Active Crossovers

[Rudy81]

Remember the function of the passive or active crossover is to ultimately provide an electrical voltage/phase corrective signal to the horn/driver. The horns/drivers only cares that this is done correctly regardless of how it is acheived. The ultimate goal is the acoustical response of the loudspeaker through the crossover region provided by the electrical drive to the drivers/horns.

The reality is the actual acoustical crossover frequencies could be very different than the electrical crossover set points. To acheive the same acoustical crossover response for the loudspeaker system when doing active v passive .

mike tn

Once again I'm going to have to show my utter ignorance. Are you saying that going active will require somehow making voltage and phase information input into the active crossover? I have yet to try this, so my knowledge is very minimal. I was under the impression that the basics are to connect the components and program the crossover to approximate crossover frequencies. This 'should' give an approximate starting point that won't damage the drivers. My plan had been to start there and work with slopes and then time changes.

Am I way off? What I don't want to do is blow a driver or damage an amplifier!

[DrWho]

"Classic" line arrays using direct radiators are inferior to horn loaded designs since that behavior is strictly linked to array length. Off axis response is a mess as well. Horn loaded designs are better. Horn loaded designs utilizing Synergy technology are even better. google around and you might start to see where I am coming from. Hop a plane to Buffalo and I'll prove it to you and buy you dinner afterwards.

Better depends on the application. The 2-way Jub outperforms the Synergy horn in regards to polar response. However, the design goals are very different. Could a synergy horn be modified to come closer or even better the Jub performance? Probably. But then the Jub could also be redesigned to have even better polars too. Given the footprint constraints of the Jubilee, I don't think one could design a Synergy horn that would yield better performance...although I would love to hear Danley's best attempt within that footprint.

I guess what I'm trying to say is that I see the two design approaches as different tools intended for slightly different purposes. In a home environment, we don't need 150dB SPL and a true stereo configuration really only has one sweet spot anyway...

[mikebse2a3]

Audyssey works in both the frequency and time domains, and does a heck of a lot of "voodoo" to the sound automatically

I've haven't experienced the Audyssey EQ. It would be very interesting to hear it's capabilities..!

mike tn

[DrWho]

Audyssey is just a fancy automatic parametric equalizer. To that extent, it's not doing any processing on the signal in the time-domain (except for the extent to which one can argue that EQ creates a phase rotation and therefore a different decay rate). The only thing it does in the time domain is it makes sure it's not trying to correct for frequency aberrations induced by reflections, and I think it might provide some decay rate weighting as well.

The more recent algorithms also try to identify where room gain sets in so that it doesn't completely EQ that out, and then they also employ a small rising response as you go lower in frequency to compensate for how we hear differently than a microphone...

There have been a lot of articles published describing what all these auto-eq features do...I'll see if I can't hunt a few of them down. It's an incredibly difficult process trying to emulate what an engineer would normally do with a pair of ears and lots of measuring equipment. I have also felt that much better results are possible when one tweaks in each filter setting manually than trying to rely on a purely automatic process. That's not to say that Audyssey is a bad thing, but it's not doing anything that an active xover and a competent user with enough tools couldn't do himself.

Btw, I'm pretty sure the most recent khorn crossovers include some EQ that tames down the khorn LF bloom at ~200Hz. That might be something to consider if one doesn't want to add extra complexity to the signal chain...

[mikebse2a3]

Once again I'm going to have to show my utter ignorance. Are you saying that going active will require somehow making voltage and phase information input into the active crossover? I have yet to try this, so my knowledge is very minimal. I was under the impression that the basics are to connect the components and program the crossover to approximate crossover frequencies. This 'should' give an approximate starting point that won't damage the drivers. My plan had been to start there and work with slopes and then time changes.

I'm saying to have an optimized design just picking a crossover point and slope isn't enough because the acoustical characteristics of the horn/driver affects these settings. You shouldn't damage any drivers starting out like you describe here.

I'm just warning that in most instances a person can't make a valid comparison between active or passive by just selecting a crossover frequency and programing that into the active unit when replacing a passive crossover. It's often much more complex than that if it's done correct.

Am I way off? What I don't want to do is blow a driver or damage an amplifier!

As far as amplifier damage you have no worry! As far as driver damage the main concern is that any amplifiers you use especially on the tweeter exhibts no turn on/off thumps and that any DC ofset on the outputs of the amplifiers are very low. This should be the case with any properly designed and functioning amplifier.

Rudy you are welcome to e-mail me through the forum and leave a phone number and times good to call you if you think I can be of some help to you.

mike tn

[Rudy81]

Rudy you are welcome to e-mail me through the forum and leave a phone number and times good to call you if you think I can be of some help to you.

mike tn

Mike, thank you very much and I will likely take you up on your offer when I am ready to go. One of the advantages I see in the active crossover is the ability to vary the slope and crossover frequency to suit the needs and capabilities of the system. For example, the JBL 2470 can go pretty high and the Eminence tweeter can go fairly low, so I will have the ability to select a suitable crossover point that takes advantage of the best sound production.

I certainly don't expect to be able to immediately duplicate what my ALK universal is doing, but I hope to eventually get close so that I can use that sound as a baseline. I will have to use something as a comparisson point.

As far as Audyssey, I don't have the pro version, but have the latest incarnation built into my Integra pre/pro. I was pretty sure I would never use it since I have held to the idea that messing with the audio signal is a no-no. Just for fun I ran an Audyssey setup routine and was shocked at how different the Khorns sounded. That led me to finding a way of measuring the audio in my room to see what kind of frequency response I was getting at my sitting position with and without Audyssey. After that enchanting learning curve, I was able to measure the purely direct Khorns and the Audyssey adjusted Khorns. What a difference! The direct Khorns have the famous 'hump' as well as a few other room induced anomalies. After Audyssey, I get a very 'flat' room response at my sitting position. I now cannot listen to the Khorns without Audyssey due to the bass hump, it sound too 'boomy' and affects my perception of other sounds. I have learned that modern technology is a good thing and that when properly done, changing the audio signal for the better is quite possible.

With movies, Audyssey does a fantastic job of setting volume levels etc. It also takes care of bass management for multi-channel as well as 2-channel plus a subwoofer. I use my RSW-15 from 45Hz down with the Khorns for 2-channel. Since I added the KPT-12-VB and KPT-1201 effects speakers, I am in home theater heaven. The KPT-12-VBs are amazing at creating a diffuse, yet 'realistic' sound field. I beleive Roy worked on those and they are amazing. That is one reason I keep wanting to hear the Jubilee in my room.

Needless to say, thanks for all the help you guys continue to provide to those of us who are less knowledgeable. Your ideas and suggestions are greatly appreciated.

[whatever55]

How about the McIntosh MEN220 ????

[jwc]

How about the McIntosh MEN220 ????

I'm gonna have that in my hand very soon.

jc

[seti]

How about the McIntosh MEN220 ????

I'm gonna have that in my hand very soon.

jc

Is that the new room equalizing device from McInstosh?

[whatever55]

Yes it is....

How soon ?

[ben.]

What you say about acoustic centers shifting with frequency doesn't make any sense and betrays a complete lack of understanding of the Synergy design. Please explain how I'm wrong here.

http://www.aes.org/e-lib/browse.cfm?elib=8194

There are other references to shifting acoustic centers in the literature...I spent a while searching, but couldn't find any of the specific articles that I originally read. However, all horns (to my knowledge) have shfiting acoustic centers with frequency and angle of measurement. It seems like it's not fully understood why this is the case, but my theory is that the wave velocity isn't the same everywhere in the horn...

As far as the synergy concept, take a look at how the polars bounce back and forth between the various drive units. Also, you should try doing your string experiment with all the different throats in the horn...

For the record, I'm not at all a fan of line arrays. However, the reason I brought it up is to point out that there is merit to calling the wavefront of a line array a planar wave when it in fact is not by an overly specific definition. There is criteria to where it behaves like a planar wavefront and under those conditions it is completely acceptable for an engineer to treat it as such. Engineering is not science...

I'm not trying to be nit-picky or dance around or whatever, but it is very difficult to communicate when we're not speaking the same language...

And also for the record, I'm also a fan of the synergy horn concept, but it doesn't change my opinion on time-alignment in a 2-way system...

Well, I'm not going to pay to download the paper so you can prove whatever point you are trying make. But I appreciate you actually reponded in somehwat of a linear fashion to the conversation. This: "This paper describes recent experiments regarding the acoustic center of a horn. It is generally believed that at low frequency a horn's acoustic center is located at the mouth and that it moves with increasing frequency toward the throat. A computer model and acoustic measurements are used to test this hypothesis on an array of similar horns." actually makes sense.

This actually doesn't contradict any arguments I've made, though. The imperfection of electronic time alignment in systems we are talking about remains. I'm not trying to plug Synergy technology - I brought it up as way to try to explain to you the shortcomings of electronic time alignment. Anyway, a situation where the acoustic centers shift towards the throat is a lot simpler to deal with than having acoustic centers that are much further apart to begin with, since the acoustic centers in a Synergy horn would be more or less on the same plane and therefore easily corrected even with properly designed passive network (since the corrections are in the phase domain). These corrections will remain more effective out in space, again since the acoustic centers are more or less on the same plane.

The situation become more complicated as one moves left to right with a more typical multi-element design, since the difference between arrival times changes as you move about, and the electronic time alignment falls apart as you do so. This is my point, which I think many have gotten but you for some reason continue to obfuscate with tangential arguments.

Yes, there are conditions where the output of a given line array will be behave as a unified wavefront, but the simple fact that you can change the angles between cabinets to change that behavior chould prove (even to an engineer) that the sound is not magically glued together. Again, semantics matter. Using the correct words allow normal human beings to communicate, not just guys with the same degrees. Again, put down the books, Mike.

[ben.]

"Classic" line arrays using direct radiators are inferior to horn loaded designs since that behavior is strictly linked to array length. Off axis response is a mess as well. Horn loaded designs are better. Horn loaded designs utilizing Synergy technology are even better. google around and you might start to see where I am coming from. Hop a plane to Buffalo and I'll prove it to you and buy you dinner afterwards.

Better depends on the application. The 2-way Jub outperforms the Synergy horn in regards to polar response. However, the design goals are very different. Could a synergy horn be modified to come closer or even better the Jub performance? Probably. But then the Jub could also be redesigned to have even better polars too. Given the footprint constraints of the Jubilee, I don't think one could design a Synergy horn that would yield better performance...although I would love to hear Danley's best attempt within that footprint.

I guess what I'm trying to say is that I see the two design approaches as different tools intended for slightly different purposes. In a home environment, we don't need 150dB SPL and a true stereo configuration really only has one sweet spot anyway...

Ok, again with the, "Better depends on the application." Then off on a tangent... What does the Jub/Synergy comparison have to with it? This little tangent you brought into the argument led to an equally tengential comparison of "Classic" direct-radiating line array with horn loaded designs. Then bringing up the footprint... stay with me for a few sentences at least! If I can find the energy to bother with it, I'll post a couple images from EASE-Focus that will show you why there is no application where a decent direct radiating line array outperforms a decent horn loaded system. Unless your application requires all kinds of energy sprayed around the off axis area, and also requires large amounts of acoustic energy be spent to get any kind of directivity in the first place. But hey, you brought it up...

Your last sentence I completely agree with - once again, I only brought up Synergy tech to illustrate a point. If you want to revisit any of my other challenges to your logic that you've yet to respond to, feel free.

[AltmanEars]

It is my understanding that the MEN220 is a "McIntoshized" Lyngdorf RP-1. McIntosh is downplaying the role of the room perfect software and in some communications has compared licensing RoomPerfect to licensing dolby... It should be pointed out that Mcintosh is a very conservative company with even more conservative customers. Customers who would scoff at using a Lyndorf RP1 are now very exited about the prospect of a Mcintosh box which is ostensibly the same...

There is a crossover built into the MEN220 and in the Lyngdorf. Originally this crossover was provided for bass management. Lyndorf believes the subwoofers should be stereo and against the walls. They (Lyngdorf) sell a sub which looks identical to a mini-jubilee bass bin.

I make these comments because with this type of technology the room correction software is everything and one wonders if Lyngdorf clients will have access to the new iterations of the RoomPerfect prior to Mcintosh clients.

[Rudy81]

Well, the process officially begins. Just picked up an EV DC-ONE for what I hope will end up being a good deal. Now I just need a multi-channel amp so I can liberate my HALO multi-channel for the experiment.

[Rudy81]

In my continuing search to improve things, I have been trying to listen to the Jubilee bass bin. I have listened two one genuine system and one clone system. Neither bass bin produced near the bass impact my Khorns produce, and no, my bass is not boosted in any way. In fact, Audyssey reduces my bass output.

Well, this is a first, I'm quoting myself. I realized this morning that the above statement is not totally correct. Although Audyssey does attenuate the overall bass response, in my room, the Multi-EQ function of Audyssey DOES boost bass at low volume levels. This is done automatically to compensate for the characteristics of human hearing. As volume is increased, the bass boost is decreased until there is no boost at reference level. I had forgotten about this feature when I made my statement.

So, I will only be able to tell how a Jub bass bin performs compared to my Khorns by putting a set in my room. Can anyone loan me a set? []

[Rudy81]

Have any of you used capacitors to protect your mid and hi drivers when working with active crossovers? I had read that when experimenting like this, one should use a 20 uF capacitor in series with the + lead of the mid driver and a 4.7 uF cap in series with the + lead of the tweeter. Do these values sound correct? Would I expect any detrimental sound issues by doing this?

I'm trying to get ahead of the game and order everything I will need to try the active crossover in my Khorns.

[Rudy81]

The following questions will show that a little knowledge can be dangerous. I am getting ready to order some capacitors to protect my drivers while I mess around with the active crossover. I had found the suggestion to use 20 uF for the mid driver and a 4.7 uF for the tweeter.

I subsequently found this page, http://www.carstereo.com/help/Articles.cfm?id=1 which allows me to calculate the crossover allowed for a given capacitor value. I am guessing I will start to cross the Khorn bass bin around 400 Hz. and would like to play around with various tweeter crossover frequencies. The JBL 2470 goes up to 12kHz IIRC and the Eminence tweeter goes down to around 2kHz.

My question is this: Aren't the suggested 20 uF and 4.7 uF caps going to limit my ability to do what I want??? I need help from you EE types since EE was not my strong suit in college. See, a little knowledge can be dangerous.

Thanks for your help.

[DrWho]

What does the Jub/Synergy comparison have to with it?

You said synergy horns are always better. I provided a case in the real world of a basic horn speaker that outperforms what is available in the synergy horn world. I brought up the footprint to acknowledge that they have two totally different design goals in mind and I would be curious to see what Danley could design in the footprint of the khorn since I think that's a good sweetspot for aesthetics.

You can save your energy on the line array data...I've probably already seen what you intend to show, and I'm not at all a fan of the line array approach anyway. You've missed my point twice about why I even brought them up in the first place.

[jwc]

It is my understanding that the MEN220 is a "McIntoshized" Lyngdorf RP-1. McIntosh is downplaying the role of the room perfect software and in some communications has compared licensing RoomPerfect to licensing dolby... It should be pointed out that Mcintosh is a very conservative company with even more conservative customers. Customers who would scoff at using a Lyndorf RP1 are now very exited about the prospect of a Mcintosh box which is ostensibly the same...

There is a crossover built into the MEN220 and in the Lyngdorf. Originally this crossover was provided for bass management. Lyndorf believes the subwoofers should be stereo and against the walls. They (Lyngdorf) sell a sub which looks identical to a mini-jubilee bass bin.

I make these comments because with this type of technology the room correction software is everything and one wonders if Lyngdorf clients will have access to the new iterations of the RoomPerfect prior to Mcintosh clients.

Yes....Will have 2 way XO capabilities...balanced or unbalanced.

Room Perfect

Set EQ options

and custom EQ options

time delay

Remote contol

Lyngdorf inside for sure..and other stuff

jc

[mikebse2a3]

Rudy81

One suggestion I've seen is choose a Fc one octave below your crossover frequency. (ie: 400hz crossover then choose 200hz to calculate your capacitor). You want your capacitor's impedance Xc to = your drivers impedance at 200hz in the above example.

It's assumed that you will also know the impedance of your driver around Fc. Since a drivers impedance varies with frequency unless you know it I guess your next best bet would be to use the nominal rating (ie: 8ohm, 16ohm...etc). This also assumes you are using amplifiers with low output impedances like solid state amplifiers typically have.

So you can use the calculator you found above until you narrow down the value you need.

If you intend to vary the crossover frequency by any substantial amount say between the Mid-Tweeter then you might want to pick up several different cap values for approximately the frequencies that you might want to try out.

This is the formula to calculate the capacitor value if you want it: C = 1,000,000 / (2pi) x (Fc) x (Xc)

So for example if you want a capacitor value for an Fc = 250hz and your driver impedance is 8ohm then:

C = 1,000,000 / (2 x 3.14159) x 250hz x (8 ohm)

C= 1,000,000 / (6.28318) x (250) x (8)

C = 1,000,000 / 12566.36

C = 79.577 mfd capacitor

Chose a standard value close ( ie: 80mfd ) to the calculated value because it's not that critical due to many variables.

Maybe someone with more experience will chime with any other protection methods that might be better but for expermenting this will definitly get you going.

mike tn