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Impulse Response : 101


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i have never really understood the mic'd cab sims that come with the HD500 or any device that supports this cab sim type stuff come to mention it, i just cant understand or get my head wrapped around how it can work ? because the sound is still coming out of what ever type of speaker/s the user is using and different types of speakers which i thought the coil inside the speaker is to do with the voicing of the speaker or am i totaly wrong .. its quite confusing for me at least and im not really convinced but thats probs due tothe lack of understanding how it works lol

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Impulse Responses are simple wave files created by sampling an impulse of a room or piece of gear.

 

They are fairly easy to make with the right program and there are plenty of free and for sale IRs of all sorts of things.

 

Most common is of room. spaces for reverb but even high end record chains and amps and cabs thus

the popularity to be able to load them in Guitar FX processor.

 

Here is a link to get an understanding of them to make your own or be able to put them to good use.

http://designingsound.org/2012/12/recording-impulse-responses/

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I hope the Helix can load stereo IRs.

That means a L and a R loaded separately.

Then if any number of IRs can be assigned to  a path. ie multiple blocks

things could get interesting.

Stereo IRs for Cab then post an IR for a recording chain into an API or Neve console or one of each L and R.

 

I'd like to know the limits of IR playing in the Helix and the possibilities.

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Limits are 4 IR's per patch and maximum 2048 sample length

 

So 4 miked Cabs - Yes but nothing else; the thing about IRs however is that you can combine them externally so potentially 2 is all you should need even with 8 mike positions spread in a stereo field

 

But 2048 sample length presumably at 96K samples/second gives only 2 hundredths of a second which I am told is good for cabinet sounds and potentially Acoustic Guitar body resonance, but is nothing like long enough for reverbs or other long duration time effects

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The Helex FAQ Thread:

 

 

Can I load third-party or my own custom IRs (Impulse Responses)?

Yes. IRs are loaded into Helix via the Helix Mac/PC software. They will then be available from special IR blocks that can be placed anywhere on your signal paths. Helix can store up to 128 1024 or 2048-point IRs, and a preset can run up to four IRs simultaneously (DSP permitting).

 

Various threads on TGP and other forum about how long a IR is needed to achieve various effects - 2048 is the High Resolution IR size on an AxeFX so there is some talk about it.  I had confirmation when I asked the question that Acoustic Guitar "body" would be possible that would sound good for picked notes, but may not be as good for a strummed guitar - the question was however in the context of using IR as a guitar simulator; that is making a clean electric sound like an acoustic, I suspect that it is plenty to make a piezo pickup sound like a miked acoustic guitar.  

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Limits are 4 IR's per patch and maximum 2048 sample length

 

So 4 miked Cabs - Yes but nothing else; the thing about IRs however is that you can combine them externally so potentially 2 is all you should need even with 8 mike positions spread in a stereo field

 

But 2048 sample length presumably at 96K samples/second gives only 2 hundredths of a second which I am told is good for cabinet sounds and potentially Acoustic Guitar body resonance, but is nothing like long enough for reverbs or other long duration time effects

Good new! I'll keep an eye on the FAQs

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Yes IRs do sound like they act like filters, but unlike eq they have a time dimension and while they are not synthesis (replace the source) they are widely used for simulations - HD Cab and Mic combinations are IRs but with various effects and controls wrapped around them; the guitar simulations in JTV and the Acoustic Body on Stagesource almost certainly include and element of IR in the process.

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If anyone wants to experiment with IR's, while they're waiting for their Helix, they can get the LeCab2 .vst plugin from LePou.  This is a free IR loader that can be launched from within your DAW.  Then dowload some IR's to load into LeCab2.  I'd suggest some of the free cabinet IR's from Catharsis.  Very easy to do this and a lot of fun.

 

LeCab2:

http://lepouplugins.blogspot.com/2010/12/lecab2-vst-for-windows.html

 

Catharsis IR's:

http://metalhomerecording.com/presets/Gear_Review_Catharsis_IRs/Catharsis.zip

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I would add to DarrellM5's post... You can use your HD500 for this if you have one:

 

Set up a patch with a Full Amp and select No Cab. Attach some FRFR monitoring solution to the HD500 or use headphones

 

Connect USB to Computer and set up your DAW (Reaper?) so that Inputs are from HD500 and Outputs are to HD500,

Set USB Hardware monitoring level to 0 (very important this turns off the direct path in the HD500 and routes everything via USB)

On a new track set input to be HD500, add LeCab2 VST and arm so that you can monitor the audio on the track.

Open the LeCab2 VST editor and load 1 or more IR's

 

The audio path should now be: guitar -> HD500 [Amp] -> usb -> DAW [LeCab2] -> HD500 -> FRFR

 

There will be more latency than you are used to, but it is a great way to play with the concept of IRs 

 

Personally I found that if listening over headphones (HD500) you could get an absolute wall of sound by using 5 or 6 different IRs (same Cab different mics and positions), but when sent to my lower quality PA speakers the extra detail didn't come across well enough to justify using it.

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I would add to DarrellM5's post... You can use your HD500 for this if you have one:

 

Set up a patch with a Full Amp and select No Cab. Attach some FRFR monitoring solution to the HD500 or use headphones

 

Connect USB to Computer and set up your DAW (Reaper?) so that Inputs are from HD500 and Outputs are to HD500,

Set USB Hardware monitoring level to 0 (very important this turns off the direct path in the HD500 and routes everything via USB)

On a new track set input to be HD500, add LeCab2 VST and arm so that you can monitor the audio on the track.

Open the LeCab2 VST editor and load 1 or more IR's

 

The audio path should now be: guitar -> HD500 [Amp] -> usb -> DAW [LeCab2] -> HD500 -> FRFR

 

There will be more latency than you are used to, but it is a great way to play with the concept of IRs 

 

Personally I found that if listening over headphones (HD500) you could get an absolute wall of sound by using 5 or 6 different IRs (same Cab different mics and positions), but when sent to my lower quality PA speakers the extra detail didn't come across well enough to justify using it.

 

That's perfect, thanks!! It is making more sense now; gotta give this one a try

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Maybe I can add a simple analogy to help.

 

1. How are IRs created? Let's say you have a device whereby if you put dough in, gingerbread men comes out. So, put a piece of paper in (sine sweep) and get a gingerbread man cutout. Then, find out difference between paper to cutout (transfer fuction). Finally, make a gingerbread man mould to match this difference (IR file).

 

2. How do IRs work? Well, now you have your mould, give it to your kitchen assistant (IR loader). Now, you can give her anything, dough, beef, your cat (amp output), and she'll make gingerbread men shapes with your mould. In other words, she's imparting the same transfer function to all inputs.

 

3. What's the difference between IRs and real cabs? Well, if you give your assistant a 6inch thick slab of dough (hot signal), you'll get a 6inch thick gingerbread man with otherwise the exact same dimensions.

 

If you put that same slab of dough into the device (real cab), you may get a slightly different shaped gingerbread man (speaker saturation, distortion).

 

In other words, real cabs may have different transfer functions depending on input dynamics (e.g. volume). When you capture an IR, it's just one transfer function, which is at the dynamic level of your capture signal.

 

Hope it helps!

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  • 3 weeks later...

The Helex FAQ Thread:

 

 

Various threads on TGP and other forum about how long a IR is needed to achieve various effects - 2048 is the High Resolution IR size on an AxeFX so there is some talk about it.  I had confirmation when I asked the question that Acoustic Guitar "body" would be possible that would sound good for picked notes, but may not be as good for a strummed guitar - the question was however in the context of using IR as a guitar simulator; that is making a clean electric sound like an acoustic, I suspect that it is plenty to make a piezo pickup sound like a miked acoustic guitar.  

 

Axe FX 2 goes up to 8000 samples (170 ms) for UltraRes IRs.

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Axe FX 2 goes up to 8000 samples (170 ms) for UltraRes IRs.

 

At 48KHz sample rate, that's 166.67ms. At the same sample rate and a 2048 sample IR, the Helix would be 42.67ms. Does anyone know what the ones built into Helix are?

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I have seen elsewhere that Helix is 48KHz sample rate, so you are correct Duncan (correction to my earlier guess that it was 96k rate).

 

Axe FX 2 UltraRes IRs are that big - yes, but the much more commonly used Hi Res are 2048 and Standard Res are 1024.  Even the Axe FX 2 is limited in how many Ultra IRs it can process.

 

I think DI said the ones build into Helix are 2K as well, but optimised to be less DPS intensive to run

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  • 8 months later...

Can I ask for some help...?  I have downloaded a whole load of ownhammer IR's - then opened the Helix IR manager (on Mac) - tried to drag across to import - no joy...  The selected wav files look like a track would in iTunes (ie with blue/red itunes symbol underneath) - with the relevant description in text underneath...  Is this the wrong format...?  Help!  Thanks.

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Can I ask for some help...?  I have downloaded a whole load of ownhammer IR's - then opened the Helix IR manager (on Mac) - tried to drag across to import - no joy...  The selected wav files look like a track would in iTunes (ie with blue/red itunes symbol underneath) - with the relevant description in text underneath...  Is this the wrong format...?  Help!  Thanks.

They are probably the wrong format. Does Helix import .wav IR's?

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Page 28 of the Helix manual specifies *.wav format.  iTunes also recognizes *.wav files too as a compatible audio format, which would explain them looking like iTunes tracks.  Maybe there is a bug in the drag/drop functionality.  In the Helix application under the Impulses tab, it looks like you can click Import and browse to the IR *.wav files.

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  • 3 months later...

Helix doesn't come with any IRs.  If you had IRs before the 2.0 update, you must have loaded them.  Use the Editor to reload them, just drag and drop into the slots in the "IMPULSES" tab of the editor, either as a group or one by one.

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Helix doesn't come with any IRs.  If you had IRs before the 2.0 update, you must have loaded them.  Use the Editor to reload them, just drag and drop into the slots in the "IMPULSES" tab of the editor, either as a group or one by one.

Where do you download the editor from? The only thing available is the firmware 2.0...

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Where do you download the editor from? The only thing available is the firmware 2.0...

Go to: http://line6.com/software/index.html

 

You'll see 3 selector drop-downs near the top.  Under Product, select "Helix".  Under Software, select "Helix".  Make sure your OS is selected correctly.  Click "Go".

 

Should look something like this (attached).  That's the "Helix Editor" - v2.00 is listed first, with older versions below it.

post-2278677-0-39922200-1468804070_thumb.png

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Impulse Responses are simple wave files created by sampling an impulse of a room or piece of gear.

 

They are fairly easy to make with the right program and there are plenty of free and for sale IRs of all sorts of things.

 

Most common is of room. spaces for reverb but even high end record chains and amps and cabs thus

the popularity to be able to load them in Guitar FX processor.

 

Here is a link to get an understanding of them to make your own or be able to put them to good use.

http://designingsound.org/2012/12/recording-impulse-responses/

 

Thanks for the link to the Designing Sound article. It was definitely a good read.

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  • 8 months later...

i have never really understood the mic'd cab sims that come with the HD500 or any device that supports this cab sim type stuff come to mention it, i just cant understand or get my head wrapped around how it can work ? because the sound is still coming out of what ever type of speaker/s the user is using and different types of speakers which i thought the coil inside the speaker is to do with the voicing of the speaker or am i totaly wrong .. its quite confusing for me at least and im not really convinced but thats probs due tothe lack of understanding how it works lol

 

Stevev! This was waaaay back, but it might still come in handy that 1) you really need a good DAW, 2) you really need great REFERENCE headphones or speakers, 3) you must understand that while a diamond rests inside a muddy bag, it is still a diamond. This metaphorically means even if you listen to a perfectly recorded piece of music made by the best musicians with the best gear available, your device's speakers will not corrupt the perfection of the music, only its delivery.

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SOMEONE WHO CAN HELP ME TO UNDERSTAND HOW CAN I PLACE IN THE EFFECTS CHAIN THE GOES, WHICH ARE THE MODELS THAT I CAN PLACE? ,WHERE? HOW DID I MODIFY IT? CAN ANYBODY HELP ME. IS NOTABLE THE DIFFERENCE WITHOUT USING THEM ??? THANK YOU. GREETINGS FROM ARGENTINA. PABLO B)

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SI ES EN CASTELLANO MEJOR!!!! YA QUE NO HAY VIDEOS TUTORIALES EN INTERNET, OJALA LOS ALLA Y SI LO ENTIENDO LO HARE YO MISMO! SALUDOS!! 

 

ALGUIEN QUE ME PUEDA AYUDAR A ENTENDER COMO PODER COLOCAR EN LA CADENA DE EFECTOS LOS IR, CUALES SON LOS MODELOS QUE PUEDO COLOCAR? ,EN DONDE? COMO LOS MODIFICO? ALGUIEN PUEDE AYUDARME. ES NOTABLE LA DIFERENCIA SIN USARLOS???  GRACIAS. SALUDOS DESDE ARGENTINA. 

PABLO.- 

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