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Thread: 4-Way Active Crossover Options

  1. #31
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    I think I saw where Widget was using one, but on the woofer only. Found it.

    http://www.audioheritage.org/vbullet...l=1#post424651

    I have one and have played around with it (3.6), but didn't really try to compare to anything else. It's easy to use.

  2. #32
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    Yes, I am using it as a simple DSP and only on my Sub1500s... it is quite invisible in this application. I haven't limited its functionality in my system due to extensive listening tests and felt it wasn't up to snuff full range, I simply have no need for it beyond the application I am using it in.

    I suggest you try it out and let us know what you think.


    Widget

  3. #33
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    Not many posts here in recent times.

    Just wondering if anyone wants to share their active crossover experiences?

  4. #34
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    I have acquired propensities for long wordy posts so l will try and break up my recent experiences in single posts.

    To my unnecessarily structured way of thinking an active crossover is not necessarily the go to solution for musical enjoyment or your next loudspeaker project.

    An active crossover is not like a preamp or a source component.

    The basics cannot be assumed or overlooked.

    1. Itís a processor in that it divides the audio spectrum into bands that are delivered to specific individual loudspeaker drivers. Sometimes the crossover makes an approximation or a different crossover characteristic. Or your just guessing whatís required. The bearing on the significance of this requires investigation.

    2. The user needs a degree of understanding and familiarity with the said loudspeaker drivers, crossover network principles and how the said active crossover can be programmed or set up.
    Thatís often a void of unknown limitations towards the success of an effective active crossover in a system.

  5. #35
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    3. What goes in one end of the active crossover and out the other end is not entirely to be assumed a straight wire with unity gain. Stereophile Speak. Just like any preamp. Thereís differences is performance that are next put into context of your existing audio components.

    4. User error and false assumptions plays an influence in the psycho acoustics of what is perceived in the absence of proper measurements. For example some Pass labs XVR1 users l met in HK were adjusting the slopes and the Q of the low pass filters and making assessments on the performance of the drivers in an Everest DD67000. Their impression was the woofer diaphragm was too slow. It was simply louder than the horn. It try telling that to the hifi nerd. What they werenít aware of is that these adjustments increased the Gain of the low pass filter outputs. This lead to incorrect observations. So users can get lost in quest which on the face of it is ideally perfection.

    So in summary it can work very well but is best done in a controlled way. That generally means simpling the user interactions with the active crossovers.

  6. #36
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    Where to from here?

    Again applying more structured thinking the application of an active crossover can be classified into some applications. This then enables a more specific focus on the active crossover design and user interactions. Nelson Pass and myself spent a long time discussing the active crossover needs of various end users and we came up with two basic categories outside of Pro Sound applications. Greg Timbers was instrumental in providing technical insights to determine the precise requirements for JBL systems.

    1. Pre determined loudspeaker system. The plug in and go customer.

    The premise of this application is the loudspeaker has been previously designed and or built. The loudspeaker has built in active crossover capabilities and known active crossover settings. The active crossover can be thus implemented with program preset crossover settings with limited user requirements for system set up. The setup can get further defined of a limited range of level settings.

  7. #37
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    2. The project/diy louder system. The thinking cap customer.
    This application is more open ended in that the user has license for prescribing the loudspeaker system design meaning the component choices, enclosure
    requirements and owns the design of the crossover characteristics and system set up.
    Classification of the JBL driver range and horns can be used to define the frequency bandwidth of each filter and deliver guidance to the user. This simplifies the selection of crossover filters requirements.
    A selection chart can be drawn up much like in JBL enclosure kit to provide compatible loudspeakers drivers, horns and appropriate crossover characteristics.

  8. #38
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    Subject to further investigation the existing pre determined systems can be improved with active crossover approaches not available in passive crossover implications. This was applied to the JBLDD67000 where the helper woofer was actively driven by a dedicated power amplifier in a Tri amp arrangement. The active crossover filter arrangement was entirely different to the passive configuration. The results were a significant improvement over the stock bi amp mode and stock passive mode of operation. Greg Timbers originally designed the DD67000 as a Tri amp system but Harman limited the market offering to passive and bi amp. Much of this is about the skill of the loudspeaker designer.

    Improvements can be applied to other JBL systems including the legacy 43XX systems which go beyond what is possible with passive crossover implementations.

  9. #39
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    If your following these posts the structured approach to the application of active crossover very much makes the application of the active crossover easier implement successful. Take out the guest work, the unknown unknowns and assumptions and success is well within reach of the consumer or novice.

    Looking at the hardware choices the pre determined loudspeaker systems can be catered for with crossover cards much like the JBL5234/5235 and the JBL DX1. None of these units are now in production. The post author is currently engaged in a pre determined active crossover design which will be manufactured in limited quantities. A thinking cap customer version is also being designed.

    Looking at other options there are not many of any commercially available active crossovers specific pre set crossover characteristics for pre determined loudspeaker systems. JBL have the M2 covered via the Crown amplifier range only.

  10. #40
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    The limitation of all universal active crossovers including dsp digital and FIR digital crossovers is as stated above. You have to know the precise crossover settings and a detailed understanding of how to program the active crossover. There are no guarantees your crossover or you are going to get it right. Unless you have a lot of time and patience and so does your spouse the novelty can wear thin as the days, weeks and months and potentially years pass while you explore numerous adjustments. Not to mention test equipment. This can be like navigating a life boat through the solar system with only stars as your guide.

  11. #41
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    Some consumer loudspeaker manufacturers such as Dynaudio and Kef are spearheading full active loudspeakers. An active loudspeaker as a rule has all the power amplifiers built inside the loudspeaker.
    Itís keeps the loudspeaker cables from cluttering your room and looks tidy. But you have to give up your choice of power amplifier.

    The success of these systems is varied based on my own assessment but they are getting better.

    The inherent limitation of these systems is the 61/2 drivers used cannot project the same output of a floor standing JBL system without distortion. Such small drivers are low in efficiency and they waste power through heat. This results in power compression.

  12. #42
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    Quote Originally Posted by Ian Mackenzie View Post
    3. What goes in one end of the active crossover and out the other end is not entirely to be assumed a straight wire with unity gain. Stereophile Speak. Just like any preamp. Thereís differences is performance that are next put into context of your existing audio components.

    4. User error and false assumptions plays an influence in the psycho acoustics of what is perceived in the absence of proper measurements. For example some Pass labs XVR1 users l met in HK were adjusting the slopes and the Q of the low pass filters and making assessments on the performance of the drivers in an Everest DD67000. Their impression was the woofer diaphragm was too slow. It was simply louder than the horn. It try telling that to the hifi nerd. What they werenít aware of is that these adjustments increased the Gain of the low pass filter outputs. This lead to incorrect observations. So users can get lost in quest which on the face of it is ideally perfection.

    So in summary it can work very well but is best done in a controlled way. That generally means simpling the user interactions with the active crossovers.
    Looking more closely at post 34/35 above in more detail.

    One of the misconstrued notions about a digital universal active crossover or any universal active crossover is that its quick easy fix to diy loudspeaker projects.

    The novice is lad to believe he can quickly dial in the crossover for a flat response and I am done. Unfortunately thats not how it goes.

    Unless the user has detailed understanding of the compression driver and correct loading of the horn in use a satisfactory result beyond PA sound is unlikely.
    The best place to start is the closest passive crossover recommended from JBL or JBL designed system and simulate the passive crossover in SPICE.
    This analysis will provide valuable insights into an appropriate voltage drive for that driver and horn combination.

    If you are unfamiliar or don't have the skills to use this analysis you are far better off considering a pre determined loudspeaker design. JBL aren't stupid and they hold the key for diy active crossover users in their passive crossovers.

    The crossover options in a universal active crossover are really only appropriate for a theoretically perfect driver. That doesn't exist in practice. A typically horn and driver will start to reduce output at the lower edge of its lower pass band at 6-12 db per octave. Using a LR 24 db crossover will not provide the correct phase response in the crossover region because of the phase response of the horn and driver. The user will need to assess different crossover slopes and different crossover frequencies until a measured uniform 24 db acoustic slope is obtained. The level of practical skill and experience required is not a cake walk and is beyond most amateur loudspeaker builders. The optional vertical polar lobe response of a LR 24 db crossover is only obtainable with a phase alignment of the drivers at the crossover point os optimal. This must be measured and then an all pass filter applied to the low or high pass crossover output.

    If this exercise is done with your ears or you rely an flat response from your simple RTA it will not be a satisfactory result. Psycho acoustics will lead you down an endless rabbit hole long after the sun turns into a Black Hole. With some white board exercises and practical tutorials a novice can grasp the necessary principles and the process of obtaining an optional crossover. I plan to trial a webinar on this topic for interested diy loudspeaker builders. For those invested in obtaining a result as good or better than a commercial system a kick starter course on this topic is a must.

    Such a course might run for 6-10 weekly instalments and cover.

    Basic loudspeaker principles
    Loudspeaker measurement techniques
    Crossover design basics.
    Loudspeaker system design basics

    A practical tutorial sessions covering
    1. System driver selection
    2. Use of REW free measurement system with a calibrated mic
    3. Loudspeaker driver measurement on a baffle
    4. How to interpret loudspeaker measurements, amplitude, impedance, phase, distortion
    5. Acoustic crossover response measurements, amplitude and voltage drives
    6. Techniques for optimisation of crossover frequencies, phase transform, amplitude

    In a webinar attendees can ask live questions, share experiences and make a contribution to the discussion. This format of workshop is run at some catch ups in the diy audio scene and people get a lot put of it. If this interest you let me know.

  13. #43
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    To answer the previous, years old question I've been using an Ashly Protea 4.24D DSP as my living room stereo crossover for several years. It's software is easy to navigate and its feature set is ideal with the only real shortcoming being a lack of FIR filters. Not something that I've missed for my applications. I still prefer the sound of the venerable BSS FDS366 but I had a dozen of the Ashlys so inventory won out. The fan on the BSS also needs more remediation if used in a home setting. Both are gained staged for use with +4dbm levels so also need some gain staging attention when used with -10 hifi amps.

    In my experience DSP crossovers yield far better results than passive networks or analog electronic crossovers but then I have decades of training and experience in acoustic measurement and plenty of tools for measurement making. If you don't have those elements then it'll be an adventure and a potential disaster along the way but with a few exceptions it affords much greater chances for better sound.



    Quote Originally Posted by Ian Mackenzie View Post
    Not many posts here in recent times.

    Just wondering if anyone wants to share their active crossover experiences?

  14. #44
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    Great 👍 post.

    Your point on the fan is noteworthy.

    A while back a number of users of BSS units hit this fan noise problem and attempted various diy adventures to mitigate the noise. The same with some Crown power amps recommended for the M2.

    In a domestic situation what route you decide on is going to be a compromise in one way or another.
    If you goal is better sound then consider what that means to you and your budget. In the hifi genre side of the hobby as opposed to thrift or eBay purchases you generally get what you paid for.

    In my experience with the DD67000ís those users had the means to buy anything and they went analogue with Pass XVR1 universal crossover. But those crossovers are by no means straight forward to set up. They are sonically great once set up using measurements but not the last word in transparency according to Greg Timbers who made his own modifications including bypassing a number of electrolytic coupling capacitors in the signal path. Pass to this day refutes electrolytic coupling capacitors are an issue and points to active gain devices. Pass stopped manufacturing the XVR1 a while ago.

  15. #45
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    On the fan noise it really is a pain if you run your system a normal domestic levels.

    The quietest fans are around 30-40 db or so. But around 60db is going to annoy you after a while. To explain the drone of a fan masks the resolution of your expensive beryllium drivers. A lot of people want accuracy, a clean sound and so on but they underestimate the significance of noise impacting on those goals. If the noise floor of your system is not sufficiently low enough the noise will ride on top of the low distortion levels and the lowest level clean signals and your back to square one.

    A simple way to assess your system noise floor is to pause your source with the preamp volume at your normal listening level. Then carefully listen to the level of apparent background noise. This could include faint but perceivable mechanical or electrical buzz, your refrigerator, a sound like ocean surf or a hiss. When you un pause the source itís noise floor will also intrude.

    One solution is to put your equipment in an adjacent room.

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