Active Crossovers

[djk]

"Of course, I may be full of it....."

I won't disagree with you on that one.

[Coytee]

Maybe your headphones suck [6] (couldn't resist)

I would have expected you to suggest that in terms of the magic of stereo, (holographic sound experience) that your headphones smoked your Khorns but, for the dynamics of the sound, your Khorns clearly stomp on your headphones. With headphones, you really have no room issues, perfect symmetry (unless your head is shaped weird like mine [:|]) and as you say, little or no signal alignment issues.

I would have expected you to say that you're surprised everyone isn't out chasing the holographic experience of headphones, with their speakers.... I would think that is the ultimate goal for some people?

Let me change the equation a little bit (at the risk of exposing more of my ignorance)

You've been to a cave or somewhere, and heard someone clap their hands....and heard an echo a bit later, right? For simple illustration, could we suggest that the echo is the same sound as the original clap however, it's not signal aligned since it gets to your ears later?

Here's where I'm going.... if you have two drivers sharing some bandwidth between them, they are both going to put energy out into the room in that shared bandwidth such that I'd ask the question... which sound is the primary sound and which one should be ignored? Is the rimshot coming from the upper frequencies of your basshorn the "real" sound and the K400 reproducing that same sound in its lower region an artifact or is the K400 making the 'real' sound and the woofer creating the artifact?

Al's extreme slope networks try to help there in that, they minimize the overlap of the drivers so they minimize the sharing of the same frequencies coming from different drivers. His ES networks (in my experience, therefore opinion) require more distance to meld together because each driver is more isolated than the more simple crossovers. They will also sound better at larger volumes since this same overlap is minimized. Kind of a situation of which compromise ballpark do you want to play in?

Back to the point... If both drivers create the sound in the same instant and it hits your ears in the same instant then you won't necessarily know there is a difference. What if however, one of those drivers (midhorn) creates that sound that hits your ears and because your bass horn is 6 feet longer, the same sound coming from it takes a couple milliseconds longer to reach you. I would suggest that with enough delay, that would start to sound like an echo and you'd be annoyed by it. If you could delay the midhorn such that the same sound (say, a rim shot) hit your ears at the same instant then all the sudden, the speaker will have more clarity and intelligibility. It would come into focus quicker which would be defined as closer. It would have more of a "one voice" rather than three smaller voices singing in unison.

If I still had my Khorns and you came over, I could show you this in an instant. Took me a year to figure it out but now I get it.

[Rudy81]

The headphone discussion is interesting because it demonstrates what people like about the sound The biggest difference between my headphones and the Khorns, is that with my headphones, the music is happening "inside my head" and with my Khorns, the performance is in front and around me....much like a real concert or symphony. Yes, my headphones do suck, nothing expensive or fancy, but they sound good enough for they gym while I try to keep age and weight at bay.

I can also see the problem with the ALK ES network, although I have never heard them. But the need to driver align those seems very important since the drivers are truly separate now. I suspect this is why pro setups do what they do with active crossovers. Their speaker arrays are so large and generally separated by notable distances....hence a big need to 'meld' the sound of the drivers to create a united wavefront. The differences will be much less noticeable in a single speaker, like a Khorn.

I am in no way disagreeing with you guys, I'm just trying to cement the concepts in my mind and learn enough to be able to weigh the pro's and con's of making such a change. The change has got to be worth the cost and setup or there is no point in doing it.

It will be interesting to see how this works in pratice in my room with my speakers. Hopefully I won't blow my drivers or amps up. Nothing like knowing enough to be dangerous. []

[Rudy81]

Another thought is....what about electrostatic speakers? They should be superb at driver alignment, right? Yet, here we all are, in love with that Klipsch sound.

[dtel]

I know very little about this but I think the "time alignment" part of active crossovers are by far not what is the best part, it's everything else you can do. I use the Ev Dx as an active crossover and I do not even have the time alignment set for the K402. It is such a small difference I have been told by a few people I probably could not even hear the difference, and that's between a MWM and K402.

Coytee you claim to not know much about this stuff but you have me beat, I have not even tried to make ANY changes in the DX, I am scared I will change something and not be able to get it back.[:$]

I do need to learn how to make adjustments just to see what they sounds like ?

[Coytee]

what about electrostatic speakers? They should be superb at driver alignment, right? Yet, here we all are, in love with that Klipsch sound

They sound great for what they do, but when was the last time you had an electrostatic speaker kick you in the gut?

[Coytee]

Coytee you claim to not know much about this stuff but you have me beat

Pfffft... you know me.... talk fast, run faster!

[Z]..........................................................

[Rudy81]

what about electrostatic speakers? They should be superb at driver alignment, right? Yet, here we all are, in love with that Klipsch sound

They sound great for what they do, but when was the last time you had an electrostatic speaker kick you in the gut?

I totally agree. My only point is that driver alingment can't be that big a deal, otherwise everyone would own planar speakers. It seems the bigger issue is the potential problems caused by driver to driver frequency interference near the crossover frequency points. I am beginning to think this may be the best reason to go active. You will never have to buy another crossover. You can hook the DX38 to anything and get proper crossover settings once you learn how.

So, my current goal is to set the Khorns up with a 'steep slope' crossover vs. the current ALK Universal. That would take care of the problems between drivers. I could later use it if I went with a Jub bass bin etc. This seems to be the real cost effectiveness of the active crossover. When compared to the ES crossovers, the DC-One or DX38 are relatively inexpensive....except for the amplification issue of course.

BTW, thank you for all your help and time with this issue. I really enjoy learning about all these topics. I have found this thread, which is similar in topic and rather in-depth as well. http://forums.klipsch.com/forums/p/60007/587908.aspx#587908

Edit to add this gem: http://forums.klipsch.com/forums/p/84837/852652.aspx#852652

[dtel]

Coytee you claim to not know much about this stuff but you have me beat

Pfffft... you know me.... talk fast, run faster!

..........................................................

[bs] We know your a good guy, we just DON'T want that rumor floating around here. [8-)]

[Mike Dubay]

"Pass over the entry level Chinese stuff - they won't sound very good for hifi. Something like Ashly's XR series (I think - their step-up series) sounds much better. If you are in a decent sized town, you could probably rent one from a PA house for very little money to see what you think."

So would the XR-1001, which is a simple stereo 2 channel be recommended?

Here is a link to the Ashley web page.

http://www.ashly.com/product/xr-series.htm

I will investigate if I could rent a unit for a short term test.

[ben.]

"Pass over the entry level Chinese stuff - they won't sound very good for hifi. Something like Ashly's XR series (I think - their step-up series) sounds much better. If you are in a decent sized town, you could probably rent one from a PA house for very little money to see what you think."

So would the XR-1001, which is a simple stereo 2 channel be recommended?

Here is a link to the Ashley web page.

http://www.ashly.com/product/xr-series.htm

I will investigate if I could rent a unit for a short term test.

Yeah, if you need a two-way. Those are the ones I was thinking of. There's a nice feature that allows you to control the response around the crossover frequencies. Really, anything decent will allow you to get your feet wet.

Big picture? There's a lot of strange logic going on here. Electrostatics? Well, there's a lot more significant differences that the lack of a crossover in that comparison.

Time alignment does make a difference. The question is does it make a difference that is noticeable to you and matters to you? Time alignment affects the phase relationship of the two associated frequncy bands, which will in turn affect the frequency response where frequency bands overlap. Steep slopes reduce the number of frequencies with sigificant interaction - Al K has talked quite a bit about this if memeroy serves.

One thing to further confuse you is the fact that electronic time alignment is only complete at one point in space. Once the listener or measurement device is relocated from that point, the difference in arrival times changes from the original spot, and the previous calculation is no longer accurate. This is why acoustic/physical alignment is preffered. If you get the acoustic origins aligned in speaker design, less (or no) correction is required. Google away on Synergy or Unity Horn technology, and Tom Danley. This concept is even superior to coax designs.

[Rudy81]

ben: I don't understand why the driver alignment is good only for one point in space. In my mind's eye, once the sound leaves the speaker with all drivers 'time aligned' the sound should propagate in unison (barring room interference, of course). So, I would think that the sound would be 'aligned' for any location in the room. I guess that is not correct.

[DrWho]

So, what am I missing here? I certainly don't feel the driver aligned sound of my headphones is superior to my non-aligned Khorns.

Well I can think of a few things at play that would describe that difference...

• Perception of music playback with your khorns involves more than just your ears - there's a visceral sensation that is lacking with headphones.
• Turning your head when listening to speakers causes the focus to stay in the same spot in the room. Turning your head when listening on headphones keeps the sound at the same point relative to your head. We expect the focus to shift when our body moves so this distracts from the whole stereo image concept.
• Speakers in a room involve more than just the sound travelling to the listener. The sound is sprayed all over the place and arrives at the listener at various points in time creating a type of reverb effect that you don't get with headphones. Most recordings are layed down with the anticipation of some room interaction. You could always mix a recording to sound good on headphones, but then when played back on a normal system with speaekrs it will sound way overdone.
• In order to get true stereo imaging on headphones, you need to apply a transfer function that accounts for how your head affects off-axis sound that hits both ears. For instance, a sound off to the left will have more HF content in the left ear than in the right ear due to the shadowing effects of your head. The left sound also arrives in the right ear slightly delayed.

I would suggest that in light of all these variables (and I'm sure there might be more that I'm not bringing up), that time-alignment is compartively a small drop in the bucket.

[DrWho]

Another thought is....what about electrostatic speakers? They should be superb at driver alignment, right? Yet, here we all are, in love with that Klipsch sound.

Electrostatics sound extremely cohesive, but generally don't have a very good polar response and lack a bit in the dynamics department. You give up some of that cohesive sound by going to multi-way horn based systems. Adding in a bit of time-alignment gets some of that cohesion back (but not all of it). You're also limited by the distortion signatures being different between the various drive units.

[deafbykhorns]

Bryston makes a nice crossover and you can sometimes find a 90's vintage at a reasonable price.

http://www.stereophile.com/miscellaneous/594bryston/#

[ben.]

Nope. Try this simple experiment:

Place something at a fixed point in space. Let's call this the HF driver. Then, place something a couple feet behind and a little below the previous object. This will represent the MF driver.

Get yourself some tape and string. Tape one end of the string to the "HF driver" and stretch it forward - you can use your listening distance as the distance if you want a more representative test. Cut it at that length, leaving the end taped to the HF. Repeat this for the "MF driver", cutting the second string so that the end joins together exactly with the first string. The length of these strings represent the source-listener distance for each component. Note that they are different lengths. This is why each freqency band in most speakers require different delay settings when time aligning a speaker system.

Now, move from the point (in any direction) where the string ends join together exactly. Those strings' ends are no longer together, and sound would no longer arrive simultaneously from each driver.

Sound will propagate at the same speed, but the source-listener distance changes as you move about the listening area. This probably isn't all that significant in a home listening environment, but one could argue that the same holds true for the arrival differences inherent in most speakers with passive networks, especially considering the specifics of the relatively short horn path of the LaScala and the lessened effects of phase cancellation at low frequencies. When you get into a large scale PA situation with subs on the floor and mid/highs flown, the situation is quite different, even around 100Hz.

[Rudy81]

ben: I totally understand and agree with your experiment. Here is where I have a problem wrapping my brain around the issue. I am assuming that once we time align the drivers, either by physically superimposing one on top of the other or using electronics, the sound wave is 'united' as one as it leaves the front of the speaker. So, in my mind's eye, I don't see it as three points in space in a 3 way, but only as one since the wave is now 'aligned' as the sound leaves the speaker. That is why I said it should not matter where the listener is in the room. In this example, of course, we have to leave out the vertical alignment of the drivers as well as the room reflections. So, this is more of an esoteric discussion since it would be impossible unless you had a single driver that could go from 20Hz to 20kHz.

I have been under the impression that one of the goals of time alignment is to get the sound to arrive at the same time from the drivers, in other words, acting as if it were a single driver. (Ignoring the vertical alignment issues)

I had no idea this was such a complex issue.

[Rudy81]

DrWho: The amount of variable in this issue are huge! Frankly, I'm amazed speakers work as well as they do. I am certainly much more used to listening to speakers than I am headphones. So, I guess I am very partial to the soundfield of a room and the visceral impact of a speaker at reference levels vs. that of headphones.

[ben.]

ben: I totally understand and agree with your experiment. Here is where I have a problem wrapping my brain around the issue. I am assuming that once we time align the drivers, either by physically superimposing one on top of the other or using electronics, the sound wave is 'united' as one as it leaves the front of the speaker. So, in my mind's eye, I don't see it as three points in space in a 3 way, but only as one since the wave is now 'aligned' as the sound leaves the speaker. That is why I said it should not matter where the listener is in the room. In this example, of course, we have to leave out the vertical alignment of the drivers as well as the room reflections. So, this is more of an esoteric discussion since it would be impossible unless you had a single driver that could go from 20Hz to 20kHz.

I have been under the impression that one of the goals of time alignment is to get the sound to arrive at the same time from the drivers, in other words, acting as if it were a single driver. (Ignoring the vertical alignment issues)

I had no idea this was such a complex issue.

You don't unite the wave, it's still coming from three different sources. It's not like hot and cold water comig out of the tap as warm water. When electronically time aligning, you're simply trying to get the various sources to arrive together at a specific point in space. You are correct about the goals of time alignment, but it is more difficult to achieve than many think.

[Rudy81]

You don't unite the wave, it's still coming from three different sources. It's not like hot and cold water comig out of the tap as warm water. When electronically time aligning, you're simply trying to get the various sources to arrive together at a specific point in space. You are correct about the goals of time alignment, but it is more difficult to achieve than many think.

I am quickly learning just how difficult, if not impossible it would be to actually do this perfectly. Thanks.