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Author Topic: Does this trace tell you anything?  (Read 1781 times)

Riley Casey

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Re: Does this trace tell you anything?
« Reply #10 on: January 15, 2020, 11:28:46 am »

I wasn't aware that Radian ever made an active version of the MicroWedge. Are these stock units or some sort of add on power amp?  If these are something with purpose tuned DSP they could probably use another pass at the tuning. Thats the kind of response I'd expect from a passive crossover even on the good traces..



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.

Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #11 on: January 16, 2020, 04:51:50 pm »

I wasn't aware that Radian ever made an active version of the MicroWedge. Are these stock units or some sort of add on power amp?  If these are something with purpose tuned DSP they could probably use another pass at the tuning. Thats the kind of response I'd expect from a passive crossover even on the good traces..

I was unclear. They are being driven active, like using external amps :)

 I believe it was two summers ago when I tuned them, the traces looked pretty much the same then as now.
« Last Edit: January 16, 2020, 04:56:06 pm by Miguel Dahl »
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Matthew Knischewsky

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Re: Does this trace tell you anything?
« Reply #12 on: January 20, 2020, 11:52:30 am »

I was unclear. They are being driven active, like using external amps :)

 I believe it was two summers ago when I tuned them, the traces looked pretty much the same then as now.

Looking at the phase trace can also be helpful when trying when troubleshooting and give some clues as to what's going on. A sine wave sweep can also be revealing for distortion in ways that pink noise or music will not. Looking at the traces is interesting but won't tell you the whole story, they're telling you that further investigation is required. I've seen all kinds of HF driver problems that are sometimes easily resolved but you never really know until things are taken apart and inspected.

Just off the top of my head here's some possible sources of the roll off shown in the trace:
-dirt/debris blocking phase plug and/or voice coil gap
-liquid spill with residue in phase plug and/or voice coil gap
-Shattered diaphragm
-Shifted pole piece
-cracked magnet
-missing/damaged/broken passive X-over network (I don't recall if these Radians had the switchable passive network and if they did, do the passive components remain in the circuit when switched to active)
-Wrong impedance diaphragm installed.

It can be a bit of a detective story to get to the bottom of some of the more challenging issues especially if someone has monkeyed with things when they really shouldn't. One tip if you're trying to compare traces it's really important to not change the testing drive level when making critical comparisons to known good units.

(I'm not one to brag but I did once earn myself the nickname "Diaphragm Hunter" in a dogged pursuit to ensure that even the most well used loudspeakers played well with each other)



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Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #13 on: January 20, 2020, 12:17:00 pm »

Aight.

Just to follow up. Our shop is pretty small. I know I can't do very precise measurments in there, it's hard surfaces and stuff everywhere. And I don't want to take it outside because 1) our shop is in the middle of a residential area 2) It's cold up here.

I have a feeling that I should build some sort of box or something which blocks out at least some mid/HF reflections. How would you guys deal with this?

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Matthew Knischewsky

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Re: Does this trace tell you anything?
« Reply #14 on: January 20, 2020, 12:39:12 pm »

Aight.

Just to follow up. Our shop is pretty small. I know I can't do very precise measurments in there, it's hard surfaces and stuff everywhere. And I don't want to take it outside because 1) our shop is in the middle of a residential area 2) It's cold up here.

I have a feeling that I should build some sort of box or something which blocks out at least some mid/HF reflections. How would you guys deal with this?

To find out whats causing the differences between loudspeakers it's not absolutely critical to measure in a perfect environment. It's much more important to make the same measurement of each loudspeaker each time in order to compare the defective units to the ones that you think are good. The position of the loudspeaker in the room, the position of the microphone relative to the speaker, the drive level, the mic preamp settings. If you have any pipe and drape or a backdrop you could put up can help with the MF/HF reflections. Any box you could build would only create other problems with the measurement.

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Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #15 on: January 20, 2020, 12:46:22 pm »

To find out whats causing the differences between loudspeakers it's not absolutely critical to measure in a perfect environment. It's much more important to make the same measurement of each loudspeaker each time in order to compare the defective units to the ones that you think are good. The position of the loudspeaker in the room, the position of the microphone relative to the speaker, the drive level, the mic preamp settings. If you have any pipe and drape or a backdrop you could put up can help with the MF/HF reflections. Any box you could build would only create other problems with the measurement.

Right. I guess I'll start by checking the speakers for something physical which looks odd. Then I'll swap drivers and cabs to see if a "poor" driver performs better in a "good" drivers cab.
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Brian Jojade

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Re: Does this trace tell you anything?
« Reply #16 on: January 20, 2020, 01:04:03 pm »

+1 to what Matthew said.  You're not really looking for an accurate measurement of the speaker.  You're looking to see what is causing that one to behave differently than the rest.  Keeping your setup identical, and then simply swapping speakers out should give you the accuracy you desire.  Realize though, that in a small room with reflections, even very subtle changes could make a difference in the result. 

As an experiment, start with one speaker, and shift the position a couple degrees each way and re-test to see how much of a difference you see in your lines.  Sometimes things in the room can offer weird, very specific reflections that will change the results dramatically.  Even where you stand in the room can make a difference!
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Brian Jojade

Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #17 on: January 20, 2020, 01:13:05 pm »

This came out a bit wrong from my part. I know I don't need perfect measurments to try to solve this particular issue. It was more "overall". For general tuning. We are already off "stock-setup" for the MW's so tuning needs to be done by ear and what I can see from frequency and phase response traces. It's also to have an environment which is adequate enough for looking through the scope for the rest of the speakers we have. This is probably Off Topic though.

But I'll start with what I wrote in my previous post. Looking for stuff, then swap drivers around.
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Riley Casey

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Re: Does this trace tell you anything?
« Reply #18 on: January 20, 2020, 05:02:40 pm »

For this kind of testing you can measure a meter from the front of the cabinet and learn all you need to know to move forward. The first step really should be removing the diaphgrams and cleaning out the drivers. After that you have some thing to measure, without that you have too many unknown variables. Any speaker that faces up toward the band should be assumed to be compromised so some degree after a couple dozen shows. After a couple years it should be assumed to be beyond usability without service.

Miguel Dahl

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Re: Does this trace tell you anything?
« Reply #19 on: January 23, 2020, 11:30:30 am »

Found this in one of the really bad ones:


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ProSoundWeb Community

Re: Does this trace tell you anything?
« Reply #19 on: January 23, 2020, 11:30:30 am »


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