'Nother IR 'Speriment

Jay Mitchell

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You included all the info that makes a reflection-free IR “sound 3D to our brains,”
Wow. You got one right.

which is a bit like saying a black and white film includes all the information needed for our brain to interpret the color of the scene.
Nope. Capturing a source of sound can (and I assert should) be a separate process from capturing (or simulating) an acoustic environment. FYI, IRs of acoustic environments can only be convolved on one modeler at this time.
 

dk_ace

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2,916
It’s really interesting to me that you posit that the decay slope difference between the left and right is what might be making the difference everyone is reporting. My only slightly educated guess would have been that such a thing would be too subtle to hear or feel. Can’t wait to try this in a week or so when I’m back.

D
 

Jay Mitchell

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5,830
It’s really interesting to me that you posit that the decay slope difference between the left and right is what might be making the difference everyone is reporting.
It's not that you're consciously aware of the fact that your left and right ears are hearing different things. There's also no image shift. There's a small but detectable difference in tonality and transient behavior.

There are ear/brain processes that are not terribly well-understood at this time (although there's ongoing research in the field). For example, your brain doesn't mix signals from your left and right ears. You can play a sound in the left ear and the same sound delayed by, say, a millisecond in the right ear. If you mix the two sounds electrically (or in DSP), you'll get a deep and broad (about an octave) response notch centered at 500Hz that is immediately audible and detrimental. If you instead play a sound in one ear and the delayed version in the other using headphones, you'll still easily hear the region that would be cancelled in an electrical mix. Same thing with inverted polarity: done electrically or in the air, you get a huge drop in volume (complete cancellation in the electrical case) but only an apparent tonal shift with no drop in volume if you apply the sound and its inverted version to each ear exclusively.
 
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Steely Dave

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1,183
It’s already been covered several times in this thread, but for posterity:

  1. Split the stereo IR into its L and R components. Save these as two separate mono IRs.
  2. Use a path split in Helix. At the split point, pan one side fully L and the other side fully R.
  3. At the merge point, again pan the left side fully L and the right side fully R. This is necessary because the IR blocks will collapse the signal that entered them into dual-mono, so to restore the stereo image at the merge, we have to re-pan them.
  4. Lastly, put an IR block on each side of the split path. Use the L mono IR from step 1 on the left-panned side, and vice versa.
Doing the above is equivalent to using a single stereo IR with a stereo IR loader. I shared a preset earlier in this thread for Helix that already has it set up with the IR being discussed in this thread.
Sounds convenient.
 

chrishurley

Silver Supporting Member
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954
I gave it a whirl on the axe3, imported via axe edit (which identified it as having a left and right and I imported both of them. I dropped it on a cab block panned hard left and right and auditioned under headphones. I had another channel on the cab block with just one channel of the pair panned center and one with both centered so I could easily switch.

I enjoyed playing through them but I really had a hard time hearing a difference between the three-I don't think I could identify which was which between the stereo hard pan, summed mono or centered single channel.

Originally, my axe output was set to l+r which was quite apparent when I added a reverb block but I fixed that immediately.

I feel like I'm missing "it" somewhere.
 

Jay Mitchell

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5,830
I enjoyed playing through them but I really had a hard time hearing a difference between the three-I don't think I could identify which was which between the stereo hard pan, summed mono or centered single channel.
Thanks for the feedback. This is why I shared the IR. Do you have a stereo speaker system you can try as well? I've not tried 'phones myself (don't own any), so I have no idea if they make a difference.
 

dlc86

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325
The IR I'm sharing here includes the "frequency + phase information that makes it sound 3D to our brains." All of it.
Does that really contain the correct phase information though? Was the mic pointed straight towards the cab? Cuz from my little experience I know that the angle of the mics contributes significantly in producing the correct phase information for binaural.

For example an ORTF array with its 110° angle and 17cm capsule spacing produces phase and time differences much more similar to those of human ears compared to, let's say, an A/B array with the same spacing where the phase differences are negligible.

But using omnidirectional measurement mics probably poses another problem in that regards
 

Jay Mitchell

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Does that really contain the correct phase information though?
Yes.
Was the mic pointed straight towards the cab?
Yes, although it's an omni test mic, so its aiming is noncritical.
Cuz from my little experience I know that the angle of the mics contributes significantly in producing the correct phase information for binaural.
I've done quite a bit of work with binaural recording and playback systems. This was not such an attempt, nor did I intend to represent it as such. However, it does contain the necessary phase information - which is actually minimal - to localize the speaker to a median-plane position with stereo loudspeakers. There is no attempt to capture elevation cues, which are due to highly individual pinnae responses and therefore not robustly reproducible anyway.

For example an ORTF array with its 110° angle and 17cm capsule spacing produces phase and time differences much more similar to those of human ears compared to, let's say, an A/B array with the same spacing where the phase differences are negligible.
When a source lies in the median plane - as this IR places it - the phase differences are negligible. Additionally, an ORTF array does not reliably capture binaural cues. It's a workable technique to create a sonic image with loudspeakers, but binaural recording requires a dummy head.
 
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Brandon7s

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1,794
Just tried this IR out. It sounds incredibly bright to my ears vs. other IRs, FFRF or otherwise. I kept checking to make sure I had the IR block turned on because the high end is MUCH brighter than I'm used to. I'd be curious to see try a similar IR but with a different cabinet or different speakers.
 

chrishurley

Silver Supporting Member
Messages
954
Just tried this IR out. It sounds incredibly bright to my ears vs. other IRs, FFRF or otherwise. I kept checking to make sure I had the IR block turned on because the high end is MUCH brighter than I'm used to. I'd be curious to see try a similar IR but with a different cabinet or different speakers.
Interesting- I found it quite mellow compared to a lot of IR's
 

mbetter

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802


Helix Ventoux > TH-U Supercabinet (definitely processes the IRs in stereo - also checked with PSP Stereo Analyzer and confirmed that IR was processed in stereo)

Although I hate your IRs to date, it seems you cracked the code for the best sounding IR with this one, Jay.


Ok, this sounds absolutely fantastic.
 

Jay Mitchell

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5,830
In the interest of clarifying matters, I'll add a few observations here.

1. When I acquire IRs, I place the cab on a rotation fixture. I then acquire a collection of IRs, rotating the speaker each time by a small angular increment and leaving the mic in the same position. This process can result in as many as 100 IRs of the same cab. Most of those IRs are for archival purposes, in case I decide after the fact that I'm interested in the cab's out-of-pattern behavior.

2. I always play through a cab first and identify the "sweet spot(s)" in its radiation pattern. I use that information to enable me to focus initially on auditioning IRs in their angular neighborhood.

3. If you think about 1. above, you'll realize that a given IR can represent the arrival at the player's right ear and another one the arrival at the left ear. Although I recognized this quite a few years ago, I don't use a stereo rig, so I never attempted to make use of that recognition.

4. As I pointed out earlier, I've seen attempts to justify the fact that most folks really don't remember - or never knew - what multi-speaker cabs sound like by claiming that each ear hears a different magnitude response - IOW, peaks and notches heard in one ear won't be present in the other - and that therefore the ragged response of, say, a 4x12 is not audibly evident. Subjectively, I knew this to be mistaken - I've heard the ragged response and the dramatic differences from one spot to another that a 4x12 creates - but, prior to this, I had not examined actual representative response data. Now I have. The response change from ear to ear is not enough to "smooth out" the ragged details.

One item I always find interesting when I share IRs is that some folks will say an IR is too "dark" or "muffled," while others will assert that the same IR is too "bright," "harsh," "mid-forward," etc. There are obviously huge variations in subjective taste and/or tone-dialing choices.

If you downloaded the IR, you have four use options: 1) Stereo as provided, 2) Left channel panned center, 3) Right channel panned center, and 4) Both channels mixed to mono. If you like the IR but don't hear a significant difference among those choices, then it won't matter which one you choose (and you won't need stereo). If you don't like the IR, it certainly won't matter whether you hear a difference. FWIW, I still use a mono rig, so I won't be using the IR in stereo. The difference it makes would IMO be lost in a live group context, and I don't record on a regular basis.
 
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ddhr

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532
Jay, thanks for sharing your IRs and your knowledge. My ears are not too sophisticated with this stuff and I appreciate your diligence and skill in working through your process.
 

the swede

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4,421
I've heard the ragged response and the dramatic differences from one spot to another that a 4x12 creates
It always bugged me back in the rehearsal room days. The 4x12’s in smallish rooms, hated it. When I had the money to my first amp I got a 1x12 peavey something. So much better… at least for me. I became anti 4x12 in band rehearsals because of the variance in places.
 

chrishurley

Silver Supporting Member
Messages
954
Thanks for the feedback. This is why I shared the IR. Do you have a stereo speaker system you can try as well? I've not tried 'phones myself (don't own any), so I have no idea if they make a difference.
I have a couple of other things I can try.

I will mention again that I think this is a very enjoyable IR to play through.
 




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