Legend? Myth? Inclination? Probably some or all of those, and a few others beside. 😉 I know many who revere the design are well aware of its limits -they just don't care, in the same way fans of most other types of speakers are willing to overlook their limits for what they do well. Don't forget, lots here & elsewhere for e.g. are happy with a pair of 3in wideband drivers for similar purposes -or even more, in a suitable horn etc. Depends where your priorities are.
Rogers was just one of a handful of companies who applied for a license to produce the design commercially BTW -a good few others did too, from Goodmans to Spendor. It was designed by the BBC's internal R&D team; they had to rely on external manufacturers as the corporation doesn't have any production facilities of its own.
Don't do that - you need damping material in the inside!
But you can use acryl with paint on the inside which also can give a cool/unusual look and you hide the inside mess.
Waterfall get around that one with their transparent glass cabinets by reverting to ye tried and trusted methods of the pioneers. Well, partly anyway. They stick a natty leather-covered cardboard / similar tube around the back of the driver with a sufficient amount of damping material in it & a bit of grill cloth at the end for aesthetics. Their 'Acoustic Damping Tube Technology' [no less]. 😉 Just a visually more attractive version of the old approach of stapling layers of grill cloth or fibreglass over the back of the driver until the old click test indicated no audible ringing. Notwithstanding some [extreme] care over wire-dressing & crossover appearance where appropriate -job-jobbed.
Granted -given the dimensions of the Waterfall boxes vis-a-vis those back in the day, when this was more or less standard practice, I suspect the new speakers are somewhat less suited to damping this way than their ancestors as it'll do the square root of zero for suppressing the longitudinal. But that's progress for you.
Presumably the PBR loading helps sort that to the point it's not an issue.
Granted -given the dimensions of the Waterfall boxes vis-a-vis those back in the day, when this was more or less standard practice, I suspect the new speakers are somewhat less suited to damping this way than their ancestors as it'll do the square root of zero for suppressing the longitudinal. But that's progress for you.
Presumably the PBR loading helps sort that to the point it's not an issue.Attachments
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We want to eliminate as much time-smear as possible. One of the reasons i am an adherent of midTLs.
By not using MDF that particualr source is eliminated.
dave
Me too. But people. My buddy with the LS3/5A loves his QUAD 405, has Spendor BC1 in the lounge and triple QUAD 57s in the listening room.
dave
Can I ask if you've ever messed with an automotive shock absorber.. pushed a screwdriver through one of the mounts and stand on it while you use your weight to compress and extend it? Ever tried to move it quickly? That resistance is at work.
Let me also question your first premise about the cabinet taking energy from the drivers. It is going there anyway and would be radiated through the cabinet walls, which you don't want. The damping is actually reducing this resonance by helping to stop movement.
Hmm, I should have known that I was not the first to think of it! To be honest it's an intimidating idea, but the acoustics are pretty interesting, since a sound wave in fluids and solids apparently works differently. I think the ideal would be to get total internal reflection of sound waves at the smallest critical angle possible, so if only I could fill one of the voids with Chlorine Gas (apparently has a very low speed of sound) we'd really be in business. Then there would be something more insane than a plasma speaker out there....
My plan is not actually to use panels per se but continuous curved structures for the most part. This is probably the other advantage of 3D printing, you get arbitrary shapes "for free". That said, I think a ~1.5mm thick bit of plastic is likely to move a good deal more than 16mm of MDF. I have read that spheroid structures are more or less free of panel resonances, but you still need a stiff structure either way to avoid "balloon" effects?
Actually... yes, this is possible but I haven't seen it before. You can get TPU filament (thermoplastic polyurethane) which is quite flexible. You can also get 3D Printers with 2 nozzles, so they can print a different material in different parts of the print as needed. However, TPU is known to be a little tricky to work with and 2-nozzle printers likewise, plus expensive. Haven't used one before. But it's a really interesting idea you've raised here. In addition to filling in layers of concrete or whatever, you could have the inner chamber of the speaker be one big rubber spring, of sorts. I don't know if this would do more damping, or just delay reflection of waves enough to smear them even more...
Yeah, the old Altec, etc., theater, prosound horns when used for HIFI added a lot 'color' to their sound that was normally kept either behind a cinema screen or outdoors where the crowds, sheer SPL drowned it out. That said, I never cease to be amazed at how many prefer it in their so called high SQ systems.
Re the bladder 'thing', back in the '90s someone was marketing subs IIRC, but can no longer remember what was in them or if there were options.
Someone mention spheroid structures ? For anyone in England, I've noticed that Homebargins currently have large (approximatly 16 inch's diameter) hemispherical stainless steel bowls, they have an external lip, so perhaps the could be glued together. I presume that car damping mats stuck inside would deaden them. I'm almost tempted to try one as a parabolic solar reflector (even though they're not parabolic).
So, I will make sure to have an odd-shaped internal chamber to avoid that, no difficulty there. Also, I think what's often overlooked about spherical enclosures is that spherical harmonics do not follow what we normally think of as harmonic ratios. While you certainly want to avoid the dreaded 'very large resonance at the diameter of the sphere' thing, the higher modes inside a sphere don't follow the normal integer ratios. My personal impression (having listened to a spherical speaker once) is that these harmonics are less familiar and therefore less offensive to the ear than "box" harmonics. Consider what a ball sounds like when you bounce/kick it... pretty different from what a box does when you hit it. I think this ends up subjectively more like noise and less like ringing when you pump music into it. But that's an assumption on top of superficial knowledge.
As was noted in the other thread, if water-filled enclosures were a great idea, they would have caught on by now. Consider how cheap it would be to ship large speakers if the cabinets were basically just big, empty water jugs! Let the user fill them with a hose when they get home. Injection molded for pennies in China and the whole thing would weigh about 5lb on top of the drivers... what a dream...
I'm not so sure about the 'caught on by now' bit. You've the added constructional complexity, and that idea has been introduced for washing machines, with an empty water tank for shipping, that is filled in situ, replacing the usual concrete. It was raised about 6 years back, pretty much everybody who heard of it said 'wish I'd thought of that', 'what a brilliant idea' or words to that effect, and -nothing. I don't know of any on the market at all. There might be some, for all I know, but I certainly don't recall seeing any when I last wombled through the local Currys electrical store. Granted, I wasn't looking, but I've not heard anybody talking about having one either, so YMMV on that. Not that I'm saying it isn't a good / functional idea -just that it's not quite so simple to produce as a couple of sheets of wood / similar, so you'd need a company with some serious budget behind it to get it to market.
So, you have a good point which is that injection molding for large things like (say) a big 3-way floorstander is very expensive to tool up, $250K minimum and probably more. So, it would only be done for speakers where they intend to sell a lot of units. They would also look pretty weird. You'd need to have a lot of confidence in the design to invest in it, and it would have to be a weird combination of cheap-looking/feeling but also high-end to work. Given how audiophiles operate (nothing newer than 20 years seems to catch on) it's not that appealing.
Also, others have pointed out that sound waves travel perfectly well through water, and it's only a little more dense than MDF, so in DIY-land you get all the problems of water without obvious benefits.
For the washing machine thing... it's possible the water 'bladder' would need to be too large - for the same weight as the concrete bit it'd have to be 2.5x bigger.
Or, perhaps they don't have confidence in the customer filling it up correctly, leading to the washing machine flinging itself around the room and killing somebody, who knows. Maybe the insurers or lawyers killed the idea. However, in those businesses, designs move on the scale of years, not months, so it may still be in the works.
Also, others have pointed out that sound waves travel perfectly well through water, and it's only a little more dense than MDF, so in DIY-land you get all the problems of water without obvious benefits.
For the washing machine thing... it's possible the water 'bladder' would need to be too large - for the same weight as the concrete bit it'd have to be 2.5x bigger.
Or, perhaps they don't have confidence in the customer filling it up correctly, leading to the washing machine flinging itself around the room and killing somebody, who knows. Maybe the insurers or lawyers killed the idea. However, in those businesses, designs move on the scale of years, not months, so it may still be in the works.
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Hope springs eternal. 😉 My back would thank them for getting a move on, I know that much...
The driver would need to be concentric with the sphere, not mounted on the side.
I have to wonder whether it isn't the outside of the sphere you were hearing acting as a baffle for sound travelling normal to it from the driver as a source.
I'd consider damping material as the main device inside the sphere.
The spherical speakers I heard sounded better than they had any right to... they were made of pitifully thin plastic (maybe 3mm), had a shallow port, and no absorptive material that I could discern. They probably used a decent enough driver, but at the time I attributed the sound to the shape itself. I could not imagine a box-shaped speaker constructed that way sounding anything but clownish, which doesn't prove anything, but that was my thought at the time.
My own plan is to use copious damping / absorption material in there, but irregular surfaces never hurt anybody either.
I am not going to go strictly spherical at all, my idea is to basically have a 3-way tower-ish shape with the top bit (mid & tweeter section) almost spherically rounded, but with an extended rear section (almost teardrop-shape) and an extension downward to accommodate a 10" woofer. So completely rounded over in every sense but not a ball either. Picture the robot baby of EVA from Wall-E and a KEF Blade. Color TBD subject to WAF systems design committee.
Didn’t Celestion use Aerolam in some of their high end speakers? It two aluminum skins with aluminum honeycomb in between.
I have done subs in a Sonotube sandwich, two different diameters of tube nested with sand in between. I routed end caps with grooves for the two tubes to set them evenly apart.
I’ve also used schedule 80 pvc piping as a cabinet. It is incredibly dense and being a pipe the pressure is evenly distributed. The walls are like 1/2” thick and well damped.
I have done subs in a Sonotube sandwich, two different diameters of tube nested with sand in between. I routed end caps with grooves for the two tubes to set them evenly apart.
I’ve also used schedule 80 pvc piping as a cabinet. It is incredibly dense and being a pipe the pressure is evenly distributed. The walls are like 1/2” thick and well damped.
Hi thank you sincerely for helping me to make up my mind But if a very stiff material is mandatory to avoid energy absorption by the cabinet then the choice is limited Metals With steel stiffer than aluminium
However if the combined mass of cabinet+woofer will be not high enough the forces generated by the moving cone will make the cabinet to shake Am i right ?
So the metal cabinet must be also quite heavy How much heavy compared to the cone moving mass i really dont know
ans the Celestion SL600si weight is only 11.25 lbs/each. This is nothing
If they image greatly this is the final evidence that cabinet stiffness and not mass is the key parameter
A very very important conclusion in my mind Now the problem is to find some of that honeycomb ?