PVDF Accelerometer
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PS: when John Atkinsom measures panel rsonances with his little device... what kind of device is that and where would one get one (or get something to repurpose)?
/quote/
This was posted a few days ago...I'm just not around every day or I would have responded. The following links may help you out:
Measurement Specialties, Inc.
http://www.meas-spec.com/myMeas/default/index.asp
http://www.meas-spec.com/myMeas/sensors/piezo.asp
http://www.meas-spec.com/myMeas/sensors/piezoSensors.asp
Piezoelectric Film Transducers
http://www.pages.drexel.edu/~st96p2ha/piezo.html
/quote/
PS: when John Atkinsom measures panel rsonances with his little device... what kind of device is that and where would one get one (or get something to repurpose)?
/quote/
This was posted a few days ago...I'm just not around every day or I would have responded. The following links may help you out:
Measurement Specialties, Inc.
http://www.meas-spec.com/myMeas/default/index.asp
http://www.meas-spec.com/myMeas/sensors/piezo.asp
http://www.meas-spec.com/myMeas/sensors/piezoSensors.asp
Piezoelectric Film Transducers
http://www.pages.drexel.edu/~st96p2ha/piezo.html
What to build speakers out of... multilayered construction?
I was thinking about building speakers using a multi-layered construction. Does anyone have any feeling one way or the other with regard to the construction of the Pioneer TAD Model 1 or speakers like it?
The layers would be made out of material similar to Russian Baltic Birch plywood. I know that the cost would be exorbitant but I'm looking into this method for all the reasons everyone is discussing herein.
http://tadhomeaudio.com/images/CabinetInterior.jpg
http://tadhomeaudio.com/images/cabinet-exp.jpg
http://tadhomeaudio.com/images/CoverSpeaker.jpg
I was thinking about building speakers using a multi-layered construction. Does anyone have any feeling one way or the other with regard to the construction of the Pioneer TAD Model 1 or speakers like it?
The layers would be made out of material similar to Russian Baltic Birch plywood. I know that the cost would be exorbitant but I'm looking into this method for all the reasons everyone is discussing herein.
http://tadhomeaudio.com/images/CabinetInterior.jpg
http://tadhomeaudio.com/images/cabinet-exp.jpg
http://tadhomeaudio.com/images/CoverSpeaker.jpg
Re: What to build speakers out of... multilayered construction?
Called translam construction (or layertoning)... other than having huge waste and the need to have access to a CNC this technique is very good.
You can use all sorts of material (stay away from all mdf / Rob Well's story tells why), and even use different materials and in different thicknesses. Walls can vary in thickness, and can be made very irregular inside (check out seven veils)
One thing too note in the exploded pioneer/TAD ... they could have done the braces better -- braces should run in the longest direction....
Another trick you could do, would be to purposely build up a very holey, open cel structure in the middle of the box -- this should have a dramatic effect on stide-to-side standing waves
Not as stiff as doing it the way B&W does....
dave
showflash said:
Called translam construction (or layertoning)... other than having huge waste and the need to have access to a CNC this technique is very good.
You can use all sorts of material (stay away from all mdf / Rob Well's story tells why), and even use different materials and in different thicknesses. Walls can vary in thickness, and can be made very irregular inside (check out seven veils)
One thing too note in the exploded pioneer/TAD ... they could have done the braces better -- braces should run in the longest direction....
Another trick you could do, would be to purposely build up a very holey, open cel structure in the middle of the box -- this should have a dramatic effect on stide-to-side standing waves
Not as stiff as doing it the way B&W does....
dave
Re: PVDF Accelerometer
A couple of days back I was probing with a screwdriver between an ear and a baffle, with some interesting results. Not very scientific, thinking about a DIY solution, the best idea to date is a magnetic phono cartridge mounted on a stand, with suitable mass, with the stylus positioned on the baffle in question.
The results could be observed on a CRO, studied on a storage CRO, or just fed to a level meter. A mic pre-amp should do the job - no need for RIAA eq.
Another possibility could be using the receiving end of a guitar reverb unit. Instead of springs, attach a high tensile wire, the other end going to the framework. A small block could couple the wire to the baffle.
The unit would be placed in front of the baffle, such that the wire was parallel to the surface under test.
None of those methods will give absolute data, only comparative.
Back to the screwdriver in the earole. The big surprise was the amount of energy transferred was from the edge of the baffle, not the front. That was on MDF.
Cheers,
Geoff
A couple of days back I was probing with a screwdriver between an ear and a baffle, with some interesting results. Not very scientific, thinking about a DIY solution, the best idea to date is a magnetic phono cartridge mounted on a stand, with suitable mass, with the stylus positioned on the baffle in question.
The results could be observed on a CRO, studied on a storage CRO, or just fed to a level meter. A mic pre-amp should do the job - no need for RIAA eq.
Another possibility could be using the receiving end of a guitar reverb unit. Instead of springs, attach a high tensile wire, the other end going to the framework. A small block could couple the wire to the baffle.
The unit would be placed in front of the baffle, such that the wire was parallel to the surface under test.
None of those methods will give absolute data, only comparative.
Back to the screwdriver in the earole. The big surprise was the amount of energy transferred was from the edge of the baffle, not the front. That was on MDF.
Cheers,
Geoff
Geoff,
Was that a box or OB? Imagine the noise at the edges with real wood instead of MDF. Typical approaches do little to address what we're hearing at the edges other than decoupling the driver frame from structure. I'm sure that something more is needed to prevent sound from entering the structure at the driver cutout where SPL's are their highest by using some damping material there and/or dissipating the energy that enters the baffle there.
The problem is very driver dependant, because with some drivers the frame itself will block much of the radiation toward the edge of the cutout
I plan to first try damping the cutout with clay or duct seal, but I think something like the mounting rings I mentioned before will be needed to cure the problem.
Was that a box or OB? Imagine the noise at the edges with real wood instead of MDF. Typical approaches do little to address what we're hearing at the edges other than decoupling the driver frame from structure. I'm sure that something more is needed to prevent sound from entering the structure at the driver cutout where SPL's are their highest by using some damping material there and/or dissipating the energy that enters the baffle there.
The problem is very driver dependant, because with some drivers the frame itself will block much of the radiation toward the edge of the cutout
I plan to first try damping the cutout with clay or duct seal, but I think something like the mounting rings I mentioned before will be needed to cure the problem.
The ressonanse in the middle of the plate will move outwards towards the corners, just like rings in the water
When all the ressonanses from all sides meet in the corners I would expect all sorts of nasty things to be going on
Thats why, in my next speaker, I will use soft wooden lists in all corners inside the box - like in the old days, only differense.... it will be glued with a thin layer of some sort of acrylic glue
When all the ressonanses from all sides meet in the corners I would expect all sorts of nasty things to be going on
Thats why, in my next speaker, I will use soft wooden lists in all corners inside the box - like in the old days, only differense.... it will be glued with a thin layer of some sort of acrylic glue
soft wood
Tinitus:
By soft wood do you mean pine or softer like balsa? Should they be corner gussets?
Ricky:
I am recycling some Bozak cabinets for use as subs and intend the identical two-layer treatment since the cabinets are made of high density patricle board. Why did you choose PVA over some of the other glues/adhesives mentioned and what is the "cold press" process?
Ray
Tinitus:
By soft wood do you mean pine or softer like balsa? Should they be corner gussets?
Ricky:
I am recycling some Bozak cabinets for use as subs and intend the identical two-layer treatment since the cabinets are made of high density patricle board. Why did you choose PVA over some of the other glues/adhesives mentioned and what is the "cold press" process?
Ray
Pine would be fine 
balsa would be streching it too far in softness, but there are some other exsotic soft wood that might woork
But I dont think it matters much, which kind of wood to be glued in the corners - its the glue and the amount of it that matters, and ofcourse the size of the "quarter-staff" (if thats the right word ?)
balsa would be streching it too far in softness, but there are some other exsotic soft wood that might woork
But I dont think it matters much, which kind of wood to be glued in the corners - its the glue and the amount of it that matters, and ofcourse the size of the "quarter-staff" (if thats the right word ?)
Quater Staff
tinitus,
I am unsure about the definition of "quarter staff"....could you mean a triangular shapped block that fits into the corner?
Can you be more specific about Acrylic Glue? I am familiar with PVA(yellow/white wood glue), Polyurethane(Gorilla Glue) and Epoxy but not acryllic.
Ray
tinitus,
I am unsure about the definition of "quarter staff"....could you mean a triangular shapped block that fits into the corner?
Can you be more specific about Acrylic Glue? I am familiar with PVA(yellow/white wood glue), Polyurethane(Gorilla Glue) and Epoxy but not acryllic.
Ray
I think the wooden "lists" should be squared, at least 1"x1" - the word quaterstaff was a longshot
Acrylic .... maybe you call it silicone, but around here silicone is less strong than acryllic .... the strongest type used fore bathrooms or outside construction repair
It should be applied very thin and evenly to the joints - after joining, it will hold itself in place untill dry, so its very easy to handle - if it works .... well, I expect it will
Acrylic .... maybe you call it silicone, but around here silicone is less strong than acryllic .... the strongest type used fore bathrooms or outside construction repair
It should be applied very thin and evenly to the joints - after joining, it will hold itself in place untill dry, so its very easy to handle - if it works .... well, I expect it will
tinitus,
I understand. It is used here for the same purpose...to set tiles in baths etc. and as a sealant in outdoor applications. It is usually called acrylic CAULK. There is also silicon caulk.
Many years ago I built several aquariums using silicon adhesive(trade name was Silastic) without using the typical steel frames. Two were over 40 gallons and held just fine. I think that the varity I used must have been very strong?!
Ray
I understand. It is used here for the same purpose...to set tiles in baths etc. and as a sealant in outdoor applications. It is usually called acrylic CAULK. There is also silicon caulk.
Many years ago I built several aquariums using silicon adhesive(trade name was Silastic) without using the typical steel frames. Two were over 40 gallons and held just fine. I think that the varity I used must have been very strong?!
Ray
Re: PVDF Accelerometer
Building a simple vibration meter
http://www.dimensionengineering.com/appnotes/vibration_meter/vibration_meter.htm
Building a simple vibration meter
http://www.dimensionengineering.com/appnotes/vibration_meter/vibration_meter.htm
Ray Collins said:
Ray: Silicone like the one you used on your aquarium is a little stronger than acrylic caulk, and drys quicker. What is REALLY strong is glue. If you are joining two pieces of wood, use wood glue.
The problem with using caulk in place of glue is that it's not designed to be an adhesive. Acrylic will take a few days to reach maximum strength, silicone does not form an exceptional bond with wood. These are problems that the proper glue doesn't have. I've used gallons of yellow carpenters glue in my lifetime, and have never had a problem. Even if the parts don't fit as tight as they should, glue will still outperform caulking.
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