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Teunos
Old Croc Joined: 23 November 2008 Location: The Netherlands Status: Offline Points: 1799 |
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Premium quality build, keep up the good work and thanks for taking the time to post pictures.
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Best regards,
Teun. |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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did some outdoor measurements today
except red all are 2.83 volts into nominal 4R load (2 8R drivers in parallel) 1/3 octave smoothing
blue and purple are 1m on axis and 1m rear (20cm behind 80cm deep box). speaker lying on its largest side. mic on small stand approx 10cm from ground. green is average of blue and purple plus two other off axis measurements so should be an approximate power response - all taken at 1m though so maybe underestimate orange is average of two 1m measurements of speaker pointing toward ground but spaced up on bricks 22cm from ground red is 28.3V at 10m on axis -3dB seems to be about 60Hz. upper roll off is better than predicted. rear access hatch is currently 12mm ply with a couple of braces. using 12mm aluminium might change the q of the rear chamber a bit and improve the low end. |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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forgot to take many more build pics. here is one of the rear chamber. very well braced now with aluminium to mount the battery for portable system use. battery just fits with 2mm clearance. If I rejigged things a bit could get the amplifier in the rear chamber too, mounted on the rear access hatch. |
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imageoven
Old Croc Joined: 28 March 2007 Location: Scotland Status: Offline Points: 2186 |
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What is the battery / amp set up (proposal)? - sorry if Ive missed this. |
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Keep pushing on, things are gonna get better.
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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Interesting sets of measurements, but I’d suggest caution before reading too much into the data. From quite a lot of experience with ‘similar’ boxes and horns in general, you’re measuring too close to be getting reliable data. The radiating area is quite large in relation to the distance of the mic, and you’re likely still ‘inside the horn’ acoustically. 10 meters is ideal but 4 meters is also sufficient in most real world circumstances, and has the benefit of being easy to compensate back to a 1 meter level via extra drive voltage or simple inverse square law maths. A quick check for this is the blue and purple traces. If you’ve actually managed to achieve a 10 dB front to rear rejection when equitemporal/equidistant from the acoustic centre, then you’re beating the full size product that inspired you - and some cardioid designs - by quite some margin. Have you tried covering the ports to determine their influence on the overall response? The shift in rolloff shape at the low corner for the red trace might indicate that the ports are creating some phase cancellations. The good news is that I would expect better results i than you’ve got even now, and you can likely ditch the 1/3 smoothing as there’ll be fewer ripples in the response to boot. Edited by toastyghost - 29 July 2021 at 1:21am |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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Banda Elite 4000.4 amp Sterling 120Ah lithium battery final system will include Waves Maxxbass 103 to simulate some sub-bass content t.racks DSP 4x4 Mini for crossover.
Edited by snowflake - 29 July 2021 at 2:43pm |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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I haven't turned it into a ported horn yet. wanted to measure it a flh and possibly as a mass-loaded horn first and then compare the addition of the ports. I did one measurement at 28.3V @10m and would like to do them all like that but we heard shouts of "what the f*** was that from other people in the park". Maybe 11.3V @ 4m (+12dB) won't cause too much commotion. don't know why I didn't try without the 1/3 smoothing will also try and get some battery current readings playing some music material.
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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more measurements shown with 1/48th smoothing:
cyan 28.3V 10m measurement from yesterday green 11.3V@4m on axis blue power response average of eight polar measurements red average of two measurements with speaker facing down at ground. orange 11.3V@4m 180 deg off axis - this is the measurement that changed very significantly and the front to rear rejection @100Hz is therefore closer to 6dB than 10dB taking average power response as 107dB it is 3dB down at 55Hz and 330Hz
Edited by snowflake - 30 July 2021 at 12:06pm |
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fat_brstd
Old Croc Joined: 23 August 2008 Location: Melbourne, OZ Status: Offline Points: 2126 |
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Looking great, how does it sound around the 200hz region? Any honkiness or is nice and smooth?
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Melbournes Rootical Warrior Roots - Dub - Steppers facebook page |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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sounds pretty good. listened to some motown stuff and even with it crossed at 300Hz the vocals didn't sound too muddy. this is the on axis distortion plot with 28.3V |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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SPL and phase
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3121 |
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group delay with 1/3 smoothing
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