Bi-Amping with Active Crossovers - Pros and Cons

Discussion in 'Audio Hardware' started by Soundgarden, Jan 9, 2022.

  1. 62caddy

    62caddy Forum Resident

    Location:
    PA
    Pros:

    Primarily useful for PA sound system arrays where single amplification is impractical and of course the few home speakers which are designed for external (active) crossover only in which case it is mandatory.

    Cons:

    Considerable added complexity & cost while requiring modifications to original speaker wiring for dubious audible benefits. Expertise level is often beyond the typical consumer to execute properly.

    In short, for those who insist on multi amplification, best to start with speakers specifically designed for it.
     
    SandAndGlass likes this.
  2. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Like just about everyone else in high end audio. Instead of taking the long way around and spending more money to do so, spend that money on better gear!

    People just can't seem to get that through their heads! When you bypass the internal crossovers you are bypassing the speaker deign itself.

    People want to take the load off their amplifiers. Amplifiers are full range because this is what their design specifications intended for them to do.

    You buy an amp based upon its ability to drive the bass. This accounts for 70% of the amps power. The other 25% for the midrange and 5% for the top end is the easy part.

    Buy an amp that is able to do the job. Spend the rest of the money on better speakers. This is all there is to it. Don't try to rethink the unnecessary.
     
  3. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I made my own PLLXO (Passive Line-Level X-Over) using a spreadsheet I found online.

    I made a little circuit board using my CNC router. The board is designed so each section can be either 1st or 2nd order. In my case, the bass (12") is 1st order, the satellites (Faital 3FE22 full-range) are 2nd order. The crossover is @ 300-Hz.

    I designed the board to be as flexible as possible by making oversized pads and rolls of holes on .1" (IIRC) increments. If I want to switch from Panasonic to KEMET to WIMA or vary series within any of these, I can easily do so, pretty much any part size out there will fit.

    I'm using inexpensive SMSL amplifiers powered by Mean Well power supplies. My bass drivers were only $30 each, IIRC, my Xmas gift from the wife. Their T/S parameters aren't particularly suited to conventional (ported or sealed) cabinets of a reasonable size, so I made my first-ever aperiodic cabinets for the 12" woofers. They hit 30-Hz with authority and do a better job reproducing bass than anything else I've had in my living room (that includes my old KEF 105's with 12" bass drivers, which come in 2nd). I really like the aperiodic sound and wish I had ignored the naysayers and not waited so long to try it.

    My entire system is designed to fit into our modest living room. So the "subs" go under the end tables (made of walnut, also by yours truly) and the full-range drivers clamp at the back of these same tables. So stereo "subs." I guess they call this sort of system FAST for Full-range and Sub Topology.

    It has been a few years now, I don't see myself going back to passive crossovers in my speakers. There are many advantages to biamping and few drawbacks, at least for me.


    [​IMG]

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    Last edited: Jan 10, 2022
    Soundgarden likes this.
  4. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    In this case it would vintage AR-3as, professionally modified for bi-amping by the same guy who just finished a masterful rebuild of them.
     
  5. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    I have to say that the amount of first-hand experience and detailed perspective being offered so far in this thread is amazing. I've got a busy work day going on here but will work through all this later. Thanks for all the input. Hopefully it's useful for others too.
     
  6. 62caddy

    62caddy Forum Resident

    Location:
    PA
    As well regarded the AR3as was (and still is), the fact is that loudspeaker technology has come a long way in the ~ 50 years it had been produced.

    This is a fairly low sensitivity model and plus its drivers were never designed to withstand large amounts of power which means dynamic range will be more limited and nothing is going to change that. That said, I find it difficult to imagine how much a serious improvement there is to be had by altering this 50 year old speaker for bi amplification.

    In other words, you can only squeeze the orange so much before it becomes a lot easier (and cost effective) to simply go to a new orange. :)
     
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  7. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    it is such a can of worms.
    active designs are best done by the manufacturer that knows the acoustic and electrical properties of the drivers being used including bandwidth, frequency response, impedance curve and distortion profiles.
    A DIY installation that guts the internal crossovers can be done but to be successful will require measurement tools, technical info about the drivers, a degree of technical skill and lots of trial and error dial in to achieve a pleasing voicing.
    There is much more to an internal crossover than xo frequency, xo slope order and driver level matching.
    Also ask yourself if a tweeter really needs its own amp.
     
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  8. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    So what is there beyond those things? Really curious.

    For me, no. One amp for bass and another for mids/tweets.

    In my case the AR-3as have a relatively simple passive crossover. I would likely have my amp builder talk to my speaker builder and build a custom active analog crossover. But I see a post above about PLLXOs which I'll admit I've been wondering about as an alternative to active crossovers.
     
  9. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    just to list a few-
    crossover frequency must be carefully picked for both the woofer and tweeter to optimize their bandwidth, help avoid frequency beaming and directionality and keep them out of their breakup frequencies where they sound rough.
    proper slopes and orders to help with the above.
    impedance flatteners to make them easier to drive and not waste amplifier power.
    notch or suppression filters if a driver has large peaks at certain frequencies or distortion breakup after its crossover frequency that the crossover alone cannot roll off fast enough.
    baffle step compensation to avoid reflected back midrange and treble from being out of balance louder than bass response.
    woofer high pass filter to increase SPL capability, reduce cabinet vibration and produce tighter, cleaner bass.

    many manufactirers slap in a simple crossover and call it a day. might be fine for some drivers but driver cone materials that can have superior sound may have challenges that require more complicated crossovers. in addition much testing is likely needed to voice and perfect the sound after the component values are selected.
     
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  10. Davey

    Davey NP: Luke Howard ~ All Of Us (2022)

    Location:
    SF Bay Area, USA
    One could argue though, that if it can't be done with a simple crossover, then maybe you should change the drivers for better results. Hard to fault either approach (or any of those in-between) if the results are good :)

    Historically I've been drawn to the simple first order crossover speakers, especially the series types, thinking Fritz and Xavian in modern times but did some of my own in the past. Oddly, I'm currently using speakers with pretty steep crossovers due to the ribbon tweeters, and they do sound good, maybe in spite of that, hard to say.
     
    Last edited: Jan 10, 2022
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  11. 62caddy

    62caddy Forum Resident

    Location:
    PA
    Few realize by the most amount of energy on loudspeaker engineering is spent on designing the crossover alone. Crossover design is extremely complex which must take into account a myriad of factors - right down to the cabinet volume.
     
  12. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    If I had super complicated speaker crossovers I'd be much more leery of doing this. If I didn't have two experts to help me do a top-notch custom job I wouldn't do this at all. I'm not going to buy an off-the-shelf product. I'm also not going to by a digital product to stick in between all my all analog vintage components.

    I think I'm likely past the point of being intellectually invested in figuring this out. Maybe that after it's all done I go right back to a simple setup and sell the extra gear. Can't imagine I'm going to stick with bi-amping if its benefits aren't clearly apparent.
     
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  13. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I was never really completely satisfied with any of my passive crossover efforts on my earlier speakers. I'd listen to a Fried speaker with a 1st order series crossover and just be enthralled, but never got there with my own stuff.

    As a result, I was always tweaking.

    One of these days I'm going to do an Altec system with horns and 15" bottoms, and I'll probably give passive a go again. Or maybe I should just check myself in now.
     
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  14. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    I'll admit I've been sheepish to ask about this and why no one (until you) suggested a passive line-level analog crossover. I figured maybe there was a reason they needed to be active. I'm sure this will lead to a healthy debate about what works best - but for what are likely obvious reasons I'd prefer passive here IF it can get the job done.

    So pros and cons of going active vs. passive for a line-level analog crossover???
     
  15. Davey

    Davey NP: Luke Howard ~ All Of Us (2022)

    Location:
    SF Bay Area, USA
    I did talk some about it in the second reply, but the main limitation is just the order of the crossover, and the size of the inductors needed if you go beyond first order due to the high impedances. With active circuitry, you effectively simulate the inductors. You can cascade simple RC networks for higher order filters, but they get very lossy.
     
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  16. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Yes, it is. I find that the AR3 and similar speakers from that era, were not versatile like more modern speaker designs are. My observations back then tended to be that different speakers did different things well and other things, not so much.

    Speakers that were voiced for certain types of music sounded great that that type of music and totally lackluster with other types of music.

    This is why I never choose to own any of them personally, opting for my Altec’s. I just couldn't find the right pair that I could live with.

    Compared to today, my audio knowledge was in its infancy. My A7's were nowhere as adapted to home use as my present A7's are. Using powerful SS amps, not tubes, not having a sub or super-tweeter, using stock factory crossovers. Still, they were dynamic and alive. Though not as highly refined, they worked better across the music spectrum.

    I think this is true, sometimes more in theory than actual practice. In my opinion, most speakers had crossovers that had less than stellar performance. Even those who could design a good crossover, didn't necessarily make the final cut, due to cost constraints.

    Crossover networks were that invisible and overlooked critical piece of technology that was virtually ignored by practically everyone. Money was spent on drivers and better looking cabinets, not on crossovers, which were deemed to be a necessary evil at best, when it came down to over budget allocation.

    When someone was paying a complement to a speaker, who ever heard anyone say "they sure have nice crossovers"? Never happened.

    Sure. You can improve the sound of vintage (and modern) speakers by crossover upgrades, sometimes quite a bit, but if the drivers and overall design and build are not what they could or should be, then there is a limit to where someone might wish to allocate their resources.
     
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  17. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    I'll look back for that. And that makes sense. That said... @Phil Thien writes this:

    "I made a little circuit board using my CNC router. The board is designed so each section can be either 1st or 2nd order. In my case, the bass (12") is 1st order, the satellites (Faital 3FE22 full-range) are 2nd order. The crossover is @ 300-Hz."
     
  18. Gibsonian

    Gibsonian Forum Resident

    Location:
    Iowa, USA
    Most things in this world can be improved. ALK company has improved many a speaker with their passive crossover designs, many of which are very unlike what they are replacing. Ask their customers.

    One thing is for sure, if you don't have the knowledge and tools, best leave it to someone who has or leave it alone. Likely will make things worse.
     
  19. motorstereo

    motorstereo Forum Resident

    Location:
    Ct.
    I can only wish I had this set of "nice crossovers" in my sda's.
    [​IMG]
     
  20. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Holy cow. I didn't even know crossovers like existed. At least not outside of truly exotic applications. Although maybe this is just that...
     
  21. Gibsonian

    Gibsonian Forum Resident

    Location:
    Iowa, USA
    [​IMG]

    Here's a pic of a line level passive crossover from Marchand. Note the big ferrite core inductors. You can buy these in just about any slope or frequency I believe. Never heard one, but I'd like to.
     
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  22. motorstereo

    motorstereo Forum Resident

    Location:
    Ct.
    Yes it's one off over the top custom by a very talented individual. He also does custom crossovers to a lesser degree but even those are fine works of art and sadly beyond my pay grade.
     
  23. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    So here's an observation:

    A lot of people feel a lot of different ways about bi-amping. But no one thinks it's child's play. You can't just swap components in and out the way you can with amps and speakers. Bi-amping - in hifi applications at least - needs to be done very well to be worthwhile.

    Two corollaries: 1) It's not easy to bi-amp well!; and 2) Doing it well most likely requires an iterative process of listen, adjust, repeat.
     
  24. CoolJazz

    CoolJazz Forum Resident

    Location:
    Eastern Tennessee
    The big point to know about a passive is that the corner frequency will change with the load. So change the amp with a different input impedance and suddenly you have new crossover frequency.

    CJ
     
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  25. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    How does this work when you're bi-amping two different amps with different input impedances?
     

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