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Thread: Active vs passive XO?

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    Senior Member baldrick's Avatar
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    Active vs passive XO?

    What would be the best solution for XO for a pair of Altec A700/A7, Altec 1632a active crossover or N1285-8b passive?

    The active soultion would be powerd by 9442 on the horns and 9444 on the woofer, the passive solution would probably be only an Altec 9444.
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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    I personally don't have experience with the crossovers you mention, but otherwise my experience tells me you are better going active whenever you can.

    Biamping yields more control, and, that Altec 1632A looks pretty damned smart.
    bo

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by boputnam View Post
    I personally don't have experience with the crossovers you mention, but otherwise my experience tells me you are better going active whenever you can.
    Yep... no experience with that crossover and in general I also really like going active since you get better control of the woofer, have the option to go with a sweet sounding smaller amp up top, and you get more control of the system over all.

    That said, I am in the process of trying out some passive crossovers for my own active systems. The overall simplicity appeals to me as well as I really can't afford the best crossovers and amps that I have heard make these speakers sound their best... less gear means I can use fewer but higher quality pieces.


    Widget

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    Senior Member Loren42's Avatar
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    Quote Originally Posted by baldrick View Post
    What would be the best solution for XO for a pair of Altec A700/A7, Altec 1632a active crossover or N1285-8b passive?

    The active soultion would be powerd by 9442 on the horns and 9444 on the woofer, the passive solution would probably be only an Altec 9444.
    Hi, Baldrick!!!

    There is no comparison. Even though I do not know the crossovers you cite, active crossovers have a number of advantages over passive designs, hands down:
    • Phase coherence
    • Higher damping factors (amps directly coupled to driver)
    • Impervious to driver impedance changes or temperature changes
    • Lower intermodulation distortion
    • Greater headroom (high frequency signals are not coupled to low frequency signals)
    • No passive inductors or other components operating at low impeadences contributing to losses and non-linearity
    • Crossover frequency are unaffected by reactance of the driver
    • No reaction between crossover and drivers
    • No padding of the drivers required to match SPLs between drivers
    • Ability to arbitrarily adjust crossover points and slopes (you can dial in the system without opening up the cabinet or swapping components)
    • Some active crossovers allow you to adjust for phase time alignment between drivers
    In my mind there is absolutely no reason to consider a passive crossover if you have the means and will to go active.

    The exception to that might be for portability of the cabinet if it is to be moved from place to place and use different amplifiers to to drive it. You also have to consider that the number of wires you run to the cabinet will be greater for bi-amped or tri-amped systems, which may be a nuisance for sound reinforcement work where you need to lug extra cables and equipment around.

    However, for home applications or permanent installations, active crossovers offer advantages even the best designed passive crossovers can not match.

    As a final note, make sure that the amplifiers you use have the same phase relationship or make sure you account for this. Some amps invert the input and some do not. The best setup uses all the same types of amps so that the phase and delays are consistent across the board. For my home tri-amped system I use a Harmon Kardan AVR 630 receiver as the amplifiers (contains six 75 Watt amps in one chassis) with the receiver set in the Direct In 8-Channel mode. This bypasses the front end of the receiver and drives the signals directly to the power amd. I paid $100 for this receiver on eBay last month. Cheap! I use an Ashly XR2001 crossover, which cost me $200. This is less money than what I would have spent making two 3-way passive crossovers!

    Loren

  5. #5
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Loren42 View Post
    In my mind there is absolutely no reason to consider a passive crossover if you have the means and will to go active.

    However, for home applications or permanent installations, active crossovers offer advantages even the best designed passive crossovers can not match.
    Two initial points:

    1). I have been using active systems in home stereo systems since 1980 and in home theater systems since 1998.

    2). There are quite a few threads on this topic.

    Several reasons not to go active:

    First of all, if you start messing around with active crossovers, you have just become a speaker designer. Regardless of how much info you have, you will likely be inadvertently changing the actual crossover frequencies and slopes from those in the original passive design to at least an audible degree. If you don't have proper measurement equipment and know how to use it you will be chasing your tail for quite some time getting the crossovers set correctly and the various amps properly balanced. I am not saying that it is impossible to do without test gear, but to match the original sound of the speaker you may spend weeks screwing around adding a couple of dB here or there one day and changing it back the next...

    Lets assume you have the correct test gear, knowledge, and or the ears to dial it in... then there is the issue of system EQ. Most contemporary systems have built in passive EQ that will be difficult to properly match without the right gear. (If you are dealing with a rather simple vintage system or a DIY masterpiece, then "fixing" the system is entirely up to you anyway.)

    OK, so you are capable of balancing and adjusting the system to your desired flavor. As many have discovered as soon as you add the complexity of outboard crossovers, equalizers, and multiple amps, the likelihood of grounding issues grows significantly and can be a real pain to fix.

    Then there is sensitivity... if you use a high sensitivity compression driver and amp in an active system you will very likely hear background noise... it is almost impossible not to in a home setting which is quiet and you only sit a few meters away from the drivers. If you have only average quality gear or don't have gear that works well together allowing you to properly adjust the gain structure the noise can be quite distracting.

    Which crossover to buy? Most are not particularly wonderful... the really good ones are quite pricy. If you use a quality two-channel preamp and want to transparently preserve it's sound quality, you must use a crossover of similar quality. This leaves you with very few options. The easily obtained pro crossovers are all pretty bad sounding. If you are using a DSP based multi-channel processor or AVR, ignore this part, but if you are trying to approach the sound quality of a top flight passive network with Pass Labs, Levinson, or similar high quality stereo gear... consider moving into active networks cautiously.

    Now, let's say your thinking, "Widget's being too picky... this Rane or Ashly crossover sounds damned fine with my AVR."

    I can go along with that... that is exactly how my last HT setup was run... but why go to the expense of extra amps, crossovers, equalizers, etc. in a system that really won't sound better for it? I did it because my DIY speakers had no networks and I wanted maximum SPL... you may too. However, if you have decent speakers with well engineered networks, the law of diminishing returns is solidly against you... along with the other items I mentioned above.

    So while I have used many active systems... and a number of passives, there are plenty of reasons to consider a passive system, even if you have the means.


    Widget

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    Active vs. passive is an issue I have been wrestling with as well.
    Even though you've spelled it all out beautifully here ... I'm more confused now than I was before

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    Senior Member Loren42's Avatar
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    While I respect your opinion, the original poster was deciding between two stock crossover systems specifically designed for this speaker system. The Altec A700 was built with these two systems in mind.

    Either one will do nicely, but the active system would be a better pick for the reasons I cited in my post.

    I think there is a lot of trepidation about going active, but it is not voodoo or magic, just better.

    For the Altec cabinet the recommended crossover frequency is 630 Hz with a slope of 24 dB/octave (Linkwitz-Riley) using the Altec 1632A. The 1632 automagically does this, so no need to fret. From there it is just a matter of balancing the output levels for the two drivers (woofer and horn) with the amplifiers.

    Even if you don't have the SPL meter, who cares? Just dial it in until you are happy. If you are wrong, just change the volume control on one of the amps.

    There is no penalty for having the levels wrong and no one will get arrested and the Pope will not have you burned. No need to stress about it, but you always have the power to change the mix if someone arrives at your next party with a signal generator and a SPL meter.


    Quote Originally Posted by Mr. Widget View Post
    Two initial points:

    1). I have been using active systems in home stereo systems since 1980 and in home theater systems since 1998.

    2). There are quite a few threads on this topic.

    Several reasons not to go active:

    First of all, if you start messing around with active crossovers, you have just become a speaker designer. Regardless of how much info you have, you will likely be inadvertently changing the actual crossover frequencies and slopes from those in the original passive design to at least an audible degree. If you don't have proper measurement equipment and know how to use it you will be chasing your tail for quite some time getting the crossovers set correctly and the various amps properly balanced. I am not saying that it is impossible to do without test gear, but to match the original sound of the speaker you may spend weeks screwing around adding a couple of dB here or there one day and changing it back the next...

    Lets assume you have the correct test gear, knowledge, and or the ears to dial it in... then there is the issue of system EQ. Most contemporary systems have built in passive EQ that will be difficult to properly match without the right gear. (If you are dealing with a rather simple vintage system or a DIY masterpiece, then "fixing" the system is entirely up to you anyway.)

    OK, so you are capable of balancing and adjusting the system to your desired flavor. As many have discovered as soon as you add the complexity of outboard crossovers, equalizers, and multiple amps, the likelihood of grounding issues grows significantly and can be a real pain to fix.

    Then there is sensitivity... if you use a high sensitivity compression driver and amp in an active system you will very likely hear background noise... it is almost impossible not to in a home setting which is quiet and you only sit a few meters away from the drivers. If you have only average quality gear or don't have gear that works well together allowing you to properly adjust the gain structure the noise can be quite distracting.

    Which crossover to buy? Most are not particularly wonderful... the really good ones are quite pricy. If you use a quality two-channel preamp and want to transparently preserve it's sound quality, you must use a crossover of similar quality. This leaves you with very few options. The easily obtained pro crossovers are all pretty bad sounding. If you are using a DSP based multi-channel processor or AVR, ignore this part, but if you are trying to approach the sound quality of a top flight passive network with Pass Labs, Levinson, or similar high quality stereo gear... consider moving into active networks cautiously.

    Now, let's say your thinking, "Widget's being too picky... this Rane or Ashly crossover sounds damned fine with my AVR."

    I can go along with that... that is exactly how my last HT setup was run... but why go to the expense of extra amps, crossovers, equalizers, etc. in a system that really won't sound better for it? I did it because my DIY speakers had no networks and I wanted maximum SPL... you may too. However, if you have decent speakers with well engineered networks, the law of diminishing returns is solidly against you... along with the other items I mentioned above.

    So while I have used many active systems... and a number of passives, there are plenty of reasons to consider a passive system, even if you have the means.


    Widget

  8. #8
    Senior Member Loren42's Avatar
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    To specifically address your quote, "but why go to the expense of extra amps, crossovers, equalizers, etc. in a system that really won't sound better for it?"

    The answer was and still is a resounding yes. For my 3-way system that I built I was facing a decision between building a high quality passive network or active.

    The cost of components for the passive system was $200 each. The total cost for the active system (crossover and amps) was about $300 (less cables). That was a monetary no-brainer.

    The improvement over the temp crossovers was instant and the system is performing so much better than before and I still can do more to dial it in even better.

    The only thing I gave up was the ability to drive the speaker system with a home brew tube amp I was going to build. Now I would need three of them and I don't think I will go ahead and do that. ;-)

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Loren42 View Post
    ...the original poster was deciding between two stock crossover systems specifically designed for this speaker system. The Altec A700 was built with these two systems in mind.

    Either one will do nicely, but the active system would be a better pick for the reasons I cited in my post.
    I agree either of these systems will perform equally well... my point was the active system has some advantages along with some potential pitfalls.

    Quote Originally Posted by Loren42 View Post
    I think there is a lot of trepidation about going active, but it is not voodoo or magic, just better.
    I agree that there is no voodoo or magic in setting up a sound system, but I take issue with blanket statements like "just better." I feel that there is rarely a simple one size answer.

    Quote Originally Posted by Loren42 View Post
    Even if you don't have the SPL meter, who cares? Just dial it in until you are happy. If you are wrong, just change the volume control on one of the amps.

    There is no penalty for having the levels wrong and no one will get arrested and the Pope will not have you burned.
    Again, you are right. There is also no penalty for having the drivers out of phase or even swapping drivers, but if you are after accuracy or a specific period sound you may not get what you're after if you simply throw an active system together.

    I admit I added significantly to the conversation veering from the initial post, however when faced with, "In my mind there is absolutely no reason to consider a passive crossover if you have the means and will to go active.", I wanted to post possible reasons to not go active. They may or may not be relevant, case depending.

    As for the down side of a poorly setup system... to some any system that plays loudly is a success and to others there is a very specific sound they are after... simply turning a few knobs may not get you there. Some people feel a car sputtering and spewing blue smoke is running and others feel that a car must be maintained by a guy in a white lab coat... it's all about expectations.


    Widget

  10. #10
    Senior Member baldrick's Avatar
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    I am useing active XO today but I would like to have a simpler system so that's why I'm considering the passive alternative. Since my system is a surround setup, I'm useing 2 active XOs and 3 poweramps together with the surroundamp. It would have been much easier to just have a good surround amp and passive XOs But if it's not a very good solution I will think twice before I go ahead
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    Administrator Mr. Widget's Avatar
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    When you say "surround amp" do you mean a multi-channel basic power amp or do you mean an AVR? If you are using an AVR, I'd recommend using it's pre-outs and continue to use an external basic power amp for at least the front three channels... at least if it is any of the more common AVRs.

    If you are using a separate processor and a multi-channel amp, I doubt there will be much of a quality hit if any moving over to the passive networks... you will likely lose a couple of dBs of headroom, but I doubt in a HT system you will be able to really get the full benefit of the active system. As Loren42 pointed out, there are real potential benefits, but my contention has been that they are not guaranteed.

    If you have the option to try both directions, that is probably your best bet. Then you can decide the route that works best for you.


    Widget

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    Senior Member baldrick's Avatar
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    By surround amp I mean an AVR A highend AVR is capable of SQ that is more than comparable to my Altec amps and even though it will lack a litle power, I would guess it's more than capable fullfilling my needs, so I'm not concerned about that.

    I did in fact get a pair of Altec A8 with the passive N1285-8b yesterday, so I will try it out. But I need to dismount the A8 and also rewire my A700 before I can try (Ohhh, when I wrote the last sentence I just realised that I don't need to rewire the A700 at all since I use the speakon biamped )
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    Quote Originally Posted by Mr. Widget View Post
    I wanted to post possible reasons to not go active.
    The only reason I can think of is that it takes money to do it right. But if someone is just going to listen to typical CD's or MP3's then the usual "couple hundred dollars" active boxes will probably work just fine.

    What kills me is that the DX-1 was only about $300... I will never live down the fact that some jackass decided to toss all one hundred and eighty six of them left in stock into the trash...

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    Administrator Robh3606's Avatar
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    What kills me is that the DX-1 was only about $300... I will never live down the fact that some jackass decided to toss all one hundred and eighty six of them left in stock into the trash...
    Wow!! That's how many got trashed What shame that was.


    but I doubt in a HT system you will be able to really get the full benefit of the active system.
    Hello Widget

    You mean as compared to a 2 channel set-up using more refined gear??

    Rob
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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by baldrick View Post
    By surround amp I mean an AVR A highend AVR is capable of SQ that is more than comparable to my Altec amps and even though it will lack a litle power, I would guess it's more than capable fullfilling my needs, so I'm not concerned about that.
    I don't know anything about those Altec amps... they may be good, or perhaps not so great, I have no idea. The quality of AVR amp sections in general is pretty mediocre at best, even in multi-thousand dollar units. Yours might be the exception, but I would certainly give it a whirl with outboard amps also.

    Quote Originally Posted by 4313B View Post
    The only reason I can think of is that it takes money to do it right. But if someone is just going to listen to typical CD's or MP3's then the usual "couple hundred dollars" active boxes will probably work just fine.
    You are assuming that everyone has the persistence and skill to get it done right.

    Quote Originally Posted by Robh3606 View Post
    Hello Widget

    You mean as compared to a 2 channel set-up using more refined gear??
    Absolutely. With the additional channels and distraction of seeing images flash before your eyes, we can tolerate a less perfect audio experience... in a two channel system with eyes closed, creating the illusion of the concert hall requires more from the equipment.


    Widget

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