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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.


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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


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    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

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    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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