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Thread: 4320 Project

  1. #1
    Heather [Senorita member] hjames's Avatar
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    4320 Project

    I worked in campus radio at USC (So. Carolina) in the early 70s and got spoiled by the sound of the JBL 4310 Studio Monitors. After school, in 1976 I bought my first JBLs - a set of L36 Decades (still have them and love 'em).
    After finding the heritage site last year I decided to upgrade my system and started looking for a set of L300s (or even L200s) I could upgrade, but the eBay prices quickly went beyond what I could justify for a set of speakers.

    Mid February I saw a set of "JBL 4505" speakers on eBay. I checked the site and with some helpful folks here I found they were actually 4320 Control Monitors - a 2 way system for recording studios from the early 70s. http://www.lansingheritage.org/html/.../1972-4320.htm
    They were big boxes and required local pickup ... so after a brief delay for a snowy weekend, we drove to Philly and
    brought them back to Virginia.

    I found a pair of 2405 drivers with diaphrams to install, again, on ebay, so they were bought and delivered a week later. I'm not a sound engineer, but I do have a technical background and know how to solder. I'm sure they weren't JBL diaphrams, but I could install the furnished diaphrams and if they didn't work right, I could have JBL techs put factory diaphrams in later.

    I did a search here and found detailed directions on replacing diaphrams -

    http://audioheritage.org/vbulletin/showthread.php?t=700&highlight=2405+diaphram

    Anyway - here are a few pictures showing the stages of rebuilding the drivers, cleaning the gap with a piece of clear plastic (cut from the diaphram packaging)
    and the final image with dated stickers on the back.

    Once they were done I mounted them in the predrilled holes to the left of the horn outlet on the baffleboard, but I once I have the crossover sorted out I'd like to mount them above the horn.

    I followed a tip from Zilch and built a pair of 3106 crossovers to tie to the high output of the exisiting crossovers in the box, but I had almost no output on the 2405 slots - tho they worked fine when substituted for some tweeters in another speaker system in the guest room.
    I have minimal test gear these days - so I checked some crossovers for sale on ebay and found a pair for JBL L166 - the low cross was at 1000hz - the high cross at 6500 is lower than the 10k I'd like to use, but it allowed me to have all the drivers working until I can redo or replace the MF and HF legs of the crossover.

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    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  2. #2
    Obviously... not a golfer grumpy's Avatar
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    Thumbs up

    Nice project. Thanks for sharing the in-progress pics! -grumpy

  3. #3
    RIP 2011 Zilch's Avatar
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    Hi, Heather, and thanks for posting pics of your project!

    If you haven't come across it yet, there's a chain of threads over in DIY for a potential crossover incorporating the 3106, still a work in progress, beginning here:

    http://audioheritage.org/vbulletin/s...ead.php?t=8507

    For the bottom line, you can also jump to the latest thread here:

    http://audioheritage.org/vbulletin/s...ead.php?t=9221

    Once work on the basic crossover is complete, a 10 kHz version for 077/2405 seems a logical next step....

    [MORE pics, please. Yup, yup!]

    Quote Originally Posted by hjames
    I followed a tip from Zilch and built a pair of 3106 crossovers to tie to the high output of the exisiting crossovers in the box, but I had almost no output on the 2405 slots....

    I have minimal test gear these days....
    If you'd like me to check out your DIY 3106's with 2405's, PM me for the address to send 'em.

  4. #4
    Heather [Senorita member] hjames's Avatar
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    I took my 2405's downstairs and substituted them for the tweeters in a pair of Optimus 3 ways and they worked fine - so I know the slot-tweeters work fine. The 2420 horns and 2215 woofs had worked fine when I used the systems in their original 2 way config for the first weeks, so I figure thats all fine.

    The 3106 crossovers I built I had connect to the hi output of the original 3110 crossovers that came with the system didn't seem to work, and it was consistant no matter which one I put on either speaker - so I tried something new. I'm running the speakers in conventional mode with a standard 110w/ch JVC receiver, no bi or tri-amping at the moment ...

    I bought a pair of L166 (3way) crossovers off ebay ... the low cross is at 1k, the high cross at 6k (lower than I want, but its a test), and dropped them as the only network in the boxes. The speakers worked fine using them, but now I know what folks mean about harshness using the slots at the lower end of their range - I think I prefer feeding more of the mids through the horns.
    I dropped the 3110s back into the box, and fed the high output of those into the L166 networks. I dropped the lowpass (woofer leg) off the L166, and just used the mid and high output of them ... its closer, but I think I need to rework them and get the high cross up near 10k.

    I can gut them and use the precision resisters and the 4 JBL style Lpads to build better networks - once I learn what caps and chokes to use for the mid and high legs of the new 3way ... but I have to find time for that ...

    I got the JBL cloth from Zilch and bought a pile of pine lumber to build the griills - fortunately our cats don't seem to have cone destroyer tendencies - but we spent this weekend clearing the garden for spring plantings - and hoping we don't get a final snow before winter formally ends. Of course anything is possible in the DC area ... sigh ...
    Hopefully I'll get back to the crossover work soon ...
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  5. #5
    Senior Member jbl4ever's Avatar
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    Hello hjames, can you post a picture of the 2405 diaphrams front and back. They look like aftermarket by the one picture. Hard to tell. If they
    are aftermarket ones the impedance will most likely be different than stock. A impedance curve would be needed to properly design the new circuit for this.

  6. #6
    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by jbl4ever
    Hello hjames, can you post a picture of the 2405 diaphrams front and back. They look like aftermarket by the one picture. Hard to tell. If they are aftermarket ones the impedance will most likely be different than stock. A impedance curve would be needed to properly design the new circuit for this.
    Not easily - I'd have to pull the woofers to gain access to the drivers, unmount the 2405s, then tear down a working driver.

    In truth, I'd rather build the crossovers as if they were the right (JBL) diaphrams - once money is a bit less dear I may send the 2405s out for JBL pro rebuilds anyway, and if I build networks specifically for the aftermarket parts, I'd just have to redo the networks when I change.

    I got the 2405s on ebay - the deal was they needed diaphrams installed and a new pair of diaphrams were provided to install. Knowing that any set I bought on eBay have worn or tired diaphrams anyway, they were cheaper than most others pairs offered. From the price of JBL diaphrams, (provided free with the 2405s) I'll assume they are aftermarket.
    The diaphrams were sealed in clear plastic trays numbered DWT044S-8.


    3110 Crossover LF out to 2215 woof, MF out to L166 Crossover
    L166 Crossover LF leg (choke) removed - MF & HF only used
    2215 15" woofer
    2420 MF driver
    2405 HF driver
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  7. #7
    RIP 2011 Zilch's Avatar
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    Biased and Bypassed:

    http://audioheritage.org/vbulletin/s...ead.php?t=3555

    Why are we talkin' about this here?

    Because Heather asked, is why!

  8. #8
    Heather [Senorita member] hjames's Avatar
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    Charge Coupled Crossovers

    I've got a quick question. I've seen the reference to Charge Coupled crossover networks quite a few times in these forums - this is something you do for bi-amped systems right? I mean, you are doing this fancy crossover at a 1v P-P preamp output signal level, correct?
    The crossover pictured on the perfboard at http://audioheritage.org/vbulletin/s...1&postcount=28 doesn't look beefy enough for the 200+ wpc power levels you folks run these speakers at ...
    I ask because I want to build crossovers for the L300 equivs I am building from my 4320 speakers (2215, 2420, 2405) - and I want to be sure I'm using the right specs to do so.
    Thanks for the info!
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  9. #9
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by hjames
    I've got a quick question. I've seen the reference to Charge Coupled crossover networks quite a few times in these forums - this is something you do for bi-amped systems right?
    Nope.

    The charge coupled crossovers are standard passive networks being powered by your amplifier. The charge coupling means that they have a DC offset voltage that is reported to lower some forms of distortion caused by the capacitors. I have no personal experience with them, but the people who have tried them really do rave about them.


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  10. #10
    Heather [Senorita member] hjames's Avatar
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    I just ordered the parts to build Giskard's 4333/S300/L300 equivalent bandbass circuit - (the regular, not the Charge Coupled design)
    see - http://audioheritage.org/vbulletin/s...42&postcount=3

    After reading a number of threads here, I've also followed Giskard's design
    trick and put the Lpad and load resistors for the MF HF legs on an external board and mounted that on the back of the baffleboard. I even created a "foilcal" lookalike in photoshop, based on the 4333A foilcal that spirou38 offered here a while back. see - http://audioheritage.org/vbulletin/s...ead.php?t=9544

    I bought a cheap Ryobi tablesaw ($99 - Home Despot) that I can clamp into my Shopmate and I've cut down some lumber to build grills with ... got some Zilch cloth to cover the grills with, and a pair of metal JBL Logo badges to slip discreetly into the corner of the grill. I don't have a shed/garage so I just need some less cold weekend time to set up the saw outside and notch the ends of the boards so I can clamp/glue them together. More pictures later ...

    I'm hoping to get all this completed by mid-April ... and get the speakers off the floor so I can have my TV room back.
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  11. #11
    Senior Member remusr's Avatar
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    One thing that will change the sound vs a 4333/L300 is the use of your tighter 2215's vs the deeper extension/longer throw 136A/2231A's.

  12. #12
    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by remusr
    One thing that will change the sound vs a 4333/L300 is the use of your tighter 2215's vs the deeper extension/longer throw 136A/2231A's.
    Ok - should I gather that tightness is not a good thing? Should I just bite the bullet and start looking for a pair of the newer speakers. At the moment, its an all alnico system (for whatever thats worth), but my plan to update the crossovers should indicate I'm willing to do updates to improve the sound.
    2ch - Oppo981, JoLida502, JBL L200+, KEF 105.4
    HT7- XDA-2, BDP93, 4b NRB, B&K 5ch amp, Vandy 3A, 2Ce, VCC1, TF600 & JBL 4641

  13. #13
    Obviously... not a golfer grumpy's Avatar
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    I would toss into the ring that tightness can be a good thing. If using a 2215 in a box
    that's tuned properly, you might like it just fine. -grumpy

    "measure then cut"

  14. #14
    Senior Member remusr's Avatar
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    I have been told some prefer the 2215A/LE15A's to the (also Alnico) 136A/2231A or the newer ferrite 136H/2231H and 2235H. I have tried LE15A's in my L300's and did not like them as much as the 136A's for the lower bass & vocals. Tuning can overcome the bass issue somewhat - I think the 2215A/LE15A's work better in a larger box but have shorter excursion & lower power limits (shorter voice coil?). The 2235H may have better midbass/vocals than the 136A/2231A and can handle more power yet. Expect to pay $150ish each for EBay 136/2231/2235's...and then probably have to refoam them for another $75. My experience anyhows. NRT usually has a stock of woofs!
    - Roy

  15. #15
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    Quote Originally Posted by hjames
    I just ordered the parts to build Giskard's 4333/S300/L300 equivalent bandbass circuit - (the regular, not the Charge Coupled design)
    see - http://audioheritage.org/vbulletin/s...42&postcount=3
    I can certainly vouch for this network, it works just fine over here. BTW, I think there was a typo in the schematic, one of the resistors was labeled 40 Watts, I can't recall what I am using - I can check if you want. Maybe Giskard could chime in - but I think 40 W is overkill.

    Initially I used Solens, now they are Hovland (except in the low pass portion) in my non-CC version. Expensive, but well worth it to me.

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