Has anyone ever experimented with this?
I got the idea from the older Cerwin Vega speakers that use a bag filled with SF6 gas. I understand they did that to make the enclosure appear larger and extend the low end cutoff, but I wonder if employing a resonator inside of a sealed box would be able to critically dampen the primary box resonance?
If a properly tuned helmholz resonator can work to attenuate certain resonant frequencies and droning in a car's exhaust system, why couldn't it be used to dampen the sealed box resonance of a speaker?
I got the idea from the older Cerwin Vega speakers that use a bag filled with SF6 gas. I understand they did that to make the enclosure appear larger and extend the low end cutoff, but I wonder if employing a resonator inside of a sealed box would be able to critically dampen the primary box resonance?
If a properly tuned helmholz resonator can work to attenuate certain resonant frequencies and droning in a car's exhaust system, why couldn't it be used to dampen the sealed box resonance of a speaker?
Technically this is possible, although a closed transmission line or just dividing the cabinet in smaller compartments are often just easier solutions. It's quite tricky to tune a HH-resonator very well.
In practice, most closed systems are small enough that these resonances (standing waves) are outside the bandwidth of the woofer anyway.
In practice, most closed systems are small enough that these resonances (standing waves) are outside the bandwidth of the woofer anyway.
FIY, Yamaha NS-5000 use them (no detailed info, only marketing):
The cuboid enclosure unifies internal standing waves at a specified frequency, which are cancelled by a newly developed resonance tube (patent pending). This technology eliminates the previous need for the huge amount of sound-absorbing material inside the enclosure. The result is the virtual elimination of standing waves with amazing efficiency and pin-point accuracy—to energetically revive the essential presence of music, formerly lost by sound absorption.
https://europe.yamaha.com/en/products/audio_visual/speaker_systems/ns-5000/features.html
And smaller ones for drivers:
Newly Developed Acoustic Absorber Eliminates Sound-absorbing Material to Revive the Original Presence of the Music
The cuboid enclosure unifies internal standing waves at a specified frequency, which are cancelled by a newly developed resonance tube (patent pending). This technology eliminates the previous need for the huge amount of sound-absorbing material inside the enclosure. The result is the virtual elimination of standing waves with amazing efficiency and pin-point accuracy—to energetically revive the essential presence of music, formerly lost by sound absorption.
https://europe.yamaha.com/en/products/audio_visual/speaker_systems/ns-5000/features.html
And smaller ones for drivers:
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Hi,
It is used in the Yamaha Ns5000 ( a few of them iirc edit:Olegtern was faster! ) and this is what Kef named 'mat' which in practice is a serie of tuned helmotz for what i understand ( it is used to be called meta material but for me it's just what i described).
https://fr.kef.com/pages/metamaterial
It is used in the Yamaha Ns5000 ( a few of them iirc edit:Olegtern was faster! ) and this is what Kef named 'mat' which in practice is a serie of tuned helmotz for what i understand ( it is used to be called meta material but for me it's just what i described).
https://fr.kef.com/pages/metamaterial
And Patrick Bateman has documented his experiments with meta material on this site.
But there have been numerous DIY designs with internal HH absorbers (they are popular in Germany...). I guess they can come in handy when internal dimensions urge you to do something about standing waves. But applying other means is probably just as useful.
But there have been numerous DIY designs with internal HH absorbers (they are popular in Germany...). I guess they can come in handy when internal dimensions urge you to do something about standing waves. But applying other means is probably just as useful.
I would like to try a series tuned item like the Kef's one.
Maybe it could be availlable in one or two years as spares from Kef?
After all drivers and even 'Shadow Flare' are...
Maybe it could be availlable in one or two years as spares from Kef?
After all drivers and even 'Shadow Flare' are...
I'm actually referring to absorbing both primary and standing wave resonances. The posts and links above are interesting reading. Using a TL is probably more practical to obtain similar results, but I want to retain the natural air spring of the cab so a high compliance driver with low Rm can be utilized.
A flow resistive vent is very effective at what I'm trying to achieve but the lack of air spring will negate the ability to safely use a very high Cms driver without a steep HP, plus I'm not using dsp either. So far I've had good success with the Variovents but it becomes very non linear at higher drive levels and is sensitive to barometric air pressure fluctuations and humidity.
You don't lose the air spring. All that happens is that the damping is varied. If you took the back off the cabinet then you'd lose your spring, but the resistance is designed to retain the correct amount of spring, just like a lower Q resonance.
The compliance of the cabinet will stay the same, otherwise it means that de Fb will shift as well.
I was actually referring to static "air spring" or better put, an air spring that is effective down to single digit frequencies. Obvuously any sealed cab has losses and leaks, but those losses wouldn't show up as counteracting the imperfect static air spring until down past a few Hz. A resistive port or basic port would have long ago stopped being effective at those frequencies.
So what I'm getting at is a sealed box with an internal resonator would still have an effective air spring down past a few Hz, where a typical ported or aperiodic enclosure would have long quit being effective of restoring the LF driver's cone to resting position. A sealed box would control the woofer down less than 5 Hz and be less prone to subsonic oscillations ie. turntable rumble. This would make an electronic HP filter unnecessary. Thats the main purpose of this whole idea.
So what I'm getting at is a sealed box with an internal resonator would still have an effective air spring down past a few Hz, where a typical ported or aperiodic enclosure would have long quit being effective of restoring the LF driver's cone to resting position. A sealed box would control the woofer down less than 5 Hz and be less prone to subsonic oscillations ie. turntable rumble. This would make an electronic HP filter unnecessary. Thats the main purpose of this whole idea.
An aperiodic vent ideally would not unload the driver at low frequencies like a port. It is intended to retain the air spring as much as you'd find with a closed box larger than the one being used. Of course this all depends on being able to make one that is resistive.
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In a simulation internal Helmholtz resonators are a simple way to kill specific resonances and afaik the way Mr Helmholtz initially designed the box with a hole in it wasn't for boosting more for killing frequencies. In Germany we have mainly two DIY magazines for speaker building and one of those uses internal HH in transmission lines.
I did one of those kits and experimented with and without this volume and couldn't find an acoustical difference. The HH got a very narrow bandwidth and if it isn't on the right place for exactly the right frequency it won't work. I assume that's the case in my experience and I would avoid those magic boxes in a box. They make the building and the design more complex and the effect might work not will work. The biggest flaw of internal structures like these are that you cannot access them for changing the damping material - depending on the design.
There must be a reason why it's only a topic in DIY and not for retail speakers...my 2ct
I did one of those kits and experimented with and without this volume and couldn't find an acoustical difference. The HH got a very narrow bandwidth and if it isn't on the right place for exactly the right frequency it won't work. I assume that's the case in my experience and I would avoid those magic boxes in a box. They make the building and the design more complex and the effect might work not will work. The biggest flaw of internal structures like these are that you cannot access them for changing the damping material - depending on the design.
There must be a reason why it's only a topic in DIY and not for retail speakers...my 2ct
I agree the bandwidth issue would make it unpredictable and impractical. Knowing this, I still am curious how a HH could apply to a simple sealed box. The deterrent for me is the non linear behavior you get at different port velocities and sensitivity to temp changes.
