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Teunos View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2021 at 3:56pm
Premium quality build, keep up the good work and thanks for taking the time to post picturesSmile.
Best regards,
Teun.
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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2021 at 11:31pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2021 at 11:43pm
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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote imageoven Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 12:32am
What is the battery / amp set up (proposal)? - sorry if Ive missed this.


Keep pushing on, things are gonna get better.
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toastyghost View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 1:16am
Originally posted by snowflake snowflake wrote:

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.




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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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 8:53am
Originally posted by imageoven imageoven wrote:

What is the battery / amp set up (proposal)? - sorry if Ive missed this.



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 View Drop Down
Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 9:07am
Originally posted by toastyghost toastyghost wrote:

Originally posted by snowflake snowflake wrote:

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.




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.

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 View Drop Down
Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2021 at 9:34pm
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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fat_brstd Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2021 at 12:57am
Looking great, how does it sound around the 200hz region? Any honkiness or is nice and smooth?
Adrians Wall Sound System
Melbournes Rootical Warrior
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snowflake View Drop Down
Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2021 at 11:59pm
Originally posted by fat_brstd fat_brstd wrote:

Looking great, how does it sound around the 200hz region? Any honkiness or is nice and smooth?

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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2021 at 12:02am
SPL and phase


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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2021 at 12:06am
group delay with 1/3 smoothing


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