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Impulse Response - Phase Issues?

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Hello All!

Despite being a guy who has used Line 6 gear, as well as other modeling software/hardware for about 15 years, as records FAR more frequently than playing live, I'm fairly new to using impulse responses.  This afternoon I decided, after a year and a half of owning my Helix, to download some freebies from Ownhammer, as well as some other supposed hi-quality freebies.  First off...WOW, talk about bringing the guitar sound 'to life'!  I use Helix the most these days, but before that (and after the Pod Live and HD500), I was a big BIAS fan.  Using an IR gives the Helix that same feel that the stock cabs don't seem to quite capture.  The issue that I've experienced with all of the IRs, however, is that there seem to be some type of phasing issue.  This isn't noticeable at all when playing rhythms or playing single notes low on the neck, but becomes very noticeable when playing single note lines higher on the fretboard.  It is as if a few seconds after hitting a sustained note,the high end cuts off as if there were a phaser on.  At first I thought this was just maybe due to a poor quality impulse response, but given that I've tried a variety if responses, some from high quality manufacturers, the issue persists with all impulses, and isn't as prominent when playing multiple notes or doing double-stops, but is definitely there when using single-string notes.  I'm also using the 2048 option for length of IRs.  I'm wondering if there is something I have wrong for settings, whether it's something inherent in using IRs, or whether I'm doing something wrong.  Any advice, insight, or help would be appreciated!

-Joe

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That is really weird. IR won't have an effect on your sound like you mention. Perhaps something else in your signal chain is creating this. What else do you have going on in your preset and how are you monitoring your sound?

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Hi Joe - I bought and use RedWirez, OwnHammer and 3 Sigma IRs after trying the freebies and have never experienced what you described. Others will weigh in with more technical details, but I've read about IRs issues, including cutting off, when you don't use the right "length." For Helix, 48k Hz and 200 ms IRs are recommended (maybe required - I forget). There is one phase issue I've read about if you combine IRs from different creators, but I regularly combine RedWirez, which are a little thinner sounding to enhance the highs, with OwnHammer, which are deeper. I've never heard the phase issue other refer to.

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Thank you both for taking the time to respond.  I decided to spend my lunch break trying a few different things and I think I have found the issue.  Almost all my patches that I've created have dual amps for my distorted sound, and it seems that this phase issue is present but very slight with the stock cabs.  Replacing the stock cabs with an IR seems to be bringing the issue more to the forefront (using an Angl Meteor and Brit 2204).  Creating a new patch with just one amp does not produce the same phase issues.  Is this anything either of you have experienced and do you have any potential things I should try?

Thanks again for your help!

-Joe

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Thank you both for taking the time to respond.  I decided to spend my lunch break trying a few different things and I think I have found the issue.  Almost all my patches that I've created have dual amps for my distorted sound, and it seems that this phase issue is present but very slight with the stock cabs.  Replacing the stock cabs with an IR seems to be bringing the issue more to the forefront (using an Angl Meteor and Brit 2204).  Creating a new patch with just one amp does not produce the same phase issues.  Is this anything either of you have experienced and do you have any potential things I should try?

Thanks again for your help!

-Joe

I don't have any presets that I use two amps simultaneously. I'll have to give it a try to see if I can duplicate. Can you post a screen shot of your preset so we can see the signal flow?

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Absolutely, man. It's based off one of the presets called "Almost not Fair", but it's been changed a heck of a lot.  I've attached the screenshot (it's hard to see the actual text, but it shows the order), and if you'll forgive my playing I've also uploaded a very short mp3 so you can hear the phasing issue as well, but you'll have to paste it into your browser.  (clyp.it/qcq4jsax)

printscreen.pdf

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I notice your output is set to digital. What are you playing through with your output signal?

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I am using spdif out into a presonus firestudio, which is feeding my monitors.

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It seems to me that if you have 2 signals in parallel - for example, a stereo signal path - and somehow only applied the IR to one of them, then a phasing effect becomes a possibility. Is that a potential culprit here?

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If you run 2 paths in parallel with 2 different impulse responses, it is possible (actually very likely) that phase does not match at every frequency. At some frequencies you will have opposite phase. Just like real cabs! In general it is a bad idea to mix different cabs with significantly different frequency responses unless you are using a crossover just for this reason. If your 2 IR match really well in the time domain, it means that phasing issues will start at relatively high frequencies as you say.

 

Perhaps changing the level in one of the 2 paths will alleviate the problem (cancellations will not be so deep if you unbalance both paths by just 1 or 2 dB), but it is also possible that the problem moves to a different frequency range.

 

Anyway many people out there (at least a few bassists) swear that mixing cabs with significantly different responses they are getting the best from both, when in reality they get cancellations at some key middle frequencies.

 

Parallel paths dealing with different frequency bands (low end in one, high end in the other) don't have this issue.

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Hello All!

Despite being a guy who has used Line 6 gear, as well as other modeling software/hardware for about 15 years, as records FAR more frequently than playing live, I'm fairly new to using impulse responses.  This afternoon I decided, after a year and a half of owning my Helix, to download some freebies from Ownhammer, as well as some other supposed hi-quality freebies.  First off...WOW, talk about bringing the guitar sound 'to life'!  I use Helix the most these days, but before that (and after the Pod Live and HD500), I was a big BIAS fan.  Using an IR gives the Helix that same feel that the stock cabs don't seem to quite capture.  The issue that I've experienced with all of the IRs, however, is that there seem to be some type of phasing issue.  This isn't noticeable at all when playing rhythms or playing single notes low on the neck, but becomes very noticeable when playing single note lines higher on the fretboard.  It is as if a few seconds after hitting a sustained note,the high end cuts off as if there were a phaser on.  At first I thought this was just maybe due to a poor quality impulse response, but given that I've tried a variety if responses, some from high quality manufacturers, the issue persists with all impulses, and isn't as prominent when playing multiple notes or doing double-stops, but is definitely there when using single-string notes.  I'm also using the 2048 option for length of IRs.  I'm wondering if there is something I have wrong for settings, whether it's something inherent in using IRs, or whether I'm doing something wrong.  Any advice, insight, or help would be appreciated!

-Joe

 

Just thought I'd mention this as I had not seen it brought up yet. The first thing I check when a note is cutting off early is the noise gate setting on the Input block.

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Thank you each for your help! I think ultimately Parapentep70 has nailed the issue. I'm so used to working with virtual amps that I wasn't even thinking in 'real life' response. Pretty much any sim I've used didn't have this issue, but I've also not been using IRs. Two IRs, going with one amp, or using stock impulses on the helix are the solution. Thanks guys!

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As I recollect, Helix is intentionally handling a variety of time based processing to correct for various phasing issues in many of it's stages. I do not know to what extent, if any, this applies to the Line 6 furnished Helix Cabs, their Mic Positions and Early Reflections. I do not recollect where I read this, but I seem to remember seeing this perhaps from Ben Adrian or Eric (Digital Igloo). I have not explored viewing the phasing impact of combining multiple Helix Cabs via a DAW, but it certainly would be easier to do so once Helix Native is released.

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I have massive Phase problems when playing live.  Sometimes the phase isn't evident whilst listening to the patch in stereo, but when the left and right outputs are summed to a mono stage monitor, phase cancellation is a massive problem.  Sometime. I'll get a huge drop in volume due to phase cancellation and I can't hear what I'm playing. A simple phase alignment adjustment in the output block would be a great help.  Also please give us some meters, either on the device or in the editor so we can match volumes between patches.  Cheers.

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