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

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  1. #1
    Junior Member cosmicjazz's Avatar
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    Sep 2019

    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:

    Compression horn driver: Radial horn:

    Super horn tweeter:

    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.

    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.

    Fostex EN3020, pics on HifiDo website, complete manual can be downloaded on Fostex website.

    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?

    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

    UREI 546

    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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    Apr 2003
    San Francisco
    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.


  3. #3
    Senior Member Ducatista47's Avatar
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    Jul 2005
    Peoria, Illinois
    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
    Senior Member RMC's Avatar
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    Feb 2017
    RE POST # 8

    Hi more 10,

    RE "Xlr also removes the possibility for ground loops if you make your own cables (connect screen only in one end)."

    The Neutrik 1/4" TRS I use on some gear does the same and I make my own cables. Ground loops avoidance isn't a particularity of XLRs. 1/4" TRS can do that too. Its more about how you connect your stuff than the connector itself. I generally prefer XLR but can easily live with 1/4".

    RE "Avoid Rane and Behringer. I have several dbxes, one labgruppen (swedish brand), and one Rane. I have used them all. ... My first one was a Behringer, it broke the first day I used it."

    Avoiding Behringer in general I can understand why since a number of folks have reported problems or reliability issues with different models, not everyone though. Never owned any Behringer but this changed today with a DEQ 24/96 and ECM 8000 mic for its RTA feature, picked-up this afternoon. As for avoiding Rane, I'm surprised at this, depending on model, you didn't mention which nor explain why so I'll assume its based on your assessment/use of one of their more recent XO models?

    Unfortunately, like many others Rane has changed over the years, DBX too, not necessarily for the better. Formerly built in the USA, Rane production was moved to low-cost Asia if I recall right and was purchased at some point by group(s) like In Music Brands. Sadly, not the same company as in the past. From a respected nice Pro gear one to a DJ/install maker now.

    Rane gear I got during the 90s is pretty good. Purchased a new 2/3 oct. GE 14 EQ in 1992 ($665.), AC 22 XO 1994 ($430.)and another AC 22 XO 1996 ($450.). These prices were below retail, add taxes to them. Wasn't cheap gear. But my experience with the three units is that they are well made, performing and reliable, using quality components.

    Very few audio manufacturers dared to systematically give very detailed specs with the more important tolerance figures for most of these product specs, like Rane did. They showed pretty nice tolerances. Over the years Rane has also provided the users with one of the best technical library. Never been cheap on tech info. Rane has been at the forefront of equipment connections issues you refer to, such as Sound system interconnections, grounding and shielding, Pin 1 problem, etc, and many more other interesting subjects.

    About 3-4 years ago I had an exchange of e-mails with Rane's Lead Factory Repair Technician regarding a question I had (not a problem) related to long-term reliability in a particular application and setup. I gave him each model/serial number along with the question. His reply was "With that type of equipment, no problem", then added some advice on doing it. From context I understood with other type Rane (more recent ones) his answer might have been different... Many people judge Rane for what it is now, and apply that across the board, instead of making the distinction with what Rane used to be.

    Rane AC 22 and GE 14 were manufactured for 10+ years, I think donkeys at those prices would not have survived in the Pro market for that long. I wouldn't have bought a second AC 22 two years after the first one either. Today I would still not change the Ranes I have for 23-27 years for some DBX 200 series stuff, since its mostly lower-cost China made equipment, not bad, but not great for the long run.

    Hope the above provides some additional insight or perspective on older Rane gear.

    Knowing what I know, never purchased a more recent Rane though, went instead for an Ashly XR-1001 crossover... Regards,


  5. #5
    Junior Member cosmicjazz's Avatar
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    Sep 2019
    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

  6. #6
    Junior Member cosmicjazz's Avatar
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    Sep 2019
    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.


    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.

  7. #7
    Administrator Mr. Widget's Avatar
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    Apr 2003
    San Francisco
    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.


  8. #8
    Senior Member Ian Mackenzie's Avatar
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    Apr 2003
    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.

  9. #9
    Senior Member
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    Aug 2010
    Jättendal (Giant Valley), Sweden
    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.

  10. #10
    Senior Member pos's Avatar
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    May 2007
    Paris, France
    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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