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Thread: New Member: Advice on 4435 Crossover Biamp Setup with 5235 crossover

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    Junior Member Mtenn's Avatar
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    New Member: Advice on 4435 Crossover Biamp Setup with 5235 crossover

    First. I have been lurking on the forum for a while and have finally registered as I have found the contributors very well informed and helpful. Second I am an amateur audiophile and not very experienced with internal electronic concepts and components and their integration into equipment beyond knowing what things are called. With that being said, so you know what you are dealing with I have searched through prior posts but I am unable to ascertain a definitive answer to my quandary. I recently purchased a set of 4435 monitors. The set came with a JBL/Urei 5235 external dividing network and the proper 4430/4435 crossover cards. However, the speakers are missing the complete internal passive crossovers (61461 Dividing Network) crossover, jacks and biamp switch). It does still have the front panel Lpad level controls. I am fine Bi-amping these and I have several options for amplifiers both Tube and SS or a combination of both with Tubes for the HF and SS for the LF channels I will probably test several variations of amplifier setups before settling on the one I like best. My amplifier options include a set of Krell KMA 160 (SS 2 Monoblocks), a Krell KSA 80 (SS 1 stereo amp), a pair of SS Adcom 555II (SS 2 stereo amps) and soon to be delivered Manley Studio 440 (Tube 2 Monoblocks). I have some nice options. Regardless, without the passive crossover, which to the best of my understanding provides some degree of protection to the HF driver and also splits the frequency for the 2 LF and MF woofers, can somebody explain exactly how I can use the 5235 dividing network without the passive crossovers but still using the Lpads and also incorporate the proper speaker protection. I also understand that there may be some additional consideration to protect the Tube amplifier.

    How do I split the amplifier outputs to both the LF and MF drivers? I understand that the LF and MF driver have a crossover at at 100hz which must have been incorporated into the passive crossover which I dont have? The 5235 I assume will be taking care of the HF cutoff points for the LF and MF drivers.

    The 5235 Crossover does have the matching 4430/4435 cards but I also understand from review of the manual that there are 5 Filter DIP switches inside the unit which also may need to be adjusted. Are there any recommendations for what settings to use? It appears this is useful for high pass filtering of the LF drivers to remove subsonic signals below the drivers capability which for the 4435 woofer I believe is 30hz. There is also a DIP to add 6db of boost to the filter point (with a caution that it draws 4x increase in power from the amplifier to cutoff octave? Is it safe to use this or should I not bother with the boost?

    Additionally there are 2 notes in the 5235 manual 1) which state using a 50 watt resistor (2xto 3x the driver impedance) to shunt the reactive component of the driver below horn cutoff installed across the driver terminals and 2) a caution note when using Tube Amps and some SS amps wherein the user should install a 20W resistor (10x the drivers impedance) across the amplifier terminals.

    I assume I wouldn't need any of this if I still had the passive crossovers?

    Because I will directly wiring the Amplifier to the HF drivers the 5235 manual recommends inserting a capacitor in series. I believe the HF crossover frequency is 1000hz so according to the 5235 manual should I use an 40uf cap for the horn? or what size capacitor is recommended and does it matter which leg it is installed on (+ or -) and where in the chain (before or after the Lpads)? How do I incorporate the LPads into the circuit?

    Also, I believe I read somewhere that the balanced XLR pins on the 5235 are reversed and I may need to have a custom cable made or otherwise swap the pins so that it will work with the Manley Tube amplifier which has the option of either balanced or unbalanced inputs (my preference would be to use the balanced inputs for the Manley).

    So It looks to me like I need to

    1. Install a capacitor in series with the HF driver somewhere? What value?
    2. Install a resistor across the driver terminals to shunt the reactive component? What value?
    3. If using the Tube amp install (another?) resistor across the amplifiers outlet terminals? What value? and is there any degradation of sound doing this for the SS amp also whether it needs it or not?
    4. Install something to cutoff/crossover the frequencies between the LF and MF drivers.
    5. Split the signal to LF and MF drivers
    6. Reverse the XLR pins between both the Source and 5235 and also the 5235 and the Amplifiers? Seems strange that I would need to do this? is this correct?

    This is not as straightforward as I had hoped. Lastly, I would also strongly consider purchasing a used set (if I could locate them) or having a set of passive crossovers built to insert back in the chain which would also give me the additional option to drive the speakers directly (passively) without the 5235 Active crossover. I know this is a long post with many questions and thank you in advance for reading and responding for any input anyone could provide. I have uploaded the 5235 manual and 4435 spec sheet.

    Matt

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    Administrator Mr. Widget's Avatar
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    Welcome to the Lansing Heritage Forum!

    Iím guessing you bought these speakers: http://www.audioheritage.org/vbulletin/showthread.php?42016-Advice-sought-re-buying-a-pair-of-4435s-locally

    It sounds like you have a nice looking pair of speakers that will take a big more research and work to get them running properly. I havenít read the manuals on this crossover or for the 4430/4435 cards, but I believe JBL assumes you have the passive HF contouring part of the network which you will need to recreate. With some help, a bit of patience, and some experimentation you should be able to get there.


    Widget

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    Junior Member Mtenn's Avatar
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    You would appear to be correct. I anticipated this but was willing to take the risk as I like a challenge. By the time I am done I will probably end up spending more than finding a clean operational pair, but at least with these I know what I have and what I am getting into. The added bonus is that they did come with the 5235's with the correct cards which I understand are difficult to come by. Less concerned about Mint condition and original and more interested in sound reproduction and components. As they say in the collector car world, these will be "everyday drivers", not museum pieces. So, according to the other thread I will need to build/buy some passives. Now the question is who on this forum is the right person to talk with and engage for the task at hand or who can provide me with a good reliable engineer or tech who is up to the task.

    Thanks for info.

    Quote Originally Posted by Mr. Widget View Post
    Welcome to the Lansing Heritage Forum!

    Iím guessing you bought these speakers: http://www.audioheritage.org/vbulletin/showthread.php?42016-Advice-sought-re-buying-a-pair-of-4435s-locally

    It sounds like you have a nice looking pair of speakers that will take a big more research and work to get them running properly. I havenít read the manuals on this crossover or for the 4430/4435 cards, but I believe JBL assumes you have the passive HF contouring part of the network which you will need to recreate. With some help, a bit of patience, and some experimentation you should be able to get there.


    Widget

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    Junior Member Mtenn's Avatar
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    Can anybody provide a photo of the stock passive crossovers for the 4435 which shows the layout of the caps and resistors etc..

    Thank you,

    Matt

    Quote Originally Posted by Mtenn View Post
    You would appear to be correct. I anticipated this but was willing to take the risk as I like a challenge. By the time I am done I will probably end up spending more than finding a clean operational pair, but at least with these I know what I have and what I am getting into. The added bonus is that they did come with the 5235's with the correct cards which I understand are difficult to come by. Less concerned about Mint condition and original and more interested in sound reproduction and components. As they say in the collector car world, these will be "everyday drivers", not museum pieces. So, according to the other thread I will need to build/buy some passives. Now the question is who on this forum is the right person to talk with and engage for the task at hand or who can provide me with a good reliable engineer or tech who is up to the task.

    Thanks for info.

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    Administrator Robh3606's Avatar
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    Schematic is here: http://www.jblproservice.com/pdf/Stu...ies/4435LR.pdf

    Don't forget the 20uf just beyond the bi-amp switch it is a pole in the HF crossover. Just use a common sense layout you should be fine.


    Rob
    "I could be arguing in my spare time"

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Schematic is here: http://www.jblproservice.com/pdf/Stu...ies/4435LR.pdf

    Don't forget the 20uf just beyond the bi-amp switch it is a pole in the HF crossover. Just use a common sense layout you should be fine.
    The schematic doesn't list the DCR of the coils though so the results may not end up exactly to spec.

    I never followed the numerous 4430/4435 DIY threads that were so popular a decade or so back on this site and searching can be rather time consuming. Can anyone pop in with additional useful info? Didn't Zilch reverse engineer the 4430 networks?


    Widget

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    Administrator Robh3606's Avatar
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    The schematic doesn't list the DCR of the coils though so the results may not end up exactly to spec.
    Hello Widget

    L101 he can use one of the Erse super Q's. The only coil other used in the bi-amp set-up is L1 at .040 mH which is going to have a DCR in miliohms. The DCR for the coil is completely swamped by R201 the 30 ohm series pot.


    Rob
    "I could be arguing in my spare time"

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Hello Widget

    L101 he can use one of the Erse super Q's. The only coil other used in the bi-amp set-up is L1 at .040 mH which is going to have a DCR in miliohms. The DCR for the coil is completely swamped by R201 the 30 ohm series pot.


    Rob
    You make it sound so easy.


    Ok Matt, get your iron heated up!


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    Hi,

    the only Rdc value that really matters is that of the LPF inductor(s), 'cause it may impact the drivers' Qts. For my 4430 build I decided to keep it as low as possible (about 10 mOhms) and fine tune the box by the ports' length.

    Best regards!

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    Senior Member Ian Mackenzie's Avatar
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    [So It looks to me like I need to

    1. Install a capacitor in series with the HF driver somewhere? What value?
    2. Install a resistor across the driver terminals to shunt the reactive component? What value?
    3. If using the Tube amp install (another?) resistor across the amplifiers outlet terminals? What value? and is there any degradation of sound doing this for the SS amp also whether it needs it or not?
    4. Install something to cutoff/crossover the frequencies between the LF and MF drivers.
    5. Split the signal to LF and MF drivers
    6. Reverse the XLR pins between both the Source and 5235 and also the 5235 and the Amplifiers? Seems strange that I would need to do this? is this correct?



    Matt[/QUOTE]

    1. Install a capacitor in series with the HF driver somewhere? What value? Refer to the 4434 crossover schematic in biamp mode (safety capacitor incorporated).

    2. Install a resistor across the driver terminals to shunt the reactive component? What value? Not required with passive network and EQ in place.

    3. If using the Tube amp install (another?) resistor across the amplifiers outlet terminals? Not required. Use 8 ohm Tap. What value? and is there any degradation of sound doing this for the SS amp also whether it needs it or not? No

    4. Install something to cutoff/crossover the frequencies between the LF and MF drivers. Not required in bi amp mode.

    5. Split the signal to LF and MF drivers. The active crossover does this .

    6. Reverse the XLR pins between both the Source and 5235 and also the 5235 and the Amplifiers? Seems strange that I would need to do this? is this correct? Have a careful read on the 5235 manual. I would only use an unbalanced signal for your scenario.

    My recommendation is to build up the complete 4435 passive crossovers and assess the performance with one of your Krell power amps. Then decided of you want to bi-amp.

    The first reason is that JBL introduced bi amp for the the purposes of dynamic head room in such a design where a large amplifier clipping would likely destroy the HF diaphragm. The second reason is that at that point in time the 5235 was considered a SOA active crossover for professional applications.

    However what has surfaced now with high performance domestic audio equipment is that the 5235 in fact can degrade the fidelity of the audio signal passing through it. Yes that's right. In your scenario it would be easier and less complex to build the passive crossovers or get someone to help you or build them for you. The system has a 96 db 1 watt 1 metre sensitivity so it will go plenty loud with any of your power amps.

    Assuming you do this use high quality film/foil capacitors like Hovland and you will be swinging from the rafters with joy.
    Use a quality Iron core like the Ease for the woofer inductor and Solen or Jantzen perfect lay air core inductors for the high pass section. Use non inductive power resisters. An option is build a charge coupled crossover if you wished but that is more complex.
    Avoid attempting to install a bi-amp switch as that is degrade audio quality. Use copper straps of you want a switchable crossover for bi amp operation. All these parts can be sourced from Parts Express online

    The load impedance below 1000 hertz is a nominal 4 ohms. No problem for your Krell power amps.
    If you use the Manley tube mono blocks in full passive mode use the 4 ohm output tap assuming it has one.

    I recommend you also inspect the compression driver diaphragms.
    Buy new replacement JBL diaphragms if the current diaphragms are fatigued or damaged.

    If you wanted to improve the system further consider the purchase of Tad beryllium 2002 compression drivers.
    With due attention to the passive network you should obtain very good sound reproduction.

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