By the way, in case you haven't seen this yet, here is a link to an italian guys take on a giant concrete sub bass horn indoors: IL PIU' GRANDE SUBWOOFER DEL MONDO - by Roberto Delle Curti - Italy
the poor fellow seems to have gone a bit esoteric since I last visited his site. Still would love to hear his system though.....
the poor fellow seems to have gone a bit esoteric since I last visited his site. Still would love to hear his system though.....
Listening to Chili Peppers in a hot tub of course.........
Ha, ha. But even just that kind of smart-asked "criterion" addresses some fundamental good questions you raised in earlier post. For example, stereo image wouldn't matter. Sound quality, again zilch. About the main implication is that it has to loud to overcome the bubbling.
Not worth fussing over this example except that it illustrates the need for definitions leading to design.
Anybody remember the 5,000 person-hrs of effort "invested" in a church electric organ? We're still waiting for information on the outcome.
Ben
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Hey you got something right.
I'm not a scientist, I won't pretend to be able to evaluate the reality and/or danger of global warming (although I do have very strong opinions based on the data I've seen).
My more pointed concern is our 1st world's appetite for consumption and more, always more. Do we really need to increase our collections of personal possessions and luxuries until every last tree is gone, every drop of water poisoned, every bit of air is full of toxins? I don't think so. And as more of the world moves up to our standard of living and more people want what we have the pillaging of natural resources and the pollution that follows will get exponentially worse, most of this stuff is going straight to the garbage dump in less than 5 years anyway so did we really need it all? There's half a billion people in China that want to trade in their bikes for cars, how is that going to swing the balance? And that's just one country.
Even a 90 degree horn is 6 db down at 90 degrees. Here's the Seos 15 (top) and Seos 12 (bottom) horizontal polars measured by Bwaslo. I think the Seos are all supposed to be 90 degree horizontal. Both of these are measured with the 1 inch Denovo DE250 CD.
The Seos 15 is barely getting 60 degrees at -6db and in some places (3-4kz and upwards of 15 khz) the pattern is narrowing significantly with a hot spot narrowing to about 30 degrees. That's not exactly as bad as a flashlight beam (I do exaggerate a bit sometimes) but it's not good for the people outside 30 degrees.
The SEOS 12 is pretty good at -6db out to 90 degrees up to about 15 khz, but again, it's got hot spots and significant narrowing at 4 khz and upwards of 15 khz. The dark red (full spl) dispersion is barely 60 degrees across the whole passband.
So it's not as bad as a flashlight beam but it's not constant directivity full spl out to 90 degrees either even in the best cases.
Again, it's all about priorities and compromises. You can chose the best directivity, placement and toe in for the job and use 2 mains and do a pretty good job or you can ignore best design principles and fill in all the holes with center channels and surround channels and fill speakers.
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The further away the mains are from the sub the worse the lobing will be. The lobing sim I showed earlier indicated there would be significant lobing around the crossover frequency as little as about 6 degrees off axis. I'm pretty sure 6 degrees off axis is going to be part of the listening position. I think that sim was with 2 sub horns 60 feet apart but there may still be significant lobing issues inside the audience position with the proposed 30 foot mains separation with the sub in the middle. You have to sim it or measure it to find out.
The design goals are pretty well defined:
An outdoor system
An all horn system
A stereo system (however I’m open to the LCR option)
Large full-size, no compromise straight exponential bass horn for the bottom octaves
The throat & rear chamber are steel & wood construction
The throat & rear chamber are contained within an outbuilding
Bulk of bass horn constructed from heavily reinforced concrete
Bass horn built into a “decorative” reinforced concrete/stone wall
Majority of bass horn to be backfilled with Earth
System must have enough headroom to achieve “wow” factor
System will be powered by the electric grid (240/120 Volt, 60-Hz) only
Oval target listening area, about 30 feet wide, by 40 feet deep (approximate & flexible)
The only thing set in stone (pun intended) is the bass horn.
Weltersys, a large wooden power pole is about 900 bucks, and it will last for 50 years. Shorter poles cost half as much. I don’t think I need to go very high off the ground for the mains – but the option is doable. I’d prefer the wooden look. A wooden pole is more “natural” looking than a metallic scaffolding structure. I openly acknowledge that my project is a very pronounced paradigm shift for most folks – in that achieving a system mobility is specifically not a design requirement.
And Relax weltersys – the idea that we’re going to run out of oil anytime soon, is just an environmentalist scare tactic used to obtain R&D tax dollars for alternate energy. The US alone has 300 years of oil reserves under our feet – and probably another 500 years on the seafloor offshores.
Consider the Grand Coulee Dam in western Washington. It produces about 7,000 MW of electricity. The dam’s power source is quite literally rainwater. To get 7,000 MW from Nuclear, we’d need 22,500 pounds of uranium per year. To get 7,000 MW from Coal, we’d need to burn 19.6 million tons per year (and generating 56.1 million tons to CO2).
I don’t have an issue with the CO2 – it’s plant food. I do however have an issue with the sulfur & mercury. The reason my wife is only supposed to consume tuna/swordfish a few times a month, is because burning Coal has literally polluted our entire planet with mercury. My issue with nuclear is that accidents happen. However given the option, I’d take Nuclear over Coal any day of the week. That being said - if I were running the Department of Energy, I’d be damming up every river capable of generating power, from coast-to-coast. But there’s a problem with hydro-power – which is that the same people who think CO2 emissions are overheating the Earth (which will somehow result in them drowning under seawater) - are the very same people who’ll have a complete mental-breakdown if you try to build a new hydroelectric dam – because “What about the fish – What about the fish - what about the immmm-pact. . . .?” I’ll tell you about the fish – there are some pretty dam big fish in the waters around the Grand Coulee Dam. And I’ll tell you about the impact – you get 7000 MW of electricity, with no radioactivity, no sulfur, and no mercury. Point being - just because I think Solar power and electric cars have no future, does not mean that I couldn't care less about our environment. . .
An outdoor system
An all horn system
A stereo system (however I’m open to the LCR option)
Large full-size, no compromise straight exponential bass horn for the bottom octaves
The throat & rear chamber are steel & wood construction
The throat & rear chamber are contained within an outbuilding
Bulk of bass horn constructed from heavily reinforced concrete
Bass horn built into a “decorative” reinforced concrete/stone wall
Majority of bass horn to be backfilled with Earth
System must have enough headroom to achieve “wow” factor
System will be powered by the electric grid (240/120 Volt, 60-Hz) only
Oval target listening area, about 30 feet wide, by 40 feet deep (approximate & flexible)
The only thing set in stone (pun intended) is the bass horn.
Weltersys, a large wooden power pole is about 900 bucks, and it will last for 50 years. Shorter poles cost half as much. I don’t think I need to go very high off the ground for the mains – but the option is doable. I’d prefer the wooden look. A wooden pole is more “natural” looking than a metallic scaffolding structure. I openly acknowledge that my project is a very pronounced paradigm shift for most folks – in that achieving a system mobility is specifically not a design requirement.
And Relax weltersys – the idea that we’re going to run out of oil anytime soon, is just an environmentalist scare tactic used to obtain R&D tax dollars for alternate energy. The US alone has 300 years of oil reserves under our feet – and probably another 500 years on the seafloor offshores.
Consider the Grand Coulee Dam in western Washington. It produces about 7,000 MW of electricity. The dam’s power source is quite literally rainwater. To get 7,000 MW from Nuclear, we’d need 22,500 pounds of uranium per year. To get 7,000 MW from Coal, we’d need to burn 19.6 million tons per year (and generating 56.1 million tons to CO2).
I don’t have an issue with the CO2 – it’s plant food. I do however have an issue with the sulfur & mercury. The reason my wife is only supposed to consume tuna/swordfish a few times a month, is because burning Coal has literally polluted our entire planet with mercury. My issue with nuclear is that accidents happen. However given the option, I’d take Nuclear over Coal any day of the week. That being said - if I were running the Department of Energy, I’d be damming up every river capable of generating power, from coast-to-coast. But there’s a problem with hydro-power – which is that the same people who think CO2 emissions are overheating the Earth (which will somehow result in them drowning under seawater) - are the very same people who’ll have a complete mental-breakdown if you try to build a new hydroelectric dam – because “What about the fish – What about the fish - what about the immmm-pact. . . .?” I’ll tell you about the fish – there are some pretty dam big fish in the waters around the Grand Coulee Dam. And I’ll tell you about the impact – you get 7000 MW of electricity, with no radioactivity, no sulfur, and no mercury. Point being - just because I think Solar power and electric cars have no future, does not mean that I couldn't care less about our environment. . .
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Good start. But clear you haven't given much thought to performance spec. Saying it's got be a horn, important as this is to all of us, is not a performance criterion. Here're a couple more.
What is the room (or setting, eh) like acoustically?
Music content and quality of sources?
What kind of freq range? Importance of treble?
Quality of stereo image? Ambiance versus direct sound?
Seating area to be served?
Time-Alignment? Distortion tolerance? Boom tolerance?
How's your hearing - ever been checked? (may not need treble over 7kHz)
and of course, are you willing to have crummy but loud commercial-quality sound that some friends will admire or are you after high fidelity that a different set of friends will admire?
B.
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are you actually reading any of the posts dude? OUTDOORS!!!!! Has been mentioned a zillion times, but you seem to overlook it everytime....
ROFL.....
Eric,
Without defining the "wow" factor in dB SPL, and the distance from the outdoor system to the listener, your sonic design goal is anything but "well defined".
I am not uptight or scared about whether we will run out of oil, or soil the air burning it for another 500 years, I can live with or without it.
Using non-polluting renewable sources of energy production is an excellent concept, as is inter-connecting a global energy production grid to equalize disparities in local energy harvesting.
Unfortunately, oil and coal companies have nothing to gain financially by selling non-polluting renewable sources of energy, so sequestered petrochemicals and coal will continue to be utilized until the cost of extraction and environmental clean up becomes less cost-effective than the alternatives.
Until that actually happens, the oil companies will continue to "jerk our chains" with "scarcity" when they slow down production to jack up their profit margins.
At any rate, you have pretty well covered your aesthetic design goals, all that's left is figuring out your sonic goals, then buying/building them in the real world.
Art
why "even"? that's the basic performance definition for horn directivity, the nominal angles are determined by the -6 dB points afaik
I disagree.
Assume you are a member of the elite 0.1%. Where would you invest your money? in a coal-fired electric plant, a nuclear fired electric plant, or in a hydroelectric dam?
I don't know about you, but when I think about owning a dam, the song money-for-nothing comes to mind. . . .
Originally Posted by just a guy
Even a 90 degree horn is 6 db down at 90 degrees.
A nominal 90 degree horn's polar response should be by definition -6dB at a point 45 degrees off axis.
Since many horns don't conform to their nominal pattern over much of their range, one needs to look or listen to the polar pattern to see/hear what the pattern is at various frequencies. JAG was simply showing that HF "beaming" occurs in the horn he referenced, though that problem is not common to all horn designs.
Art
Even a 90 degree horn is 6 db down at 90 degrees.
Bob,
A nominal 90 degree horn's polar response should be by definition -6dB at a point 45 degrees off axis.
Since many horns don't conform to their nominal pattern over much of their range, one needs to look or listen to the polar pattern to see/hear what the pattern is at various frequencies. JAG was simply showing that HF "beaming" occurs in the horn he referenced, though that problem is not common to all horn designs.
Art
I'm going to start by stuffing (qty 8) 18" B&C drivers into the throat, with 10 kW. That should give me the "wow" dynamic range. I will make adjustments to the rest of the system from there.
If it's over the top, I can always turn down the volume. . . .
I'd go for the dam, and hire you to build it, if you can guarantee me the displaced property won't cause environmental problems, and still guarantee me a better ROI
But first I'd want to see how your sub turns out, writing does not complete anything, which reminds me, time to get out to the shop again..
Art
That's exactly the point I was trying to make, a 90 degree horn is 6 db down at 90 degrees. And as the polars I showed clearly demonstrate, at some frequencies there are hot spots and at others there are weak spots. So a 90 degree horn is not full spl at all frequencies over the full 90 degrees and then zero spl at 91 degrees. Weltersys said a big horn with a big CD could cover 90 degrees up to 16 khz, I was just showing it's not as simple as that. Within the 90 degrees there is still directivity differences at different angles and frequencies and a definite beam on axis at the very high frequencies (at least with this type of waveguide - I'd like to see polars of a horn/CD combination that can do 90 degrees at 20 khz if anyone has an example, please).
I think I pretty clearly showed that a 90 degree horn can cover as narrow as 30 degrees at some frequencies, this has to be considered when placing and pointing the mains. Since the hot tub obviously has to be in the sweet spot, placement and pointing of the mains will make an incredible difference to the distribution of sound - different positioning and toe in will favor different areas. The close mains positioning favors a narrower and longer area in front of the horn axis. The wide mains positioning gives big dead spots in front of and behind the hot tub.
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Still only a short term solution. There's only so many rivers and once you dam them all up what's next? Energy demand forecasts that I've seen are in the 40 percent increase over 20 years ballpark, and that's in the 1st world countries that already have more than we need (need being very different than want). And in developing countries the demand is increasing at much higher rates.
Everything from the economy (and tax structures) to the consumer driven, marketing fueled, bottomless pit of constant consumption is aimed at constant and steady growth. We live in a finite space with finite resources, at some point constant and steady growth is not going to be possible. We've been able to keep on top of it for now by depleting resources and polluting the environment and becoming smarter with tech, but at some point we're going to consume ourselves into abject destitution.
This requires a paradigm shift from top to bottom, not damming every river on the planet in an effort to increase consumption even further. Toronto doesn't have anywhere to put their huge piles of garbage so they truck it out near me, 3 hours outside the city. This is madness on every level.
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in this case the sub itself is 30 feet wide, so the mains would not be far away, would it? Plus, as I pointed out in a previous post, when the mains are hoisted up, lobing will be primarily vertical
this kind of compromise happens all the time in the PA world.
EDIT: based on the design brief, this IS pretty much a PA, conventional HiFi thinking does not apply in some regards.....
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It's center to center distance that matters when calculating lobing. So yes, even if the sub horn is 30 feet wide and you put the mains right at the outside edges the center - center distance from each main to sub horn center is 15 feet in the horizontal plane, way more than the ideal 1/4 wavelength spacing so there will be lobing in the horizontal plane.
Priorities and compromises. Nothing is perfect but picking the right compromises to accomplish the main priorities is still pretty important unless you want a dozen fill speakers to fill in all the holes, which will present a whole other set of challenges while attempting to fix the first problem that could have been solved with proper design in the first place.
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