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b&c 21sw low tuned BR |
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JonB67 ![]() Young Croc ![]() Joined: 22 April 2016 Location: UK Status: Offline Points: 1368 |
![]() ![]() ![]() ![]() ![]() Posted: 28 December 2021 at 8:16pm |
Thats insane.
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JonB67 ![]() Young Croc ![]() Joined: 22 April 2016 Location: UK Status: Offline Points: 1368 |
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The software is free. Its not hard to do. Why build based on what you guess is happening when you can see the facts laid out for you by the software?
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toastyghost ![]() The 10,000 Points Club ![]() ![]() Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10883 |
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Whole Body Vibration is a field of intense study - the benefits and issues caused by it are still under dispute, but there is a great paper that explored the thresholds and frequencies for inducing it in human listeners with subwoofers:
https://www.aes.org/e-lib/online/browse.cfm?elib=20383 The whole paper is worth a read, but you can se from the abstract that you 'only' need a linear sound pressure level of 107 dBZ at the listener from subwoofers to induce WBV. Also, the resonance of different body parts was assessed across all test subjects: ![]() Note the x-axis scale is in 25 Hz divisions. The results clearly show that the majority of WBV is induced by frequencies between 60 Hz and 125 Hz, for all body parts. The peaks are resonances and sit at harmonics of the ~60 Hz initial peak. If 'maximum perceived impact' is the goal, then you'd be better off focusing on designs that really hammer home the upper bass region. Of course, I'm known for deploying systems with extended LF response. Part of that is based on an agreement I have with my good friend Jo Burton's research which indicates that people perceive a system that plays an octave lower as being louder and of better quality than one which 'only' reaches 30 Hz: https://www.aes.org/e-lib/browse.cfm?elib=19179 However, I'm not going to lie to anyone and say that going for this is easy. The rule of thumb is that you need twice as much displacement and energy to achieve the same sound pressure level with an extra octave extension. The boxes need to be bigger - much bigger - and the diaphragms must be very controlled to prevent thermal runaway or cone damage from rocking modes. The reality is that several well designed 18" reflex boxes with those modern drivers will likely have nearly as much 20 Hz output as a pair of 21" tuned super low, but with way more output in the more useful upper bass region. It's also more flexible as you can bring the number of boxes needed for the show. If you feel that you want or need a dedicated infra box later, then look at adding a set of dual 21". But be warned, you'll spend a lot of cash on drivers, wood, amps and transport to keep up at concert levels... as an example, we have some custom dual 21" tapped horns that I designed for just this purpose. Similar to the TH221 from Danley, but DIY because it was hard to justify the equivalent cost of twelve more TH118XL just to hit these lower frequencies without proof that it won more business. Four of them keeps up with twelve TH118XL playing everything 30 Hz up, which is impressive - except for the fact that once you put those four boxes in a van, there's no space or weight limit left for anything else. They're 250 kg each. I've also worked with a 40" Powersoft M-Force box from Traction Sound as part of my time with the AUDINT sound art crew. That's a reflex box tuned to 16 Hz, the size of a small car, and it's loaded with cutting edge linear motor technology costing many thousands of £££. It's great, but it's not enough for a concert alone. Far from it. My tapped horns are much more efficient than a ported cabinet at those frequencies, so you'd need the same or more physical volume to achieve the same. Stick with what you have, and design a big dual 18" reflex with an oversized, flared port in the middle. There's plenty of examples out there. Use a proper modern DSP amp with excursion, thermal and peak limiters to drive it to the fullest. Then revisit later. |
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madam ![]() Registered User ![]() Joined: 14 June 2020 Status: Offline Points: 18 |
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I have a SubPac M2, that have a range of 10-200 Hz.
Some of my favourite tunes makes my teeth rattle and my vision blurry and all of these happens in the really low freq parts. I wanted to build a few of the Martin Audio WS18X cabinets for the 6 brand new Martin Audio DLS846 drivers I have. But I just changed my mind, and tought better sell the drivers, and get 1 or 2 even biger and more powerful 21 inch units. So I can have lower overall weight, less AMPs, less work. I love the corner ported Martin designs, I know it is not the best, but results a small front panel, braces the sidepanels, no need to get some tubes, I can get 4 of them for almost free. BTW if anyone wants up to 6 of the NEW DLS846 drivers, just let me know.
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DMorison ![]() Old Croc ![]() Joined: 14 March 2007 Location: Aberdeen Status: Offline Points: 1580 |
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+1 to checking exactly how low you need to get first.
Here's an example of just how long you need to make the vent to get down into home cinema type LF ranges - and bear in mind that for PA SPL's you'd probably need an even bigger vent area, further increasing the required length.
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JonB67 ![]() Young Croc ![]() Joined: 22 April 2016 Location: UK Status: Offline Points: 1368 |
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Also worth running a spectrum analyzer on the tracks you think are the lowest of what you play and see what their frequency actually is. Audacity will do this and is free to download. |
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cravings ![]() Old Croc ![]() ![]() Joined: 30 January 2007 Location: Ireland Status: Offline Points: 7392 |
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There's a user on here called crashpc I think, and he's crashpccz on YouTube who has done a good bit of testing 21s in small reflex cabs
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smitske96 ![]() Young Croc ![]() Joined: 16 February 2016 Location: The Netherlands Status: Offline Points: 1007 |
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The lowest i would aim for PA would be 30Hz. What kind of dimensions do you have in mind? Also important, what kind of amp do you have to drive it?
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madam ![]() Registered User ![]() Joined: 14 June 2020 Status: Offline Points: 18 |
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I would use it for PA, but I love Detroit electro and other sub-bass heavy materials.
I know about SB-15121. Any other suggestion? I would better DIY. |
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VECTORDJ ![]() Registered User ![]() ![]() Joined: 11 June 2006 Location: United States Status: Offline Points: 489 |
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QSC sells a theater sub with a B and C 21 that appears to be approx 20 cubic foot. Very deep tuning. Check out Their spec sheet.
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JonB67 ![]() Young Croc ![]() Joined: 22 April 2016 Location: UK Status: Offline Points: 1368 |
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For home cinema?
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bob4 ![]() Old Croc ![]() ![]() Joined: 29 February 2004 Location: Finland/Germany Status: Offline Points: 1779 |
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