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Thread: My first active multi amp project, choices for electronic crossovers, advices please.

  1. #1
    Junior Member cosmicjazz's Avatar
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    My first active multi amp project, choices for electronic crossovers, advices please.

    Greetings to all music lovers and audio enthusiasts out there, I'm new on the Forum, looking forward to start to contribute, share the experience about the assemble process of my first active system, and also learn with more experienced friends.

    Here's a subject that I would like to learn more, I'm researching what will be the more appropriate electronic crossover for my project, in order to contextualize the project, here are the components that I'm purchasing...

    Source: Vinyl

    3 way loudspeakers, (Oh.. by the way, sorry for the components net be Altec / JBL)

    12" Woofer:
    https://www.fostexinternational.com/.../pdf/fw305.pdf

    Compression horn driver:
    http://www.loudspeakerdatabase.com/Fostex/D1405 Radial horn: https://www.fostex.jp/products/h400/

    Super horn tweeter:
    http://www.loudspeakerdatabase.com/Fostex/T925A


    Here's the thing about the electronic crossovers, that I will be grateful for the thoughts from more experienced audio friends.

    First, I'm considering just analog crossovers, as my main source is vinyl, do not make much sense for me, the phono signal be converted to digital and back to analog again, but appears that the downside is the difficult to solve the phase and time alignment issue with an analog one, in order to try to reduce this compromise, I'm thinking about align the voice coils manually.

    My considerations till now:

    Accuphase F-15L complete info on Accuphase link.
    http://www.accuphase.com/cat/f-15len.pdf

    Fostex EN3000, I have the manual in japanese only, specs are on the Audio Heritage website, better pictures, including from the inside, on Hifido website.
    https://www.hifido.co.jp/sold/14-84210-27250-00.html
    https://audio-heritage.jp/FOSTEX/etc/en3000.html

    Fostex EN3020, pics on HifiDo website, complete manual can be downloaded on Fostex website.
    https://www.hifido.co.jp/sold/11-627...-00.html?LNG=E
    https://www.fostexinternational.com/.../manuals.shtml

    Sony MU-C031 (this is not the ESPRIT one..), Pics on HiFido website, Can't find any info neither manual about this one, maybe it's a rare unit?
    https://www.hifido.co.jp/sold/02-13152-13313-00.html

    JBL M553 specs on the JBL Pro website, I'm sure you guys can provide very enlightening info about this one, as well the UREI 546
    http://www.jblpro.com/pages/electronics/mseries.htm

    UREI 546
    http://www.jblproservice.com/navigat...ectronics.html

    I'm still learning about this subject, as this will be my first project through the active multi amp route, appreciate the patience if some questions of mine do not make much sense...

    Anyway, i would like to understand more, the differences in design, about this crossovers"
    Fostex EN3000 it will provide a less quality signal? what you see on the inside pictures? let me know about the design...

    Fostex EN3020 appears to be much more quality device...

    Accuphase F-15L, It's all discrete, Accuphase build quality and selection of components, and reliability, according to my researches the prices are more or less the same when comparing to the other equipments listed here.

    Sony, this one is mystery hehehe

    JBL M553, maybe also the sweet spot in sound quality and reliability as well?

    UREI 546, now this is a interesting one, I have to say that I do not understood the concept and his functions, and intimidate me a little as well, too much stuff going on, I much prefer a more straight forward way to configure the crossovers, also, if in case of this unit need to e repaired, I'm afraid that can be a challenge for most of technicians where I live... but I'm interesting to know how this device works.

    Thanks everybody, looking forward about your thoughts, best regards to all.

  2. #2
    Administrator Mr. Widget's Avatar
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    There is so much to unpack here. I am not going to dig into each piece of gear you mention, but will give you my opinions based on my personal experience. My first active system was back in the late ‘70s, essentially a home made pair of L300s that I triamped. I then played around with numerous other active Dynaudio, SEAS, Focal etc. based systems of my own concocting... some quite good and others not so much.

    Obviously there were no digital options and DSPs were yet to be invented. Over the years I have used numerous pro audio and “audiophile” active crossovers. I have also played with passive line level multi-amp systems. These are similar to active systems but being passive you need to work with the input and output impedance of your associated gear to properly control the curves, turnover frequencies etc.

    In the mid 2000s I also used an early version of DEQX and enjoyed the incredible control and design flexibility afforded by going the digital route. Being able to really time align and customize your crossover frequencies and use minimum phase crossover slopes are all extremely powerful reasons to consider the digital approach.

    All that said, I have recently deployed a tri-amped system and as I worked on the speakers I considered the pros and cons of digital and analog and ultimately went with an analog approach. I am using very high end drivers and am using an exquisite analog crossover from Pass Labs. I have no regrets, the sound is really fabulous, but audio being what it is I traded one set of compromises for another.

    Ultimately you will need to decide what you require of your crossovers and be prepared to experiment for weeks. I urge you to get some test gear and familiarize yourself with it. Your ears will be the ultimate test, but the equipment makes tracking down phase errors, balance levels etc. much easier to sort out quickly. The road ahead is full of potholes, but the adventure itself is worth the effort, and with luck you’ll end up with a system you love.


    Widget

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    Senior Member Ducatista47's Avatar
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    cosmicjazz, love your Sun Ra avatar. My one piece of advice is to not take any single thing about this too seriously and to have fun. While I long ago figured out that listening to music instead of critically listening to reproduction equipment is where my passion lies, I do understand the allure of tinkering with gear. It actually runs in my family. I have a decent sounding classic large four-way system, but I gradually embraced the listening experience involving no crossovers at all.

    I learned to ignore the measurements that would tell me how imperfect such systems are and instead savor the absolutely perfect time alignment, phase, cohesion and integration of the approach I now use. Be it speakers or Stax headphones, I know all reproduction systems are imperfect and each has joys to offer. I also, with advancing age, enjoy knowing that I will never have to tinker or even think about my stereo rig again. It also feels great anytime I get to enjoy what is right about life instead of fighting what is wrong about it.

    One thing I can pass on is the rewards of deliberately maximizing the direct sound from speakers by physically blocking out the reflections and increasing the physical size of your personal auditory reception system. I will give just a hint here, but cup your hands around your ears, as when trying to hear something in the distance. Notice that the sound pressure coming directly from the speakers increases noticeably - by a lot, actually - while the opposite happens with the reflections. Only corner bass traps are needed to give lower frequencies a chance. Room treatment fuss and expense is minimized and significantly fewer watts are needed. You can easily modify a baseball cap to do this, but most will find it more elegant to modify your listening chair. It is like using audio binoculars and much greater detail is immediately heard, too. I mention this because while few would embrace this for everyday listening (their loss), it enhances the evaluation of the changes your tinkering hobby will produce.
    Information is not Knowledge; Knowledge is not Wisdom
    Too many audiophiles listen with their eyes instead of their ears


  4. #4
    Junior Member cosmicjazz's Avatar
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    Thanks for your thoughts friends, really appreciate.

    Well.. I think will go for what seams logical to me, about the crossovers choice, the Accuphase one appears to e very straight forward, they are sold for reasonable price, and the design build appears to be the more reliable one...

    OH yeah... Sun Ra was the man, space is the place bro

  5. #5
    Junior Member cosmicjazz's Avatar
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    Hey guys let me ask you,

    This days I was thinking about the possibility of use a tube integrated with pre-out on my active tri-amp project, in order to power the mids and highs.

    Example: http://www.luxman.com/asset/product/LX-380/gb2.jpg

    Send the "pre out" into the "pre amp in" into the active crossover, send the integrated "main in" with cable splitter into the mids ad highs on the crossover, and bi-wire the radial horns and super horn tweeters.

    A separated solid state amp goes into the crossover low, so I presume as the integrated "pre out" is plugged on the crossover, he will also control the solid state amp, right?

    Let me know what do you think, this will work?

    Many thanks, best regards.

  6. #6
    Administrator Mr. Widget's Avatar
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    First, I’d like to say I totally understand what Clark is getting at. A very simple “full range” speaker powered by a very simple system can be very magical and give you a clear window into the music. None that I have heard, even the high end examples using Fostex and Lowther drivers are terribly accurate from an objective frequency response standpoint, but in some ways that isn’t all that important as humans are very good at “auto correcting” frequency response anomalies.

    That said, if you want shimmering highs and bass impact in your gut, a multi-way system is required.

    On to your suggested pieces of gear. There is nothing wrong with going with an integrated amp with pre outs, but you may end up discovering the built in amp is inappropriate for your speaker design and then you will have all that amp sitting there unused in your system.

    Regarding the Accuphase crossover, I’d be concerned that since it requires different boards to change frequencies, you may find it difficult to get it to fit your system. Also, I find it is best to be able to massage the system by trying various frequencies and slopes to get the best integration between drivers. Ideally your crossover will allow you to create asymmetrical crossover points just in case that is needed to get the best integration.

    I think you should consider getting a digital crossover to use as a tool to explore your design and then decide if you want to stay digital or look at a high end analog crossover.


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  7. #7
    Senior Member Ian Mackenzie's Avatar
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    Mr Widget makes some excellent points.


    The Accuphase is a fine unit but the plug in boards are now difficult and expensive to obtain.

    I would be patient and continue your investigations further before acquisition of active crossover equipment. Passive loudspeaker are created by measurement and testing of drivers before any attempts are made to design a passive crossover. Do not be led to believe an active loudspeaker can be assembled without measurement of the loudspeaker drivers. The assumption is the loudspeaker mounted on the baffle has a linear response at least one octave either side of the crossover point.

    Every loudspeaker driver is different and must be measured in order to obtain the real benefits of active crossover principles. Optimal design of crossover between drivers is as much an art as it is a science. Trust your ears and understand what your measurements mean before making adjustments.

    For the purposes of this l would try the REW software down load (free). This is the start of your journey into active loudspeaker.

    In terms of the choices of analogue or digital l believe the KISS (keep it simple stupid) principle applies in diy audio.
    Attempting perfection without much knowledge or experience from the outset is crazy. Dsp (digital) processing of any kind has the potential to promise a lot. However the execution is not ideal despite the hype. A well executed passive crossover will often deliver a superior hi fidelity experience over a commercial/ pro dsp crossover or an analogue active crossover. A simple well executed analogue active crossover can deliver a superior hifi experience compared to a well executed passive crossover.

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    Choose crossover and amplifiers with xlr inputs and outputs. The increased voltage gives you better signal to noice ratio. Xlr also removes the possibility for ground loops if you make your own cables (connect screen only in one end).

    Analog filters

    Go for Linkwitz-Riley 24 db filters. If you place the drivers "phase linear" in you cabinet you will avoid comb filtering.

    An excellent and easy choice is DBX 234, new or second hand. Sound is very good. Upside is that it is easy to set up, frequencies are adjustable on a knob. Downside is that you cannot set the frequencies exactly.

    Avoid old stuff unless you have an interest in refurbishing things.

    Avoid Rane and Behringer.

    I have several dbxes, one labgruppen (swedish brand), and one Rane. I have used them all. I also have a Klark DN800, expecting to put in a lot of work into it changing frequencies and slopes. My first one was a Behringer, it broke the first day I used it.

    Digital filters

    IIR filters have the same filter characteristics to analog filters. Plus delay and EQ. I have one minidsp which I cannot recommend, low quality analog parts. The behringer filter has bad reputation. I also have an old Yamaha which I have never listenend to, but Yamaha has never made one bad product to my knowledge :-)

    FIR filters have also possiblity to EQ phase. But this is a can of worms since you end up wanting things not quite possible yet. Good price performance here is Dynacord 600, I have not heard it myself but have heard good opinions about it.
    Last edited by more10; 11-27-2019 at 02:51 AM. Reason: Added Behringer to analog part.

  9. #9
    Senior Member pos's Avatar
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    Quote Originally Posted by more10 View Post
    FIR filters have also possiblity to EQ phase. But this is a can of worms since you end up wanting things not quite possible yet.
    I would rephrase this as "this is a can of worms since you end up correcting things you probably should not"
    Not talking about phase per se here, but the desire some might have to correct any defect (magnitude or phase) based on a given measurement, including comb filtering effects, and even excess phase at times

    But in the end building a linear-phase acoustical crossover is actually easier than building a minimum-phase one, especially for 3 ways and up, because you don't have to match combined phase shifts betweens channels.

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    Listen to pos. He is the authority on digital filters.

    I am quite happy with my analog filters in my pretty conventional three way system. I have plans for digital filters though :-).

    One more thing though. You will have to take care of baffle step. You can do this as a regular filter between power amplifer and speaker. Or with an EQ.

  11. #11
    Senior Member Ian Mackenzie's Avatar
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    https://dbxpro.com/en/products/234

    I don't think the above crossover will provide enough flexibility for the starting point of a diy loudspeaker such as this.

    My recommendation is to do the hack work with a simple but effective dsp crossover. Work out the best crossover configuration, EQ etc and store that data. The mini dip will do or the new Dayton dsp crossover. Then arrange a hi end analogue active crossover for your excellent drivers using the data from the dsp crossover.

    I have owned the DBX 234. Its a cheap PA crossover compared to a Pass labs or First Watt crossovers and is unsuitable for a diy hifi project. I threw it in a skip bin for land fill. Of course its entirely up to you what end up with.

    Impressions of sound quality does varies from one continent (region) to another. I have learn't not to argue with what people like and dislike. I let them buy what they want and let them screw it up themselves.

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    Failing with the dbx 234 is quite an acomplishment considering it being a very simple filter to set up.

    Do not trust scotsmen advising to throw valuable property into landfills.

    The JBL filter is not good. I have one 553.

    The best EQ you can have is linear cone drivers/horns/bass boxes. Myself I currently use Pioneer PH50/PD50 horn/driver combo. Very flat down to 1K. No EQ needed. For midrange I have an Altec 414, also extremely flat. The bass is a different matter, needing some EQ. With linear drivers you can manage quite well with an analog filter.

    Analog filters are much cheaper than digital. The digital filter needs proper DACs for every channel. The analog filter needs only a proper OP-amp per channel.

    Investing your mone wisely is hard. Buying pro equipment you will only pay for functionality and quality. Pro guys can hear the bullshit. So reasonably priced pro equipment you will get what you pay for. So called hifi equipment can be grossly overpriced. Especially modern equipment. Unfortunately you cannot buy pro preamps, so hifi stuff will have to do. Turntables likewise and pickups.

    If I had 1000$ to spend, I would spend it on midrange drivers rather than a digital filter. Midrange is the most important part of any system since voices are in midrange. Our brain cares most about voices, so if you midrange is top quality, the treble and the bass can be as good as you can afford or your wife will allow. You can always find place for excellent midrange. Feeding fantastic signal to a mediocre midrange is waste of money. Feeding bad signal to excellent midrange is unbearable. You will hear any flaws you your filter with world class midrange.

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    Senior Member Ian Mackenzie's Avatar
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    Your funny.

    I bought the DBX to fill a gap after sending my Pass Labs diy active crossover to an LHS forum member who still has it. That was a long time ago. The difference was night and day in my system. If you open it up you will realise why. When l moved house it had to go. So it was true. I think the Ashly crossover is better on all counts and the Marchland too. The Bryston is very nice. The First Watt B4 is very nice. So l know what I’m talking about.

    As l said l don’t argue with people’s likes and dislikes. Based on wide experience assisting people with setting up their JBLs and systems you can lead a horse to water but you can’t make it drink it. By this l am referring the what goes on at home is largely uncontrolled. People will do what they do and often are none the wiser based on what they know and from others opinions. The way systems are set up and equipment is used becomes the norm. That becomes the listening experience and they accept it. In some instances they believe the loudspeaker has flaws because they are oblivious to problems with the environment, mistakes in the way the loudspeaker is set up and incorrect adjustment so they tweak and modify it to what they think is their liking.

    Even after sorting out the mistakes, adjusting equipment correctly, having the loudspeakers and listening position as the designer intended the people can revert back to how things were. So l take opinions on equipment with a grain of salt.

    I have however heard excellent results with the Fostex components in a simple 3 way home diy system. The crossover was passive and the hifi equipment was high quality. The owner spent a long time researching the best strategy and had the technical skills to implement his design.

    I was actually in Scotland last year. Lovely part of the world. They make impressive audio equipment (legendary). But l live down under when l am not travelling.

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    Thanks Ian

    Sorry for calling you a scotsman. I was a bit would up when I wrote that. I will start looking for the active crossovers you are recommending, knowing that there must be something better than my current dbx.

    And Cosmicjazz, it is a part of the hobby to try different equipment. If you buy second hand you will not lose that much when you sell old stuff.

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