reading on here. Today I want to describe a revisit to my favorite audio set. In a former series of articles I did describe Mikes setup as a typical LineMagentic/Western Electric installation with 22a-horn, 555-telephone, 597 hf-unit in combination with a h-dipole enclosure (with compliments to the original WE TA-7331) incorporating Klangfilm KL-405 low frequency-speakers (Incredible close to Music I – The System Matching).
This particular shown audio installation has set the pace for years in several audible terms for me. One rarely found effect was the general ability to play any sort of program material without any inherent preference. Typically the mass of better audio sets shows mostly such preferences, i.e. like intimate small scaled classical or jazz music, or large scaled orchestra and opera music or as third option, a clear distinction into electrical amplified rock or pop music. Mikes set was frankly said immune to any sort of compensation its inherent sound destinction. It always made me speechless when he played large orchestral music and switched to a pop band like Yellow, both played with almost 100db loudness without any sort of compression or other typical widely known errors...
For years Mike tried to improve a little here and there, some minimal changes did happen, but in general he seemed to follow a deep insight, made with this combination of components after 30 years of testing and changing. This particular combination marks a solely found apex, where everything seem to match perfect in balance and maximizes in colaboration to each other in a certain degree of quality. I always reminded him saying:"Never change a winning team"! To often we all had bitterly learned the lesson, when in order to improve the things, we change only one component and had lost it all – audio mikado!
I did know since two years that he was interested to test the original design of the low frequency dipole from Western Electric made in the early 1930ties with TA-7331. He always said: "I want to know how it really does sound". The attentive reader might know that in the early 1930 years in cinemas the sound was more or less telephone quality, maybe a good 200 to 5000 hz aka voice standard, far from todays audio quality, where everybody demands a minimum utopia of 20 to 20.000 hz as a result of 60 years of commercial advertizing promize.
Mikes lf-derivate dipole is a good portion smaller than its role model, made to match the sizes and preferences of the 22a-horn asthetically and made from different woods and is with best arguments a good lot less stiffer realized. The original WE-drawings are available and give perfect insight into construction, material, sizes and dimensions of the vintage enclosure. So Mike tried to copy a perfect close sample of this product. Northem hemisphere coniferous woods are today in Europe not so easy to find, but he did. He tried to copy the original design as close as possible and with some help of his friend Norbert Gütte he matched with unbelievable acurateness the historic role model into a today made reality.
|inside different cut out adapter boards can be mounted|
With his long term established installation he did incorporate a pair of 14''-drivers in dipole constellation in order to find enough low frequency energy for his set, till he uses just one simple 300B-SE-amplifier to drive the whole installtion in a passive way per channel. After testing several other 15'' driver options from Altec and Isophon in the past he did finalize with two KL-405 some years ago.
His beloved one and only power amplifier Shindo SE-300b mono amplifier drives his three way installation alone. Other fellow warriors incorporate active tube or other amps dviding for the higher frequencies in order to find enough control for the low freqency part. The Shindo amp is a true WE91A derivate, so it does convince with phantastic medium frequency tone realism and a rare fluedity as a result of a quite small Triad output transformer. The other side of this medal is a less prominent bass response, not exceptional loud nor far deep, comparing these rarities to other 300B-amps. In order to compensate this effect Mike did use the two Klangfilm 8 ohms units in parallel to find the right energy level as low frequency support without compromizing the higher frequencies using autoformers. This combination gave him unparalleled service for years.
With the new, stiffer and bigger TA-7331A dipole enclosure Mike is well prepared for examination of different driver options with matching adapter boards. Since years he has held a pair of LineMagnetic BA-15 field coil 15'' drivers in storage, which now get another chance to come into service. Independend from this pair he tried first to match only one of the 14'' Klangfilm KL-405 with than 8 ohm impedance, mounted to a adapter board into the new enclosure. A vintage Jensen or a replica 18'' fc-driver with lightweight cone and 16 ohm impedance might be actualy still on his wish list. The search for other drivers is hardly limited to paper rolled surrounds and extremely thin paper cones with ultimate cone mass of 120 grams for the 18'' versions and of course even less for the smaller variants. Such determination is result of long term evaluation with low powered single ended tube amplifier devices .A well known classic in the 15'' range is the TA-4151A or its bigger 18'' TA-4181A LineMagnetic brother will be classic aproved partners of this type of enclosure.
The evaluationFirst of all it was very interesting to listen for me to only one of his classic Klangfilm drivers in the new enclosure comparing it to the older smaller enclosure with two of them. The first impression is well known, one driver delivers generally a thinner low frequency response than two. The doubling of the cone surface adds the physical fact of doubling with three decibel the bass energy.
But not only, one driver in the new the structure sounds a good bit better defined, foremostly in the upper registers of its frequency cut. Here we are talking about a 6 dB cut off at around 300 hz. This effect is very little, but seems to support the general transparency of the whole system up to middle frequencies.
Comparing it directly to still existing other enclosure beneath, confirms the listened new result. The double driver cabinet gives more low frequency energy, but it is less colourfull and less transparent portrayed, and sounds a bit overtoned. At this early beginning of our audition we weren't save about the reason. Is it the size of the new enclosure with its lower possible physical response, or is it's rigidness, which gives a more uncolored deeper response? Or might it even be the higher impedancy of 8 ohms, which betters the power amplifiers ability to control the chassis? The extremely low impedancy of 4 ohms is not a ideal load for the Shindos, we have seen several other amps here with a complete break in!
The mounting of the bigger LineMagnetic 15'' driver might give answers to such open questions. First of all we talk here about a field coil driver with coated paper cone, paper surrounded, but not as lightweight as the vintage German Klangfilm cone. Another aspect is the higher impedancy of 16 ohms. From all my experiences in history it was absolutely clear that a 15 ohm speaker is always a better load to any tube amplified transformer coupled device, even when there are different secondary options at the output transformers for lower loads. A slightly bigger cone surface brings in another extra for deeper frequency response.
|The LineMagnetic BA-15 with its dedicated adapter board inside the TA7331|
The prepared adapter board was quite fast mounted to the enclosure, cabling to match the tungar power supply were as well ready to go. The built in passive crossover with Tango stepped intuctor coil made the quick change possible, a perfectly matching value was just a new contact of its coil.
With the first tone the sound changed dramatically. We had suddenly the feeling not any longer to listen to the same audio set, we did do for so long. Something completely new happened and shifted the overall soundstage to a former unknown domain. The sound got dramatically more dynamic with a real load of better resolution and scale. The low frequency response got extremely better articulated, still a bit withdrawn in terms of energy, but exceptionally better defined. It sounded 100% better resoluted even in the middle frequencies. Here the 22A-horn was a lot better intercepted, its enormious qualities in resolution and dispersion of the micro dynamic detail seemed to be extremely improved by now. Coming from the single Klangfilm driver, it sounded double dynamic and unbelievable better defined in the most frequencies of the complete soundstage.
What made this exceptional step forward possible? Again, do we talk about size or rigidness of the enclosure? Do we talk about a better energy transport inside the enclosure structure? Or is this step mainly build on better matching impedancies of the chassis to the power amplifier? Actualy it looks of course that it is a product of all attitudes together, but I am quite safe about the fact, that it is not the deeper and bigger size of the enclosure. It seems to be mainly solved by the rigidness in combination to the improved impedancy of the chassis as driveable load. The tungar power supply and the field coil magnetic unit might be as well in count for such a difference, but this question needs further investigation. Another options of 16 ohm drivers might be be tested soon to get safe insight. As well 18'' chassis will be in evaluation soon.
After this experience we switched the set back to its long term standard low frequency support, the doubled KL-405 in its smaller enclosure. The first impression was, there must have gone something faulty, it cannot be! It is sounding completely failed, indifferent detailed with too much upper low frequency energy, which is overlaying the horn and influencing its abilty to express and resolve in finest micro detailed structures. It is unbelievable that this sound was the highly aproved state of art for some years!
Yes, it sounds unbelievable stages better defined and with extremely better resolution over the complete tonal scale. Its dynamic articulated attitudes seem to be doubled, the projected scale of information has got widen to an extreme. Everything is there a whole lot more...
Can this be? What is the secret to double your income without more work to do? Were do you get the double output of something without changing the input? Might it be a classic case of illusion?
Yes and no. We are still considering all aspects. A rigid enclosure helps to perform higher energy levels with less contributing side effects. Different than ordinary other enclosures, which need to handle middle or even high frequency drivers, the low frequency dipole works very different in terms of resonance distribution. Here the rigidness does not influence negatively the response of the higher registers, instead the rigid construction enables a deeper response of lowest tonality without resonant effects. The weak smaller enclosure brings in a lot of unwanted resonances influencing the exceptional abilites of the 22A through thinner boards and less stiff bracing. Supported by the better handling ability of the power amplifier of a higher chassis impedancy and as result a much improved sound structure, the stiffness adds up to a extremely better articulated refined sound in general.Mike is actually very impressed by such a differend result and will continue the evaluation process with other low frequency loudspeakers to find out more about such improvements.
But no sunshine without shadows. My personal rating is a bit more complicated. First it needs to be examined how a better postitioning of the units, which is actually not ideal to the listening place, will influence the result? Actually the sound stage is very complex and inhomogenous. Its difficult to find a smooth projected imaging of the music with naturally scaled instruments. Listening for more than two hours to music showes me several other inconsistencies. The former unbelievable attitude to play any sort ot music programe has gone. Instead the system shows up with very clear preferences to some small scale arranged music. Larger scaled classical orchestral music is played (let me say it carefull) with several problems. The sound structure is exquisitly detailed but at the same time shows tendencies to dry out and starts to get a bit cheeky. The low frequency response is extremely articulated but does not really seemless intergrate into the huge soundstage. It might be a problem coming from its physical ordered placing side by side of the other components. In former times the units were placed in optimal triangled composition in Mikes listening room, now they are far more positioned in distance to each other. The soundstage was before completely three dimensional holographic in a small centered listening position. It took not even minutes to forget about its coming into being in terms of technical realisation. I was able to forget completely its artificial sensation and accept it like a naturally released sound from an instrument. Actually in the suboptimal positioning of the new enclosures, the sound is some sort of disintegrated and dismantlet. Horn, tweeter and dipole seem to come from different origins, a problem very common with such horn installations, but again before completely unknown here, now very prominent.
To me such little defects are more or less inacceptable, till I am used to my Tannoy Dual Contentric units which are almost point sources and are able to convince with a lot bettered homogenous projection and a almost holographic sound stage. If you get used to such a speaker you are extremely sensitive for any sorts of phasings and time incorrections. Mikes new set has lost some of his former major qualities of a holographic soundstage in exchange with much improved dynamics and far better resoluted micro detail. I hope he will readdress these lost attitudes to his new system some day again.
But as well our audition has shown several unknown new facts, which need further investigation.
My personal conclusion would be a stiffer baffle board for his smaller old dipole enclosure and I would search for some fast and expressive, hard edged light weight paper coned 15'' chassis with 16 ohm impedance; if it needs a permanent magnet or a field coil is a still open question? As well the 18'' driver needs to be evaluated some time, if it can sing, we never might know – the answer is going to be a bit expensive. The main question is for me, is it worth to give all the positive cooperative results away for just a little better resolution and dynamics? But it is like always, once heard, it is difficult to struggle back.
With such dipole enclosures the bass chassis can give very different sound directions into the whole system. It is a bit like a typical wine tasting process, there will be some extremely different tasting candidates out there. Each of them will shift the general sound stage to other illusions and its just like the wine, you need to find your personal favorite...
Some people prefer beer against some wine, the active driven solution is just a whole own story to find ways into heaven. i am sure it will take years to find a way...
Read on soon,