# Active vs passive xover



## xyrium (Jul 28, 2008)

Does anyone know of an active vs passive crossover paper that I can read to understand how an active design addresses the driver anomalies (peaks, etc.) that passives resolve? I am about to assemble a new kit, and may consider going active if it would benefit me.


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## JCD (Apr 20, 2006)

There are actually a lot of articles out there that show the benefit of an active crossover -- in fact you can do a search here and I'm sure you'd find several.

However, I think this is probably what you were looking for -- Elliot Sounds Article.

I'm not sure if it's going to address everything you're looking for, but it should lay out a lot of the pros and cons.

As for flattening out a response, it may be "corrected" using the active crossover itself. Behringer has a very popular active crossover that also has EQ abilities.


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## xyrium (Jul 28, 2008)

Thanks again JCD. I'm slightly familiar with the BFD and one other Behringer unit, maybe the DSP1124 or something, and I would most likely use something similar from DBX. I suppose the eq'ing is done via a parametric, which I was under the impression that even with a high Q setting, would impact more than the precise target frequency. I suppose it's a tradeoff that I'd have to listen to though. Thanks for the link. I've read a few of the designs on that site, certainly very interesting. I don't recall him addressing driver anomalies in the articles, but I haven't read them thoroughly, more like a quick skimming. 



JCD said:


> There are actually a lot of articles out there that show the benefit of an active crossover -- in fact you can do a search here and I'm sure you'd find several. However, I think this is probably what you were looking for -- Elliot Sounds Article. I'm not sure if it's going to address everything you're looking for, but it should lay out a lot of the pros and cons. As for flattening out a response, it may be "corrected" using the active crossover itself. Behringer has a very popular active crossover that also has EQ abilities.


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## JCD (Apr 20, 2006)

This is the unit I was referring to -- Behringer DCX2496.

I know someone who uses this with a ridiculously good DIY set of speakers and it sounded amazing. The DBX is also a good choice, but I think this unit does everything that the DBX does but at a smaller cost.


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## xyrium (Jul 28, 2008)

Ahh yes. And fully compatible with REW's output. Something I will definitely consider! Thanks!


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## JCD (Apr 20, 2006)

There is going to come a day when I design and build my end all be all system. That unit is going to be a part of it. It's a tweakers dream since it can a 1st through 8th order crossover rolloff. It can do a bessel, Linkwitz-Riley or a butterworth type of crossover. It's got the EQ built in. You can time delay the different signals. For as little as $250 (I've see it that low), it's a bargain.


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## lsiberian (Mar 24, 2009)

xyrium said:


> Does anyone know of an active vs passive crossover paper that I can read to understand how an active design addresses the driver anomalies (peaks, etc.) that passives resolve? I am about to assemble a new kit, and may consider going active if it would benefit me.


The biggest issue with going active is amp cost. 

For the tweeters you'd want a Class A amp, an AB for the next level, and the next two levels could be a Class D.

Though I'm tempted to try the class D kits.


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## JCD (Apr 20, 2006)

lsiberian said:


> The biggest issue with going active is amp cost.
> 
> For the tweeters you'd want a Class A amp, an AB for the next level, and the next two levels could be a Class D.
> 
> Though I'm tempted to try the class D kits.


Completely agree. That cost is somewhat offset by the cost of the crossover parts you don't have to buy.

A few more points I could add..

I'd probably get an amp that was <35watts for the tweet
I'd probably get an amp that was <75watts for the mid
I'd probably get an amp that was <100 watts for the woofer


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## lsiberian (Mar 24, 2009)

JCD said:


> Completely agree. That cost is somewhat offset by the cost of the crossover parts you don't have to buy.
> 
> A few more points I could add..
> 
> ...


What are your thoughts on Audiosource amps. They have trims so you could attenuate the incoming DCX2496 signal.


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## xyrium (Jul 28, 2008)

Come on, you guys are hijacking my thread! LOL.

A couple of thoughts. First, I don't think we can assign a specific class of amp to a specific speaker unless you know exactly what instruments, including human voice, that it will be affecting. For instance, if you xover at 2kHz, both the woofer and tweet are reproducing human voice. So, if that Class A amp actually has some sort of sound imprint, voices would be oddly represented.

Second, I also don't think you can just toss wattage at each speaker, expecting that the tweeter needs less than the woofer. I see many "pro" designs with built in amps and xovers doing this, but the design is based on the sensitivity and impedance characteristics of each driver. This said, we really can't arbitrarily assign specific numbers (Wattage) to an unknown design. Additionally, you'll need double the wattage of a particular amp just to obtain a 3dB increase in SPL. So, many factors to consider I suppose. 

However, I still don't see how these electronic xovers do anything but provide a dividing line between each driver. In order to handle driver anomalies, they would have to implement a parametric EQ to notch certain areas of concern. THat's where pieces like the Berry units come in I suppose.

Am I on the right track?


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## xyrium (Jul 28, 2008)

I had an Audiosource Amp One/A. Great amp, perfect for the L15 design I was powering with it. The little thing ran pretty damned hot, but never gave up. However, I think that design may be different (better?) than the HT stuff they are putting out there right now.


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## JCD (Apr 20, 2006)

xyrium said:


> Come on, you guys are hijacking my thread! LOL.
> 
> A couple of thoughts. First, I don't think we can assign a specific class of amp to a specific speaker unless you know exactly what instruments, including human voice, that it will be affecting. For instance, if you xover at 2kHz, both the woofer and tweet are reproducing human voice. So, if that Class A amp actually has some sort of sound imprint, voices would be oddly represented.


The class of amp is really a function of the wattage being used. All things being equal, a Class A amp is going to be superior in performance to a Class AB. When you start getting into a Class D amp, they're extremely inexpensive on a per watt basis, but I'd argue most would say they have a lot of extra odd harmonic distortion and therefore wouldn't be very appropriate for any thing other than the lowest octaves.



xyrium said:


> Second, I also don't think you can just toss wattage at each speaker, expecting that the tweeter needs less than the woofer. I see many "pro" designs with built in amps and xovers doing this, but the design is based on the sensitivity and impedance characteristics of each driver. This said, we really can't arbitrarily assign specific numbers (Wattage) to an unknown design. Additionally, you'll need double the wattage of a particular amp just to obtain a 3dB increase in SPL. So, many factors to consider I suppose.


I think you can make some generalities -- tweeters are usually much more sensitive than a mid which is more sensitive than a woofer. Again, it's a generality, but it's probably more accurate than in-accurate.



xyrium said:


> However, I still don't see how these electronic xovers do anything but provide a dividing line between each driver. In order to handle driver anomalies, they would have to implement a parametric EQ to notch certain areas of concern. THat's where pieces like the Berry units come in I suppose.


Since you don't need to worry about the impedance curve of the drivers in the crossover area, it's much easier to get a flat frequency response. Zobel networks and notch filters to flatten the impedance curve for the tweeter/mids/woofers are no longer needed. Plus you don't have to use passive components in the first place -- so all the extra unwanted "stuff" they add to the signal is avoided. 

You can also perfectly time align your individual drivers -- something you can't do with crossover parts. You can with a slanted baffle, but that has it's own issues. 

You also can add 3dB's to the over all sensitivity of the speaker. I've heard that's the amount your average crossover steals.

And with the driver anomalies ca you mention, using an EQ is going to be easier than fixing it with passive parts. And, I'd argue, sound better. Tons better? maybe not, but better.



xyrium said:


> Am I on the right track?


Like most things in audio, it depends on who you ask. I'm a big proponent of active crossovers. There are others who aren't. I'm just throwing out some info I've picked up. Hopefully it helps.


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## Paul P (Dec 5, 2009)

JCD said:


> Like most things in audio, it depends on who you ask. I'm a big proponent of active crossovers. There are others who aren't. I'm just throwing out some info I've picked up. Hopefully it helps.


I don't doubt that an active crossover / speaker management system will give you great flexibility
but what do they sound like ? I have trouble imagining that so much processing can be made
completely transparent (not that a passive crossover is transparent). Is it an analog vs digital 
thing ? What's the noise like ? The DCX2496 seems like a pretty big thing to be putting in the
signal chain.

Paul P


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## xyrium (Jul 28, 2008)

Thanks JCD, all of this helps tremendously! I've been contemplating going active for a long time. After I build the sealed ZRT, I plan to pick up one of those Berry's and experiment a bit. As long as the device doesn't raise the noise floor of my setup, it seems to have all of the tools on it to shape the sound however I'd like.


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## ironglen (Mar 4, 2009)

JCD said:


> Completely agree. That cost is somewhat offset by the cost of the crossover parts you don't have to buy.
> 
> A few more points I could add..
> 
> ...


Based on what I read on threads regarding active/passive, and with helpful responses by HTS'ers I'm using this hybrid passive/active system using some small mb quart bookshelves (1" tweeter, 5.25" ported mid) driven by 60w/ch and (planned) dual anarchy 6.5" mid-bass @ 120w/ch. The mb quarts passively cross at 2khz and I'm using samson 3-way to actively cross at perhaps 300 hz. I will be placing the mb's atop the anarchy 'bass bins' and should be able to set the mb back a touch to align them better. I picked up the pro amps and active crossover for ~$200, if it works out, I plan to add another crossover and amp to power an identical center. Seems like it should work nicelyonder: while keeping cost manageable, total cost should fall around $1100 for full 7.0 with the matching front three full-range 'towers'.


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## xyrium (Jul 28, 2008)

Wow, that would one of a system for such a low cost. Photos please!!!


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## ironglen (Mar 4, 2009)

xyrium said:


> Wow, that would one of a system for such a low cost. Photos please!!!


Yeah, I'm hoping so. Bigger isn't always better, but I think it's a good plan. Info led me to use the hybrid design as more cost effective, that is, if you buy the bookshelves on the cheap and they are worthy of the overall system. It was said using active for lower freq's saved more money, and an entire active system was too costly, so...

The mb quarts arrived last night, well packaged from the German factory. I must say, the faux black woodgrain looks exceptional. I picked them up from an overstock-type dealer on ebay after I negotiated his buy it now price-I'll give them a listen this weekend. $316 to my door (after a 10% off coupon) for all eight german-made mb's! I believe they went for $300/_pair_ several years ago. Now I just gotta figure and build bass bins that blend with these.


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## JCD (Apr 20, 2006)

Paul P said:


> I don't doubt that an active crossover / speaker management system will give you great flexibility
> but what do they sound like ? I have trouble imagining that so much processing can be made
> completely transparent (not that a passive crossover is transparent). Is it an analog vs digital
> thing ? What's the noise like ? The DCX2496 seems like a pretty big thing to be putting in the
> ...


It does seem a little counter intuitive, but based on my one direct listening experience, the results were pretty impressive. Not that I have a golden ear or heard a side by side comparison, but I didn't hear any loud sound floor. 

The guy who had incorporated the unit into his system does know what he's doing and did have to fiddle with it, but once he got it dialed in, he was quite happy with the results. He will state till the end of days that similar results could NOT be gotten with the BEST passive crossover.

Another person I know who is an analog purist wouldn't use the Behringer because it is digital, however, he was also a huge proponent of active crossovers, just a purely analog version. He will also say that similar results could NOT be gotten with the BEST crossover.

These two people arguably have the best systems (speakers pus electronics plus rooms) I know of. Both are complete advocates of active systems even if one prefers digital (i.e., CD's, solid state amps) and the other prefers analog (e.g., LPS, tube based SET amps).

Again, these are their opinions, but I've seem similar comments with others that have done the same thing.


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## lsiberian (Mar 24, 2009)

xyrium said:


> Come on, you guys are hijacking my thread! LOL.
> 
> A couple of thoughts. First, I don't think we can assign a specific class of amp to a specific speaker unless you know exactly what instruments, including human voice, that it will be affecting. For instance, if you xover at 2kHz, both the woofer and tweet are reproducing human voice. So, if that Class A amp actually has some sort of sound imprint, voices would be oddly represented.
> 
> ...


Amp audibility is sketchy at best. I'd gander few folks can pass an ABX test between anything but tubes and solid state. As long as the amp is well designed. The reason for a call A amp on the tweeter is the low power reserves and safety it would bring the end user from popping their tweeter. Reasonably I know of no reasonably priced class A amp so I'd not suggest it unless you want to build your own. 

an A/B amp is perfectly sufficient for almost any level. If you want to best bang for buck fan mod a behringer 2500. You'd need 2 of them for a 2 way speaker. I just have a hard time with the idea of putting a powerful amp like that on a tweeter. I really would love to have a 3-way stagged amp for a 3-way speaker. But such a design can only come from DIY audio. 

Class D amps have improved a lot from their old days. As always any amp comparison test must be done either ABX or via measurements. Side by side listening is an ineffective test of amp audiblity because of :coocoo:acoustics.

of course you don't buy amps based on sound you buy them based on how long they will hopefully last.


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## lsiberian (Mar 24, 2009)

JCD said:


> It does seem a little counter intuitive, but based on my one direct listening experience, the results were pretty impressive. Not that I have a golden ear or heard a side by side comparison, but I didn't hear any loud sound floor.
> 
> The guy who had incorporated the unit into his system does know what he's doing and did have to fiddle with it, but once he got it dialed in, he was quite happy with the results. He will state till the end of days that similar results could NOT be gotten with the BEST passive crossover.
> 
> ...


JCD the best speaker designer I know advocates active and the 2nd best just decided he prefers them too. So I think it's probably the way to go in some cases. But let's remember that for budget systems a kit with a crossover in it will net better results. The Madisound RB kit is my recommendation to anyone want to get into DIY speakers. Build a pair of those first. Then start looking at the bigger stuff. I personally use those very kits and they are very good speakers. Finishing that kit was a great accomplishment for me and I learned a ton.


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## xyrium (Jul 28, 2008)

I agree with you on all accounts, especially on amp audibility and the cost/performance ratio of the kits at Madisound. Though I haven't tried any at PE, they look quite good as well. Woul d you be talking about the Orion in speaker 1 or 2 by any chance?


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## JerryLove (Dec 5, 2009)

Paul P said:


> I don't doubt that an active crossover / speaker management system will give you great flexibility
> but what do they sound like ? I have trouble imagining that so much processing can be made
> completely transparent (not that a passive crossover is transparent). Is it an analog vs digital
> thing ? What's the noise like ? The DCX2496 seems like a pretty big thing to be putting in the
> signal chain.


 The noise is nearly non-existant. The DCX2496 does an ADC, manipulation in the digital domain, and a DAC. The only place for potential loss is the A-D-A conversions, and the DACs are excellent.

Yes. Manipulation of sound in the digital domain is completely without noise and, assuming your algorithms are good, without error. The problems in analog crossovers simply don't exist in digital crossovers. There really are no audio down-sides I can tell. The down sides are cost (depending on the cost of the passover), the need for multiple amps, and the need for power to the active crossover.

It's acutally pretty similar to the move from matting to digital compositing in the video world. 

Remember, the DCX2496 is balanced in/out: so you will either need to convert that, or run balanced pre and amps (I recommend the Yamaha pro line of amps).


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## mjg100 (Mar 12, 2008)

ironglen said:


> Based on what I read on threads regarding active/passive, and with helpful responses by HTS'ers I'm using this hybrid passive/active system using some small mb quart bookshelves (1" tweeter, 5.25" ported mid) driven by 60w/ch and (planned) dual anarchy 6.5" mid-bass @ 120w/ch. The mb quarts passively cross at 2khz and I'm using samson 3-way to actively cross at perhaps 300 hz. I will be placing the mb's atop the anarchy 'bass bins' and should be able to set the mb back a touch to align them better. I picked up the pro amps and active crossover for ~$200, if it works out, I plan to add another crossover and amp to power an identical center. Seems like it should work nicelyonder: while keeping cost manageable, total cost should fall around $1100 for full 7.0 with the matching front three full-range 'towers'.


I have been doing some thing like this for awhile. I have a small room so I am using RBH WM-30 on wall speakers for the mid/high unit. These have 1" fabric dome tweeters, two 4" woofers and two 4" passive radiators. I used a Behringer CX2310 to crossover to bass bins that use the 10" drivers from the NHT XdW subwoofer. I did this for my front three speakers. The sound was great. The system had a lot of head room and dynamics for such a cheap system. My room is acoustically treated and I use an acoustically transparent screen. 

I did a lot of experimenting with my system and currently I am doing things differently. I am still using the RBH WM-30's for the mid/high unit, but rather than go through the CX2310 I cross everything to my subs with my AVR. I have a sub located below all of my speakers (5.1) and I cross all of my speakers to my subs at 100Hz. This way I have six 10" drivers and one 12" driver reproducing all of the bass under 100Hz. The system sounds great for such a low cost. I bought nearly all of the amps and drivers for my subs at close out prices. My brother has Meridian DSP600 mains ($20,000/pair MSRP) used in his 5.1 ht. He has listened to my system and likes it better (for movies) than his. It is all about the subs, sub intergration and room treatments. With my mid/high units I have tried 100Hz, 120HZ, 150Hz, 180Hz and 200Hz. I did not notice any improvement once I went above 100Hz so that is what I am currently using.


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## ironglen (Mar 4, 2009)

mjg100 said:


> I have been doing some thing like this for awhile. I have a small room so I am using RBH WM-30 on wall speakers for the mid/high unit. These have 1" fabric dome tweeters, two 4" woofers and two 4" passive radiators. I used a Behringer CX2310 to crossover to bass bins that use the 10" drivers from the NHT XdW subwoofer. I did this for my front three speakers. The sound was great. The system had a lot of head room and dynamics for such a cheap system. My room is acoustically treated and I use an acoustically transparent screen.


I like what you've done. Do you use it to listen to 2 channel often, or exclusively for ht?


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## mjg100 (Mar 12, 2008)

I use my room nearly 100% for HT.


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## sfdoddsy (Oct 18, 2007)

Let's remember that most of us already have semi-active systems, at least those who use subs.

A fully active speaker spreads those benefits across the whole system.

I've been active for the past 8-9 years and I can't imagine going back.

I'm no longer a believer in big amp difference, and so use an 8 channel QSC pro amp I picked up on eBay for $600 with my DCX.


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## lsiberian (Mar 24, 2009)

sfdoddsy said:


> Let's remember that most of us already have semi-active systems, at least those who use subs.
> 
> A fully active speaker spreads those benefits across the whole system.
> 
> ...


The issues with passive xovers are overblown like many other issues in DIY speaker design.

Remember new folks to this hobby are usually much lower in expectations than an experienced builder. You could build a passive 3-way that is better than almost many pairs of speakers for less than the $ spent on extra amps for an active design. Madisound will do the design and even build the crossover for you if you are scarred of the passive approach for a reasonable price. 

I can't suggest full active systems for folks with budgets. I probably will not be going that route due to costs.


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## JCD (Apr 20, 2006)

lsiberian said:


> The issues with passive xovers are overblown like many other issues in DIY speaker design.
> 
> Remember new folks to this hobby are usually much lower in expectations than an experienced builder. You could build a passive 3-way that is better than almost many pairs of speakers for less than the $ spent on extra amps for an active design. Madisound will do the design and even build the crossover for you if you are scarred of the passive approach for a reasonable price.
> 
> I can't suggest full active systems for folks with budgets. I probably will not be going that route due to costs.


Make no mistake, for an inxpensive DIY system, I wouldn't go active either, but for a "serious" system, I don't think I would go passive. I designed a system recently. The part costs for the crossover were about $50/speaker. For two, it's $100. I bet one could find a used amp for about $150. And these weren't exotic parts -- not junk, but not expensive.

But your point is valid. If you're going to with a cheaper DIY kit, passive makes economic sense.


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## xyrium (Jul 28, 2008)

Hey guys, if passives are inferior, why are the high end designs from some of the more popular builders on these forums such as Jed from Clearwave, John Krutke, etc., still using passives? There has to be something these guys are missing, and active components can be found in many nearfield powered studio designs for a relatively low price.


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## JCD (Apr 20, 2006)

I'd say cost is going to be a big part of it -- if you're getting into a big time speaker, you'll want a big time amp, so the cost just goes up. And for the most part, the public doesn't know or care about the advantages.

There have been attempts by companies to provide a active speaker for the home market, but they just haven't caught on. Paradigm used to have a powered speaker that was supposed to be a great speaker, but it just didn't catch on.

But there are always exceptions.

If you look at the studio mixing market, I think most of those speakers are all actively powered. For example, the Mackie 824 is supposed to be a great speaker (even for HT use) and it has it's own amps and electronic crossover.

Linkwitz's Orion speakers are active and are regarded as a great speaker -- but the only people that really know about them are the folks like us -- into the audio hobby.

I also don't want to oversell the active thing -- I do believe that the best performance is going to be a properly designed active system; however, properly treating a room acoustically is far more important.


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## xyrium (Jul 28, 2008)

Hey Jacen,

Yep, and my current build is exactly for that, a small home studio. I've used various KRKs, JBL LSRs for a week, and M Audios. All powered with active filters. The last pair I got were Emu PM5s, probably the weakest of the lot and require a sub. 

However, as soon as I went to an external amp and passive speakers, the entire sound stage opened up, and I was then inspired to assemble the ZRTs in a sealed cab. I don't have a large room, so these should be close to perfect.

I've seen the Orions, definitely cost prohibitive, but an interesting design concept! Interesting though is his use of a run of the mill ATI amp which I completely support. I have reached the point where I believe the expense at the speaker level far outweighs the benefits from any other device in the signal chain (speakers make the greatest difference). I am also building the ZRT with two pairs of binding posts, so I can try an active setup sometime down the road. Maybe next Spring. I think the ZRTs are a good candidate for active design because they aren't metal cone drivers, and may not require a tremendous amount of eq'ing to get relatively flat. I'll probably pick up another Parasound A23, and one of the Berry xovers. Wish me luck!

Edit: Wow, the dbx DriveRack 260 seems like the perfect tool. While the Behringer stuff seems decent, I'm concerned about quality. I'd think that dbx or Rane might be the next step up, though still not perfect of course.


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## F1 fan (Jul 6, 2006)

I'm also a strong proponent of the active approach and use an active 4way in my main system.While the DCX unit is incredibly versatile I prefer the pure analog approach using (mostly)DIY PC boards that I can configure for the exact response I desire.If one is electronically inclined using the kits from the likes of Marchand are an excellent way of getting your feet wet with actives. http://marchandelec.com/xovers.html

Linkwitz's site is also a good source of info.http://www.linkwitzlab.com/filters.htm


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## lcaillo (May 2, 2006)

Marchand seems interesting. Does anyone else have experience with them? Good, bad, otherwise?

I started a thread for them and put them in the vendor listings. Post any general info about them that you have in the thread below:

http://www.hometheatershack.com/for...um/23867-marchand-electronics.html#post217580


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## F1 fan (Jul 6, 2006)

I haven't personally used the Marchand offerings but have heard excellent reports from others that have.My DIY units were from two other sources that unfortunately are no longer available.


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## xyrium (Jul 28, 2008)

I agree. Marchand has been around for a long time, or maybe I'm thinking of Van Alstine (or both). I have frequently heard Marchand come up in discussion about xovers.

Either way, an electronic EQ should only be considered a starting point in going active. Unless the xover module includes notch filters, and EQ'ing (like the dbx I mentioned earlier, or the various Berry's people are using), I don't see how one can achieve a tight tolerance on frequency response across the spectrum by just dividing frequency ranges across drivers and not addressing the driver breakup nodes, etc.

So, my question is, how many of those who advised that they've gone entirely actively, are addressing the driver anomalies, or are you just sufffering through the peaks and valleys in lieu of increased efficiency?


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## lsiberian (Mar 24, 2009)

lcaillo said:


> Marchand seems interesting. Does anyone else have experience with them? Good, bad, otherwise?
> 
> I started a thread for them and put them in the vendor listings. Post any general info about them that you have in the thread below:
> 
> http://www.hometheatershack.com/for...um/23867-marchand-electronics.html#post217580


looks a bit pricey for my tastes.


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## lcaillo (May 2, 2006)

Actually, you can get the raw crossover modules for $70. If you were trying to do it on the cheap you could come up with your own PS and use fixed resistors for the settings once you figured out what you needed, and stuff it in your own box and it could be done pretty cheap.


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## Drew Eckhardt (Oct 24, 2009)

lcaillo said:


> Actually, you can get the raw crossover modules for $70. If you were trying to do it on the cheap you could come up with your own PS and use fixed resistors for the settings once you figured out what you needed, and stuff it in your own box and it could be done pretty cheap.


Marchand has some simple cross-overs (XM1) that you shouldn't be interested in because they won't accommodate the shelving filter you want for baffle step compensation or all-pass you want to aim the cross-over lobe. They have the XM44 series which puts the passive components surrounding each dual-op amp on a board with a corresponding card-edge connector on the main board. The full XM44 system has three slots per input/output pair; the XM44-EMB has two. Each op-amp (two per dual package or card) gets you a two pole high/low/band-pass, a shelving filter, a peaking filter, a biquad, or a notch filter.

For many applications you may be better off with Siegfried Linkwitz's boards.

The ASP is good for a 3-way with up to 4th order slopes, with two all-pass sections on each of the midrange and tweeter channels, level adjustments on woofer and tweeter, two notch filters for the midrange and one for the woofer, shelving low-pass on the midrange for dipole or baffle step compensation, and Linkwitz Transform or shelving low pass on the woofer channel.

The topology cascades the filters (IOW, the lowest frequency high-pass feeds a low-pass for the midrange and high-pass for the tweeter) which SL states is required for correct acoustic summation.

It's completely silent.

http://www.linkwitzlab.com/pcb.htm

The Pluto boards include LM3886 chip amps and 3-terminal regulators to drive the cross-over, are good for a 2-way with up to 4th order slopes, have a single tweeter amp and bridgeable mid-bass amplifiers, all-pass on the tweeter, level adjustment for the tweeter, notch filters for both channels, and a Linkwitz transform or shelving low-pass filter on the woofer. You could probably adjust the shelving high-pass filters on the power amps to be in the audio pass-band if you wanted.

They're completely silent except in environments with RF issues.

http://www.linkwitzlab.com/Pluto/electronics.htm

Both boards have pads for proper op-amp power supply bypassing and low-pass capacitors in the feedback loops where practical for low-pass filters with RF cut-offs.

Both are $100/pair.

Starting with solder-less bread board may be a fine idea.

Linkwitz has a nice active filter cook-book 

http://www.linkwitzlab.com/filters.htm


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## Drew Eckhardt (Oct 24, 2009)

xyrium said:


> So, my question is, how many of those who advised that they've gone entirely actively, are addressing the driver anomalies, or are you just sufffering through the peaks and valleys in lieu of increased efficiency?


Both Orion in the living room and Pluto+ in the bedroom correctly address driver response issues.


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## lsiberian (Mar 24, 2009)

Drew Eckhardt said:


> Marchand has some simple cross-overs (XM1) that you shouldn't be interested in because they won't accommodate the shelving filter you want for baffle step compensation or all-pass you want to aim the cross-over lobe. They have the XM44 series which puts the passive components surrounding each dual-op amp on a board with a corresponding card-edge connector on the main board. The full XM44 system has three slots per input/output pair; the XM44-EMB has two. Each op-amp (two per dual package or card) gets you a two pole high/low/band-pass, a shelving filter, a peaking filter, a biquad, or a notch filter.
> 
> For many applications you may be better off with Siegfried Linkwitz's boards.
> 
> ...


I'd prefer to use a DCX 2496. It's the amping that introduces cost issues for me.


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## Drew Eckhardt (Oct 24, 2009)

lsiberian said:


> I'd prefer to use a DCX 2496. It's the amping that introduces cost issues for me.


One 60W/channel multi-channel amplifier will generally cost no more than one 200W/channel stereo amp which provides the same output level. I like used bipolar Adcoms (they're inexpensive and stable into any load you can come up with) and would compare the 2535 to the 555ii. 

If you're building your own amps you can use smaller heat sinks and power transformers.

Amps with discrete output stages can split their devices among the channels now that power dissipation is much lower and the extra driver stages shouln't cost as much as you save on the heat sink and transformer in small quantities.

If you're using chip-amps you may be able to go from bridged/parallel to single amps; and even if not you're looking at $12 in parts (using film caps for the amplifier high-pass circuit; bipolar electrolytics would be cheaper) per channel for small quantities (production runs are much less expensive).


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## Kevin Haskins (Nov 14, 2007)

It is like anything in audio, some of the reasoning is legit and some of it is not. 

From someone who designs loudspeakers and transducers it does open up a lot of design flexibility that you wouldn't have with a passive design. If you implement a passive design right it can be done with very good results. But amplifiers and DSPs get cheaper every year so the value proposition just keeps getting better for fully active. 

The main thing for me is the flexibility you have on the bottom-end. You can do things active that just cannot be done for any cost passively. You have a lot of flexibility in performing room PEQ, subsonic filters and limiting filters too so there are a lot of cool tricks that just are not possible without a DSP. It is also easy to acoustically align drivers since time delay is simple with a DSP so you can get better phase tracking through the crossover not to mention you have almost an infinite amount of flexibility with filter choices without the constraints put upon a designer trying to deal with component cost, physical constraints etc.. etc... 

Download the Hypex Filter Designer software. 

http://www.hypex.nl/docs/AS2.100/HypexFilterDesignerv1.3.zip

http://www.hypex.nl/docs/AS2.100/Manual%20AS2.100.pdf

This is getting pretty close to the "cats meow" for active design because you can import transducer measurements and perform whatever filter functions you choose. It doesn't alleviate the need for good design but it is a powerful tool.

Kevin Haskins
Exodus Audio


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## lsiberian (Mar 24, 2009)

Drew Eckhardt said:


> One 60W/channel multi-channel amplifier will generally cost no more than one 200W/channel stereo amp which provides the same output level. I like used bipolar Adcoms (they're inexpensive and stable into any load you can come up with) and would compare the 2535 to the 555ii.
> 
> If you're building your own amps you can use smaller heat sinks and power transformers.
> 
> ...


I'm interested in the idea, but I'm not an electrical engineer and the books are bit over my mind for some reason. If I could design the circuit I would give it a go.


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## Kevin Haskins (Nov 14, 2007)

Drew Eckhardt said:


> One 60W/channel multi-channel amplifier will generally cost no more than one 200W/channel stereo amp which provides the same output level. I like used bipolar Adcoms (they're inexpensive and stable into any load you can come up with) and would compare the 2535 to the 555ii.
> 
> If you're building your own amps you can use smaller heat sinks and power transformers.
> 
> ...


I have an active design done with opamps and LM3886s and for 100 units, cost is comparable to what I'd spend on the passive design for the same system. Most loudspeaker designers are not amplifier designers and vice-versa and there is also the issue of what sells. Often times consumers desires are not rational from an engineering standpoint. If customers don't recognize the value and support it with sales, it just never happens. That is a large part of why active designs are not the norm in home theater/audio loudspeakers. It has more to do with what the market wants and what sells rather than what works best. 

Kevin Haskins
Exodus Audio


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## F1 fan (Jul 6, 2006)

xyrium said:


> So, my question is, how many of those who advised that they've gone entirely actively, are addressing the driver anomalies, or are you just sufffering through the peaks and valleys in lieu of increased efficiency?


Good question ,in my case I used drivers that had reasonably smooth response for atleast an octave beyond the intended crossover frequency.With the 24db slopes any anomalies beyond an octave in the stop band will be so far down in level as to be insignificant. The desired amount of delay for the high pass section was acomplished by using a slanted baffle of approximately 10 degrees, instead of electronically via an all pass network.Being a 3way shelving filters were not stricly necessary for baffle step compensation but the PC boards I used did allow for the incorporation of such.Aswell these specific boards were designed with the capability of adding notch,peak,shelving, all pass, and Linkwitz transform should one desire it.


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## xyrium (Jul 28, 2008)

Marchand obviously addresses driver anomalies with the use of add on cards, and their XM44 seems very nice indeed. The "Pro" midrange brands like dbx, Rane, Ashly, etc., address it similarly, but in the digital domain, and then the final output is analog. Additionally, they have variable settings, so if you're drivers begin to break in and their response changes slightly, you can handle that without any upgrades, or changes in hardware. I think some of them even do a sweep and make all of the corrections automatically. Hmm, I'd love to see someone who has REW output from a pair of three or two ways using this option.

However, I believe you've answered my questions essentially. There are electronics manufacturers out there that make units, tailored to your needs. I suppose the pro brands seem more attractive because they have variable settings. Either way, my current project is going to be ready for that test when the time comes. I'll put some jumpers on the binding posts for now...

Then I'll just need to find another amp with gain settings so I can adjust the output at the amp to keep the driver response flat. The Bryston 2B-LP seems like a nice piece to power the tweeters.




Drew Eckhardt said:


> Both Orion in the living room and Pluto+ in the bedroom correctly address driver response issues.


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## F1 fan (Jul 6, 2006)

xyrium said:


> The Bryston 2B-LP seems like a nice piece to power the tweeters.


Ironically thats what is powering my SEAS H1212 tweets.A HYPEX UcD180 drives the mids and an older Bryston 3B on the woofers.


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## xyrium (Jul 28, 2008)

Nice, thanks Kevin. I obviously have some more reading to do!!!  I just want to be relatively prepared if I decide to take the plunge next year.



Kevin Haskins said:


> It is like anything in audio, some of the reasoning is legit and some of it is not.
> 
> From someone who designs loudspeakers and transducers it does open up a lot of design flexibility that you wouldn't have with a passive design. If you implement a passive design right it can be done with very good results. But amplifiers and DSPs get cheaper every year so the value proposition just keeps getting better for fully active.
> 
> ...


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## F1 fan (Jul 6, 2006)

Kevin Haskins said:


> I have an active design done with opamps and LM3886s....


Are there any specifics of the design that you can share without giving away an proprietary info?


> If customers don't recognize the value and support it with sales, it just never happens. That is a large part of why active designs are not the norm in home theater/audio loudspeakers. It has more to do with what the market wants and what sells rather than what works best.


Unfortunately actives seem to be a hard sell to the general A/V buying public,only hard core DIY'ers and those using the small pro active monitors in there studio's seem to embrace the benifits.


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## Kevin Haskins (Nov 14, 2007)

There is nothing proprietary about it. It was a design done with NE5532s and LM3886s on a single PCB along with the main power supply and low-voltage regulated supply. I have a pair of LM3886s bridged driving one of my Anarchy midwoofers and a single LM3886 driving the tweeter. I did the design for a Seas DXT tweeter but the board is general enough to be used with others if I wanted. 

It also had a THAT Corp balanced line receiver, HP subsonic filter that allowed me to change the Q to add a little boost and protect under the ported driver, a couple generic S-K filters and a couple notches for both the drivers. I could bypass any that I didn't need but it was only 4 dual opamps in front of the LM3886s. I used standard LM317/337 regulators that ran off the main power supply which was only +/- 25V rails to begin with. Filter caps were all on board but the bridge rectifiers mounted to the chassis and a 200VA transformer. The PCB was only 7" x 3.5" and standard 2-layer board so it was pretty inexpensive and small. The Parts BOM was in the neighborhood of $50 via Digikey/Mouser minus the transformer. 

Kevin Haskins
Exodus Audio


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## Drew Eckhardt (Oct 24, 2009)

lsiberian said:


> I'm interested in the idea, but I'm not an electrical engineer and the books are bit over my mind for some reason. If I could design the circuit I would give it a go.


www.chipamp.com sells LM3886 circuit boards for $6 a channel, complete kits for $20/channel (less power supply), and a power supply kit for $30.

For common things you don't even need to layout a PCB.


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## F1 fan (Jul 6, 2006)

Thanks Kevin,by chance do you sell the blank boards? I have a pair of Zaph's ZA14's on the way and hopefully a pair of the new Vifa NE series tweets soon.Having the xover and 3886's on a single PC board would be a nice and neat way to experiment with them actively.


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## Kevin Haskins (Nov 14, 2007)

F1 fan said:


> Thanks Kevin,by chance do you sell the blank boards? I have a pair of Zaph's ZA14's on the way and hopefully a pair of the new Vifa NE series tweets soon.Having the xover and 3886's on a single PC board would be a nice and neat way to experiment with them actively.


I have a couple prototype boards in my lab but nothing I sell. I'd never sell it as bare boards. I just don't have the time to support something like that. It would be a nightmare so if I ever do end up selling something based upon the board it would only be a finished product.

If you want to lay out a PCB it isn't rocket science. The schematics for the filters are all in one of the many opamp cookbooks on the web. I use the Reference Designs published by National for the LM3886 (ignore all the audiophile suggestions for leaving out parts). 

Kevin Haskins
Exodus Audio


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## F1 fan (Jul 6, 2006)

Kevin Haskins said:


> . I'd never sell it as bare boards. I just don't have the time to support something like that. It would be a nightmare ....


Well I can imagine there would be a lot of hand holding necessary if they ended up in the hands of those with little expierience in electonic assembly.:yikes:



> If you want to lay out a PCB it isn't rocket science. The schematics for the filters are all in one of the many opamp cookbooks on the web


It would likely be cost prohibitive to have a production run of custom boards done when I only need a few, so I will have to stick with my tried and true Vector board method. I have done several active filters,gain stages etc. using them but a purpose built PC board would be much simpler to assemble not to mention neater.Your description of your design had me hoping as it would be perfect for the project I have in mind.


> I use the Reference Designs published by National for the LM3886 (ignore all the audiophile suggestions for leaving out parts).


I have built a pair of chip amps of the LM3875 variety and used substanially more filter capacitance than some of the Gainclone guru's are recommending.The extreme minimalism and small filter cap approach doesn't make much sense to me.

Btw.Your Anarchy looks like a lot of driver for the money.:T


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## hdspeakerman (Dec 16, 2006)

xyrium,
I did not read the entire thread but there is go info at the Rane website about their crossovers. I have a two way and a three way and I like them very much. They are good with many drivers but I would not recommend them with aluminum drivers. You can buy one on ebay or audiogon cheaply and experiment with them. That is the best way to learn what they are about and you can still keep learning about passive crossovers if you like. Howard


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## xyrium (Jul 28, 2008)

THanks Howard. When I was younger, I used several Audiocontrol electronic xovers in a mobile audio setup, so I have a fair understanding of that area, including the notch filters, etc. However, the xover between the mids and tweets were always passive. This said, the aluminum drivers as you mention, are certainly cause for concern, and thus the need for some level of EQing on the xover device. Since I would prefer to avoid having more than one more device in the signal chain, I'd like to find something that does both the EQ function (1/3 probably) and xover, in the digital domain. Thus, the interest in the dbx Driverack 260. I think that will be device I'll use should I decide to go this route in the future. Having about $175.00 invested in the current passive xover will probably put that off for a while, though I have an Audiolab preamp and Onix CDP that I might sell shortly to reduce the apparent cost.


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## bobolix (Jan 4, 2010)

If the efficiency of the drivers for different bands is the same approximately, then at active loudspeaker design there is no reason to use amps with different peak output power for different bands. Only the sustained power can (and should) be reduced for the tweeter. Particularly, if the crossover frequencies are 300 Hz and 3 kHz e.g., then the sustained power in the bass band is approx the same as in the midrange, whereas in the highs it is usually less than 20% of bass or mids. But, the peak power in all bands can reach the same level. And in general, the total sustained power (the long-term average) is usually less than several percent of the peak total. Further, the true rated power of usual tweeters (long term again) is less than one tenth of this for the midranges or woofers. 

One important conclusion - the power protection of the tweeter is a *must* at the active design, otherwise :fireworks2:.


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## xyrium (Jul 28, 2008)

If efficiency of the drivers is the same, as you propose, and power handling within it's frequency range (the SS 6600 has an fs of 550Hz i believe) why would one need to be more concerned about it? 

What I am gettng at, is that many two way designs cross the tweeter over rather low, many times, 1.5k or less. This said, if this is merely to avoid peaks in the woofer's range, then as we discussed earlier, proper alignment of amplifier power ratings need to be adhered to, which I believe is what you're stating that you agree with. No?


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## bobolix (Jan 4, 2010)

Not exactly - and not so simply. Again, in general, the available peak output *acoustical* power in any band should be the same - and the peak electrical power should correspond to, assuming the efficiency relations. BTW, at the two way design, the efficiency of the appropriate tweeter is 3 to 6 dB above the efficiency of the woofer usually. The crossover frequency have not to be too low, indeed - it should be as high as possible and at least two times higher than the fs of the tweeter; the actual choice is given by the directional properties of the woofer, but, assuming the distortion, actual power rating and so, it should be not less than 2 kHz - 2,5 to 3,5 kHz is the reasonable choice in most cases. This is nothing new, of course. 

The another question is the sustained input power for the tweeter. Most of the hifi tweeters can withstand the long term average power about 5 watts maximum - no matter what is stated by the manufacturer. The peak power (short term - say 50 ms nonrepetitive) can be ten to twenty times higher. The amount of the total average acoustic power coming from the tweeter depends strongly of the crossover frequency and the signal character - it varies between 1 and 10 percent of the total acoustic power usually. The eventual peaks in the bass region come into account for the tweeter only if the crosover slope (and/or crossover frequency) is too low.

And, that all is only a small part of the problem ...


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## xyrium (Jul 28, 2008)

Thanks bobolix. I'm curious about a few areas in your response. Since many designers use a crossover point to avoid breakup in the mid or woofer's response (primarily in two ways), many designs are indeed crossed over at around 2k, and some even lower. While I doubt this is 2-3x the fs of the tweeter, I suppose it's a tradeoff in power handling. Unfortunately, this would preclude using only an active crossover without some level of EQing to correct those anomalies. Is that what you're suggesting, and that a passive xover is then a superior solution? 

Perhaps these are particular problems attributed to two way designs?


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## Drew Eckhardt (Oct 24, 2009)

bobolix said:


> Not exactly - and not so simply. Again, in general, the available peak output *acoustical* power in any band should be the same - and the peak electrical power should correspond to, assuming the efficiency relations. BTW, at the two way design, the efficiency of the appropriate tweeter is 3 to 6 dB above the efficiency of the woofer usually. The crossover frequency have not to be too low, indeed - it should be as high as possible and at least two times higher than the fs of the tweeter; the actual choice is given by the directional properties of the woofer, but, assuming the distortion, actual power rating and so, it should be not less than 2 kHz - 2,5 to 3,5 kHz is the reasonable choice in most cases. This is nothing new, of course.


Typical cross-over frequencies often result in unnatural sound due to the abrupt broadening of horizontal polar response and the power/vertical polar response dips from driver spacing, especially in 2-ways. 

1500Hz works great on a beefy 1" dome tweeter like the Seas T25CF002 (fs 500Hz) with peaks over 105dB, allows for a large mid-bass, and keeps frequencies which would stimulate cone resonances from the second and third harmonics out of the mid-bass. (Linkwitz Orion at 1440Hz, Seas Trym at 1600Hz)

1Khz works great on the Aura NSW2 (fs 250Hz) used as a mid-tweeter (Linkwitz Pluto). Output level on the original Pluto is limited by the mid-bass; in Pluto+ the Aura probably becomes the limiting factor although its enough for most people's casual listening leels.

500Hz reportedly works well on some large wave-guide + compression driver systems.

Where driver resonance is too close to your desired cross-over point, its filter can provide a pair of zeroes to eliminate the driver's natural resonance. A biquad will do that and provide the first two poles of its high-pass, with both analog (aka Linkwitz Transform) and digital (IIR) realizations possible.



> The amount of the total average acoustic power coming from the tweeter depends strongly of the crossover frequency and the signal character - it varies between 1 and 10 percent of the total acoustic power usually.


If you have your music as .wav files it's easy to turn an approximation of your proposed cross-over functions into IIR filters and mate the two in Octave (which is free) or Matlab (where students may have a license from their university) and see what results from real-world examples.


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## brandon75173 (Dec 13, 2009)

JerryLove said:


> Remember, the DCX2496 is balanced in/out: so you will either need to convert that, or run balanced pre and amps (I recommend the Yamaha pro line of amps).


Thats the bad thing about trying to meld the pro audio stuff with a home use. I have an amp, BFD, and pre-amp (balance box) on top of one of my subs. It took all of that to get the balanced amp (or in this case X-over) to function properly. I was looking for an active crossover using unbalanced input/output for my 2.1 computer build, but there are very few options. Some chinese junk as usual.


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## xyrium (Jul 28, 2008)

So, you have a preamp feeding your BFD? I go straight from an Emu 1616M (soundcard) to an amp...done. However, when I stick a crossover in there, it will simply be Emu>xover>amp. Rane and Ashly both make good stuff, and I believe Rane still has stuff made in the US. dbx also makes some nice gear, though I believe mostly made in Asia. 

If you must you unba;lanced connections, maybe you could come up with a 12V power source and use some of the Audiocontrol gear made for mobile audio. From my recollection, they made very solid equipment, though it was over 15 years ago when I last touched that stuff.


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## brandon75173 (Dec 13, 2009)

Yeah the preamp turns my unbalanced (and very low level) RCA sub pre out from the receiver into a balanced and gained signal. Running the pre out direct to the amp is way to low of a signal. Running direct to the BFD can achieve the right level with the gain turned basically to max. By doing that you end up with a wicked over gain hum. Its the only way I have been able to get high enough level without the hum. I am still new to this but the dynamics seem to make sense as I play with them. Thats why in basic systems it is so nice to have the more user friendly unbalanced low level inputs IMO. Of course as long as there is minimal sacrifice.


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## xyrium (Jul 28, 2008)

That's a tough one. For me, there's nothing better than balanced connectors. I get dead silent black backgrounds. No ground loops, no interference, etc. Are you sure the BFD can't accept unbalanced connections? If it has 1/4" jack inputs, you might be able to use them with only two conductors for unbalanced. My 1616M is actually switchable, which is nice. Of course, true balanced uses transformers at each end. However, even the servo stuff still provides the benefits of noise and hum cancelling. 

I say, switch to using a PC based system, grab yourself a nice audio card with balanced outputs, and roll from there (PCI, USB, or Firewire, and don't let anyone tell yuo the PCI based stuff is noisy. If they do, tell them to show you measurements...). The DVD or CD Rom on the PC, using the unbelievably outstanding DACs found on almost any midrange audio card these days, will outperform some of the best audiophile CDPs. Nothing like true error correction on the fly!


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## brandon75173 (Dec 13, 2009)

xyrium said:


> That's a tough one. For me, there's nothing better than balanced connectors. I get dead silent black backgrounds. No ground loops, no interference, etc. Are you sure the BFD can't accept unbalanced connections? If it has 1/4" jack inputs, you might be able to use them with only two conductors for unbalanced. My 1616M is actually switchable, which is nice. Of course, true balanced uses transformers at each end. However, even the servo stuff still provides the benefits of noise and hum cancelling.
> 
> I say, switch to using a PC based system, grab yourself a nice audio card with balanced outputs, and roll from there (PCI, USB, or Firewire, and don't let anyone tell yuo the PCI based stuff is noisy. If they do, tell them to show you measurements...). The DVD or CD Rom on the PC, using the unbelievably outstanding DACs found on almost any midrange audio card these days, will outperform some of the best audiophile CDPs. Nothing like true error correction on the fly!


Sounds good on paper, but the traditional receiver route in the living area is how it has to be for me right now, by choice of function. And the BFD does accept 1/4", which is how I can run an RCA--->1/4'' cable direct from the receiver to the BFD. Neither here nor there really. Just trying to make the point to anyone reading this that its not plug and play to run a low level unbalanced signal to a balanced 1/4" or XLR connection. Despite the fact that RCA to basically any cable connection is readily available.


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## xyrium (Jul 28, 2008)

Got it. It is certainly unfortunate, but at least you made it work. Nice job finding a workaround!


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## boardpile (Nov 3, 2009)

brandon75173 said:


> Thats the bad thing about trying to meld the pro audio stuff with a home use. I have an amp, BFD, and pre-amp (balance box) on top of one of my subs. It took all of that to get the balanced amp (or in this case X-over) to function properly. I was looking for an active crossover using unbalanced input/output for my 2.1 computer build, but there are very few options. Some chinese junk as usual.


I have the same setup for my subs. Receiver to a MIC2000 pre-amp to an EP4000. I get no hums, pops, and the gain on the EP is only about a third of the way up. Does the trick.


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## brandon75173 (Dec 13, 2009)

Run your gain 100% on the EP by everything I have seen from manufacturer and informed users. I have the BFD inline for the EQ value.


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## bjs (Jun 12, 2008)

lsiberian said:


> I'd prefer to use a DCX 2496. It's the amping that introduces cost issues for me.


Suggest a cheap receiver which has external decoder inputs.

I bought two Insignia Receivers from Best Buy. $300 Canadian for 10 channels with 100 watts per channel. The volume control works as a nice input attenuator too.


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## reed.hannebaum (Apr 21, 2006)

In my system I have an active xover feeding Paradigm Studio 20's for my front L/R speakers and stereo subs. I have experimented with the Paradigm X-30, dbx223, Behringer CX2310, and the NHT-X2 Xover's. The X-30 produces hiss and cannot accomodate stereo subs. the dbx223 xover point cannot be adjusted below 70Hz. The Cx2310 is a good unit but the controls are difficult to adjust accurately and there is no phase adjustment. The NHT unit is by far the best unit I have tested and the most expensive. It is very quiet and very versital. Like the Marchand xovers (highly regarded and expensive) it only has discreet xover points for the main speakers. While this may seem to be a detriment, this helps to minimize the number of opamps in the signal path producing less noise and distortion.


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## reed.hannebaum (Apr 21, 2006)

brandon75173 said:


> Yeah the preamp turns my unbalanced (and very low level) RCA sub pre out from the receiver into a balanced and gained signal. Running the pre out direct to the amp is way to low of a signal. Running direct to the BFD can achieve the right level with the gain turned basically to max. By doing that you end up with a wicked over gain hum. Its the only way I have been able to get high enough level without the hum. I am still new to this but the dynamics seem to make sense as I play with them. Thats why in basic systems it is so nice to have the more user friendly unbalanced low level inputs IMO. Of course as long as there is minimal sacrifice.


Rane, as I am sure you know, is a well respected pro audio gear mfg. They have written a very informative white paper on this topic.

http://www.rane.com/note110.html


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## xyrium (Jul 28, 2008)

Thanks Reed. I have a dbx 260 and a Crown CDi1000 on order. I will probably be taking Zaph's ZRT and making it active with these items, in addition to my current Parasound A23. The A23 will be used on the highs. While way overpowered for these drivers, I hope to at least use these cautiously to implement an active system. 

Do you know of any white papers on how to properly achieve this? My main concern is going ot be how I am going to achieve LF/HF amplitude balance between the woofer and tweeter. I plan to start with Zaph's passive xover frequency of 1.7kHz. Therefore, what frequencies would you say I should use to blanace the amplitude of the associated drivers?


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## reed.hannebaum (Apr 21, 2006)

Wow, that's going to be quite a system.

The way I blended everything was using REW. It's a recursive process; adjusting relative amplitude, adjusting xover pt., then re-adjusting amplitude. I feel these are the fundimental parameters. Then after that you can do equalization.


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## xyrium (Jul 28, 2008)

Thanks Reed. Yes, it has the potential for greatness. I love Zaph's work, he's a great designer. If it wasn't for his ideas, I'd probably be still be using an old pair of B&W DM303s. However, i figured active may take these drivers to the next level. The Crown wil eventually be used for subwoofer duty once I decide on one (considering a Seas L26ROY). All cabs will be sealed, in order to at least start off with decent group delay function. The PEQs on the driverack will allow for something like 4 on each input and 3 on each output (or vv), and the xovers go from 0 to higher than my hearing can perceive. 

I've used REW before, and I also hope to eventually use HOLMimpulse to do comparison measurements. So, I'll start a new thread once I've begun the process. Thanks for the tips!

Paul


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## reed.hannebaum (Apr 21, 2006)

As I am sure you are aware, when using PEQ's; get by with the lest number and amount of equalization that you can. Every time you equalize you introduce phase distortion. This may not be a big deal except around an xover pt. You want to preserve the advantages of your Lindquist-Riley crossover.


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## xyrium (Jul 28, 2008)

Thanks again Reed. I am certainly hoping to avoid much EQing. There are only one or two areas that I believe will actually require it, but I'll know better once I get them active and take measurements. If it turns out that I'm doing more harm than good, I'll back out and reapply the passives.

This said, I was also under the impression that if done in the digital domain, the phase shift/distortion would not apply. Is that inaccurate? 

Thanks!


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## reed.hannebaum (Apr 21, 2006)

xyrium said:


> Thanks again Reed. I am certainly hoping to avoid much EQing. There are only one or two areas that I believe will actually require it, but I'll know better once I get them active and take measurements. If it turns out that I'm doing more harm than good, I'll back out and reapply the passives.
> 
> This said, I was also under the impression that if done in the digital domain, the phase shift/distortion would not apply. Is that inaccurate?
> 
> Thanks!


A Butterworth filter is defined by it's Transfer Function. Inherent to this function is frequency dependent phase error. Now whether you choose to model this function with analog components or to use a Z transform and model it in the digital domain, the phase error still remains.


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## Paul P (Dec 5, 2009)

I understand that one of the benefits of active crossovers is they can eliminate the 
phase shifting of an passive crossover but is there any guarantee that the separate 
amps used with an active crossover will each maintain the correct phase ?

Paul P


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## reed.hannebaum (Apr 21, 2006)

This is an excellent point. Every amplifier has some phase shift, but very few offer this information in their specifications. Since this shift is frequency dependent, it will vary at different XO points. 

An active cross over can eliminate phase shifts if designed to do so. This is what the Lindquist-Riley type of cross over does. It is essentially two cascaded Butterworth filters that brings your tweeter and midrange speakers into electrical phase alignment. Of course phase shift in your amplifiers as well as mechanical misalignment between the two speaker voice coils will offset this. Some speakers are designed with a slanted baffle in order to bring the tweeter and midrange speakers into mechanical alignment, but that still leaves the relative misalignment in the two amplifiers. By looking at the amplifier outputs on an O-Scope, you could measure what this is at the XO point and adjust the phase control (if you have one) on your cross over to correct for this. Very few people ever bother with this and this would only be correct at the XO point. If the two amplifiers are from the same manufacturer and especially if the are the same model, then the phase shift in the two amps will be the same and so no relative phase shift.


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## xyrium (Jul 28, 2008)

Hmm, it's beginning to sound more difficult to implement than a passive xover... I suppose the manufacturers of Pro speakers (the powered stuff like Kelin and Hummel, etc.) really do a lot of homework before distributing a product. Thanks for everyone's contribution to this thread. I'm going to read some stuff on the ESP pages, but if anyone has a link on how to properly implement this, I'd truly appreciate it.


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## Lucky7! (Jan 7, 2008)

xyrium said:


> Hmm, it's beginning to sound more difficult to implement than a passive xover... I suppose the manufacturers of Pro speakers (the powered stuff like Kelin and Hummel, etc.) really do a lot of homework before distributing a product. Thanks for everyone's contribution to this thread. I'm going to read some stuff on the ESP pages, but if anyone has a link on how to properly implement this, I'd truly appreciate it.


Developing an active system is similar to a passive; measure, adjust, measure, adjust until you get the resukts you want.

Actives are much easier to do in many ways, as changing the xover F can simply be a couple of 2c resistors or small cheap caps. Adding notches or EQ in an analogue active xover, especially a commercial product can add some complexities, but if you take the time to learn some analogue electronics, not hard even for a relatively inexperienced DIYer to do. Start with something like Elliott's boards and you can add further processing if you choose.

Personally, except for my Unity's which already have a developed passive MF/HF xover, I'm not even bothering with passive in the current builds, nor have I bothered with them for about 8 years. I can dial in my DCX's to do what I want in minutes and add delay if needed.


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## Kevin Haskins (Nov 14, 2007)

I agree... if you design crossovers active are easier. For the average Joe who wants to slap a bunch of drivers together it won't work. Of course that doesn't work with passive crossovers either. ;-) 

Kevin Haskins
Exodus Audio


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## xyrium (Jul 28, 2008)

Thanks guys.

I suppose the hurdles of adjusting xover points are greatly diminished with infinitely variable active units. So, one has no need to changes any components as you would in a fixed design like the Marchand stuff. 

Hey "X", do you have any of your designs posted somewhere?


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## Kevin Haskins (Nov 14, 2007)

xyrium said:


> Thanks guys.
> 
> I suppose the hurdles of adjusting xover points are greatly diminished with infinitely variable active units. So, one has no need to changes any components as you would in a fixed design like the Marchand stuff.
> 
> Hey "X", do you have any of your designs posted somewhere?


Here is the best solution I've found. DSPs allow for all the flexibility you will ever need.

http://www.hypex.nl/docs/AS2.100/Manual AS2.100 V1.2.pdf

http://www.hypex.nl/docs/AS2.100/HypexFilterDesignerv1.3.zip

I stock these but don't have them on the web site yet. It does not alleviate the need to take good measurements and do good design but it allows for a nearly infinite range of adjustabity for playing around with voicing a design. You also can run a couple notches on the bass to deal with room issues. 

I have a pair installed on my personal loudspeakers and love them. 

Kevin Haskins
Exodus Audio


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## xyrium (Jul 28, 2008)

Very nice indeed. However, I'musing a dbx Driverack for this purpose:

http://www.dbxpro.com/260/index.php

It's similar to the Behringer stuff every seems to be using. Therefore, the amplification will be external to the xover itself.


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## Lucky7! (Jan 7, 2008)

xyrium said:


> Hey "X", do you have any of your designs posted somewhere?


When it's finished I'll post it all as a fait accompli similar to Paul W did with his Octagon system. I know what I want and how to do it, and just need to find the cash and time to complete.


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## xyrium (Jul 28, 2008)

Oh good lord! Wow, that's some setup he has going there. In the images, it appears that he's doing both passive and active. Hmm, how does one keep phase intact with all of that going on?!?! Either way, he seems happy, so I get the feeling that a few tweaks with the DR 260 won't impair much. Good luck with your implementation though. You certainly will have your work cut out for you!


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## reed.hannebaum (Apr 21, 2006)

A9X said:


> When it's finished I'll post it all as a fait accompli similar to Paul W did with his Octagon system. I know what I want and how to do it, and just need to find the cash and time to complete.


Now this is an exceptionally well engineered system. Very impressive. Obviously a lot of thought, research, time, and money went into this project. There are few Home systems that give me a wow, but this is in that catagory. Jeremy Kipnis' system is another obvious candidate but I am not so sure his system is as well engineered.


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## lsiberian (Mar 24, 2009)

I plan to use a cx2310 myself on each side. 

I still have 4 more channels of amps to buy, but that's a minor detail.


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## Lucky7! (Jan 7, 2008)

reed.hannebaum said:


> Now this is an exceptionally well engineered system. Very impressive. Obviously a lot of thought, research, time, and money went into this project. There are few Home systems that give me a wow, but this is in that catagory.


I was very impressed when I saw it too, and I'm using it as a reference for the sort of performance _leve_l I'd like to achieve, even if I'm going to go about it differently, and this is part of the reluctance for posting a lot about my gear before then. I love how he seems to have set a design and performance goal for everything and then systematically looked for ways to achieve that until he got the result he wanted. I'm basing my goals on what I'd had/designed/built in the past as well as other people's systems, especially two 2ch systems I've heard in the last year or so. If I can make it as good as both of them (combined as a mixed 2CH/HT), I'll be well pleased.

I have the limitation of an apartment dweller on some aspects of the system, such as not being able to change the room, ultimate SPL and bass levels etc, but have designed it so I can transplant it back to my home when I return there in a few years, but I might need a few more subs then because the living room is huge. My biggest handicap is I'm a really poor woodworker, as evidenced by the big pile of plywood scrap I made last week.



reed.hannebaum said:


> Jeremy Kipnis' system is another obvious candidate but I am not so sure his system is as well engineered.


Sorry, here I don't agree at all. The Kipnis system reeks of "showoff my toys and money" rather than a well engineered project. Even if I had the money to design a system in a room that large, I'd do it very, very differently and it would cost a fraction of what his did.


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