Cubo15ext, measured
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=104010
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Topic: Cubo15ext, measured
Posted By: Tonskulus
Subject: Cubo15ext, measured
Date Posted: 15 July 2019 at 5:17pm
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Finally managed to do some outdoor measurements. Cubo 15 extended, RCF L15P540, magnet in horn
Ground plane. One nearby wall at one side 5meters away, which might affect a little. test equipment: Calibrated Umik-1 microphone, Room Eq Wizard. No EQ except 30Hz highpass and 200Hz lowpass (48dB). Results:  Green: 20Volts / 1m Blue: 20Volts / 2m Red: 1W/2.83V/ 1m For comparsion, Orange: CerwinVega 12inch in ported enclosure (vegaline 12, 4ohms). 2.83V / 1m. Will do some more at longer distances + magnet in chamber. Some Eq added, driven to the max (around 30-50Volts rms), 1 meter max continuous SPL.  |
Replies:
Posted By: Timebomb
Date Posted: 15 July 2019 at 8:01pm
 Your measurements look much better than simulations, possibly a little too good, was SPL calibrated with calibrator, or off the frequency response calibration file? Would be interested to see some results at longer distances, a wall 5 meters away will definitely affect your measurements, i use a football field as it is big and flat with no building for 70 meters or so. ------------- James Secker facebook.com/soundgearuk James@soundgear.co.uk www.soundgear.co.uk |
Posted By: toastyghost
Date Posted: 15 July 2019 at 8:31pm
| You also kind of should measure at 4m minimum from the cabinet to ensure you’re getting accurate data for subs. |
Posted By: Tonskulus
Date Posted: 15 July 2019 at 9:25pm
Im using calibration file. I only changed sensitivity factor and mic gain to 0dB (there are dip switches inside the mic for gain adjustment) for measuring up to 130dB. At 1meter, cubo 15 can peak over 130dB. It happened when I accidentally measured @ 50-60volts so I had to back off a little to get full response curve. For sure I will make more measurements, further away from buildings! Thats why I measured 12" subwoofer in the same spot, there has to be something for comparsion. As well as some other subwoofers like hog-scoops etc.. |
Timebomb wrote:Posted By: Timebomb
Date Posted: 16 July 2019 at 8:32am
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Look forward to seeing your results :) Yeah 11.3V at 4 meters, 22.6V at 8 meters, or 28.3V at 10 meters in a big flat opens space (with no wind ;) ) would give better results. The spl does look high for that cabinet, the spl calibration that came with UMM-6 USB measurement mic was not correct, i cant remember if it was high or low but when i checked it with a calibrator it was off, if you can buy or borrow a calibrator then you can change the .text file and then get spl calibration back on, the best way is to calibrate just before you take the measurement though, its pretty easy in room eq wizard. I think its definitely worth checking. ------------- James Secker facebook.com/soundgearuk James@soundgear.co.uk www.soundgear.co.uk |
Posted By: Tonskulus
Date Posted: 16 July 2019 at 8:37am
Well, I checked SPL with JBL 2445J+2380A horn. Specs says 112dB/1W/1m.. I got 111dB so I think its not that far off. Also, SPL for 12" cerwinvega looks pretty much normal as it should. Anyway, 125-130dB @ 60...80Hz is not magic from single 15" in proper enclosure. |
Posted By: odc04r
Date Posted: 16 July 2019 at 9:05am
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All looks pretty reasonable to me, I agree that your numbers are in the expected ballpark for the enclosure and the typical rising response is there. Don't suppose you took impedance mag/phase also? |
Posted By: Tonskulus
Date Posted: 16 July 2019 at 9:39am
I do have equipments for measuring impedance curve / ts parameters, will measure them too asab. There is huge dip around 220Hz, exactly the same as can be seen on some cubo 15 simulations. I think its phase cancellation beetween the cone and horn. Horn length is about 80-100cm, 200Hz wave length is right there. Not a problem in practice because upper limit for cubo is around 100Hz anyway. Above that, it sounds really honky. 40-110Hz enclosure it is, if you ask me :) |
Posted By: odc04r
Date Posted: 16 July 2019 at 11:39am
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Yeah, the cancellation dip should be approximately the path from back to front of driver one would expect. I'll give you 45-100Hz bandwidth  Would be interesting to see how the impedance measured compares with predicted model, that should give you another strong piece of information about reality vs simulated. If you have a way to pad down the amplifier output to keep it in the headroom of your soundcard then impedance at large signals might also give you clues about the resonances that creep in with more power. |
Posted By: Tonskulus
Date Posted: 16 July 2019 at 12:05pm
My rig has both options for measuring small- and large signals (well, not at max power but around 10-20watts at least is possible). Need to look for simulations of cubo15extended w/L15P540 too.. |
Posted By: Elliot Thompson
Date Posted: 17 July 2019 at 1:12pm
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It is good to see you took the time to measure your design. It will put you in a different league than those who only use simulations as their means of identifying the frequency response. As you can see, simulations are not accurate as they may appear. As you focus more into the measuring side of loudspeakers, the more you will gravitate away from simulations. If you ever choose to
measure your cabinets again, do not use any high pass/low pass
filtering. Filtering alters the measured frequency response. If you
sweep 20 Hz – 200 Hz without filtering, you will have better
un-bias report. Based on the single cabinet results, the cabinet is the limitation why you were encountering excursion issues with the RCF L 15 P 540. I would recommend measuring the TS Parameters of the RCF L 15 P 540. The better understanding you have of your design, the lower the chances of having any surprise accidents when operating your loudspeakers.
Best Regards, ------------- Elliot Thompson |