Page 2 of 2 FirstFirst 12
Results 16 to 23 of 23

Thread: JBL 4345 3 -Way Version with JBL 2447

  1. #16
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,170
    Quote Originally Posted by Mannermusic View Post
    Last sentence! Been there, etc. It gets beyond the hobby stage. Thing is, after some years, everything becomes unstable - connections, electronics degrade . . . and you don't realize it at first, the human brain tends to adapt. So, KISS is best philosophy in the real world. And, a well developed passive system sounds plenty good, to these ears, at least. In fact, better in some ways. No magic. I like your "down the rabbit hole" comment.
    I run full active 4 way, bi-amp and passive set-up's. There is something to be said for the simplicity of a passive system but even they can have issues such as the dreaded Bi-amp switch and potentiometers. I have had more issues with the pot's in my old school L/R active crossovers. You really need to go into maintenance mode every couple of months to rotate and clean off the whippers as part of it. Plug and unplug connectors and so on.

    I would avoid using pot's in new crossovers and use stepped attenuation instead like L250/9800 as examples.

    I don't think that's big price to pay and with modern DSP it's not an issue no Pots! One thing for sure if you can take measurements good enough to do a passive crossover you can certainly use them to create DSP filters for an all active system.

    The ease of which you can create filters using DSP is impressive so you can try and make changes almost on the fly. Simply can't do that with passive networks so if experimentation is your thing DSP has distinct advantages.

    Either way active or passive it's all a fun time!

    Rob
    "I could be arguing in my spare time"

  2. #17
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Quote Originally Posted by Riley Casey View Post
    I'd be inclined to say just the opposite unless one is simply trying to recreate exactly an existing design as the R&D resources and skills required to iterate passive networks successfully are significantly larger than off the shelf DSP crossovers and a couple extra power amps but to each their own
    Each to their own
    You are right each to his own and l leave it to people to do as they wish.

    But your perspective suggests a plug and play approach (in the absence of the requisite R&D which l have at my disposal).

    The Facts
    Without an understanding of the individual native driver response and other characteristics on an actual baffle an attempt to do otherwise ( without R&D ) is unlikely to yield a satisfactory result.

    No loudspeaker driver has a perfect text book pass band frequency response or phase response. Placement of a driver on a defined loudspeaker baffle can make a significant difference to its native frequency response.

    The science
    The late Dr Linkwitz in his dsp active crossovers goes to great lengths to demonstrate that an accurate acoustic Linkwitz 4th or 2nd order filter from a driver is far from trivial with dsp. It’s in fact quite a complicated bit of design.

    The Pass Analogue Active filter approach
    What Nelson Pass explained to me was that he proved to his neighbour Dr Linkwitz that a close equivalent measured & subjective result could be obtained with a correctly designed analogue active system. Dr Linkwitz took some convincing but was so impressed with the Pass analogue active crossover that a kit has been made available at the Diyaudio.com shop for one of the Linkwitz loudspeaker systems.

    It should be noted and respected that Dr Linkwitz was a leading scientist in the field of loudspeaker crossovers and in a number of other audio areas. He was also a fastidious advocate of high quality sound reproduction.

    To my knowledge Neville Thiele’s patented TM crossover offers superior characteristics over all previous crossover types. However this is quite complex crossover to implement. Again it’s the drivers acoustic response we are referring to not the electrical voltage drive. Douglas Self has in a presentation devised analogue version of the TM crossover.

    Perspective
    If you are merely after a PA Wall of Sound or simply fun playing with an active crossover then of course none of the above matters too much. I think we have all been there. While such high powered sound systems may be impressive to an audience in an arena they are not designed for critical listening or monitoring in the recording or sound reproduction process.

    Sometimes it’s easy to loose sight of the perspective on specific or discrete applications when referring to such technologies. For example Texas Instruments don’t just make a general purpose audio chip these days. They offer chips for a variety of applications from portable lifestyle consumer audio, automotive applications, to consumer hifi and professional sound applications. The environments are all unique as are the specifications.

    https://bssaudio.com/en/site_element...ks-white-paper

    As l have said previously let your ears be the judge of what you hear and that is a personal thing. The real science behind what you hear is however is well defined.

  3. #18
    Senior Member
    Join Date
    Jan 2005
    Location
    Detroit
    Posts
    391
    Quote Originally Posted by Robh3606 View Post
    I run full active 4 way, bi-amp and passive set-up's. There is something to be said for the simplicity of a passive system but even they can have issues such as the dreaded Bi-amp switch and potentiometers. I have had more issues with the pot's in my old school L/R active crossovers. You really need to go into maintenance mode every couple of months to rotate and clean off the whippers as part of it. Plug and unplug connectors and so on.

    I would avoid using pot's in new crossovers and use stepped attenuation instead like L250/9800 as examples.

    I don't think that's big price to pay and with modern DSP it's not an issue no Pots! One thing for sure if you can take measurements good enough to do a passive crossover you can certainly use them to create DSP filters for an all active system.

    The ease of which you can create filters using DSP is impressive so you can try and make changes almost on the fly. Simply can't do that with passive networks so if experimentation is your thing DSP has distinct advantages.

    Either way active or passive it's all a fun time!

    Rob

    For what it's worth: Cleaning pots: You've got to take them apart and brush Deoxit directly on the resistor / wiper, etc. Then insert a suitable paper between the resistor and wiper and rotate. Repeat until no more gunk comes off. You're done and you will never have to do it again (most likely). Deoxit leaves a protective/lube film that is excellent. No, it is not easy.

  4. #19
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Rocinante
    Posts
    8,170
    Quote Originally Posted by Mannermusic View Post
    For what it's worth: Cleaning pots: You've got to take them apart and brush Deoxit directly on the resistor / wiper, etc. Then insert a suitable paper between the resistor and wiper and rotate. Repeat until no more gunk comes off. You're done and you will never have to do it again (most likely). Deoxit leaves a protective/lube film that is excellent. No, it is not easy.
    I have used Deoxit on loudspeaker pots and your right it works really well. I just spray it into the vents and give them a couple of turns. Must admit I have not taken them apart. Inside a speaker the only issue I would think would be a layer of oxidation on the contacts, can't imagine much actually getting inside them to gunk things up. They are usually well sealed less the vents. Do you find much in them when you open them up???

    Rob
    "I could be arguing in my spare time"

  5. #20
    Senior Member
    Join Date
    Jan 2005
    Location
    Detroit
    Posts
    391
    Quote Originally Posted by Robh3606 View Post
    I have used Deoxit on loudspeaker pots and your right it works really well. I just spray it into the vents and give them a couple of turns. Must admit I have not taken them apart. Inside a speaker the only issue I would think would be a layer of oxidation on the contacts, can't imagine much actually getting inside them to gunk things up. They are usually well sealed less the vents. Do you find much in them when you open them up???

    Rob
    The whole reason for getting in there is that external spraying makes a big mess inside; is "hit or miss" in terms of getting cleaner/lube on the resistor/wiper parts. A BRUSH DIRECTLY on those parts is the trick. No over-spray, etc. More like surgery. But, you've got to pry the cover tabs back, remove the covers (exposing the resistor/wiper) and then apply, wipe, apply, wipe, etc. You will see black gunk (oxidized mtl) on the paper as you wipe. GT says just R&R the damn things and be done. But I use them 'cause I am always tweaking. Anyway, to each his own.

  6. #21
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Quote Originally Posted by Mannermusic View Post
    Last sentence! Been there, etc. It gets beyond the hobby stage. Thing is, after some years, everything becomes unstable - connections, electronics degrade . . . and you don't realize it at first, the human brain tends to adapt. So, KISS is best philosophy in the real world. And, a well developed passive system sounds plenty good, to these ears, at least. In fact, better in some ways. No magic. I like your "down the rabbit hole" comment.

    Looking over my shoulder
    To the thousands of lurkers watching this thread try and interpret each post from your own perspective.

    Everyone has has their own level of hands on experience, insights and accumulated technical understanding of active crossovers.

    Context is a powerful thing in the face of ambiguity and rhetoric.
    Putting the above paragraph into context it’s about where your starting from, your goal, your expectations and what information you have and what input you can obtain. This can be a make or break situation on it an active loudspeaker system working out.

    In the real world
    In the real word at one extreme as Rob comments he manages to dial in a dsp crossover without too much difficulty. But that is an individual perspective and we all exist in a different station in life.

    Rob has years, decades of diy loudspeaker experience behind him and number of important skills he has picked up along the way. So Rob’s comments are valid in his situation. But if your curious with what this all about and new to the scene it’s not going to a walk up start. I have personally met people who spent a fortune on state of art jbl drivers and attempted an active system with a DEQX active crossover. They unfortunately ended up selling everything because they gave up trying to make it work. That’s right.

    The key ingredients
    But don’t let this put you off. Depending on exactly what you think your trying to achieve there can be merit in using an active crossover network. If you have or can obtain all the necessary data, expertise available and have the time to implement it correctly you were will succeed. A good starting point is to have a conversation with myself by going to the link below.

    The playing field
    Sometimes it’s about reaching an understanding of what’s possible and to de bunking some of the myths and over glorifications that seem to float around cyberspace about active loudspeaker systems.

    Most contemporary loudspeaker engineers- designers with real qualifications would prefer to implement their products as active systems. Small active monitors are popular in the home studio market. They are great for getting a much bigger sound than you would expect out of a small bookshelf sized enclosure. But not in the consumer hifi home audio market that has a long heritage of separate audio components. In getting their passive loudspeaker designs to work and in fact sound any good the loudspeaker engineer - designer has to do a lot more massaging with a passive crossover than you might think.

    What really goes on inside your loudspeakers?
    The passive crossover, the drivers and the enclosure are carefully adjusted to work as a “system” to achieve an acceptable subjective outcome. A passive loudspeaker system must incorporate compromises including losses of system sensitivity, bandwidth, system placement and power handling. We put up with it because it’s what we know and we accept. A full active system can remove some of these compromises. But designing an active system from scratch or converting a passive system into an active system is not a piece meal exercise.

    What you need to know when you remove the passive crossover
    Referring back to my earlier comments what the loudspeaker engineer-designer did with the passive crossover is now completely removed. What you don’t know is how the system would have been set up if it was an active system in the first place? Passive crossovers general work on the basis of attenuation of sounds across the audio spectrum. Active crossovers generally work by boosting and attenuation of sounds across the audio spectrum.They sometimes pull a few tricks too. These modifications to the tonal balance exist to make the loudspeaker subjectively acceptable to listen to. This is worked out not only with paper graphs but with many hours of listening in real listening rooms and a lot of trial and error error.

    Some myths debunked
    Your ears are not just listening to a snap shot or a slice of the loudspeaker sound output. Your ears are also listening to the impact of the loudspeaker distributing sound energy into the listening room. The significance of this arises when attempting to obtain the correct tonal balance from the loudspeaker system.

    It’s important to have the correct tonal balance at frequencies where your ear is particularly sensitive such as in the 2000 hertz region and at low and high frequency extremes for the system to sound tonally balanced. As mentioned above sound is being distributed into the listening room and does not just stop immediately after it arrives in the room. The sound decays according to the room acoustics. This is referred to the reverberation time and is measured by recording the time required for a sound to naturally attenuate to an inaudible level. Then arrival of the next sound will be masked if the first sound had not attenuated quickly enough.

    These aberrations, artefacts are always there whether you are consciously aware of it if not. Depending on the room acoustics these artefacts might be perceived at slap echo, flutter, booming and or ringing resonances. The source or cause of the artefacts exist whether the loudspeaker is in the room or not. An active crossover be it dsp or analogue cannot remove the source or cause of the artefacts your ear hears in the room. It can only modify the apparent loudness or intensity of the artefacts. Attempting to remove these offending sounds can cause a loss of important program information all together.

    What’s possible
    The loudspeaker engineer- designer has no control over these issues. But adjustments can be introduced in the loudspeaker system to reduce the apparent intensity of certain frequency regions sensitive to your ears in the listening room. The loudspeaker does not exist in an infinity large space in the listening room. The shape of the loudspeaker and the size of the baffle will influence the frequency response and the diffraction of sound from the loudspeaker baffle. To repeat its important to realise that EQ correction & phase adjustments can only influence or modify the apparent intensity of what your ear hears in the room. Not remove the source of the problem.

    Sometimes these tonal balance adjustments are permanent contours or they can be switched or variable adjustments with the passive crossover. It’s therefore a good idea to obtain some frequency response measurements of your passive loudspeaker system in your room before attempting to convert it to an active system.

    If this is all new to you its best you obtain an active crossover with pre determined characteristics for your particular passive loudspeakers.

  7. #22
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    See my new thread with re written series of posts which will be easier to follow Unfortunately l missed the edit time line due to other commitments. Mods please delete if you wish. Ian

  8. #23
    Senior Member
    Join Date
    Apr 2003
    Location
    Australia
    Posts
    7,942
    Quote Originally Posted by Robh3606 View Post
    I run full active 4 way, bi-amp and passive set-up's. There is something to be said for the simplicity of a passive system but even they can have issues such as the dreaded Bi-amp switch and potentiometers. I have had more issues with the pot's in my old school L/R active crossovers. You really need to go into maintenance mode every couple of months to rotate and clean off the whippers as part of it. Plug and unplug connectors and so on.

    I would avoid using pot's in new crossovers and use stepped attenuation instead like L250/9800 as examples.

    I don't think that's big price to pay and with modern DSP it's not an issue no Pots! One thing for sure if you can take measurements good enough to do a passive crossover you can certainly use them to create DSP filters for an all active system.

    The ease of which you can create filters using DSP is impressive so you can try and make changes almost on the fly. Simply can't do that with passive networks so if experimentation is your thing DSP has distinct advantages.

    Either way active or passive it's all a fun time!

    Rob

    Hi Rob,

    In your post concerning Pots are you referring to L pads in reference to the L250.

    On your active crossovers the cracking of a pot can be a sign that a dc leakage is a cross an electro coupling capacitor. Simply check if the pot wiper has an dc in the dc volt mv range of your multimeter. If there is replace the coupling capacitor. I recommend a 470 uF value to avoid low frequency distortion from the increased impedance of a small value electro capacitor.

    In JBL active crossovers they use low cost Alps pots or similar which are not really up to a lot of rotations. Greg Timbers said Harman electronics were not great.

    We use high quality from this manufacturer recommended by Pass Labs.

    http://precisionelectronics.com/file...4-Military.pdf

    When making fine level adjustments a rotary pot is intuitive. I sometimes use an 8 key dip switch for precision db level attenuation adjustments by shunting different fixed resistor across R2 in a R1 / R2 voltage divider with a low impedance buffer so low impedances can be used to reduce noise. The advantage of the approach is there is no break and make of the signal as with a switched attenuator for R1 / R2 in a voltage divider. It’s also far less costly than a stepped attenuator.

    With an 8 key dip switch for a few dollars you can have a good spread of fixed attenuation points such as this sequence.

    +2 db, 0 db, -0.75 db , -1.5 db, -3.0 db, -5 db , -8.0 db, off.

    It’s not a linear scale and these steps start out at perceivable changes in level and then more aggressive shifts in level over a defined range.

    I find an off position great setting up when measuring individual drivers.

    A separate trim pot or master fader can be used to adjust for a flat position with your Clio measurements. You can make precise repeatable adjustments across you sub, mid bass, horn and uhf outputs.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Jbl 2447 with aquapas dia?
    By greg32 in forum Lansing Product General Information
    Replies: 22
    Last Post: 10-08-2018, 02:30 AM
  2. 2380/2447
    By kawasakitech in forum Lansing Product Technical Help
    Replies: 9
    Last Post: 12-08-2013, 02:51 AM
  3. DSP/EQ/XO for 2x2226 and 2447/2352
    By baldrick in forum Lansing Product Technical Help
    Replies: 13
    Last Post: 02-22-2013, 06:49 AM
  4. 2446 or 2447
    By imtkjlu in forum Lansing Product DIY Forum
    Replies: 5
    Last Post: 03-24-2006, 04:07 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •