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Author Topic: Does this trace tell you anything?  (Read 1943 times)

Miguel Dahl

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Does this trace tell you anything?
« on: January 10, 2020, 02:25:38 pm »

Just some quick traces I grabbed on the stage yesterday. There are spikes and dips somewhat due to conditions when I took the measurments. But look at 6k and above.
These are Radian Microwedges 12". Active powered. Oooold. We use an RCF DSP and I just tuned them by ear. But, I know we have "pairs" of even matching speakers. This trace is the with two "ok" ones and two "dull" ones.

Can this indicate a busted or bad "some" component within the speaker?

« Last Edit: January 10, 2020, 02:40:05 pm by Miguel Dahl »
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Keith Broughton

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Re: Does this trace tell you anything?
« Reply #1 on: January 10, 2020, 07:00:49 pm »

Try swapping hi freq drivers to see if anything changes.
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Riley Casey

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Re: Does this trace tell you anything?
« Reply #2 on: January 11, 2020, 07:44:58 am »

How do they sound with sine wave sweeps ?  Stage monitor high frequency drivers ( any driver that faces up at the world ) require routine cleaning. When was the last time you pulled the diaphragms, cleaned out the voice coil gaps and vacuumed out the phase plugs?

Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #3 on: January 11, 2020, 12:32:46 pm »

How do they sound with sine wave sweeps ?  Stage monitor high frequency drivers ( any driver that faces up at the world ) require routine cleaning. When was the last time you pulled the diaphragms, cleaned out the voice coil gaps and vacuumed out the phase plugs?

I have no idea if or when that was last done. I've never done it during my three years there so far. There's some slight distortion-ish on at least one of them.
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Riley Casey

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Re: Does this trace tell you anything?
« Reply #4 on: January 11, 2020, 02:27:42 pm »

Distortion could easily be caused by crud rattling around on the diagram which when facing up acts like a catch basket. Once a year cleaning at a minimum would be my recommendation.  Also switch your analyzer to log display. Much more useful.

Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #5 on: January 11, 2020, 02:40:21 pm »

Distortion could easily be caused by crud rattling around on the diagram which when facing up acts like a catch basket. Once a year cleaning at a minimum would be my recommendation.  Also switch your analyzer to log display. Much more useful.

I'll pop those grilles when they come back from the current job and have a look. Why/how is log more useful?

Reason I started the thread was that my colleague said it "looks" like something fishy with a resistor or something. My thought is that the HF drivers are just past their prime, as the speakers are very old.
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Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #6 on: January 12, 2020, 03:26:59 pm »

If it turns out the HF drivers are shot. Would it be possible to recone everything with new coaxial drivers from RCF? Like this one https://www.bluearan.co.uk/index.php?product=RCF_CX12N351_-_12_inch_450W_8_Ohm&id=RCFCX12N351. We have a good price from our RCF dealer, that why RCF..

Since we already are not on factory DSP tunings, a different driver would just leave the cab itself as "Microwedge". But is this possible? We have been thinking of getting rid of them, bit if one can give them a second life with this, then I guess it's worth keeping them.
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Keith Broughton

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Re: Does this trace tell you anything?
« Reply #7 on: January 13, 2020, 06:51:35 am »

Determine the actual problem first, then look for a solution.
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Art Welter

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Re: Does this trace tell you anything?
« Reply #8 on: January 14, 2020, 03:42:04 pm »

I'll pop those grilles when they come back from the current job and have a look. Why/how is log more useful?

Reason I started the thread was that my colleague said it "looks" like something fishy with a resistor or something. My thought is that the HF drivers are just past their prime, as the speakers are very old.
"Log" gives equal space to each octave, making it easier to see the "big picture".

Assuming the same drive source was used for each, cabinet and mics were in exactly the same place, the deviation between each is within 2 dB to 6kHz. I've seen plenty of brand new drivers that don't match any better.
The high frequency loss above that could easily be caused by "dust bunnies" accumulating in the horn, take a picture when you pop the grilles, my bet is grill foam rot accumulation glued in with some sticky goo in the "dull pair".

Assuming these are active cabinets, there should be no resistors in the cabinets.
If they are using the Radian Microwedge passive crossovers, loss of the HF bypass capacitor could account for the reduced HF output above 6 kHz.
Diaphragm replacements that don't match original specs could also account for the HF differences.



« Last Edit: January 14, 2020, 03:46:48 pm by Art Welter »
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Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #9 on: January 14, 2020, 06:59:22 pm »

"Log" gives equal space to each octave, making it easier to see the "big picture".

Assuming the same drive source was used for each, cabinet and mics were in exactly the same place, the deviation between each is within 2 dB to 6kHz. I've seen plenty of brand new drivers that don't match any better.
The high frequency loss above that could easily be caused by "dust bunnies" accumulating in the horn, take a picture when you pop the grilles, my bet is grill foam rot accumulation glued in with some sticky goo in the "dull pair".

Assuming these are active cabinets, there should be no resistors in the cabinets.
If they are using the Radian Microwedge passive crossovers, loss of the HF bypass capacitor could account for the reduced HF output above 6 kHz.
Diaphragm replacements that don't match original specs could also account for the HF differences.

Ah, yes the big picture. Indeed.

There are active cabs.

Here's all of them. I guess that the one blue guy in there was fed a higher level. "pairs". But i'll pop the hood and take a look at how it looks under the grille.



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ProSoundWeb Community

Re: Does this trace tell you anything?
« Reply #9 on: January 14, 2020, 06:59:22 pm »


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