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Full Range TC9 Line Array CNC Cabinet
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Old 28th May 2017, 09:41 PM   #521
stardust4ever is offline stardust4ever  United States
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Quote:
Originally Posted by fluid View Post
I'm a bit confused as to what you are referring to, the image you quoted is Byrtt's with a 192kHz sample rate, that makes it a little harder to compare to mine at 48K.

Moire patterns is a video term to describe one form of aliasing, there are no 44 to 48 conversions in the loopback tests so I am a bit confused as to what you mean.
The graph with the 24kHz ringing showed the waveform amplitude cresting and falling several times before fading away. This is representative of what happens when two tones with nearby frequencies are mixed, creating an amplitude pattern that rises and falls according to constructive and destructive interference.

In fact there is a musical instrument known as a theremin that uses the constructive and destructive interference between two RF waveforms at different frequencies to create a musical tone (absolute value sine wave) from the interference.

I have uploaded an audacity screenshot showing the result of adding a 2205Hz and 2400Hz waveform. The graph I referenced had evidence of two independent ringing frequencies which constructively and destructively combined resulting in the waveform. So the amplifier rang at two distinct frequencies which had roughly the same decay time, possibly a result of combining the left and right channels together.

I dunno really. The fact the ringing exists wholly in the ultrasonic domain means it shouldn't matter as far as listening is concerned.
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Last edited by stardust4ever; 28th May 2017 at 09:51 PM.
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Old 29th May 2017, 02:32 AM   #522
fluid is offline fluid  Australia
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Quote:
Originally Posted by stardust4ever View Post
The graph with the 24kHz ringing showed the waveform amplitude cresting and falling several times before fading away. This is representative of what happens when two tones with nearby frequencies are mixed, creating an amplitude pattern that rises and falls according to constructive and destructive interference.

In fact there is a musical instrument known as a theremin that uses the constructive and destructive interference between two RF waveforms at different frequencies to create a musical tone (absolute value sine wave) from the interference.

I have uploaded an audacity screenshot showing the result of adding a 2205Hz and 2400Hz waveform. The graph I referenced had evidence of two independent ringing frequencies which constructively and destructively combined resulting in the waveform. So the amplifier rang at two distinct frequencies which had roughly the same decay time, possibly a result of combining the left and right channels together.
I think I see what you are saying. In Byrtt's graph at 192K it might look like that but the shape of the ringing is divided by the peak into pre and post ringing, the shape is only relevant if it appears either before or after not separated by the peak.

In my Scarlett graph and in Byrtt's UMC graph the post ringing does show that same pattern. Hard to say why that is as there was no sample rate conversion or mismatch involved.

Quote:
I dunno really. The fact the ringing exists wholly in the ultrasonic domain means it shouldn't matter as far as listening is concerned.
Apart from curiosity to understand the process better a little bit of ultrasonic ringing shouldn't be a problem.
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Old 29th May 2017, 07:08 PM   #523
suzyj is offline suzyj  Australia
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Originally Posted by xrk971 View Post
OPC,



Here are the simulations of the cone displacements for a 2L rear chamber per driver, with 9V (parallel) and 45v (series) with stuffing in rear chamber.

SERIES:
Click the image to open in full size.

PARALLEL:
Click the image to open in full size.
This is an intriguing result. It makes a strong argument for multiple low power amplifiers to drive two or three parallel connected drivers, or perhaps a 2s/2p at the most, in order to maintain better control the voice coils.
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Old 29th May 2017, 07:40 PM   #524
xrk971 is online now xrk971  United States
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Full Range TC9 Line Array CNC Cabinet
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Originally Posted by suzyj View Post
This is an intriguing result. It makes a strong argument for multiple low power amplifiers to drive two or three parallel connected drivers, or perhaps a 2s/2p at the most, in order to maintain better control the voice coils.
Hi susyj,
Yes, I never would have thought the differences would be so great until I ran the sim. It was Wesayso who urged me to run the sim. In reality, we probably won't hear much of this because the cones are flapping about in their linear range. It's when you start pushing power through them and some may be hitting xmax or beyond. There will be more distortion on the cones moving more of course. On a a line array with 25 drivers may be less noticeable than a single. But I the quality of the overall I integrated sound in distortion and phase space may not be consistent. Even if we can't easily hear the difference. It does say to choose parallel over series. And ideally a single amp for each set in series. Here is where 16ohm drivers like Faital Pro 3FE22 are handy.
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Old 30th May 2017, 07:00 AM   #525
fluid is offline fluid  Australia
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Originally Posted by xrk971 View Post
Yes, I never would have thought the differences would be so great until I ran the sim. It was Wesayso who urged me to run the sim. In reality, we probably won't hear much of this because the cones are flapping about in their linear range. It's when you start pushing power through them and some may be hitting xmax or beyond. There will be more distortion on the cones moving more of course.
As this simulation of pure parallel vs series has the greatest variation around the Fs of the drivers it would be interesting to see if the conjugate impedance flattening circuit that wesayso uses reduces the variance, while a little more work to put the components in the simulation it could be a useful data point.
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Old 30th May 2017, 07:10 AM   #526
fluid is offline fluid  Australia
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I have tried to take some better photos of the finished speakers in room.

I am very happy with how they look and are pretty much what I envisioned except I think that I underestimated the height in my mind!

Not the best pictures in the world but hopefully you get the idea. Big black rectangles are not that easy to photograph inside

I am going to be away for the next few weeks so in room measuring and listening won't be happening until I get back.

Full Range TC9 Line Array CNC Cabinet-p1000772-jpg

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Old 30th May 2017, 08:16 AM   #527
samuelj is offline samuelj  United States
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Hello Fluid,

Going away for a few weeks without leaving behind a listening impression of those 'big black rectangles'?!

Very nice build. Guessing these speakers would pull the 'disappearing act' to a spectacular feat as often attributed to such arrays and considering your matt black stealth finish, only feet are showing!

Hope its not too early to ask, are you planning on a sub or a super-tweeter?
And, what amplifier are you using, an UcD? Sorry, I missed that in the long thread.
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Old 30th May 2017, 08:23 AM   #528
gkh is offline gkh  Austria
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Wow, they really look great!
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Old 30th May 2017, 09:05 AM   #529
bushmeister is offline bushmeister
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They look really professional fluid. Very clean. Can't wait to hear what you think about the sound of the line array!
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Old 30th May 2017, 09:40 AM   #530
wesayso is offline wesayso  Netherlands
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Typical... first you leave us waiting for months, dragging along the build while talking about everything except the arrays...

When they are finally finished, you skip town without telling us how you like em!

(just kidding, they do look beautiful! )
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