Measuring speaker stuff starting with Thiele-Small parameters
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 Multi-Way Conventional loudspeakers with crossovers

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 9th January 2019, 11:41 AM #11 Lojzek   diyAudio Member     Join Date: Feb 2012 Location: Croatia Audiomatica Clio 4.51 standard small signal TSP evaluation has got 1Vrms of output voltage in a measurement setup that includes driver only in the circuit, the so called internal mode of measurement, and the output impedance of clio card is 100R. You can make trial measurements with lesser voltages and investigate if there are significant differences. I get consistent results by having 15R of a resistor in the circuit and a driver, powered by a headphone out of a laptop sound chip at Vout=0.5V rms. In that case, the output impedance of a sound chip is 68R. __________________ "Immer wenn du denkst es geht nicht mehr, kommt irgendwo ein Lichtlein her."
 9th January 2019, 05:52 PM #12 DualTriode   diyAudio Member   Join Date: Aug 2009 Location: Nor Cal Hello JohnPM and Lojzek, There is a range; 0.1 - 1.0 volts. I will start low and work my way up. The AP hardware has a test amplifier with a fixed gain of 20 and has the recommendation for small signal of not exceeding 1 volt output. Kind of interesting that the instructions are so fuzzy on the topic. Thanks DT
GM
diyAudio Member

Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
 Originally Posted by DualTriode I am thinking of using the added weight method as opposed to the known volume box to do the measurements.
FWIW the pioneers determined that the net box volume [Vb] raise Fs by > 1.56x, so lowering it > 1.56x is theoretically the most accurate, which from dim memory is ~1.5x Mms, so can get pretty heavy for [sub] woofers.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 10th January 2019, 02:59 AM #14 Jack Hidley   diyAudio Member     Join Date: May 2007 Location: Danville, CA Never attach a magnet or any ferrous material to the cone. If you do this near the dust cap, so it doesn't excite any rocking modes, it is going to affect the magnetic forces in the gap. If you do it near the surround, there will be rocking modes and it will change the parameters. If you use a 50/50 mix of blue tack and standard hardware store blue stick for hanging things on the walls, the mixture will not be sticky enough to damage any cones. If you want the most accurate results for the perturbation derived parameters, add the known weight to the cone and take a nearfield frequency response before and after. In the passband, subtract one response measurement from the other. Given the known added mass, this makes it very easy to determine the drivers moving mass perfectly. You then use this to calculate everything else. To determine an optimum drive level, take multiple impedance curves starting at the lowest level and increasing to the maximum level. Look at the frequency of Fs. The best accuracy will happen when you use the drive level where the Fs measurement is the lowest. __________________ Jack Hidley ACS
 10th January 2019, 03:24 AM #15 Dave R   diyAudio Member     Join Date: Aug 2006 Another useful fact is that a US nickel is 5 grams. I like the non-residue blue tack, and I have a mass scale to accurately measure within 0.1 gram. Harbor freight had an inexpensive mass scale on sale recently (around \$10). Don't know how accurate it is, but you could check against a quantity of nickels or AA batteries, etc. __________________ - Dave R the 200% Norske Last edited by Dave R; 10th January 2019 at 03:26 AM.
 11th January 2019, 07:07 AM #16 DualTriode   diyAudio Member   Join Date: Aug 2009 Location: Nor Cal Hello, An old friend told me about the Zen of Motorcycle Maintenance; the motorcycle needs to know that you are not afraid to break it, only then will the motorcycle cooperate. I am afraid of breaking my APx 1701 transducer interface adaptor. This afternoon I spent an hour with customer service in Beaverton. I am all set now for monitoring voltage and current across the sense resistor and monitoring voltage across the driver under test. All I need now is to put together a XLR test lead to connect the analyzer to the DUT. Thanks DT
 11th January 2019, 07:36 AM #17 Lojzek   diyAudio Member     Join Date: Feb 2012 Location: Croatia There is specs for APx1701 that say maximum of 10Vpk for balanced and 5 Vpk unbalanced. Before you connect wires to AP's input, you can check the voltage that is supposed to enter the AP with a multimeter first. __________________ "Immer wenn du denkst es geht nicht mehr, kommt irgendwo ein Lichtlein her."
DualTriode
diyAudio Member

Join Date: Aug 2009
Location: Nor Cal
Quote:
 Originally Posted by Lojzek There is specs for APx1701 that say maximum of 10Vpk for balanced and 5 Vpk unbalanced. Before you connect wires to AP's input, you can check the voltage that is supposed to enter the AP with a multimeter first.
Thank you, sounds like a job for mister Fluke.

DT

 11th January 2019, 09:06 PM #19 Jack Hidley   diyAudio Member     Join Date: May 2007 Location: Danville, CA If you are going to measure low impedances with the AP, you should just build a current source. It is extremely accurate, the wiring is super simple and there is no chance of damaging the input circuitry. __________________ Jack Hidley ACS
DualTriode
diyAudio Member

Join Date: Aug 2009
Location: Nor Cal
Quote:
 Originally Posted by Jack Hidley If you are going to measure low impedances with the AP, you should just build a current source. It is extremely accurate, the wiring is super simple and there is no chance of damaging the input circuitry.
Jack,

The amplifiers in the apx1701 are pretty much a voltage source. The specified output impedance is 0.13R including the 0.1R sense resistor.

Please tell me more about what you are thinking about with a current source and low impedance measurement!

I am cautious about the voltage; one day a long ago I stuck a probe into a tube circuit and shorted B+ volts into my the SYS2522. Duke fixed it for me.

Thank You DT

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