Measuring resonant/resonance peak - Questions/advice

[belwar]

Ok, first off this is another thread searching for good information on measuring resonant peak of pickups. I've done lots of searching and have gone about as far as I can on my own. I understand it is not a nessesity of pickup winding, but in order to keep detailed records of my evolution I would like to at least try - No harm in measurement!

Here are some questions I have if anyone is interested in helping out..

1) What is the difference between "resonant frequency" and "resonance peak".
2) Is there a mathematical calulation that can ben used to determin the peak or do you have to view a waveform?
3) I've read that a signal generator and occiliscope with X-Y capabilities are required to measure the peak. Are there methods that can be done on the computer easily?
4) I found a USB Computer ociliscope (model DSO-2250) which looks like it is also a signal generator. Does anyone with experience want to look over the specs and see if this would be suitable to do the task? I would be willing to buy one and test it. From the screen caps it looks like you could pull up waveforms showing the peak easily but it is all over my head.

Thanks for any help.

b.

[dpm]

really interested in this myself.

A fairly straightforward and not too expensive method would be lovely

[belwar]

I just came across a piece of software called Multi-Instrument 3.0 which uses your computer soundcard and two probes. Aparently you can use it as a signal generator, osciliscope, AND LCR meter.

Anyone care to check it out?

[StarryNight]

I just came across a piece of software called Multi-Instrument 3.0 which uses your computer soundcard and two probes. Aparently you can use it as a signal generator, osciliscope, AND LCR meter.

Anyone care to check it out?

It seems the LCR meter is an 'add on' for another $100. I guess this setup would depend if you have the space for a computer in your shop. It looks cool but if i have to carry my laptop down to the basement to test some pickups, i might not be so inclined to use it as often as if there was a dedicated machine right there to turn on. Yet, for the price of the software and a dedicated computer i think the Extech LCR meter might be more handy (literally) and cheaper in the long run. I'm in the same boat btw. I would love to have an LCR meter of some kind - but getting some stock would be nice too

[Possum]

...

You know for FREE, you can download Audacity, record some riffs and they have an analyzer built in. I just did some comparisons using that. You get the final tone out the speaker, but it is useful. I wanted to know if the middle pickup tone in a bucker guitar with its "sweet" tone is because of a mid-scoop, and yes it is, judging by the frequency response chart generated from selecting a section of the recording.

[David Schwab]

That's good to know. I have Audacity, but haven't used it much.

[Possum]

....

Audacity is a work in progress, download the latest version. Its designed by a bunch of hobbyists all working on it, some stuff doesn't work real well, the last version would crash and destroy your recording with it, nice. Its free and has alot of useful plug-ins but still can be buggy. If you record anything with it, its recommended that you immediately export it as an AIFF or WMA file so you have a reliable file that won't get killed :-)

[David Schwab]

I mostly use Spark XL which was a stereo audio editor made by TC Works. They discontinued their software line a while ago, but it's still been working through every OS X upgrade. I'll be sad when it breaks.

I have ProTools and stuff, but Spark is so damn handy. So I keep checking out other audio editors for when the inevitable happens.

[Achiles]

What about this?
http://buildyourguitar.com/resources/lemme/

[Bruce Johnson]

I'm quite interested in this subject too. I'd like to put together a rig that I can use to consistently measure the output profiles of my basses. I'm no expert on it, but I think the way to go (in our kind of budgets!) is find some decent software that makes a PC into a spectrum analyzer, in conjunction with a good quality audio input box or card. I did some digging a while back and there were several reasonably priced spectrum analysis software packages available. Does anyone have any experience/opinions with them?

[belwar]

I'm quite interested in this subject too. I'd like to put together a rig that I can use to consistently measure the output profiles of my basses. I'm no expert on it, but I think the way to go (in our kind of budgets!) is find some decent software that makes a PC into a spectrum analyzer, in conjunction with a good quality audio input box or card. I did some digging a while back and there were several reasonably priced spectrum analysis software packages available. Does anyone have any experience/opinions with them?

I'm slowly working on a write up on how to measure resonance frequency. It wasn't as hard as I thought it would be once I figured it out. Before I do the write up though, I need to understand what im looking at. I bought an old 1960's audio oscillator off of E-bay for 60 bucks and my DMM has frequency.

Joe Gwinn was my hero in this - He helped me alot and now I want to give that good will back to others.

[Peter Naglitsch]

I just came across a piece of software called Multi-Instrument 3.0 which uses your computer soundcard and two probes. Aparently you can use it as a signal generator, osciliscope, AND LCR meter.

Anyone care to check it out?

I missed this thread when it was first up.

I have used the virtins multiinstrument 2.something for some time now. What it all comes down to is the driver coil you use. I had to redo the driver coil a few times and still isn't 100% satisfied. The curve the frequency analyzer shows are a combination of the output curve from the driver coil and the response of the pickup being measured. In the end it all comes down to learning to use your equipment. I have learned to recognize what part of the curve is the driver coil and what part is the actual pickup being measured. Then I subtract (in my head while viewing) the effect of the driver coil.

I know that there were a thread on driver coils and analyzers a while ago, but I cannot find it right now... Might be interesting to compare what people use for drivers.

[Joe Gwinn]

I missed this thread when it was first up.

I have used the virtins multiinstrument 2.something for some time now. What it all comes down to is the driver coil you use. I had to redo the driver coil a few times and still isn't 100% satisfied. The curve the frequency analyzer shows are a combination of the output curve from the driver coil and the response of the pickup being measured. In the end it all comes down to learning to use your equipment. I have learned to recognize what part of the curve is the driver coil and what part is the actual pickup being measured. Then I subtract (in my head while viewing) the effect of the driver coil.

I know that there were a thread on driver coils and analyzers a while ago, but I cannot find it right now... Might be interesting to compare what people use for drivers.

The inductance of the driver coil causes the current and thus magnetic field to drop as the frequency is increased. A series resistor having at least five times the resistance of the coil's reactance at the highest test frequency should swamp the inductance effects and cause the driver coil effects to vanish.

The drive coil should not be wound as a pickup coil, which will have too many turns and thus too much inductance and too low a self-resonant frequency.

For example, consider a coil having an inductance of 0.01 H. At 10 KHz, the reactance will be 2*Pi*10000*0.01= 628 Ohms. Five times this is 3.14 K, so use 3 K or 3.3 K. Or 10 Kohms. Great precision is not required.

[salvarsan]

Resonance peak and how to get it

First, you spend more $%^&! money on insufficiently accursed measurement tools.

Then you post impedance+phase plots on the forum, like this:

http://music-electronics-forum.com/showpost.php?p=95974

-drh

[Bruce Johnson]

Instead of a driver coil, how about making up a mechanical device which made a piece of steel wire (simulating the string) vibrate at a controllable frequency and amplitude over the pickup. You'd set this device at particular frequencies and record the output of the pickup with a spectrum analyzer (freq vs amplitude). Assuming that you could make the device and test setup consistent and repeatable, wouldn't this be the best way to compare pickups? I realize that there is no single, simple answer here. It's all about establishing some standard test procedure, and then using it consistently to find differences.