QSC K Series distortion?

J

joegold

Fractal Fanatic
I hesitate to post this because most of you will think I'm crazy.

In a nutshell...
I'm hearing some ugly-sounding lower midrange breakup when I play certain harmonically complex chords with a dark clean tone through the QSC K-Series powered speakers.

I've tried this (see below) through my K10 and a K12 and KW12 at a local music store and all 3 QSC products exhibited the same behaviour.
I also tried it through a JBL PRX12 and a Yamaha DSR115 both of which did not have the same problem and were clean as a whistle.

Do this to hear what I'm hearing:
Use the neck pickup on your guitar. Humbuckers will work best but it also happens with Strat single coil pickups.
Turn your guitar's tone pot down to around 2.5 and its vol pot up full.
Plug into the Axe (front Input jack with I/O set correctly) and hit the Bypass button, so the only processing going on in the Axe is the DA/AD converters.
Adjust the Axe's input knob appropriately for that guitar.
Plug one of the Axe's Outputs into a K10, K12 or any other K series (non-sub) speaker.

Play the following chord voicing with a loud attack (finger-style is fine) and a short staccato duration.
X 12 13 11 X 13
Bottom to top, that's A Eb Gb F.

Now gradually increase the Input level pot on the QSC and the Output level pot on the Axe.
After you reach a loud-ish, but not-too-loud, level you should be able to hear the breakup I'm talking about.

It sounds to me like the LF driver is breaking up.
It could be due to the driver designs in the K Series.
It could also be due to some sort of IM distorion that the K Series' DSP algorithms don't handle properly because it happens mostly on harmonically complex chords and is less evident with simple chords like major and minor triads.
It's also much less apparent, if at all, when using a brighter guitar tone.

Am I nuts?
Does this same thing happen when you do it?

I'd chalk it up to me having a faulty unit if it wasn't for the fact that those other K-Series boxes had the same problem and the JBL and Yamaha boxes did not.

I'm noticing this at home just practising jazz tunes at medium volumes, and since I'm mostly a jazz player it will make the K10 (or any other K-Series speaker) a non-viable FRFR speaker for me - which is a drag because otherwise I really like it.

[I gleefully await all the flame posts that will tell me not to use a dark jazz tone... lol]
 
I don't have Scott's K10 any longer, so I can't test this. I do have a suggestion, however. You may be clipping the input of the K10. Set your levels to just initiate the distortion. Next reduce the Axe-Fx output level and increase the K10 input level just enough to compensate. Does the distortion decrease or disappear?

Edit: Nothing in the register you're playing in - A220 and up - can possibly overextend a 10" woofer. The cause of the distortion must lie elsewhere.
 
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joegold said:
...and hit the Bypass button, so the only processing going on in the Axe is the DA/AD converters.
Click to expand...
Why test this way. We don't play this way. Play through a patch you like and see if the "issue" is still present. It's almost as if your test is designed to create a problem that under performance conditions wouldn't ever exist.

joegold said:
Am I nuts?
Click to expand...
Yes. But what does that have to do with it.

joegold said:
Does this same thing happen when you do it?
Click to expand...
I have used a single K10 as complete room coverage on several loud gigs and it has behaved very well. I play the K10 at un-mic'd trio volume in a large area most every night of the week and it does just fine for what it is.
 
If anyone is going to get breakup with their K series speaker, it is me. I play ultra high-gain extreme metal through mine. And I haven't noticed this.

Nevertheless, I will try your test on Sunday when I'm at rehearsal and let you know what I find.
 
If I do that (i.e. lower the Axe's output until it cleans up), I can get the distortion to lessen - until I compensate for the level loss by turning the K10's level up.
And if I have to turn down that low to get a clean sound, then this speaker is no good to me.
I.e. With the K10 cranked and the Axe's Output at a level that doesn't cause the K10 to crap out, it's not loud enough for the types of gigs I'll be using the K10 for.

At a rating of 1000 watts, I'm very surprised that I can't get this system much louder with a dark clean jazz tone. Even with the breakup, it's not that loud. My 60 watt Pearce G2r gets louder than this w/o breaking up.
With a bright clean pop tone I can get it pretty loud without it breaking up (at the Axe or at the K10), but it still doesn't sound like 1000 watts of loud to me.
Of course, with a rock sound it can get ear splitting loud.
 
scotts

It's worse with a real preset.

EDIT: I only suggested using the Axe's bypass function to test this because it makes it easy for others here to reproduce the problem and because it takes any programming oddities within the Axe's effects blocks out of the equation.

Admittedly, I play with a very dark tone when I'm playing straight ahead jazz.
But my tone control on the guitar never goes below 2.5.
If I can't get more clean headroom from the K10, when using a tone like that, then it's all but useless to me.

I can't speak to your experiences or the way you like to play, only to mine and the way I play.
And when I'm just practising at home at very reasonable volumes, it breaks up.

Again...
The same problem happens with several K-Series speaker I've tried which includes another K10, a K12 and a KW12.
And it *doesn't happen* with a JBL PRX12 or a Yamaha DSR115.
 
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joegold said:
At a rating of 1000 watts, I'm very surprised that I can't get this system much louder with a dark clean jazz tone.
Click to expand...
Me, too. I didn't try Scott's with that kind of sound, so I can't say whether or not it does the same thing. It's definitely not about pushing the woofer too hard, however. It's the result of something in the electronics being driven into clip.
 
Well it's probably what you suggested is happening in that the K-Series inputs are being clipped.
The fact that it only happens on harmonically complex chords played with a dark tone is what lead me to muse (ignorantly) earlier that it might have something to do with the way their circuits and DSP are designed to handle inter-modulation distortion.
But I don't know what the hell I'm talking about. lol
I just wish it wasn't happening.
The K10, with your corrective EQ, sounds real good to me otherwise.

I might be making a mountain out of a mole-hill.
It may be that when I take it out to a gig that it will have have clean headroom to spare.
I'm not used to playing FRFR. It may actually be louder than I think it is and it may feel totally different when playing in a band.
But based on what I'm hearing at home, with the thing virtually right in my face, at practise levels (loud practise levels mind you... but not real loud), compared to my regular jazz amp (a Pearce G2r), it doesn't sound like it's going to cut it on a gig.

It'd be great if I was doing something wrong that I could fix.
But I don't think that's what's happening.

Has anybody else out there tried my little experiment yet and gotten the same or different results?
 
(joegold)...because it happens mostly on harmonically complex chords...
Click to expand...
At my gig tonight I pushed the volume a bit more than usual, used my cleanest patch and darkened up my tone way more than I usually do (and I get into dark jazz tones as well). I played a couple of solo guitar pieces and intentionally focused on modern cluster harmonies with lots of dissonance and very dense four and five note voicings. I didn't hear anything resembling what you describe.

I have used this speaker on a couple of seriously loud gigs and I didn't even begin to push its capabilities. It has tons of clean headroom.

(joegold)...compared to my regular jazz amp (a Pearce G2r), it doesn't sound like it's going to cut it on a gig.
Click to expand...
You are having way too much trouble with this. Something ain't right. Whatever that something is maybe you should let the FRFR thing go for a while and just enjoy your playing through the gear that you are comfortable with. Too much of the sort of interaction you are experiencing can seriously screw up your head.
 
This may sound very strange, but have you tried more than one guitar? I know that all logic points away from the guitar possibly being the cause but I do have a strange theory after a similar experience. Also post a clip if you can manage to mic it.
 
I can't seem to get mine to break up like that.
I have also played 2 bigband gigs with it where my tone is pretty dark without problems it seems to be loud enough for that
and a gig with a pretty loud (jazz, but still :) ) drummer.

Jens
 
It happens with a Strat (w/Suhr V60LP pups) and an ES-175 (w/Gibson 57 Classics). I haven't tried it with other guitars yet.
It happens when I use the Axe's 1/4" outs (Out1 or Out 2) or the XLR Out 1 jacks.

Has anybody out there actually tried *exactly* what I described in my original post yet with different results than mine?
 
Jens said:
Yes
Click to expand...

You used the exact same chord voicing, with short hard attacks, with your neck pickup on full, your vol pot cranked, your tone pot around 2.5, with your Axe in Bypass mode .... and you heard no breakup at all as you turned the volumes up on the K and the on the Axe?

Really?
 
Yes, I did not play really loud but. Band rehearsal loud for sure.

I did not play only that voicing though.

I just tried again. It does not break up. I mostly play with the tone around 3 anyway.

Jens
 
Hmmm.

Just so y'all don't think it's just me and that I'm crazy....
When I did this at the music store last Monday (comparing the two K10s , a K12, a KW12, the JBL and the Yamaha), the 2 product specialists/sales guys in the store heard it too.
Only in the Ks.
 
For clarity...
We're talking loud, staccato, dense, block chords (all notes/strings stuck at the same time) here.
 
"For clarity"? I thought you wanted it to break up ;)

I did what you wrote and it did not start to break up, You might better get something else than the QSC's or this will drive you nuts ?

Jens
 
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