need help choosing a JBl 128H replace driver

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Boyan Silyavski

Member
2016-05-16 11:12 pm
Denia
  • #1
    Hi guys,

    need some help with 12 drivers please.

    Some background:

    I have a pair of JBL L112 from many years. When i obtained them they were not with the original 12" 128H drivers, but some other 22xx something and as they were rotten i send them to the garbage bin. It happened that at same time i had some new like vintage 12", no name, so i just dropped them in. They play surprisingly well, even feeded by 150W 8Ohm amp full power, not that i do that very often nowadays .
    Meanwhile some other nice speakers passed here but at the end the JBL 112 stayed, i guess i find them perfect for me, sound, size, WAF
    Now they are carefully placed in room and sound very nice.



    So why to change the 12" then?

    Mainly because i would like some more bass, which i am sure i am missing with these.
    Then the 128H are not new, expensive to ship to Europe, very hard to find and who knows how they are reconed or repaired.
    Apart from that i would like to learn DIy speaker design, at least a bit, cause i looked last 2 weeks at DIY speakers and honestly couldn't choose one to build. Due to high price of speakers >1000euro, or low power, or this or that.. Incredible. i looked at least at 200 designs. The speaker i would like to build would be like the Statements but 2x10" instead of 2x 8" or even better 1x or 2x 12" bass in a transmission line cabinet. This SUMMONER 1293SRTL is one i like, but they are in Australia, i am in Europe... If there was a kit combining the Statements with the Summoner ...

    In other words i realise i am absolutely ignorant and will need a lot of time and first completing some projects before i make my dream speaker.

    So its obvious i could at least play with what i have. plus just finished my 8x4 cnc so i am eager to "better" things around me.

    The idea though is to start from things i love, i know and have idea what i want.

    So my plan is some step by step side projects for fun, while learning, reading, learning to measure, etc:
    -find suitable 12" driver for the JBL
    -make a clone of the L112 and now that i have figured the bass driver, see how the other could be exchanged with better modern ones
    -make a clone of the L150, which is essentially L112 in higher enclosure +
    -make some other speakers, for example Statements, Sb240 or Vota 4.


    So my speaker making journey started trying to find a suitable 12" driver, mean while learning what all these words and numbers mean.

    Anyway, after countless hours of browsing i have narrowed to 2 drives, having in mind Fs ~20-22hz of the original 128H, coil size and travel, at least what i understand as a total noob.

    - Monacor SPH-300KE , ~150 euro this one looks to me almost same same as the original, apart paper from kevlar, which does not bother me /now/

    -DAYTON REFERENCE HF SUBWOOFER - 8 OHM - 12", more RMS, a bit less sensitive, ~200euro


    I am attaching some documents for the enclosure, crossovers, etc.

    Any help will be highly appreciated. And yes, i don't want to buy the original 128h and forget,i want to learn sth new and experiment



    Meanwhile if sb has some idea on better tweeters and mids for the clone, without going too far from the original concept and sound signature of that speaker. For the future clone i mean.
     

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    Boyan Silyavski

    Member
    2016-05-16 11:12 pm
    Denia
  • #3
    johnlcnm said:
    Boyan,
    Have you asked your driver replacement question here: Lansing Heritage Forums

    Regards,

    John
    Click to expand...

    I have. Can you imagine what the answer is in a JBl forum?

    "buy the same drivers"


    But i am not willing to pay for old drivers prohibitive amount of money, if i could find new ones.

    Thats why i need somebody who knows just to take a look and confirm or not.

    Anyway, its not like building a spaceship critical
     
    pos

    pos

    Member
    2008-02-19 4:27 pm
    Paris
    rephase.sourceforge.net
  • #8
    Boyan Silyavski said:
    I have. Can you imagine what the answer is in a JBl forum?

    "buy the same drivers"


    But i am not willing to pay for old drivers prohibitive amount of money, if i could find new ones.

    Thats why i need somebody who knows just to take a look and confirm or not.

    Anyway, its not like building a spaceship critical
    Click to expand...

    http://www.audioheritage.org/vbulle...112-L150A-questions-possible-128h-replacement

    Believe it or not, the 128H is actually a very good woofer, even by today standards.
    Plus the passive network is build around it: chances that you will obtain an objectively better result with another woofer without investing major time and knowledge in measurements and network tweaking are not very high...

    :usd:
     
    B

    Boyan Silyavski

    Member
    2016-05-16 11:12 pm
    Denia
  • #9
    pos said:
    JBL L112, L150A questions, possible 128h replacement

    Believe it or not, the 128H is actually a very good woofer, even by today standards.
    Plus the passive network is build around it: chances that you will obtain an objectively better result with another woofer without investing major time and knowledge in measurements and network tweaking are not very high...

    :usd:
    Click to expand...

    I agree with you. Still searching for the originals. But, hey, their price has risen to 400$ a pair at fleabay, plus shipping costs, plus import duty, a big NO.

    I will be still happy to pay ~250euro for a good pair and 300euro for perfect white cones, which is their realistic price. the way i see it.


    Meanwhile i will be exploring other options, hence the questions. I have upgraded and updated all my system so last point are the speakers, hence i started investigating, even if i am sonically happy with the current situation.

    But more money than that i am not paying, as otherwise i will build something better DIY. I am quite tempted building the OBL-15 - Troels Gravesen , cause i have place and wife factor is not a problem. At least size wise, cause it will be easier to drop new woofers inside my JBLs than explaining why i need new speakers
     
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    helma

    Member
    2016-08-27 5:19 am
  • #11
    I'm bringing this thread back to life since I'm in a similar situation as the opener - the difference being my speakers are JBL 120ti, which also use the 128h woofer. They're about 60l vented boxes, tuned to 35Hz I think. The crossover frequency for the woofer is 900 Hz.

    I don't really understand that much about speakers, though I've been doing some reading and seems in obtaining a woofer, besides sensitivity I want Fs, Qts & Vas as close to original as possible?

    I haven't heard the original woofers so I have no baseline in that regard, and I'm not sure if these speakers will be keepers, so the objective here is to get them playing enjoyably with a reasonably neutral presentation, with a low budget. Anything more than 100 EUR per woofer starts to sting, which already makes the Monacor SPH-300KE @ 150 EUR a bit suspect - at that price with patience I could probably find refoamed originals.

    Below are the most important(?) specs for the original drivers and the affordable possible replacement I found:

    HTML: 
    JBL 128-h		fs 21 Hz    Qts 0.20	Vas 280 l 	(cone material paper) 


Monacor SPH-300KE	fs 22 Hz    Qts 0.33	Vas 250 l	(cone material kevlar)  

Monacor SPH-315		fs 22 Hz    Qts 0.24	Vas 330 l	(cone material polupropylene) 

Monacor SP-300P		fs 30 Hz    Qts 0.31	Vas 266 l 	(cone material paper, impedance curve shows resonance
								 closer to 40Hz) 

the box 12-280/8-W	fs 38 Hz    Qts 0.30	Vas 77 l 	(don't know the material - note: by 1kHz impedance is 
								 already 25-30 ohm)

    Now the questions ...

    Is the box 12-280/8-W totally out of the question due to the low Vas and the impedance curve that rises so much towards the crossover frequency? Would this seriously mess up how the crossover works? What I like about this woofer a lot is the price, which is 55 EUR at Thomann and people seem to like them in some applications at least. Getting the speakers running for 130 EUR or something, including delivery is a very tempting idea.

    There's another Monacor driver which I didn't include (SPH-300TC), which has even closer specs to the original, but it is a dual 8 ohm voice coil model - which threw me in a loop, but my understanding is I'd have to use only one coil to get 8 ohm impedance and the Qts etc. specs wouldn't really apply anymore in that case?

    Basically all the Monacors seem reasonable replacements to me, which one do you think would be the best? The SP-300P seems to have the resonant frequency quite a bit higher than the original, but it has a paper cone which I suppose might be good to get a sound signature more similar to the JBL 128-h?

    On a more general pondering note - original JBL stuff seems hard to source in Europe, but I suppose something like 123A / 2213 or LE-120H would also work reasonably in place of the 128-h - even if not the exact replacement it would still be genuine JBL which I figure would be better for resale value than having a Monacors in there, yet alone "the box" :)

    Thanks in advance, any help is much appreciated.
     
    H

    helma

    Member
    2016-08-27 5:19 am
  • #13
    No, I have no original drivers, I asked if they were still around but previous owner had trashed them years ago. Said they I didn't ask why, but probably because of rotten surrounds... I'm in Finland.

    All the original ones I've found thus far have been with what seem very inflated asking price, but it seems you're right, upon looking at eBay completed auctions etc. it seems the going rate for actual sales is more in the ball park of what you said, so maybe it's best to be patient and/or post some WTB ads on forums.
     
    H

    helma

    Member
    2016-08-27 5:19 am
  • #17
    Inductor said:
    As was said from post #4, the only one similar is this:
    SB Acoustics SB34NRXL75-8 (Europe w/tax: 253.00€ - no/tax: 209.10€)
    ... or Fostex W-300 II A for 1.149,00 € :D
    https://www.hifisound.de/en/Do-it-y...s/Woofer/Fostex-W-300-II-A-Alnico-Magnet.html
    Click to expand...

    I can't really see the reason why either the Fostex or SB acoustics would be better matches than pretty much any of the Monacors I listed above? I'm sure they are better woofers than the Monacors, or at least I hope they are since they are a lot more expensive. But the only significant advantage I can see on a glance is the SB acoustics extends further in the bass without going down so much. The Fostex doesn't have even that :) Am I missing something that would make the Monacors I listed above technically worse replacements?

    I found some 2206H and 2202H in Finland, the seller didn't list prices but it seemed he was having a clearout of accumulated stuff so I'm guessing price would be reasonable. Unfortunately other than being JBL, it seems those would be very poor matches and more intended for mid-bass/mid applications. Oh well, at least it was sort of close :)

    I even toyed with the idea of getting a pair of Peerless SLS 12 and closing the ports, making a 45 liter sealed enclosure, F3 would be @ 47Hz and I have a hunch that arrangement might actually work pretty well in my room, but then again it would be nothing like the original speaker.

    Again, getting the original woofers would be the best and I'd really like to hear those speakers as JBL intended them, why I'm stubbornly trying to find a suitable new / more readily available budget arrangement is I'm not really in a mood for hunting and getting impatient :)
     
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