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Multi-Way Conventional loudspeakers with crossovers

rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
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Old 28th April 2020, 01:08 AM   #3001
emailtim is offline emailtim  United States
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Quote:
Originally Posted by fluid View Post
...

Your high frequency driver exhibits a similar response to an array in that it has sharp peak followed by unsettled response as the different parts of the sound combine at the microphone from different positions.

...
FWIW, the high frequency driver is a vertical 5 foot ribbon tweeter.
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Old 28th April 2020, 01:16 AM   #3002
fluid is offline fluid  Australia
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I got that from your description which is why I said the response was similar to an array. Compare your long ribbon impulse to my 25 driver impulse from a few pages back similar behaviour. Look at the first millisecond. There will be a path length difference from the ends of the ribbon Vs centre to the mic just like there are in an array. And when you look you have the same unsettled first millisecond.
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Old 28th April 2020, 03:18 AM   #3003
emailtim is offline emailtim  United States
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Thanks Fluid. Here is the ribbon tweeter zoomed in.

I calculated the +/- 2.5 foot distance from the mic tangent which comes to @ +/- 4" or 1/3rd of a foot (first circle) which is shorter than the 8/10ths of a ms ripple.

I assume the additional ripples (second circle) must be the floor ceiling line source reflections ???

Thanks for the info. I see some of transferred onto the tweeters STEP.

Click the image to open in full size.

Quote:
Originally Posted by fluid View Post
I got that from your description which is why I said the response was similar to an array. Compare your long ribbon impulse to my 25 driver impulse from a few pages back similar behaviour. Look at the first millisecond. There will be a path length difference from the ends of the ribbon Vs centre to the mic just like there are in an array. And when you look you have the same unsettled first millisecond.
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Old 28th April 2020, 09:42 AM   #3004
fluid is offline fluid  Australia
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I would be surprised if anything less than a millisecond was a reflection rather than the speaker, 1ms is a path length difference of about 30cm.

The portion of the impulse in the left circle is quite different to the right which seems a more defined ripple.

You can try a short gate and look at the frequency response, this is dominated by high frequencies anyway.

In your earlier graphs the first reflection looked to be between 3 and 4ms.
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Old 28th April 2020, 05:09 PM   #3005
emailtim is offline emailtim  United States
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I will investigate further.

I also noticed the waveforms of the content of the 2 circles to be different but didn't know what to make of it. I appreciate being able to better interpret the plots.

I use the 1ms~=1ft rule of thumb. 30cm is 11.8 inches.

The 4ms/4ft reflection is most likely the leather couch which I should probably move back (or throw a quilt over) when taking measurements.

Quote:
Originally Posted by fluid View Post
I would be surprised if anything less than a millisecond was a reflection rather than the speaker, 1ms is a path length difference of about 30cm.

The portion of the impulse in the left circle is quite different to the right which seems a more defined ripple.

You can try a short gate and look at the frequency response, this is dominated by high frequencies anyway.

In your earlier graphs the first reflection looked to be between 3 and 4ms.
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Old 28th April 2020, 11:17 PM   #3006
fluid is offline fluid  Australia
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Originally Posted by emailtim View Post
I use the 1ms~=1ft rule of thumb. 30cm is 11.8 inches.
Seems odd to quibble over a slightly inaccurate rule of thumb division.

For us metric users 3ms per metre is the ball park figure. Neither is totally accurate.

I hope you took the intended point that unless you have a reflective surface in that area you are looking at speaker response in the sub 1ms region.
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Old 28th April 2020, 11:51 PM   #3007
wesayso is online now wesayso  Netherlands
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Quote:
Originally Posted by fluid View Post

I hope you took the intended point that unless you have a reflective surface in that area you are looking at speaker response in the sub 1ms region.
On either side... so it can also be a reflective surface near the microphone.

Did we see a picture of the baffle?
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Old 29th April 2020, 12:36 AM   #3008
fluid is offline fluid  Australia
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Originally Posted by wesayso View Post
On either side... so it can also be a reflective surface near the microphone.

Did we see a picture of the baffle?
I said path length before but not directly in the part quoted. But with a bad mic setup it could easily cause ripples or small reflections.

No picture but that was a 5ft ribbon from description.
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Old 29th April 2020, 12:53 AM   #3009
emailtim is offline emailtim  United States
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Quote:
Originally Posted by fluid View Post
Seems odd to quibble over a slightly inaccurate rule of thumb division.

For us metric users 3ms per metre is the ball park figure. Neither is totally accurate.

I hope you took the intended point that unless you have a reflective surface in that area you are looking at speaker response in the sub 1ms region.
Sorry Fluid, I was not quibbling or disagreeing at all. Just stating I don't normally think/dream/work in the metric system and none of my tapes are metric but do have a metric machinist ruler, feeler gauges, wrenches and sockets, none of which would work for measuring the 2-channel room distances.

1) I confirmed the 4ms ripple was a leather couch reflection.
2) I confirmed the 8ms ripple was a reflection off the back wall.
3) I tried covering the top and the bottom of the front of the ribbon to make it a quasi-point-source. It made some minor magnitude changes to the 1st ms of the plot confirming your assertions.
4) I tried padding the floor in front of the ribbon and it made no difference confirming it wasn't the floor's line source extension. I didn't test the flat ceiling reflection.

The Ribbon Tweeter is a standard Magnepan Ribbon.

Click the image to open in full size.

As for the mic, it is on a standard mic stand, pointing straight at the speaker with a 0 degree correction file. No special shock absorbed mount, just a pressure fit clamp.

Last edited by emailtim; 29th April 2020 at 12:58 AM.
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Old 29th April 2020, 01:06 AM   #3010
fluid is offline fluid  Australia
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Quote:
Originally Posted by emailtim View Post
Sorry Fluid, I was not quibbling or disagreeing at all. Just stating I don't normally think/dream/work in the metric system and none of my tapes are metric but do have a metric machinist ruler, feeler gauges, wrenches and sockets, none of which would work for measuring the 2-channel room distances.


As for the mic, it is on a standard mic stand, pointing straight at the speaker with a 0 degree correction file. No special shock absorbed mount, just a pressure fit clamp.
No problem seems I misunderstood your intention. I did wonder which tape measure you had to mark out 11.8 inches

Troels graveson has a good document showing mic ripple putting a tube over the back can make quite a difference.
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