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JL Sargent

Crossovers, driver timing with active vs passive?

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I know when using active crossovers that electronic delay or driver placement can be considered. How do passive crossovers handle this, if at all?

I think I found my answer: sfogg wrote: "Nope. The drivers are out of alignment. Like most things it is a tradeoff. The horns in that layout with the passives basically prevent you from being time aligned while on the flip side you get the distortion/dynamic benefits of the horns. Some are willing to make that tradeoff, some aren't."

So if the above statement is correct for all Klipsch Heritage speakers then certainly an alignment impovement could be made. But is this even something the average person can hear? Interesting.

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Passive crossovers cannot compensate for driver offset. That is the reason that many speakers have a sloping front on their cabinets - you have to move the drivers for time alignment. Active crossovers with delays on the outputs do this electronically.

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From what I've read, I'm under the impression that they can't... unless you physically align the drivers. This is why some feel there is a benefit to active crossovers. There are others who feel the benefits an active crossover can get you are not worth the "electronics cost" when compared to a simple crossover.

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Coytee, I know you have Jubilees and I think you made some Cornscala type speakers. Have you played with time alignment on those setups?

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You can eliminate the issue altogether by eliminating the overlap between drivers..........using an extreme slope passive crossover as opposed to using an active crossover, digital DSP unit, more amps, etc. If there is no overlap between the drviers the time alignment issue goes away.

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If there is no overlap between the drviers the time alignment issue goes away.


That's true, unless a note coming from one driver is meant to come at the same time as a different note from another driver. In that case, time-alignment will give a tighter and more realistic sound. It's not obvious with every tune, but with some tunes you can really hear the difference when the delay is correctly set.

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I had an active system with the fancy DSP, delays, crossover, pro amps, etc. I got rid of it because it didn't sound as good as what I have now. In every comparison test I ever heard, the passive solution always sounded better to me. Some others in those same tests felt the active solution sounded better. So who knows. I will say this though. My hats off to the folks who get the active solution right. It's a walk across Texas in my opinion and requires a very careful choice of equipment matching. I know a few have done it and are satisified and I also know otheres that are on a continual search for the right combination and really have not got it totally right yet.



You can make a case for the technical correctness of the DSP and delays.......but implementing it correctly takes skill and produces many headaches. Read some of the posts of the different types of problems people have. All I was saying is that you can avoid all that by using the extreme slope passive technique and wind up with excellent sound in a MUCH simpler solution.



Islander, I have no idea what you are talking about with regard to the notes and different drivers. ;)

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I know you have Jubilees

Correct

I think you made some Cornscala type speakers

Incorrect, you're mistaking me with someone else here [:P]

Have you played with time alignment on those setups?

I'm using the Dx38 so with regard to the Jubilees, yes, I'm using some alignment. If memory serves me, when JC and Mark (above) were here, I attempted to take the delay OUT of the system to hear what the difference would be. Presuming I in fact, did it correctly, I don't think any of the three of us heard any real difference. I don't mean to speak for them but I think that was the conclusion (again, with the presumption that I didn't screw it up!)

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Islander, I have no idea what you are talking about with regard to the notes and different drivers. ;)


What I mean is when a bass line is keeping time with a treble line in a piece of music. If the longer bass horn causes the bass beat to arrive a bit later than the treble beat, it won't sound as "right" as it would if the drivers were time-aligned.

The difference is not huge and it's not evident on every piece of music, but it definitely can be heard. Doc Who has done some experimentation with easily adjustable delay and says it's easy to hear once you know what in-synch and out-of-synch drivers sound like.

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Where I can hear a time alignment issue in my system even with the ESNs is with a test CD I have that has a clicking and repetitive percussion track. It almost takes a trained ear to notice but you can hear it at times. Barely noticeable though.

In a normal music situation I never hear a time alignment issue. Especially with room reflections and the ESNs it is next to impossible to hear any issues like that.

I do understand what you were talking about now. Is there a popular or specific song that has the type of passage you mention so I can give it a try?

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Looking at these speaker designs I can see where the folded horn is at a real disadvantage as far as timing goes. But a cornwalls 15" direct driver and its midhorn are probably very close timing wise. I was all about going active xovers and aligning the drivers. Now I'm not so sure its even worth doing since 99% of these speakers are not aligned and 99% of the users don't even notice or care. Its kind of a bummer really. IGNORANCE is bliss! Kinda like the relationship between K55 and K77 drivers. According to my studies the K77 is about 1/2 a good tweeter and the K55 is just a so so mid driver. I have not listened to all the offerings out there but it does seem there are upgrades available and reasonably cheap.

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From what I've read, I'm under the impression that they can't... unless you physically align the drivers. This is why some feel there is a benefit to active crossovers. There are others who feel the benefits an active crossover can get you are not worth the "electronics cost" when compared to a simple crossover.

I have my voice coils physically aligned to within 1/8th wave at Xover. I use all single components (1st order). It is the simplest and most musical sounding, with minimal "group delay" (like what you get with 4th order passives)...........but I have to go 4-way with efficiency and polar matching to avoid any kind of EQ (took over a year to do it right), and that is just fine by me as I don't get why people want to EQ the heck out speakers just to keep it 2-way.................different strokes.

I will try Active shortly, but I like what I have so well, I'm not inclined to mess with it right now.

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"Passive crossovers cannot compensate for driver offset. "

If the woofer is shallower than the HF horn, a passive allpass delay will correct the time response.

Posted Image

Balanced type recommended for DIY as the unbalanced type requires a bifilar inductor.

(as used in time aligned co-ax monitors and some B&W speakers)

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JL,

No need to mess with the corns. Just not worth it. A large effort and cost with little payback and a definite possibility that it won't sound as good as it does now. Basically an experiment. Plus, a cheaply done active system is just not going to sound audiophile grade. You would need to spend some decent bucks for sure.

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Plus, a cheaply done active system is just not going to sound audiophile grade. You would need to spend some decent bucks for sure.

Exactly, there's a reason why most true professional active crossovers/processors cost more than a good pair of Khorns.

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Thanks for the insight and knowledge about it guys. It'ss funny how our perception about what is and is not seems to always change when it comes to speakers. It's said we live our lives in circles and I keep circling around back to the first decent pair of speakers I ever bought. I pair of Technics SB 2680s if I remember right. I've still got em and they sure did sound good last time I listened to them, circling back around.

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In a normal music situation I never hear a time alignment issue. Especially with room reflections and the ESNs it is next to impossible to hear any issues like that.

I do understand what you were talking about now. Is there a popular or specific song that has the type of passage you mention so I can give it a try?


Try Leonard Cohen's Take This Waltz. It has a deep bass organ line that keeps time with the vocal. Un-aligned, it sounds fine, but with time-aligned drivers, it sounds a bit tighter and more "right". It's a subtle difference, but I can hear it.

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I find the time-alignment most noticeable with percussive sounds - especially snare and toms. A legato violin solo is gonna be much less noticeable (if at all). It's also noticeable when listening to very complicated sections of music - like when there are a lot of instruments all playing at the some time - but that's really difficult to adjust by ear. I think part of the ambiguity is the number of mics used and the lack of phase coherancy in the bleedover.

The differences are certainly subtle, but then so are a lot of the tweaks so often discussed.

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I do understand what you were talking about now. Is there a popular or specific song that has the type of passage you mention so I can give it a try?

Funeral For A Friend, from Goodbye Yellow Brick Road - Elton John. The snare drum sounds distant, the transients sound smeared when no delay is applied. Delaying the mid horn to the bass horn makes the snare come alive.

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