Really Don? the 100 horsepower number was a rough approximation to keep the math simple - as 10,000 cars rather "conveniently" equals 750 MW.
Let's assume my 100 HP estimate was 4 times too high. At 25 HP, we'd still need to build 87 nuclear plants, each sized 750 MW, requiring 573 pounds of uranium per day - just to get US cars off gasoline. At 25 HP, my point remains valid - which is that our present electric grid simply cannot support the wide-spread integration of electric cars - we cannot make the power, and we cannot route the power even if we could make it.
FWIW, a typical 15000 Btu automotive heater-core (in the dead of winter, heat turned up full-blast) will crank out about 4.17 Btu per second, which is equal to just under 6 horsepower (5.893 to be more precise). A continuous six horsepower draw isn't exactly water under-the-bridge - when you're pulling it from batteries. . . .
Ben,
Sound systems are not "smart" or "dumb", they simply come with differing levels of sensitivity.
By "true horn" you must be referencing the "full size" horns in this thread.
50 watts into an extremely large horn capable of 116dB using one watt at one meter would produce a shade over 131 dB at one meter using 50 watts, but Entropy Eric plans to listen to the horn around 24 meters distant, at which point the SPL will have dropped at 6 dB per doubling of distance to only 101 dB, not much on the excitement factor if he's been near the front rows of a Red Hot Chile Peppers concert, where LF levels can exceed 131 dB by a good margin.
To get the equivalent SPL of the 50 watt amp at one meter, at 24 meters will require 30 dB more power, 50,000 watts. That will require a lot more drivers than Entropy Eric's original plan, but larger drivers with more Xmax like the B&C18SW115-4 could do that SPL level with around 10 or so, using a mere 25,000 watts.
Taking the inverse, if a pair of drivers like the B&C18SW115-4 were used in a hot tub sized sub located 2 meters from said listening position, they could produce 131 dB output using around 6000 watts, that power only costs $450, and can easily be run using a 10AWG extension cord from the shop, or run off the same service that runs the hot tub that Entropy Eric has indicated will be his usual listening position.
Perhaps this little bit of math makes it clear why I have questioned the distant placement of the subs once Eric indicated the small nature of his desired listening location.
Cheers,
Art
It would be a very bad day if the air in your horn-throat went mach. . . . It would likely be the last thing you ever experienced. . . .
Eric,
That is exactly the reason my 600 watt 30MPH electric trike was only heated in summer and cooled in the winter 😉 .
The trike actually had to be geared down for a top speed of only 15 MPH to climb the mountain grades in Madrid, NM, but when I used the same motor with LiFePO batteries on a 2 wheel "moped" (that legal designation did not require registration or insurance there) it was capable of running at 25 MPH for 39 miles on a single charge, and could hit around 35MPH short term without popping the 50 amp breaker or overheating the "24 Volt" motor run at 48+ volts.
The bike only required an estimated $.5 to charge, and the LiFePO batteries only drop from 40AH to 33 AH after 2000 cycles, about 60,000 miles if using them to 80% discharge.
When the cycling longevity and almost complete lack of Peukert's effect are taken into account, even though the LiFePO batteries are several times the cost of lead acid batteries, they are a considerably better value.
The lack of Peukert's effect also allows the LiFePO batteries to deliver 10C peak amperage, the 52 pounds of 40AH batteries on the bike can deliver 400 peak amperes, 48,000 watts at 120 volts. With inverter and class D amplifier efficiency running around 80%, that little battery pack could deliver 28,800 watts to a speaker system.
Not quite up to your needs, but cost was only $890, you could afford more, and the solar panels and AC charger to charge them on rainy days, and have a silent back up AC power for when the grid goes down.
I was glad I had my solar system on my travel trailer (wish I'd not have sold those LiFePO batteries with the motorbike, the 72 pounds of AGM lead acid batteries in the trailer only store a fraction of the power) when hurricane Matthew recently took out power, I was able to keep the house refrigerator cool and did not loose any food, important since there were no stores open due to lack of power...
Art
I do not want 100 dB at 24 meters - thus I need to rethink my design.
Assume for the moment that I build a 25 kW bass horn, feeding (qty 10) B&C 18” drivers (which I am completely onboard with doing – because the ends justify the means. . . . . and because I like the idea of achieving concert-level sound – should the need arise. . .)
Question - for my highs, I was leaning towards Radian 850PB-8 drivers, with off-the-shelf rectangular cast-aluminum horns (unless I get really crazy, and fabricate some tractrix horns out of stainless). If I crossover the radians around 800 Hz, I can get about 138 dB (1 meter) without overload. I've read that although Radian advertises this horn driver as being able to hit 20 kHz (which I'm not sure I can even hear over 17 kHz anymore) - customer reviews have strongly recommended a 5 kHz low-pass, and running a dedicated bullet-tweeter from 5 kHz and up - which I might do. . . I was originally planning on two compression drivers for the highs (one Radian 850PB-8 per channel). If I design for 131 dB maximum acoustic output at 24 meters, what do I do with the Radians? I’d need at least four (maybe 5) 850PB-8 drivers per channel, right? Assuming I purchase the off-the-shelf rectangular cast-aluminum horn lenses, do I simply stack them vertically? Do I curve them a bit – to form a high-frequency horn array?
I currently own (qty 3) crown MT-3600VZ amplifies, (qty 1) crown MT-5000VZ amplifier, (qty 2) crown DC-300A-2 amplifies – all are available for this project – and I’m willing to buy more power if needed – MUCH more power if needed.
That being said - 131 dB at 24 meters (from 20 Hz up) seems like a pretty darn aggressive sound system. Would 121 dB at 24 meters still achieve the desired wow factor? And not require my guests to put in hearing protection when I’m throwing a summer party? I honestly don’t know the answer to this question – I don’t have a good engineering feel for how much SPL is required outdoors. . .
This SPL issue reminds me of speed boats. I used to be into jet boats big-time. I’ve owned a 50 mph boat, which was fast. I’ve owed a 70 mph boat, which was real fast. I’ve own a Jet boat that almost hit 80 – wow that sucker was real fast (and sucked a fantastic amount of fuel too). Then one day I purchased a 17 foot V-drive speed boat, and built a strong Pontiac 455 for it. That V-drive effortlessly hit 107 mph on hand-held GPS, the first time I took it out - which happened to be the last time I took it out. Nearing terminal velocity in a 17-ft boat is uncomfortable to say the least. . . . It was too much - even for me. .. .
I have found that in life that there's a balance between performance and pleasure. Generally speaking, the more the performance, the more the pleasure. However there comes a point where further increases in performance, will actually decrease the perceived pleasure. . . . I want to make sure that I’m keeping my SPL target goals in-check. . .
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I’m very familiar with the Maff curve – where the bottom octaves need to be disproportionally louder to achieve the same perceived loudness. This is why the bass drum at a concert can hit at 125 dB and sound good, and it’s a pretty safe bet that the electric guitar at 3 kHz is not cranking out 125 dB also.
The Maff-curve phenomena is very apparent if you’ve ever visited the ultra high-end stereo stores, with the 145 thousand dollar master-reference Krell amplifiers, hooked up to the fantastically expensive full-range reference speakers. Don’t get me wrong, they sound fantastic - however the bottom end is simply lacking compared to what you hear at a concert. A flat 93 dB (or whatever the reference setting is) from 20 Hz to 20-kHz simply does not sound good to me. When you crank these systems up enough to have the kick-drum actually “kick”, the vocals are loud enough to make your ears ring. This is why I build my own systems. I have learned to simply add drivers on the bottom end, and with active crossovers, it’s very easy to increase power to the lower octaves until it sounds good.
I’m sorta planning on doing the same thing with this outdoor system. The bass horn is the only thing I need to get right the first time around (because I’m literally casting it in concrete). Everything else is a variable that I can tweak as needed. I’m assuming I’ll be building several iterations of midrange horns – before I find something that I’m happy with.
The Maff-curve phenomena is very apparent if you’ve ever visited the ultra high-end stereo stores, with the 145 thousand dollar master-reference Krell amplifiers, hooked up to the fantastically expensive full-range reference speakers. Don’t get me wrong, they sound fantastic - however the bottom end is simply lacking compared to what you hear at a concert. A flat 93 dB (or whatever the reference setting is) from 20 Hz to 20-kHz simply does not sound good to me. When you crank these systems up enough to have the kick-drum actually “kick”, the vocals are loud enough to make your ears ring. This is why I build my own systems. I have learned to simply add drivers on the bottom end, and with active crossovers, it’s very easy to increase power to the lower octaves until it sounds good.
I’m sorta planning on doing the same thing with this outdoor system. The bass horn is the only thing I need to get right the first time around (because I’m literally casting it in concrete). Everything else is a variable that I can tweak as needed. I’m assuming I’ll be building several iterations of midrange horns – before I find something that I’m happy with.
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Perhaps I need to reevaluate my planned listening distance. The 24 meter setback was assuming a pair of large stereo bass horns, spaced 60 feet apart at the mouth.
Now that I'm leaning towards building just one bass horn, I see no reason why I cannot converge the listening area closer to the horn.
If spaced my mids & highs about 30 feet apart, the sweet spot would be about 30 feet in front of the bass horn mouth. I'd still cover a decent listening footprint for throwing the occasional party, and my overall SPL (source) requirements would drop. . .
Don Hills has got me thinking - (I’m sorry, I’m back on the electrical car tangent. . . .)
One of my cars (a 2006 V6 Ford Mustang) weighs approximately 3500 pounds, and has a 210 horsepower gasoline engine, with 5-speed manual transmission. I am trying to visualize pulling the 210 HP engine, and replacing it with the 25 HP engine from my riding lawnmower. Could I actually hit freeway speeds in a 3500-lb mustang with a lawnmower engine? My gut tells me no way. I hate to talk smack about Ford, but my Mustang is a bit of a dog when it comes to acceleration. It is a far cry from what I’d call peppy. The car can hardly get out of its own way when you go to pass (that's probably because I also have a 1974 Firebird with a 440 horsepower Pontiac 455 under the hood, and I'm slightly biased as to what passing power should be. .. . ) But I digress.
The easiest way to directly measure the actual drag-force power requirements of any car, would be to simply pull it down the road (a pickup truck would work well). The pull vehicle would need to be far enough ahead, so as to not provide any help from cutting the wind in front of the test-car (which is cheating - - - NASCAR!). You’d simply pull the test-car at steady speed using a small steel cable (obviously keeping the cable off the road). Using a pull-scale, you’d directly measure the drag-force pull in pounds. The power required to move the car down the road is simply the measured pull-force (lbf), times the vehicle’s speed (mph). You’d have to convert mph to ft/s, and apply a conversion factor to get horsepower – but it’s a pretty straight forward calculation. Nonetheless, I am NOT going to swap my V6 with a lawnmower engine, and I’m way too lazy to coordinate pulling my car down the road with a steel cable - simply for the point of this discussion. . .
That being said, I might be able to reverse-engineer the number - Ford says my car gets 28 mpg on the freeway, which is a complete load of crap. I get 20 mpg on a good day – maybe 22 if I drive like a grandpa . . . A gallon of gasoline has about 115,000 BTU, and I’m burning a gallon about every 20 minutes on the freeway, which is 95.83 BTU per second. This BTU consumption equals 135.5 horsepower of heat input. My Ford engine is nothing fancy – aluminum block, aluminum heads , a single overhead cam – I’ll assume an average automotive thermodynamic efficiency of 28%. Where 28 percent of 135.5 is 38 crankshaft horsepower). Assume a 5% loss in the transmission, and 3% loss in the differential, the actual power required to move my 3500-lb Ford Mustang at freeway speeds is about 35 horsepower.
35 is more than 25, and less than 100. . . Perhaps a better first-approximation would’ve been to use 35 horsepower. . . . (or 41 horsepower with the heater on .. . . )
One of my cars (a 2006 V6 Ford Mustang) weighs approximately 3500 pounds, and has a 210 horsepower gasoline engine, with 5-speed manual transmission. I am trying to visualize pulling the 210 HP engine, and replacing it with the 25 HP engine from my riding lawnmower. Could I actually hit freeway speeds in a 3500-lb mustang with a lawnmower engine? My gut tells me no way. I hate to talk smack about Ford, but my Mustang is a bit of a dog when it comes to acceleration. It is a far cry from what I’d call peppy. The car can hardly get out of its own way when you go to pass (that's probably because I also have a 1974 Firebird with a 440 horsepower Pontiac 455 under the hood, and I'm slightly biased as to what passing power should be. .. . ) But I digress.
The easiest way to directly measure the actual drag-force power requirements of any car, would be to simply pull it down the road (a pickup truck would work well). The pull vehicle would need to be far enough ahead, so as to not provide any help from cutting the wind in front of the test-car (which is cheating - - - NASCAR!). You’d simply pull the test-car at steady speed using a small steel cable (obviously keeping the cable off the road). Using a pull-scale, you’d directly measure the drag-force pull in pounds. The power required to move the car down the road is simply the measured pull-force (lbf), times the vehicle’s speed (mph). You’d have to convert mph to ft/s, and apply a conversion factor to get horsepower – but it’s a pretty straight forward calculation. Nonetheless, I am NOT going to swap my V6 with a lawnmower engine, and I’m way too lazy to coordinate pulling my car down the road with a steel cable - simply for the point of this discussion. . .
That being said, I might be able to reverse-engineer the number - Ford says my car gets 28 mpg on the freeway, which is a complete load of crap. I get 20 mpg on a good day – maybe 22 if I drive like a grandpa . . . A gallon of gasoline has about 115,000 BTU, and I’m burning a gallon about every 20 minutes on the freeway, which is 95.83 BTU per second. This BTU consumption equals 135.5 horsepower of heat input. My Ford engine is nothing fancy – aluminum block, aluminum heads , a single overhead cam – I’ll assume an average automotive thermodynamic efficiency of 28%. Where 28 percent of 135.5 is 38 crankshaft horsepower). Assume a 5% loss in the transmission, and 3% loss in the differential, the actual power required to move my 3500-lb Ford Mustang at freeway speeds is about 35 horsepower.
35 is more than 25, and less than 100. . . Perhaps a better first-approximation would’ve been to use 35 horsepower. . . . (or 41 horsepower with the heater on .. . . )
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Just some thoughts.
Hi Entropy455,
Think about it as a 4-way system. Your choice where to put the break points. I do not find the suggestion of 130dB in the listening area reasonable. It takes 20dB more power to go from 1m to 20m, it takes 6dB more power to go from 20m to 40m.
Regards,
P.S.: http://www.gcaudio.com/resources/howtos/loudness.html
Hi Entropy455,
Think about it as a 4-way system. Your choice where to put the break points. I do not find the suggestion of 130dB in the listening area reasonable. It takes 20dB more power to go from 1m to 20m, it takes 6dB more power to go from 20m to 40m.
Regards,
P.S.: http://www.gcaudio.com/resources/howtos/loudness.html
Attachments
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My intuition (which I openly admit is rather novice in this realm) is that my listening area needs about 120 dB in the bottom 3 octaves, and about 105 dB in the mid/high octaves - for desired backyard get-togethers / parties. And for easy listening while soaking in the hot tub with the wife, I could probably drop those values by 15 dB across-the-board (i.e. turn the volume down).
Opinions?
Opinions?
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I just read that a 16" battleship gun (with a 660 pound firing charge), will produce a 190.7 dB sound pressure when fired. That's amazing. . . I had to share. . . .
It's no wonder the battleship veterans are deaf - even the cooks. . . .
I've also read that if you are topside when one of these guns fires, the sound will cause internal bleeding, resulting in death. . .
For the record - I've just made an official concussion that 190.7 dB is too loud for a stereo system. . . . .
It's no wonder the battleship veterans are deaf - even the cooks. . . .
I've also read that if you are topside when one of these guns fires, the sound will cause internal bleeding, resulting in death. . .
For the record - I've just made an official concussion that 190.7 dB is too loud for a stereo system. . . . .
Figuring the HP required to keep the Mustang at speed will be a WAG in my opinion since there are so many variables.
It takes about one half pound of gasoline per horsepower hour and more if there is any ethonaol in the mix.
If you have a scanner you can read the MAP (manifold absolute pressure) while driving on level ground with no wind at the speed you want to calculate drag, load the car on a chassis dyno and load the dyno to hold the car at that speed and MAP, the wheel HP calculated back to crank HP is your answer.
Back to the audio quest:
Seems to me a some of the volume variables need to be defined which would require a quality SPL meter and at least one walkabout field trip to some out door live performances.
Figure out how loud you really want it to play. The rest is just math.
I have a large format outdoor system with four RCA 9462 bass horns. This constitutes two bass horns that measure 7' square and are very nearly flat to 40Hz. With eight JBL 2226's and just over 11,000 Watts of power they play as loud as I ever want them to for maybe one adrenaline rush song and then it is down in the low 100dB SPL range.
The mid bass is two horn loaded JBL 2220's each side and one JBL 2450SL on a 60 degree radial. It is amazing how loud this stuff will play and sound good when your not trying to cover a large area or crowd.
When this is turned up to the subs limit most people find their confortable distance between 50-70 feet with a few of us more like 30' and others near 200'
That said, I sure as hell would like a full size 20Hz bass horn!
Oh yeah, your shop being at a angle oblique to your listening area should pose you no problems. Being in the controlled coverage area of large format horns outdoors is somewhat similar to headphones in the respect that there is such a big difference in amplitude between in or out of coverage that the rest of the world goes away.
Following along with interest!
Barry.
It takes about one half pound of gasoline per horsepower hour and more if there is any ethonaol in the mix.
If you have a scanner you can read the MAP (manifold absolute pressure) while driving on level ground with no wind at the speed you want to calculate drag, load the car on a chassis dyno and load the dyno to hold the car at that speed and MAP, the wheel HP calculated back to crank HP is your answer.
Back to the audio quest:
Seems to me a some of the volume variables need to be defined which would require a quality SPL meter and at least one walkabout field trip to some out door live performances.
Figure out how loud you really want it to play. The rest is just math.
I have a large format outdoor system with four RCA 9462 bass horns. This constitutes two bass horns that measure 7' square and are very nearly flat to 40Hz. With eight JBL 2226's and just over 11,000 Watts of power they play as loud as I ever want them to for maybe one adrenaline rush song and then it is down in the low 100dB SPL range.
The mid bass is two horn loaded JBL 2220's each side and one JBL 2450SL on a 60 degree radial. It is amazing how loud this stuff will play and sound good when your not trying to cover a large area or crowd.
When this is turned up to the subs limit most people find their confortable distance between 50-70 feet with a few of us more like 30' and others near 200'
That said, I sure as hell would like a full size 20Hz bass horn!
Oh yeah, your shop being at a angle oblique to your listening area should pose you no problems. Being in the controlled coverage area of large format horns outdoors is somewhat similar to headphones in the respect that there is such a big difference in amplitude between in or out of coverage that the rest of the world goes away.
Following along with interest!
Barry.
How loud would you say your system is when you’re pushing the “average” listener to a stand-off distance of 50 to 70 feet (i.e. what would you estimate the SPL to be within the actual listening area)? This value would probably be a realistic design goal for my listening area. And I might be able to do it with the amplifiers I already have. . .
I hadn’t thought of using a dyno to map the power curve with respect to fuel-injection settings - then reading the fuel-injection parameters on-the-road for a direct energy/power comparison. That’s a good idea, and it’s a lot safer than towing a car at freeway speeds with a steel cable. . . . .
Below is an intake I built for one of my jet boats (Caddy 500). I also built the red press. I’ve yet to retrofit an old engine with modern fuel injection. That's another item on my bucket list. . . .
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Eric,
1) As stated before, "concert level" in the front rows of a RHCP concert can go well above 131 dB, though the cabinets used by Dave Rat don't go much below 35 Hz, reducing the size needed to produce around 140 dB by a huge factor.
2) 138 is a theoretical number based on power handling and sensitivity. In reality, the non-linear nature of air when nearing 160 dB in the throat (easy to figure using the inverse square law, and I have confirmed the levels by measurement exceed 160 dB well below thermal limits) limits output to a few dB less than theoretical, and although the Radian and other drivers voice coils can survive the thermal demands, they will start to sound horrible (distortion well in excess of 10%) at a fraction of their rated power. The splitting up of the frequency range using two HF drivers is the "classic" way to mitigate the distortion problem.
3) Generally speaking, most concert systems HF output is 10-15 dB less than the low frequency, and depending on how much of a LF "haystack" employed, may be closer to 20-25 dB less. As the saying goes "tweeters don't get the party going, it's all about the bass".
That said, to keep the HF "clean" will require several HF drivers per bass driver. To deliver non- interfering, summed HF response using multiple horns requires them to be designed for the purpose intended, either using multiple very narrow HF devices (like my "Maltese" 11x11 degree horns with 115dB one watt one meter sensitivity) or narrow vertical throat adapters such as the 1992 "Vdosc" line array patents describe, or any number of others developed by competing companies to effect the same end. The choice then becomes whether you go point source, with less throat distortion, but worse polar response, or use the HF line array approach.
Having used Tom Danley's "Paraline" HF horn coupling in a small format horn loaded line array, and the Maltese horns, which are the cleanest sounding horns I have experienced, regardless of designer, I can say with no reservations that the Paraline sounds better in multiples than the narrow, "non overlapping" approach. That said, if you placed the system near the listening position, a pair of 3" diaphragm drivers on a horn of the proper dispersion to cover the area will sound better than any multiple driver system from a distance, unless you are after the reverberation such a distance will afford.
4) 121 dB in the bass range is about 20 dB less than at a loud concert. It only takes a 6 dB reduction in SPL at 40 Hz to sound half as loud. Do the math, measure your wife's bass rig, and answer for yourself.
5) The loudest events I ever did sound for were providing public address for the Formula boat races popular in the early part of the 1980s. Watching those boats skimming the water at over 100MPH was both exciting and deafening, even wearing ear plugs and ear muffs, about 50 dB attenuation. On a related boat note, most of my boating has been on displacement sailboats, the last one was a fairly light, water-ballasted Catalina 250. With a stiff downwind breeze, it could be pushed above hull speed, transitioning from 5 mph to 7 mph made the boat "feel" like the difference between a 1970s Caddy and riding a roller coaster. From boring to exciting in a 2 mph range...
6) Back in the days when selling sound by the pound, we routinely measured 120 dBA and 126+ DBC (+ because the SPL meter "pegged" at 126 dBC) at the mix location in First Avenue. By the way, you can see Prince humping my H34 speakers in the movie "Purple Rain" filmed there, they edited out him humping my earlier fiberglass low mids, evidently looked a bit too graphic even for the Purple One.
Although the EV line array system now in First Avenue has more than an order of magnitude more power potential (over 100,000 watts, compared to 8000 back in the day) the "A" scale (rolling off below 1kHz) SPL readings are still much the same, though for certain genres of music the "C" scale is higher. I could check with my former employee Greg Huber, who has been operating (and owning a portion of) the system there for many decades since I sold STS as to the exact levels, but I know the old EV LF cabinets in the club do not have near the potential of modern designs and drivers used in other venues.
At the more family oriented music shows I currently do sound for, I seldom exceed 110 dBC, or 90 dBA. I no longer can tolerate much more than 95 dBA "slow" for more than a short period of time, so I don't work the type of shows where that is typical any more. It is nice having arrived at a point in my life I can do what I want.
7) I have the same car, looks great, but is a pig aerodynamically. Although I have been able to get 25 MPG on occasion with the 2006 Mustang (but only 19 MPG on my last fill..), our 2015 Subaru Outback, about the same length, 2700 pound tow capacity (compared to only 1000), heavier, but with way more interior space, routinely gets over 30 MPG. I'd say your estimate of the Mustang needing 35 HP at freeway speeds is good, but don't get me started about why they computer limited it's top speed to 115, rather than fixing the drive-line imbalance, the "speedy" Mustang is the first car I owned that could not "bury the needle" on the speedometer. I was disappointed the first time I wound it out, and felt like the brakes had been hit when the limiter kicked in, while there was still loads of RPM left before red-line.
8) Yes. We used to "scooter tow" our hang gliders in to the air when we did not feel like jumping off cliffs. The scooter tow rig consisted of a 250CC variable transmission using the rear wheel as a rope drum. The tow operator would pull the hang glider into the air by judicious application of power, enough to get the glider airborne, but not too much to overpower it and make it go "squirrley", like a boat driven above hull speed. Power needed to get pilots 1000 feet in the air could be as little as a few horsepower, or as much as the scooter could put out with the throttle wide open, dependent on the type of glider.
9) An excellent book that goes into detail of getting the most with the least amount of motive power is "Bicycling Science" by Frank Rowland Whitt and David Gordon Wilson. The third printing in 1985 predicted the ultimate human powered speed record to be in the range of Todd Reichert's current (2016) 89.58 mph (114.17 km/h) unpaced faired recumbent bicycle world record, but it took a while for the right machine and the right rider to be created.
I could easily ride at 25 mph on my recumbent, but can only hit 20 mph on my semi-recumbent mountain bike.
Having already dispensed a plethora of free information, (you get what you pay for ;^) ) please contact me directly if you'd like to hire me for further audio consultation.
Cheers,
Art
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Now, there's an important data point.
SPL meters are cheap. I seem to recall finding my cellphone meter reasonably close to my Radio Shack meter. Crank up your volume and see what you get. As I said, the levels advocated at this forum are not connected to reality. Going over 100dB (maybe A or maybe C) is really loud.
Since Art is into reminiscences, I was an Expert Witness on a case involving a young man who fell to his death during a rock concert by Ted Nugent*. So I can tell you, crazy loud music can have bad consequences.
Ben
*Montreal Forum. Yes, they had to pay me to attend. Had to sneak in my gear.
Here's the upbeat and life-affirming thoughts that Nugent says about his severe hearing loss, " "The ear's not too good, especially with background noise, but that's a small price to pay. Believe me the journey was worth it". Not my kind of life-affirmation.
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Hi Art,
Do you think some type of long-throw Synergy horn might be a good choice for this application? Maybe something like multiple SH-25? You did a lot of research when building your SynTripP, how would the multiple range horn compare to individual front loaded horns?
Regards,
P.S.: At least the sub 100Hz bass seems covered. 🙂
Do you think some type of long-throw Synergy horn might be a good choice for this application? Maybe something like multiple SH-25? You did a lot of research when building your SynTripP, how would the multiple range horn compare to individual front loaded horns?
Regards,
P.S.: At least the sub 100Hz bass seems covered. 🙂
Woah, pump the brakes there big guy.
I've dispensed a lot more free information than anyone else in this discussion and was prepared to go all the way but was forced to leave due to free time issues resulting in my inability to defend my common sense data points on the dumb burning man horn, which you and hollowboy were determined to fight for out of spite.
Let's not forget this little gem from a couple of weeks ago.
That is an outright admission that you are in no way qualified to design a full size horn. Nothing you've said since then changes anything. You don't know how they work, you are not very comfortable with simulators and I am confident that you've never even tried to use the "system design" tool which can give you ideal specs for the driver and the horn.
While you are good at what you do, what you do has nothing to do with full size horns.
And by the way, let's look at what the other guys that voted me out of this discussion have to say.
Oh yeah that's right. Hollowboy has nothing to say about anything except the dumb burning man horn.
Every time Ben is asked a direct question this is always his answer, he doesn't have one. He answered similarly about the compression ratio issue admitting he hasn't got a clue.
In the meantime, Ben's only contribution is showing up to question the knowledge of the people that are providing meaningful input, and ranting on his dogma. How many times has he criticized moving coil drivers now? I told you this was going to happen from the beginning. He adds no value.
Sitting back and watching this train wreck since I stopped contributing has been entertaining. You guys are rehashing points I made 2 weeks ago about efficiency and other details (some people are still not on the right track) and making no forward progress. As for the new stuff, people don't seem to be aware that a system capable of 130+ db doesn't need to be powered to that level, but if you want clean sound at lower volume and ultra low THD you do need the system to have incredible amounts of unused headroom. Drivers start to sound bad about half way to xmax.
AND NOW YOU WANT TO GET PAID FOR IT. Despite the fact that you openly admitted you don't know anything about full size horns.
I said I wasn't going to help anymore and I'm not but I will give the OP this one bit of advice. Take your stereo outside and listen to it. It will answer most of your questions. Put the subs 18 meters apart and play some bass tones, maybe pink noise. Walk around and find out how lobing is affecting things by making massive dead spots. Stand up close to one of the speakers and then walk back 20 meters to the proposed listening spot and see if it really sounds better back there. Crank the volume and see if it's loud enough ANYWHERE to be impressive. Never mind the listening position, see if you can sit right in front of it and be even mildly impressed. Find out if the reflections off the barn make any difference at all. If you build a 30000 liter horn (or even two 30000 liter horns) and it can only do 120 db at the listening position with 10 percent THD I don't think anyone is going to be even mildly impressed. Especially your engineer friends. It's kind of like putting a motorbike engine in a tank. Sure you can make something that will work but it's performance is a joke compared to what it could be (or should be), a total waste of resources.
This discussion can't go any further than diversions into alternative energy and gas mileage because very few people here are qualified to push the discussion forward and those that are are only talking about details, not the actual design of the project (tb46, David McBean for example), and you've purposely alienated me from the discussion out of petty spite.
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Hi JAG,
Post #377: "...Take your stereo outside and listen to it...."
That has been suggested before, and that's what we are waiting for. So, it looks to me that we are just kicking around rocks while trying to maybe narrow the system specifications/locations/... a bit more. 🙂
Regards,
Post #377: "...Take your stereo outside and listen to it...."
That has been suggested before, and that's what we are waiting for. So, it looks to me that we are just kicking around rocks while trying to maybe narrow the system specifications/locations/... a bit more. 🙂
Regards,
Hi entropy455,
I just have to comment on the photograph in Post #373. That's beautiful artwork. Very impressive.
Regards,
I just have to comment on the photograph in Post #373. That's beautiful artwork. Very impressive.
Regards,
I reluctantly agree. I say reluctantly, because the bass-reflex enclosures are quite heavy. It’s also the rainy season here in Seattle. I actually moved them into my house from the garage using my forklift. But no more excuses – this weekend (weather permitting) I will take them outside, and take the Pepsi challenge. I can tell you that inside the house (playing CD music), these things go well past what I consider the comfort threshold for "too loud". I’m embarrassed to say that I do not currently own an SPL meter. Maybe it’s time to hit up Amazon, and make this an official test.
I appreciate all feedback I’ve received to date – yes, even Don Hills poking me in the eye – I appreciate you too Don. . . . Just-a-guy, you were able to show that boundary conditions directly impact (and rather dramatically impact) the throat impedance of a bass horn – a concept that I was having much difficulty in accepting as fact. Weltersys, you have real-world sound reinforcement experience, which is nothing short of invaluable. You’ve also given me sound advice (pun intended) – in that that you’ve directed me towards excellent starting points for constructing my highs (Maltese, Vdosc, Paraline, etc) – thank you! Thank you David McBean for the awesome Hornresp software, and thank you to everyone else who I haven’t named, for constructively contributing towards this thread.
Although my degree is in Mechanical Engineering, I am confident that I’m able to tackle this project. The top of the horn is a high-risk structure – i.e. a load-bearing slab in bending-tension, simply supported on ends. I need to determine the required slab thickness, rebar size, and rebar placement - to ensure adequate bending inertia and acceptable bending stress – and ultimately ensure there’s an adequate design Factor-of-Safety. The horn could quite literally kill someone if it catastrophically failed. A friend of mine holds a Structural Engineering PE stamp (Washington State) and will be formally second-checking my design work.
Now that I’m only building one horn, my costs are going way down on this project. I’m building a square mouth horn (possibly somewhat rectangular). The horn will require four pours. The first will be a pair of heavy-duty reinforced footers, running the entire length of the horn – an abutment of sort. The vertical horn walls will be supported by the footers, and specifically not the bottom slab-portion of the horn. The bottom slab of the horn will be constructed similar to a reinforced slab-on-grade. This pour will not have much super-plasticizers in the mix. The vertical rebar will already be cast into the bottom-slab, and more importantly, into the footers. The vertical walls will then be formed using a super-plasticizer mix. The rebar tying into the overhead will be preset into the vertical walls. After the walls have cured for a few weeks, I’ll remove the forms, pull over the rebar, and form up the overhead. The overhead will be placed from above - similar to a slab-on-grade, except heavily reinforced (for a load-bearing slab simply supported on ends). This will require a pretty fantastic amount of shoring up from below, as I’ll be supporting several tons of essentially liquid mud (until it cures). The small end of the horn will likely be cast as a whole when I do the vertical walls. I’m not overly concerned about the cold-joints, as I intend to use a lot of rebar throughout. I will however look into joint sealing techniques nonetheless, as it would be silly to have an air leak at a cold joint, when it could’ve been prevented with trivial amounts of corrective action during the casting process. I’ll be purchasing a concrete vibrator for this project.
After the concrete is just cured enough to walk on, I’ll put down cloth and keep it wet with the sprinkler. The forms will stay in place for weeks between pours, as this project is far from being under the clock. Most of the horn will be backfilled & buried (after a full month of curing). I’ll use a tar-type sealant on the concrete, and a curtain drain (clean washed river rock, perforated drain tube, with landscape fabric) adjacent to the horn footers, so that I don’t have standing water below grade.
I was originally prepared to build a pair of 20-Hz horns (25 feet long, with 18 foot diameter mouths). Now that I’ve had a come-to-Jesus realization that half-space horns really only need half the mouth area (thank you just-a-guy) - and that just one horn will eliminate a lot of potential lobing problems - my project suddenly seems very small. However if I stick with my original plan to make 18 foot diameter horns (just one), and I extend the length the horn to 62 feet, I get a 10 Hz tune in half-space. Is this a complete waste of steel & concrete, maybe? I’d personally like to hear (or rather feel) a horn sweep from 100 Hz down to 10 Hz with authority – just one time would justify the cost of this project. My wife’s bass guitar speakers turn off like a switch at 30 Hz. Perhaps I should seek a happy medium, and build a 40 foot long horn, with a 13 foot diameter mouth (14 Hz tune) . . . What to do, what to do, what to do. . . .
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