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Old 31st October 2012, 03:25 PM   #41
Rudolf is offline Rudolf  Germany
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Originally Posted by dewardh View Post
If one felt a need to "improve" ORION (without going to an altogether new set of drivers) it might be easier to just replace the pair of Millennium with the upper-mid and tweeters from the LX521
"Blooming" is not a problem of the Millennium driver in the first place, but a problem of (excessive) baffle width. Changing the drivers between Orion and LX521 wouldn't change much. Giving the Orion the baffle of the LX521 would be more effective with regard to blooming. This has already been explained by JohnK and SL for some time.

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Old 31st October 2012, 03:47 PM   #42
dewardh is offline dewardh  United States
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"Blooming" is not a problem of the Millennium driver in the first place, but a problem of (excessive) baffle width.
It is, of course, both. One cannot simple narrow the baffle (with a pair of Millennium) because of the front-to-back distance between the domes (and the mounting structure for the rear tweeter). On the other hand one would certainly not retain the existing baffle if one adopted the LX521 upper mid and tweeters . . . that would substantally defeat the purpose of such a substitution, which would be to produce a true dipole pattern in the upper mids.
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Old 31st October 2012, 10:54 PM   #43
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I agree with that, and see it as an advantage for dual tweeters (as opposed to dipole tweeters). The high frequency rolloff can easily be applied to the rear tweeter only. One has to be careful with phase in the filters (if there is to be any dipole cancellation at the tweeter's low end), and as always the front wall should be as diffusive (not absorptive) as possible (regardless whether the rest of the room is "live" or "dead"). "Tuning" the reverberant rolloff is, of course, room dependent as well, but like you I don't believe that rolling off the direct sound is the best way to deal with that.

One of the things that SL has managed to do with the LX521 is cure the "bloom" that ORION suffers . . . standing in the null (at BurningAmp) there was none of it . . . the null is a null from the bass all the way up. The result, of course, is that on axis one hears the speaker and in the null one hears the room. In this regard at least the LX521 is a significant improvement over ORION, at least in a room with "live" side walls (but not enough, I think, to induce me to build a pair).

The LX521 has the expected problems with vertical polar (SL suggested that I should listen to them sitting down, rather than standing up and walking around as I am wont to do) . . . I know that you are familiar with this issue . There are still "issues" to be resolved, but this speaker is another step closer to defining and addressing them . . . it's the best I've heard. It's got me seriously thinking about "revisiting" the ORION tweeters (I see no reason to change the woofers or the W22) . . .
Well, I would say that there is more to this than what SL has done. The "tweeter bloom" issue was resolved several years ago with the Note and by many other DIYer's who have posted there results here at DIY audio. This is certainly not something that should be credited to SL. SL is rather late to this party, though I do congratulate him for joining in. But the way SL appears to have "solved" the issue is not to solve it but to avoid it by placing the tweeter x-o at 7k Hz. In the NaO Note, and other DIY speakers presented here, what has been done is to use a wave guide to control the directionality of the tweeter. I did use a rather high crossover in the original Note, but experimented with a 4k x-o as well, without degradation of the polar response. In the revised Note I'm currently at 6k but will probable shift closer to 3k in the finalized version. It's a matter of what sounds better. I may well issue two configuration files and get people decide which sounds better for themselves. That's an advantage of using a digital x-o, and use of a digital crossover also allows the user to change the tweeter delay and "tilt" the main tweeter lobe as desired.

I also take considerable issue with the use of a 1st order filter between the upper and lower mids. I emailed SL about this, but he has not replied. I will have a discussion of this when I revise my News web page later this week. Frankly, if it is desired to make the system a hybrid, active 3-way, the better choice of crossover would seem to be a higher order passive crossover between the upper mid and tweeter.

Lastly, I do agree that dual (front and rear) tweeters do allow some flexibility in tuning the power response, but controlling directivity of the tweeter is just as important. Additionally, what I have found in my revision is that with the crossover at 6 or 7k the rear tweeter isn't really all that necessary. The imbalance of the reverberant filed resulting from a lack of a rear tweeter seem more significant with a lower crossover point, such as the 2.2K of the NaO II or the 1.4k of the Orion. Those speakers need the rear tweeter. But when the x-o get pushed to 6 or 7k the rear tweeter is less important because the upper midrange LP filter at those frequencies still allows considerable radiation to the rear above the x-o point. For that reason the revised Note is designed with the rear tweeter considered as an option.

{edit: Please recognize that Tweeter bloom and baffle related dipole bloom are different issues.}
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Last edited by john k...; 31st October 2012 at 10:56 PM.
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Old 1st November 2012, 12:18 AM   #44
dewardh is offline dewardh  United States
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Well, I would say that there is more to this than what SL has done.

I also take considerable issue with the use of a 1st order filter between the upper and lower mids.
There is always more to it . . . (and a few things that I might have done differently). But speakers are always compromises . . .

Whatever the "theoretical" issues are with the first order filter it works fine . . . I heard no evidence of any sort of "distress". Clearly SL wanted to keep the "passive" crossover as simple as possible, and he may have been thinking about phase rotation issues and cone breakup as well. I see some advantages (as well as the obvious disadvantages) to the "two-way-mid" instead of "two-way-tweeter", even though I'll likely go with the latter if I mod my ORION.

Certainly SL is not the first to address the "bloom" issue, and it has been widely discussed here and elsewhere. Most of the previous "solutions" that I have seen make other unfortunate compromises and introduce other problems (like unsatisfactory vertical pattern control) and reflect the too common error of focusing on one "feature" at the expense of (significant) others. I have no idea how long SL has been working on this design (although the custom drivers suggest rather a while) or how many iterations the design has gone through. What distinguishes it from the other efforts that I have seen and read about is that the LX521 is a balanced and pretty much completely successful design (which like all speakers still has room for improvement).

If I didn't have ORION already I'd buy the (soon to be available) kits in a heartbeat. There is nothing else out there that does so many things so well. Listing to them at BurningAmp (where I was looking for problems, and the room provided some) I found myself constantly thinking the same thing . . . there's nothing wrong with them (well, they won't play as loud as Earl's horns, but that I don't need).
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Old 1st November 2012, 02:33 AM   #45
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Originally Posted by dewardh View Post
There is always more to it . . . (and a few things that I might have done differently). But speakers are always compromises . . .

Whatever the "theoretical" issues are with the first order filter it works fine . . . I heard no evidence of any sort of "distress". Clearly SL wanted to keep the "passive" crossover as simple as possible, and he may have been thinking about phase rotation issues and cone breakup as well. I see some advantages (as well as the obvious disadvantages) to the "two-way-mid" instead of "two-way-tweeter", even though I'll likely go with the latter if I mod my ORION.

Certainly SL is not the first to address the "bloom" issue, and it has been widely discussed here and elsewhere. Most of the previous "solutions" that I have seen make other unfortunate compromises and introduce other problems (like unsatisfactory vertical pattern control) and reflect the too common error of focusing on one "feature" at the expense of (significant) others. I have no idea how long SL has been working on this design (although the custom drivers suggest rather a while) or how many iterations the design has gone through. What distinguishes it from the other efforts that I have seen and read about is that the LX521 is a balanced and pretty much completely successful design (which like all speakers still has room for improvement).

If I didn't have ORION already I'd buy the (soon to be available) kits in a heartbeat. There is nothing else out there that does so many things so well. Listing to them at BurningAmp (where I was looking for problems, and the room provided some) I found myself constantly thinking the same thing . . . there's nothing wrong with them (well, they won't play as loud as Earl's horns, but that I don't need).
SL states that he started fooling around with extending the dipole response in 2009: "In 2009 I had started a project to look for a baffle shape that might provide a more ideal dipole response knowing that a rear tweeter was a necessity."

As far as phase rotation goes, I doubt that played any part in it, although that is speculation. But the upper mid is connected with inverted polarity which seems to have more to do with having the upper and lower mids track phase through the x-o point. Certainly my simulations showed that as well. If phase rotation was an issue, it would indicate that it should also be an issue with the 4th order 1.4k mid/tweeter crossover in the Orion, which it isn't, unless you think it is. Comparing simulations of the revised Note with 1st and 4th order mid coupling crossover shows an additional 130 degrees of phase rotation below 4k Hz. About 40 degrees at 1k Hz.

Would you care to explain you comment that other approached to solving the bloom problem: "Most of the previous "solutions" that I have seen make other unfortunate compromises and introduce other problems? You mention vertical polar response but you previously mentioned this to be a problem with his current design.
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Old 1st November 2012, 03:28 AM   #46
dewardh is offline dewardh  United States
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Would you care to explain you comment that other approached to solving the bloom problem: "Most of the previous "solutions" that I have seen make other unfortunate compromises and introduce other problems? You mention vertical polar response but you previously mentioned this to be a problem with his current design.
Regarding phase rotation . . . every crossover adds more. And we'd probably all have preferred less at the ORION MT crossover, but neither driver permitted anything less than LR4. The new mids are very forgiving that way.

A messed up vertical polar is almost unavodable with multiple stacked drivers. The mess is minimized in the LX521 but not eliminated. Designs that stack multiple mids (to get more displacement) or use drivers like the Neo-8 (which almost guarantees lobing because of its length) are worse, often much worse, since they tend overall to be acoustically "long" and have excessive spacings at the crossovers. The MMT portion of the LX521 is actually quite small, which minimizes the issue. The "no baffle" designs are actually stacked circular baffles . . . with a whole 'nother set of problems. SL avoids such common mistakes. As with all his designs the LX521 seems to strike a balance . . . there may be "better" ways to do several aspects of the design in isolation, but taken together the compromises work and it is better than the sum of its parts.

But there are also things that are just relics . . . since he's using his existing ASP, which is inherently three-way, we get a whole section (and amp) dedicated to a couple dink tweeters that only run from 7kHz up. That's a choice dictated by history, not by design. I'm sure, though, that SL weighed the alternatives (particularly the more complex passive crossover that would be needed for the MT cross) and concluded that the present split works better overall. Clearly, though, it could be done either way, or four-way active, for that matter. Equally clearly there is nothing to be gained by nit picking such trivial aspects of the design.

I asked about the odd baffle shape . . . SL answered that it was mostly cut and try, since "theory" wasn't much use with multiple drivers in such close proximity (an exageration, I'm sure, but with a germ of truth). I'm tempted to think that there is also a bit of "signature" to it . . . as there was with the ORION side panels, and is with PLUTO. He's not a man given to visually pedestrian design . . .
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Old 1st November 2012, 12:14 PM   #47
Vix is offline Vix  Yugoslavia
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Dewardh,

I don't want to take this thread off-topic, but I am very curios to know how Open Baffles presented at Burning Amp sounded. More specifically, I'd like to know your opinion regarding Nelson Pass Open Baffles (and perhaps compare them to SL's OB's). I know they have quite a few differences, so don't really belong to this thread, but since you were there...

Thanks,

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Old 1st November 2012, 01:24 PM   #48
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Regarding phase rotation . . . every crossover adds more. And we'd probably all have preferred less at the ORION MT crossover, but neither driver permitted anything less than LR4. The new mids are very forgiving that way.

A messed up vertical polar is almost unavodable with multiple stacked drivers. The mess is minimized in the LX521 but not eliminated. Designs that stack multiple mids (to get more displacement) or use drivers like the Neo-8 (which almost guarantees lobing because of its length) are worse, often much worse, since they tend overall to be acoustically "long" and have excessive spacings at the crossovers. The MMT portion of the LX521 is actually quite small, which minimizes the issue. The "no baffle" designs are actually stacked circular baffles . . . with a whole 'nother set of problems. SL avoids such common mistakes. As with all his designs the LX521 seems to strike a balance . . . there may be "better" ways to do several aspects of the design in isolation, but taken together the compromises work and it is better than the sum of its parts.

But there are also things that are just relics . . . since he's using his existing ASP, which is inherently three-way, we get a whole section (and amp) dedicated to a couple dink tweeters that only run from 7kHz up. That's a choice dictated by history, not by design. I'm sure, though, that SL weighed the alternatives (particularly the more complex passive crossover that would be needed for the MT cross) and concluded that the present split works better overall. Clearly, though, it could be done either way, or four-way active, for that matter. Equally clearly there is nothing to be gained by nit picking such trivial aspects of the design.

I asked about the odd baffle shape . . . SL answered that it was mostly cut and try, since "theory" wasn't much use with multiple drivers in such close proximity (an exageration, I'm sure, but with a germ of truth). I'm tempted to think that there is also a bit of "signature" to it . . . as there was with the ORION side panels, and is with PLUTO. He's not a man given to visually pedestrian design . . .
First let me say that I have no argument with SL. But that doesn't mean I won't be critical of his work, or the work of others. That is the way things move forward. As always, it is typically those who blindly support someone's work and dismiss the work of others that hampers progress. Simply stating the the 1st order is better without having the experience of examining different crossovers, as I have, doesn't make it so. You appear to be saying that no one but SL can get it right to which I would say you are way off the mark. I am critical of the use of the 1st order passive crossover because my experience with the design and revision of the Note indicates that it is significantly better with a higher order crossover between the mids. I encourage SL to experiment with this, and in fact, if SL chooses to retain the hybrid deign going forward I would encourage him to make the effort to place the passive x-o between upper mid and tweeter. A higher order passive x-o at 7k is not difficult to implement at all.

As for excess phase rotation with a higher order mid coupler, I have added a comment on that to my updated News page.

In any event I will continue to be as critical of anyone's efforts, including my own, if i think there is a better approach. In fact, my critical nature of SL's write up of Phase shift due to dipole D & effect upon xo lead him to rewrite the discussion and, I am pleased that he made reference to that discussion. So, while I may not be so politically correct in the way I approach things, apparently people, including SL, are listening.
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Old 1st November 2012, 01:38 PM   #49
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Would it be correct to assume that the LX521 uses the 1st order filter to blur the presents of two mids?
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Old 1st November 2012, 01:44 PM   #50
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Would it be correct to assume that the LX521 uses the 1st order filter to blur the presents of two mids?
I certainly can not speaker to the LX521, but since this thread is suppose to be about the NaO Note revision I can comment that I have tried many difference crossovers, both order and frequency, and I find that the higher order crossovers yielded a more coherent, more detailed midrange response. So, at least for the Note, blur would be the operative word, but not in a favorable light.
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