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Thread: 4355/3155 clones

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    Administrator Mr. Widget's Avatar
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    4355/3155 clones

    I have gone on about this before, but here it is again with a bit more detail and info that may be of interest to others planning on a similar adventure.

    As most of you know the JBL 4355 was the largest example of the JBL 43XX series of monitors. It was an updated version of the 4350. It used slightly different components than the 4350 with a more sophisticated crossover design. The 4350 used the 3107 crossover and the 4355 used the 3155 crossover.

    http://www.jblproservice.com/pdf/Net...%20Network.pdf

    http://www.jblproservice.com/pdf/Net...%20Network.pdf


    Shortly after deciding to tackle the 4355 project I discovered that the 3155 crossover that I planned on copying used several tapped autoformers in lieu of standard inductors. I called JBL parts seeking these custom parts and was informed that I was SOL. In my search for a solution Giskard generously offered to contact G.T. (The original designer of the 3155 network.) and together they worked out the L-R networks to create an equivalent circuit to the original 3155 with autoformers.

    Below is a schematic of the new 3155. I added the 16 ohm and 8 ohm L-pads as per the original 3155, other than that I built this design exactly as suggested matching L, R, and C values to within 1%.

    Now the 3155 crossover is a passive 3 -way design meant to be used in conjunction with an active crossover to complete the 4-way system.

    I have used a 24dB/octave and a 12dB/octave active crossover to complete the system. I also tried the system with a 12dB/octave low pass section on the twin woofers and allowing the 2202 woofer to run out naturally being limited by enclosure tuning.

    I was not satisfied with the sound quality of my Rane AC22 crossover as to my ears at least it is not as clean and musical sounding as I would like. Unfortunately every combination that I tried with the 12dB/octave crossover sounded thick and mid bass heavy. Changing crossover frequency between 100Hz and 400Hz would change it slightly but not fix it. I even tried a natural run out for the 2202 and crossing the 2235Hs at 100Hz. Still not right. Shooting the system with my RTA confirmed this showing a broad bump centered between 200Hz. and 300Hz. I try to avoid EQ if at all possible, but I was thinking that a notch filter was in my system's future.

    Then Giskard came to the rescue again! He posted:

    http://www.lansingheritage.org/html/...de-monitor.htm

    If you read the last column of the second page it clearly addresses my problem. It was the mutual coupling of the woofers and the 2202! I scratched my head a bit, thought about getting a 5234A with the appropriate card in it, and then tried a fix with equipment that I have here. I used the low pass section of the Rane AC22 to feed the 2235Hs. The crossover frequency is around 275Hz. With a parallel output of my preamp I fed an Audioarts 12dB/octave crossover with it's high pass section set to around 275 Hz. Bingo!!! The asymmetrical slopes help create the needed notch and the steep slope on the 2235Hs helps prevent them from contributing too much mid bass.
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    Last edited by Mr. Widget; 09-13-2003 at 12:57 AM.

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    Administrator Mr. Widget's Avatar
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    The active setup described above feeding a pair of Hafler 9505s powering my project box 4355s is truly beyond my expectations. I expected the tonality to be good. I knew the transient response would be great. But with the physical modifications that I have made to the system the imaging is the best I have ever heard from a JBL system. It seams to be keeping up or even bettering my upstairs "audiophile system". It is even better than the 4430s I've heard, plus it has the extension in response that the 2405 allows. The drawing below shows my current setup along with my proposed one box solution. Originally I was using the 2397 horn, but now I am using a pair of my Westlake copies... smooth, natural, all of the dynamics of a horn system, but so smooth and natural! My other JBLs never sounded as good at low levels as they did at kick-in-the-pants levels. This system still sounds spectacular even at very low levels and because it is a 4355 it can play scary loud!
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    Last edited by Mr. Widget; 09-13-2003 at 01:00 AM.

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    Hi Mr W. I too am getting a little closer to my idea of a nice system. I posted the other week how I had been playing around with a pair of 4691B's I bought. Well this week I purchased 2 2220-h's and put them into some bins. It goes like this:

    One channel - VLF 2241-H 18" in 6.5 cuft tuned to 40hz
    - MB 2220-H 15" in 5 cuft eq'd to minimise response under 100 hz ( will build 1.5 cuft bin soon )
    - Mid 2123-H 10" in .5 cuft bin
    - HF Altec 909-16 and modified 511B horn
    Apart from the 2220-h in the 5 cuft bin ( ex 4331 cabinet ) the other drivers seem to be in their correct enclosures. Well I hooked it all up this afternoon, ( both channels ) and after tuning everything I listened to one of my favorite tracks. Harry Connick Jnr ( Star Turtle track 12 "Never Young" ) Wow I near shit my self, the slam of this system is incredible, the kick and snare drums were in the room with me, I swear !!!!!. The mid bass is better than any thing I have heard to date. The sound stage is so large and life like and the imagery is very precise. Apart from the HF section I think this system is getting close to the ancient Drew Daniels system with out the grunt. I have a total of 600 watts rms per cannel. Any way this system has given me some clear directions on where I'm going from here with it all.
    Mike.C
    Thanks for your help
    Regards Mike...................

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    Administrator Robh3606's Avatar
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    Thanks Mr.Widget

    For posting your impressions. Sounds like a killer set-up. I was wondering about the improved imaging. I would think it is at least partially related to the verticle array on the mids and highs. In the 4350 Tech Manual it states you should be at least 8 feet away. How are they near field now?? With my set-up using the 2344 and a verticle array I can get real close and not loose driver blend or imaging. I would guess these are the same way in spades. Are they toed in at all??

    Rob

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    Originally posted by Robh3606
    Thanks Mr.Widget

    Are they toed in at all??

    Rob
    He has a posted drawing here:

    http://www.audioheritage.org/vbullet...=6042#post6042

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    Administrator Robh3606's Avatar
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    He has a posted drawing here:


    Thanks!

    Rob

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    Administrator Mr. Widget's Avatar
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    Originally posted by Robh3606
    Thanks Mr.Widget

    For posting your impressions. Sounds like a killer set-up. I was wondering about the improved imaging. I would think it is at least partially related to the verticle array on the mids and highs. In the 4350 Tech Manual it states you should be at least 8 feet away. How are they near field now?? With my set-up using the 2344 and a verticle array I can get real close and not loose driver blend or imaging. I would guess these are the same way in spades. Are they toed in at all??

    Rob
    The only changes from the 4350/4355 that I made that would influence the imaging are the vertical alignment and the 2397/Westlake horn. One of the factors that determine image stability is an even polar response. This is one of the hallmarks of the 2397. The image stability of my 4355s is remarkable, but what I found so surprising was how well these speakers convey stage depth. Most JBL systems have a sound that is projected or is forward, these speakers while certainly not laid back, are not at all forward.

    I would like to make the comment, that while I am raving about a system utilizing a horn that I am also selling, the factory 2397 has all of these traits as well and in my listening tests in this system both horns sounded equally wonderful.

    As far as near field listening goes, the drivers are spread too far apart for that application. I am listening at a distance of 10' and there the pair of speakers form a cohesive sound stage.
    Last edited by Mr. Widget; 09-14-2003 at 12:34 PM.

  8. #8
    Administrator Robh3606's Avatar
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    "The only changes from the 4350/4355 that I made that would influence the imaging are the vertical alignment and the 2397/Westlake horn. One of the factors that determine image stability is an even polar response."

    Yes and the horizontal placement must effect the polar response especially through the crossover region. There has to lobbing somewhere.

    "As far as near field listening goes, the drivers are spread too far apart for that application."

    Yes my array has the same issue. I should have asked the question better. What I was curious about is could you hear the 4355's loose their cohessive sound stage as you got closer and can you get closer now before that happens??

    Rob

  9. #9
    Administrator Mr. Widget's Avatar
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    " Yes and the horizontal placement must effect the polar response especially through the crossover region. There has to lobbing somewhere."

    Yeah, I don't know why they went that route. The earliest 43XX had a vertical alignment. With the 4350/55 there are baffle real-estate issues, but as you know they chose to offset the 2405 on all of the later 43XX.

    I would love to test the near field for you, but unfortunately each "4355" is made up of three boxes plus one big ass horn sitting on top. The only way to test it would be to shrink the equilateral triangle to 8', then 6', then 4' and compare the results. I am not willing to go to that much trouble. .


    The thing is these speakers are so large that even sitting 10' away from them, the response of my non audio friends is a sarcastic, "Could you sit any closer to them?". This is probably prompted in part from this setup being in my HT where the screen and HT speakers are about 16' away. I set the 4355s up in a 10' equilateral triangle based on JBL's recommendation of an 8' minimum and the room I am in.

    If I move closer to one speaker with only one playing, I am not aware of the source being made up of a multiple of elements until about 6'-7' away.

    I think the bottom line is, to really get the most out of a speaker like this you must have a fairly large room. These speakers would probably not image worth a damn in a 12' by 14' room with all of the early reflections. The other thing, I don't know if you took a close look at the room drawing in the "Toe-in" thread, but most of the 10' high walls are covered with heavy velvet drapes.

  10. #10
    Administrator Robh3606's Avatar
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    If I move closer to one speaker with only one playing, I am not aware of the source being made up of a multiple of elements until about 6'-7' away.

    That what I was looking for! Thanks.


    I would love to test the near field for you, but unfortunately each "4355" is made up of three boxes plus one big ass horn sitting on top. The only way to test it would be to shrink the equilateral triangle to 8', then 6', then 4' and compare the results. I am not willing to go to that much trouble.

    Don't move thing!!! I am in a smaller room and about 7 feet away. I was curious about the walk up effect not a true nearfield set-up test. I would not move mine either but then again I got no place to go!!

    Thanks Rob
    Last edited by Robh3606; 09-14-2003 at 02:15 PM.

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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Inter-transducer Phasing?

    posted by Mr. Widget
    Shooting the system with my RTA confirmed ... a broad bump centered between 200Hz and 300Hz. ... my problem ... was the mutual coupling of the woofers and the 2202!
    Hey, Widget...

    I've been pondering this all week-end, since the Friday taste-test. (Nice! )

    If I'm deciphering your "3155 Modified" schematic correctly, you are running all transducers off the 3155 as Red input to Red transducer terminal post. Right? If so, they are all running JBL convention, negative polarity.

    I'm guessing your LF's (2235's) are also running JBL convention negative (Red input to Red terminal). So, the area of frequency overlap between the LF and the 2202 would be summed, not cancelled. That is not what JBL do with the 4343 and 4345.

    Both the 3143 and the 3145, when either biamped or four-way passive, run the LF negative (Red input to Red terminal post), and the "uppers" (MF, HF, UHF) all opposite polarity, positive (Red input to Black transducer terminal).

    I'm wondering if the troubling 200-300Hz "hump" could be obviated or lessened by reversing polarity between the transducer groups (i.e, LF and others), and simplifying your active crossover configuration.

    Last edited by boputnam; 09-14-2003 at 05:11 PM.
    bo

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    Smile Interesting Statement

    Hello Mr Widget

    Great to see your projects coming along so nicely.

    Your following statement has me very intrigued,

    Most JBL systems have a sound that is projected or is forward, these speakers while certainly not laid back, are not at all forward.
    It's actually been years since I heard a stock JBL "system" so I'm pretty well out of the loop for having hands-on experience with the 43xx line.

    Irregardless of that, I use JBL transducers for my own purposes.. My present quasi-MTM setup has extremely strong imaging capabilities ( side to side ) and most important ( for me ) - front to back depth . The thing is , all that front to back imaging is behind the enclosures front line or "upstage"( for the theatrically inclined ). This has kept me transfixed for more listening hours than I'm willing to admit to. In my (MTM) case, this imaging appears to be the combination of the round mouthed horn and the DC blocking caps I'm using ( among other system things ). In another thread I've talked about my recent foray into different caps. Well, all these newer caps I'm trying have moved the soundstage forward and/or collapased it quite a lot. Certainly not what I was after when I started my cap. exploration.

    In the case of your 435Xs' , to what, do you attribute that receeding soundstage ?

    regards <> Earl K
    Last edited by Earl K; 09-14-2003 at 06:31 PM.

  13. #13
    Administrator Mr. Widget's Avatar
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    " I'm wondering if the troubling 200-300Hz "hump" could be obviated or lessened by reversing polarity between the transducer groups (i.e, LF and others), and simplifying your active crossover configuration."

    In my original setting up of the system, flipping the polarity of the 2202 was one of the first things that I tried. While it did change the sound a bit, it didn't solve the problem. In any event the JBL article that discussed this coupling problem was talking about it in the 4343. A system with switched polarity. Personally, all things being equal, I would prefer to maintain system phase if possible.


    " In the case of your 435Xs' , to what, do you attribute that receeding soundstage ?"

    I am really happily surprised by the stage depth forward and backward as well as extending left and right beyond the physical spacing of the speakers. I have no concrete conclusions as to why it is working so well. As I said the polar response is probably responsible for the rock solid stability, but the overall stage depth was a happy surprise. I haven't tried to "time align" the system, so unless by some happy accident it just worked out, I wouldn't say that it is time or phase coherent. I am a firm believer in vertical alignment, I am sure that it helps, but I have heard many other systems that were in vertical alignment and they did not image as well.

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    R values for inductors

    Your custom horns look awesome and that's great that you were able to get plans for an updated version of the 3155 crossover. Do you know what the R values are for the inductors listed in the schematic? They all appear to be aircore inductors. If you knew the gauge of wire used the R could probably be estimated.

  15. #15
    Administrator Mr. Widget's Avatar
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    Thanks, I am using inductors throughout with minimum R values.

    For the 2.4 mH coil on the 2202 I am using a premium laminated iron core inductor to keep R low. For the three inductors on the 2441 I am using Goertz Alpha-Core flat ribbon coils, and for the two inductors on the 2405, they are moderately large gauge high purity air core coils.

    Off the top of my head I don't remember the gauges of the wire or ribbon used, but I did make sure all of the DCRs were quite low. None of the inductors were stock as I trimmed all of them to length to achieve the exact inductance specified.

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