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Home » Audio » Speaker » Widerange midwoofers, specs, and x-o pts...
| Re: Widerange midwoofers, specs, and x-o pts... [message #60999 is a reply to message #60998] |
Wed, 23 September 2009 19:38   |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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You're getting too excited here, Dark Moebius.
I was simply describing how dome tweeters can work if you do some special gyrations to make them happen. They are special gyrations, but I seem to be the only one who has taken the time to make them happen.
Newbies here need to know that this is possible, though difficult. While Rick is not directly responding to me, everyone on both here and PE, knows that I have used domes with my line array, and everyone that I know or ever saw, except for the PipeDream people's 81,000 buck devices, have used ribbons.
While I have a short trigger sometimes, and Rick is really good at pressing my buttons when I'm not paying attention, my only purpose is to correct any fallacies that I see in terms of line array building.
You or anyone else has that right also. You, or Rick or Fred, can disagree with the use of domes in line arrays. I don't have a problem with that. But you cannot tell all the newbies that using them will cause unacceptable comb filter distortion, without me stepping in and, as politely as I can, saying, "No, that's not correct, if, and only IF, you do it this way." And I've described the way.
I do have to apologize for flipping out before. I really don't like to be letting my buttons be pressed.
Everyone here has specific biases. Rick has made it pretty clear that he thinks Krutke's measurements of Fountek tweeters are wrong, but he's not been will to offer any counter measures to show that other than his own viewpoint.
I maintain my right to explain when someone has made an incorrect statement and my way to fix it. Except for Fred and I(and I hope I am wrong), we may be the only DIY people(meaning we don't offer finished items or kits for sale) who have actually built line arrays from scratch using Jim Griffin's white paper that have a tweeter array as part of the system. I believe everyone else may have built one of Rick's kits. This is great, and i encourage everyone to build what they feel comfortable with doing. But when you do it completely yourself, you've learned things that you won't learn in any other way.
Kind regards and thanks for sharing,
Marlboro
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| Re: Widerange midwoofers, specs, and x-o pts... [message #61019 is a reply to message #61003] |
Thu, 24 September 2009 19:38 |
darkmoebius2
Messages: 37
Registered: August 2009
Location: Los Angeles, CA
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Baron |
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| Quote: | I believe that distortion is the most significant measurement...FR is so dependent on so many things from the speakers to the room to actual hearing of the individual to almost everything...But distortion is pretty steady: IT INCREASES AS THE VOLUME INCREASES.
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Certainly a logical deduction, but...
I wonder if the levels(and types/orders) of distortion between the best of applicable ribbons and domes are as audible as the numbers seem to suggest.
Not to mention, there are other factors in how things ultimately sound. Horizontal and vertical dispersion characteristics seem to favor ribbons in array circumstances i.e. ribbons have limited vertical dispersion and much greater horizontal dispersion giving a greater sense of space and size.
Also, Zaph's tests were done 4 years ago and I wonder if ribbon/planar designs have progressed much since then. Or, at least, manufacturing has evolved to higher tolerances thereby improving performance.
I did find this comment on DiyAudio regarding one person's comment that ribbons tended to sound "light", "bodyless", "boring/no kick": | Quote: | btw, *most* of the problems kea posed are likely due to an overdamped output because of amplifier pairing with very low output impeadance. Match OR almost double the ribbon's impeadance (i.e. for an 8 ohm ribbon either 8 ohm output or up to 16 ohm output for the amplifier), and you should find that the sound changes rather dramatically in favor of the low mass driver. The tangible air compression (or "kick") IS a product of the drivers mass and its transfer impeadance to the air. The less mass, the less "kick". This is a subjective valuation, BUT generally the lower in freq. you go the more mass your diaprham should have - otherwise it does indeed provide a "lifeless" character (..which incedentally is more accurate to the source but likely less accurate to the event - but this is definitly an art in balancing these two aspects, not a science).
Finally, it seems that everyone is *certain* that the likes or dislikes for ribbons and other low mass drivers are due to harmonic distortion. I find that laughable. Chances are that most people wouldn't even be aware of an increase in 3rd order up to 5% and 2nd order up to 15%. At the lower % levels (below 1%) I would be looking more at 5th order and above to cause any sort of audible problem. So - if you are looking for a problem in most drivers - I wouldn't be to concerned with driver THD unless the higher order (5th+) started moving much past .1%. This doesn't mean that you shouldn't try to minimize THD, but rather that you should be careful in that a reduction in THD may well lead to an increase in distortion that we either cannot measure yet OR can measure, but so far do not understand its importance.
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The distortion comments are most interesting. But, I wonder what the impedance circumstances of Zaph's tests were, too?
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| Re: Widerange midwoofers, specs, and x-o pts... [message #61022 is a reply to message #61019] |
Thu, 24 September 2009 22:14 |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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Re: "Not to mention, there are other factors in how things ultimately sound. Horizontal and vertical dispersion characteristics seem to favor ribbons in array circumstances i.e. ribbons have limited vertical dispersion and much greater horizontal dispersion giving a greater sense of space and size."
The only problem with this is that the human ears don't have the capability to recognize differences in vertical dispersion.....
Jim Griffin was describing circumstances regarding vertical dispersion in line arrays in June, 2008 on the PE forum:
"......talked about the differences in how a near field line array radiates vs. the spreading radiation which would be observed from point sources or for far field radiation. Another consideration with line arrays is from the psycho-acoustical viewpoint. Our ears and head combination provide an exceptional ability to localize sounds in the horizontal plane. Shadowing by the head helps in the horizontal plane.
"However, the ear has poor spatial resolution in our ability to localize sound in the vertical plane. This poor vertical resolution is attributable to the equal distances from each ear to sources in this plane. Furthermore, the ear will mask signals according to both their time of arrival and the strength of each signal. Thus we observe very little ability to discriminate between signals from different sources in the vertical plane.
"Bottom line is that you should not worry too much about the arrival time differences in the near field because of the ears lack of vertical discrimination."
Apparently in the jungle, early man did not need to hear predators coming from the trees, but only from around on the ground.
I'm not positive, but the reference suggests that the extreme differentiation of the human ear-brain to horizontal dispersion and minimal to vertical, would have some influence on your concern. I would need to see some measured comparison between domes and ribbons in horizontal dispersion. Just looking at the fact that the dome stick out, and the ribbon is flat, it would seem to me that dispersion should be easier for something that sticks up compared to something lies flat. But I've no research at the moment on the dispersion comparison. I'll research it.
What do you think?
Marlboro
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| Re: Widerange midwoofers, specs, and x-o pts... [message #61023 is a reply to message #61022] |
Thu, 24 September 2009 22:47 |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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I don't have time for any more research.
What I've discovered so far is not that the ribbon is inherently wider in dispersion that the dome. What makes some of them have such wide dispersion is a kind of horn loading that you see in the HVRT1C or in the Pioneer ART-55D, but that you don't see in the Eton AR Air motion.
There is another factor. The ribbon may not actually have a wider dispersion than a dome:
The output of a planar ribbon driver is evenly distributed over the entire radiating surface, which results in no wave cancellation, diaphragm break-up or resonances. The flat radiating surface also results in a coherent wavefront with even dispersion.
This may be what is perceived as wider when in fact it is really the coherence with less cancellation.
There is a third factor. Ribbons tend to stay the same in their dispersion characteristics as they move through the different frequencies, However Domes tend to beam and the frequency rises. I would be interesting to put a line of domes together on some kind of rising and falling horizontal angle to the listening area. This would prevent the effect of the beaming from influencing the sound. it owuld be fairly easy to do with a line of 30 dome tweeters.
But the problem remains that even a lowly Dayton Neo20FA will be able to match or beat most ribbons in FR, distortion, and spectrum decay.
Its an interesting discussion. I wish one could say there was an answer hands down. I think it still means what people like:
Heres a comparison quote from a guy on Audiocircles about 3 years ago:
"IMHO, what I noticed immediately between the tweeters was the difference in apparent "air" and "detail". Cymbals seem to have a natural shimmer to them, along with triangles etc.
"The 1" fabric dome seems to have more "body" to the sound and less "air". Between the two, I lean towards the ribbons but have grown to like the fabric dome. "
I'm still researching it.
Marlboro
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| Re: Widerange midwoofers, specs, and x-o pts... [message #61024 is a reply to message #61023] |
Thu, 24 September 2009 22:49 |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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Re:
"The distortion comments are most interesting. But, I wonder what the impedance circumstances of Zaph's tests were, too?"
Please correct me if I'm wrong.
I don't think the impedance characteristics make any difference unless you are tied to using passive crossovers. With active crosses various impedance is a non-issue, the amp has direct control of the speaker. Also the spike to infinity that you see at the crossover in passive crosses is either non-existent in active electrical crosses or at least way less.
Maybe this isn't what you were talking about??
Marlboro
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