Why not horns?

Ditto to Weseixas!

I was just thinking the same thing about Duke's speakers.
Isn't more of a waveguide than a horn?

Unsound, ALL time coherent designers think/thought this. Vandersteen, Thiel, Johnson, etc.
It is the single measurement that most distinctly shows the output signal as it relates to time. And timing was the paramount issue for all of these guys.

an admitted naive observation from a bachelor........

Why is it that we need to figure out ways to get the wifes "out of town" whenever we want to have a little audiophile fun? It seems to me that they don't plan on ways to get the men out of town whenever they have their little parties. To the contrary, they plan the party and we pretty much go running! LOL! (Hmmmmm. wait a minute!.........)

Back to the thread.... Why not horns? Well, because they sound like horns. My friend has meticulously set up his Trios with 3 pairs of bass horns in a dedicated and purpose built room with every little trick and room correction you could think of.
Mighty mighty impressive dynamics. Sometimes feels like I can hear the nose hairs moving in the recording. But ultimately only fun for a little while. I always come away feeling as though I have listened to a well constructed parlor trick rather than a live musical event.

*shrug*

Okay, then let me put it this way.....
Between himself, myself, and at least one other professional there is 60+ years of collective experience in the overall set-up of that room and system.
I'm confident my own 20+ years of professional experience is enough to say that he has those horns as "optimized" as they will ever be.

And, yes, in this case three pairs of basshorns does come close. And I have the data to prove it.
Like I said, they are not full horns but they are horns non-the-less. Between the triple stack and the very high sensitivity of the 6 individual woofers per channel, well, I'd like anyone to show me a "horn" that goes all the way down to 20Hz thats better! (And fits inside even a generous listening room.)

Having heard many horn systems in all sorts of varying set-ups I would say that my friend has managed to optimize his to a far greater degree than any other. So I would say, yes, he has done what was "right".

The size of the amp on the basshorns has nothing to do with what they require. Incidentally, it's 2x 250watts. One for each 12in. driver.
And while it's not a true full horn it is neither a flared opening. But by the time you triple them up you've arrived at pretty much the same place, I would assume.

I know he loves them and has managed to produce the best sound I've ever heard in a horn. And I know many others who love horns. But it's just not for me I guess.

@ Herman, I should have looked up your system before trying to answer your posts. my apologies.
But if I may be so bold, apparently size and overwhelming a room is not such an issue for you! haha.

But I stand by my statement on the triple avantgarde basshorns. The cumulative length isnt quite like yours but the end result is probably the same. The overall sensitivity pretty much matches the other three horns, which is the point anyway. (right?)

Oh, and we tried the time alignment a LONG time ago. Big improvement, Yes, but still not my cup of tea in the end.

If you take 6 different drivers, unless they have perfectly linear transfer functions, they will all have slightly different responses. If they all have the same input signal their responses should smooth to a more linear response.
It may be to small to be audible which is why I stated that it MAY be argued to be better. But it doesn't change the fact that these differing nonlinear transfer functions should become more linear as a whole.
The reduction in distortions, which is what Weseixas picked up on, should have been a little more obvious.

"You are comparing 2 amplifiers that obviously have differences other than max power and saying it is definitely because they have more power. It seems you jump to a lot of conclusions."

Well, for starters, the output impedance was cut in half.

"Prez, so there is nothing you could possibly do to improve the sound of that system?"

At this time, no. But we are always searching.

"How do you figure the efficiency of the "basshorns" given it is an active system?"

Easy. You raise to volume to a specific SPL and then measure the output of the amplifier. The rest is just math.

Incidentally, I'm trying to give the benefit of the doubt but so far I'm not entirely certain you understand the full breadth of sensitivity and the ways to achieve it.
FWIW, a serious argument could be made that it is better to use 6 individual drivers to achieve the same sensitivity of just one and a huge horn due to the way the 6 different ones will average out their non-linearities.

Sorry, let me clarify one thing.......
The two 150watt amplifiers in question versus the one 75watt were simply monobloc versions of the same amplifier.
Identical in every way expect the fact that the monobloc has paralleled outputs.

How many different ways do I have to say this?
A) the fact that a speaker HAS a 250watt amplifier attached to it does not mean that it NEEDS 250 watts.
The reason for using this much is simple. (though arguable) The more power an amp has the greater it's power supply. The greater it's power supply the (usually) more linear it's first watt is. Read up on Nelson Pass and his theories for more on this subject.
For reference, this same guy with the Trios went from one 75 watt stereo amplifier to two 150 watt monos for just the top three horns. And it sounded better! Why, when he only needed 1watt?? For reasons OTHER than headroom.
One of the basic points of those little, low watt, SET amps is the linearity. But that linearity is not exclusive to low watt SETs. It just takes a whole lot more power supply (amoung other things) to make a bigger amp the same.
Trust me, I have all of the fun little tech toys to measure these beasts in every conceivable way. And the bottom line is that the sensitivity of three basshorns nearly matches that of the rest of the system. Period.

Second, I am not simply a casual, some of the time, listener with my friends system. We've been working on it together for about 10 years. He is retired and has the time and resources. I and a couple others have the expertise. So I say, yet again, I am fully confident that if there is a technology or any other way to make his horns sound better, we have explored it.

As far as time alignment goes, we've tried both electrical and physical. Trust me, we've tried it all.

Still don't like 'em long term!

@ Duke: I remember reading that same account of the guy who hated horns until that experience. I just can't place it.

But I disagree. I've heard everything that has gotten any press in the last 10 years and more. Some are better than others. But I maintain my ultimate conclusion. All horns sound like horns to some degree or another. Some are just better at hiding the fact.

But like we "horn haters" have said over and over..... To each his own. Its all a balance of compromises, no matter how you look at it.

I read the following statement wrong so I'll try to answer it again.

"You are comparing 2 amplifiers that obviously have differences other than max power and saying it is definitely because they have more power. It seems you jump to a lot of conclusions."

Actually, I made no such claim! I offered this example as a counter to your implication that simply because a speaker HAD a ton of amplifier power that it NEEDED the power. I simply offered a concrete example as to why Avantegaurde WOULD install a 250watt amp versus the argument that it NEEDED one.
My initial response to this statement was offering a reason as to why the amp with more power would sound better.

Bridging and paralleling are two very different things.
Bridging effects the voltage. Parallel does so with the current. If a design can allow for paralleling you double the current thus doubling the wattage. You also cut the output impedance in half thus increasing your damping factor.

The question of whether or not a set of three basshorns will reach 109dB sensitivity is not as simple as measuring 1watt at 1 meter. Measuring actual sensitivity in the real world is a little more complicated. And the whole 1w/1m standard is very misleading!
1w/1m works adequately for comparing drivers and most simple one to four way dynamic designs. But for planar speakers and line arrays it is basically useless. A typical speaker will measure a particular level at 1m and that level will drop off as a function of distance. A planar or line array will measure one thing at 1m and then INCREASE as a function of distance up to a point. This is because it takes a little space for the entire surface of the planar or all the drivers of a line array to combine.
In the same way, three bass horns are effectively a line array of 6 different 12inch woofers. This takes up nearly eight feet and will only combine at a distance of about 10feet away or more. Therefor, in order to accurately define the actual sensitivity of the entire system you have to measure both the upper frequency horns and the basshorns are the same distant spot. You measure the upper horns to get their true sensitivity at that point and then set the basshorns so that they are of equal SPL at that same spot. THEN you measure the amplifier output. And only THEN do you have a real estimation of the sensitivity of the entire system.

Duke: Ah, yes! I remember now. Then again, your contribution has thrown into the light that we should be careful in defining exactly what "horns" we are talking about.

Your Dream Maker is only a "horn" from 1.7K up. It's not a wonder it would sound so smooth. the majority of all instrument fundamentals as well as all voices aren't coming form a "horn" at all! (if I understand the design correctly)
I would think this would be a major difference between it and something like an Avantgarde! If not, please do explain. I am curious!

My take on the blind test was that the listener was noticing all of the same similarities that seperate Stats and Horns from typical dynamic speakers. It doesnt surprise me one bit that he guessed the way he did.

I've seen the same thing with the (effectively) 100dB Scaena speakers being compared to Magnapans!

Good Gawd Herman!!!

Sit back, take a breather and learn something!!

First of all, Voltage X Current = Power (Watts)
This is basic basic stuff. If you double the current you double the power!

And what I said about distortion is also true. I mean seriously, your most recent post calls into question your very ability to remotely discuss these things.

In all seriousness. Go ask a Electrical Engineer. You'll find that everything I've said about this stuff so far is true.

I don't mean to be crass, but Sheesh!

"Now if you told me that 6 would distort less because each is working 1/6 as much therefore distorting much less"

YES!!!! That is EXACTLY what I am saying!!! (Among other things)

What are YOU reading???

"Those of you making categorical pronouncements about the limitations of horns - all horns - demonstrate the greatest need for education."

I always love the smug responses.
I'm not sure who you are calling out here. But everything I've ever said is based off of extensive and first hand experience. I'm not and never have claimed that it's impossible to create something from a horn. But to date I have yet to hear one that truly impressed me overall.
I'm not out there trying to design one therefor I really see no reason why I would need more education on the matter.
When I hear one I like it will change things.

And honestly, I'm not going to retract anything either. I don't doubt that you (Herman) teach electronics but I am still a little wary as to why, when I said "parallel", you assumed bridge and didn't seem to know the difference.

I had written a lengthy explanation to all of this but Audiogon rejected it for being too long. This is probably a good thing.
So I'll just sum up in a few lines.
First, your equations make sense for DC and purely resistive AC. But this is not how drivers directly coupled to amplifiers behave. The whole argument arose from an example I gave as to why Avantgarde would chose to use a high power amp on an already sensitive speaker. This had nothing to do with the assertion that the basshorn could not be sensitive BECAUSE it has a large amp.
Because this line of arguing really has no relevance to the thread. And because we seem to be on different verbal wavelengths here. I'll simply refer you to Balanced Audio Technology for an explanation on why they list their Vk-75 as a 75watt amp and why they list their Vk-150 as a 150watt amp. Even though the only difference between the two is the internal paralleling of the inputs and outputs and a different nameplate on the VK-150. Any more explanation as to why this matters on a complex load I leave to them.

Cheers, and goodnight, for now.

"Calling me smug is powerful stuff but unlikely to move you any further along in your understanding of horn function and the distinctions that exist from one concept to the next." -Macrojack

If I really don't care about horns one way or the other. And if I don't really care because I have yet to hear one that I truly like. Why do I need to educate myself? I don't care that much about line arrays either. Do I need to also educate myself about them? I'm sure there is some professional out there who could show me all sorts of math as to why they are the bees knees. Perhaps my perception of "smug" was a little strong but it's what I perceived when confronted with the idea that I need to "educate" myself more because I don't "like" horns. They don't suit my taste visavis other designs. I've never said they were an invalid concept.

"I completely understand the difference in parallel and bridged.
I completely understand that parallel amplifiers cannot double the power output. I remain confused that you insist they do." -Herman

Then why did you assume bridge when I said parallel? And why did you need me to make the distinction? Whatever, its neither here nor there.
Laying in bed last night it dawned on me that every time you (herman) refer to "power" you are actually speaking of of "gain". Basic Watts versus dBW. Suddenly it became clear why you were so adamant that a basshorn didn't need 250W of power.
Well obviously it doesn't "need" that much GAIN. And because it has a built in volume control it is unlikely that it will ever USE that much gain. Never the less, being that the driver is NOT a resistor but has a complex impedance curve, the designers probably found a 250W amp useful.

As I said before, you're going to have to talk to BAT directly if you want any more explanation on their specs.
But your perspective makes better sense to me now thinking in terms of GAIN rather than total available power and why you aren't seeing what I've been trying to say here.
A horn may only need a small amount of gain but no speaker is a pure resistor and very likely will benefit from increased power in terms of current.

BTW, I offered no apology. Taking it truly is smug.

"Sorry, a complete load of crap.
Are you serious? You add up a bunch of errors and the total error is less than any individual error?"

Yes, absolutely serious. And it beguiles me as to why you don't get it.
I didn't use the term "errors" but since you do, in this sense "error" would be any deviation from FLAT. Maybe I should have said "frequency response" instead of transfer function.
But this doesn't change my assertion. Which, by the way, is provable with actual measurements.

In simplified terms, take two drivers with the same frequency range but whose precise deviation from flat response within that range are slightly different. If you add them to the same signal but reduce the gain to each by half (3dB) you end up with the same gain but the deviations from flat frequency will tend to average themselves out as the outputs from the two will combine.

This is a simple case of adding and then dividing by two. How is that not averaging? Aside from the fact that it can be consistently shown with direct measurements.

Until you can prove me wrong instead of just throwing insults you have no high ground.

"As you you've established clearly that you have no use for horns, pray tell, what use have we of you? Why are you presenting yourself so emphatically in an arena where you have no interest nor expertise?" - Macrojack

See, now this seems smug to me. But it's probably just a case of lost in translation.
My original foray into this thread was the simple answer to the question "Why not horns?" To which my response was the equally simple, because they SOUND like horns. It was not my intention to go beyond that yet somehow I got drawn in.
And since I joined this thread it turns out that the only "horn" that didnt sound like a horn wasn't even a horn over a significant area of its frequency range.

I AM curious. AND I do have experience with horns. I am NOT resistant to horn theory. But so far my only assertion against is that horns sound like horns. And so far the only place I've presented myself so emphatically was either
a) about amplifier power, etc.
b) the fact that multiple drivers can approach the same sensitivity as a single large horn. Properly implemented, this is true. As I've tried to convey with a real world example.
c) that at least one of the examples of a "horn with a smooth sound" wasn't even a full horn after all.

So, really, you probably have no USE of me. Even so. How does that restrict my presence? And, most importantly, how does educating myself on horn theory change any of the above three?
For the record, I will most likely still go and read what you have suggested because I am infinitely curious. My only problem was with the idea that we seemingly had to stop all interaction in this thread until I went to read your suggested material.
Again, perhaps intentions were lost in translation.

Herman. I have one last thing to mention with regards to parallel amps in an effort to reconcile why we keep misunderstanding what each other is saying.....
If you take a look at BATs website and look at the following products: VK-255SE and VK-600. Scroll down to the bottom of each page and look at the specs. You will see that both amplifiers have 26dB of gain. Yet one is rated at 150W into 8ohms and the other is 300W into 8ohms.
The practical difference between these two amps is that the VK-600 is basically a chasis with two of the smaller amps fit inside. There are other differences but practically speaking, this is the crux of it. The 600 basically has double the output devices in parallel that the 255 has. Indeed, they previously offered a VK-250M which was basically the same as a VK-600 in two seperate boxes. Now, they go a step further. Just like the VK-75 and the VK-150, if you take the VK-600 and parallel its inputs/outputs you get an amp with the same gain but twice the current capability again.

Bottom line. I totally agree that paralleling identical amps does NOT change the gain (dBW) one bit. But clearly, BAT is a good example of how it does double the output power.
Perhaps we've been arguing over two very different things here. Whatever the case, if you still strongly disagree with what BATs website clearly states then, well, I have to admit I am curious to know why but this is probably not the best place to hash that out.
Cheers.

Macrojack, Good grief man! I only have so much time to waste here. I told you I would read it! :)

And I have. Naturally, the first thing I have to note is that even Mr. Woods has stated that the conical (the least colored) "has very little trace of the "honky" sound." Which is also to say that it still has that sound. Perhaps my ear is especially sensitive to that. Not sure yet. I will have to explore it some more.

Either way, Bill Woods as much as admits that even the least colored horn is still colored. This may seem like nit-picking but in an hobby where we describe differences in cables as "vast", is it not reasonable that even this slight coloration is still obvious to some?

Thats my observation after a first pass over the recommended article. Going back for more..........

"Mine are as crystal clear and utterly precise as anything you have ever heard and in all likelihood significantly more so." - Macrojack

I can appreciate your enthusiasm for horns. I really can.
But this statement can not be supported in any manner since you do not have first hand experience with what I have heard.
Nor do I have the benefit of hearing your system.
So, on this we are at an impasse.
Fortunately this is fine. I'll continue to keep an open mind, try to learn whatever I can from you and your fellow enthusiast, and wait for the day that I hear a horn I can truly appreciate.
Cheers!!

Herman, if you had read the website you would see what I am talking about. Two amps with the same gain but different rated output power into the same load. The only difference being the number of PARALLELED output devices.
Given this comes from a well respected and established company whose designer has credentials far beyond what is adequate for HiFi and certainly your own, I find it humorous that you continue to ridicule me.
I know nothing but what I have learned from other highly qualified individuals.

If you would like me to quit "bothering" you then stop the insults and respond to this concrete example.
Or, just be quiet. Or must have the last word?

"Perhaps we equate loudness with distortion and respond by playing louder when the distortion is absent." - Macrojack

I've found this to be absolutely true in my own experience. Even with dynamic drivers. These days I've have to be conscious of the volume from time to time to make sure I'm not going overboard.

P.S. can someone show me where to figure out how to quote others in this thread properly. Instead of cut and paste. Thanks!!

Almarg: Thank you so much. You've explained it so much more eloquently that I. Indeed, the operative word I've been neglecting is MAXIMUM. And you are correct, the primary differences are current capability and heat dissipation.
I didn't anticipate these distinctions to have made a difference in an Avantgaurd Trio but it did. Why? Who knows for sure? To which my guess was that the amp with higher maximum power capability (based on current) handled even small impedance variations with more grace.

Thanks again for your input.

Almarg...... upon consideration I'm convinced you are correct.

All three of my examples have listed specs of 26dB gain. This equates to 400W, correct? (under ideal circumstances)
Yet the other specs are listed as 150W and 300W. The maximum wattage is not specified for paralleling the largest amp (VK-600m) So we can probably assume that it tops out at 400W maximum (still 26dB gain) with overkill ability on the current side.
All they are doing is adding more power supply and more heat dissipation.

Thanks again for your contribution. This probably wasn't the best example to illustrate my original point. ugh! haha.

@ Almarg/Herman........
Well, a couple things are certain here.
1) first and foremost, it was classless to get personal and call names with Herman. My sincere apologies on that.
2) I've become completely lost in what has been said by me, by others. What hasn't been said, yadda yadda yadda. I know I have a habit of letting my thoughts move faster than my fingers and too often key words such as "maximum", "maybe", etc etc. get left out and totally screw up the intended meaning.
3) I've fallen prey to remembering particular specs incorrectly and assuming the numbers were correct without going back and verifying by actual math.
4) I just don't care anymore.

Herman, you asked me to stop. At first I was acting on emotion and didn't want to. But I calmed down and decided to stop. But I keep coming back to read more about horns and keep seeing new posts directed at me. Posts filled with animosity, deservedly so. To a point. Is it okay to state at this time that you've more than made your point? I'm stopping. Done. I made a few mistakes along the way. You're not the idiot I too quickly assumed. Admitted. Done.

One last attempt at an amiable contribution on BAT amplifier power.......
Um, well, you guys figured out where the 26dB gain number came from. The 400W was a partial guestimate based on (incorrect) memory, partially from a chart taken from an older Music Fidelity paper. Had nothing to do with actually running the numbers, not knowing actual input sensitivity.

I could have sworn a VK-600 was the same as a pair of VK-250 in one chasis. Nope, remembered that wrong too. Slight differences there.
But I found this for you guys to chew on and play with. (since it seems you're kind of 'into' figuring this out.)
BAT has an old page of specs that can still be accessed directly. http://www.balanced.com/products/amp/specs.O.shtml
Obviously the simple act of paralleling doesn't DOUBLE (definitely wrong there) but the power does go up. Interesting.......
Compare the charts for the VK-250 and VK-250M. Same gain. Same input sensitivity. 50W difference at 8ohm. Note also the VK-500 and VK-1000. Same gain. Same input sensitivity. 100W difference at 8ohms.
I point these out for you to play with because I KNOW (no really, I mean I REALLY know this time) that the only difference in these two comparisons is the internal paralleling of the inputs and outputs. No switches to be flipped. No changing rails. In fact you could take either stereo unit and convert it to mono without ever opening the chasis.

FWIW

P.S. forgot to mention....... (yet again)
On the chart, a VK-1000 is just a monobloc version of the VK-500.

World's greatest catch-all argument for your favorite thing.....whatever it may be.
"You just haven't heard one properly set up!"

Ah!! But of course!! How unlucky for the rest of the world that there are so FEW amazing systems out there. Please tell me, where do I go to buy one this instant and who can I get to "properly" set it up?!

Indeed, for this particular thread, Weseixas makes THE most compelling argument. Though you could almost miss it. If your live reference (assuming you have "live" as a reference) is amplified music then it's no wonder horns are so appealing. And, sadly, these day's that's pretty much everything. Kinda hard to find live amplified music that doesn't have multiple horns in it.

"I for one know its possible to design very good sounding accurate loudspeakers of most any design and transducer type so why not with horns?" - JohnK

Good sounding? Certailny.
Accurate?? By what definition?

Better bass from horns versus a Thiel??
Define better.
It may have more "punch" but it's severely delayed.
Pick your compromise.

"My mid-tweets are delayed so I am time aligned." - Herman

Please define time aligned.

My point, in this case, is that unless you changed out the crossovers in your speakers you may have some sort of "alignment" but the bass is still lagging the mid and the mid is still lagging the tweet.
A step response will reveal this.
And while what your's sound like in relation to the vast majority of box speakers may be true it may not necessarily be true in relation to a Thiel. A Thiel is time coherent, which makes it unique in this regard.

Herman, believe me, I have no desire or intention of getting into another worthless debate with you.

But you do force me to defend myself.
First, I never said that Thiel was the only time coherent speaker out there. Having owned Meadowlark as well as multiple pairs of Dunlavy I can safely say that time coherence is not something new to me. My assertion was simply that the exact speaker in question (Thiel) WAS time coherent and that "most" horns are not because "most horns" that I have encountered do not use first order crossovers.
Clearly, I do not know what YOUR speakers use. But when I look at the pictures of your system I appears to me that the upper horns are the Avantgarde Duo. If this is wrong please share. Yesterday I took apart a pair of Duo horns to see what was inside. On the (stock) pair that I looked at there was certainly more than a single capacitor going to the tweeter. I then measured the speaker and found I was correct in assuming that the Duo was not time coherent. The impulse response and step response clearly show that it is NOT.
THIS is why I said that (quote) "unless you changed the crossovers" neither are yours. I ALSO started off by asking what you meant by "time aligned". This, in other words, was the perfect opportunity for you to explain that indeed YOUR speakers use first order filters.
If indeed they do then they very well may be time coherent.

I am perfectly willing to accept this. But up to this point you have not indicated this is the case with your speakers. And time alignment is not the same as time coherent.

So, as I said. Please indulge the curious here (not only myself. I happen to know that Unsound is also a fan of time coherence).
Please go into more detail on YOUR speakers.
If you have a first order filter on tweeter. Great. What about the midrange and woofer? All three need to have minimum filters for the speaker to be truly time coherent. I am sure you know this. And I ask because I am truly curious. If your speakers use first order from top to bottom then you are only the second person I have come across to implement something that I have been exceedingly curious about for a very long time. Ie. horns+first order.

I am also very curious to know what woofers you are using. If your speakers did start life as an Avantgarde Duo, did you incorporate the stock woofer into your horn?

Thanks.

Herman,
I reread your most recent post. Good information. Thanks.
I'm curious. How exactly did you go about implementing a digital crossover without any phase shifts or time issues?

Thank you for added information Herman. I appreciate it.

I suppose I was using the looser definitions of "unique" as in "distinctly characteristic" or "unusual". (Meriam-Webster goes into a drawn out discussion over the battle of useage on this word. Some scholars thinking it should be used in an absolute sense, others giving it broader application)
Anyway, thats neither here nor there. Probably not the best choice of words to indicate that the idea of time coherency by design is exceedingly rare. To the best of my knowledge, only Vandersteen and Thiel on a consistent basis anymore.

My understanding of the differences between time alignment and time coherence comes mostly from those who care about such distinctions. (John Dunlavy, Pat McGinty, Richard Vandersteen, Roy Johnson, etc. Ah well, John Atkinson too)
According to them, time "alignment" is the physical placement of the drivers with the attempt aligning the leading edge of an impulse. Designs with slanted and concave baffles are attempting this. Wilson Audio, the Focal Utopia line, Avalon, etc. are good examples of this.
The distinction between these designs and those such as Vandersteen and Thiel are in the minimum phase filters. Only minimum phase filters prevent a timing delay within the crossover. So, according to them, time "coherency" is when all frequencies arrive at the same time and in the same phase. Since all filters of a 2nd order or higher delay the signal to some degree, only a minimum filter combined with physical alignment achieves coherency.
Things get a little grey when someone like Hansen comes along. Hansen uses minimum phase filters and physical time alignment but inverts the polarity of (If I remember correctly) the midrange drivers. Thus his speakers are time "coincident". Ie, all frequencies arrive at the same time but some will be out of phase.

Thank you for allowing me the opportunity to share this primer. I doubt I did the concept full justice. So at this point, I would suggest reading the Green Mountain Audio site for more precise info. Roy goes into serious detail. Far more than any of the others did. And it's interesting reading to boot!

I'm just starting to understand the realities of varying digital filters and their "orders". But from what I understand so far, even higher order digital filters have timing delays. But, admittedly, I'm still learning about these bad boys. For now I'm only comfortable with analog filters.

But thats why I was so intrigued by what you (Herman) have done! If your digital filters do preserve the time domain then I'll bet that IS one helluva system!
Cheers!

I've been a Time Coherent "fanboy" ever since I first encountered and sold Dunlavy speakers about 15 years ago. And I'm just as passionate about that design as you guys are with horns. But, having a lot of experience with Avantgarde as well, it has always been a curiosity what would happen if these two principles were combined.

Here is a story about a friend of a friend who is attempting to do just that.
http://www.stereotimes.com/jimlangham.shtml

Mr. Langham lived for a long time with the mighty Dunlavy SC6 as his reference. Then he heard these Magicos and began the quest of combining the best of both worlds. The article doesn't mention this part of it. I only know because I know his friend who told me about it.
It might be an interesting article for all you horn guys though!
Cheers!

Cool! Thanks Mapman.
Ima check that out.

Herman, there certainly has been much debate over the merits of time coherency.
Just to clarify one point first. The way they describe it, time "coherent" demands time "alignment". But the reverse is not true.

You're point about phase is certainly correct. But I think there is also a distinction with the "when" of phase. For instance, it's either the 2nd order or 4th order filter (I can't remember which) that is phase coherent in the crossover region. Which is to say, all the peaks and valley's line up. The difference is that some frequencies started before others. The delayed ones are a full cycle behind. They are still phase coherent but not time coherent.

The easiest way I found to grasp it was to note that TIME coherent was at the pinnacle of the hierarchy. Indeed, most people, when refereing to this type of design, say "Time AND phase coherent". But it's redundant to say that since time coherent demands phase coherent. It demands both time alignment and phase alignment. These other two could be achieved individually by means of physical placement or filter makeup. But both, on their own, was only part of the story. Anyway, thats the best way I know to describe it.
Also, I think phase alignment and coherent ARE the same thing. But I'll have to think about that a little more to be sure. No, I think its true. anyway..........

First order filters do have phase shifting but the filter circuit as a whole compensates. The current lag in an inductor is the same degree (hopefully) as the voltage lag in a capacitor. But, I'm going to have to think about that some more before I try to go any further. I want to make sure I don't mistate anything.

The one measurement that is the arbiter of all this is the acoustical step resonse. Two speakers that easily show this is Wilson and Dunlavy. Both are time "aligned".
Wilson: http://www.stereophile.com/floorloudspeakers/920/index6.html
Dunlavy: http://www.stereophile.com/floorloudspeakers/162/index10.html

Looking at the step responses. Though, be careful when reading what JA has to say. I've noticed that over the years he throws all the descriptions around without much measure of consistency.

The short of it is this. The only speaker design that shows a step response (and therefor the most accuracy in the time domain) that mimics the input is a "time coherent" design. Ala Dunlavy, Vandersteen, Meadowlark, etc etc. They are the only ones that approach the right triangle form.

The merits of this? Well, like I said, Hotly debated.

I gotta run. More later.
Cheers!

Different / Better example........
Herman, here is a different example of a speaker that is "time aligned" but with a high order crossover. (Linkwitz/Riley I believe.)

All of the drivers are in the same polarity as well. It's easier to see the delay that the crossover imposes. But I think (dont hold me to this) it IS phase aligned.

http://www.stereophile.com/floorloudspeakers/699hales/index4.html

Different / Better example........
Herman, here is a different example of a speaker that is "time aligned" but with a high order crossover. (Linkwitz/Riley I believe.)

All of the drivers are in the same polarity as well. It's easier to see the delay that the crossover imposes. But I think (dont hold me to this) it IS phase aligned.

http://www.stereophile.com/floorloudspeakers/699hales/index4.html

Macrojack, YES, that is the precise way to describe it. It is 360degrees out of phase. But if you take a snapshot in time and look at the waveform (sine waves show this best, obviously) it LOOKS like it is aligned because all of the peaks and valleys matchup.
And herein is where the marketing BS starts to really get out of control. Well, in one manner anyway.

I'm still trying to find the place on the web that helped me the most in understanding how first order filters result in zero phase shift. Haven't found it yet..........

Exactly Herman! What you've stated is the crux of the argument FOR time coherence. What I stated is the over simplified reasoning given by designers who use steep filters.
They point to "phase coherence" but the only thing they are measuring is sine waves.

As far as "alignment" versus "coherent" go, well, maybe just semantics. Thats fine. I'll go just one step further using a different explanation from another designer and then let it be. Because to each their own.
Anyway. This is how Pat McGinty basically explained the difference in his mind.
Take two drivers, a tweeter and a midrange and you mount them on a flat baffle. Connect the positive leads together and the negative leads together. Take a 9V battery and tap the leads against the battery. The microphone will see two distinct upward spikes. (assuming you touched positive to positive, etc.) Then you start to slant the baffle backwards an increment and repeat the battery test. The result is that the spikes will converge a little bit because the acoustic center of the tweeter physically leads the midrange and, assuming the tweeter is on top, the more you slant it backwards the more the tweeters acoustic center moves backwards towards the acoustic center of the midrange. Perpendicular to the horizon is the frame of reference here.
Anyway, at some point the microphone will see one convergent spike. This is what they consider the physical time alignment of the two speakers. And this was basically the first step of the design process used by Meadowlark, once they decided on the drivers they were going to use.

So at this point the drivers acoustic centers are aligned at the precise point in space that the microphone sees them as one.
So if you now apply a good and appropriate first order filter to the drivers you should end up with a fairly accurate step response. This is what they consider time coherent because it is the only way that all frequencies arrive at the microphone (or ear) at exactly the same time. And, actually, Meadowlark's were pretty good at this.
But, if you applied a fourth order filter as was the case with the Hales Transcendence Five speaker that I referenced. (And also once owned) you end up with a step response like what you see in the Stereophile article. If you bypassed the crossover in those Hales and set up a microphone at a normal listening level at a normal listening distance and applied the 9V battery test (Note: you aren't trying to pass DC through the drivers, only create a "tick" response by quickly touching the leads) you would see a single spike from all the "ticks" arriving at the same time.
But you pass music through the steep crossover on the way to those same drivers and what happens is that, because of the steep filter, you see the tweeter lead the mid, and the mid lead the woofer. In this case the acoustic centers of each driver are time "aligned" but the speaker is not time "coherent".

Anyway, as I said, these are the distinctions that Time Coherent designers make. And, like Pat McGinty always said, "All you really need to do is look at the step resonse because if that isnt right then nothing else matters." And, for better or worse, these were the decisions and distinctions these guys made. The fact that there are so few who make speakers like this is a very loud statement as to the importance the industry as a whole grants these principles.

Cheers!!

Macrojack,
Those TC-50s are notorious for showing up in any discussion of time coherence. They've become practically an iconic item in the discussion.
Because they used a first order filter on the mid/woofer driver and had that distinctive slanted baffle it is often assumed that they were time coherent.
Stereophile measured the speaker before they obtained the MLSSA system so some of the measurements related to time were not available.
However, it has since been shown that they are not time coherent. It is estimated that they sounded so damn good because the primary driver handling the midrange was using a first order filter and therefor had a very nice impulse response, which the old stereophile measurements DO show.

Cheers!

Also, Macrojack, John Dunlavy was known for claiming that his later Dunlavy Audio Labs speakers were superior to his earlier Duntech designs precisely because the "new" (at the time) MLSSA system gave him the opportunity to measure far more precisely and implement his theories to a greater degree.
This was late '93, early '94.

Anyway, back to horns!!! (didnt want to hijack this thread, haha.)

I have a question for the horn guys.

A complex musical signal has both compression and rarification components of it's pressure wave. I can see how the compression component interacts with the horn.
How does the rarification component react with it, if at all?

Thanks!

Thanks Macrojack. That was very helpful.