If you look at the Direct sims I posted you will see that above about 100 hz even in the hottub the people that are not directly on axis will be sitting in a 20 db null at those frequencies. Call it comb filtering or lobing, I would say it matters a lot.
Hi Bob,
Thanks for reminding me of the link, I hadn't noticed it the first time. It is difficult to derive clear conclusion from the article though, will have to chew on it a bit.
About the endless discussion of lobing, let me try again to explain why your eye and your ear do not hear the same - or why some folks can produce a mountain of information without an inch of understanding its relevance.
In the first figure, I show a woofer of mine with no smoothing. Holy smokes, there's a 25 dB hole! Truth is, real-world acoustic data like this always looks horrible. But honest to the facts as the mic hears 'em.
In the second figure, there is "1/6" smoothing which means the software takes a few Hz's (1/6 of an octave only) and does a running average. The second figure sort of honestly characterizes the sound in a way that the first does not and the way the fancy lobing diagrams do not either. Actually, it would be even more honest to the listening experience if I took three runs and smoothed them and averaged all them together... and depending on where I put the mics, might have no hole at all.
If you have discrete frequencies, there will be little holes where low loudness will be measured. And as the guitar player moves their fingers a minute amount to change the note ever so slightly, that location will shift around (because the NOTE just changed a tiny bit) and nobody will ever notice a thing because it is all shifting about all the time and there is no mental standard for what that note at that instant OUGHT to sound like for that instant in that seat at those finger pressures. And so too will the particular seat in your living room where the low loudness occurs.
(Yes, for a whole range of reasons, a room or a stadium can have a seat where the sound is awful. For example, under the balcony overhang in Orchestra Hall in Chicago (and all other overhangs too). Good reason for sound techies to walk about and check the sound. But that has nothing to do with the menacing lobing diagrams or fantasy beliefs in evil comb filtering folks have been posting. Minor issues.)
Ben
In the first figure, I show a woofer of mine with no smoothing. Holy smokes, there's a 25 dB hole! Truth is, real-world acoustic data like this always looks horrible. But honest to the facts as the mic hears 'em.
In the second figure, there is "1/6" smoothing which means the software takes a few Hz's (1/6 of an octave only) and does a running average. The second figure sort of honestly characterizes the sound in a way that the first does not and the way the fancy lobing diagrams do not either. Actually, it would be even more honest to the listening experience if I took three runs and smoothed them and averaged all them together... and depending on where I put the mics, might have no hole at all.
If you have discrete frequencies, there will be little holes where low loudness will be measured. And as the guitar player moves their fingers a minute amount to change the note ever so slightly, that location will shift around (because the NOTE just changed a tiny bit) and nobody will ever notice a thing because it is all shifting about all the time and there is no mental standard for what that note at that instant OUGHT to sound like for that instant in that seat at those finger pressures. And so too will the particular seat in your living room where the low loudness occurs.
(Yes, for a whole range of reasons, a room or a stadium can have a seat where the sound is awful. For example, under the balcony overhang in Orchestra Hall in Chicago (and all other overhangs too). Good reason for sound techies to walk about and check the sound. But that has nothing to do with the menacing lobing diagrams or fantasy beliefs in evil comb filtering folks have been posting. Minor issues.)
Ben
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All you need to do is look at the frequency response graphs Bob posted to see that the frequency response is completely different depending on where you are located to know that these are not minor issues.
The issue is quite similar to bass in a small room with a single sub. You can stand in the corner and you can stand in the middle of the room and get completely different frequency response. And the difference between these two in room locations is about the same difference as the frequency response graphs Bob showed (20 db dips).
Huge amounts of research have been done in the field of smoothing response in small rooms because it's a huge problem. And the magnitude of the problem is similar to the problems shown in Bob's frequency response graphs.
And since there's a super simple fix to the problem (don't use dual subs spaced 60 feet apart) there's no reason not to apply that fix.
The graphs you just posted show a very benign dip in comparison to the ones Bob showed, even the deep one is only half as deep and not nearly as wide as the comb filtering Bob showed.
Ben I'm really curious to know your ideas on how this system should be designed. So far you have not given a single shred of constructive input. All you have done is criticize ideas that have already been presented. If you were to design this system what would it look like? Let's have some details please.
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the interference patters happen no matter if there are reflecting boundaries up close or not.
In an indoor situation boundary reflections would make the whole situation more complex, but it still wouldn't change the basic mechanism of how the multiple discrete sources interact.
Great thread ! Awesome project !
I totally get the excitement in trying to make something seldom seen or heard...go Entropy455 go !
OK, a little background, then my 2 cent recommendations....
I've been toying with powerful outdoor playback for almost 20yrs.
First go was a pair of meyer mts4a's. Killer good sound, very powerful full range boxes, but clearly needed more bass outdoors.
So I built 4 Labhorns, soon after their plans were posted. Excellent, but now needed more space away from residence to get rid of reverb reflections.
Lived on a 145 acre farm, and built a soccer field / pavillion for a local travel team, with audio goals being a big part of the design. Got electrical power, big open listening space, equipment storage, ....and importantly...help legitimizing the high SPL levels..zoning was a bitch !
Sold the farm, and found myself unwilling to lug the 280lb mts4a's outdoors at my new residence.
I've just lived with smaller mains,until I saw Peter Morris's DIY mid-high. Now use both 60 and 90 degree versions over the 4 Labs along with two more similar horn subs (JTR) which play remarkably well with the Labs....
Processing is miniDsp, a 3 box setup that has let me play with all kinds of setups, as well as experimenting with flattening phase down to about 30hz..
OK, if I was in your beautiful position of contemplating such a low extension sub outdoors....
Well....I'd first resolve the conflicting goals of how loud do I want to be at my listening distance, vs what does that mean for the neighbors, like carneoleon brought up.
Because IMO that equates to how often do I honestly get to crank at desired levels.
I've learned that the 'whenever you hear music, you're invited' idea works, but.......all it takes is ONE disgruntled neighbor, and Mr Sheriffff shows up ....
Then, like 1audiohack mentioned, figuring out exactly how to get full range SPL. Which to me means, am I gonna go store bought for the mains, or DIY.
If DIY, I second tb46's thoughts on a 4 way system with each passband spanning 2-3 octaves. But I must admit, the right Danley box sounds mighty tempting here.
If using a mono sub (which I probably would), I'd do a LCR arrangement, where L and R are flown, and C sets on top of the sub. This way I could play with both worlds, stereo and close-coupled mono. I've played with these alternatives a lot, and am still without conclusion. Some tracks sound better mono, some stereo,.. some with subs center clustered, some with stereo subs...all outside...go figure..
I certainly dunno know exactly what freq localization begins, but THX certification requires requires 80hz x-over IIRC. I cross at 100hz with the DIY's to be excursion safe, and at 80hz with the big meyer's. Again, no conclusions...
Oh, one piece of conventional placement wisdom I do like is the stereo isosceles triangle....it gives impressive imaging out of the DIYs. But this setup has a heavy hand in determining optimal listening distance. 16m triangle legs have been about my max working distance for this
Listening levels: I'd say depends on how much I like the song, and how much I like the wine 😀
90dB SPL flat to maybe 115. 105 is an exciting fun number for most guests IMO.
And really, 105dB at 16m is 139 at 1m. That's a heck of a lot harder for the mains than it looks if you want really clean sound. If I'm trying to show guests clean maximum impact, we move up to within at least 8 meters....
Processing: totally depends on mains decision IMO. If you go DIY, miniDsp is a great tuning platform, with both IIR and FIR capability. If you go store bought, just get a decent processing amp like ItechHD or qsc pld. If you don't go DIY, I'd pass on miniDsp due to its consumer output levels.
Anyway, best of luck, hopefully all my rambling added up to 2c !
Oh, PS....make sure to think thru nearby structure resonances..the labhorns rattled the ever loving poop out of the picnic shelter's roof at the soccer field..big design overlook...
I totally get the excitement in trying to make something seldom seen or heard...go Entropy455 go !
OK, a little background, then my 2 cent recommendations....
I've been toying with powerful outdoor playback for almost 20yrs.
First go was a pair of meyer mts4a's. Killer good sound, very powerful full range boxes, but clearly needed more bass outdoors.
So I built 4 Labhorns, soon after their plans were posted. Excellent, but now needed more space away from residence to get rid of reverb reflections.
Lived on a 145 acre farm, and built a soccer field / pavillion for a local travel team, with audio goals being a big part of the design. Got electrical power, big open listening space, equipment storage, ....and importantly...help legitimizing the high SPL levels..zoning was a bitch !
Sold the farm, and found myself unwilling to lug the 280lb mts4a's outdoors at my new residence.
I've just lived with smaller mains,until I saw Peter Morris's DIY mid-high. Now use both 60 and 90 degree versions over the 4 Labs along with two more similar horn subs (JTR) which play remarkably well with the Labs....
Processing is miniDsp, a 3 box setup that has let me play with all kinds of setups, as well as experimenting with flattening phase down to about 30hz..
OK, if I was in your beautiful position of contemplating such a low extension sub outdoors....
Well....I'd first resolve the conflicting goals of how loud do I want to be at my listening distance, vs what does that mean for the neighbors, like carneoleon brought up.
Because IMO that equates to how often do I honestly get to crank at desired levels.
I've learned that the 'whenever you hear music, you're invited' idea works, but.......all it takes is ONE disgruntled neighbor, and Mr Sheriffff shows up ....
Then, like 1audiohack mentioned, figuring out exactly how to get full range SPL. Which to me means, am I gonna go store bought for the mains, or DIY.
If DIY, I second tb46's thoughts on a 4 way system with each passband spanning 2-3 octaves. But I must admit, the right Danley box sounds mighty tempting here.
If using a mono sub (which I probably would), I'd do a LCR arrangement, where L and R are flown, and C sets on top of the sub. This way I could play with both worlds, stereo and close-coupled mono. I've played with these alternatives a lot, and am still without conclusion. Some tracks sound better mono, some stereo,.. some with subs center clustered, some with stereo subs...all outside...go figure..
I certainly dunno know exactly what freq localization begins, but THX certification requires requires 80hz x-over IIRC. I cross at 100hz with the DIY's to be excursion safe, and at 80hz with the big meyer's. Again, no conclusions...
Oh, one piece of conventional placement wisdom I do like is the stereo isosceles triangle....it gives impressive imaging out of the DIYs. But this setup has a heavy hand in determining optimal listening distance. 16m triangle legs have been about my max working distance for this
Listening levels: I'd say depends on how much I like the song, and how much I like the wine 😀
90dB SPL flat to maybe 115. 105 is an exciting fun number for most guests IMO.
And really, 105dB at 16m is 139 at 1m. That's a heck of a lot harder for the mains than it looks if you want really clean sound. If I'm trying to show guests clean maximum impact, we move up to within at least 8 meters....
Processing: totally depends on mains decision IMO. If you go DIY, miniDsp is a great tuning platform, with both IIR and FIR capability. If you go store bought, just get a decent processing amp like ItechHD or qsc pld. If you don't go DIY, I'd pass on miniDsp due to its consumer output levels.
Anyway, best of luck, hopefully all my rambling added up to 2c !
Oh, PS....make sure to think thru nearby structure resonances..the labhorns rattled the ever loving poop out of the picnic shelter's roof at the soccer field..big design overlook...
JAG,
You are correct, flat 20 Hz response is lower than the horns I have worked with over the course of my career. Also understand that the music we worked with in the vinyl record era had little content below 40 Hz and the direct radiator response of massive quantities of FLH did go into the 20 Hz range, you could hear it on some synth lines.
A 10 block system using 20 Welter Systems (WS) L4 front loaded horns (FLH), each cabinet 45" x 45" x 32" in size would result in a bass array 15 foot tall (225 inches, 5.77 meters) by 12' 8" (128 inches, 3.28 meters) wide, 45 inches deep. Most outdoor shows using Southern Thunder Sound (STS) split the WS speakers stage right and left, (L/R) the bass horn array would be half that wide either side. L/R low frequency (LF) output along the center line of an outdoor venue sums as it would with a single center array, other than the directivity index (DI) of the larger bass horn being higher than the smaller low mid horn at the crossover frequency of 200 Hz.
An exception to my usual practice of L/R deployment occurred on 8/9/80 when STS was hired by Naked Zoo Enterprises (NZE), a competing St.Paul production company to provide an additional system located on a center "relay" (delay) scaffold located around 175 feet from stage behind the front of house (FOH) mixing location. The show was well attended, with a good bill featuring Charlie Daniels, Jerry Jeff Walker, and the Henry Paul Band at the Parade Stadium in St.Paul, Minnesota. We also provided NZE another large delay system at the University of Minnesota East Bank for the "River Flat Jam" with the Lamont Cranston Band, Head East, and Ozzie Ozborne/Randy Rhodes that summer.
NZE provided the scaffolding, as I recall we used 15) WS 1979 vintage fiberglass "Crunchers", a 45"x 45" x 30" horn with a separate 45" x 30" x 11.25" 2 x 15" compression chamber, set up 3 wide and 5 tall, mouth area of the bass horns almost 12 foot wide by over 20 feet tall on several scaffold decks. The bass horn stack was flanked L/R with vertical lines of low-mid, high-mid, & high horns, adding another five feet of frontal area.
The 1979 system had no rigging points, so was lifted up to over 30 foot high using scissors lifts, a scary ride when you shift hundreds of pounds of cabinets from the swaying lift to the stable scaffold. The later L4/H34/H38 cabinets all featured vertical and horizontal rigging, so could be flown either as vertical lines, or horizontal arced arrays, depending on coverage required by whatever venue the systems were deployed in.
Pictures of the STS/WS 1979 and other systems from around that era can be seen in the Pro Sound News "History of Concert Sound"
HistoryOfConcertSound.org
Post #5 has a description of the evolution of WS systems as of 2005, they have continued evolving and improving ( in most aspects) over the last 11 years.
The mono delay tower systems provided for NZE were dwarfed by the system we worked with the next year. Harry Witz of dB Sound out of Chicago hired us for support sound for the 9/5/81 REO Speedwagon, April Wine, Blackfoot "Triple Header" at the Brewer's Stadium in Milwaukee, Wisconsin. We arrived the day before to set up and sound check the integration of the systems, all pass bands erected in vertical line arrays.
No delay systems were used, Harry's sound design worked far better than any feasable implementation of delay towers.
My system, with other similar sub-hired equipment that filled a 24" straight truck was set up to cover the "cheap seats" on either side of the main scaffold towers used to "fly" dBs system and stack our systems which had no built in rigging hardware.
Between the Anicom, Eclipse, and WS equipment we brought to the stadium, and dB Sound's mains system, there were a total of 16 "blocks" of speakers and amplifiers.
Each "block" had around 4000 "real" watts of power (around 8000 peak) for the audience coverage, about 128,000 peak watts, above the "rule of thumb" of one watt per head typical of that era on large events.
128) 15" bass drivers on 45" deep horns covering 40 to 200 Hz
128) 12" or 15" low-mid drivers in 30" deep 3 way horn enclosures covering 200 to 1200 Hz
64) JBL 2482 hi-mid drivers exponential horn of nominal 35 x 60 degree dispersion which narrowed to approximately half that at the upper end of the1200 to 5kHz pass band, reducing interference associated with the vertical spacing
64) JBL 2420 high drivers on 90 x 40 degree radial exponential horns covering 5kHz to 16 kHz, also with progressively narrowing HF verticle response.
The vertical lines of each respective frequency reproducer were placed on platforms or flown from scaffold at least 60 feet high. My recollection standing on the top deck was we were looking up to the highest stadium seats at no more than a 10 degree angle- we did not need to angle any HF horns up for the nose-bleed seats, as it was within the coverage angle of the horns used, even allowing for the reduction of verticle coverage the line creates .
Climbing around the various scaffold decks during set up, sound check and show with ear plugs and ear muffs, my Radio Shack SPL meter never came out of being "pegged" at 126 dB, I'd estimate levels peaked around 140 dB "A" or C" scale in the immediate near field around the array. At the front of house mix riser located around 200 feet from the stage, halfway back in the stadium, SPL was swinging in the 120 dB "C" range, and not much below that on "A", as the band engineer's mixes were all rather "aggressive".
dB Sound was known to have the loudest systems on the road at the time, "outgunning" Clair S4 "hangs", or the various ShowCo systems by around 3-6 dB, largely because of the narrow dispersion horns dB used, and specifically on the stadium shows, the vertical array of the systems resulting in far more coherent sound at distance than the "checkerboard" patterns of Clair's front loaded boxes and ShowCo's aggregations of horns in short stacks stretching either side of stage like rows of firewood. ShowCo's cabinets regularly became firewood back in that era, seemed every year the components were housed in different boxes until their Prism system, which had vertical arrays and beam steering, and a really effective rigging system that was very simple to deploy compared to almost any before or after. Clair Bothers S4 hung from "Bumpers", a crude arc could be described by various adjustment of each pair of bumpers set of three chain motors.
Although both Harry Witz and I had deployed systems in vertical arrays on prior shows, his Brewer's Stadium system design was my first introduction to really long lines of bass horns, the "puny" 20 foot (6 meter) tall stacks I'd worked with just a year before were not even a wavelength of the F3. With a 60' tall line, the classic 3 dB rather than 6 dB per doubling of distance was impressive, I never had heard sound as consistent over a huge area before, walking at a brisk pace, we heard little difference in level or tonality from the crowd barricade to the furthest "cheap seats" in the upper balconies hundreds of yards from the system. "We" in this case refers to the many sound technicians, band mix engineers, and my brother Roy and I, who were free to wander wherever we pleased to report back any system adjustments needed to FOH.
dB Sound's Brewer's Stadium system was several orders of magnitude louder than Terry Hanley's system used to cover around 7 times the audience size at Woodstock 1969.
Harry Witz really was a good mentor, freely sharing information he had aggregated in his experience touring the largest venues in North America with his evolving speaker designs.
Ultimately, his sister company, R&R Cases, which made the best road cases in the business, as well as all dB's speaker systems, was contracted to build EV's Manifold Technology systems Harry started using the MT systems as they retired previous systems.
The dB Sound MT systems had a few notable changes from the "stock" versions- the HF were manifolded in a completely different fashion than the original Dave Gunness design, which suffered from terrible throat distortion and "air compression" at anything more than half power.
Although Dave Gunness and his associates came up with a pretty decent rigging system and excellent power density and efficiency in the MT systems, it should be noted he has never again attempted to use four HF drivers on a single tiny throat in any design since.
Some other representative STS production events exclusively using eight or more blocks of FLH cabinets include these shows:
8/12/83 We Fest- Sons Of The Pioneers, Freddy Fender, Tammy Wynette- Sioux Pass Ranch, Detroit Lakes, Minnesota
8/13/83 We Fest- Lynn Anderson, Bellamy Brothers, Alabama
8/14/83 We Fest- Tom T. Hall, Jerry Lee Lewis, Merle Haggard
8/25/83 Willie Nelson- Grandstand, Minnesota State Fair, St. Paul, MN
8/27/83 Kenny Loggins- Grandstand, State Fair
8/28/83 Statler Brothers- Grandstand, State Fair
8/29/83 Engelbert Humperdink- Grandstand
8/31/83 The Beach Boys- Grandstand, State Fair
9/1/83 Sammy Davis Jr.- Grandstand, State Fair
9/2/83 Oak Ridge Boys- Grandstand, State Fair
9/3/83 Kansas- Grandstand, State Fair
9/4/83 Manhattan Transfer- Grandstand, State Fair
6/20/87 Kansas City Super Picnic TV Show: Blackstone, George Burns, Gladys Night- Arrowhead Stadium, Kansas City Missouri.
Around 1986, WS started transitioning from horn load LF sections to a higher SPL output manifold bass reflex (MBR) design that reduced the L4 LF enclosure size by 33% while extending the F3 from around 50 Hz to below 40 Hz. dB Sound had seen the "writing on the wall" and had done the same several years before.
The EV Ad was from around 1990, both horn and MBR bass cabinets were used at the Grandstand, 6.35 mm Xmax was a "high performance" woofer in the late 1980s- we had to haul a lot more speakers around to achieve the SPL of current drivers, so we did.
Glad to not be lugging huge horns around.
Off to see the two members in Sha-Na-Na who still remain with the group from when I provided sound for them, and no, I was not at Woodstock 1969...
Art
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Hi mark100,
Post #708: "...make sure to think thru nearby structure resonances..the labhorns rattled the ever loving poop out of the picnic shelter's roof at the soccer field..big design overlook..."
Great post mark100, entropy455 has a big shop right in the line of fire-so to speak. While the layout is not fixed yet, this might be a very important consideration.
Oh, and thanks for trying to return some "sanity" to the SPL levels. Oh, well. 🙂
Regards,
Post #708: "...make sure to think thru nearby structure resonances..the labhorns rattled the ever loving poop out of the picnic shelter's roof at the soccer field..big design overlook..."
Great post mark100, entropy455 has a big shop right in the line of fire-so to speak. While the layout is not fixed yet, this might be a very important consideration.
Oh, and thanks for trying to return some "sanity" to the SPL levels. Oh, well. 🙂
Regards,
I liked this info.
I'm not trying to dispute the general intent of this statement, but I think you made an adding or typing error with the number I put in bold.
sound pressure level (SPL) decreases with doubling of distance by (−)6 dB (usually)
16m - 105dB
08m - 111dB (+6)
04m - 117db (+12)
02m - 123dB (+18)
01m - 129dB (+24)
Also: the usual 6dB rule assumes an ~omnidirectional source. With big horns, the on-axis output should fall off more slowly.
I'm not sure how much difference the directionality would make. If (purely a guess) the decrease was only 3dB per doubling of distance:
16m - 105dB
08m - 108dB (+3)
04m - 111db (+6)
02m - 114dB (+9)
01m - 117dB (+12)
...that's a big change - 139dB would need bulletproof drivers and kilowatt amps, but 117dB could be achieved with lightweight drivers and battery power.
This is all very fascinating. That's a genuine statement, don't read any sarcasm into that. There's a lot of info there and I'll have to read over it a couple more times to take it all in.
I do have some comments and questions.
1. All of your professional work has been involving HUGE audiences, in most cases the audience would be at least twice as wide as the stage and in some cases likely more than twice as wide as the stage. To cover an audience that wide absolutely requires at least dual separated subs (or at least a horizontal array), a single central mono sub would never work. With very wide audiences any comb filtering that occurs is a necessary evil in order to provide even spl coverage out to the "cheap seats".
How does this apply to OP's very small and narrow audience? He's outlined an audience area maybe 30 feet wide.
2. In your own words, the biggest horn stack you've ever worked with was 12 feet 8 inches wide (a 10 block system). And on most occasions you split that 10 block system in half and used bass horn stacks only 6 feet 4 inches wide. As per your previous post, it sounds like the mains (mids and highs) were integrated right into that stack, so essentially you had a maximum width of 6' 4" and the mains were essentially inside the sub giving a c - c distance between sub and mains of near zero on the horizontal plane. Even if the mains were beside the subs the c - c distance is remarkably low, 3 - 4 feet maybe, which allows for little or no comb filtering even with a high crossover point.
How does this relate to OP's proposed system that has a 20+ foot (horizontal length) sub (or dual subs) with a proposed main position at the side of the sub(s) giving a minimum 12+ foot c - c distance between the sub and mains?
3. In your description you have used many tools of the trade to form the beamwidths and wave patterns - horizontal arcs, various types of delay and/or beam steering arrays, vertical arrays (line array).
How does any of that relate to OP's project? With a single mono or dual stereo separated subs you can't use any of that, no arcs, no delay or beam steering, no line arrays.
4. If you like you can ignore everything except this one, it's the most important. Since nothing you have described yet is even remotely close to OP's proposed project, layout (audience size and area), equipment (huge number of subs used in various configurations vs OP's 1 or 2 massive horns), what are your recommendations for OP's project?
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Hi hollowboy,
Post #712: "...139dB would need bulletproof drivers and kilowatt amps..."
I've been messin' around w/ this for a while now, and looking @ the scope of this project I think using 4ea. (four) B&C 18SW115 would be on the cheap (?) side; well, here is what those 4 drivers will give you @ 1kW into each on a "full size" horn w/ a 10ft x 21.5ft mouth. Art's (weltersys) experiments indicate that these drivers will take peak of 3kW. The HP filter is set to keep the worst (sub 20Hz) excursion peak below Xmech, the rest is below Xmax, and the LP for an upper transition ~160Hz (all @ 1kW ea.).
If this is not enough I'd suggest to build two (I can't believe I'm typing this.) 🙂 Stereo, here we come.
Regards,
P.S.: Those curves are w/ resonances "NOT masked".
Post #712: "...139dB would need bulletproof drivers and kilowatt amps..."
I've been messin' around w/ this for a while now, and looking @ the scope of this project I think using 4ea. (four) B&C 18SW115 would be on the cheap (?) side; well, here is what those 4 drivers will give you @ 1kW into each on a "full size" horn w/ a 10ft x 21.5ft mouth. Art's (weltersys) experiments indicate that these drivers will take peak of 3kW. The HP filter is set to keep the worst (sub 20Hz) excursion peak below Xmech, the rest is below Xmax, and the LP for an upper transition ~160Hz (all @ 1kW ea.).
If this is not enough I'd suggest to build two (I can't believe I'm typing this.) 🙂 Stereo, here we come.
Regards,
P.S.: Those curves are w/ resonances "NOT masked".
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Hi 'just a guy',
Like I answered OP's question before, stereo basshorns, or shall I say basshorns for each side in order to create a point source for L&R. Whether they are configured as dual mono or stereo, I find less important but cannot see any objection for stereo. A 'gap' between the L&R basshorns of at least 1/2 wavelength of the Xover to prevent coupling between L&R at that frequency. For each side coupling between basshorn and low/mid-horn is desired for seamless transition but you seem to be aware of that already.
If you want to simulate the radiation pattern of a such a setup then perhaps 'Direct' isn't the ideal tool. The outcome of a 'tiny' 🙂 DSL218, a 1/4 WL basshorn with a smaller than ideal mouth, to represent a full sized 1/2 WL 'giant' basshorn doesn't seem look right. The outcome perhaps minimized to only a theoretical proof of the existence of 'lobing' but without any further detail specific conclusions. Of course, that is my opinion 🙂
Regards,
Djim
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I have no idea what you mean here. You don't want the basshorns to couple? Regardless, at 160 hz, 1/2 wave is 3.5 feet and at 80 hz it's 7 feet, and OP's proposed design is over 20 feet wide so there's no way to get them anywhere near within 1/2 wave of each other so comb filtering is guaranteed when the dual subs are mono or stereo.
I asked twice already (if not more) if anyone knew of a program like Direct that you could enter your own speaker data.
Regardless, the errors introduced by using the subs Direct allows will be directivity at higher frequencies compared to OP's large sub. Even so, the large sub has ~ enough beamwidth to make the Direct sim reasonably accurate in the area that OP has outlined as his small audience area.
Hi hollowboy, yes I meant 129dB...thx for the kind catch 🙂
For the mains, I do think a clean 129dB is harder than most folks think.
And yep, its easy enough to hit 129dB @ 1m....
But past around there, I've found distortion starts to creep up, and quickly.
A few weeks ago I measured THD using REW, and the measurements appear to confirm what my ears are telling me. By the time the DIY 60 (which is known as a pretty powerful box) gets into the low 130dB @ 1m range, THD is touching 10% at select frequency's. Overall, it averages considerably lower, and the biggest component is the 2nd harmonic....but still it's not as clean sounding as a few dB lower. (I should say I'm new to REW and want to double check accuracy, before posting more numbers... but I know what I hear..well, sometimes haha)
Do you think directivity slows down the 6dB loss per distance doubling for mains? I've been under the impression it doesn't....
Yea, I was guessing. Thinking again, I was probably guessing wrong 🙂
Doing some 'thinking out loud' below, it should be 6dB for any sort of source, horn or omni:
- a perfectly omni source (like a balloon popping) would give 6dB loss per distance doubled because the surface area of the spherical sound 'bubble' is quadrupled when radius doubles.
- for a source constrained to an arc (by a horn), only a fraction of the surface of the sphere is 'illuminated' by the horn ...but that 'illuminated' fraction would still quadruple as radius doubles.
By that logic, only linear / constrained sources, like stethoscopes and speaking tubes, would break the 6dB rule.
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Oliver,
The last time I saw "Live" was another good "war story", it was the first time I had seen of dozens of end-fire 2x18" subs set up either side and across the front of stage in a relatively small 12,000 seat arena, perhaps the worst sound I had heard and a decade, but very much fun running around with Wally, their tour manager as he tracked down the show electrician, who had to replace the 400 amp 120/208 3 phase fuses the sound system had blown "because a lighting guy plugged in (a 30 amp..) projector into the sound power instead of lighting".
The 60" tall rig I described in the last "war story", covering at least four times that audience, probably averaged no more than 200 amps 3 phase.
Art
Line arrays lose 3 db per doubling of distance in the nearfield at frequency where the array is sufficiently long. At subwoofer frequencies they would have to be very long.