You can use cellophane! Or a robust fabric...it will act like a big passive radiator with bandwidth & resonance defined by the tension.
I have to admit that I use whatever things I have under sight, and my last subwoofer use a 8mm MDF/cardboard for the first part of the box, the one holding the woofer. Though that if I find some 1 mm lead sheet and...
The mind wanders, I just imagined a sub fitted to a gym ball!
Hi sorry it's me again but I have really to know your opinion
I still think that the only nasty vibes can come from the front baffle
And trivially speaking the lower the Hz and the higher the Spl the more the vibes
I was thinking of sticking with biadesive tape a small mirror to the front baffle
Hit the mirror with a laser pen beam with an angle and find the reflected beam at some distance from the speaker
Then excite the woofer with a strong low Hz signal and see if the reflected point moves
If it stays still this will mean that the front baffle doesn't flinch
Is this a stupid test?
I would be happy to hear your opinion
Thank you very much indeed
I still think that the only nasty vibes can come from the front baffle
And trivially speaking the lower the Hz and the higher the Spl the more the vibes
I was thinking of sticking with biadesive tape a small mirror to the front baffle
Hit the mirror with a laser pen beam with an angle and find the reflected beam at some distance from the speaker
Then excite the woofer with a strong low Hz signal and see if the reflected point moves
If it stays still this will mean that the front baffle doesn't flinch
Is this a stupid test?
I would be happy to hear your opinion
Thank you very much indeed
Your test would give you no idea how any vibrations you measured affect the frequency or impulse response of the cabinet.
Stupid means not having, or showing a great lack of intelligence or common sense.
Without knowing what you want to determine from your test, can't determine whether it is stupid.
As could be determined with the touch of a finger, your test would certainly tell you that vibrations will increase with amplitude, and could tell you the most resonant frequency at the particular placement location of the mirror, assuming the bi-adhesive tape and mirror didn't change that particular resonance peak, which they would to some extent.
MalVeauX did some accelerometer testing which conclusively proved that dual opposed subwoofers reduced cabinet vibrations by a great amount compared to using one of those drivers as a passive radiator:
Measurements (Vibration Tests, Videos)
Now that all the typical stuff is out of the way, I wanted to explore what the dual opposed afforded me in this design. The idea was that it should cancel cabinet vibrations. I wanted to test this with an accelerometer and also just practical tests like a glass of water.
I'm using a WitMotion accelerometer sensor and associated software to gather data on acceleration, angular velocity, etc. I attached it with blu-tac.
First, I measured single driver so that the other driver was merely passive, this means I do not benefit...
Now that all the typical stuff is out of the way, I wanted to explore what the dual opposed afforded me in this design. The idea was that it should cancel cabinet vibrations. I wanted to test this with an accelerometer and also just practical tests like a glass of water.
I'm using a WitMotion accelerometer sensor and associated software to gather data on acceleration, angular velocity, etc. I attached it with blu-tac.
First, I measured single driver so that the other driver was merely passive, this means I do not benefit...
That said, his test didn't compare frequency and impulse response of two woofer cabinets with the same enclosed volume, one dual opposed and another with both drivers on the same side or to determine what actual sonic effects cabinet vibrations may impart.
Hi my main goal would be to see any displacement of the front baffle
I guess that in the best case it should not move back and forth when the woofer is excited with strong signals
How any front baffle movement can affect the sound is a mystery to me
Maybe this is more impacting the sound when some domes are mounted on the same baffle
If I had a 2 ways speaker I would mount the tweeter in a separate enclosure mechanically decoupled by the woofer cabinet
Thank you for the very valuable link
While the benefits of the solution are evident I can't help but notice that high quality commercial subs like Reals for instance don't adopt it
I so much prefer front firing woofers even if I can't tell why
I would even load the woofer with a horn to direct all the pressure towards the listening position
I guess that in the best case it should not move back and forth when the woofer is excited with strong signals
How any front baffle movement can affect the sound is a mystery to me
Maybe this is more impacting the sound when some domes are mounted on the same baffle
If I had a 2 ways speaker I would mount the tweeter in a separate enclosure mechanically decoupled by the woofer cabinet
Thank you for the very valuable link
While the benefits of the solution are evident I can't help but notice that high quality commercial subs like Reals for instance don't adopt it
I so much prefer front firing woofers even if I can't tell why
I would even load the woofer with a horn to direct all the pressure towards the listening position
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The movement of the baffle (and any other moving part of the enclosure) can vary in from in phase to out of phase with the woofer's movement.
In phase, it's contribution could slightly increase SPL, out of phase, slightly decrease.
If you were to compare the movement (displacement) of both you will notice that the baffle moves only a tiny amount by comparison, perhaps 0.1mm when the driver moves 10mm.
With a 100/1 ratio like that, it would take precise measurements to detect any difference in frequency response, which would at most be under 1/4dB, a fraction of the deviation in response of the best drivers available.
If the cabinet is well constructed, the sonic contribution of vibration is negligible.
Hi thank you very much for the very valuable advice
But only 0.1 mm is nothing indeed I was thinking much more
Does the same apply also to dome drivers that fwiu they move very little ?
I with a friend did an experiment with this speaker actually on the pair
we played some pipe organ tracks with powerful low Hz notes
Then we added lead sheets internally to the sides The resulting weight was about 20kg/each
we played again the same tracks The sound was so much better
much more out of the box more powerful defined better 3d effect
better in all aspects
Now the question
Is it possible that the vibrations of the unweighted cabinet have dirtied the tweeter's output, introducing distortions?
because if that were the case, even just removing the tweeter from the box and isolating it from the bass could give a similar improvement
without the need to use toxic lead
But only 0.1 mm is nothing indeed I was thinking much more
Does the same apply also to dome drivers that fwiu they move very little ?
I with a friend did an experiment with this speaker actually on the pair
we played some pipe organ tracks with powerful low Hz notes
Then we added lead sheets internally to the sides The resulting weight was about 20kg/each
we played again the same tracks The sound was so much better
much more out of the box more powerful defined better 3d effect
better in all aspects
Now the question
Is it possible that the vibrations of the unweighted cabinet have dirtied the tweeter's output, introducing distortions?
because if that were the case, even just removing the tweeter from the box and isolating it from the bass could give a similar improvement
without the need to use toxic lead
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i have found an old thread about tweeter excursion
i think that in a not properly designed cabinet if i mount a powerful woofer and a tweeter on the same baffle the vibrations induced by the woofer on the baffle can smear the tweeter response ?
and this could happen expecially in the tweeter lower range where it has more excursion Like at 2kHz
i have seen a two ways with the high freq driver mounted on a column completely separated from the bass cabinet
i think that in a not properly designed cabinet if i mount a powerful woofer and a tweeter on the same baffle the vibrations induced by the woofer on the baffle can smear the tweeter response ?
and this could happen expecially in the tweeter lower range where it has more excursion Like at 2kHz
i have seen a two ways with the high freq driver mounted on a column completely separated from the bass cabinet
Hi just to sum up
Any front baffle displacement caused by the woofer movement will not impact the woofer response
And this means for instance that design and build a subwoofer cabinet will not be that challenging
Have I got it right?
The situation could be different for dome drivers where the dome excursion is minimal and even small front baffle vibrations could smear the dome response and cause distortion
Right?
Any front baffle displacement caused by the woofer movement will not impact the woofer response
And this means for instance that design and build a subwoofer cabinet will not be that challenging
Have I got it right?
The situation could be different for dome drivers where the dome excursion is minimal and even small front baffle vibrations could smear the dome response and cause distortion
Right?
A floppy cabinet construction can impact it's sound, but those impacts are minimal for reasonably stiff enclosures.
I doubt the cabinet vibrations in a reasonably stiff enclosure would cause audible smearing or distortion in the dome tweeter. It is possible large movements (which wouldn't occur on the cabinet in #227 with or without lead lining) could cause Doppler distortion, but the Doppler distortion always present in the woofer when low frequencies modulate high frequencies would be orders of magnitude greater than in the tweeter, and lead lining would have no effect on those.
Your experiment with 20KG of lead lining would have reduced the cabinet's enclosed volume by almost 2 liters, which would raise it's resonant frequency, changing it's response, and reduce the woofer's excursion at a given drive level. Lead in close proximity to the crossover coils would change their inductance, also affecting frequency response.
Depending on the nature of that distortion, it might be objectionable.
Subwoofers driven to Xmax, the so-called linear range of excursion have 10% harmonic distortion.
Most don't notice that level of HD unless under controlled A/B conditions with sources lacking harmonics, like pure sine waves.
That said, amplitude modulation of high frequency signals by low frequencies when driven past Xmax can be quite noticeable, as lack of definition, gargling vocals, etc. and a good reason to limit the excursion of drivers that cover a wide range of frequencies, like the woofers in Ginetto61's cabinets.
Pipe organs may have strong response down in the 16Hz range, if a subwoofer was handling the lower octaves, the woofer would be unaffected by it's excursion, even if the subwoofer was driven beyond Xmax.
thank you very much again For any work on cabinets i will have to rely on a professional worker
since I am a beginner in the sense that I have read a lot but done little, the idea would be, considering how important it is to obtain a rigid cabinet, to start from an existing box and stiffen it
I do not want to use lead anymore which is toxic and is everything but stiff (by the way the cabinets now are very very dead)
I would like to use metal elements to be fixed internally to the panel Metals are so much more stiff than any wood And they are heavy too
Moreover I do not understand why almost no one builds metal frames on which to then fix the various panels Actually Magico did it for the Q1
I saw a model by Sonus Faber where the side panels were attached to the supporting wood structure even by magnets
This guarantees exceptional accessibility to the internal components for maintenance or upgrades
I bought a cheap endoscope I have to check where my friend has fixed the lead sheets I would like to cut a big opening on the back or the bottom for an easy access to the internals
The cabinets will work as test bench for some experiments
I have to study how make the lead less dangerous Maybe sealing it with some paint
Thank you very much again
P.S. 20kg is the total weight of the speaker after loading it with lead
The original weight was around 12 kg i read
No, but the driver's strong pressure waves + baffle, etc., eigenmodes sure will.
Weight and stiffness are independent properties.
Thick plywood is much stiffer than thin metal.
Almost no one prefers to use more expensive internal cabinet construction methods that don't yield positive sonic results.
So you reduced the enclosure volume by around one liter instead of two...
Thanks a lot Then i have to study how to design bracing I wonder if there are any guideline
To be honest if i were a welder i would do it with these
like in the old racing car The frame was in welded metal
then the sides could be of cardboard plastic thin wood almost anything Aside bottom panel and front baffle of course
This is off topic Sometimes i read some mags lab reports of measurements of panels vibrations on loudspeakers cabinets
the measure usually the side or top panels I cant read well but the feeling is that these vibrations are extremely low in level
I cant see how they could disturb the front emission
moreover to reach the listener they have to be reflected by some surface and so the level goes down even more
imho the only emission that matters is the direct one
speaking of subs if the solution of two woofers firing in opposite directions were the only good all subs would be like that
i prefer to face the drivers always
i see But what i love is the idea of sides that can be removed very easily to access the internals This is wonderful just some bolts and voila
honestly i did not think about that It could be The only think that stops me to use lead slabs everywhere is its toxicity
it is a wonderful material to tame vibrations Wonderful and cheap
no need of very expensive high tech composites of secret formula
You could always get a blowtorch (or two) and silver solder it. But building a steel frame would add stiffness exactly where it already has stiffness - at the 90 deg joints.
imho there is just one panel that really matters The front baffle There is a reason why many manufacturers make it very thick Even 2"
But the idea would be to bolt the woofer directly to the rigid metallic frame and use the panels just to seal the cabinet
the metallic chassis would become the woofer basket No i will not weld the woofer to the frame
It is exactly like in old racing car with a metallic chassis
The engine (i.e. the woofer) was fixed to the frame not to the bodywork which was only supported by the chassis
it had no structural function only aerodynamic
but a speaker does not travel at 300 km/h
the side could be kept in place just with some magnets
The access to the inside of the speaker would be a pleasure
But the idea would be to bolt the woofer directly to the rigid metallic frame and use the panels just to seal the cabinet
the metallic chassis would become the woofer basket No i will not weld the woofer to the frame
It is exactly like in old racing car with a metallic chassis
The engine (i.e. the woofer) was fixed to the frame not to the bodywork which was only supported by the chassis
it had no structural function only aerodynamic
but a speaker does not travel at 300 km/h
the side could be kept in place just with some magnets
The access to the inside of the speaker would be a pleasure
A cube and a sphere of the same volume would have a similar resonant frequency.
I actually considered using a sewer pipe at one point. A few friends of mine, work in construction, and sometimes have a piece left after a job. They are seriously strong and solid. So a glued in thick wooden panel in each end, and you would have a bit of unique look, with that color and ribbed shape 😀
