I've done some reading on the WM-61A.
The problem is most preamp schematics suggested for it for it are only good til 110dB or 118dB.
How do you measure louder signals?
What is the simplest way to measure relative SPL dB?
For example, measuring the SPL of a speaker at 40hz, then measuring the SPL at 50hz. If one is x the other is y, I just want to know for example, y is 5dB more than x. or the 40hz signal is 80dB above my silence measurement.
So I'm thinking I just need a linear mic like the panasonic WM-61A and a computer with speakerworkshop running on it? or some RTA?
Then possibly a preamp?
The problem is most preamp schematics suggested for it for it are only good til 110dB or 118dB.
How do you measure louder signals?
What is the simplest way to measure relative SPL dB?
For example, measuring the SPL of a speaker at 40hz, then measuring the SPL at 50hz. If one is x the other is y, I just want to know for example, y is 5dB more than x. or the 40hz signal is 80dB above my silence measurement.
So I'm thinking I just need a linear mic like the panasonic WM-61A and a computer with speakerworkshop running on it? or some RTA?
Then possibly a preamp?
Radio Shack (Tandy in some parts of the world) has an inexpensive meter if you want to measure actual SPL.
A measurement system like speaker workshop is not meant for measuring high SPL. In order to do that, you need a SPL meter.
You can make an SPL meter, but probably not for what the shack sells them for.
A measurement system like speaker workshop is not meant for measuring high SPL. In order to do that, you need a SPL meter.
You can make an SPL meter, but probably not for what the shack sells them for.
here is usefull info how to midify radio shack to be more accurate fo low frequencies:
http://forum.audiogon.com/cgi-bin/fr.pl?htech&983682086&openfrom&3&4
http://forum.audiogon.com/cgi-bin/fr.pl?htech&983682086&openfrom&3&4
I imagine this info is from Eric Wallin's extensive work on the various RS meters, so there may be some more info here: http://mysite.verizon.net/tammie_eric/audio/audio.html
Also: http://www.hometheatershack.com/for...strange-rs-spl-meter-calibration-results.html
GM
Also: http://www.hometheatershack.com/for...strange-rs-spl-meter-calibration-results.html
GM
This post from gaetan8888 shows the schematics for the Radio Shack digital (2055) and analog meter (2050):
http://www.diyaudio.com/forums/swap...-sound-level-meter-33-2050-a.html#post4524368
It appears that the main problem is the woefully low value coupling capacitors.
http://www.diyaudio.com/forums/swap...-sound-level-meter-33-2050-a.html#post4524368
It appears that the main problem is the woefully low value coupling capacitors.
the wm61A can handle a lot more mechanically. all the distortion is generated by the jfet and mostly it's non linear gate drain diode.
by bootstrapping the drain, and setting the fet in source follower mode by not loading it, (bootstrapping load impedancr as well) the fet keeps operating at constant voltages.
I built various mikes this way and they all calibrated the same sensitivity of 14mV/Pa. I used the behringer mike as a case. it turned out a classI mike as well
by bootstrapping the drain, and setting the fet in source follower mode by not loading it, (bootstrapping load impedancr as well) the fet keeps operating at constant voltages.
I built various mikes this way and they all calibrated the same sensitivity of 14mV/Pa. I used the behringer mike as a case. it turned out a classI mike as well
How about making the measurment at 10m and adding the 10db loss?
That's how I do it using the rat shack.
At that distance your measuring the difference in room modes at different freqs not the speaker. (Unless you do it outside. ).
There are free apps for most smart phones you can try out for.... free. I have one from rta audio that does 20hz
Cross·Spectrum - Galaxy CM-140 Sound Level Meter
I have not gone through them, yet. I was going to see if they could calibrate the mic I already bought from PE, and I think I need an SPL meter as well.
I know you said cheap. But how accurate is cheap?
I have no clue how to calibrate an SPL meter... So I am useless...
You can look into sound level calibrators...
http://www.testequipmentdepot.com/bk-precision/accessories/cal73.htm?utm_source=bing&utm_medium=cpc&utm_campaign=Bing%20Product%20Ads&utm_term={QueryString}
and ebay...
http://www.ebay.com/sch/i.html?_nkw=sound+level+calibrator
If you use REW, you can use any calibrated mic for frequency, then use the calibrator to make sure your mic is dead on as far as SPL... (yeah, they are expensive, at least 200 bucks)
I use HOLM, and don't worry about measured SPL right now. I just measure the frequency response of each driver to check relative levels with same volume setting at crossover point... So I can't help you with true SPL response...
I have not gone through them, yet. I was going to see if they could calibrate the mic I already bought from PE, and I think I need an SPL meter as well.
I know you said cheap. But how accurate is cheap?
I have no clue how to calibrate an SPL meter... So I am useless...
You can look into sound level calibrators...
http://www.testequipmentdepot.com/bk-precision/accessories/cal73.htm?utm_source=bing&utm_medium=cpc&utm_campaign=Bing%20Product%20Ads&utm_term={QueryString}
and ebay...
http://www.ebay.com/sch/i.html?_nkw=sound+level+calibrator
If you use REW, you can use any calibrated mic for frequency, then use the calibrator to make sure your mic is dead on as far as SPL... (yeah, they are expensive, at least 200 bucks)
I use HOLM, and don't worry about measured SPL right now. I just measure the frequency response of each driver to check relative levels with same volume setting at crossover point... So I can't help you with true SPL response...
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Loudspeakers
- Subwoofers
- cheap SPL meter for subwoofers