Like paper there are a zillion kinds. Depends on the plastic.
There are metals that aren’t stable as well.
Execution counts.
dave
Yes it's true. ABS with fiberglass in it is almost as stable as steel.
There are good and bad plastics.
There are good and bad plastics.
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hi i thank you All heartedly for all your kind and very valuable inputs
i just want to make two comments
some says that a heavy box "stores" energy
like this stored energy can be given back
i would use dissipates energy
if i understand well lead transforms vibrations in heat and waste it not store it
Moreover what is the benefits to use a very stiff cabinet that does not store energy and then use a very inefficient driver like in the celestion sl600? they need a lot of power to come alive
Moreover celestion has built two soundstage champions one very light the sl600 and one very heavy the Kingston almost 5 times the sl600 weight
inho it would be much easier to make a very heavy cabinet than one very stiff
for a very stiff cabinet exotic materials are usually needed Out of the reach for many DIYers
i conclude saying that if i had a pair of sl600 i would look to replace the woofers ASAP
i am sure they hold back the performance of the speaker
i just want to make two comments
some says that a heavy box "stores" energy
like this stored energy can be given back
i would use dissipates energy
if i understand well lead transforms vibrations in heat and waste it not store it
Moreover what is the benefits to use a very stiff cabinet that does not store energy and then use a very inefficient driver like in the celestion sl600? they need a lot of power to come alive
Moreover celestion has built two soundstage champions one very light the sl600 and one very heavy the Kingston almost 5 times the sl600 weight
inho it would be much easier to make a very heavy cabinet than one very stiff
for a very stiff cabinet exotic materials are usually needed Out of the reach for many DIYers
i conclude saying that if i had a pair of sl600 i would look to replace the woofers ASAP
i am sure they hold back the performance of the speaker
Mass and stiffness store energy that can be given back.
Resistance dissipates energy as heat (damping).
Resistance dissipates energy as heat (damping).
lead dampens for sure and also has big mass No stiffness at all by the way
however i guess that the spectral decay test says it all about the dynamic behaviour of a speaker
however i guess that the spectral decay test says it all about the dynamic behaviour of a speaker
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My understanding from reading here and ASR is that damping = dissipating sound through heat / friction
So more mass or density doesn't necessarily mean more damping.
Lead has some stiffness, (everything does) but obviously not much for a metal.
CSD is a pretty informative plot if you are looking for cabinet resonances, definitely.
So more mass or density doesn't necessarily mean more damping.
Lead has some stiffness, (everything does) but obviously not much for a metal.
CSD is a pretty informative plot if you are looking for cabinet resonances, definitely.
One solution is to mount the drivers in small boxes, that are inside, but mechanically isolated (by springs and foam) from the main, outer enclosure. This works for both the mechanical vibration that is a result from the reaction forces from the driver, and the sound radiated from the rear of the cone.
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hi thank you for the very kind and helpful advice
the nice thing of CSD on the whole speaker is that will describe the mechanical behaviour of the all system drivers plus cabinet
OT i have seen somewhere the CSD of old Infinity drivers Emim and Emit
i am not an expert but i got the feeling that they were very close to the state of the art
no tails to speak of Astonishing performance indeed
unfortunately they have stopped their production
they must be very clean sounding
by the way i don't know anything about their distortion
In does in that it lowers resonance to below a speaker's passband, ergo nothing strong enough to excite it.
this is a little of topic ... i have always been intrigued by this driver
https://i.ebayimg.com/images/g/Yx0AAOSwTwZfyATV/s-l500.jpg
look how wide is the basket edge around the cone 😳
This imho must be very good indeed Because it allows for a more solid mechanical connection with the front baffle (larger contact area)
https://i.ebayimg.com/images/g/Yx0AAOSwTwZfyATV/s-l500.jpg
look how wide is the basket edge around the cone 😳
This imho must be very good indeed Because it allows for a more solid mechanical connection with the front baffle (larger contact area)
Found on a swedish forum:
1. Sandwich damping. Design loss factor (eta) via shear in the loss layer around 0.2, i.e. around 10 times higher than in an undamped MDF construction. This alone gives a reduction of 10 dB (broadband) for structure-radiated sound.
2. Stiffeners (and to a lesser extent thickness increase). Higher fundamental resonance frequency leads to fewer excited modes and thus a lower overall level of the structure-radiated sound. Here, however, there are also disadvantages in the form of a higher so-called radiation factor* due to higher bending wave speed and longer streaks.
The excitation also shifts more and more to the area type (vs. point ditto) as the frequency increases and the bending wavelength thus decreases, which lowers the structural radiation.
3. Mass increase. In practice, a sandwich construction usually gives rise to thicker walls, which also results in an increase in mass and an even lower level.
As a small digression, it can be added that the parameters one has to play with in all structural acoustic problems are mass, stiffness, losses and radiation factor. An increase in the first three gives lower radiation, an increase in the last one gives higher. The ideal structure in this regard is heavy, stiff and "tough" at the same time!
It should be noted that there are already almost completely safe solutions for eliminating the risk of audible structure-radiated sound from a speaker box. 12 mm MDF / 0.5-1 mm damping glue / 12 mm MDF in combination with as many stiffeners (made of wood or plywood, concentrated in the area around the base/intermediate element(s)) as you can handle gives guaranteed overkill in this area.
I've rambled on about this many times before, but the DIYer shouldn't bother with home woven dampening devices, crates within crates, concrete structures, or some all-welded steel monstrosity, but should work engineer-wise instead. Less work, reasonable total weight and impeccable performance. What more could you want? Even worse, boxes within boxes, attempts at vibration isolation and artificial damping arrangements can provide minimal acoustic benefits and, in the worst case, even direct disadvantages compared to the simplest pure MDF box.
1. Sandwich damping. Design loss factor (eta) via shear in the loss layer around 0.2, i.e. around 10 times higher than in an undamped MDF construction. This alone gives a reduction of 10 dB (broadband) for structure-radiated sound.
2. Stiffeners (and to a lesser extent thickness increase). Higher fundamental resonance frequency leads to fewer excited modes and thus a lower overall level of the structure-radiated sound. Here, however, there are also disadvantages in the form of a higher so-called radiation factor* due to higher bending wave speed and longer streaks.
The excitation also shifts more and more to the area type (vs. point ditto) as the frequency increases and the bending wavelength thus decreases, which lowers the structural radiation.
3. Mass increase. In practice, a sandwich construction usually gives rise to thicker walls, which also results in an increase in mass and an even lower level.
As a small digression, it can be added that the parameters one has to play with in all structural acoustic problems are mass, stiffness, losses and radiation factor. An increase in the first three gives lower radiation, an increase in the last one gives higher. The ideal structure in this regard is heavy, stiff and "tough" at the same time!
It should be noted that there are already almost completely safe solutions for eliminating the risk of audible structure-radiated sound from a speaker box. 12 mm MDF / 0.5-1 mm damping glue / 12 mm MDF in combination with as many stiffeners (made of wood or plywood, concentrated in the area around the base/intermediate element(s)) as you can handle gives guaranteed overkill in this area.
I've rambled on about this many times before, but the DIYer shouldn't bother with home woven dampening devices, crates within crates, concrete structures, or some all-welded steel monstrosity, but should work engineer-wise instead. Less work, reasonable total weight and impeccable performance. What more could you want? Even worse, boxes within boxes, attempts at vibration isolation and artificial damping arrangements can provide minimal acoustic benefits and, in the worst case, even direct disadvantages compared to the simplest pure MDF box.
it seems to me that this thread (also for my fault and please excuse me for this) has drifted from the original topic of cabinet material measurements to cabinet design and construction
I think that it would be very useful to go back to the topic in order to select the best instrumental methods to assess if a speaker cabinet is good or not
At Stereophile magazine, for instance, they routinely carry out this test here below
https://www.stereophile.com/images/archivesart/rokantfig2.jpg
is this what we have to look for ? no ripples ?
Speaking of resonances i have already made my suggestion of using a carillon mechanism placed directly on the various sides of the cabinets
The louder the sound the more resonant the cabinet
I conclude saying that if a non resonant cabinet is the ultimate goal why on earth we still going on comparing speaker cabinets and musical instruments ?
are not like comparing apples and oranges ? they are two objects designed and built for completely different purposes The comparison could be even misleading
If someone builds a speaker cabinet acting like a musical instrument is his/her problem
For sure it will be never an accurate speaker
P.S. another case where different sides of the same cabinets behave differently
https://www.stereophile.com/content/bw-nautilus-801-loudspeaker-measurements
I think that it would be very useful to go back to the topic in order to select the best instrumental methods to assess if a speaker cabinet is good or not
At Stereophile magazine, for instance, they routinely carry out this test here below
Here one result
https://www.stereophile.com/images/archivesart/rokantfig2.jpg
is this what we have to look for ? no ripples ?
Speaking of resonances i have already made my suggestion of using a carillon mechanism placed directly on the various sides of the cabinets
The louder the sound the more resonant the cabinet
I conclude saying that if a non resonant cabinet is the ultimate goal why on earth we still going on comparing speaker cabinets and musical instruments ?
are not like comparing apples and oranges ? they are two objects designed and built for completely different purposes The comparison could be even misleading
If someone builds a speaker cabinet acting like a musical instrument is his/her problem
For sure it will be never an accurate speaker
P.S. another case where different sides of the same cabinets behave differently
https://www.stereophile.com/content/bw-nautilus-801-loudspeaker-measurements
Large Advent woofer, they found some really cheap baskets and ‘fixed” them to accomodate the smaller cone.
dave
Someone in a previous thread suggested using an automatic centre punch, you could use it in the same way as the music box mechanism, a single impulse would be an interesting to compare against the multiple tones. Perhaps just blutac a tiny bit of wood to the speaker so you don't end up with lots of dimples...
thank you for the valuable advice I asked because it looks quite different from the others and the unusually wider edge caught my attention
usually when i see something different i wonder why they do so while all the others don't
