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Thread: STOP PRESS ..... Bombshell

  1. #31
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Quote Originally Posted by Ian Mackenzie View Post
    Hi All,

    I thought l would let you know where this is at.

    With the flux of time during Covid 19 there has been some pondering of matching needs to product features and benefits.

    With that in mind l am interested in your impressions and thoughts on the following:

    Option 1.
    A simple to use stereo 2 way universal analogue active crossover with continuously adjustable crossover points from 200-1500 hertz or similar.

    24 dB LR slopes, state variable with balanced/unbalanced inputs and outputs.
    Designed with premium TI audiophile chips and hi quality Wima capacitors and high quality pots.

    This will be an improved Ashly or other universal crossovers like the Rane.

    The idea is too keep it simple for those who want premium sound quality but arenít into taking the lid off and making fine adjustments.

    It wonít cost an arm and a leg because you will deal direct with the factory.

    Option 2.
    A stereo 2 way analogue active crossover that can be set up for specific Jbl systems using plug in cards.
    In concept like the DX1. It will also feature a sub out put with an optimal low pass filter.

    The crossover frequency, slopes ect are all set precisely for your particular Jbl systems.

    The design will use premium class A Jfet buffers and high headroom studio quality discrete op amps.
    Available in unbalanced as this crossover is for consumer hifi fanatics. Balanced connection and circuits add cost and complexity and frankly donít promise improvement in sound quality.
    All parts are of the highest quality. This product will be endorsed by Greg Timbers.

    Option 3.

    A Stereo 2 way or Tri amp analogue active crossover for the audio amateurs who enjoy building project loudspeakers of their own design.

    The design will feature premium class A buffers like option two but with adjustable plug in crossover cards for crossover points and slopes. Special purpose plug in cards will be made available for equalisation of low and high frequency drivers and phase alignment of low and mid frequency drivers.

    It will available with unbalanced or balanced connectors to a customers requirements.

    Option 3 will be sold with the Dayton Omni Loudspeaker measurement system.

    I have a reasonable inventory of popular JBL small and large format compression drivers and a growing collection of horns and woofers. So I can offer users with ball park crossover set up guidance.

    Why Analogue? Because itís simple with not a lot to learn and adjust. The focus is on doing the least damage to your precious analogue source. Vinyl is well and truly back and it sounds incredible with with a pristine signal path.

    I have some state of art test abs measurement equipment on order.

    Just a show of hands would be useful or other ideas.

    Option 2 fleshed out for now.

    Basic description
    A stereo two way crossover with preset plug in crossover cards with D connectors and front panel level controls.

    The user
    The product is primarily for users of premium consumer JBL and sort after JBL vintage loudspeakers and other loudspeakers configured for bi amp operation. Audio amateurs will find application with the design of their own project loudspeaker system.

    Cards will also be available for other consumer loudspeaker of popularity that have bi amp capability. Adjustable plug in cards will be made available including adjustable crossover frequency and crossover slopes.

    Specification - draft
    The front panel will have adjustment for both Low and High Levels for left and right loudspeakers, a power indicator.
    The level tim controls will have a range of +6 db to - 20 db.
    24 VDC power input jack from an external smps.
    The outputs and inputs for Left and Right Low and High channels outputs and a left, right and mixed mono sub output for external self powered subwoofers. A rear panel D link connector is specified. This will simplify fabrication and aid user setup and installation.

    The interior has plug in crossover cards which are installed by the factory on a main mother board.
    The plug-in crossover cards can be installed or changed by the user with a removable top panel.
    The std specification is up to 24 db LR but higher order filters can be achieved.
    The mother board will have capacity for additional plug-in card modules to expansion capability to a fully active two way loudspeaker system.
    This modules include LF Shelf to compensate for room boundaries, LF Boost, Room EQ Notch, LF phase shift (delay), Horn EQ with trim adjustment.
    The motherboard can be configured for mono three way operation (4 way with sub output)

    The interior has low voltage DC power supply.
    Internal are some adjustments to assist with earthing to minimise earth loops
    The product is packaged with a simple set up tool and a more advanced set up option available as an add on sale.
    The chassis is made of machined and anodised aluminium panels and is solidly constructed.
    Dimensions 18" x 4" x 15"
    Weight 15 Ibs.

    Specification and design
    Low Noise Linear System Jfets, Sparko Labs and Sonic Imagery discrete studio grade operational amplifier modules.
    Bourins and TDK potentiometers
    Wima polyropolyne capacitors
    Vishay resisters

    Noise - 100 db
    Distortion less than 0.002%
    Frequency response 20 - 20,000 hertz +-0.25 db

    Price POA based on a users requirements which will be unique in many cases. So you only buy what you need and can update and expand later.

  2. #32
    Senior Member
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    Sep 2008
    Germany / Hamburg
    Awesome project, thumbs up!!!

  3. #33
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003

  4. #34
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Btw the above was close to my original thinking early on.

    Okay this is the thing:

    Because there is a sub out there are two or three options.

    1. Unfiltered sub out for an external self powered sub with built in low pass crossover and power amp.
    2. Filtered low pass sub out for an external Diy sub with an external power amp.
    3. As per option 2 with a high pass crossover on the main Low output. This will enable a main Low band pass filter. For example a crossover at 100 hertz to a mid bass horn or configuration of a 4355 or 4345 to an active 3 way monitor.

    So the design is Transversal is its functionality.

    Different user groups want different things. But the common denominator is the loudspeaker or proposed loudspeaker the crossover is allied to. This type of Transversal configuration allows the user to Step - Up the functionality to a higher level of active operation in the evolution of his overall system.

    More options:
    4. On the high output channel there are additional options to incorporate programmable horn EQ to smooth the horn and or extend the horn response in the case of a CD design. This Step - Up in functionality removes the in-build high pass passive crossover and passive EQ.

    So there is application for multi way monitor users who want to Step - Up to 3 way active in a multi way monitor or Step to full active of a two way monitor.

    This sort of flexibility supports project loudspeaker users who plan to build out their own augmented two way system and helps overcome the limitations of high sensitivity two way designs.

    I havenít looked at it yet but a plug in module that offers an adjustable room curve is also possible.

    Offering a chassis that anything to anyone is needlessly complicated and confusing and ineffective. I may offer a mini version chassis of the above that is a plug in set and forget box for those who arenít the tweaking type of user.

    Because this is an open public forum there are limits to disclosure of the design.

    If anyone here has specific questions please pm.

    Thank you to those who offered feedback.

    Once Christmas is out of the way start on the detailed design.

  5. #35
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Attached are some of the voltage EQ and FR curves with the crossover.

    This follows the protocol of measure, test and learn.

    The user can obtain excellent imperial results with a measurement kit such as REW or the the Dayton kit.

    The crossoverís objective is to add as little or no noise or distortion as possible while being flexible in attaining the crossover transfer function as intended by the loudspeaker designer.

    In terms of economics yes there is a start up cost in terms of the crossover and an additional stereo power amp. However this cost is offset by:

    1. A superior dedicated high frequency amplifier.
    2. Flexibility of trialling different settings to evaluate the optimal performance.
    3. Removal of expensive passive crossover parts.
    4. Removal of complex trial and error design of passive crossover networks which can have
    unpredictable results due to interaction with the drivers impedance.
    5. More efficient use of power and superior diaphragm control resulting in lower distortion,
    improvements in resolving power and transient performance.

    Itís another step closer to the music according to feedback from trials. The user forgets about the equipment and becomes emotionally connected to their music collection.
    Attached Images Attached Images      

  6. #36
    Administrator Robh3606's Avatar
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    Apr 2003


    Hello Ian

    Looking at your first graph you seem to have some significant gain below 20Hz. Are you going to have a highpass filter there in actual use?? Anyone using a turntable could have some issues with any gain between 10 and 20 Hz not to mention anyone using reflex boxes in conjunction.

    "I could be arguing in my spare time"

  7. #37
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Hi Rob,

    Thatís a good point.

    In production these EQ curves will have limits put on them and bandwidth limiting filters to avoid excess sub sonic gain. That will all be worked out in product field trials.

  8. #38
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Hello everyone who has commented in this thread and the followers who are interested.

    An update

    Here in Down Under the state boarders are re opening on the 17th of December 2021. That signals the green light for the economy and logistical things important to business to start moving again. Melbourne has had longest set of lockdowns on the planet! So for that and some other reason am in the process of relocating to the Sunshine Coast in Queensland. Not far from Steve Irwin’s Australia Zoo.

    So l am interested to pick up on where l left off in this thread gleaning insights from anyone interested in a more up to date active crossover with origins based on the DX1.

    1. To kick off some new interest over a period of time there have been calls for SH DX1 Crossovers, and crossover plug in PCB’s.

    I would like to see a show of hands for general interest in meeting that need?

    Apologies for the detailed post below

    Put simply

    Are you in favour of one box can do all?

    Are you in favour of expanding on product capabilities as you go?

    For the Thinking Cap Customers do you want access to fine tuning things like bass response, CD horn EQ adjustment from the front panel?
    Or are you cool with tweaking your Diy loudspeaker with internal adjustments? See my comments below.

  9. #39
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Edited text and added a pdf diagram to make the post easier to understand

    This list of posts summarises the direction of the discussion at the time.

    I have a some questions?

    There is interest in Option 2 and or a Blend of Option 2 + 3. Great.

    A. My question is would you prefer a product that can be configured in a single chassis to provide a number of
    configurations and features at the outset with items 1,2,3 and 4? Version A Yes/No


    Would your prefer a simplified crossover as with items 1, 2 with the option to be able to expand the crossover
    capability with other additional chassis's that can be connected to provide 3 and 4? Version B Yes/No

    1. Stereo Bi amp
    2. Stereo Bi amp with stereo Sub outs (no sub crossover
    3. Stereo Tri amp with Sub outs and a crossover filter, a Low or Mid out with low and high pass crossover filters, and a high crossover filter. Adjustable filters available via internal adjustments.
    4. Options for low frequency shelf filters, driver EQ, Room Curves EQ, CD horn EQ, Sub sonic filter, driver Delay. Full active via internal adjustments.

    Human Connectivity.

    Are you comfortable with accessing the internal crossover plug card inside the chassis by taking the lid off? This is done with the DX1 crossover and the JBL 5234 and JBL 5235. Yes/No.


    Would you prefer to have a slot for example that you put the crossover cards in at the front or the rear. The Accuphase active crossovers took the approach. Yes/No

    Access to Adjustments item 4 - Advanced Adjustments for the invested thinking cap customer.


    Would you prefer to access the item 4 adjustments internally on optional plug in modules with labelled rotary trimmers or Dip switches or small knobs mounted on the PCB modules internally. By using a screw driver and a measurement system the adjustments can be set accurately.

    Lower cost
    Busy internally
    Optional plug in modules and can be acquired to customise a particular need. Buy as you need.
    Only accessible internally
    Requires removal of chassis lid
    Rotary trimmers and Dip switches - fiddly, potential for mistakes adjustment of wrong module.
    Requires a measurement system for accurate system adjustment.

    Note : Subject to space and design requirements we may be able to offer small knobs and small labels with a two or three tier PCB module to assist the user in making the adjustments

    NOTE : All items in item 4 with Version A are optional and are plug in modules where that are accessed internally with trimmers and dip switches and a small screw driver. Yes/No


    Would you prefer to have front panel access to all or some of these adjustments using knobs and switches in Version A - Single Chassis? Yes/No

    Busy front panel
    Easy to access the adjustments
    Costly to implement
    Higher upfront cost a item 4 is purchased with the single chassis.


    Would you prefer to have front panel access to all or some of these adjustments in an expansion chassis per Version B. Yes/No

    Buy the adjustments as a separate Chassis
    Front panel mounted adjustments in a single extension chassis - Version B
    Front panel accessable
    Can be adjusted by hand for convenience
    Requires a measurement system for accurate system adjustment.
    This would comprise of a number of front panel mounted knobs and switches and would be a permanent.

    Item 4 listing of Variable Adjustments for :

    Low frequency shelf filter below 100 hertz (single control Left and Right)
    Room EQ bump filters. below 300 hertz (3 controls per filter Left and Right per filter) Two bands
    CD horn EQ. (3 controls per filter Left and Right) One band
    Driver EQ. (3 controls per filter Left and Right). Two or three bands
    Driver Delay. (1 control per crossover output). Two or three bands

    Bare in mind the adjustments in item 4 really require a microphone measurement to make it worthwhile.
    This is not that difficult as it might seem with some understanding of the relevant techniques.

    There are limitations to making these adjustments by ear other than a basic bass and treble tone controls.
    You might switch in and out a low frequency filter to hear the difference. Once correctly set which can take a period of time with objective measurements and subjective assessment. The user generally won't make further adjustments.

    You might set it and leave it or need to make a numbers of changes with measurements over a period of time.
    Once the adjustments are made they are out of the way internally and you can acquire them when you need them.

    Or you might prefer the appearance of front panel visible controls and the convenience of front panel access. It will resemble a knob farm and cost more are to implement.

    If the customer is building a clone and one of the drivers is now discontinued we can provide technical support for either a modified passive network or a active network. The execution in the active design is much easier and less expensive if the customer has some spare power amplifiers he can utilise.

    The full active level is an advanced user scenario. I will be offering user support with demonstration webinars, technical tips, design examples.

    I am interested in your thoughts and opinions.
    Attached Images Attached Images

  10. #40
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    Aug 2017
    Reinventing the FDS360 ?

  11. #41
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Quote Originally Posted by Riley Casey View Post
    Reinventing the FDS360 ?
    Your showing your age...LOL.

    In some ways yes as to the functionality.

    I am not out to make a crossover that is a universal one size fits all or will be everything to everyone.

    The application or approach is different in that the active crossover is "tuned" precisely to a defined loudspeaker as the loudspeaker designer intended for the "Plug in and it goes" consumer customer. These are loudspeakers designed for bi amp operation. The consumer customer rarely if ever has the capability or the means to do this precisely. By focusing on one loudspeaker we can do that really well.

    Then if this customer becomes more curious and adventurous they can take over the controls of the aircraft as it were and have fun flying it.

    But careful what you wish for.

    This is the "Thinking Cap Customer". We given the a maps, charts and teach them how to navigate, take off and land the aircraft.

    They can progress in sophistication and complexity make the loudspeaker fully active.

    This can include modifying the frequency response to improve the subjective performance in their environment or to their own preferences or minimise an annoying acoustic anomaly.

    Or modify the loudspeaker design if they wish.

    This might included different compression drivers, woofers and horns etc. The original divers might not be available for a particular loudspeaker design the customer wants to clone. So we offer a precision crossover characteristic to enable the customer to use an alternative driver. We have the technical resources to do that. We can offer more sophisticated crossover characteristics to improve on the original legacy design.

    We can teach the customer how to make meaning acoustic measurements as part of the product offering. Once they pass this hurdle they will become more invested in their loudspeaker system and will be able to start making informed decisions around shaping the subjective results.

    There are some pitfalls to doing this so its less risky to be selective in the approach by giving the customer a product that goes beautifully at the outset rather than over complicate it and overwhelm them.

  12. #42
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    Edit. Bells and Whistles or Useful Tools

    ď4 Options for low frequency shelf filters, driver EQ, Room Curves EQ, CD horn EQ, Sub sonic filter, driver Delay. Full active via internal adjustments.Ē

    In looking at the adjustments in item 4 above you may ask are they bells and whistles or are they something l may need.

    This is the thing.

    An existing JBL loudspeaker System
    When you have a predetermined JBL loudspeaker system which is Bi amp ready and want to simply Biamp a number of the adjustments are taken care of for you within the overall design of internal passive crossover such as driver response shaping, horn equalisation.

    What we do.
    What we do is look at the existing passive crossover and engineer the active crossover characteristics from that by measurements of what the passive crossover is doing with the drivers connected. We look at the whole picture. Not just the crossover slopes and determine the best approach for Bi amp operation. This might include some mild shelf LF EQ at 35 hertz, a room resonance Low Q dip at at 290 hertz and superior active filter slopes on the woofer.

    We canít account for every possibility in your own listening room but we can provide you with some optional tools like a tool box.

    Your listening environment
    For example you might be stuck for space and you canít move the loudspeaker for the smoothest bass. Bass response in a domestic living space can be an involved subject. But we can help you assess your options and provide you with the most effective tools.

    Product Support
    After some discussion with us you buy a measurement mic and a USB interface so you can explore whatís happening with your JBL system with REW. You discover a bump in the response at 100-150 hertz and a sharp80 peak at 60 hertz.

    We recommend you move the loudspeaker back as close to the wall as post to move the Combe effects that cause the bumps further up to a higher frequency. You re measure the the bump is now at 80 hertz.

    You canít eliminate low frequency room interaction with EQ but you can reduce the issue with carefully use of EQ.

    We provide you with a set of Low Q EQ and High Q EQ plug in cards with instructions for installation and adjustment. You install the plug in modules and make adjustments by following a demonstration clip we provide you on a Zip drive which explains how to interpret your REW measurements and how to go about adjustment of your plug in modules. You do this on a Saturday afternoon and sit down to listen to your favourite tuned Saturday evening.

    The improvement
    You find the bass has more clarity and the system has better overall tonal balance. The listening experience is more enjoyable because you can focus on the music.

  13. #43
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    The. Thinking Cap Customer

    You own JBL 4435 and you have longed for a better power amp but itís really expensive.
    You read a review of a Quick Silver power amp but is rated at only 50+50 watts. On the forums you read about Bi amping the 4435 and start to think about your options.

    You contact us for advice on Bi amping the 4435.

    The Recommendation
    We discuss your situation with you, your budget and make a recommendation.

    You order a Stereo Biamp active crossover with a plug in crossover module for the 4435.
    You also order a kit of parts to assemble a charge coupled passive horn CD EQ for the bi radial horn.

    Getting it all together
    The crossover and the kit arrive. On a Zip drive we provide you with installation and set up instructions for the active crossover. We provide you with diagrams and instructions on assembly of the charge coupled kit and an installation guide.

    Your new Quicksilver power amp arrives.

    You refer to the installation guide for the active crossover and connect everything up.
    We give you support to make some fine adjustments and you obtain the correct balance with the woofer and the horn.

    The results
    You listen to some of your favourite tunes on Saturday night.
    The loudspeaker is far more revealing of fine details and the bass is firmer.
    You feel closer to music and start to rediscover your record collection.

  14. #44
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    These scenarios are typical of how loudspeaker owners approach using an active crossover. They give you an idea of how the active crossover and some optional modules and kits can work together to improve your listening experience.

  15. #45
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003


    Okay, I have some good news.

    After a lot thought in terms of the original idea for a configurable active crossover to suit a particular users needs I come up with a novel way of implementing the idea.

    In conventional passive and active crossovers we think of multiway systems in terms of is it a two way, three way or four way system?

    But suppose for a moment we stop and look at how a user starts to think about his particular system and what he would like to do next?

    Or how he might want to build a clone using some alternative drivers or horns. Then the question of the crossover network comes up?

    I am seeing more evolution in the use of alternative drivers where newer drivers are available or where a mid range cone driver is now N/A and how to sort out the passive crossover network. Or it might be a new woofer or a large format compression driver. Passive networks are complex to design and also really really expensive to assemble with high quality parts.

    Yes this is the problem. I see lots of requests on how to do it.

    So what this thing is going to do is allow a user to break down what's going on in his particular loudspeaker system to a level not easily done before in a controlled and precise way. The user is going to be able to experiment with it and do some tweaking. People like to tweak.

    I told Greg about it yesterday and this is his reply:

    "I really love the idea. You are basically talking about a monster DX-1. Unfortunately the DX1 was not set up for anything more than the crossover function. Your box is capable of so much more".

    A Monster DX1.

    So in terms of the next steps I am drafting up the overall design. The key has been to find a way of making it work in the practical sense so that only whats relevant is in use.

    I nearly fell of my chair my chair when I figured this out.

    Back in my days at uni I did some systems analysis and design for a potential career in IT. I ended improving and testing processes for banks. What they do is teach you how to look at systems and break down systems into different levels. What's on the face of it is a simple process.

    But under that process you have inputs, more actual processes, interactions with the user and outputs. Passive crossovers are often compromises and often an active crossover doesn't get it right because people don't really understand passive crossovers and how they interact with real drivers.

    Quite often the passive crossover design bends the response of the system to obtain a listenable outcome in the room.

    I have new engineer to assist in the design of the project. He has spent over four decades designing mixing consoles and Hifi equipment, has a number of patents and is currently consulting. The aim is to obtain some really good specifications like really low noise and distortion.

    If anyone has any requests on what they would like to do with their system post it here.

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