Go with a tapped horn design and this will be the result, except that the driver will be in the mouth of the "horn" so it will be completely protected if a grille is added to the mouth.
That is what i also would do, and this is a design that could work for you that is tested and designed here: https://www.diyaudio.com/community/threads/th-18-flat-to-35hz-xoc1s-design.190635/
A single XOC1 TH18 using the B&C 18SW115-4 could achieve more SPL than the pair of the OP's Mackie subs, but would hardly go any deeper, it's response rolls off ~24dB per octave below 40Hz:
If the octave below 40Hz is desired, a TH like Josh Ricci's Gjallerhorn would be a more useful choice.
That said, for output density (cabinets per truck space) ported cabinets still have an output advantage in the 20Hz range, as can be seen in Josh's comparative measurements in post #7.
Void Nexus X is basically what you are after (or similar). A shitload of voice coil area and motor.
I designed a similar 4x12" version not long ago, but did not proceed with the project.
I designed a similar 4x12" version not long ago, but did not proceed with the project.
Smitske wrote he didn't proceed with his similar design.
The OP's Mackie SR18S has a usable (-3dB) bandwidth from 35 Hz – 160 Hz.
The louder 8x12" Void Nexus X has less usable (-3dB) bandwidth, from 36 Hz to 100 Hz.
It uses neodymium magnet 1000 watt (AES) 12" drivers with cast aluminum frame, 101.6 mm (4”) copper wound voice coils, and treated paper cones.
For compactness, it's difficult to beat a vented or PR design. And you don't see many PR alignments used for pro audio purposes.
Also, a vented design that's -3dB @ 20 Hz can be designed to be usable up to 100 Hz (or more, if some vent power compression effects are acceptable). None of the higher-order designs like THs (typically usable only for 2.5 octaves or so) will be able to do that.
Also, a vented design that's -3dB @ 20 Hz can be designed to be usable up to 100 Hz (or more, if some vent power compression effects are acceptable). None of the higher-order designs like THs (typically usable only for 2.5 octaves or so) will be able to do that.
Personally don't see the use in 20Hz extension for PA. 30Hz would already be really low in general. Think 35Hz is a good compromise in general.
The bass extension needs often depend on overall SPL. If there is something audible between 30-35Hz and lot around 40Hz, it is good enough. If SPL is lower and thus 30-35Hz even lower and rather not audible, then the extension is missing to the feel and ear.
It is rare to have true need for content below 30Hz in PA. I listen a lot to DnB, deep breaks and all that bollocks, and while some note might be missed during the whole evening gig, the overal experience is full, warm and hearthy, "warbly" and vibrational. No desire unmet. I believe the missing note would hurt less than the apparatus that could reproduce it faithfully.
Yes, Bassreflex and PR design are still the ones most SPL dense designs under 250l brutto, but not cheap for speakers and amps. The speaker cones can move the air by themselves. Even fairly efficiently if run around its impedance peak a lot, but it is not a cheap trick at all. But those modern neo "eurodrivers" are quite good at that. Those fair 4,5" to 5,3" light coil assemblies support that when higher Xmax models are chosen. With oldschool heavy duty stuff, such us hi-fi/car audio, the design, power requirements and price goes through the roof. From time to time I look into that direction with "what if" feel, and no. Never appeared as best choice ever.
The XOC looks very good for general purpose use if the size and weight is not an issue.
It is rare to have true need for content below 30Hz in PA. I listen a lot to DnB, deep breaks and all that bollocks, and while some note might be missed during the whole evening gig, the overal experience is full, warm and hearthy, "warbly" and vibrational. No desire unmet. I believe the missing note would hurt less than the apparatus that could reproduce it faithfully.
Yes, Bassreflex and PR design are still the ones most SPL dense designs under 250l brutto, but not cheap for speakers and amps. The speaker cones can move the air by themselves. Even fairly efficiently if run around its impedance peak a lot, but it is not a cheap trick at all. But those modern neo "eurodrivers" are quite good at that. Those fair 4,5" to 5,3" light coil assemblies support that when higher Xmax models are chosen. With oldschool heavy duty stuff, such us hi-fi/car audio, the design, power requirements and price goes through the roof. From time to time I look into that direction with "what if" feel, and no. Never appeared as best choice ever.
The XOC looks very good for general purpose use if the size and weight is not an issue.
BMS 18N862 and tune to about 30Hz. Expensive but the best you can do.
As others said I would also not do a real 20Hz woofer, it's wasted energy. Loud 30Hz are already pretty special for PA.
https://bmsspeakers.com/index.php-190.html?id=18n862_overview
FaitalPRO 18XL1800 goes also deep with plenty Xmax but has higher THD as the BMS. I would use the BMS as "full range woofer" over a 2 way with the Faital just for the lowest octave - smaller, easier and after all cheaper.
As others said I would also not do a real 20Hz woofer, it's wasted energy. Loud 30Hz are already pretty special for PA.
https://bmsspeakers.com/index.php-190.html?id=18n862_overview
FaitalPRO 18XL1800 goes also deep with plenty Xmax but has higher THD as the BMS. I would use the BMS as "full range woofer" over a 2 way with the Faital just for the lowest octave - smaller, easier and after all cheaper.
Just a little note that going <30Hz with a PA system can be a lot of fun, but you end up using silly-overkill drivers & amps.
For example, a small theatre that I provide PA for occasionally is normally served just fine with a 1x12" 40Hz ported subwoofer with 1KW input.
Once, we wanted to do some special effects which involved going loud and low. 3x Faital 18XL1800, 3KW per driver, sealed boxes. In the nearfield, the frequency response reached its maximum at 18Hz.
In both cases, the main speakers were some 10" coaxials, which kept up fine in each case.
It was a fun show, but I trust this indicates the order-of-magnitude difference that's required to get that extra LF extension.
Chris
For example, a small theatre that I provide PA for occasionally is normally served just fine with a 1x12" 40Hz ported subwoofer with 1KW input.
Once, we wanted to do some special effects which involved going loud and low. 3x Faital 18XL1800, 3KW per driver, sealed boxes. In the nearfield, the frequency response reached its maximum at 18Hz.
In both cases, the main speakers were some 10" coaxials, which kept up fine in each case.
It was a fun show, but I trust this indicates the order-of-magnitude difference that's required to get that extra LF extension.
Chris
Just pondering, what about those fan style subs could they be souped up to cater for such low bass at high spl?
Or what about using compressed air?
Or what about using compressed air?
It's nothing special, but has done well for me for a good number of years now: https://www.diyaudio.com/community/...-40hz-from-28l-net.416562/page-6#post-7793667
Driven by one channel of a Powersoft T602. IIRC, the driver was a custom-built one for Void. I just happened to buy one on eBay at the right time - haven't seen any since. It has a large rubber surround, dual spiders, 3" voicecoil and a large ferrite magnet with plenty of ventilation.
Typical usage for me is moderate-SPL for 1-200 people (depending on the program material).
Chris
If you're talking about something like the Eminent rotary subwoofer, those typically require a very large enclosure, which is at odds with the original poster's wishes.
www.soundandvision.com/content/eminent-technology-trw-17-rotary-subwoofer
"it requires a manifold chamber in front of the unit to absorb the random noise of the blades rotating. In the photo above, a manifold is being built for a trade-show demo; the blades will be positioned in the circular cutout.
Because the effective radiating area is so large, the TRW-17 also requires a huge backwave chamber, which is typically an entire room, attic, or basement."