M(A)TCH type crossfrequency management 07-2014

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rec1227-192622 piano

LC Crossfrequency Management System for Real Sound in Three Way Speaker System

 

 

Author

 

In 1976 graduated Electricity/Marine Electricity in Gdansk Technical University – Poland. In 2002 graduated also on the same University in Shipbuilding.

 

In professional carrier designed new ship’s power electricity systems, in 1991- 1995 serviced supertanker’s in 24 hours pneumatic and electronic automation systems service in ports and shipyards of Singapore, Dubai, Bahrain. Over 15 years Ships Class surveyor. 2006-2009 Managing Director established by him egyptian company in Egypt.

 

In 1991- 1993 member of Audio Engineering Society as Manager of owned by him company in audio field. Inventor of patent regarding Crossfrequencies managing circuitry. Since 1990 year engaged in hobbyist creation and playing music (youtube with nick Mikexception) and at the same time developing super real creation of sound with conventional drivers and passive crossovers.

          At the beginning author want’s to explain name „Crossfrequency management circuitry” given by him instead of traditionally „Filters” or „Crossover”. Apparently word filtering considers the meaning to predefined perfect separation of elements according to parameters from whole complex. In such way operate LC frequency filters in widely used crossovers. They target is maximum separation of bands each from other so eventual infiltration is treated as not proper. The idea of traditional filters is to create three independent systems speaker – filter to transmit acoustic signals which optimally, it means according to primary information delivered to terminals shall be added in the air. This systems called crossovers should not change time alingnment in narrow bands of frequencies and together with speakers not to affect the amplitudes. Moreover their parameters should match requirements created by speaker physical limitations to what author shall not comment as it is not in close consideration to the subject. Additional requirement is to pass the energy in more or less balanced way in function of frequency.

 

         All this is possible for crossovers only in very approximate ways due to fact that processes inside electromechanical systems in 1000 times range change of frequency in practice make it impossible to theoretical analyze. The worst structural problem created by them is providing a change in phase angle in ranges of cross frequencies what means that mathematically signals have parameters of vector calculation excluding their instant balance.

 

                In the past years author evaluated acuostic systems and crossovers. Subject of them were particular three : 1) pararel LC type 12dB/oct, 2) pararel and serial 6dB/oct, 3) serial electrical connection of special drivers selecting radiated band by their purpose. The last was long time ago applied in .old tube radios. What is interesting today most listeners appreciate their pleasant and non-obtrusive sound what should turn our attention.. It could be indication that after a years of efforts technique  of converting electrical signals to acoustic has stuck. Confirmation could be that today market is booming with multichannel constructions with subwoofers from 4.1 to 7.1 and more with artificial programming as replacement of real sound. Disappointed music lovers and audiophiles having more needs than computer multichannell are left in margin of expensive field, still not satisfactory due to complexity of combinations .

              As mentioned author’s attention was turned by specific disadvantages of some deliberated frequency division systems. The LC parallel filtering with 12dB/oct acquire unpleasant way of behaviour in ranges where the transmission is passed from one band to other. To hide this irregularities to level accepted by hearing usually side frequencies must be emphasized. It is not author’s desire to analyze deeply what is going on but the reasons are mainly contra phase distortions, not aligned speaker and crossover amplitude characteristics and additionally existence of created unwanted filters consisting of inductions of coils and resonances of diaphragms which are generating false voltages.

                Serial filters 6dB/oct have much less visible irregularities due to more stabilized parameters ( less speed of increase mean better compensation as mentioned in point 8 of thesis). The problems are wrapped good but their disadvantage is low damping factor and limitation to two band crossovers which together means barrier to bigger dimensions of lowtoner due to required tweeter power.

 

                For real sound, in author’s opinion, they are comparable to wideband drivers – they allow better alignment of characteristics but on minus add a phase shift.

 

             Serial electrical connection of special drivers was rare but as said used in practice with success. But it’s adaptation requires dedicated production of compatible speakers and is limited only to two bands. Using of tweeter is out due to idea of serial composition and required in such imagined situation power of tweeter. For this reason tweeter should be in parallel with condenser attached what means loosing of main advantage and we are then 50 years back. . .

            Presented system is back targeting popularization of real kind of sound which is not fatiguing or obtrusive, requires and provides extreme flat response and natural balance..

           Author would like to point that he is not involved in processes observed only in cables even they have impact in whole circuitry. He had not not observed deciding role of them for special impression of sound reality .

Standard frequency crossover wit 12dB/oct – brown color shows contra  phase operation

           Presented by author „Crossfrequency Management System” divides and applies to speakers frequencies of bands on basics of two functions: resonant filtering and inductance impedance comparison . To imagine it’s working we show it first  without coupling.

 

              As seen it is almost typical circuitry of known crossover where lowtoner uses 3rd level filtering m type and Middle and tweeter use its independent circuits of 2nd level. Common frequency 1,8kHz for all is explained below.

Real circuitry :

              The idea is to adopt normally rejected by one band signals to supply next band and vice verse. It is done by inductance coupling in following way: In both real ranges of passing the job, the good and transduced signal for given  band ( the screening is magnetic field) is deducted in coil L from next band increasing the selectivity while not used and phase shifted is added thanks to it’s shift. It is expected that some unwanted voltages generated by undefined resonant processes, normally resulting in apparent power, are getting loaded in side bands where are used and damped.

              So we obtain secondary mixing and secondary judging of signals primary divided by resonance LC.- this time by amplitude of field. It increases damping of filtering which is positive. The condition of this cooperation without weakening inside is to provide that LC resonance is out of range of the signals controlled by inductance – in practice must cover deeply each other and emphasize signals if coupling is null. Then by increase of coupling flat characteristic may be obtained.

             It’s job of primary is to secure the driver from not proper frequency and power instead of limiting the transmission. And that is awaited main advantage – .common signals pushed to drivers are not incorporating standard phase changes done by parallel operation. This changes are unavoidable in standard crossover filters and are resulting in sharp resonances in narrow bands. That is the problem fought now only by digital filtering. Adequate selection of LC parameters allows creation of safety barrier between this frequencies and precision magnetic inductance adjustment is done in analogue way.

              The philosophy of this approach is like double layer management – author had met similar philosophy in Intermediate Frequency circuitry of old luxury before 1940 radio receivers like Philips 753, 850, Elektrit Automatic – the selectivity was decided in two stages – one was standard double step selective amplifier with LC resonance circuitry and secondary was amplification controlled by IF signal normally not heard in speaker what resulted in hiding unpleasant band distortions during tuning between stations. It was rare solution met only in expensive receivers and required from producer very high accuracy in tuning. After stability of that tuning in time was crucial.

              Similar to that, presented system requires high accuracy in tuning to assure ideally flat characteristic and stability in time for that tuning is crucial. But in reward, not mentioning acoustic impression, the time and effort comparing to standard filtering design is much lower. It is enough to repeat settings and to keep them unchanged.

Following I present theoretical phase- amplitude function of circuitry.

Below for comparison widely used 3 way crossover theoretical phase – amplitude function.

Click to enlarge

 Wykres fazowy MATCH gotowy

Wykres fazowy m-type używany gotowy popraw.

Above I present theoretical amplitude changes in ranges of ,magnetic tuning

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Photos of arrangement

Below main dimensions of acoustic system. It is transmission line with primary chamber and 4 separate resonating volumes.

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Some small details

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Michal Czabajski.on 2013 july 19,                          01.47 hrs

Update no1 :  2014 may 15

Update no2:   2014 june 03 – added vector graphics

Update no3:   2014 june 19 – added phase – amplitude function

Update no 4:  2014 june 23 – Description „Phase factor” in phase – amplitude function replaced with „Phase non coherence”

Update no 5:  2014 July 10  drawing „Principle of operation added” some misspelling rectified.

 

 

 

 

 

 

638 myśli nt. „M(A)TCH type crossfrequency management 07-2014

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