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Thread: STOP PRESS ..... Bombshell

  1. #31
    Senior Member Ian Mackenzie's Avatar
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    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.

    Ian
    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
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    Awesome project, thumbs up!!!

  3. #33
    Senior Member Ian Mackenzie's Avatar
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    Thanks

  4. #34
    Senior Member Ian Mackenzie's Avatar
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    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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    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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    Post

    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.

    Rob
    "I could be arguing in my spare time"

  7. #37
    Senior Member Ian Mackenzie's Avatar
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    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.

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