Hi Oliver,
Quote: "The pressure chamber is also interesting for DIY-er. Under the premise that the chamber was once calibrated with a reference microphone, it is no problem, due to its small dimensions, to set the chamber up to calibrate any microphone in frequency response and level.................. Theoretically, for good sealed enclosure, a calibration of a microphone frequency response can be done without the comparison with a reference mic"
Theoretically that is correct
but:
A) You still need a high quality reference to calibrate the pressure chamber
B) The driver needs to be powered with a precision of 0.010V (RMS) which involves expensive equipment that most people don't have.
C) Drivers do change over time so how often do you need to recalibrate?
(Btw the Monacor MCE 2000 uses a Panasonic capsule)
Quote: "The pressure chamber is also interesting for DIY-er. Under the premise that the chamber was once calibrated with a reference microphone, it is no problem, due to its small dimensions, to set the chamber up to calibrate any microphone in frequency response and level.................. Theoretically, for good sealed enclosure, a calibration of a microphone frequency response can be done without the comparison with a reference mic"
Theoretically that is correct
but:A) You still need a high quality reference to calibrate the pressure chamber
B) The driver needs to be powered with a precision of 0.010V (RMS) which involves expensive equipment that most people don't have.
C) Drivers do change over time so how often do you need to recalibrate?
(Btw the Monacor MCE 2000 uses a Panasonic capsule)
Hi Djim,
I just thought you might find it interesting (Post #217). For getting absolute values you are correct in your criticism, but, for relative values, i.e.: to determine the fall-off of a given microphone below 150 Hz, this would be a great tool to have, and it wouldn't be very critical at all.
Regards,
I just thought you might find it interesting (Post #217). For getting absolute values you are correct in your criticism, but, for relative values, i.e.: to determine the fall-off of a given microphone below 150 Hz, this would be a great tool to have, and it wouldn't be very critical at all.
Regards,
Good, but not quite as good as the B&K 4004 rated +/- 2dB from 10Hz to 40kHz
.That said, I generally use a much cheaper measurement mic.
At any rate, unless your measurement mic drops like a rock in the vicinity of the speaker F3 point (as some examples previously show do) probably not worth a lot of money to chase the ultimate.
Art
Hi Oliver,
Maybe it is interesting for developing a relative cheap calibration tool by integrating a small amp that is connected to a standard Digital to Analog converter based on USB connection, which gets driven by a simple sinus program. That way it can become an easy calibration tool for your mic (reference dB point) anywhere below 100Hz and give a mic response plot. The error rate could be made smaller than 1dB between 5Hz and 100Hz if a small correction eq is integrated in the software.
Question is, would there be a market for such tool that would cost around the 250 dollars?
Maybe it is interesting for developing a relative cheap calibration tool by integrating a small amp that is connected to a standard Digital to Analog converter based on USB connection, which gets driven by a simple sinus program. That way it can become an easy calibration tool for your mic (reference dB point) anywhere below 100Hz and give a mic response plot. The error rate could be made smaller than 1dB between 5Hz and 100Hz if a small correction eq is integrated in the software.
Question is, would there be a market for such tool that would cost around the 250 dollars?
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Good idea, but most would prefer to pay someone a fraction of that amount to make a deviation chart for their mic, or pay for a better quality mic that comes with a chart, so I think the idea has limited commercial appeal.Hi Oliver,
Maybe it is interesting for developing a relative cheap calibration tool by integrating a small amp that is connected to a standard Digital to Analog converter based on USB connection, which gets driven by a simple sinus program. That way it can become an easy calibration tool for your mic (reference dB point) anywhere below 100Hz and give a mic response plot. The error rate could be made smaller than 1dB between 5Hz and 100Hz if a small correction eq is integrated in the software.
Question is, would there be a market for such tool that would cost around the 250 dollars?
My favorite measurement tool was a Hall Engineering ATG-301, which consisted of a dB meter with a deviation chart and a sweepable finite-bandwidth pink noise generator with a 20-20K frequency range in bandwidths from 1 to 1/20th of an octave.
I probably only paid $250 for the set , unfortunately it was stolen (along with $150K of sound and lighting equipment) but would pay a lot more to have a similar tool again. Even with Smaart and RTAs, I really miss that hand sweepable pink nois generator, and can’t seem to find anything similar.
The ATG-301 was made in the 1980’s, 20 Hz was lower than almost any speaker’s response then, now I’d want a unit to be calibrated down to a few Hz...
Art
Hi Art,
That’s why I asked the question in the end. The difference with a supplied chart is that you still have no reference to adjust to in a real measuring setup. A 'normal' pistonphone is often used for calibrating to 94dB at the usual frequency of 250Hz (they cost more than 500 dollars). The instrument I described would be able to deliver any level between 80dB and 140dB at any frequency spot between 5Hz and 100Hz within accuracy of 1dB.
Practically, that means you can calibrate any measuring setup within the same level range you are going to measure. Do you think that is worth the extra investment?
That’s why I asked the question in the end. The difference with a supplied chart is that you still have no reference to adjust to in a real measuring setup. A 'normal' pistonphone is often used for calibrating to 94dB at the usual frequency of 250Hz (they cost more than 500 dollars). The instrument I described would be able to deliver any level between 80dB and 140dB at any frequency spot between 5Hz and 100Hz within accuracy of 1dB.
Practically, that means you can calibrate any measuring setup within the same level range you are going to measure. Do you think that is worth the extra investment?
Well, I think we can argue if the B&K is really better. Above 24kHz yes. But between 20Hz and 20kHz it is worse (+/- 2 dB compared to +/-1dB for the sofsci). Between 10-20Hz they are the same. Sounds more useful to me.Good, but not quite as good as the B&K 4004 rated +/- 2dB from 10Hz to 40kHz
That said, I generally use a much cheaper measurement mic.
At any rate, unless your measurement mic drops like a rock in the vicinity of the speaker F3 point (as some examples previously show do) probably not worth a lot of money to chase the ultimate.
Art
Never the less, I had the opportunity to borrow a second ECM8000 from another friend (beacuse of the discussion about the quality and reliability of the calibration file). I know it is far from the perfect test, but at least I found it interesting. I just swapped mic during the test (nothing change at all, not even wiring) and captured two plots.
To me, they look VERY similar. Strangely enough the level seems to be a bit different, but the graph is very similar for sure.
The Kraken's are a bit more integrated in my environment now
Added a front for the openings to make it more "stealth".
I have the sofsci measurement stuff now (+-2db 10-20 Hz, +-1db 20-20kHz) so I will be posting a more "correct" freq response shortly.
These horns are amazing. That the deep base could rumble a lot of things I understood, but the quick, clean and tight base for music surprised me.
Added a front for the openings to make it more "stealth".
I have the sofsci measurement stuff now (+-2db 10-20 Hz, +-1db 20-20kHz) so I will be posting a more "correct" freq response shortly.
These horns are amazing. That the deep base could rumble a lot of things I understood, but the quick, clean and tight base for music surprised me.
wiring the 2 JBLs
My stereo amp QSC GX3 can handle 4 ohm each channel. Can I split the sub signal (mono) and wire it to the L/R inputs on my amp and wire each amp output to each of the JBL making sure they are wired 180 degree out of phase? Would that effect be the same thing as wiring the 2 JBLs in parallel and having a muscle amp to handle the 2 ohm?
Thanks
My stereo amp QSC GX3 can handle 4 ohm each channel. Can I split the sub signal (mono) and wire it to the L/R inputs on my amp and wire each amp output to each of the JBL making sure they are wired 180 degree out of phase? Would that effect be the same thing as wiring the 2 JBLs in parallel and having a muscle amp to handle the 2 ohm?
Thanks
Fredrik,
Farther back in the thread is the single 12" version of the subwoofer. It requires one JBL GTO 1214 sub ($100) two sheets of 4 x 8 foot 3/4" (18mm) plywood ($75) screws, glue and input terminals ($20) The single 12" version would run you around $200 American so the dual 12" would be around $400.
Farther back in the thread is the single 12" version of the subwoofer. It requires one JBL GTO 1214 sub ($100) two sheets of 4 x 8 foot 3/4" (18mm) plywood ($75) screws, glue and input terminals ($20) The single 12" version would run you around $200 American so the dual 12" would be around $400.
No, 142kg was not not a typo. It was quite heavy to carry into place
I guess you have seen my thread on the kraken on faktiskt.se? Contains more information and listening impressions and more measurements. http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&t=47472
When it comes to price I payed about 1300-1500sek for material (precut and ready) 22mm MDF per horn.
Drivers are about 1000-1100 sek each in Sweden (I bought one pair from UK for about 700 sek each but they are not available from there anymore).
If you are in the Sthlm area you are welcome to come try them out
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