What about a sub with a spring bass trap built in?
Oh no name callin’ other than the normal name callin’, just sayin’
Oh no name callin’ other than the normal name callin’, just sayin’
This idea could work. You definitely want it in a sealed box (vented won't do the same thing). You will need to put some sort of damping material on the inside back wall to cushion the "woofer spring" and increase the bass trap bandwidth. The hard part here is trying to determine the "weight" of the passive radiator. You can try to use a tuned membrane bass trap calculator, but you'll need to figure out the "weight per square inch" of the passive radiator. Then it's the volume of the internal cabinet. I think it's much easier to engineer a tuned membrane bass trap because the area of the membrane matches the area of the box and the entire membrane has equal distance to the back of the box. Not saying this can't be done, but it is entering into engineering rocket science here.
I have only seen one active bass trap made and it is called "Active Bass Trap" made by a company called Bagend. It is similar to the type of technology you find in noise-cancelling headphones. It uses a microphone mounted on the front of the cabinet and then uses a small amp with a 10" woofer to create the opposite "cancelling" waves. I have read that it's somewhat effective. You may need 2 or 3 of these.
You may be better off doing a design where your rear corner subs are fired in opposite polarity of your front subs. I forget what this is called (something like "double-bass" or something).
I've seen subs that double fire. Isobaric, and daisy chained. The active driver on the inside of the chamber is fired out of phase.. They dig pretty DEEP.. Face to Face in an open baffle is pretty impressive too.
It's always the same with bass, distortion. Not hard to make a lot of BASS but GREAT bass in a room is tough... Back walls are BAD.. Retracting walls? 007 stuff...
oldhvymec, can you catch an explosion in a tin can? I think you'd better think up a more viable project. Let's see...making subwoofers is fun. How's about designing a room that has no bass nodes. Maybe you could turn your roof into a passive radiator, put it on springs. Watching it bounce would be cool.
Maybe springs on the French doors will work as a poor mans substitute. Besides they are already there..:-)
I'm not trying to "catch it all", BUT I would like to make a dent in the frequencies I'm trying to work with. 45-55, 75-85, 115-125, 250 (?)
pretty normal bumps and valleys. The 250 up is pretty easy. Wall panels but below 125 hz... and a fairly easy to make trap? Not to darn ugly.. Just ugly enough..
A guy was making exactly what I wanted BUT he quit making the ONE trap I really liked.. Naturally!! I think the proper term is SOL.. LOL
With me any more 15 min 3 times a day.. My hand quit.. Twist up like pretzels (sp), silly things.. I can get a lot done in 45 min. though..
I wonder if a sail mounted to a box, or a collection horn into a dampened box? Or into water? LOL turn sound into bubbles? Why not..
I’ll look I’ve found two types that are adjustable.
One of them only does one frequency at a time and takes 6-8 for 2400 CF. That’s a typical 300 foot floor X 8 foot ceiling. A lot of listening rooms are close to that..
The second one I found does 3 frequencies but the guy QUIT making them... 900.00 a pop too. Two would have worked perfect with a few wall panels two 6 foot HEAVY drapes (floor to ceiling) on the side walls and a rear wall mods (2 x 36" French doors) opened and HEAVY corner drapes drawn to cover the doors faces.. The panes of glass actually work pretty good.. High ten glass 6 x 8 pains with actual mahogany hard wood dividers for 16 panes.
Down to making corner adjustable traps or MAKING something for sure..
The 12CF subs got some HUGE sides... 60H x 18W x 22D. 4 actually.
I know there is a way to make GREAT muffler for Gods Sakes.. I’m a mechanic.. I can sure make noise.. NOW to quiet STUFF down.
Besides I’m still thinking vent the noise into water. The bubbles can double as an antistatic reducer and moisture therapy for my lungs.. :-)
Back to Murdock Mysteries
Not to compress ausaudio As a muffler.. as a filter.. You ever see a water muffler?
What about WET stacks on marine diesels? You'll have to trust me on this one.. A pair of V12 Cats in a tug, can get LOUD (130+ db) yet quiet as a mouse with water muffs..130+ db easy uncorked.
I use to work on Hydro-blasters.. 15,000 psi HP water jets. Water does not compress.. LOL BUT is sure quiets things down, and it transfers SOUND pretty dog on well, too.
Those noisy POS used 6V53 Detroit (2 cycle diesels) with "WATER" mufflers installed into 3000 gallon scrubbers. Noise and Opacity test requirement, because of the location. You had to keep a 25 foot distance between you and the scrubber, too. The harmonics would crumble your bones..
Hydro water plants are the same way.. 15-30 minutes exposure, your DONE. Turbine growl is a bone grinder.
It's easy to fix stuff (Gas Monkey Garage). UNDERSTANDING what it does and is doing is another thing..
I need BASS mufflers, yup Dual INTAKE mufflers :-)
Old Heavy Master Mechanic, that gladly retired..
Put together a large array of noise canceling headphones modified with an adjustable low pass filter.
600 pairs of head phones. I'll head to the bank for a loan. What should I say I need the money for? I need 100K for my ??K system to add headphones.. "LOAN DENIED" LOL Big ol' red letters..
Start looking like Master Ms digs, with his "enbeddings", love that guys way of tinkering.. :-)
A: Wouldn’t it be easier to adapt a swarm subwoofer setup as others have done to even out the peaks and valleys? Perhaps utilizing in-wall subs if floor space is tight.
B: IME, a crappy sounding room will never be a great sounding room no matter how many bandaids you throw at it. Can a crappy room be improved? Yes, but it will never be a great sounding room.
I think Acoustic Fields builds something similar to what the op is referring to. A diaphragmatic absorber. They do or used ro sell plans for them to diy. Its pretty complex with a carbon substance inside as well, if I remembercorrectly. I believe they work with the lowest of bass frequencies. They are big, heavy and expensive.
The flex part of the box is a perforated piece of wood sandwiched in between the multiple layers of the box. There's not much products that can compete with its effectiveness at those low levels of bass.
That's the purpose of the adjustable spring bass traps. 125 hz and <
As far a DBA or Swarm they are the bandaids. The whole reason they were developed to begin with. I got away from multi subs a long time ago 20 plus years now.. I use 2 sometime 3 OB dual servo subs with full blown DSP controlled MB columns. There is not a gear issue ONLY a room issue. I confess...:-)
It is an easy way to even out the peaks and valleys BUT still not the best.
I like a servo sub system with Narrow MB and Monitor columns. There is no need for BASS everywhere, when it's RIGHT there.. A lot of the nulls are corrected by MB column placement. The servo software is pretty good BUT it is software none the less.. Just like the DSP.. Not all DSP software is created equal. I use a Behringer 2496 for all the BASS management.. Easy peasy.. Active sound management, I just use it for 300 hz and down.. 300 hz up its all passive.
This is the PRE check list for a front room. Not the main room but it is my main listening room for now.. Paint, floors and drapes. They are going to be made. CLOSE.. Drapes and traps. of course there is a phono stage on the way.. 3 more months.. I'm cutting it close..
Thanks for your input though, rhljazz
@oldhvymec - I did find a broadband absorber, designed by Dennis Foley of Acoustic Fields.
He uses a sealed box, with perforated internal walls filled with activated charcoal.
I have visited the Genolan caves in New South Wales and the caves are used for concerts and recordings beacause of the acoustical properties of the porous limestone formations.
It uses activated charcoal within the cabinet, the micro pores do the heavy lifting. When I first read it, I remembered the caves.
He does sell plans for DIY. Currently I am building four of his QRD17 diffusers (from plans) out of solid cherry wood.
How cool is that. I use to use AC and DE in HUGE water filtration systems.. 12,000 gallon filters. We uses two frack tanks as holding and settling cells. That is when I learned about concrete and it ringing like a bell.
It took quite a few super sacks of AC to fill the two 5000 gallon stainless steel filters. It cost 15k 30 years ago for 15 super sacks. Had to turn in a core carbon too, or the price almost doubled..
I wonder how thick it has to be to BE effective? I'll check it out..