@kemmler3D
I hear you on too thick a layer of CLD, but I'm not as convinced about it being similar to sand.
I also hear you on the need for both stiffness and damping, not to compromise either too much, however I'd note that unless the panel moves, damping doesn't happen. Damping can therefore fill in the gaps but where does the compromise lie? Some cabinets as mentioned above are quite flexible but well damped.
I can't answer as to the fluid filled but I note that as it is not attached to the insides of the walls, it won't necessarily damp with every movement, it may simply redistribute under some movement conditions.
I hear you on too thick a layer of CLD, but I'm not as convinced about it being similar to sand.
I also hear you on the need for both stiffness and damping, not to compromise either too much, however I'd note that unless the panel moves, damping doesn't happen. Damping can therefore fill in the gaps but where does the compromise lie? Some cabinets as mentioned above are quite flexible but well damped.
I can't answer as to the fluid filled but I note that as it is not attached to the insides of the walls, it won't necessarily damp with every movement, it may simply redistribute under some movement conditions.
A comp i did from another German study (modestly braced MDF vrs plywood (quality unknown).
Based on the math in the basic science the likelihood of causing a resonance to express the higher in frequency the (potential) resonance is the less likely there will be the energy to excite it.
Further, if the Q of the potential resonance is high (frequency too), it is even less likely that sufficient sustained HF energy to excite the resonance.
I am guessing this came from the same or similar. Found it when looking for the above)
View attachment 1116018
dave
Seems to me the actual measured data contradicts that "relative likelihood" graph. May own measurements directly contradict it also. I don't know what physics was used to make that graph, but it is so over-simplified, I don't think it is useful. The opposite in fact, in that it leads people to believe they can simply stiffen their wood boxes and all problems will be solved.
Regarding the comments on Q changes from damping, don't forget the other important part: the actual amplitude. If you can drop a resonance 10-20dB with panel damping, it will not matter if the Q is lower and the resonance broader. Lowering Q being bad is only relevant if the amplitude was not also dropped at the same time.
The measurements are not music. Those panels are purposely excited as much as possible to expose all resonances.
The higher initial F0 of the multiply is the figure of merit. Then push it up from there.
Too bad the initial data was not burst decay (waterfall with periods as the time axis), so that we could compare the Q of the resonances.
dave
The higher initial F0 of the multiply is the figure of merit. Then push it up from there.
Too bad the initial data was not burst decay (waterfall with periods as the time axis), so that we could compare the Q of the resonances.
dave
I would like to see an actual measurement of a single example of typical wood construction where the primary resonances have been pushed above the passband of the mid. I don't believe it is possible, and the tests that have been done using typical materials (as in this thread) lead me to believe I'm correct. I'd love to be wrong because it would make design easier, but...
Last edited:
You don't really believe a lower Q resonance that is also 15dB lower than the higher Q resonance is worse do you? 15dB is A LOT of power. And I use 15dB because that is what CLD methods can get you over solid boxes (at least).
You don’t have to get that far, just high enuff that they is likely to ever be sufficient to get the “potential” resonance going. Under most conditions as if if was not there.
Elegance vrs Brute Force.
dave
Certainly works if done right, i will not argue with that, i sorta do that with the sides of the full-on miniOnkens.
But how much work is it? Worth the effort. Like comparing an amplifier with a “damping factor” of 400 to one with one of a 100.
dave
"likely" is doing a lot of work there. Again, I would rather see a single actual measurement proving this than more speculation.
CLD is all about elegance. My first examples used 1/4" MDF bonded together, for a nominal thickness 1/2"! Others in this thread are talking about 2" thick cabinets 😵
It's not too much. You lay one sheet down and spread your polyurethane adhesive with a tile adhesive spreader so that it's even. Place the other piece on top, squish it lightly and weigh it down, but don't clamp it tight because you want to retain a little thickness to the adhesive.
Me neither, hence my lossy/mass loading to shift it lower.
Can you 3D print rubber? Imagine if you 3D printed a plastic honeycomb enclosure, but the printer filled the honeycomb cavities with rubber to damp the thing.
Surely not using dissimilar thickness skins as most seem to do (not implying your good self!) is missing as trick - identical thicknesses place the damping material on the neutral axis where displacement is at its lowest.
Agreed, however the slow transient decay of the stored energy is also a time-smeared mess.
Hi my point was that imho the cabinet construction clearly becomes more critical the more we go down in Hz and up in SPLs
The Rogers do not go lower than 100Hz with decent SPL ... they are not full range speakers
They should have used a sub even in the van with the Rogers
That is the reason why i would keep separated in a dedicated cabinet the big woofer from the other drivers
The beasts should be kept in a cage
i agree completely
this material looks quite impressive
https://b2b.karlpichler.it/it/DELIGNIT-PANZERHOLZ-B15-ANTISFONDAMENTO-40mm-213X100cm/22702-001
56 kg/m2
it looks like the perfect wood ? stiff and dampened The wood version of the bulletproof glass ?
https://b2b.karlpichler.it/it/DELIGNIT-PANZERHOLZ-B15-ANTISFONDAMENTO-40mm-213X100cm/22702-001
56 kg/m2
it looks like the perfect wood ? stiff and dampened The wood version of the bulletproof glass ?
Yes, I doubt anybody here would disagree -can't beat the laws of physics. 😉
Agreed: they aren't, because they weren't designed to be. Although they actually get lower than the original design requirements & specification (see below)
On that I'll (respectfully) disagree. The design remit for the LS3/5 prototypes & the LS3/5a is set out in the introduction to the original paper (BBC RD 1976/29). Quoting verbatim:
There is a need to monitor sound programme quality in circumstances where space is at a premium and where headphones are not considered satisfactory. Such circumstances include the production-control section of a television mobile control-room, where the producer responsible for the overall production of the programme needs to monitor the output from the sound mixer but at levels lower than those used for mixing. Thus a small monitoring loudspeaker is required and, as no adequate commercial device was available, one was designed by BBC Research Department. The design is based on an experimental loudspeaker developed during the preliminary work on acoustic scaling described elsewhere in which a small loudspeaker was needed to cover the frequency range from 400 Hz to about 20kHz. When the characteristics of the loudspeaker were measured it was found that, despite the small size cabinet, the axial response/frequency characteristic was substantially uniform down to 100 Hz and that excellent sound quality was obtained with programme input.
Sub-bass was not part of the bandwidth specification for low-level [primarily television speech] monitoring in mobile broadcast control vans (& their fixed equivalents). There is no sub-bass content in the material such production control rooms (mobile or fixed) were expected to handle on a regular or even semi-regular basis. For that, the larger setups were used. Remember, we're talking 1970s & '80s era BBC television here -mostly things like regional news shows, on-site reporting / broadcasts and specialist segments (such as anchoring the daily early-evening children's show period, the studio for which was described as 'the broom cupboard' due to its miniscule size) & the like.
Last edited:
The panels primarily resonate. Louder music makes the same amount louder from the panel... so normally you don't need to brace more just because you want to listen louder.
Thanks for the kind and valuable explanation and i promise the last one on the Rogers
What I fail to understand is how a loudspeaker born for a specific purpose is used and praised by many enthusiasts who never recognize its evident limits of range and dynamics How can you listen to a rock concert but also symphonic or jazz music with the presence of bass and piano with the Rogers without completely missing the low frequencies ? and the bigger the room is the bigger the loss of course
a friend of mine had actually built two subs to put underneath each speaker and when I heard the Rogers with them the difference was abysmal
Finally the sound was really complete and satisfactory
Last edited:
I see thanks But there is another point that i dont understand
From what i get here the cabinet dampening effect takes out some energy from the drivers ? so a very stiff and not dampening cabinet is needed to allow that all the energy emitted by the driver is transferred to the listener through the air
But the cabinet mast have also a very high mass to counteract the forces generated when the cone moves back and forth
therefore the optimum material cannot be MDF that absorb also part of the energy from the drivers
I see only metals as possible candidates
https://www.researchgate.net/profil...74@1536630777562/2-Sample-Stiffness-Table.png
i can see that steel for instance is very stiff and very high density
Al second best
Wood is so much less stiff and so it will absorb some energy from the driver Sub optimal i mean