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Thread: Makie a JBL 2234 with a 2225

  1. #1
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    Question Makie a JBL 2234 with a 2225

    Hello,

    I read a lot of things on this forum. (many interresting informations)

    Actually I have a pair of 2225H, and I would like to know if I can transform them on 2234H ?

    - by replacing the cloth surround by a new foam surround...

    Considering that 2231 2234 2235 2225 have the same basket / engin, and that JBL sould prefere to save money and produce the same cone / coil:

    "is someone on the forum know exactly what are the differences between the 2225 and the 2231 ?" ( Cone / coil / spider / surround )

    Many thaks for your help

  2. #2
    Senior Member RMC's Avatar
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    Hi Surfer,

    Welcome to the Lansing Heritage Forum.

    Sorry, but i'm not convinced this would be a worthwhile undertaking. I think you will end up with an imbalanced woofer. Coil, spider and surround were designed for a specific performance and excursion level in mind.

    Usually sound reinforcement woofers (e.g. 2225) have stiffer suspension system and hi-fi/monitor woofers have a more compliant one. What you're trying to do would be a mix of both: a more compliant foam surround allowing more cone excursion, working together with a stiffer spider trying to restrict such increased displacement.

    Can the coil and spider travel the extra distance afforded by the foam edge? And without increased distortion? i doubt. Some driver parameters may also change in the process.

    The other way around (from foam to cloth surround) might have been somewhat more logic, though still an imperfect solution.

    Richard
    POWERED BY: QSC, Ashly, Tascam, Rolls Mosfet, NAD, and Crest Audio

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    Hello Richard,

    Thanks for your reply... I understand you must be right !

    It sould be logic, but, "Are you shure that the spider and the coil are not the same ? "

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    Senior Member 1audiohack's Avatar
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    Hi All;

    I donít think that any of the moving parts are the same. Well the dust cap and maybe the tinsel leads.

    From a George Augsperger note I have: The cone is specific to the 2234/2235. They are made by Hitachi from very hard paper. Most other JBL woofers of the age have cones manufactured by Hawley.

    If the goal is to lower the FS of the 2225 then changing the surround may bring it down a little but as has been mentioned a moving system is a system and there is a possibility of creating unforeseen problems by changing components of that system.

    That said, 2225ís are still plentiful and inexpensive here in the states and few would worry about experimenting with them.

    What's the worst thing that could happen? Reconing them with C8R2235 kits and you end up with what you want anyway.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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    Senior Member 1audiohack's Avatar
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    I forgot to mention, the coils are not the same. The 2225 is 0.63Ē / 16MM long where the 2234/2235 is .75Ē / 19MM.

    The only thing I donít know for certain is the spider rate but I have to assume that the 2234/2235 is one letter softer than the 2225. I believe there are A through D spiders with A being the softest. However my memory could use some work!

    Also, I measured the FS of four 2234ís that I replaced the surrounds on and the difference with no surround and new surrounds was less than 3Hz. So the 2234 surround contributes little the the resonant frequency of the 2234. Measured with the driver vertical of course.

    Based on that information you could measure the 2225ís FS, cut one of the 2225ís surrounds out remeasure and get an idea of where the FS would land with a thin foam surround.

    Barry. Whoís not afraid to hack.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  6. #6
    Senior Member RMC's Avatar
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    Had this already in the making.

    The JBL driver listings i have don't give the specific part number for each component that goes into a driver (e.g. no coil or spider part number mentioned). The only sure way to know if the exact same.

    But lets assume the voice coil and the spider are the same for 2225 and 2234 as you mention. Apart from knowing or not if the foam installed is the same or not as the original one for 2234, you still have yet another problem.

    Changing the surround to a more compliant one (cloth to foam) will cause the driver's Vas and Qts parameters to shift (as per Eargle) and both of these influence the proper cabinet volume. Then you need to measure the new and actual woofer parameters that are impacted, with a software program such as DATS or Woofer Tester before building a box.

    Also, a member who tried a surround change from foam to cloth saw his driver's Fs parameter increase markedly, while some others varied less. Based on this, one might expect that, from cloth to foam surround, there could be a shift downards of driver Fs, therefore modifying some box ratios like the tuning factor and the F3 factor, both of which take into account the driver's free-air resonance frequency (Fs).

    So not an easy call. These are things one should know before jumping in to avoid regrets.

    Richard
    POWERED BY: QSC, Ashly, Tascam, Rolls Mosfet, NAD, and Crest Audio

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    Thumbs up

    Hummm.... ok guys!

    If ¬ďcone + coil + spider¬Ē are not the same ... it's dead! . I imagined that It was a wonderful option, but there is no miracle.

    - I'll keep the 2225 basket and I'll recon with a 2235 recon kit, if it's the only one solution, it would be 'tip top"


    Many thanks for all these "very interesting" information

  8. #8
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    Buy the 2235 kit, if you can find a pair, but leave off the mass ring leaving it a 2234. I wish I would have had this done to mine when I had the 2205s reconed as 2235s.

    Ultimately, I am far happier with a pair of 2241Hs which don't require that much larger of a cabinet.

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    https://jblpro.com/en/site_elements/2225h-j-information

    Modelling the 2225 driver with its 97 db sensitivity gives a QB3 alignment with a box volume of 50 litres and a port tuning of 56 hertz and F3 68 hertz. Depending of what your doing this driver could be used for a mid bass application to a large horn from 500-1200 hertz. The jbl spec sheet suggests a response out to 1200 hertz.

    Itís high 97 db sensitivity in a compact enclosure mid bass ported enclosure is the best attribute for a home diy situation using a low power hifi amplifier. Simply use a sub woofer below 80 hertz and you have a workable system. A driver with 97 db sensitivity and a lower Fs typically requires a physically large enclosure of 170-240 litres but the bass response F3 is still limited to 40 hertz. The x max of 5.00mm means itís really only useful as mid bass driver.

    The 2234 will require some bass boost to achieve a similar response to the 2235.

    Something to think about.

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    Quote Originally Posted by Ian Mackenzie View Post
    https://jblpro.com/en/site_elements/2225h-j-information

    Modelling the 2225 driver with its 97 db sensitivity gives a QB3 alignment with a box volume of 50 litres and a port tuning of 56 hertz and F3 68 hertz. Depending of what your doing this driver could be used for a mid bass application to a large horn from 500-1200 hertz. The jbl spec sheet suggests a response out to 1200 hertz.

    It’s high 97 db sensitivity in a compact enclosure mid bass ported enclosure is the best attribute for a home diy situation using a low power hifi amplifier. Simply use a sub woofer below 80 hertz and you have a workable system. A driver with 97 db sensitivity and a lower Fs typically requires a physically large enclosure of 170-240 litres but the bass response F3 is still limited to 40 hertz. The x max of 5.00mm means it’s really only useful as mid bass driver.

    The 2234 will require some bass boost to achieve a similar response to the 2235.

    Something to think about.
    Many thanks Ian,
    I'll keep that in mind ! ... I think that I will recon directy with a 2235 recon kit ! .


    - I have a paire of 4430 and for me the sound of the 2235 is the better a never heared.

    I never heared the 4435 ( 2 x 2234 ), but a lot of peoples told me that it was mutch better that the 4430 ( 1x 2235 ). i'is for this reason that I asked this question (2225 to 2234) It was just to test it!

    - I also have a paire of 4645C with the 2245h (original, with the aquaplast) It's more low but less reactive as a 2235 H.

    After that, I planed a do a cabinet with 2 x 2235 ( apolito style ) to keep the reactivity of the 2235 but the 2245 sound level.

    What do you thing about that ?

  11. #11
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    You have some good plans.

    The difference with the 4435 is one woofer works only below 100 hertz. This compliments the other woofer with the port tuning to produce a response down to 30 hertz with full power output. The 4435 is tuned to 26 hertz as an over damping system. The bass out of the 4435 is excellent. Better than a single 2235H. Deep extension and good linearity or authority. I prefer it to the 4355.

    The other difference is that without the mass ring there is 35 grams less mass at the alex of the voice coil and the inner cone termination. The effect of the additional dead weight is to lower the free air resonance and flatten the midrange response. But the down side is the motor /cone assembly has mass induced loss in transient definition in the midrange or speed. The mass at the voice coil is simply too heavy to keep up with the speed required to accurately operate in piston mode in 500-1000 hertz range. When you hear the 2334 driver is far more resolving. Itís a not brainer.

    I recommend you try removing the mass ring and simply put on a new dust cap. The low frequency range can be electronically equalised or use your 2245 to fill in the bass.

    The dual 2235 system would be cool with a horn that can start at 650 hertz like the Yuichi radial horn.
    I would consider dual 2234 cones and set up the woofers so the top 2234 only operates below 100 hertz. That way you donít have to be concerned about the driver spacing of the Díapolito design.
    Ian

  12. #12
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    [QUOTE=Ian Mackenzie;442129]
    You have some good plans.

    The difference with the 4435 is one woofer works only below 100 hertz. This compliments the other woofer with the port tuning to produce a response down to 30 hertz with full power output. The 4435 is tuned to 26 hertz as an over damping system. The bass out of the 4435 is excellent. Better than a single 2235H. Deep extension and good linearity or authority. I prefer it to the 4355.

    The other difference is that without the mass ring there is 35 grams less mass at the alex of the voice coil and the inner cone termination. The effect of the additional dead weight is to lower the free air resonance and flatten the midrange response. But the down side is the motor /cone assembly has mass induced loss in transient definition in the midrange or speed. The mass at the voice coil is simply too heavy to keep up with the speed required to accurately operate in piston mode in 500-1000 hertz range. When you hear the 2334 driver is far more resolving. Itís a not brainer.

    /QUOTE]

    Yes ok, logic, understood, for the linearity issue with the mass ring in transient definition in the midrange.


    [QUOTE]
    I recommend you try removing the mass ring and simply put on a new dust cap. The low frequency range can be electronically equalised or use your 2245 to fill in the bass.
    /QUOTE]

    I would like to keep my original 2235 in there original stat . It's for this reason that I bought 2 x 2225 ( and I will receve two other 2225 soon ). In fact I have 4 recon kits for 2235H from "The Simply speaker". The fact is that's very expensive. From your contry to France with shipping + taxes it coast arrount $650 by pair !
    It was bought "in case", where I had to recon my old 2235H for any reasons ( from JBL 4430 ).
    My plan was to resore 4 other 2235H built with the 2225 basket + the 2235H recon kit, to test a new system with 2 x 2235 (+ Medium + tweeter).

    To test your solution (2234) I can use a more cheap kit like the "SS Audio Recone Kit for 15 Inch JBL 22xxH", do you have an opinion on it ? I don't want to play with my brand new JBL kits and replace the dust cap if I need to add the 35G ring after (...if I burn one of my old 2235).


    [QUOTE]
    The dual 2235 system would be cool with a horn that can start at 650 hertz like the Yuichi radial horn.
    /QUOTE]

    If sould be a good solution for me.

    I would consider dual 2234 cones and set up the woofers so the top 2234 only operates below 100 hertz. That way you donít have to be concerned about the driver spacing of the Díapolito design.
    Ian
    I don't realy understood your solution. You suggest to use dual 2234 below 100Hz !? or just one of then under 100Hz like the 4435 config ?

  13. #13
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    Firstly if you are considering your own diy loudspeaker what you plan is entirely up to you. The notion of a diy loudspeaker is that you should be able to build an equally good or better loudspeaker than a commercial product for the same outlay.

    Generally a good deal of trial and error experiments will yield a better diy loudspeaker than attempting the ultimate diy loudspeaker from your original concept.

    The Mass Ring
    The mass ring makes the 2235H function like an extended bass woofer with relatively small box volume. That’s why they did it. Using a larger horn with a lower crossover point of 650 or 500 hertz will minimise the trade offs of the mass ring on the midrange clarity. The problem is real once you hear the difference. A 2335H sound muffled or muted in comparison when used in the bi radial 4430 application.

    JBL 4435
    In the case of the 4435 one woofer has a low pass passive filter at approximately 100 hertz. The 2234H woofer has a low port tuning frequency and the response tapers off slowly below 100 hertz.

    The second 2234H operates up to 1000 hertz then crosses over to a bi radial horn. This woofer also operates below 100 hertz in an identical manner to the other woofer. What happens is the response of both woofers combines to give a flat response down to the F3 at approximately 30 hertz.

    MTM loudspeakers
    The technical challenge of all MTM loudspeakers with crossover frequencies lower than 2000 hertz is avoiding comb filter interference between the two woofers. This is caused by phase discontinuity between the woofers when they are operating at both the same frequency where the woofer spacing is equal to the wavelength of that frequency. What you see if you do a measurement is a corrugated bumpy frequency response. The subjective effect is a flat planar sound quality that is annoying after a while.

    To minimise the comb filter effect you need to move the woofers closer together. The problem then arises that there is little or no space for the horn between the woofers. At 800 hertz the wavelength is 43cm. However the space between the frames of two 15inch woofer spaced 43cm apart at the cone centres is only 4.5cm.

    Reducing the crossover frequency down to 600 hertz will increase the space between the drivers to 19 cm. However a typical 600 hertz radial horn may not fit in this space. A 500 hertz crossover point will provide 30cm of space which is more acceptable.

    Alternatives
    The subjectivity of comb filtering should not be underestimated and can spoil the use of good quality drivers. For this reason some of the older dual 15 inch woofer systems such as the Tad monitors had the dual woofers close together in the horizontal plane with a large 650 hertz bi radial horn above the woofers. They also used a step 6th order passive low pass filter on the woofers. These monitors were regarded as a reference in many studios and became a de facto design.

    Another possibility is to use an 8, 10 or even a 12 inch dual concentric driver between the two 2235H woofers. The benefit is that you can then lower the crossover frequency much lower and still enjoy a point source sound throughout the mid and high frequencies. Loudspeaker manufacturers such as Radian, B&C, 18Sound make excellent dual concentric drivers using horn or ribbon. It’s worth looking into and you may well achieve a better result than a costly horn and compression driver. (crossover frequency of 250 hertz). Large horns look good but seldom does the subjective performance match the looks.

    The devil is generally in the detail of a good sounding loudspeaker and thus is equally true of a diy loudspeaker.

  14. #14
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    An additional thought would be to make your MTM using three separate modules stacked on top of each other. That way you can play around with different horns or other options as l mentioned or even adopt a horizontal approach to the woofers if you prefer.

    All too often a diy loudspeaker builder conceives his design before the building it and never has an opportunity to try some options. This is important where the original design is not up to your expectations. Even the best ideas do not always impress our ears. This is what makes building a diy loudspeaker some of an art.

    In general conceiving your own final diy loudspeaker design before building it is a huge leap of faith. Cloning a previous known design closely has a much higher probability of success if you only intend building the final enclosure from plans.

    The fun part is always the journey. What you build you have to live with.

    I hope that makes sense.

    Ian

  15. #15
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    As I said, a pair of 2241s is preferable to my ear, and the RTA, than a pair of 2235s. And I have both to listen too.

    This is the original issue CD played on an Oppo95 through a Yamaha RX-Z9 Receiver in "Pure Direct" mode through the Mermans (JBL 2241H, JBL 2251J, Heil AMT) with no eq, digital processing, or room correction, electronic or physical. Room is quite large, and you hear it in the recording.


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