Great to read about your new stuff going on Art, hope you will have success and fun while building and testing new ways to implement your new subs!
I've strictly been deejaying the last 5-6 years with my gear(no live music) and this talk about cardioid and end fire arrays are very interesting indeed, but these techniques seem to favor live music rather than CD Dj gigs. Personally I really like to have my stomach rattle while behind the decks and I dislike playing with poor bass at the decks and bad monitoring over all..
I wonder what would be the best way to implement 4-6 cabinets to reduce vertical dispersion, while maintaining even coverage and good horizontal dispersion in front of the cabs while have a strong bass aiming back at the DJ? I was thinking a straight horizontal cluster center stacked with delay on the 1 or 2 outer pairs, but I've been looking at Dave Rat videos on YouTube and while he claim this seem favorable with a sine wave his impression is you loose transient response and it sounds bad with dynamic music material.
I've strictly been deejaying the last 5-6 years with my gear(no live music) and this talk about cardioid and end fire arrays are very interesting indeed, but these techniques seem to favor live music rather than CD Dj gigs. Personally I really like to have my stomach rattle while behind the decks and I dislike playing with poor bass at the decks and bad monitoring over all..
I wonder what would be the best way to implement 4-6 cabinets to reduce vertical dispersion, while maintaining even coverage and good horizontal dispersion in front of the cabs while have a strong bass aiming back at the DJ? I was thinking a straight horizontal cluster center stacked with delay on the 1 or 2 outer pairs, but I've been looking at Dave Rat videos on YouTube and while he claim this seem favorable with a sine wave his impression is you loose transient response and it sounds bad with dynamic music material.
When you are doing a directional array with two rows of subs, you have two options for implementation.
Option one is to have the rear subs fire first, then the front. The result is the wavefronts are perfectly in time for the audience and the signal is preserved in its entirety. The drawback is that on stage you get hit by the rear subwoofers first and then after a small delay the antiphase of the front row. Imperfect but significant cancellation is achieved.
Option two is the opposite. The front row of subs fire first, followed by the rear row. This means that the audience hears the front subs first, followed by the rear subs in phase. This results in the smearing of transients and muddying that you describe. For making this sacrifice, you gain much more perfect cancellation to the rear. The wavefront from the front subs is rejected very strongly when it reaches the rear subs. Stage volume is drastically reduced.
Hi and thanks for the explanation, Dave Rat also gave a very good representation of the technique and end fire arrays seem cool!. What I'm after is not that much cancellation behind but a focused punch at the DJ desk while maintaining a good horizontal dispersion on the front of the subs facing the audience. CD's are OK with some brute force bass without issues and I need to feel quite a lot of sub when mixing to get a good freling of what im doing.
Another way would be to get really strong Dj monitors with an end fire array configuration but if it's achievable I could get away with >100 hz in the DJ monitors and get the sub from the sub stack, just time delay the monitors to play well with the sub stack if it makes sense?
I can't believe I missed that. I must finally be maturing somehow.Looking forward to the Keystone Blow
Isobaric loading does not increase excursion, so you pay for a pair of drivers to get the output of one. No potential there, for my cheap ***
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A vertical array would reduce vertical dispersion, while maintaining even horizontal coverage in front (or behind).
Stacking the 45" dimension vertically would result in about 2.5 dB more rear radiation than a horizontal stack, but definitely use a large plinth and ratchet strap the stack to it if you go 6 cabinet high-that would be a 22.5 foot (6.92 meter) tall stack!
A stack that tall would have vertical pattern control to well below the Keystone's LF cutoff.
Art
Looking forward to the Keystone Blow
, visions of a "Glory Hole" "come" to mind, forgot the effing hyphen in the Keystone B-Low Sub™ (or C-Low) name .I gotta get out to the shop...
Art
I gotta get out to the shop...
Art
Art, any hint at what driver you'll be using for the stretch KS?, will the BC18SW115 work ok? ... I'm jumping the gun here sorry
For a mere $100 I'd recommend you pick up the DATS V2
Dayton Audio DATS V2 Computer Based Audio Component Test System
cheers
Martin
Martin,
I'll be using a pair of B&C 18TWB100-4, and using four Dayton PA385S-8 that I have in (too small)2x15" PPSL BR cabinets. They will be eventually be replaced by more 18TWB100 when I can afford it, and hopefully won't make the mistake of buying cheap again
.The BC18SW115 work great, but require a bit more power to go a bit louder, and are more expensive than the more sensitive 18TWB100. Since I have no gigs on the books yet after my recent move to Florida, have to keep track of the $$.
Art
Art, will the upper response of your extended keystones be affected in any negative way due to the lower corner? I like to be able to cross my keystones above 100 which works fine with the originals.
Also regarding the nature of the end fire array you mentioned occupying quite a bit of space, would it be OK to position it underneath a rather tall stage or is in front of it more preferred? Would the array need to be spaced from the wall behind it for the positive effect to be valid? I understood they need a rather big room to work properly
Also regarding the nature of the end fire array you mentioned occupying quite a bit of space, would it be OK to position it underneath a rather tall stage or is in front of it more preferred? Would the array need to be spaced from the wall behind it for the positive effect to be valid? I understood they need a rather big room to work properly
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Osse,
1) I have not simulated the additional path length and volume changes yet, but would anticipate the upper response dip will come down about the same % as the low corner, less than 1/3 octave.
2) 100 Hz is where I generally cross also. If the upper response is adversely affected too close to that frequency, I'll change the Keystone exit accordingly to correct. The cabinets loaded with 15" rather than 18" will definitely need some exit adjustment for proper loading.
3) End fire (or "tunnel") arrays have been employed over and/or under stage on major tours, the reports have been good, though I have not heard (or experimented) with any of those configurations so far.
4) The reason for using end fire or cardioid arrays is too reduce rear radiation. If the array is near the wall, the wall is already a boundary, and more effective at cutting down rear radiation than electronic methods.
End fire or cardioid arrays are not as loud in the forward direction as a flat-front stack, they simply (well, it's complicated..) create a destructive interference pattern in some direction other than forward. By manipulating physical spacing, polarity, and delay, different patterns can be created. In the real world, because of diffraction and reflection effects as the waves wrap around and bounce off cabinets, the results are seldom as "clean" as the simulations would suggest.
That said, an end-fire "V" with Keystones would be much more "horn like" than the usual end fire "domino row" often seen. I anticipate an end-fire "V" with Keystones may actually be a bit louder than a flat-front stack due to additional horn gain. I sold the original pair of Keystones a few years ago, so won't know anything for sure until the new cabinets and the tests are done.
Since you already have multiple Keystones, you could experiment and report the results, I'm sure there are lots of readers that would be interested!
Art
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Would you lay the keystones down and place them in pairs at 90° angle for the v-array you mention? Would this also increase horizontal dispersion
Actually I only have two for the moment(8 ohm drivers), but I have an amp that can push two more so I'm tempted on two more some time in the future and try the end fire configuration
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Bjones,
I'll give it a try.
The Keystone, and most any tapped "horn", has an expanding cross section that starts with a small throat area and expands in to a large mouth area. That expansion can be called the "flare rate".
To (properly) extend a horn, the flare rate should be continued, or expanded, upon, as in a hyp-ex (Hyperbolic mouth on an Exponetial) horn. None of the examples of horn extensions you drew look anything like a smooth expansion. That does not mean they won't "work", but they probably won't work very well in terms of frequency response, especially in the critical upper range of the pass-band, "where the action is".
As can be seen in the photograph of the wave-guides used on the Keystone-Paraline array, they have a smooth, 90 degree expansion from the cabinet front dimensions, resulting in increased output with no frequency response deviations, in fact smoothing the response slightly. The wave-guide is not actually a horn extension, it does not lower the low corner of the frequency response, but does provide an average of 3 dB gain over the pass band from 36 Hz to 100 Hz, with even more gain above 100 Hz. Because the wave-guide imparts an upward sloping response, even when equalized flat there is considerably more "punch" available than without. Although the extra bother of assembling the wave guides may not be worth the rewards for a one-night gig, I always used them for multiple-day events if there was room for them.
Using the wave-guides is like more than doubling power, with no power compression. When you need all the headroom you can get, they make a big difference.
Art
I would be more inclined to place them upright to take advantage of the additional forward gain the vertical array would have compared to a horizontal placement. That said, a horizontal array with a "V" wave-guide above could be awesome. One could experiment with the angle, although 45° would certainly work, it may not be the optimum for forward gain, or smoothest frequency response.Would you lay the keystones down and place them in pairs at 45° angle for the v-array you mention?
Actually I only have two for the moment(8 ohm drivers), but I have an amp that can push two more so I'm tempted on two more some time in the future and try the end fire configuration
The physical distance between the Keystone acoustical centers will be different in either horizontal or vertical arrays, and the "V" angle will also affect distance from front to rear, so different delay times will be required. The addition of wave-guides will also affect optimum delay time for rear cancellation due to the longer rear path length to go over the guide.
Lots of moving parts, Osse!
Art
Good morning Art,
Becuase I have only a day or so left to complete the wave guides, hopefully you can give me "just enough" and I can delve deeper when I return.
Fig A - Because you know the exact subwoofer I am using, rather than tell me how to get to the proper dimensions, could you provide either confirmation that the ones I have will work, or ones that will. Based on Fig A - each side is 24" wide with a 90 degree horizontal (I planned on using 1/2" for this)
Fig B - poorly drawn perspective
Fig C- I really don't know how combing works on low frequency and realize that these guides overlap -
Fig D top down view with the subs angled as I would if using multiple narrow dispersion mains
Fig E - I feel like this stack is what you were saying would be ideal - i could match all the horizontals up however, I think it will be taller than the structure its going to have over it - also there are other camps close and the goal isn't to project the sound as far as possible with even spl coverage, but more create as much sound in a 100' x 50' area - in this case having bodies absorb the sound is a plus which is why I was keeping the stack under 9 feet with subs side by side
If I am way off - maybe just a "90's to wide use 60 degrees and they need to be at least 30" I know this is over simplification
Becuase I have only a day or so left to complete the wave guides, hopefully you can give me "just enough" and I can delve deeper when I return.
Fig A - Because you know the exact subwoofer I am using, rather than tell me how to get to the proper dimensions, could you provide either confirmation that the ones I have will work, or ones that will. Based on Fig A - each side is 24" wide with a 90 degree horizontal (I planned on using 1/2" for this)
Fig B - poorly drawn perspective
Fig C- I really don't know how combing works on low frequency and realize that these guides overlap -
Fig D top down view with the subs angled as I would if using multiple narrow dispersion mains
Fig E - I feel like this stack is what you were saying would be ideal - i could match all the horizontals up however, I think it will be taller than the structure its going to have over it - also there are other camps close and the goal isn't to project the sound as far as possible with even spl coverage, but more create as much sound in a 100' x 50' area - in this case having bodies absorb the sound is a plus which is why I was keeping the stack under 9 feet with subs side by side
If I am way off - maybe just a "90's to wide use 60 degrees and they need to be at least 30" I know this is over simplification
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Mr. Jones,
1) The wave guides I was using were 90 degrees because the top cabinet horns were 26.5" wide, and 90 degrees.
Functionally, at low frequencies, whether the "wings" or "barn doors" are parallel or angled to the cabinet makes little difference, the larger boundary area is what increases forward directivity, and therefore gain- the 3 to 6 dB that would wrap around behind the cabinet goes forward, just like if the cabinets were mounted in a wall. There is no reason for you to make wave guides, you could simply use pipe clamps on the top and bottom of plywood.
2) I don't recall the exact sub woofer you are using, but barn doors or wave-guides will work with any cabinet design equally well.
3) The vertical stack is optimum for not wasting your sub SPL on birds and gyrocopter pilots. If it is too tall for the venue, try something along the sketch below. Bodies absorb very little <100 Hz output, unless they are actually pressed up against the Keystone exit, in which case, pry them away.
4) It is so simple you have missed the point. Make the boundary as big as you can afford to, and you will get more gain, to a lower frequency, topping out at a theoretical maximum of +6dB.
Stand the plywood up, screw it to the cabinet front, done deal, Day-Glo paint is optional.
My tests indicated a +3 dB at 36 Hz to +6 dB around 160 Hz with only doubling frontal area. A +6 dB gain down to to 36 Hz (or as low as any sub can go) requires an infinite boundary ( a 100 mile long and deep cliff), so there is obviously a point of diminishing returns, there really would be no reason to go wider than the lowest wavelength reproduced even if you could afford to lug and erect that much plywood.
Don't cut off any more skin!
Cheers,
Art
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Art, I can't thank you enough. Talk about missing the forest.
Last question for now than is - 1/2" ply with some 2x4 beams ran across the back is my plan.
Obviously, flex is bad. How bad? I want that rear sound wave to reflect and not absorb and I know the second that ply flexes its absorbing.
Since there are no other "walls" to create pressure it cant hit with too much force, but I imagine constant vibration.
I want to avoid time/cost/energy to have something end up soaking up sound energy - so if I need to spend/do a little more to reinforce the crap out of it let me know. Otherwise Im thinking 2 8' studs on edge ran across the back and screwed in to prevent excessive flex.
Last question for now than is - 1/2" ply with some 2x4 beams ran across the back is my plan.
Obviously, flex is bad. How bad? I want that rear sound wave to reflect and not absorb and I know the second that ply flexes its absorbing.
Since there are no other "walls" to create pressure it cant hit with too much force, but I imagine constant vibration.
I want to avoid time/cost/energy to have something end up soaking up sound energy - so if I need to spend/do a little more to reinforce the crap out of it let me know. Otherwise Im thinking 2 8' studs on edge ran across the back and screwed in to prevent excessive flex.
