Speakers cabinet _ knock on wood test

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Good morning to Everyone !
it is me again trying to understand something on speakers cabinet testing
I firmly believe in the knock on test on cabinet panels
It reminds me of another test usually done on another product


I absolutely believe in the usefulness of this test
wanting to do the test in a more scientific way, instead of my knuckles that also hurt, I would like to use a small hammer
a first question is about the type of hammer that can be used and above all what is the best material
metal, wood, plastic? there are hammers of very different materials

Moreover I wonder if it is possible to somehow replace the ear with an instrument that gives a sort of spectrum of the noise generated by the cabinet
I was very impressed by this video here from Wilson Audio


each material has a different resonance in an evident way
It seems that different materials are optimized for different purposes
I struggle with English but I have not understood which material is the best in the end
The only cabinet that is truly critical for me is absolutely the woofer one
I think it is really the only problem that I have left
and I think it is enormously underestimated
I tried to study the solutions used for subwoofer cabinets but I do not know which is the best and above all how it is made inside and with what materials and all the rest
I believe that the real problem in audio reproduction is the reproduction of low frequencies which are like the foundations of a building
if the foundations are not solid the whole building can collapse
if they are solid the rest he's always standing or almost
 
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I firmly believe in the knock on test on cabinet panels

Of acedemic interest only. Since the stimukus is unlike the music you play, with excitement from the outside not the inside so knock test is not something that tells you what you think. If the box rings when you strike it, and theyare at higher frequencies, that is a good thing.

dave
 
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Hi ! thank you very much for your helpful advice In the meantime i have bought a wood ball to use instead of my knuckles
i really do not know if this test is of some value i can only say that i tried a little speaker and the sound of the top side and back panel is quite different
In many cases is very boomy The frequency of the sound change and above all the volume
The idea is to have a speaker that when hit on the sides does not generate a sound of its own
or at least as little as possible
the pitch as you say must also be telling
for now i am shocked by how much a speaker cabinet can amplify the hit
i admit i have been intrigued by the Mr Wilson test and how their composite sound very different

i understand the best material for a woofer cabinet could be the one with higher pitch ?

however i guess the test could be more telling when done on a complete cabinet
 
thank a lot again now i know what to look for to find a decent bass cabinet solution that is my only real problem
a higher pitch
if i understand well a stiffer cabinet should have a higher pitch ?
so i guess that mdf is ruled out while plywood should be a much better option
I have already knocked on some plywood at the stores and the sound pitch is indeed higher in Hz
and extended bracing also very helpful as well
i should use a mic to check the spectrum probably i have one i will try to do it soon
 
I have two tests, one is the knuckle test, the other is resting my hand on a speaker whilst music plays, and feeling how much it vibrates. Someone on diyaudio suggested using an automatic center punch, this would mean that a known amount of energy is doing the test. You can also record the resulting knock, and try an find the frequencies in it. I've tried lots of different cabinets, and my best results are from very thin ply (3.4mm I think) VERY well braced.
 
Hi thank you very much I will use a usb mic i have bought then
i have also bought two wood balls to use instead of my knuckles They work quite good

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however i am quite worried by the complexity of the whole topic
not being particularly ingenious I try to look at what others do and I see very different solutions between them
if we take a small two-way speaker I see that there are speakers in different types of material and extremely different weight and properties
It is not possible that anyone is equally good
there must be an ideal solution with real solutions that are more or less close to that ideal speaker
The total absence of a sensation of boxy sound for me is now at the top of any other requirement
what is called the disappearing act
anyway if i understand well that the higher the pitch the higher the stiffness of the panel ? and that for a bass box the pitch should be high ?
i have tried the ball on a little speaker each side sounds different with the smaller one having the higher pitch
the material is aluminum with constant thickness
 
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I have two tests, one is the knuckle test, the other is resting my hand on a speaker whilst music plays, and feeling how much it vibrates. Someone on diyaudio suggested using an automatic center punch, this would mean that a known amount of energy is doing the test. You can also record the resulting knock, and try an find the frequencies in it. I've tried lots of different cabinets, and my best results are from very thin ply (3.4mm I think) VERY well braced.
Hi very interesting thank you very much
May i ask what do you intend for best results ? lack of vibration ?
things get complicated when all the drivers are mounted on the same baffle
I see high end speakers as heavy as 200kg/each
in other speakers the woofers are in different enclosures A solution i prefer also because it allows for experimenting with different options for mid and high range reproduction
 
It seems to me that tap testing sample panels would possibly best be done the way tonewoods are tap tested... you're just looking/listening for a higher pitch and a lack of ringing. For tonewoods, the piece is held between the thumb and forefinger near a corner and the center of the panel is tapped with the middle finger of the other hand. Give that a shot with whatever wood samples you have around
 
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Hi very interesting thank you very much
May i ask what do you intend for best results ? lack of vibration ?
things get complicated when all the drivers are mounted on the same baffle
I see high end speakers as heavy as 200kg/each
in other speakers the woofers are in different enclosures A solution i prefer also because it allows for experimenting with different options for mid and high range reproduction
The best results were the way they sound, very clean bass. With that example, both the bass and full range were on one cabinet, although the full range has its own chamber, and is slightly mechanically decoupled from the front baffle by a foam mounted sub baffle.
I also think that having separate boxes for bass and mid range is a good idea, it means you can experiment with different sections without making a whole new speaker, as well as the acoustic advantages.
 
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It seems to me that tap testing sample panels would possibly best be done the way tonewoods are tap tested... you're just looking/listening for a higher pitch and a lack of ringing. For tonewoods, the piece is held between the thumb and forefinger near a corner and the center of the panel is tapped with the middle finger of the other hand. Give that a shot with whatever wood samples you have around
Hi thank you very much for the very valuable advice
actually i am finding these wood balls very convenient and practical A steel ball could be too hard and damage the speaker/wood surface
it is very easy to check for cabinet damping for instance
At the cost of being annoying the only real problem to me is the box with the woofer It is the only real challenge in design and build a speaker
The midrange will have a much lower cone moving mass like less than 10 gramms and when cut above 500Hz very small displacement like 2 max 3 mm
A driver this light and this almost still will produce almost no vibrations Just making the mid tweeter cabinet a little heavy will solve ANY issue
Of course it would be fundamental to decouple mechanically this head from the body But it can be done

The very bad solution so popular is the tower speaker with all the drivers in the same box
To overcome the problems they have to be made very heavy and stiff
It is an unnecessary complication I wonder why people prefer the stairs when there is an elevator
 
The best results were the way they sound, very clean bass. With that example, both the bass and full range were on one cabinet, although the full range has its own chamber, and is slightly mechanically decoupled from the front baffle by a foam mounted sub baffle.
I also think that having separate boxes for bass and mid range is a good idea, it means you can experiment with different sections without making a whole new speaker, as well as the acoustic advantages.
Hi thank you very much for your kind and valuable advice This is exactly what i am trying to achieve
when the bass solution is found it will be like a corner stone of a building I will keep it as long as i will listen in the same room
I have looked at many three ways with 10-12" woofer The woofer is cut at 80 to 1100 Hz depending on the speaker model
It is a big difference indeed Many JBL studio monitors use to the woofer up to 1 kHz
This is my other obsession The frequency cut between woofer and mid Another very important issue
 
The worst shape you can use is a six-sided box. Try to think of shapes which are more rigid.

Harder to make the joints strong if they are not right angles. Right angles make optimum use of fasteners, and allow much easier clamping and weighting (needed to make the glue strong). It would take special custom tooling to clamp a box together if not rectangular cross section.
 
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See here:
 
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