoy 15'' Enclosure for the Enthusiast – The Realisation IV

Today I will report about my second week living with the new enclosure type. Living means on the first hand to get acquainted with them and on the other hand to optimize their performance in a lot of little details to improve their ability to perform like a natural music instrument. As already described, the first listening ended with a unforeseen disaster. With the strengthening and tightening of the construction (i.e. the backboard of the funnel/baffly board) a unbelievable deep, crisp, creaky and colorful low frequency response came up. This sort of response I never have heard before with a Tannoy Dual Concentric speaker, it was just breathtaking. The open baffle type cabinet with its fast, dry and extremely undistorted low frequencies made this lf-response a sensation.
But to be honest, like always, when a particular property shows up with a foremost character and over boarding quality, it happens always at the expense of others, in particular with a full range speakers. In my new cabinets the response of the highest frequencies has got influenced very well from the stiffened mounting. The easy natural listenability had suffered, the character of the speakers has now grown very prominent and superficial. This is never a good sign…

The baffle board and the mechanical attachment of the speakers seem to be are a very delicate part of the most designs, it was with all my former cabinets, but here with the support of the horn its influence is tremendous. Sometimes I do ask me, if commercial made speakers (like Altecs, Jensens, Tannoys, JBLs, etc.), ever have been evaluated so critical about all this little details before they got introduced into the market. I really can't believe this, if their designers will have taken this important detail into study? If, there would be other alternatives in mounting big chassis to the baffle boards? With solid full range types or other sorts of duplex speakers a wide range of different sound attitudes can be achieved, just with more or less solid consolidation to the baffle boards (i.e. one built chassis with a covered frequency spectrum from 50 to 10000 hz minimum).
Since I did use the front loaded horn, in particular with DHT preamplification, I have got used to a perfect transparent high frequency response without any hardening or any other sort of degradation. With its wide open, deep and spacious projection, its extremely transparent properties the funnels did engage my main ability to preserve them into my new design. But now, with the new stiffed cabinet, some of this silky response has got lost towards a more technical performance, as well grown to a bit cheeky side. I cannot accept to loose my beloved and very important attributes, so I started a venue to find this refinements back. Such enterprises are always a part of the similar game, independent if the trip will enter electronic wonderlands or like here, the relationships of mechanical resonances between design and built materials. My aim is to shift the existing resonances in the radiated frequency spectrum up and down, to emphazise were these can be damped, were they are mostly annoying and finally might support the general performance.

Stiffening of the back board, as well can be seen the tight mounting of the chassis with metal screws

As a first test I exchanged the stiffening board against solid underpinning struts, in each cabinet two of them did resemble the massive boards. The effect was as expected, the wonderful creaky deep bass was gone and a bit more wooly and soft indifferent low frequency response had taken place, together with almost no change of the hf-response. The all around performance of the cabinets was immediately shifted two classes below their former state. It took not very long and I reassembled back to the solid construction already shown in my last post with the solid boards.
As next step I did dedicate my interest to the mounting of the chassis. In almost any vintage cabinet the mounting between wooden baffle and speaker is realized with double threaded nuts, which are inserted into the baffle board and take the bolts to fasten the speakers. As already said, I always find this construction a very delicate operation, in particular with full frequency radiating chassis. It is going extreme and more than delicate to mount such a 15kg chassis to a baffle board. First the simple way of a thin walled baffle, where the chassis is mounted with short wood screws. This simple way can work quite well with sealed or reflex enclosure types of smaller size. Second the way of double layered multiplex boards with 24mm thickness to form the baffle (like the 1970 diy schematics published by Tannoy) is a very difficult approach to harmonies in the response. Since the strengthened boards are always shifting the performance into a more or less edged sound with harsh ends. Additionally the chassis are fixed with inlaying nuts and solid screws tightened till the wrench brakes.
Between these two designs almost any degree of prominent resonances is possible, just the way their  physical ability to handle them will change the general property to work like a instrument.

A selection of different mounting materials, screws, bolts, nuts and wooden clamps types evaluated with this cabinets.

The older speakers from the Tannoy range even strengthen further with eight wholes instead of four. In short the massive tight construction gives way for a more technical orientated soundstage, since the opposite design opens the way for a mild more natural tonality with refined harmonies, always at the dangerous border to indifferent detail. Almost any state in-between these two positions can be achieved, depending on the character of the amplifying electronics.
In all my former evaluations with speaker cabinets I ended up with a less tight, more natural relaxed attitude of well balanced long listenability. Here now with the funnel I wanted to go a similar way, but have to find new options to realize the first path, since the funnel makes it more complicated.
My next idea was to design wooden holders which will resemble the nuts in the baffle board. For that reason I made some wooden clamps, which will press the speaker from the back side to the funnel (i.e. baffle board). This construction will have the option to adjust the tightening power precisely and distribute it by a wooden lever to the chassis. The wooden design makes a much refined transition point between speaker resonances and cabinet possible. Were the classic bolts are more or less tight or not, here a wider variation of tightness and as result of the wooden material, a improved distribution of the introduced resonances will be obtainable.

Specially designed wooden clamps to improve and control the pressure and therefore the resonance introduction coming from the chassis into the baffle.

With the clamps installed the general sound relaxes a lot, the medium frequencies get back into a perfectly refined performance and as well the hf-response improves remarkably. "…at the cost of other properties…", I did say. Yes, the lf-response suffered here, it lost precision, got wooly and overloaded in power. For the first sight it was acceptable, but I did realize immediately, it needed another idea to get all the resonances better distributed, but I had no idea yet were to search. With the building of the clamps, I did already feel like a classic instrument maker, since such introductions are "everyday bread" in this job. It looks, that it is all is a play of tightening and less tightening; to get both directions of energy into the right balance of control with contradictive effects.

I did improve the design of the clamps with the second made generation so, that they will be able to have a better distribution of energy. I did introduce the wooden dowels in order to bring the pressing right into the mounting holes of the chassis. I fixed the clamps whis double wood screws to the baffle board. With the effect, that the all around performance improved the right way, but still the named problems stayed in reduced stage. So it needed another try to get the cabinets forward to sing.
I came back to my originally used bolts and nuts. I bought rubber washers of 2mm thickness and introduces these to decouple the metal bolts from the chassis. Now everything turned back, the lf-response got bettered with fastness and tightness, the medium frequencies rounded up, but the hf-response was again a bit to prominent. Now I had the opportunity to adjust the power of tightening by turning the screws a half turn forward or back. No way, no position got out a acceptable performance, it always sounded prominent and shrill.

The perfect sounding solution, the simple and technically poor mounting with felt damped wood screws

So I made a very easy try. I did cut out washers from my 12mm felt. These got combined with iron washers and simple wood drilling screws. This sandwich got screwed tight till the felt compressed into the holes, there were four empty ones with each chassis. So I only had to remove the other bolts with rubber washers and could listen directly to the new mounting principle.

Unbelievable, a fundamental change came up. A completely improved performance of all frequencies was immediate, with a fast and airy, well extended lf-response, all other frequencies improved to a so far unknown state. A three dimensional holographic performance was suddenly present with best dynamics and a perfect sensitivity, without any particular prominence. Just homogenous refined musicality containing a wide scale of harmonies and without any offensive touch. I did listen to a lot of my analogue records this evening, as well I did stream digitally stored material from the hard drive. I did both with a good loudness (always a good sign) and completely pleasured with my new speakers. Now I need to be prevented from myself, not to change this "winning team" again. Even, when I do know that this mounting is technically a less educated solution…

The lesson from this new experience is, to take more than care about this constructive detail, if you are building a cabinet for full range speakers, in particular in the heavy weight class. The mounting of the speaker to the baffle has the same importance the materials for the enclosures itself have, as well the speaker type and finally the principle of enclosure are on par. If a felted washer can make such a difference, – a difference which in the hifi business sometimes will be paid with 1000 or more dollars (for one interconnection for example), than almost any speaker enclosure can be adjusted or improved in a fundamental state, when taking care about this detail.

If you are interested about more results from our music instrument research department read on soon,Volker

A Tannoy 15'' Enclosure for the Enthusiast – The Realisation III

                  

                  "Never change a winning team!"

Hi to everybody interested to follow on. Today I am writing from the position of complete frustration about the first audible results. Before I was absolutely save about my knowledge and new ideas which lead to the realizing of my new enclosures. As I already said, I have realized in the past several other enclosure projects for two decades, so I was absolutely safe about the most constructive details evolving with loudspeaker cabinet making. I did not expect to end my first listening evaluation last week with a complete disaster, the new enclosures did not work at all! These cabinets were not able to show any low frequency response at all. I had the impression below 300 hz all tonality has lost any lower support, below 100 hz it seemed to be like cut off. It sounded like with a low frequency control knob in contradictive position. The former evaluation cases performed very well in this discipline, otherwise I never would have been convinced to overtake the open baffle principle for the new enclosures. One more time it can be said: "never change a winning team…!"It was again one of the moments in life were I was absolutely stroked back from a unexpected effect…!

The new enclosure

For more than a half of a year I did use my former evaluation enclosures to work out almost any option for the final design. How can it be, that the perfectly made new cabinets didn't work almost in a similar way, when all constructive detail have been tested before with the dummies? All? I made some basic new experiences during the evaluation, first time in my life I did use a 15'' Tannoy Dual Concentric speaker in a open baffle cabinet. As the attentive might remember, my first impression was as well a  bit thin sound structure, which I needed to accommodate, when coming from a former reflex cabinet with big boost in the 100 hz area. After a while I learned to assess the faster, leaner and undistorted bass response of the open baffle to be superior to any other principle I had used with 15'' Tannoy speakers. With a good horn or in the open baffle the bass response can reach almost natural accuracy and timing, were other principles mostly suffer from a wooly and always slow thick bellied lf-extension, typical for ported designs. A lot of people do prefer this unnatural sound and get confused meaning the attribute of "warmth" and "rounded".

During evaluation I tested the mechanic extending of the cabinets in order to improve the lf-response with longing boards. These thin boards had been screwed to the back frame. This sort of simplest extension showed me the effect how such a extension will influence the lower frequency response. As a result I decided to built a extendable cabinet. Second I had already evaluated the front loaded horn with other cabinets and did know about its big advantage. So I have realized two wooden funnels and just screwed these in front of my evaluation cabinets. In the past I did learn to fear massive thick double walled baffle boards, they will not work well with a fullrange speaker of the heavy weight class of the Tannoy. The middle frequency response get hardened and does not sound very refined and musical. But here now the double baffle did do quite well, even when the evaluating design was almost 40mm of plywood with both layers in sandwich. I did not know why? The drivers had been mounted very tight from behind the original baffle boards, which were a solid part of the open box type construction, the funnels just added up as a additional front part.

The evaluation enclosure with double baffle boards

The implementation of this horn funnels into the  final enclosures made several changes in the construction of their mounting necessary in respect to the free sides for the sliding inside cases. At the end I did use a mitered frame design to incorporate the funnel into the housing. The completed object got screwed from the back using the strengthening frames at the front. The heavy driver is mounted directly to the end board of the funnel. Only the funnel itself supports the 10 kg of the driver and conducts as well its energy input to the whole system (resonances). My former experiences with Tannoy drivers have always made the baffle board construction, its material choice and its dimension to a delicate decision in order to find the best resonant voice for the full tonal spectrum.

Special constuction to keep the space free for the sliding cases

For two days I tried almost everything possible to make a change. I did seal the speaker to the funnel with mod rubber stripes. I did seal the interior cases with felt lips to the main frame, both in order to prevent any early unwanted shortcut of the lowest radiated waves. I did check my electronics for any defects, particular in the regulation of several power supplies (In the past a defective regulator tube did drive me crazy by its compromising sound). I did check tubes and tried very different first changes with the enclosures itself. The slideable interior frames did not show any positive effect at all (how could they do without lf-response). So I just made a quick reflex conversion, I did close and seal them and I did fill them with wool. All changes showed the same result, no low frequency response! I did run desperate not knowing what to do.

Normally driving a car for some hours is the perfect situation for me to let my brain play and find the clearest thoughts. Since I did not have any traveling at my timetable at the moment, I had to find other states of concentration. Waking up early in the morning and lying in bed is another excellent option to find deeper ideas. Here I realized some days ago, that the mechanical support of the driver, i.e. funnel might bring the problem. I did know from former realizations that the strong stiffening of an enclosure is a absolute basic to get good tight bass response. If you bring the conjuncted construction even further under tension (like instruments are made), it can even improve in this competence.
So I did know that the sliding mechanism does prevent any rigid inside constructions since its needs to keep all four side walls free of space. I decided to take the inner enclosures out and instead to introduce  massive panels to connect the holding backboard of the funnel to all sides of the cabinet. Additionally  to the precisely adjusted boards I did use wooden cotters to bring the whole construction into controlled tension and used some more massive screws to hold the boards into tight position. The revised construction has tightened up the whole design with a main attention to avoid the suspending effect of the funnel to the driver mounting. The classic knocking test with the finger at the outer case showed immediately a completely different resonant ability.

Wooden cotters bring the interconnected boards with the outer frame into controlled tension

Stiffening board underneath the backboard of the funnel

Two hours later I started again to listen to this enclosures. I remember the first moment last week. I just placed the diamond in the first groove and even without any music I did directly realize, that there was something going wrong. But now the inlet groove test sounded promising. From the first moment everything was better than right. The sound was completely different now. The tonal spectrum was very well supported with perfect balanced lower frequencies and all other frequencies seemed so much better integrated, that from the first moment on pure relaxing was on set. The lower frequencies have got fast, tight and deep, with a wonderful creaky ability to reproduce the best wooden instruments from the "Cremona School". Some records of Benjamin Britten with Rostropovich at his cello, Jaqueline du Pré and Pablo Casals made me immediately to find home in the absolute "gourmet class" of music reproduction.

But as well brass instruments did profit a lot from the improved integrity of the low frequencies. My absolutely favorite record of modal jazz music "Kind of blue" is always a very good test. A highly improved soundstage without any compression, but with extra space and air as a result of the front loading mechanism. I was sitting in front of my new speakers and more than happy with the result. Now they did match my highest expectations and they are performing even better now. They are the best Tannoy speakers I have heard till now – by far, no exception.
They have the ability to perform in the best possible manner being a true natural music instrument with well balanced harmonies as foremost attitude. They can work free of the usual compression effects and typical electrical artifacts with a wide open soundstage of almost holographic depth. Even after four hours of intensive listening no signs of tiring occurs, which is always a result of well balanced homogenous refinement. The speaker is able to produce exceptional fine micro dynamics, which is a more common character of electrostatic speaker designs, than with heavy weight champions of the paper cone class. The dynamic abilities of such drivers form the attraction to use a 15'' speaker, the combination with the refined abilities give such combinations a highly addictive dimension.

Only a handful other systems are in competition with such elaborated audio transducers. But this question is a purely theoretical one, who is able to make a direct comparison between let's say a JBL-Paragon, -Hartsfield, -Everest to Jensen Imperials, to EV-Partricians, or to Tannoy Westminsters, to  Altec's A7, to Western Electric WE15a's with WE TA7331a's or to a Klangfilm Euronor?  Nobody (I know, Dr. Takeshi Mikami, he has them all) is able to do such a comparison and I do think it is as well not necessary. It is much more on demand for the most of us, to find a good match for the own preferences and our personal taste. Mine was and is the Tannoy Dual Concentric speaker and I have realized now a longtime captured idea, to design a very good set of audio enclosures to bring them in the foremost line.

Some horn funnels on delivery in Japan

Other people would do now a recording/movie with an iphone and upload it to youtube to show the properties of the new speakers. I have never understand for what reason this little films about high end equipment are made, may be I am to old to understand?
But right now, it needs to improve the craftsmanship of the new changes in the enclosures as next step, before the last function will be implemented, the variable blinds as back of the baffle. We will see, if other unexpected things will happen?

Read on soon, Volker

A Tannoy 15'' Enclosure for the Enthusiast – The Realisation II

Hello to everybody interested to follow on my realisation designing new enclosures for the classic Tannoy Dual Concentric speakers. In short summarized the first part, I want to find a living room friendly size for the 15'' Tannoy speakers which will be a incomparable upgrade for the common aficionado not having a restored farmhouse in Cornwall for the second or third hifi setup.

"James Bond" like phantasies of Tannoy sales managers in a product catalogue, were the woman, the whiskey, the furniture, the car and the audio components will match the same decorative "taste" of empty chauvinistic representation.  Imagine a car outside? But there are definitely 200 better choices of malt whiskey in Scotland...

As ended in the last article my first listening to a Western Electric horn array extended completely my idea of audio representation to a new dimension. Their unfolded horn designs (foremost made to transduce the middle to high frequencies of the audio spectrum from 300 to 12000 hz) showed me a unknown dynamic spread scale of musical informations, –  its inherent captured air, speed and a true naturalism of representation.

A winter tale...

This particular experience brought me back to my long lived dream about a front loaded horn funnel as an improvement of the classic Tannoy speaker, knowing that such a feature will help the Tannoy a lot to overcome its typical "archilles' heel".  In the mid 1990ties I was interested to introduce it to a common sized cabinet and discarded the plan because of complications in the technical realization (bending wood). In theory I was always convinced that the funnel will open up the important medium frequencies with a widely improved response and now I wanted to practice this idea. I built a first pair in 2010 from card board and introduced them to my cabinets  –  I could not believe what acoustically happened even with a such simple design. I directly realized, that I had failed a absolute important feature for almost 20 years of use. In original it got introduced with the Autograph cabinet to bring the middle and high frequencies to the same level as the mechanical amplified low frequencies from the backloaded horn. As I now know myself, with the Autograph cabinet it is very difficult to find a almost invisible natural audio representation. The size and materials of the cabinets, so the position in the room corners make them…,  let's say, to prominent transducers, were the holographic presentation in the middle frequencies is not the foremost quality.

The new enclosure

In other applications the front loading horn can help very well to overcome Tannoys most problematic attribute, the frequency cut around the 1000 hz, where Tannoy married the low and the high frequency diaphragms. The 1000 hz point is the most problematic area in the whole audio spectrum. Almost every instrument and voice covers this part of the frequency, which means, in the audible reproduction any mistake will be shown with a tremendous general effect. With the support of the funnel the Tannoy "achilles' heel" gets highly improved. I would go as far to say, it completes the speakers to a new design, when the modified crossover will support that task.

and 2/3 out...

The interior cabinet almost complete in

The interior cabinet is sealed with a felt lip for tight and smooth extraction

The distribution of the medium frequencies are in a different class and remind me a lot to the qualities I did notice first time from a big Western Electric medium frequency horn. As well here now a dramatical improvement in the coherence of the middle frequency response is noticeable. A lot more air between every instrument is present as a result of mechanical improved high frequency dispersion. Together with much better transient response and a dramatically bettered homogeneity, the most significant benefits are shortlisted. The vintage Tannoy Monitor speakers are already known and valued for their homogenous refined sound quality as a single point source (mostly in Japan, to me it looks that more vintage Tannoy speakers are in use there, than ever been produced in the West Norwood factory). Being a 15'' driver of enormous dynamic abilities, it combines two almost contradictive properties hardly found with other drivers. With the customized front loaded horn it reaches new claims of extended natural musicality and tonal refinement.

But one thing needs to be said at this point about the amplifying electronics to be used with such a horn to everybody who is on a hunt for a cheap shortcut to the wonderlands of life. It needs the finest tube amplification at every stage of the chain, able to deliver the best refined musical signal without any sort of phase degradation or other typical electronic deformation in the response. When such improved signal quality will be obtainable, a front loaded horn can be a fortune (similarity with the huge WE horns). 

With some mediocre shop hifi products or even worse some chinese "bling bling tube amps" such a audio transducer of this ability will show straight the inherent limitations of the poor profit orientated designs and their inferior used parts like seen with a magnification glass. It needs a perfectly matched chain of single components built from well chosen parts to a higher order of quality. The necessary refinements will rarely be found in commercial made hifi components due to its limitations of cost cutting values and sale strategies. With highest grade parts built diy projects might be able to realize a different stage, even when the budget will limit the plans. Or similar concepts are consequently made and matched together by idealists like Shindo, Kondo, AN and some others. With superior DHT amplification today such a quality is realized like no other by Thomas Mayer.

The advantage of the open baffle principle for the cabinets combines the perfect conditions for a driver in a horn design (the decrease of the braking air cushion behind the diaphragm and therefor the increase in linearity and speed of its radiant ability) of a comprehensible sized cabinet. As well the open baffle adds the backward radiated energy to the common front radiation (in anti phase mode), which can be  noticeable as increase of the low frequency radiated energy. Here the position of the cabinets and the size of the surrounding room gets into account, since the lowest radiated frequency will be limited by the room itself and the total length of the from front rim of the lf-driver to the back rim.
A typical open baffle speaker radiates into both directions, which means that a fullrange driver radiates the same energy into both directions. The backward part will be reflected quite soon from the backing walls of the room. The distance between speaker and backing wall defines the time delay between both contra phasing signals. If they would reach the listener in time, a whole part of the audio spectrum will  distinguish itself. So its is quite important to find a ideal position for the speaker between wall and listening position in a given room. Generally it can be said that a position in the center of a room will give the best undistorted (longest delay of reflexions) radiation. But the most people don't want to sit in the middle of a room with the huge speakers 1.5 m distance in front of their face. Here a compromizing position has to be evaluated. I have my speakers positioned with 1 m distance from the back walls and sit with three meters distance in front of their 3 meter base.

With 1 m behind it starts that the backside signal adds with a positive effect and enough delay comparing to the frontside radiation. The funnel directs the front radiation to the listener, so the typical negative effect of all fullrange baffle speakers, namely a decrease of space illusion in the soundstage by wandering reflections is not audible. The reflections in the room normally decrease the precise definition of the stage, thanks to the physical benefits of the funnel the illusion of space is extremely good. At this point all goodies come together. The unique Tannoy Dual Concentric principle works acoustically like a precisely defined point source for both frequency units. The funnel completes this design to a wider overlapping of both parts, operating the enclosure similar like a full range instrument of defined position. As result the speakers are able to produce a perfect illusion of space (like a lot of small drivers are known for this habit), a holographic dimension were other duplex designs of this weight class are showing limitations and produce some problems (phase and time delays between their units) to be corrected. Ask the most people driving a huge WE installation about time delay (some of them can write books about these facts), you will be astonished how much technic will be needed to get it  corrected. A integration of a analogue to digital conversion, digital time delay shift, followed by a digital to analogue converter before power amplification, is one of the simple operations to get it corrected. This is one reason, which protects me against such highly complicated systems, even if they are massive virulent sound wise.

Read on soon about the variable options with the inner cabinets, Volker


footnote: the image from the Tannoy product catalogue is shown with respect to the original intended use

A Tannoy 15'' Enclosure for the Enthusiast – The Realisation I

I hope everybody has had a good start into the new year. As a perfect beginning I am very happy to present my new design of enclosures for the Tannoy 15'' Dual Concentric Monitor speakers to all interested enthusiasts. My cabinet is made in foremost stage to match my personal high expectations as an musical instrument on its own, but as well to match the universal preference list of the common Tannoy aficionado. For those were the size as room dominating furniture will not be a foremost feature, the Westminster might be the perfect match, plans to built them are existing in the web. But when size does matter, it needs a more compact designed cabinet as to be a ideal typic replacement for the classic 120-200 liter volume bass reflex cabinets (Berkley / Arden / Lancaster / Canterbury / Amesbury / York Rt and similar types like the Onkens / EV, etc.).

Guy R. Fountain at his wood workshop assembling a Canterbury corner cabinet made from lumber core plywood. A excellent material for loudspeaker enclosures, but only seen with the most manufacturers till the early 1960ties.

I wanted to find a fairly improved cabinet design, which works in every respect superior to all the vintage designs and will be able to embed the Tannoy speaker as incomparable audio transducer. My found solution combines the open baffle principle with a sealed enclosure type, additionally a possible variable extension of its volume will give extra options of adjustments. This variable extension adapts a wide range of room preferences and customizes the best low frequency response in a given room. With its selected materials several improvements and refinements in almost all acoustical terms are audible. A more natural response is a result of the extensive use of solid coniferous wood sorts and traditional wooden connections instead of screws. The whole audio spectrum is a lot better defined with finer harmonic structures and improved tonal ability as result. Quite thin walled boards of northern plywood (15mm) are used throughout the whole design (instead of thick walled boards), instead plenty of solid strutting has been applied in combination to natural woolen felt in order to control interior reflections and resonant damping. The strutting overtakes experiences from Western Electric baffle designs to structure the boards into unregulary units in order prevent resonant additions arising. The verneer is a long fibered solid 3 mm thick mahagony wood type to add another solid wood layer. The common use of finer layered multiplex boards with loads of compound glue should be avoided, the thicker layers of the plywood have a enormous advantage in natural tonal harmony of the finished speaker.

 

Strutting with solid wood to structure the panels into unregular sized parts, damped with woolen felt of 13mm thickness to prevent unwanted reflections.

 Sliding mechanism for the internal cabinets made from damping boards to extract the absolute distance between front and backside rim of the speaker.

This particular cabinet design summarizes my experience of 25 years of building enclosures for Tannoy speakers to a certain stage of improvement. I have built sealed, ported, vented designs of almost every useful size from lots of different wooden materials, as I did built different types and sizes of horn enclosures. Every design has had its own special physical advantage, but in almost every case at the expense of other qualities in its ability to support musical harmonies of certain orders. Over the years I have met lots of other users with Tannoy speakers, where I could complete my knowledge about unknown types.

As described already, I never could accommodate one of the classic backloaded horn designs (i.e. York, GRF, Autograph, etc.) for myself, because I don't like the always present uneven frequency (roughness) below 500 hz, arising from the not ideally formed backloaded horns. The shortening of the development, the reflections inside (turning corners), the unavoidable resonances of the huge enclosure surfaces and their much to small openings, support this effect in a amplified manner. It is always more or less effective, independent if we talk about the small GRF Rt or the biggest design the Autograph, – all these designs have a collective presence with expressive dynamics, but they are far the opposite from being a holographic transducer. The only original design I never had a chance to listen to, is the Westminster Royal. But as well here the enclosure offers infinitive foldings with huge surfaces inside, with a quite long horn development, but still far away from a ideal design. Some version have as well the "Girdacoustic" strengthened cone which is a lot to heavy, but is able to dissipate 100 watts of power. Here the given name states the foremost claim of the venture: "prestige series".

To make them sing a lot of traditional wood work is necessary...

The crossover housing needs to be placed out of direct radiation from the speaker

Loose assembling of some parts of the internal enclosure.

I was convinced for all the years that the vintage 15 ohm Dual Concentic Tannoy driver is one of the best speaker designs of all time to be used with tube amplification and in a horn design enclosure. I have tried out several other duplex options from Altec, Vitavox, Stephens, Lorenz, Jensen and others without getting really involved. All the speakers I did try, have enormous potentials when well implemented, but did not attract me to be some sort of a lifetime companion. The Tannoy shows some extra qualities all the others don't match, as a result of its unique seamless integration if the hf-unit. As one of the foremost vintage enclosures I do like the Altec Voice of the Theatre A7, but unfortunatly it does not perfectly match the Tannoy preferences. Generally it can be said, all speaker designs haves beside their qualities as well some sort of disadvantages. When we decide, we are always looking to find the best compromise to our individual preferences and to our taste. Mine was and is the classic Tannoy.
My all time statement  –  till I had the chance to listen to a Western Electric horn array with refined tube equipment. This performance was absolutely unique, a completely different physical presentation of audio acoustics, which I had not heard before, impossible to be realized with a dual concentric speaker. The wide band medium frequency performed by one single driver unit (WE 555 with WE 15a horn, i.e. transmitted frequency from 100 to 4000 hz, with WE20 horn from 300 to 8000 hz), amplified through one ideal long horn development without compromise, is a audible class of its own, a true majestic musical instrument of highest ability.

WE 15a replica Mf-horn front ends in delivery in Japan. It just needs a tiny bit of a good will and such a installation will match almost any living room. Thanks god that the necessary additional Lf-speaker is not a horn design...?!

These wide range operated horn systems are exceptional designs in a true class of their own. The WE transducer systems have been designed for cinema installations with a ultimate possible quality in mind, in a time when the later cost cutting preferences were still out of sight, which got standard in almost every case of all modern mass production in the second half of the 20th century. I will cover a complete series of articles about these speaker designs and its modern derivates made by Line Magnetics in practise for early spring time.

Read on next week for the finishing of the cabinets, Volker