Hi Ente
I missed your literature on the Dumas system and how it works and how to make the housing, can you please share this again and any detailed information that you may have. A quick internet search did not provide much information.
Best Regards
I missed your literature on the Dumas system and how it works and how to make the housing, can you please share this again and any detailed information that you may have. A quick internet search did not provide much information.
Best Regards
Sorry, of course it's DUMAX!
A few years ago, inspired by IEC 62458-2011-07: Sound system equipment – Electroacoustical transducers – Measurement of large signal parameters, section 4.2, I also tried to determine large-signal parameters. However, I didn't use a DC or very low-frequency signal for the static displacement, but rather pressure/vacuum. Anyone who owns a laboratory power supply and is willing to invest €15 for a cheap Pollin air pump (https://www.pollin.de/p/daypower-luftpumpe-lp36-12-12-v-330071) can easily perform a BL(x) measurement.
The pump generates either pressure or vacuum in a suitable loudspeaker cabinet. This pressure/vavuum results in a specific positive/negative displacement of the loudspeaker, at which the impedance is then measured with a small-signal level. This must be repeated for several excursion positions. The procedure is therefore almost identical to that of DATS LA.
I did not calculate the deflection, but measured it using a triangulation laser (see also https://www.artalabs.hr/AppNotes/AP7...8-GerRev01.pdf).
If you don't have a laser, you can find a solution for measuring deflection at Linkwitz (keyword: wedge micrometer).
Regards
Heinrich
A few years ago, inspired by IEC 62458-2011-07: Sound system equipment – Electroacoustical transducers – Measurement of large signal parameters, section 4.2, I also tried to determine large-signal parameters. However, I didn't use a DC or very low-frequency signal for the static displacement, but rather pressure/vacuum. Anyone who owns a laboratory power supply and is willing to invest €15 for a cheap Pollin air pump (https://www.pollin.de/p/daypower-luftpumpe-lp36-12-12-v-330071) can easily perform a BL(x) measurement.
The pump generates either pressure or vacuum in a suitable loudspeaker cabinet. This pressure/vavuum results in a specific positive/negative displacement of the loudspeaker, at which the impedance is then measured with a small-signal level. This must be repeated for several excursion positions. The procedure is therefore almost identical to that of DATS LA.
I did not calculate the deflection, but measured it using a triangulation laser (see also https://www.artalabs.hr/AppNotes/AP7...8-GerRev01.pdf).
If you don't have a laser, you can find a solution for measuring deflection at Linkwitz (keyword: wedge micrometer).
Regards
Heinrich
Hi Ente & Hurrication thanks for your replies.
This very practical, easily executable approach is very good.
Going further if we add a compound gauge (pressure & vacuum) and measure the - Linearity of pressure increase the to movement of the cone - we will be able to gauge the linearity of the suspension system.
We will also be able to judge the effective restoring force of the suspension system beyond xmax.
I think with this & Arta + Laser as in the link posted here - quite a bit of large signal parameters can be determined to effectively improve driver design at Motor & Suspension system level at really good costs levels - along with keeping the spirit of DIY
Since we have really good people here - can we look at some mathematical relationships - between the linearity of pressure increase to cone movement.
Some other discussion points
1. Getting the compound gauge with equal scales on both sides may be difficult, building up large vacuum may be difficult for large drivers - In this case we can just remove the driver and mount it magnet outwards for the -ve movement and use pressure readings -- and compare apples to apples
2. We can short the VC and map the pressure reduction to drive the cone outwards.
Best Regards
Suranjan
This very practical, easily executable approach is very good.
Going further if we add a compound gauge (pressure & vacuum) and measure the - Linearity of pressure increase the to movement of the cone - we will be able to gauge the linearity of the suspension system.
We will also be able to judge the effective restoring force of the suspension system beyond xmax.
I think with this & Arta + Laser as in the link posted here - quite a bit of large signal parameters can be determined to effectively improve driver design at Motor & Suspension system level at really good costs levels - along with keeping the spirit of DIY
Since we have really good people here - can we look at some mathematical relationships - between the linearity of pressure increase to cone movement.
Some other discussion points
1. Getting the compound gauge with equal scales on both sides may be difficult, building up large vacuum may be difficult for large drivers - In this case we can just remove the driver and mount it magnet outwards for the -ve movement and use pressure readings -- and compare apples to apples
2. We can short the VC and map the pressure reduction to drive the cone outwards.
Best Regards
Suranjan
And I guess this thread will bring about Dats LA - End of Life.
The idea was good - implementation not accurate.
The idea was good - implementation not accurate.
That is an idea!
Might need to set this up.
I'm currently looking on Aliexpress for compound pressure transducers. Should be an interesting way to measure drivers that I forgot about.
Thank you Heinrich! I forgot about this! I will have a busy summer I think. Making up a few bits of a thorough test system. A DIY Klippel Turntable and mic movement system and this driver measurement system. DATs as the other versions never impressed me. Too bad Smith&Larson stopped production. It is the most solid test system that was available commercially for a reasonable price. I still run a Smith&Larson Speaker Tester Pro.
https://www.amazon.ca/DC12V-Vacuum-...eb4-4f78-9ffa-846504a626f9&pd_rd_i=B07T7Z4QNQ
Possible candidate. And for simplicity I was thinking of buying a plastic drum and cutting the drum to a more practical height. You already have most of an airtight system and you attach a flange, to the flange you attach different baffle boards. If you make the flange wide enough for over center clamps you have a system that is fairly easy to make up.
These kinds of barrels are available second hand for very reasonable prices. Just pick your previous contained liquid with some caution. Most of the time the vendor sells the barrels washed. With judicious thoughts you can use the barrel to your advantage in that you have a ready made container that will hold a modest vacuum and a modest pressure required to make the driver diaphragm movements.
In the past I have qualified many drivers for meeting or not meeting their specifications. There are a few very accurate, very low tech ways of measuring diaphragm movement.
Possible candidate. And for simplicity I was thinking of buying a plastic drum and cutting the drum to a more practical height. You already have most of an airtight system and you attach a flange, to the flange you attach different baffle boards. If you make the flange wide enough for over center clamps you have a system that is fairly easy to make up.
These kinds of barrels are available second hand for very reasonable prices. Just pick your previous contained liquid with some caution. Most of the time the vendor sells the barrels washed. With judicious thoughts you can use the barrel to your advantage in that you have a ready made container that will hold a modest vacuum and a modest pressure required to make the driver diaphragm movements.
In the past I have qualified many drivers for meeting or not meeting their specifications. There are a few very accurate, very low tech ways of measuring diaphragm movement.
👍Or an un-used speaker cabinet lying around. The clamp is a very good find.
You will find when you try to draw a vacuum that many cabinets are not exactly airtight.
And as a transducer design consultant I design everything from 50mm drivers to 610mm drivers. So a one piece setup is a good idea. I'm thinking about building a tetrahedral test enclosure, atop of this might be a good place for the pressure/vacuum chamber.
Your idea about directly measuring the Cms. Care to elaborate on this? I have two LASER displacement instruments. One faster the other slower. Ebay is an independent Consultants friend.
Speaking of Ebay
https://www.ebay.ca/sch/i.html?_nkw...sacat=0&_from=R40&_trksid=p2332490.m570.l1313
The actual pressure and vacuum range required is not that great.
To be able to integrate this into a measurement system will be what makes my head hurt the most.
Further to this brain storm How about Commercial kitchen pots? I'm in Canada. Costco is a company that has these are reasonable prices. ANd they are already available is many sizes. Aluminium so easy to work with. OK tiny brain storm over.
This will be the difficult part - but i think this way we can find a relationship. To establish the mathematical model - we will need to work together here on data, my idea is not very well formed - but we can find a direct relationship this way -
Case - 1
A) we know the maximum mechanical strength of the BL - ie we short the VC. (BxL , L in the gap or total L we need to brainstorm)
B) we pressurize and read the pressure required to move the cone in +ve direction 1mm , then 2mm , then 3mm and so forth , your slow laser will be helpful - as we can freeze the cone movement where ever we like by stopping air flow.
c) we vacuum and read the cone movement -ve direction // or we can remove the driver and mount is in reverse and not use vacuum at all and do both movement by pressure.
Case - 2
A) we keep the VC - open not shorted
B) we pressurize and read the pressure required to move the cone in +ve direction 1mm , then 2mm , then 3mm and so forth , your slow laser will be helpful - as we can freeze the cone movement where ever we like by stopping air flow.
c) we vacuum and read the cone movement -ve direction // or we can remove the driver and mount is in reverse and not use vacuum at all and do both movement by pressure.
We should be able to develop a mathematical model for compliance - by removing the BL component by Case 1 - Case 2
We will need more input on this - from the good people here - but this is one way we have full control of the driver movement and can measure force to move the cone accurately, we need to take advantage of this.
Best Regards
Suranjan
Another relationship is with VC shorted - The force required to move the cone should only be the mechanical braking force being exerted by the coil , and this is known.
Therefore any additional force required to move the cone is the compliance restoring force
VC Shorted , Mech Force 1 = BL 1
Formula may be like -
Force required to move 1mm of cone (pressure x sd, most probably) = BL1 + Compliance restoring force.
something like this, I am not good with the math - can think of some of the relationships - more inputs are welcome
Best Regards
Suranjan
Therefore any additional force required to move the cone is the compliance restoring force
VC Shorted , Mech Force 1 = BL 1
Formula may be like -
Force required to move 1mm of cone (pressure x sd, most probably) = BL1 + Compliance restoring force.
something like this, I am not good with the math - can think of some of the relationships - more inputs are welcome
Best Regards
Suranjan
I design drivers and systems and I openly admit that I suck at math. I helped design our software. I can come up with relationships in the physics side of the designs. But math, higher level maths are a language that i struggle with. Your secondary idea is good. But there are caveats to this. Most loudspeaker motors are stronger on the inward side versus the outward side. I work very hard to get that as equal as possible. No simple task. There is also a B symmetry that needs to be known beforehand. As that it the reference in your second idea that I think is smart. My guess is the Klippel group have some app notes on parts of this.
I am still trying to find the complete standard for this type of measurement method. I am an AES member but not an IEC member.
IEC 62458-2011-07: Sound system equipment – Electroacoustical transducers – Measurement of large signal parameters, section 4.2
Does anyone have this standard? And are they willing to share it? The maths relationships are partly shown in the teaser section.
I am still trying to find the complete standard for this type of measurement method. I am an AES member but not an IEC member.
IEC 62458-2011-07: Sound system equipment – Electroacoustical transducers – Measurement of large signal parameters, section 4.2
Does anyone have this standard? And are they willing to share it? The maths relationships are partly shown in the teaser section.
https://www.cfuttrup.com/dpc/dpc.htm
Some of the most easy to read well distilled information on loudspeakers I know of. Klaus has written a great primer.
https://audioxpress.com/article/beyond-thiele-small-dumax-and-klippel-driver-measurement-systems
Some of the design of the Dumax system
I have the Original AES journal on Dumax if anyone wants it, contact me.
Some of the most easy to read well distilled information on loudspeakers I know of. Klaus has written a great primer.
https://audioxpress.com/article/beyond-thiele-small-dumax-and-klippel-driver-measurement-systems
Some of the design of the Dumax system
I have the Original AES journal on Dumax if anyone wants it, contact me.
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Hi
We will have to establish the BL curve first - then move to cms I think
Feed the coil a fixed voltage & current and move the cone by press/vac , most likely the - Back Emf V will directly proportional to B x L(no of turns in the gap) x V(velocity)
Once we know the BL +ve / -ve and here we can actually measure the drop in BL accurately. We apply it to the cms.
We will have to establish the BL curve first - then move to cms I think
Feed the coil a fixed voltage & current and move the cone by press/vac , most likely the - Back Emf V will directly proportional to B x L(no of turns in the gap) x V(velocity)
Once we know the BL +ve / -ve and here we can actually measure the drop in BL accurately. We apply it to the cms.
I am doubtful of the math the above formula needs a check, I think it will be something like this.
you laser will come in handy for measuring the velocity.
The pneumatics need to set up well with direction control valves to control the movement of the cone
The pneumatics need to set up well with direction control valves to control the movement of the cone
I grew up working in many trades. I am still a practising Cabinetmaker and Carpenter. I started out in the business of loudspeakers integrating other peoples drivers into cabinets in 1989. Plumbing is not even 4rth or 5th on my list. I have built complete houses a few times in my life. And by complete I mean everything other than digging the soil. I enjoy a challenge.
Integrating this into a computer interface is. As is making it as simple as possible. One of those large cooking pots is most likely the best method. A circle is best when dealing with either vacuum or pressure. I was a coder almost 40years ago. Not anymore. But I know a few guys who are much better at this than I am.