Good point. The test is simple an does not take into account EQ. If you have a boost somewhere then your voltages at that frequency will be higher. Your 30Hz boost will need about 4.5X more voltage than you measured.
Conversely, if you had a cut at 120Hz or 220Hz, your readings would be off.
Bill, thanks for your results and the good info. I'm surprised about the interaction with the meter, what type is it?
It probably isn't, but it does not matter. Here's why:
Once you have set your level, it's set. Because digital playback has an absolute maximum level (a ceiling) we know the voltage can never go higher than that.
The test signal is 12dB lower than that ceiling. So the max voltage possible is 4X what you measure from the test tone. Make sense?
However, if you wanted to know the average level, then matching the test tone to the music is important. Looking at a lot of recordings, I see that most loud sections have an average level of -10dB to -12dB. Of course they aren't all like that, but those levels are typical. And that's one of the reasons I chose -12dB for the test signals.
If you have software like Goldwave, you can open the music file and read its average level. Read the whole file, or just a selected part of it. Very handy tool.
Results
9.42 VAC @ 120 Hz, 8.99 VAC @ 220 Hz.
Carver TFM-15CB driving my DIY MTM, dual 6.5", Four Ohm, Trick Piezo.
Room size 5M by 5.5M.....A rather "live" room, ceramic floor, cemented walls, no particle board nor drywall ..........A decent volume, turned up just shy of onset of distortion harmonics.
________________________________________________________Rick.......
9.42 VAC @ 120 Hz, 8.99 VAC @ 220 Hz.
Carver TFM-15CB driving my DIY MTM, dual 6.5", Four Ohm, Trick Piezo.
Room size 5M by 5.5M.....A rather "live" room, ceramic floor, cemented walls, no particle board nor drywall ..........A decent volume, turned up just shy of onset of distortion harmonics.
________________________________________________________Rick.......
Last edited:
This kind of test needs a voltmeter with a voltage-peak-hold function (I own four having it...) connected across the driver or the loudpseaker and some records having modulation peaks reaching the full scale deviation (FSD).
Yesterday, I discovered this program
ocenaudio
It can provide statistics on a record :
Peak amplitude; Minimum, Maximum and Average levels in dB (awfully called "Powers").
From there, you can obtain a lot of informations about the voltages applied to your speakers, if they may ever suffer from thermal compression, if your amplifiers ever clip, etc...
This could help to extend this disccussion which deserves it :
http://www.diyaudio.com/forums/solid-state/133168-amplitude-frequency-distributions-wanted.html
Yesterday, I discovered this program
ocenaudio
It can provide statistics on a record :
Peak amplitude; Minimum, Maximum and Average levels in dB (awfully called "Powers").
From there, you can obtain a lot of informations about the voltages applied to your speakers, if they may ever suffer from thermal compression, if your amplifiers ever clip, etc...
This could help to extend this disccussion which deserves it :
http://www.diyaudio.com/forums/solid-state/133168-amplitude-frequency-distributions-wanted.html
Last edited:
Using musical signals, knowing peaks and average voltages applied to the amplifiers and loudspeakers (and drivers in multiways) gives a larger and more detailed picture of the whole than measuring volts of continuous low frequency sinewaves according to the proposed test procedure. I think that the peak hold function can now be found on some low cost multimeters.
I find 110 dB of LF adequate in my living room, and don't have room for a 45 x 22.5 x 26.5 speaker, and my Technics tuner sub output can probably only do 30 volts or so.
The rather efficient (around 101 dB 1 watt 1 meter) Keystone tapped horn sub has been duplicated by PASC, he is considering replacing his present subs in his home stereo with that speaker.
Lots of people get used to 120 dB of bass in car and concert systems and want to reproduce that in the home, without cabin gain it takes a lot of horsepower to do it.
The 120V test was done in my shop in an area around 20 x 16 x 9, and was off scale (over 126 dB) on my dB meter at one meter. I actually don't find 130 dB at 30-40 Hz peaks uncomfortable, though I don't listen above 110 dBC, 90 dBA in my home stereo.
My shop seems to saturate around 120 dB at low frequencies if listening in the middle portion, increasing voltage does not increase level after a point.
Wobbly walls and phase cancellation.
Of more usual home stereo interest, the Acoustic Research AR2 at 10.9 volts was pretty anemic, only about 100 dB at one meter, a pair in my shop (or living room) may have done about 95 dB maximum at normal listening distance.
I think the AR2 was a 4 ohm speaker with a 87 dB rating, 10.9 v is around 30 watts, and that was as much as it could take without exceeding 10% distortion at low frequencies.
They definitely ran out of gas below levels I like with some types of bass heavy music.
Art
Unfortunately, the integration time on multimeters is far to slow to read musical peaks with any detail or accuracy.
LOL
Thanks for posting.
I agree. It would be nice if you could do this, but I would not trust the meter on music. An Oscilloscope, yes.
However: If you think you need to measure peak values, you have missed a fundamental part of the test. We already know where the peaks are, they are 12dB higher than the test tone. That's 4X the voltage. Where else could they be?
The test tone could be at any other level, as long as you know what that level is, you know where the peaks will be.
Thanks Brett. Hard to say from that, but I might put you right at 2V for the -12dB.
If 6V rms is as loud as you ever want it, then that would be 8.5V peak. Drop that down 12dB and you're at 2.12 volts. Ballpark, anyway.
I hope that some more of you get a chance to do the test this weekend. It's nice to know all the different configurations and voltage ranges out there.
If 6V rms is as loud as you ever want it, then that would be 8.5V peak. Drop that down 12dB and you're at 2.12 volts. Ballpark, anyway.
I hope that some more of you get a chance to do the test this weekend. It's nice to know all the different configurations and voltage ranges out there.
That's the loudest I could stand being near them with a tone, which I would equate to an average level for dynamic content. Peaks could easily exceed that by 20dB and still be bearable, providing the system is still within it's linear range.
See Bob Cordell's dynamic content and power tests to get what I mean.
Yeah, hard to say and it depends on the tone. I can stand a lot louder tone at 220Hz than at 1000Hz, that's for sure! But I do find that I can play music at a higher average level than most tones, so agree with you. Just hard to say. Do you think that puts you in the 5-10V range, then?
My peak-hold capable multimeters are three Metrix MX57EX ASYC II and a Fluke 867. The Metrix can detect peaks of duration below 1/100000 s.
An externally hosted image should be here but it was not working when we last tested it.
With a standard multimeter for calibration at 200 Hz, using a sound card, a stepped attenuator, recording and analysis software, it may certainly be possible to do a very fine analysis of what goes really to your speakers.