DIY 18 driver column speaker (plans).
GRS 3FR-4 Full Range 3" Speaker Driver 4 Ohm , qty = 36 (available cheaply from parts express in bulk)
4x cabinets, MDF, interior dimensions 36"h x 9"w x 15"d, exterior dimensions 37.5"h x 10.5"w x 17.5"d
Each cabinet consists of 9 3" full range drivers, stacked in a vertical columb every 4 inches
1" dia x 5.25" length PVC bass reflex ports are installed on each cabinet to enhance bass response. The bass reflex ports are located exactly 3 inches left and 3 inches right of the centroid of each driver, 18 ports total per cabinet.
Left and Right speakers each consist of two towers (9 drivers each) stacked vertically. This modular construction greatly aids in construction, storage, and transport, since MDF panels generally come in 2' x 4' panels, a single continuous cabinet six feet long will be difficult to construct. When stacked on top of each other, each speaker will be 6'3" (75") tall. The top and bottom columns of 9 drivers each will be lined up exactly 4 inches apart, with the centermost speakers being 5.5" apart. This slight gap in the center caused by the insertion of 1.5" of mdf for the speaker walls. I believe this deviance is fairly small and should not impart any audible artifacts on the tonal output.
Most modern middle class residential dwellings have a cieling height of 8 feet, give or take an inch or so. The purpose of a sound column is to project a full soundstage at all heights from floor to ceiling, creating a linear rather than square rolloff, and reducing interactions caused by reflections with the floor and ceiling. The speaker currently stands 6'3" tall, just above the heads of most humans. Ideally the speaker columns can be positioned higher off the floor so that all comfortable sitting, standing, or reclining positions will be nearer to the centroid of the column. It isn't necessary to have an ideal soundstage at floor level because adults don't generally occupy this space, and as well furniture and other objects or clutter will disrupt the sound beam. As a result, ideally the column should be centered at about 4 feet above the floor, equidistant between floor and ceiling in a typical residential dwelling, and the tallest speaker will be place above the listeners' heads outdoors or in a larger venue.
So two boots are constructed to lift the speaker columns off the floor and provide bracing support. This bottom boot enclosure will have a design similar to the rest of the cabinet. These boot enclosures will have a wider base than the driver columns to help prevent tipping, but otherwise share the same depth and width dimensions.
2x boots, interior dimensions 9"h x 9"w x 15"d, external 10.5"h x 10.5"w x 17.5"d with bottom panel extending beyond the base of the tower for structural support. This will raise the seam between the bottom and top half column to exactly 4 feet above the floor, creating an ideal sound beam whether sitting, standing, or reclining. Total system height is now 7"3" (87"), yielding approximately 9" clearance below the ceiling in most residential installations.
The two boots would also make an ideal location for optional installation of two 8" diameter subwoofers (ported or sealed) to supplement the low range of the columns, thus reducing the need for EQ compensation.
Wiring of the drivers:
Each half tower contains 9x 4ohm drivers stacked vertically. These drivers will be sectioned off into three groups of three in a series/parallel network. The easiest way to wire them is as follows:
O-black terminal
|
-(S)+
| |
-(S)+
| |
-(S)+
_/
/
-(S)+
| |
-(S)+
| |
-(S)+
_/
/
-(S)+
| |
-(S)+
| |
-(S)+
|
O-red terminal
Each half column, when stacked, will have a characteristic impedance of 4 ohms. The red terminal of one half column is externally connected to the black terminal of the other half column, creating a series 4 ohm + 4 ohm = 8 ohm impedance. The remaining red and black terminal is connected to the amplifier, yielding balanced sound and a very high SLP level. If an 8" subwoofer (preferably 8-ohms, with appropriate passive crossover) is installed into the boot, it will be need to be bi-amped by connecting it to a separate channel or amplifier from the stereo pair. Bi-wiring or using the A/B selector on the amplifier is unlikely to yield much benefit as the columns will have a much higher sensitivity, as well as a linear rather than square rolloff as the listener gets further away. The bass loading effects of the room may help to mitigate this but the sub will likely need a higher signal level achievable only by biamping.
One important thing to consider is the towers will need to be braced to prevent from toppling over, especially in a house with pets or children are present, or carpeted floors. A simple way to do this would be to fasten a beam or panel to the edges of the speakers, immobilizing the tower.
I have my doubts if it is really this good, but I input the parameters for the GRS 3FR-4 full range driver into the vented box calculator (this requires metric conversion) and got an amazing low-end frequency response curve.
According to Parts Express:
Nominal diameter 3"
Re = 135Hz
Qms = 4.11
Qes = 1.11
Qts = 0.88
Vas = 0.03 ft^3 (.85L)
Desired volume in liters according to vented box calculator
mh-audio.nl - Vented System
resulted optimal volume = 8.66L (528 in^3). I increased this value slightly to 540 in^3 (4"h x 9"w x 15"d) for whole inch units which is convenient. Selecting 1" PVC piping as my port material, I opted for dual front facing ports (per driver) at a suggested length of 5.25". This results in a port tuned to 63.81Hz, and a whopping 41.86Hz rolloff, unbelievable bass extension for a 3" driver!!!
This contents of this emaculately tuned enclosure is to be stacked upon itself a total of 9 times per enclosure resulting in a vertical column speaker with highly impressive bass response. I am not aware of anyone attempting to build a ported vertical column, but keeping everything completely symmetrical and exactly replicating the ideal enclosure space, including 18 bass reflex ports per half column (36 per completed speaker) should creat a pretty damn fine sound stage. Why use a sophisticated equalizer to correct a sub-par sealed column when you can build a much better ported column that at most only needs a very modest bass/trebel boost, if at all?
Sadly my current finances and living arrangements make construction of this beautiful concept impossible. I bought a pack of four GRS 3FR-4 speakers recently, and was fairly impressed when I crammed them inside an inexpensive bird house. I was able to get great sound out of it on my amp using a +6 bass and +3 treble boost. I plan to construct a pair of 4"h x 9"w x 15"d ported enclosures for the two spare speakers and see if these values are really as impressive as the numbers suggest. If a single driver in this tuned enclosure sounds great, then 18-way ganging them on top of each other would be epic, much better than relying on active EQ to fix the driver's shortcomings.
Wish me luck.
BTW, if anyone wants to use my idea or even incorporate my exact suggested dimensions into their project, I would be honored. I am considering releasing this under CCv3 non-commercial. Attribution appreciated and please don't build my idea and claim it as your own or sell it for profit.
Thanks,
(C) 2017 Alfred J Williams
GRS 3FR-4 Full Range 3" Speaker Driver 4 Ohm , qty = 36 (available cheaply from parts express in bulk)
4x cabinets, MDF, interior dimensions 36"h x 9"w x 15"d, exterior dimensions 37.5"h x 10.5"w x 17.5"d
Each cabinet consists of 9 3" full range drivers, stacked in a vertical columb every 4 inches
1" dia x 5.25" length PVC bass reflex ports are installed on each cabinet to enhance bass response. The bass reflex ports are located exactly 3 inches left and 3 inches right of the centroid of each driver, 18 ports total per cabinet.
Left and Right speakers each consist of two towers (9 drivers each) stacked vertically. This modular construction greatly aids in construction, storage, and transport, since MDF panels generally come in 2' x 4' panels, a single continuous cabinet six feet long will be difficult to construct. When stacked on top of each other, each speaker will be 6'3" (75") tall. The top and bottom columns of 9 drivers each will be lined up exactly 4 inches apart, with the centermost speakers being 5.5" apart. This slight gap in the center caused by the insertion of 1.5" of mdf for the speaker walls. I believe this deviance is fairly small and should not impart any audible artifacts on the tonal output.
Most modern middle class residential dwellings have a cieling height of 8 feet, give or take an inch or so. The purpose of a sound column is to project a full soundstage at all heights from floor to ceiling, creating a linear rather than square rolloff, and reducing interactions caused by reflections with the floor and ceiling. The speaker currently stands 6'3" tall, just above the heads of most humans. Ideally the speaker columns can be positioned higher off the floor so that all comfortable sitting, standing, or reclining positions will be nearer to the centroid of the column. It isn't necessary to have an ideal soundstage at floor level because adults don't generally occupy this space, and as well furniture and other objects or clutter will disrupt the sound beam. As a result, ideally the column should be centered at about 4 feet above the floor, equidistant between floor and ceiling in a typical residential dwelling, and the tallest speaker will be place above the listeners' heads outdoors or in a larger venue.
So two boots are constructed to lift the speaker columns off the floor and provide bracing support. This bottom boot enclosure will have a design similar to the rest of the cabinet. These boot enclosures will have a wider base than the driver columns to help prevent tipping, but otherwise share the same depth and width dimensions.
2x boots, interior dimensions 9"h x 9"w x 15"d, external 10.5"h x 10.5"w x 17.5"d with bottom panel extending beyond the base of the tower for structural support. This will raise the seam between the bottom and top half column to exactly 4 feet above the floor, creating an ideal sound beam whether sitting, standing, or reclining. Total system height is now 7"3" (87"), yielding approximately 9" clearance below the ceiling in most residential installations.
The two boots would also make an ideal location for optional installation of two 8" diameter subwoofers (ported or sealed) to supplement the low range of the columns, thus reducing the need for EQ compensation.
Wiring of the drivers:
Each half tower contains 9x 4ohm drivers stacked vertically. These drivers will be sectioned off into three groups of three in a series/parallel network. The easiest way to wire them is as follows:
O-black terminal
|
-(S)+
| |
-(S)+
| |
-(S)+
_/
/
-(S)+
| |
-(S)+
| |
-(S)+
_/
/
-(S)+
| |
-(S)+
| |
-(S)+
|
O-red terminal
Each half column, when stacked, will have a characteristic impedance of 4 ohms. The red terminal of one half column is externally connected to the black terminal of the other half column, creating a series 4 ohm + 4 ohm = 8 ohm impedance. The remaining red and black terminal is connected to the amplifier, yielding balanced sound and a very high SLP level. If an 8" subwoofer (preferably 8-ohms, with appropriate passive crossover) is installed into the boot, it will be need to be bi-amped by connecting it to a separate channel or amplifier from the stereo pair. Bi-wiring or using the A/B selector on the amplifier is unlikely to yield much benefit as the columns will have a much higher sensitivity, as well as a linear rather than square rolloff as the listener gets further away. The bass loading effects of the room may help to mitigate this but the sub will likely need a higher signal level achievable only by biamping.
One important thing to consider is the towers will need to be braced to prevent from toppling over, especially in a house with pets or children are present, or carpeted floors. A simple way to do this would be to fasten a beam or panel to the edges of the speakers, immobilizing the tower.
I have my doubts if it is really this good, but I input the parameters for the GRS 3FR-4 full range driver into the vented box calculator (this requires metric conversion) and got an amazing low-end frequency response curve.
According to Parts Express:
Nominal diameter 3"
Re = 135Hz
Qms = 4.11
Qes = 1.11
Qts = 0.88
Vas = 0.03 ft^3 (.85L)
Desired volume in liters according to vented box calculator
mh-audio.nl - Vented System
resulted optimal volume = 8.66L (528 in^3). I increased this value slightly to 540 in^3 (4"h x 9"w x 15"d) for whole inch units which is convenient. Selecting 1" PVC piping as my port material, I opted for dual front facing ports (per driver) at a suggested length of 5.25". This results in a port tuned to 63.81Hz, and a whopping 41.86Hz rolloff, unbelievable bass extension for a 3" driver!!!
This contents of this emaculately tuned enclosure is to be stacked upon itself a total of 9 times per enclosure resulting in a vertical column speaker with highly impressive bass response. I am not aware of anyone attempting to build a ported vertical column, but keeping everything completely symmetrical and exactly replicating the ideal enclosure space, including 18 bass reflex ports per half column (36 per completed speaker) should creat a pretty damn fine sound stage. Why use a sophisticated equalizer to correct a sub-par sealed column when you can build a much better ported column that at most only needs a very modest bass/trebel boost, if at all?
Sadly my current finances and living arrangements make construction of this beautiful concept impossible. I bought a pack of four GRS 3FR-4 speakers recently, and was fairly impressed when I crammed them inside an inexpensive bird house. I was able to get great sound out of it on my amp using a +6 bass and +3 treble boost. I plan to construct a pair of 4"h x 9"w x 15"d ported enclosures for the two spare speakers and see if these values are really as impressive as the numbers suggest. If a single driver in this tuned enclosure sounds great, then 18-way ganging them on top of each other would be epic, much better than relying on active EQ to fix the driver's shortcomings.
Wish me luck.
BTW, if anyone wants to use my idea or even incorporate my exact suggested dimensions into their project, I would be honored. I am considering releasing this under CCv3 non-commercial. Attribution appreciated and please don't build my idea and claim it as your own or sell it for profit.
Thanks,
(C) 2017 Alfred J Williams
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When you input TS parameters from a high Qts speakers in a vented box calculator (software), result always is a big box with impressively low extension, and unfortunately, with very bad sound quality of the bass. Qts=0.88 is too big for a vented box design. Try with closed box and active EQ. Or, if you insist, try with vented box volume of about 2 liters per driver.
You might be right. Honestly based on the specs, 42Hz sounds more than a bit too good to be true. My Polk Monitor 40 Series II are phenomenal sound with their dual 5.25 woofers and dip down to around 50Hz according to the specs. That a 3" driver could do better than that is a pretty tall order, without building an enormous wave guide or something.
This speaker recommended .088 cubic feet or thereabouts for a sealed enclosure. My bird houses are about half that volume, approximately .043 IIRC, but it's hard to mess up a sealed box. Too small and you limit the bass extension, too large and you risk over-excursion. A sealed enclosure at .088 cubic feet per driver would place the column at about a six inch square prism internally, and a lot simpler to build and lightweight. That would yield a better bass response than my undersized bird houses but still require tweaks of the bass and treble knobs on the amp.
Cutting box enclosures is a PITA with a circular saw but can be done by carefully marking your cuts and clamping down, using scrap lumber as a rip guide. I was serious about building at the very least two 4"x9"x15" ported enclosures for the drivers to see how it performed in it. If it's as bad as you say, I probably saved a few bucks worth of MDF, a few hours of sweat, and disappointment.
I guess you could say I got to reading this thread and was inspired by the amount of dedication one man put into his project:
http://www.diyaudio.com/forums/full...o-towers-25-driver-full-range-line-array.html
And yeah, always built a one-high prototype first to make sure it sounds good before you stack em sky high...
Hi Alfred
Just wondering if you have considered using sections of plastic pipe sandwiched between a baffle and a back plate. If you use an up-cut trenching bit on your router, you could easily cut he grooves into which the pipe sections would fit.
Doug
Just wondering if you have considered using sections of plastic pipe sandwiched between a baffle and a back plate. If you use an up-cut trenching bit on your router, you could easily cut he grooves into which the pipe sections would fit.
Doug
I'd probably use a 1 1/8" spade bit with a hand drill. It's what I used on my arcade style game controllers, and should fit the 1 inch PVC pipe. Or 1 1/4", not absolutely sure if the wall thickness was 1/16 or 1/8. Obviously test the bit on scrap first. Any splintering can be sanded and filled when fitting the pipe. And MDF tends to splinter a lot less than plywood. If you place a scrap panel underneath the work piece, both sides come out super clean.
The 3" cylindrical hole saw was murder on my wrist when I did the birdhouses, but came out clean in the end. I can't really imagine doing 36 3" diameter holes in this manner without a drill press. Like I said, I don't have the fianances or living space atm, but I may build a one-high enclosure to test the acoustical properties. Sonce said don't trust the numbers for small drivers, as 42Hz does sound a bit too good to be true for a single 3" driver. If the single ported enclosure sound like garbage, a sealed enclosure would still work then. 6"x6"x4" (per driver) in a long tube would also work and be a lot less total mass than the ported plans. I think bass would roll off around 130Hz, necessitating a bass boost and/or active sub for full low end response.
With double the drivers and ports, especially if the single enclosure was perfectly symmetrical, the sound pressure on either side of the imaginary wall would be exactly the same. So removing this wall would likely have a negligible effect for two or more units, then the enclosures could (in theory) be stacked sky high.
Box rigidity could come into play at extreme dimensions though, so internal bracing is not a bad idea.
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A couple of points for you to consider.
Put the drivers as close together as you can, it is the centre to centre distance between drivers that dictates where the comb filtering from the combined drivers will occur. By mounting the drivers frame to frame you make this as high as possible.
Vented enclosures are very tricky to get right and often need the tuning adjusted by port length, that is going to be a pain for you as you have so many.
Slot ports built into the side of the cabinet would be easier to construct and to tune.
Also a vented cabinet can't have as much stuffing inside to tame the cabinet resonances. Your design as a very long pipe with no stuffing will have some pretty bad pipe resonances. By breaking up the cabinet internally into separate sections you limit the resonances somewhat and get extra bracing.
The small 8 inch sub driver is going to be the limiting factor as the line will likely have much more output potential than it.
Put the drivers as close together as you can, it is the centre to centre distance between drivers that dictates where the comb filtering from the combined drivers will occur. By mounting the drivers frame to frame you make this as high as possible.
Vented enclosures are very tricky to get right and often need the tuning adjusted by port length, that is going to be a pain for you as you have so many.
Slot ports built into the side of the cabinet would be easier to construct and to tune.
Also a vented cabinet can't have as much stuffing inside to tame the cabinet resonances. Your design as a very long pipe with no stuffing will have some pretty bad pipe resonances. By breaking up the cabinet internally into separate sections you limit the resonances somewhat and get extra bracing.
The small 8 inch sub driver is going to be the limiting factor as the line will likely have much more output potential than it.
Thanks. The 3" drivers could probably be pushed down to 3.5" distance minimum, but I plan on back mounting the drivers and routing out the space for the mounting plate to 1/4" thickness. This may weaken the structural integrity of the MDF front panel considerably, seeing as there would be a 1/2"x1/4" bridge between every hole across the length of the front panel. That could break very easily
At my current 4", equates to a full wave around 3350Hz or so.Referring to figure 7 of the following document,
http://www.audioroundtable.com/misc/nflawp.pdf
maximum SPL is achieved between .5 to 1 wavelength, showing a rapid SPL deterioration beyond 2 wavelengths, where comb effects begin to dominate. This would start to cause problems above 6700Hz. If I went with 3.5" spacing, this would get me up to 3825Hz full wave (double wavelength at 7650Hz), so comb filtering effect will start to dominate between upper 6000s to upper 7000s regardless what I do.
The PDF I referenced seemed convinced that a two way line array speaker with ribbon tweaters spaced a minimum of 80% coverage was the way to go, but this creates other problems, one of which is much higher cost. Another issue is the author's ribbon tweeter array is shorter than the woofer array, which may result in a higher SPL in the beam area for the tweets but with lesser coverage as well. The wider coverage for the woofers might cause an imbalanced sound in the crossover region as well, and the crossover frequency has to be at minimum wavelength to the distance between the woofers as well as the distance between the woofer line and the tweeter line.
Wesayso used this driver in his gorgeous 25 high full range custom build, and he seemed to have no issues. The IDS25 also uses a 3.5" driver. 25 x 3.5" = 87.5", just shy of the 8 feet (96") standard ceiling height of most residential domiciles in North America. Stacked at 3.5", they would have started "combing" around 7650Hz.
I stand by my opinion that 3.5" spacing in MDF with a 3" hole saw would be structurally unsound, so I'm going with 4" to be safe. My design with 4" spacing produces a 6 foot column with 18 drivers which is to be be centered between floor and ceiling.
I think you are right. The more and more I think about it, doing a sealed enclosure might be safer.
The drivers could make a neat 6"x6"x72" column internal (7.5"x7.5"x73.5" external) at 4" spacing. I'll need to do at least one load-bearing structural break in the column unless I buy 8'x4' MDF panels, which would be difficult to transport home. Placing thin, non-load-bearing 6"x6" squares of 1/4" MDF internally between every three drivers might be an option if it reverberates, but I imagine it would be difficult for the structure to resonate if SPL are uniform across the entire length. Also with such a thin and long structure, it may become necessary to bolt together at the seams somehow as wood glue may not be enough. Should I use screws or dowels? Possibly dowels in the front and side panels, with screws for a removable back panel, should I ever need to open or service it.
The six foot cubic prism might look nice mounted on a short pole connected to a square base so that the column will have optimal room height.
I'm not using these as PA speakers or indoor/outdoor venues so I doubt I'd ever pump a full 180w of power into these babies. They will have more than enough loud for comfortable listening in any living space.
That said, the sub thingy probably isn't going to happen. I imagine an active sub and/or bass/treble tweaks will be all that's needed to get great sound.
Thanks. The 3" drivers could probably be pushed down to 3.5" distance minimum, but I plan on back mounting the drivers and routing out the space for the mounting plate to 1/4" thickness. This may weaken the structural integrity of the MDF front panel considerably, seeing as there would be a 1/2"x1/4" bridge between every hole across the length of the front panel. That could break very easily
I don't know if you have seen my thread where I am building a 25 driver sealed array using TC9 drivers in mdf?
http://www.diyaudio.com/forums/full-range/303417-full-range-tc9-line-array-cnc-cabinet.html
I have used 77mm through holes in 16mm MDF with the drivers mounted basket to basket the frame is recessed into the front by 3.5mm and the backs of the holes have a roundover. There is no issue with structural stability but you do need to be careful about moving the front panels as they are long and thin with lots of holes in. Hold them on their side to move them or leave them flat.
I don't see a problem with making them closer as your baffle would basically be the opposite of mine. The full thickness on the edges really helps to maintain the panel strength horizontally.
Up to you but I don't want to give away anything if I don't have to.
I know them well they also heavily inspired my build.
I think so which is why I did!
It seems the general consensus from Pros is to go sealed and EQ the entire column to flatline the response curve of the drivers.
In my experience, you can really make a quality full range driver sing by enhancing the traditional 100Hz bass and 10kHz treble knobs. I seem to really enjoy the warmth of sound from a full range with the bass at 4 o'clock and treble at 2 o'clock position. Of course this isn't HiFi, and a well designed 2-way or 3-way HiFi speaker with good bass extension sounds best with a perfectly flat EQ.
I have read that passive radiators behave similarly to a port, but IDK if that's accurate since a passive radiator still creates a sealed enclosure. Like a tuned port, the rear of a speaker creates SPL in the enclosure, then this sound pressure escapes, either by equalizing the pressure through a port, or by moving a diaphram. Since pressure has to build inside the resonate chamber before the diaphram or port releases it, the SPL signal lags behind that of the back cone, reinforcing the front cone SPL. One potential benefit over ported enclosures is the passive radiator will still resist excursions well below it's resonant frequency, acting more like a sealed enclosure at very low frequencies, preventing the drivers from reaching their excursion limits.
How does this tie into the line array? A passive woofer could translate this back pressure into sound, enhancing the low end response of the full range. A single 5.25 inch passive radiator has similar surface area to three 3 inch drivers, and likewise a single 6.5 inch passive radiator has a similar surface area to four 3 inch drivers (and an 8 inch is roughly equal to seven drivers), with the benefit of deeper resonant frequency, which is desirable for increasing the low end response.
Assuming the array is perforated internally, they radiators could be positioned on the side or rear, each radiator unit being yolked to several driver units. If a suitable passive radiator cannot be found at the given size, then cheap woofers could be used and left disconnected. It would raise cost though, and may be a waste of good drivers that could otherwise be crossed over and used to accentuate the low end response.
In my experience, you can really make a quality full range driver sing by enhancing the traditional 100Hz bass and 10kHz treble knobs. I seem to really enjoy the warmth of sound from a full range with the bass at 4 o'clock and treble at 2 o'clock position. Of course this isn't HiFi, and a well designed 2-way or 3-way HiFi speaker with good bass extension sounds best with a perfectly flat EQ.
I have read that passive radiators behave similarly to a port, but IDK if that's accurate since a passive radiator still creates a sealed enclosure. Like a tuned port, the rear of a speaker creates SPL in the enclosure, then this sound pressure escapes, either by equalizing the pressure through a port, or by moving a diaphram. Since pressure has to build inside the resonate chamber before the diaphram or port releases it, the SPL signal lags behind that of the back cone, reinforcing the front cone SPL. One potential benefit over ported enclosures is the passive radiator will still resist excursions well below it's resonant frequency, acting more like a sealed enclosure at very low frequencies, preventing the drivers from reaching their excursion limits.
How does this tie into the line array? A passive woofer could translate this back pressure into sound, enhancing the low end response of the full range. A single 5.25 inch passive radiator has similar surface area to three 3 inch drivers, and likewise a single 6.5 inch passive radiator has a similar surface area to four 3 inch drivers (and an 8 inch is roughly equal to seven drivers), with the benefit of deeper resonant frequency, which is desirable for increasing the low end response.
Assuming the array is perforated internally, they radiators could be positioned on the side or rear, each radiator unit being yolked to several driver units. If a suitable passive radiator cannot be found at the given size, then cheap woofers could be used and left disconnected. It would raise cost though, and may be a waste of good drivers that could otherwise be crossed over and used to accentuate the low end response.
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