This dense paper roll doesn't ring like MDFs or plywood. It seems to have very good acoustic properties. Too bad it didn't come in sheets. But then if it did I'm not sure how I would go about cutting it. The standard method is on a lathe cutting machine with a circular razor wheel that gradually slices through as it turns at high speed. Ive tried the usual methods, saws aren't very effective. Its difficult to cut cleanly that way and it also starts to burn. Im in the process of making 5 inch subs, but its great for mid range cups too. I might try making a 2 or 3 way with it housing one driver per tube. The other available size is 3" inner diam. that could house the HF's.
Attachments
Thank-you. You've got me laughing. Hahaha
A dose of humour at just the right time, to break the tension. Will help us all live a bit longer.
Hi all,
I've been reading on and off in this thread and have found it to be very interesting & informative. Doing a bit of internet search today I found this thread which appears to have much information about damping factors & transmissibility of many different materials.
damping factor values : damping factors
I didn't notice it mentioned here already ... ?
Cheers,
Jesper
I've been reading on and off in this thread and have found it to be very interesting & informative. Doing a bit of internet search today I found this thread which appears to have much information about damping factors & transmissibility of many different materials.
damping factor values : damping factors
I didn't notice it mentioned here already ... ?
Cheers,
Jesper
Accelerometer measurements - how?
Hi All,
I hope this thread is still somewhat alive as I have found it to be very interesting ..
Being interested in learning more about cabinet material resonances I've now bought an accelerometer, the ADXL001 from Analog Devices - link here:
ADXL001 Datasheet and Product Info | Analog Devices ...
suggestion courtesy diyaudio member jcx.
that I would like to use to measure cabinet resonances. To this end I'm looking for a feasible software that will allow me to visualize the relevant data that are useful in relation to measuring resonance measurements. I'm thinking that real-time measurements are relevant as well as some plots indicating the decay & change of resonances over time (some waterfall plots?) ...
However, this is not a field I'm much familiar with so I'd appreciate ideas & suggestions from you ....
Cheers & thanks
Jesper
Hi All,
I hope this thread is still somewhat alive as I have found it to be very interesting ..
Being interested in learning more about cabinet material resonances I've now bought an accelerometer, the ADXL001 from Analog Devices - link here:
ADXL001 Datasheet and Product Info | Analog Devices ...
suggestion courtesy diyaudio member jcx.
that I would like to use to measure cabinet resonances. To this end I'm looking for a feasible software that will allow me to visualize the relevant data that are useful in relation to measuring resonance measurements. I'm thinking that real-time measurements are relevant as well as some plots indicating the decay & change of resonances over time (some waterfall plots?) ...
However, this is not a field I'm much familiar with so I'd appreciate ideas & suggestions from you ....
Cheers & thanks
Jesper
One caution here. There is not a one to one relationship between panel vibrations and sound radiated. It is extremely complex depending on the radiation efficiency of particular modes. Some modes will be highly efficient but others not at all. One can be sure that reducing the vibrations to zero will be effective, but if some go up and others go down then no conclusions can be drawn. and one never knows when a lower threshold has been reached (below which the sound is simply masked and cannot be heard.) And, one has to look at magnitude and phase at all points on every panel in order to conclude anything at all. Looking at the vibrations at a single point probably doesn't mean much at all.
I have tried to measure cabinet radiation but in every case, the levels are swamped out by the direct radiation of the driver itself. I have never been able to isolate cabinet vibrations from driver vibrations.
One guy around here did a study using software to find the sound radiated from an enclosure from a laser scan of the surface. In this study he found that only the back panel was significant as a radiator, the other panels were insignificant. Good to know.
I have tried to measure cabinet radiation but in every case, the levels are swamped out by the direct radiation of the driver itself. I have never been able to isolate cabinet vibrations from driver vibrations.
One guy around here did a study using software to find the sound radiated from an enclosure from a laser scan of the surface. In this study he found that only the back panel was significant as a radiator, the other panels were insignificant. Good to know.
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Hi Earl,
Thanks for your feedback. As it is I'm currently most interested in looking at resonances of various materials just to get an idea about how they behave. They are not part of a loudspeaker enclosure as such but are "isolated materials".
I don't right now remember if it was in this thread that I saw a link to a comparison between aluminum and Panzerholz's resonance behavior but it was quite interesting to me - I'd like to investigate a couple of materials myself in this manner - the link to the comparison is here:
https://www.lessloss.com/page.html?id=80
Any chance you know of a software that may help display this?
Cheers,
Jesper
Thanks for your feedback. As it is I'm currently most interested in looking at resonances of various materials just to get an idea about how they behave. They are not part of a loudspeaker enclosure as such but are "isolated materials".
I don't right now remember if it was in this thread that I saw a link to a comparison between aluminum and Panzerholz's resonance behavior but it was quite interesting to me - I'd like to investigate a couple of materials myself in this manner - the link to the comparison is here:
https://www.lessloss.com/page.html?id=80
Any chance you know of a software that may help display this?
Cheers,
Jesper
You are looking for the internal damping of the material? That's a factor, but IMO it is not that important. I design in structural damping which just looking at the materials will not show. For example, just looking at the material will not show you how effective Constrained Layer Damping is or how well a damped cross brace works. In my experience it is the total enclosure damping that matters. Damped materials help, but design is the most important thing.
A look at how well some glues are damped would be interesting since I developed a special glue just for its damping, but I never did any testing on it.
A look at how well some glues are damped would be interesting since I developed a special glue just for its damping, but I never did any testing on it.
Hi Earl - thanks again for your feedback ;-)
I've been reading into this thread and also having taken a look at some of the measurements I linked to in #523 I am "intuitively" aware of this, although I haven't yet tested it out in practice. This is what is to come now - to a sensible/"clarifying the basics" extent - with measurements made on some glue composites and pure materials.
In my context both weight and local damping will be very important (headphones) and so an interaction between adhesives (e.g. in a constrained layer context or a glue as a local vibration "absorber") and the adhesives themselves (for very local damping) is interesting to me.
Currently I'm quite impressed with Panzerholz from a knuck-test point of view (have some ~ 10 mm & 5 mm samples), however, the 5 mm samples are not mechanically stable, they bend, and so I cannot use them. And it also appears to change its resonance behavior when getting thinner (probably not surprising but nevertheless quite obvious when knuck-testing the two thicknesses).
In terms of glues I imagine some kind of epoxy glue with tungsten powder to add (very local) mass - or maybe a thick shellac mixture again with e.g. tungsten powder to add (local) mass. Possibly also two thin layers of different glues/composite masses so as to have slightly different damping qualities of the different materials while maintaining a low mass. Don't know if this is effective, though, but I reckon a measurement may give some information about this.
Any chance you can say just a bit about how your glue is made (I of course fully respect any reservation you may have here). If possible/ok with you - and in case it proves feasible in my context - I may also be interested in buying just a bit from you, in a first round for testing.
And then again I hope someone here may suggest a software that I can use for measurements ... and is straightforward to use
Cheers,
Jesper
I've been reading into this thread and also having taken a look at some of the measurements I linked to in #523 I am "intuitively" aware of this, although I haven't yet tested it out in practice. This is what is to come now - to a sensible/"clarifying the basics" extent - with measurements made on some glue composites and pure materials.
In my context both weight and local damping will be very important (headphones) and so an interaction between adhesives (e.g. in a constrained layer context or a glue as a local vibration "absorber") and the adhesives themselves (for very local damping) is interesting to me.
Currently I'm quite impressed with Panzerholz from a knuck-test point of view (have some ~ 10 mm & 5 mm samples), however, the 5 mm samples are not mechanically stable, they bend, and so I cannot use them. And it also appears to change its resonance behavior when getting thinner (probably not surprising but nevertheless quite obvious when knuck-testing the two thicknesses).
In terms of glues I imagine some kind of epoxy glue with tungsten powder to add (very local) mass - or maybe a thick shellac mixture again with e.g. tungsten powder to add (local) mass. Possibly also two thin layers of different glues/composite masses so as to have slightly different damping qualities of the different materials while maintaining a low mass. Don't know if this is effective, though, but I reckon a measurement may give some information about this.
Any chance you can say just a bit about how your glue is made (I of course fully respect any reservation you may have here). If possible/ok with you - and in case it proves feasible in my context - I may also be interested in buying just a bit from you, in a first round for testing.
And then again I hope someone here may suggest a software that I can use for measurements ... and is straightforward to use
Cheers,
Jesper
P.S.: Regarding my software question I've just started a separate thread for this:
http://www.diyaudio.com/forums/soft...resonance-measuring-software.html#post4955666
- reckon more people may see it. Yet to any readers of this thread please be welcome to post a suggestion you may have ... ;-)
Jesper
http://www.diyaudio.com/forums/soft...resonance-measuring-software.html#post4955666
- reckon more people may see it. Yet to any readers of this thread please be welcome to post a suggestion you may have ... ;-)
Jesper
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I think that there will be lots of software that can show accelerometer data. The problem is, as with any measurement, is how to interpret it. How you setup the test is the key factor. Just putting an accelerometer on a cabinet probably won't tell you a thing. The standard measurement for damping uses a cantilever of the various materials and structure. By measuring the Q of the resonance(s) one can extract the damping. Its hardly trivial, but doable.
My glue is a 2k soft polyurethane filled with glass micro-balloons. In damping, its friction that matters, more mass tends to lower the damping because there is more kinetic energy to dissipate. The best "damped" structures are light with very high internal friction. Epoxy is so rigid that it doesn't move at all so there can never be any internal friction. To have friction you must allow for movement. High stiffness does move resonances upward, but at ever higher Q. Lower frequency resonances at very low Q are what I am after.
Aluminum is a perfect example. Very stiff, but rings like a bell.
A casting of my filled poly is as dead as sand, but hundreds of times stiffer.
My glue is a 2k soft polyurethane filled with glass micro-balloons. In damping, its friction that matters, more mass tends to lower the damping because there is more kinetic energy to dissipate. The best "damped" structures are light with very high internal friction. Epoxy is so rigid that it doesn't move at all so there can never be any internal friction. To have friction you must allow for movement. High stiffness does move resonances upward, but at ever higher Q. Lower frequency resonances at very low Q are what I am after.
Aluminum is a perfect example. Very stiff, but rings like a bell.
A casting of my filled poly is as dead as sand, but hundreds of times stiffer.
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I hope this thread has been referred to already:
http://www.diyaudio.com/forums/equipment-tools/267734-accelerometer-testing-loudspeaker-drivers.html
I bought one of Georges accelerometers, highly recommended. Information here:
gntanavaras@gmail.com
Information can be processed with standard software like ARTA. Much information can be derived from FFT and CSD plots.
No serious amateur should go on designing speakers without a device like this.
http://www.diyaudio.com/forums/equipment-tools/267734-accelerometer-testing-loudspeaker-drivers.html
I bought one of Georges accelerometers, highly recommended. Information here:
gntanavaras@gmail.com
Information can be processed with standard software like ARTA. Much information can be derived from FFT and CSD plots.
No serious amateur should go on designing speakers without a device like this.
! Yes I don't know why so much people have this obsession of metal cabinet ! Ok for some brands as you don't sell flagship for the sound but by snobism ! Mostly the purchasers buy it to show to their friends the huge modern art bad sounding speaker which is more liking to a metal suppository for mamuth than Art !I'm asking myself if it's not better to make light wood case to get a higher panel resonance than damp it from the outside by a layer of Yoga carpet ?
Often seen in Stereophile resonances in 400/600 Hz even from the expensives Alexandria speakers or the Vivid !
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Wood tends to be low damping. The best that I have found are polyurethane planks. These are extremely well damped. The thing is that damping on the outside is usually very poor. It is the structure that needs damping and the damping must be part of the structure. Add-ons like carpet will not do very much. Carpet may reduce the radiation of sound however, even if it doesn't reduce the vibration. This is like coating a submarine with a soft material (which they do). It reduces reflection and radiation. However, in submarines a great deal of internal structural damping is done, including active noise control. In fact the concepts were first developed and deployed in submarines.
@vacuphile: Thanks for the tip on the accelerometer amplifier and ARTA. I actually remembered ARTA myself earlier today and seeing that it does CSD plots I think I will go this way. Compared with the ACH-01 one of the advantages of the ADXL-001 is that it is physically very small and also weighs about 1/20 of the ACH-01. Thus, everything else being equal, it may "intrude" less on the measurement than the ACH-01.
@Eldam: Yes, metals ... aluminum wouldn't be my choice for a loudspeaker but I actually also reckon it may have quite a say in e.g. amplifiers where the output transistors often are mounted on aluminum heatsinks. I assume it would be positively audible if another arrangement could be found.
Cheers,
Jesper
@Eldam: Yes, metals ... aluminum wouldn't be my choice for a loudspeaker but I actually also reckon it may have quite a say in e.g. amplifiers where the output transistors often are mounted on aluminum heatsinks. I assume it would be positively audible if another arrangement could be found.
Cheers,
Jesper
Thanks Earl for the inputt, yep I saw your last iteration was with such lighter cabinet
For the simple DIY do you believe than hard reticuled foam with sealed cells is solid enough to keep internal driver wave and damp ? Maybe not solid (stiff) enough ? 'à la Vandersteen?)
I liked what xrq971 and some made with lighter foam ! but when you have bigger drivers....
For the simple DIY do you believe than hard reticuled foam with sealed cells is solid enough to keep internal driver wave and damp ? Maybe not solid (stiff) enough ? 'à la Vandersteen?)
I liked what xrq971 and some made with lighter foam ! but when you have bigger drivers....
I am not sure if by "hard reticuled foam with sealed cells" you are including the poly boards that I use, but I assure you that the boards that I use are solid enough. There are several grades, I use the medium grade. The more rigid grade tends to make for a heavy cabinet.
This material is used for making CNC models for use as forms. It's not some DIY material, it's for professional usage. But it is very very expensive (10x MDF) - that's the downside - but I don't think that there is a "better" material. Look it up, its called Renshape (there are other brands as well.)
This material is used for making CNC models for use as forms. It's not some DIY material, it's for professional usage. But it is very very expensive (10x MDF) - that's the downside - but I don't think that there is a "better" material. Look it up, its called Renshape (there are other brands as well.)
No I just talked about hard/solid foam which can be cut easily with a knife or a saw ! Some are airy but the cells are sealed (at the opposite of your acousitical hom filters which have open cells iirc)
I understood you are using more polymer technology which need moulds ! It asks some skills and more Investment than a standalone simple diy speaker assume !
I also think about some house isolation external pannels... But as you said, all this is physic and need solid measurement ! Few here measure panels vibrations, I bet less a dozen (but the semi-pro whom are making kits maybe !)
My best if I was doing speaker as an enthusiast will be the Dynudio method : a driver with good coupling to a panel (why not a thin soid plastic (wooded carbon if your wallet is deep) which allow good rear radiation for the driver, this last glued on a cabinet with a big open front bafle : One has to find the glue which allow enough damping/decoupling, no toxic for home and family, and time proof (imagine the panel which drops on the floor after two years !)
I understood you are using more polymer technology which need moulds ! It asks some skills and more Investment than a standalone simple diy speaker assume !
I also think about some house isolation external pannels... But as you said, all this is physic and need solid measurement ! Few here measure panels vibrations, I bet less a dozen (but the semi-pro whom are making kits maybe !)
My best if I was doing speaker as an enthusiast will be the Dynudio method : a driver with good coupling to a panel (why not a thin soid plastic (wooded carbon if your wallet is deep) which allow good rear radiation for the driver, this last glued on a cabinet with a big open front bafle : One has to find the glue which allow enough damping/decoupling, no toxic for home and family, and time proof (imagine the panel which drops on the floor after two years !)
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