The 'box' sound is noticeable after you eliminate it. When I first tried stone lined enclosures I replaced the cabinets while keeping the design unchanged. What surprised me was the tweeter attenuation now necessary with the stone cabinets. IIRC it was around 2-3dB. It was a two way 12 litre design where 3/4 mdf lined with 3/4" marble conglomerate and multiple stone cross bracing replaced 3/4" mdf with a single mdf cross brace. To say the improvement in transparency was large would not be overstating it.
So, obviously get rid of the rectangular box. This is difficult without creating one of the world's ugliest speaker. I managed to do just that -
I took a traffic cone and glued it to a cement forming tube. I filled the space between the cone and tube with sand. I stuffed the cones with polyfil, with the driver mounted at one end of the tube, the other a sealed panel with the connecting terminals.
Imagine how ugly a pair of, say, 8" X 24" tubes are, that need to sit horizontally on stands? There's almost nothing you can do to make them have eye-appeal. Acoustically, I imagine the "dagger" conical shape of a soft material, with 360 deg of sand dampening about it, probably presents the back side of the speaker with a pretty inert space.
Even though the "cabinet" is only 1/4" paper, I also expect its continuous curvature, while loaded with sand, isnt going to vibrate as an unbraced flat panel might.
I took a traffic cone and glued it to a cement forming tube. I filled the space between the cone and tube with sand. I stuffed the cones with polyfil, with the driver mounted at one end of the tube, the other a sealed panel with the connecting terminals.
Imagine how ugly a pair of, say, 8" X 24" tubes are, that need to sit horizontally on stands? There's almost nothing you can do to make them have eye-appeal. Acoustically, I imagine the "dagger" conical shape of a soft material, with 360 deg of sand dampening about it, probably presents the back side of the speaker with a pretty inert space.
Even though the "cabinet" is only 1/4" paper, I also expect its continuous curvature, while loaded with sand, isnt going to vibrate as an unbraced flat panel might.
The traffic cones or sports cones make superb rear chambers for mid range or full range drivers. It’s what is used on my TL speakers but is hidden inside the main TL cabinet.
Stuffed with polyfill, they absolutely do not sound boxy.
Wrapped with foil covered butyl to reduce resonances:
More in this thread:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
Stuffed with polyfill, they absolutely do not sound boxy.
Wrapped with foil covered butyl to reduce resonances:
More in this thread:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
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The air spring in an underdamped enclosure (such as one that is too small) not only provides a force to return the cone back to center, it propels it past center and back the other way at which point the power input to the system not only replenishes energy in the spring lost to damping but adds even more, doing this many times in succession and greatly enhancing the movement of the cone - hence resonance. The problem is that when the input to the system stops, the cone vibrates back and forth many times before stopping as it takes a long time for all the stored energy to be dissipated.
A highly damped system differs in that almost all the energy stored in the air spring has been dissipated by the time the cone arrives back at centre, hence the air spring acts to almost exclusively oppose the force that the voicecoil is creating.
The subjectively accepted optimal solution (optimally damped, Q=.707) is one where the air spring helps move the cone at frequencies where the speaker would produce attenuated output, but isn't underdamped to the point that the resonance is subjectively noticed - no boost in frequency response and a group delay that isn't longer than typical musical instruments.
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I don't want to sound disparaging, when bells ring they have four nodes and four antinodes, if you stick an odd number of lumps ( heavy, but damped; perhaps silicone mixed with lead shot would work ) evenly spaced around the bottom on the inside might make a difference, perhaps they just wont be exited. I'd go for an odd number of feet as well.
Regarding 'overswing' of the woofer, in that situation the back EMF will still be developed, and will, as the waveform has now changed to a later part in time, be either in phase with or antiphase with this later signal.
It will therefore add to or subtract from the current in the amplifier O/P cct., across possibly several cycles (at the higher end of the frequencies which the driver passes).
This will, on a sine wave result in an asymmetrical waveform, and peaks of high current in the O/P cct because the effective impedance of the driver changes
It will therefore add to or subtract from the current in the amplifier O/P cct., across possibly several cycles (at the higher end of the frequencies which the driver passes).
This will, on a sine wave result in an asymmetrical waveform, and peaks of high current in the O/P cct because the effective impedance of the driver changes
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