(Multi)meter for speaker testing

[unknownuser]

I am taking the step of messuring my own drivers for more accurate speaker building. I have a question on recomended (multi)meters. At issue is AC voltage messurements. Every meter I own only lists AC voltage range down to 40hz. I looked online and it seems this is standard for most all meters. I did see one that listed down to 10hz for AC voltage but it was priced over $3,000. A little more then I am willing to sink into a voltage meter. Is this just an issue off how far off the accuracy drops below 40hz?

The "best" meter I currently have is a hand held Ideal 61-633 true RMS DMM. Thats in the $300-400 range.


(Originally posted by: moro)

[curt_c]

It would be far easier and faster to use your computer/sound card to make the measurements using freeware like Speaker Workshop’s program.

IMO, you would be better off to spend your money on a calibrated mic, mic preamp, and measurement software.

C

[unknownuser]

> It would be far easier and faster to use
> your computer/sound card to make the
> measurements using freeware like Speaker
> Workshop’s program.

> IMO, you would be better off to spend your
> money on a calibrated mic, mic preamp, and
> measurement software.

> C

Yeah, I already downloaded speaker workshop. Putting together a Wallin 2 jig tonight. I just wanted to do it the "old" way a few times to help me wrap my brain around what the computer is doing automaticly. I think I will just use the meters I have now and see how they do, since I plan on moving to speaker workshop very soon.

For short term I am going to use a DIY panasonic mic. Looks like a popular upgrade from that is the Bheringer mic and preamp.

O, btw, did you (Curt C.) ever do a X-over design for a 2 way dayton 6 1/2 and 1/8th tweeter to match up with the Triunes? I have seen plenty of projects using those in a 2 way, but not one ment to balance with the triunes.


(Originally posted by: moro)

[david_l]

Why not just calibrate your existing meter by setting it up however you are going to measure the drivers( usually the constant voltage method) and connect a known resistor in place of the driver and note the readings on your voltmeter at different frequencies across the sampling resistor and write down the difference? Since you will always be keeping the voltage across the sampling resistor at a constant voltage when measureing the driver, just add the required correction to the reading at each frequency and correct accordingly.

[curt_c]

> O, btw, did you (Curt C.) ever do a X-over
> design for a 2 way dayton 6 1/2 and 1/8th
> tweeter to match up with the Triunes? I have
> seen plenty of projects using those in a 2
> way, but not one ment to balance with the
> triunes.

I’ve not done an MT with the silkie and the 6 ½” Dayton Classic, as the midrange performance was not up to the performance of the 5 ¼” Dayton Classics.

C

[curt_c]

http://sound.westhost.com/tsp-f2.gif

Provided Link: http://sound.westhost.com/tsp.htm


> Why not just calibrate your existing meter
> by setting it up however you are going to
> measure the drivers( usually the constant
> voltage method) and connect a known resistor
> in place of the driver and note the readings
> on your voltmeter at different frequencies
> across the sampling resistor and write down
> the difference? Since you will always be
> keeping the voltage across the sampling
> resistor at a constant voltage when
> measureing the driver, just add the required
> correction to the reading at each frequency
> and correct accordingly.

That method won’t quite work, as it assumes the source is linear at the frequency extremes, -which it likely is not due to amplitude variations in the generator, and possibly the amplifier. That is why you monitor (with an accurate meter) to keep the voltage across the series resistor constant, but here we have no accurate reference for comparison at the frequency extremes.

C

[unknownuser]

> I’ve not done an MT with the silkie and the
> 6 ½” Dayton Classic, as the midrange
> performance was not up to the performance of
> the 5 ¼” Dayton Classics.

> C

oops, my mistake I ment 5 1/4 2 ways to match the triunes. I have a set of triunes I use in my HT setup. I have some back surrounds but they are old Infinity 2 ways. Would like to build some 2 ways with the same drivers and a crossover that voices the same as the Triunes. If you have not done anyhting, I may take a look at the Triune crossover and see what I can come up with.


(Originally posted by: moro)

[petermars]

http://www.mindspring.com/~pmars/speakers/test-setup.jpg


Here's what I do... it seems to work well.

Use a 1K ohm resistor in series with a "calibration" resistor of the same value as Re for the driver. The 1K resistor creates a very constant current source no matter what your amp is doing at various frequencies.

Set your multimeter to mV scale and set voltage at stand-in resistor to display the exact same value as the "calibration" resistor.

I used 3.4 ohms in drawing below, because that was the measured Re of my 4 ohm driver. Once you get your mV reading to 3.4, or whatever your actual Re and therefore "calibration" resistor is, your multi-meter is calibrated.

Next remove the "calibration" resistor and connect the driver.
You will now be monitoring your driver mV (now calibrated to indicate impedance instead )

Run your freq. sweep, or plot your individual Freq/Imp points.

Don't change any amplifer or tone generator levels when swapping the driver for the "calibration" resistor.

It works very well. Calibration resistor can be made up of as many resistors as necessary, in any configuration, to match the Re of your driver. 1/4 watt or 1/2 watt resistors work fine.

Pete

[petermars]

> Set your multimeter to mV scale and set
> voltage at stand-in resistor to display the
> exact same value as the
> "calibration" resistor.

Instead of "Stand-in resistor" I meant "calibration" resistor... sorry! You want your meter to read the exact same number value as your Re stand-in... or "Calibration" resistor.

A calibration resistor is used because it is non-inductive, and will give a fairly accurate reading at whatever Freq. you choose to calibrate with. I chose 35 hz because I was testing a sub in this circuit diagram. 4 ohm driver with Re of 3.4 ohms in this example... yours will be different.

Pete