-10 dBv or +4 dBu ???

Guilty Party

Guilty Party

Member
Hi.

Asking for opinions on what people are setting this pad at and why. It would also be interesting to know what you are running your signal into and if you have found any problems or reasons to to go one way or the other. This is a sound reinforcement question, not involving the computer at all.

I am troubleshooting an FRFR speaker that goes into a muted protection mode, seemingly the speaker is seeing some kind of signal it doesn't like from the FM9 and enters the protection state. I have looked through the manual for the speaker to see whether it will happily accept the higher nominal input but cannot seem to find that info. I have looked at other speaker specs as well and don't see this spec listed there either. Can anyone enlighten me with what the verbage on this spec might look like? The FM9 manual says +4 dBu is for "professional" equipment. What constitutes that if you cannot find the spec on it?

Along the same lines, do we think the input trim on the FM9 could play into the signal being too hot for the speaker to handle? I have it dialed back to like 15% and I am still tickling red a bit. My presets were dialed in a bit hot but I have fixed that and am still having a reliability issue. Trying to get to the bottom of it to see if it is operator error. In other words, do I have something set wrong.

Or is it possible the speaker is overheating?

Curious to hear some replies on this
 
If the speaker in question is a QSC Kxx.2, I think this is a known issue with the speaker system itself. I’m sure others will chime in with details. While a powered speaker might distort if given too much input signal, it shouldn’t be overheating to the point of protection muting it.
 
Yes, it's a known issue. But there are plenty of people who use them without issue. For a reason, they sound great. My question is pretty specific, what are users setting the pad at and, from experiences, does it make a difference or cause a problem. You're thinking is that the speaker is overheating or are those just my words from OP?

I just wanna try and make sure that I am not missing a setting that could be causing this. I have tried both settings on the pad. It blew at +4 after 15 minutes of use, changed to -10 for 30 min and it was fine but quiet, changed back to +4 for 30 min and it was fine. So, inconclusive. And unpredictable. Unreliable? As I mentioned, I also dialed Input trim way back to 15%, could this be the ticket? Unfortunately my testing was flawed as I cannot recall at what point I dialed back Input trim. aargh...

As part of my open case, I am asking QSC whether or not the speaker should be fine at +4 dBu. Just thought I would nose around here a bit for opinions
 
I have all three modelers set for +4 dB, and have used them with RED SOUND’s ELIS.8 and Electro Voice PXM-12MP without problems at stage volume.

Input trim varies depending upon the guitar, but if your modeler is set to occasionally flicker the red when you hit the guitar hard then it’s set correctly for that guitar. Level the scenes and presets so they are around 0 dB and then it’s just a matter of where OUT 1 is set. With a single EV with its output at 50%, the modeler’s OUT 1 will be about 1:00 and the EV will be loud, probably 100 dB-ish, and will run that way for hours without problems.

The connection is always on OUT 1 using XLR.
 
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Since it's going into the Muted Protection mode, it sounds like your speaker might be expecting -10 dBV. There are differences in voltage between the two settings and some gear sees the +4 dBu signal as an overload regardless of that actual volume from the FM9. Your speaker is likely muting to prevent any speaker or other component damage due to excessive volume that can occur with the +4 dBu.
 
Guilty Party said:
I have looked through the manual for the speaker to see whether it will happily accept the higher nominal input but cannot seem to find that info. I have looked at other speaker specs as well and don't see this spec listed there either. Can anyone enlighten me with what the verbage on this spec might look like? The FM9 manual says +4 dBu is for "professional" equipment. What constitutes that if you cannot find the spec on it?
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The spec you’re looking for is Input Sensitivity. Any professional gear manufacturer should make that information available.


Guilty Party said:
Along the same lines, do we think the input trim on the FM9 could play into the signal being too hot for the speaker to handle?
Click to expand...
No.


Powered speakers go into protected mode when they’re trying to produce too much output. Currently, some versions of some powered speakers are known to go into protected mode when they have no reason to.
 
Thanks guys. My gain staging seems to be in order. Nothing is above 0 dB. When I first started having this problem I had my Amp Level too hot (0 dB) but I have that under wraps and dialed back to the defaults typically encountered with any Amp type. I'm using the JVM OD1 Green for the most part and it's level is set a -12 dB. Levels on ALL other blocks are set to defaults (0 dB). Including Out Block. So the only variable I see is the pad and the Input Sensitivity. The speaker, then, MUST be looking for -10 dBv. Which sucks as the out put volume is reduced quite a lot. I would hope that QSC gets back to me about the signal level the speaker is expecting.

don't see anyone posting here that is set to -10 because their speakers are looking for the lighter load...
 
Ok, I just found something that might make a difference...

The K 10.2 has 3 inputs, the 3rd being for a media player so that is not in play at this point.

Input 1 is switchable between MIC/ LINE. I have it set to LINE and have been running from the FM9 into it with an XLR. And having these PM4 issues.

Looking at the QSC docs this morning and I notice that Input 2 is different. It is switchable between HI Z/ LINE. The connectivity diagram illustrates using a TS cable to plug a guitar in to this input and set it to HI Z.

Or are they different? Both MIC (1) and HI Z (2) would be looking for low output sources, ie microphone or passive guitar pickups. MIC setting would engage a Mic preamp, would HI Z do the same? LINE inputs are looking for high output sources (mixers, etc and assumedly modellers?)

I am not running a guitar DIRECTLY into the speaker, so I am not convinced that my signal is HI Z. The FM9 is pretty much a preamp, yes? So signal should require no conversion. Or maybe I am wrong.

If I was guessing, which I am at this point, I think the output signal would be louder if input is set to MIC or HI Z as a preamp would be engaged.

I'm likely barking up the wrong tree, but it is something I had not previously noticed.
 
Guilty Party said:
Thanks guys. My gain staging seems to be in order. Nothing is above 0 dB. When I first started having this problem I had my Amp Level too hot (0 dB) but I have that under wraps and dialed back to the defaults typically encountered with any Amp type. I'm using the JVM OD1 Green for the most part and it's level is set a -12 dB. Levels on ALL other blocks are set to defaults (0 dB). Including Out Block.
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I didn't mean inside the Axe-Fx, but overall in your system. How you are gaing staging between the FM9 and the QSC? How did you set that up?

Guilty Party said:
So the only variable I see is the pad and the Input Sensitivity. The speaker, then, MUST be looking for -10 dBv. Which sucks as the out put volume is reduced quite a lot. I would hope that QSC gets back to me about the signal level the speaker is expecting.
Click to expand...
The only variable for your QSC shutting down? I mean that sounds more like its defective or you are just running the QSC way too loud.
 
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Guilty Party said:
Ok, I just found something that might make a difference...

The K 10.2 has 3 inputs, the 3rd being for a media player so that is not in play at this point.

Input 1 is switchable between MIC/ LINE. I have it set to LINE and have been running from the FM9 into it with an XLR. And having these PM4 issues.
Click to expand...

Yeah Line setting is correct.

Guilty Party said:
Looking at the QSC docs this morning and I notice that Input 2 is different. It is switchable between HI Z/ LINE. The connectivity diagram illustrates using a TS cable to plug a guitar in to this input and set it to HI Z.
Click to expand...
Yeah a device like the FM9 or Axe-FX is not a Hi-Z source, you would set it to the "Line" setting.

Guilty Party said:
Or are they different? Both MIC (1) and HI Z (2) would be looking for low output sources, ie microphone or passive guitar pickups. MIC setting would engage a Mic preamp, would HI Z do the same? LINE inputs are looking for high output sources (mixers, etc and assumedly modellers?)
Click to expand...
Don't know what the QSC does, but yeah you want the Line setting here.

Guilty Party said:
I am not running a guitar DIRECTLY into the speaker, so I am not convinced that my signal is HI Z. The FM9 is pretty much a preamp, yes? So signal should require no conversion. Or maybe I am wrong.
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That's right.

Guilty Party said:
If I was guessing, which I am at this point, I think the output signal would be louder if input is set to MIC or HI Z as a preamp would be engaged.
Click to expand...
What output signal?
 
Guilty Party said:
Ok, I just found something that might make a difference...

The K 10.2 has 3 inputs, the 3rd being for a media player so that is not in play at this point.

Input 1 is switchable between MIC/ LINE. I have it set to LINE and have been running from the FM9 into it with an XLR. And having these PM4 issues.

Looking at the QSC docs this morning and I notice that Input 2 is different. It is switchable between HI Z/ LINE. The connectivity diagram illustrates using a TS cable to plug a guitar in to this input and set it to HI Z.

Or are they different? Both MIC (1) and HI Z (2) would be looking for low output sources, ie microphone or passive guitar pickups. MIC setting would engage a Mic preamp, would HI Z do the same? LINE inputs are looking for high output sources (mixers, etc and assumedly modellers?)

I am not running a guitar DIRECTLY into the speaker, so I am not convinced that my signal is HI Z. The FM9 is pretty much a preamp, yes? So signal should require no conversion. Or maybe I am wrong.

If I was guessing, which I am at this point, I think the output signal would be louder if input is set to MIC or HI Z as a preamp would be engaged.

I'm likely barking up the wrong tree, but it is something I had not previously noticed.
Click to expand...
Your FM9 output signal is not high-Z. It is a low Zout preamp output, as you stated. Guitar is considered high Z at several kohms or more in this context.

Mic level is lowest, followed by -10dBv, then +4dBu.

https://wolfcrow.com/what-is-the-difference-between-line-level-and-mic-level/

Yes all else being equal, much louder using mic or high Z input. Line is least sensitive.

This is curious.. FM9 at +4dBu into line should be ok, perhaps just too hot during spikes for the speaker? I have used my Yamaha DXR10s without such issues. Are there any other speakers you can try for comparison?
 
AlbertA said:
I didn't mean inside the Axe-Fx, but overall in your system. How you are gaing staging between the FM9 and the QSC? How did you set that up?
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Sorry, not really sure what you mean by between FM9 and QSC. Can you explain please
AlbertA said:
The only variable for your QSC shutting down? I mean that sounds more like its defective or you are just running the QSC way too loud.
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I'm leaning towards defective
 
ucnick said:
Your FM9 output signal is not high-Z. It is a low Zout preamp output, as you stated. Guitar is considered high Z at several kohms or more in this context.

Mic level is lowest, followed by -10dBv, then +4dBu.

https://wolfcrow.com/what-is-the-difference-between-line-level-and-mic-level/

Yes all else being equal, much louder using mic or high Z input. Line is least sensitive.

This is curious.. FM9 at +4dBu into line should be ok, perhaps just too hot during spikes for the speaker? I have used my Yamaha DXR10s without such issues. Are there any other speakers you can try for comparison?
Click to expand...
Curious indeed. FM9 at +4 into line would seem typical for any system. I can surely get my hands on other speakers, it's a bit of a process but doable. The retailer is our drummer. I demoed the QSC against the DXR 10. Not for hours, but long enough to settle on the QSC sound. Also demoed against SRM 210 and DHR 12M. The retailer has been made well aware of the issues and I expect to have it solved one way or the other (replacement) as it is a brand new purchase. I have put a lot of time into trying to pin down the issue and testing. Growing weary...
 
So I took a look at the QSC manual.... bummer it doesn't really have an indicator to when you are over-driving the input and looks like there's no separate input gain from output volume. So harder to gain stage that way. Where do you set the gain knob in the QSC?
 
AlbertA said:
So I took a look at the QSC manual.... bummer it doesn't really have an indicator to when you are over-driving the input and looks like there's no separate input gain from output volume. So harder to gain stage that way. Where do you set the gain knob in the QSC?
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Unity, 12 o'clock. FWIW I am using no active DSP on the QSC. No scene, no filters no eq, straight flat
 
Guilty Party said:
Curious indeed. FM9 at +4 into line would seem typical for any system. I can surely get my hands on other speakers, it's a bit of a process but doable. The retailer is our drummer. I demoed the QSC against the DXR 10. Not for hours, but long enough to settle on the QSC sound. Also demoed against SRM 210 and DHR 12M. The retailer has been made well aware of the issues and I expect to have it solved one way or the other (replacement) as it is a brand new purchase. I have put a lot of time into trying to pin down the issue and testing. Growing weary...
Click to expand...
Interesting. I had a few QSC K series and ditched them in favor of the Yamahas. As usual YMMV...
 
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