It lowers the fundamental resonance frequency of the loudspeaker assembly... the only interesting point is the loudspeaker assembly resonant frequency IMO.
Everything will resonate at a certain frequency whatever you do.
Still seems like the enclosure is getting damped instead of the driver. This is just looking at the weight and stiffened of the material of the two sides. The enclosure panels and braces have less density and less stiffness, this doing something like that basically uses the mass and the mounting structure of the driver to reduce sound caused by the panels, this difference is also more audible since the panels have greater radiating area.
The gluant cushion will damp the cabinet and the loudspeaker driver strucures.
The result is a lower resonant frequency of both assemblies (Loudspeaker chassis and enclosure).
If these two resonant frequencies were out of band (well designed), lowering the resonant frequencies will places resonances in the undesirable band, not sure that it is a good idea.
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The jelly cake have the lowest resonating frequency cake over the world, about few hertz.
It is easy to experiment, just have to make a jelly cake and put it on your loudspeaker, then put a vibration sensor on the enclosure and measure that the low RF cake lowers the RF of your loudspeaker external structure after the mecanical coupling.
RF : Resonant Frequency.
When two sources are combined coherently the pressure increases by 6 dB and the power by 3 dB, so we have to be clear which one we are talking about. I virtually always talk pressure since that's what we hear and what we measure. This 6 dB increase is purely acoustic, completely independent of any electrical or mechanical conditions.
If I place a compliant yet massive structure on the back of the magnet the mass will lower the resonance, but if this is wedged between the magnet and the cabinet then the increased stiffness will raise the resonance of the magnet structure - although the mass will tend to lower it so what really happens depends on the mass/stiffness ratio of the material. Something like rubber would raise the resonance but also dampen it somewhat.
Generally we can never lower resonances below the passband, that just doesn't work, so we try and raise them above the passband - or dampen them to make them less pronounced. In cabinets I have found damping to be the most effective both in the materials and in cross bracing.
If I place a compliant yet massive structure on the back of the magnet the mass will lower the resonance, but if this is wedged between the magnet and the cabinet then the increased stiffness will raise the resonance of the magnet structure - although the mass will tend to lower it so what really happens depends on the mass/stiffness ratio of the material. Something like rubber would raise the resonance but also dampen it somewhat.
Generally we can never lower resonances below the passband, that just doesn't work, so we try and raise them above the passband - or dampen them to make them less pronounced. In cabinets I have found damping to be the most effective both in the materials and in cross bracing.
This is IMO the most probable explanation. It is basically the dynamic range of the speakers. All speakers have a lower limit of SPL that is basically 0 dB since they are passive, but more practically, the room's noise floor. But not all speakers have the same MaxSPL and this is a very important aspect of their design. Music can have > 10 dB of peak/RMS so if you listen at 90 dB - a reasonable level - there will be peaks at 100 dB or more. The entire chain needs to handle this without any loss of coherency. I have measured many speakers that measure extremely well at 80 dB in the lab, but there small size and the limited power of their internal amps means that they are not capable of high SPL like 100-110 dB without some compression. Speakers like mine could handle 110-120 dB peaks without breaking a sweat - for a limited time of course.
Summas used the 15TBX100 and their replacement used the 15NBX100. Both drivers had a well controlled breakup region and yet it was still an issue that needed close attention to. Yes, the breakup does tend to bleed into the upper range even with sharp crossovers. Much easier to control with an active crossover than passive.
B&C woofers tend to excel in their well damped response above the cones rim resonance. This is a real issue in a two way system like mine that needs the woofer to go up to 700-800 Hz. Takes some careful work on the crossover to get it right.
What are you talking about ?
Do you know the relationship between :
Speaker's Resonant Frequency (fs)
Sealed Enclosure Resonant Frequency (fc)
Ported Enclosure Resonant Frequency (fb)
Speaker Box Calculations
It is quite interesting that both the 12" and the 15" versions of these B&C drivers have higher Lvc in neo than in the ferrite variant. And all of them have quite a high Lvc in general for a driver with a shorting ring.
That's why I didn't try them fo a power HiFi Project some time ago despite otherwise looking great on paper. But maybe it was an error not to do so. But one can't try heaps of drivers when doing things like that as a hobby only.
Regards
Charles
That's why I didn't try them fo a power HiFi Project some time ago despite otherwise looking great on paper. But maybe it was an error not to do so. But one can't try heaps of drivers when doing things like that as a hobby only.
Regards
Charles
Fs = Loudspeaker driver resonance (in free air)
Fc = loudspeaker resonance (Loudspeaker driver + enclosure... the loudspeaker is in the enclosure)
Much more than 10dB, actually. A peak/RMS range of 10dB is typical of heavy metal or today's heavily compressed pop. In the early days of CD, -18dB RMS was a typical mastering target for popular music. Classical was around -22dB, some pop, rock and R&B was around 16dB below full scale.
So yes, dynamics are important. Peaks of 16-18 above average level are typical in what most people here listen to.
OTOH according to NRC of Canada "90 dB (unweighted) average is very loud and considered far beyond normal listening levels"
there was an interesting thread before: SPL targets for speaker design
ps.
here are distortion measurements of commercial loudspeakers according to the NRC methodology: SoundStageNetwork.com | SoundStage.com - SoundStageNetwork.com | SoundStage.com
they measure "THD+N @ 90dB, 50Hz - 10kHz (measured @ 2m)"
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