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Thread: Discussion Thread JBL 4343 to 4344 upgrade

  1. #256
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Ian Mackenzie
    Is this still your room setup?
    The curve we have been discussing as I understand it.
    Yes. We've shared a "coldie" here...
    And, sorta - this is obviously not the 52-5140 card - but the graphed comparison is clearly close...
    bo

    "Indeed, not!!"

  2. #257
    Administrator Mr. Widget's Avatar
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    When I was working on my 3155 project with Giskard's help, he posted this: http://www.audioheritage.org/vbullet...2&postcount=32

    It clearly shows the expected ~3dB bump from using a Butterworth filter. I suppose in the "real world" the curve may be quite different due to lack of output from the 2122H.

    It is interesting that the factory recommendation was for an 18dB Butterworth filter set at 290 Hz and the GT supplied voltage drive was for a 12dB Butterworth set at 320Hz.


    Widget

  3. #258
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    Yes it is interesting.


    Somewhere in a thread and I dont know where are some Spice generated voltage drives for the full set of filters into respective 8 ohm loads.

    That may shed more light on this discussion.

    I might look for that later on.

    If you have a copy of Vance Dickasons Cookbook on page 90 (4th edition) there is very interesting paragraph on the combined response o even order filters....

    In short when even order filters are combined the two sections sum flat when the level of both filters is 6 db down at the crossover point.

    Normally they are -3 db down at the crossover point for Butterworth filters when phase of high and low pass filters is coincident and the summation is +3db which is +6db gain at the crossover point (+3 minus -3 is 6 db ).

    As Dickason points out though if the in phase relationhip is relaxed and the crossover points are spread by a given facter of about 1.3 the filter will sum nearly flat when both high and low pass filter sections are -6db down at the crossover point.

    It would be interesting to measure this in practise.

    Ian

  4. #259
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Ian Mackenzie
    In short when even order filters are combined the two sections sum flat when the level of both filters is 6 db down at the crossover point.

    Normally they are -3 db down at the crossover point for Butterworth filters when phase of high and low pass filters is coincident and the summation is +3db which is +6db gain at the crossover point (+3 minus -3 is 6 db ).

    As Dickason points out though if the in phase relationhip is relaxed and the crossover points are spread by a given facter of about 1.3 the filter will sum nearly flat when both high and low pass filter sections are -6db down at the crossover point.

    It would be interesting to measure this in practise.
    Linkwitz-Riley filters are -6dB and the sum to a flat on axis output... here is an interesting interview of Siegfried Linkwitz in Stereophile. Look at the middle of this selected page for a discussion about this topic:

    http://www.stereophile.com/interviews/503/index3.html

    I am not sure how accurate DEQX is in it's emulation of L-R and Butterworth filters, but I have found that the L-R filters sound and measure better. When I have compared the same slope and frequency on Project Widget and measured them with CLIO.


    Widget

  5. #260
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    When Bo started talking about this I was wondering this they were LR , pure or modified Butterworth filters as I mention above fitted to the Bryston.
    If you were keen it would be interesting to test out these various types of filters on the fly with the DEQX plugged into Bo's system.

    At any rate it would seem the stock 3145 passive filters were almost entirely empirically tuned and probably with an eye for flat on axis response.

    I do like the approach of using Allpass (3rd order fiters) throughout the network.

    For those not familiar Allpass filter have an Allpass Phase characteristic. At a basic level what this refers to is the phase relationship (correlated and uncorrelated) of the highpass and low pass filter sections where phase is a function of the filter slope and Q. All odd order networks exhibit and high and low phass phase relationship that constantly 90 degress out of phase and this is termed phase quadrature (no The Who is not invent this term!).

    Because the outputs are 90 degrees out of phase at all frequencies the phase is said to be uncorrelated, and the filter outputs will sum together flat when the level of both filters is -3 db at the crossover point. The advantage of the 3rd order filter is that it sums with a flat magnitude response and it attenuates the output of the driver quickly in the stop band. Second and Fourth order LR filter also belong to the Allpass Group of filters, however as Mr Widget indicates, they are -6 db at the crossover point and also provide flat magnitude response.

    The distinction between the Third order Butterworth filter and the Second order LR filters as Allpass filters beyond this discussion becomes more complex when we start to look at what is termed Power Reponse.

    Power response refers to the off axis amplitude response in the crossover region when we are talking about the distinction crossover filters. Second order LR filters (even order) which sum flat when their high and low pass outputs are -6 at the crossover point do not have a flat power response but have a dip of -3 db at the crossover point. Odd order filters however which have an uncorrelated phase response on axis response and have a flat power response.

    The audible differences of these various filter types is depeds on the specific design of the loudspeaker and is open to wide debate.

  6. #261
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    Might be a good idea if this whole filter thinghad its own devoted thread with a link from here and from the 4345 Club thread.

    These sort of discussions are a myar and can drag on endlessly.

    I was about to roll out the self powered 2405 crossover thing being a Greg Timbers recommended 43XX modification and I would like to maintain continuity. If there is anything conclusive regards alternative active filters we can paste them back in here.

    Ian

  7. #262
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    Quote Originally Posted by boputnam
    Doods...

    I wish I had reason to travel to Reno...!!

    .
    Bo,

    Might be a useful opportunity for you and Ed to cross paths.

    I know Ed spends time in the Bay area, suggest you send Ed a pm as a courtesy.

    Ian

  8. #263
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Ian Mackenzie
    At any rate it would seem the stock 3145 passive filters were almost entirely empirically tuned and probably with an eye for flat on axis response.
    Giskard told me it was a very iterative process. They would start with a planned topology, listen, tweak, listen some more and tweak some more.
    bo

    "Indeed, not!!"

  9. #264
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    Yep,

    I got the same impression in that email about the box tuning..quite amazing. I impresses me that it was not done with a computer model. They obviously have great ears!

    Ian

  10. #265
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    Bo,

    Have you done any more comparions or A/b's ?

    I am assembling another project for my system so I won't have any feedback on the filters for 2-3 weeks

    Ian



    Quote Originally Posted by boputnam
    Giskard told me it was a very iterative process. They would start with a planned topology, listen, tweak, listen some more and tweak some more.

  11. #266
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    Some parts arrived so I should be able to start on this project soon.

    The bags of capacitors are polystyrene, hard to get but excellent for signal filters.

    Ian
    Attached Images Attached Images  

  12. #267
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    Re: Active Crossover / External Auricap Crossover/4344 Review (True Love)
    Hi, Ian. I got the active crossover back from Bo last Friday. I don't think he ever had a chance to audition it. I reinstalled it in my system on Sunday. I've got to tell you that after not listening to my 4344's (can I call them that now?) for the last two months, I am just utterly blown away. The system sounds so damn good. Just absolutely amazing. I think I had been making so many improvements over the last year I had started to take the system for granted. But after listening to my other JBL's for the past two months (Performance Series, 240Ti's, 120Ti's, 4412's) and then coming back to these, I realize just how special these are. Full, rich, articulate sound that can't be fully duplicated by the smaller boxes. It's like meeting up with an old love and remembering why you fell in love in the first place. I continue to be amazed. Thank you once again for the sharing your skill in the crossovers.

    Ed


    Nice to hear you so happy!

    Can you post us another picture please mate?

    Ian




    Quote Originally Posted by porschedpm
    I’ve been invited by Ian Mackenzie to publish an outline of the upgrades that I’ve made to convert my 4343’s to 4344 spec. And give my impressions of the resulting sound. This 2 ½ year upgrade process has culminated with the recent addition of custom built active and passive crossovers built specifically for my application by Ian. A summary of these upgrades are as follows. For more description and detail of these upgrades you’ll want to drill back through the 4343-to-4344 Upgrade Discussion thread.

    Upgrade 4343B drivers to 4344 spec.
    1. Replace LF 2231H drivers with 2235H
    2. Replace MF 2121H drivers with 2122H
    3. Replace HF 2420 compression driver with 2425J.

    Bi-Amp speakers:
    1. Pass Labs 250w/ch Class A amp for LF drivers
    2. Pass Labs 150w/ch Class A amp for MF-HF-UHF drivers
    3. Ashly XR-1001 2-way active crossover

    Upgrade stock passive crossovers:
    1. Outboard crossovers custom built specifically for 4344 application by Ian Mackenzie.
    2. Outboard crossover design completely bypasses the 4343’s Bi-Amp switch
    3. Outboard crossover design completely bypasses the 4343’s L-Pads

    Added internal Brace

    Upgraded active crossover:
    1. 2-way active crossover custom built specifically for 4344 application by Ian Mackenzie

    Evaluation of upgrades.
    1. When I upgraded from the 4343B to the 4344 drivers the changes were subtle. The low frequencies now seemed a little more detailed. The mids seemed to sound more natural and the highs seemed to be much more extended and natural (although I should add that some readers have said they prefer the aluminum diaphragm in the 2425H).

    2. Bi-amping the speakers added quite a bit of detail and authority to the low end. I had issues though that I attributed to the Ashly active crossover (or possibly the internal Bi-Amp switch or a combination of the two). What I gained in detail and authority on the low end, I gave up in terms of transparency and fullness of the music from the mids on up. The music sounded somewhat thin and undynamic. It seemed like the music was veiled. I described the sound to be as if there was something in between me and the speaker. I could still hear the music but it just wasn’t alive. I went back to a single amp set-up to verify it was the Ashly crossover/bi-amp switch causing this. I eventually decided that bi-amping was still the way to go and so went back to the bi-amped set up and started looking for a better quality active crossover.

    3. Adding in the custom built outboard passive crossovers, eliminating the internal bi-amp switch and L-pads, and adding the internal bracing was all done at the same time. While it would have been ideal to listen to the differences after each of these upgrades separately, it wasn’t practical to do so. But taken together, and probably due in most part to the new passive crossovers, they allowed the music to open up and be more full and transparent. The speakers sounded better than they ever had before. Even though there was still some slight veiling effect from the Ashly crossovers, it appeared to be minimized.

    4. It’s been a little over a month since I upgraded the active crossover to the custom active crossover Ian built specifically for my application. See pictures below active crossover. What you don't see is that the power supply is oused in a complete differen box and is hidden behind the equipment cabinet. Adding in this active crossover was another quantum leap forward. The veiling caused by the Ashly switch was now completely gone. And there was huge increase in detail from top to bottom. There was an overall new transparency and fullness to the music. The low end had a huge increase in control and authority of the bass. The mid through highs were now so crystal clear that any imbalance between drivers immediately stood out. It took me several attempts to get the balance amongst the drivers correct but once I did, the music became jaw-dropping good. It was detailed and dynamic. In fact it became hard to stop listening because it made all the old music I’d heard hundreds of times before, fresh and exciting again. I found subtle nuances I hadn’t noticed before because the detail just wasn’t there before. I still am amazed at how good it sounds when I turn on the music after being away for awhile. It’s nothing short of awesome. The music is now full, dynamic and detailed.

    It's taken over two years to get to this point but this latest upgrade has made the whole upgrade journey worth it. I can't over emphasize the importance using good quality crossovers. The quality of your crossovers should be at least equal to the quality of your other components. Really the easiest part was sourcing and installing the 4344 spec drivers. The most challenging part was upgrading the crossovers. You can use the stock 4343 crossover temporarily, but it was never designed for the 4344 drivers. And if you can find a 3145 network out there chances are it's time for it to be upgraded anyway. So invariably you'll be faced with having to custom make or if you have the time and expertise to do so. I had neither, so I was fortunate to have Ian custom make the crossovers for me. I asked Ian for his help because he understood the amps I was using and could match the quality of the crossover components to them. But there have been several LH threads written on building crossovers and there are several Forum members that have the ability to custom build networks. My deepest thanks go out to Ian for his patience, persistence and technical wizardry in building these phenomenal crossovers. It's hard for me to imagine how the music can sound any better. Although I have heard Ian's currently toying with the idea working on incorporating a small Pass DIY amp into an active crossover chassis to run the UHF-2405's. Sounds interesting.

  13. #268
    Senior Member porschedpm's Avatar
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    It'll take me a day or two but I'll take some pics and get them posted.

    Ed

  14. #269
    Administrator Mr. Widget's Avatar
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    Have you tried switching back and forth between the 2420s and the 2425s?
    If your 2420s were up to spec, I'd expect you'd find them a bit less aggressive sounding yet retaining all of the detail.


    Widget

  15. #270
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    Having spent counltess hours stuffing around with nine volt batteries I will now focus on this project. I have a populated board, heatsink and PS. All that is required is the 18 db slope filter.


    Hope to post some details soon, it should be fun.

    That why we are all here.

    Ian

    http://www.audioheritage.org/vbullet...&postcount=266

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