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Thread: 4343 crossover modifications

  1. #331
    Senior Member Ian Mackenzie's Avatar
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    Jean,

    I saw your results and will try to interpret..


    I have a good reference on such and but it refers to loudspeakers per say:

    Basically it relates to the panel resonant modes due to torsion and panel flexure, their frequency and magnitude dependent on the Q of the material and also its thickness and density. With an increase panel thickness and density resonant modes are less likely to be excited.

    Densities vary, lead being 11.3 x 10 3 kg/m 3, chipboard 0.81 x 10 3 kg/ m 3 and plywood depending on grade 0.67 x 10 3 kg/m 3..

    Enclosure Resonance is extremely complex but essentially a clamped panel will have its own acoustic output when forming part of an energised loudspeaker, derived from sound within an enclosure.. The output consists of standing wave modes at higher frequencies and pressure modes at those frequencies where the wavelengths exceed the internal enclosure dimensions.

    In theory, a clamped panel has a well defined vibrational series in both longtitudinal and bending modes. A further mode is due to panel mass resonating with its own and the enclosure's air volume stiffness.

    Many have attempted to control panel resonaces with limited success. The results dissplace such resonances to more subjectively acceptable frequencies but not their magnitude. Sand can be effective but is awkward to use and mass soars dramatically. When damping is used to control resonance, the Q of the panel is reduced.

    But where high mass was an advantage, it is detrimental with panel damping.

    Resonance contol uses the principle of dissipating energy through friction and a given panel should be laminated with a layer of comparable mass. The mass equivalance ensuring that a good mechanical match is achieved b/n the layers to permit the effective transfer of vibrational energy from the panel to the damping material.

    I hope this makes some sense.

    I would also point out that an often overlooked fact is that adding fibreglass to cavity actively absorbs vibrational energy through frictional losses and therefore assists in reducing enclosure related energy transmission..

    The Doctor

  2. #332
    Senior Member gerard's Avatar
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    Jean - b&kman


    I saw there is fiberglass all over the 4343 ; Do you think it is better .
    My clone only have in the low part of the system ? .

    Gerard

  3. #333
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by B&KMan
    I put a vibration analyse of caps in regards on the nature of panel fixation and no nothing comment...
    You were surprised (and somewhat dismayed) to find that solidly fixing the components to the substrate serves to directly transmit the substrate resonances (which are within the audible range) to those components.

    Now you must damp the substrate. Am I gettin' this?

  4. #334
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Zilch
    You were surprised (and somewhat dismayed) to find that solidly fixing the components to the substrate serves to directly transmit the substrate resonances (which are within the audible range) to them.

    Now you must damp the substrate. Am I gettin' this?
    Medium density foam rubber and secured with cable ties seems to work.

    I put everything in an enclosure, A) to survive the delivery B) to keep the noise out of the works!

    The Doctor

  5. #335
    Administrator Robh3606's Avatar
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    You can use a buffer material. I use 3/4 inch fiberglass ceiling tile between the actual crossover substate and the speaker side panels. You can keep the wire leads off the panels or use a staking compound that absorbs vibration like a pliable RTV.

    Rob

  6. #336
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by gerard
    Jean - b&kman


    I saw there is fiberglass all over the 4343 ; Do you think it is better .
    My clone only have in the low part of the system ? .

    Gerard

    Hi dont know if you remark the x cross wood under fiberglass for support the HF and all fiberglass is flue in frame plus 3 sheet on top for hf and uhf section... Yes i is strongly recommended because it is destroyed the standing wave prisonner on top section... Remind the 4343 the event is just very low botton and med close box create a cage resonnator so for more control ( conform to engeneer I recommand to put in )



    Jean.

  7. #337
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Zilch
    You were surprised (and somewhat dismayed) to find that solidly fixing the components to the substrate serves to directly transmit the substrate resonances (which are within the audible range) to those components.

    Now you must damp the substrate. Am I gettin' this?
    Yes and no.. (english transaltor maybe)

    Shit back, keep big drink, chip, and play maybe a printer version and read slow this fundamental study of vibration oriented in acoustic

    (i hope is not to hermeneutical exposition and my english support the very tuff synthese of what is what... )

    (I dedicace this post in all members who help me strongly in my poor conception in electronic...




    =====================================


    All material have a natural vibration (right?)

    more soft or massif = more down amplitude... (right?)

    The thin massonite is light and is same material of thick massonite)
    So I realise in this test the vibration is normally down with increase the mass

    so the thick is normally create less vibration and normally absorb by mass the vibration of caps...

    Bad surprise the thick massonite is vibrate same as thick.. but, because it is more mass, the excitation contain more energy and create a more resonnace transfert on caps than only natural resonnace caps only... so the total vibration is increase !!! in this case the thick massonite is create resonnace on caps than keep resonnace on caps... (double bad way)


    keep same in other hand, I hope it is more clear in this..

    the test modal expose the thin is not realy good but better than thick !!! because if the thin is not keep the energy on caps by mass but it is not create a double hit resonnace energy (create by thick.):the thick create double peak resonnace and appear in listener more flat but in reality is induce more distortion in caps and finnaly in signal so the total noise is higher and if not keep engergy vibration is give on caps extra energy...

    interpretation of ear listening:

    remember the first criterion of discerne coloration is the power of peak and restriction in spectrum... In fact if you have peak in entire spectrum, you not keep signature but just not discern the detail hidden by this noise floor.

    Ex: is you play pink noise and induce a sinewave you ear is detect the coloration immediately but if I put narrow noise in pink noise, you ear keep difference but not discern what is what, etc, etc, etc,

    I try in other exemple, if you put a diapason into body of guitar you listening clearly the note but more powerful...= natural amplifing...

    So the thick and thin massonnite have natural frequency and at this resonnace is play same a diapason on caps... so less power is better and if you material have multi-discrete resonnace than a major single peak, you hit 2 function:

    1--- you not produce resonnace energy in caps and
    2--- you have a great opportunity to keep the energy of caps for restriction of natural frecquency of caps= less resonnace caps noise....


    In theorycally the next point is realy specific on acoustic problematic...

    Normaly, the engeneer is work to create a damping structure for limiting the amplitude of natural frequency... in case of audio, this damping is only valuable by approach of hysterical or structurally damped...

    Why ?? reason: TIME DISSIPATION ENERGY !!! (see pict)

    The engeneer, on standart structure, not consider if is create a secondary peak or more bkgnd noise ... For audio the time dissipation is critical... more than .2 ms the signal bkgnd noise is push up and blur details, space ambiance, etc... so if you put asphalt, rubber, neopren or any other absorber, the peak is converted in time dissipation so you reduce the peak amplitude but increase bkgnd noise floor...

    so the best in the best is create a sandwitch with multi material : all material is hard and lower than .2m delay dissipation peak but each have big difference natural frequency... so each resonnace is cancelled by the other with out increase time dissipation (right ??)

    Add at this principe the concept of mass for inertia and you result the best : big mass with composite of hard material for cancelling peak resonnace... and Voilā !!!... apply this concept of box enclosure, board electronic or electronic unit, stand speaker, or stand electronic and you produce the best of the best inertia as possible...

    If you control each aspect of the vibration insertion on your sytem you control a big aspect of problem coloration. but if it is not sufficient for garantee the result: it is necessary for good way of flat and ultra realistic reproduction...

    Ex: Mr hiraga, (world sommit of horn specialist) consider a enclosure of sand arround horn is garantee this horn is not generate a parasite natural resonnace in sound because the freq of sand is too high and the capacity of absorb fast with not extension in time dissipation...



    Finnaly, for more specialists in read this, last aspect is not cover by this small experience is factor of air born sound transmition...

    Same as romm, insulation is 2 magor factors: impact energy and air sound...

    this is second aspect explain what it is important to create hard connection of caps to material... the air sound produce exictation on caps and result in resonnace free without never material to reduce this resonnace... So if you put caps in the air the energy of caps is not go a way to go out of caps and energy is just procure more resonnace...

    but if you put damping material, you affect this rule in amplitude to distribute enrgy in time so you put up the bkgnd noise... plus you create a seond signature of the damping material into caps...

    So it is strongly important to fix caps hard to higher mass as possible and this mass is more fast dissipation energy as possible...


    I understand many guy Is create apparently good result with out this rules but if you keep sofisticated material analyser, you realize many fantasist apporch...

    I hope this rules is help anybody sam this few member is help my in electronics... I knoe the material for analysing this is (extremely prohibitif).


    I conclude by exemple in quest in my young age... I have a big rock sstand slab for support my electronic andunfortunatly the sound result is realy harch.... So I try to tune the slap with damping eleastomere... smal peice, med peice, full, lead, woood, etc, etc, etc, finnaly couple years later , after my lab, I check my slab tuned... The result is simply catastrophic, after applied the rules exposed here , the result is just incredible... but the moral of this story is my damping material is tune a peak for 2 db but the real power peak is 32 db !! so imagine the futile correction is here....

    Jean

    Weel, time for beer yuk yuk yuk !!!



    Jean.

  8. #338
    Senior Member B&KMan's Avatar
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    Here pict who I explain as possible the phenomenon of damping problem in time

    Jean
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  9. #339
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Robh3606
    You can use a buffer material. I use 3/4 inch fiberglass ceiling tile between the actual crossover substate and the speaker side panels. You can keep the wire leads off the panels or use a staking compound that absorbs vibration like a pliable RTV.

    Rob
    Euh sorry what is pliable RTV ??

    Jean

  10. #340
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by johnaec
    Hopefully, some other members here will get the chance to listen to tham and add their opinions also.

    John

    Well, thanks for gentlemen appreciation, unfortunalety, I leave in quebec canada, so the listening is tuff at this distance, I try to record with my B&K result with part tune but my old computer is too fast saturated...

    So I compansate by pict and result analyser...

    thanks again for good words...




    Jean.

  11. #341
    Senior Member B&KMan's Avatar
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    OK dokay, fresh new for tis project...

    I send a couple of pict to speakers and the bignet install on back, most details of insides speakers for cloner guys...

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  12. #342
    Senior Member B&KMan's Avatar
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    Installation on bignet....on back of 4343

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  13. #343
    Senior Member B&KMan's Avatar
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    Finally replug speaker and most important, place exactly at same place and angle position...


    and result of sound speaker left in grey bar (3143) and (in highlight line) the result of right with bigNet...

    --- First constatation: my uhf is not good... (it is not my first modification caps it is a cone replacement )

    --- second constatation the response of each driver is really differ to original response...



    I feeling wrong problem network...
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  14. #344
    Senior Member B&KMan's Avatar
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    Why I have hole in mesure...

    I mesure each driver individually out of box with network... I put pink noise and mesure with mic at 2 inch of outpput for keep clean response driver...

    see pict for detail....
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  15. #345
    Senior Member B&KMan's Avatar
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    Ok now I compare each driver to next other....
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