IR Properties

Discussion in 'Digital & Modeling Gear' started by Jay Mitchell, May 17, 2019.

  1. MaxTwang

    MaxTwang Member

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    Jay's email accompanying the IRs asks people not to share the IRs but to direct others to contact Jay for the IRs. With Jay's generosity with these IRs and the information in this thread it's a shame someone benefiting from his generosity wouldn't comply with his request.
     
    Last edited: Jun 15, 2019
  2. MaxTwang

    MaxTwang Member

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    I ran a Morgan AC20 Deluxe's EF86 channel though IRs C and 4x12 - 112 IR C loves the ef86 channel, big bouncy low end like the ef86 channel on the handwired AC15. The 12ax7 channel does well with the 412.
     
    Last edited: Jun 15, 2019
  3. Jay Mitchell

    Jay Mitchell Member

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    There's that, but my money says nobody's cheated. There's a strong probability that facefirst is just trolling here. His "opinion" is suspiciously short on detail: he said he didn't like C but said nothing about a comparison among it, A, and B. I'm pretty sure he has no clue how any of them sound, because he doesn't have them.
     
    Last edited: Jun 15, 2019
  4. AZG

    AZG Supporting Member

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    I've been playing around with the 3 1x12 IR in my Helix. A is okay. Sounds similar to many of the commercial IR I have. B is terrible IMO. C is really good. Sounds so clear, not boomy, balanced. I'm guessing this is Jay's fair field. Hoping he sends me the fair field 4x12 soon to compare to other stuff I have.

    Based off this one sample, I'm thinking this is where current modeling solutions most clearly are missing the mark. I would buy a good far field IR pack.
     
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  5. gigsup

    gigsup Supporting Member

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    Speaking to this...

    A member suggested I try a comparison, and it made sense:
    Shoot a sweep of the .kipr file loaded into the Kemper, and compare it to the original waveform from which the IR was generated.

    Using a Focusrite Clarett with Thunderbolt and REW generating the sweeps, I inserted the Kemper into the loop using the front input jack, and taking the measurement off of the "stack" output.
    No other block, effect, space, or EQ was on (that I'm aware of) in the Kemper unit.

    The results are shown below for two different cabinets.
    FWIW I tested the outputs of the Kemper from the Master section, and Headphone out as well as the Stack, they were identical.


     
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  6. Jay Mitchell

    Jay Mitchell Member

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    Makes sense.

    From the magnitude response differences in the displays, it is clear that the kpa does not convolve the original IR. The displayed spectral differences are definitely audible. There's potentially quite a bit more, however. Overlaid impulse displays of the same comparisons would provide additional information about audible differences.
     
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  7. djd100

    djd100 Member

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    I was able to try the JM FF 4X12 IR last night at stage levels (FF IR of a Egnater 4X12 with GB's), and like the JM FF C 1X12 it displayed increased authenticity and bested my other NF IR's easily. I used it with a Axe II's (Ares 1.03) Cornford M50 model (modded Marshall'ish...), out of some ancient 1X12 two-way EV PA speakers plus sub, in a rehearsal studio setting for classic rock'ish tones via three Les Paul's, two with HB's and a P-90'd single cut Junior for slide.

    I've also tried it with the Axe II's mic models as well to decent effect via my home studio's NS-10's (adds the various presence peaks and proximity's etc), but preferred it without any Axe II mic models at stage levels via the somewhat harsh/ancient two-way EV's plus sub. I also like many others found that the amp model's bright cap, tonestack, and presence controls were all that was needed to dial it in.

    Note that I converted it to standard .syx for the Axe II.

    Again, like the JM FF C, JM FF 4X12 sounds stellar, thumbs up (and thanks again Jay for sharing these, and for all the knowledge you've shared now and in the past as well!). :aok
     
  8. djd100

    djd100 Member

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    Quick question regarding reflection free'ish near field/close-mic's IR's...

    Assuming a large enough space where only the floor would represent reflections in the 20ms window, would hanging the cab 20' up in a 40' tall environment benefit the near field/close-mic's IR's?

    A PITA no doubt, just curious is all LOL?

    Thx...
     
  9. Jay Mitchell

    Jay Mitchell Member

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    Since the reflected sound has to make two trips - one out, and one back - you'd only need a little more than half that. If you place the cab at 12' with a 24' ceiling height, you could get a 20ms reflection-free IR. That would present some challenges: supporting the cab - a chain motor and fly points would probably be the best and least expensive equipment for that - and mic placement. An adjustable fixture that attaches to the cab and supports the mic (securely - dropping a mic from 12' would ruin your day) would be required. To move the mic, you'd have to run the speaker down to the floor, adjust the fixture, then run it back up to trim height. Road dogs can do this kind of thing in their sleep.
     
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  10. the swede

    the swede Member

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    Does reflection free...iness enhance the character (or makes it clearer because reflections masks the character?) of the cab or is the cabs character considered to be reflections?

    If so, the only character left is the speaker type and mic?
     
  11. Jay Mitchell

    Jay Mitchell Member

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    Once again:

    1. The sound the cab produces has no room reflections.
    2. The speaker you play the IR through will produce room reflections.

    Any room reflections captured in an IR will change the character of the sound of the cab. You may like that, you may not; the fact remains that an IR with room reflections sounds different than the cab it was taken from.
     
  12. Larry Eh?

    Larry Eh? Member

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    I've been wondering about the use of FF IRs at FOH. The purpose of a FF IR is to make a FRFR cab sound like the guitar cab that the IR models. If that FRFR cab is on stage, it replaces the guitar cab so the audience will hear it the same way they would hear a regular guitar cab with the sound source coming from the stage and its reflections off the stage floor, etc. But if you send the FF IR to FOH, then that will be like hearing a guitar cab placed where the PA speakers are. A NF IR to FOH sounds like a mic'd amp like we're used to hearing whereas a FF IR to FOH won't have this coloration of a mic'd cab. Does that mean that the audience will feel something is missing or will it mean a whole new clarity in guitar sound un-muddied by unnecessary reflections?
     
  13. Jay Mitchell

    Jay Mitchell Member

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    That assumes that "a mic'd amp like we're used to hearing" is a particular sound. It isn't.

    No.

    No.

    There is no magic bullet. The weakest link will always be the limiting factor. If the weakest link is the FOH PA or the operator thereof, nothing you can do with your stage rig will ever fix that.
     
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  14. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    Much as I like the sound of the reflection-free FF 1x12 IRs, I'm less confident that NF IRs would be the same sort of revelation. When we hear a FF IR through FRFR, it's "better" because we're not hearing reflections from the room where the IR was shot. OTOH, we're accustomed to hearing those reflections in NF IRs since every miked amp we've ever heard through FRFR had them. To some extent, I'd wonder if it's part of the sound we're used to from close-mic captures just like proximity effect is.
     
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  15. gigsup

    gigsup Supporting Member

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    This was my point of view earlier in this thread; that those sounds have informed the sounds we appreciate today.
    The problem is, it's a moot point, because the argument doesn't speak to the topic.

    With regard to an IR of a speaker/cabinet, the only mic that matters is the measurement microphone.
    In a close mic'ing application, the angle of the microphone has the greatest influence on the sound being recorded.
    In a far field mic'ing application, the angle of the speaker/cabinet has the greatest influence on the sound being recorded.
     
  16. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    What topic are we speaking to? If the topic is capturing the sound of the cab, NF IRs are irrelevant because they capture the sound of the speaker and mic (and reflections), not the cab. if the topic is getting the tones we're familiar with (NF or FF), then I think my point about reflections being part of the sound of a miked cab still holds up.
     
  17. djd100

    djd100 Member

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    Indeed, DOH!, I should've figured the distance LOL, and no, dropping a quality mic from 12' would certainly ruin my day LOL!

    I don't have a space with 20' plus ceiling aside from my studio's loading dock, and unfortunately we're 100 yards or a tad more from a major freeway, so I like many others am definitely in the market should someone make some for sale etc.
     
    Last edited: Jun 24, 2019
  18. djd100

    djd100 Member

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    Yes, I'd agree that the difference would be less dramatic, though practically speaking I'd be hoping for perhaps a smoother reflection free top and bottom end?

    It's my understanding that a reflection free NF IR that's truncated to say 20ms would sound smoother than a typical IR with reflections in part due to the fact that the reflection laden room tone is truncated (just guessing?), as well as the reduced comb filtering inherent in reflection free IR's?

    Jay, please correct me if my thinking is in space LOL!
     
  19. cliffc8488

    cliffc8488 Member

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    You need to turn off the Amp and EQ. Leave only the Cabinet enabled. Otherwise you are also getting the frequency response of the amp and eq. If you do this it should be pretty close.
     
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  20. Jay Mitchell

    Jay Mitchell Member

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    Different won't necessarily be revelatory, but it will definitely be audible. Here's a comparison I just constructed to hopefully give an idea of the potential magnitude of the differences.
    [​IMG]
    The green curve is the magnitude response of a reflection-free IR. The red curve is the result of adding a delayed (.8ms) duplicate of the IR to itself, but at a 10dB lower level. While this does not perfectly duplicate the effect of a floor reflection in an NF IR, gives you a pretty good idea of the way the response of a speaker can be altered by a very early reflection.
     

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