Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Dan Lawrence]

I have some questions regarding the use of the Little Labs IBP jr, which, for my purposes, operates the same as the IBP.

I am unclear as to the details of how the switches interact, and how one functions at all. I've download the info at Little Labs, but these details are not listed anywhere I can find them. I even wrote them, but don't seem to be getting through. So I ask here.

Firstly, I imagine that if one uses the "Phase Invert" button, the phase is flipped (180) and then any adjustments made on the sweep are in addition to the flip, so that one can go a full 360 around. Is this correct? Does the 90/180 switch interact w/ the phase invert button? (I assume the invert is fixed by definition, but don't want to assume anything).

I also want to be sure I'm clear, that 90/180 button is 90 degrees variation when pushed in and 180 while out?

The bypass button says "phase adjust bypass," does it also bypass the invert button, or just the sweep button?

Lastly, I am quite unclear as to the function and theory of "phase center hi/lo" button. I have noticed that at times the results using it are stark, and at others, imperceptible. I want to understand what's going on there so as to better tune my ears and upgrade my theory a little.

Wish I had a DAW to see waveform results, but for now, only my ears.

Thanks for your time.

d

[Fletcher]

I have some questions regarding the use of the Little Labs IBP jr, which, for my purposes, operates the same as the IBP.

I'll do my best... a couple of things will require experimentation on your part... but hopefully I can give you some stuff to ponder while you're experimenting.

I am unclear as to the details of how the switches interact, and how one functions at all. I've download the info at Little Labs, but these details are not listed anywhere I can find them. I even wrote them, but don't seem to be getting through. So I ask here.

Jonathan has been traveling [trade show stuff] -- I'm sure he'll get back to you as quickly as he can... understand he's a "one man show" so during trade show season [NAMM, Musik Messe, AES] it can take him a bit of time to respond -- other than that, he's usually pretty quick to respond [except when he's on holiday which he does a few weeks a year].

Firstly, I imagine that if one uses the "Phase Invert" button, the phase is flipped (180) and then any adjustments made on the sweep are in addition to the flip, so that one can go a full 360 around. Is this correct? Does the 90/180 switch interact w/ the phase invert button? (I assume the invert is fixed by definition, but don't want to assume anything).

Its not really a "phase invert" button [despite the labeling] but a "polarity reverse" button -- effectively there is little difference but if you think about the signal polarity being reversed rather than the "phase" being flipped I've found it a bit easier to wrap my head around it.

I also want to be sure I'm clear, that 90/180 button is 90 degrees variation when pushed in and 180 while out?

 

If I remember correctly its 0-90˚ with the button out and 90˚ - 180˚ with the button in.

The bypass button says "phase adjust bypass," does it also bypass the invert button, or just the sweep button?

Just the sweep

Lastly, I am quite unclear as to the function and theory of "phase center hi/lo" button. I have noticed that at times the results using it are stark, and at others, imperceptible. I want to understand what's going on there so as to better tune my ears and upgrade my theory a little.

First, you have to understand that the IBP is a variable "all pass filter".  The nature of any audio filter is one where you're going to alter the "speed" of the audio around the filter point of that filter.  So, say you have a "hi pass" filter that is set to 40Hz -- in addition to reducing the level of the audio from 40Hz down you're going to slow down the signal at and around that point -- this change in "speed" is what we call "phase" as you're altering the linear characteristic of the phase response of that signal at that point.

What the "hi/lo" button does is change the center point of the "all pass filter" [I think by an octave, but it could be more, or it could be less... I never actually asked Jonathan - I'm guessing because an octave seems sensible to me -- but I could be very wrong].

If you use the IBP on a bass DI signal [say you have a Mic track and a DI track]... you will hear the "vowel" of the character of the bass note change.  Its not "dramatic" -- but it does [VERY MUCH] help things fit together in the context of a mix / presentation of a song.

Wish I had a DAW to see waveform results, but for now, only my ears.

You won't see it on a DAW display as that display is the full amplitude of the waveform and the IBP works internally within the waveform.  What you're doing is "slowing down" a section of the frequency spectrum [pulling random numbers out of my ass] you'll slow down 300Hz in relation to how it was coming out of the speakers prior to the application of the IBP... but you won't change the overall level.  In fact -- you won't hear the thing work at all unless you use it in relation to another sound [like my bass Mic / DI example previously cited].

FWIW I've found the IBP works best on bass -- bass mic vs. DI;  bass composite vs. kik drum -- things like that.  It can work small miracles if you have two mics on a guitar cabinet as well -- turn the knobs and push the buttons until you get the "vowel" of the guitar sound you're working to achieve.

The reason the nomenclature is vague is because the thing never does the same thing twice... a 16th of an inch of difference in microphone placement gives you a radically different response when you're playing with the IBP.  FWIW -- it took me a long to time to wrap my head around using the thing... since I have, its an indispensable tool in my world [I used to have 2x IBP "heavy" and 2x IBP Jr. in my rack].

If you ever get a chance to play with the IBP "heavy" -- here is one of my absolute favorite tricks with it.  Have the bass player plug into a DI... send the signal back to the control room, go through a mic-pre and then split the output.  One side of the split goes to whatever processing you feel like doing to the DI signal [I generally compress the bass when I'm recording it] and then to storage.

The other side of the signal goes to the IBP "heavy", then using the "re-amp" function I send the signal out to the performance area via a Littlelabs STD and into the bass amp.

From there, the bass player adjusts the bass amp to get his desired tone in the room [remember, you can't hear the IBP working until you have a second signal to reference the IBP effected sound against] -- you mic the bass cabinet and bring that signal back to the control room, through a mic-pre / processing and send it to storage.

Now -- you bring the mic and the DI signal up on your console [I bring them up to the same level -- but that is absolutely not mandatory] and adjust the phase knobs and buttons on the IBP while the band is running down the song in rehearsal.  By doing this I can tailor the "vowel" of the bass sound to fit in REALLY well with the kik drum, guitars, etc. all while keeping the overall bass tone we were going for in the first place.

I can not even begin to tell you how much I love this little box!!  It literally changed the way I worked and thought about things... it also made me a little sad that I didn't have them about 15-20 years earlier than when they were released.

Peace

[Dan Lawrence]

Fletch, can't thank you enough for all that time and response. I will save the whole post to keep w/ my notes for my gear. FWIW ... So much of what you said mimics many of my experiences with the box. I said the hi/lo button sometimes has dramatic effects, yeah, that was aligning a bass DI w/ a Manley VOXBOX signal. (LUUUUV that thing for bass!) The hi/lo put the tone right in the pocket. For guitars I saw little effect, but the phase sweeping definitely helped tighten their sound. Glad you mentioned your memory of the 90/180 cuz my intuition would have me believe the opposite.

I did have one other question, which I hesitated to avoid long-windedness, but you touched on it, so I'll throw it out now.

Though I try to employ the KISS principle in all my recording (not the band, but the "keep it simple, stupid" philosophy) I just can't help reaching for the golden ring on guitar tone. I'm currently using a 3 mic set-up (when not using room mics like in my Rode NT4 post) and that is the classic Royer (121)/57 combo on the front, and some tip of LDC at the rear of the cab. I just find so much depth in that tone config.

Question 1)         Placed at exactly the same distance from the cone(s), should I expect different mics (or types of mics, say to to the fact that a Royer isn't a cardiod) to have different phase relations. (I read somewhere recently that not all mics are "phased" the same, and I'm not even sure what that means in terms of building design.) In practice, I noticed even the Royer seems slightly out of phase w/ the 57, though in the case I checked, they were on different amps, stacked, but I think I had the cones and not the coils aligned. When you talked about differences of "1/16 making a big difference w/ the IBP, I realized I need to find two assistants - one to play and the other to position mics!

Question 2) is a segue of Q1 ... which is , the rear cab mic (when using open back cabs ... a sexy combo of 1952 Fender Deluxe and Top Hat Super 33). I had hoped to eliminate phasing problems between the mics by placing the rear mic the exact same distance from the back of the coil as the front mics are from the cone, then flipping the phase. I have used a variety of LDC's, a Blue Mouse, Manley Cardiode Reference, and Josephson 716. Am I delusional thinking that this distance formula will cure my ills? If not, should the distances be measured from the same point in the speaker (that kinda makes sense, when I hear the sound of the question out loud). But again, question 1 may shed more light on all this, and then I'll need at least three or phase aligners to really roll with style. (The phase seldom seems to be a nice and neat 180 out, and just that little difference can really make to tone go from nice to ... wow!) I like wow.

Thanks again for all your time and effort on the forums,

D

[Fletcher]

"Exactly" the same place is a physical impossibility -- "damn close" is do-able, but will indeed net some kind of phase related interaction.  I've broken a lot [A LOT] of laws in my time... but so far I haven't been able to break the laws of physics 

What the IBP can do is allow you to play with the laws of physics using other principles of physics to achieve the desired result.  I mentioned before I had 4 of these beasts in my old room... I have indeed used all 4 when recording 1 sound.  I'm not necessarily proud of that, just stating that it can be done, and I have often [not always, but often] found that the result was well worth the time expenditure.

Using an R-121 and a 57 is a way to go -- same with adding a mic to the back... but you need to understand that no two drivers on the face of this or any other planet will be 100% identical.  You need to understand that each microphone will have its own frequency response and phase anomalies [however minute - they exist].  You need to understand that getting the two mics even as close as 1/64th of an inch equip-distant to the dust cap of a driver [arbitrary point of reference] still leaves 1/64th of an inch of "wiggle room" [though it carpentry its exceptionally precise - this ain't carpentry].

None of this really means fuck all in the grand scheme of things -- but it is something to have in the back of your mind as you're listening to the sound and trying to capture what you have determined is going to be the absolute best sound as it relates to the track at hand [and that sound's interaction with all the other sounds as you should Always Be Mixing].  Its all about aesthetic, and the reference to the other stuff that is already recorded [going backwards sucks!!].

Don't be afraid to waste lots of time looking for every inch of improvement you can find -- unless taking that time is sucking the inspiration of the performer which is FAR and away more important than the "tonal character" of the sound you're recording.

I hope this makes some sense.

Peace

[Jim Williams]

Combining two mics to achieve perfect phase response isn't likely to happen.

Mics are imperfect devices and even if matched, a 1/4" distance difference un-matches them. Even if you do, they won't match at all frequencies. A basic phase delay tool will not overcome frequency vs phase differences as it's a simple full bandwidth all pass filter. You will need to build a frequency selectable all pass function to try and tighting up those differences and that may not accomplish the desired effect.

It's sort of like trying to push down a ping-pong ball floating on water with your thumb.

[Fletcher]

I don't think the object is to get both microphones "perfectly" in phase [that would be a foolish endeavor at best] -- I think the object is to get the two microphones to make the sound larger without sounding "hollow" [or at least that's always been my goal]... the best tool I've found for the job of getting the two to sound "larger" without sounding "hollow" has been the IBP.

Neither here nor there - just my experience.

Peace

[Dan Lawrence]

I appreciate all that input. My biggest reason for wanting the technical details is because I'm almost always recording myself w/ no assistance. I gave up my bedroom to make an "iso" room so at least I can get a better picture of the sound than when the amp is 6 feet away from my head. I do a lot of trial and error pre-testing, but again, the need for several IBP's or something of the sort has become apparent if I want to continue this multi mic'ing technique w/ the best sound quality. FWIW, I do use "satisfaction" as the success meter. I wouldn't know what "perfect alignment" really is anyway. While all can be done more efficiently post tracking, I want to set the mics up in their most efficient config too. More importantly, I am striving to make as few A/D conversions as is practical, so re-recording indie tracks w/ new alignments is contrary to my ideal, but something I'm willing to try, but creates four times the D/A A/D conversions, before another D/A to A/D mixing stage.

That issue of frequency vs. alignment has been puzzling me, though I came to suspect it before Jim mentioned it, understanding the vary distances of wavelength vs. frequency.
Wouldn't that suggest that even w/ a single mic, varying freqs can reach it out of phase?

Well, thanks for the educational discourse. It's been really enriching.

d

[Fletcher]

That issue of frequency vs. alignment has been puzzling me, though I came to suspect it before Jim mentioned it, understanding the vary distances of wavelength vs. frequency.
Wouldn't that suggest that even w/ a single mic, varying freqs can reach it out of phase?

Yup - happens with a single mic as well... and it changes with altitude, air pressure, humidity, etc. 

Audio is at best an imperfect science... so control the things you can control [the resultant sounds that are recorded] and do your best to learn about the things you can't control... as the more you know the more you can work around impediments.

Peace

[Dan Lawrence]

Thanks again Fletcher. Don't know what I'd do w/o the forums. See ya round.

d

[druhms]

Just my 2 cents,

I love the IBP. I tend not to use it as a tool to fix phase issues when tracking multiple mics on one source, but more as a tool to obtain different flavors of tone while tracking.
Guitar amps, almost exclusively, are where i use these things. I cut using the typical multiple amp / mic setup and summed to one track...then double.  I do my best to get everything in phase by technique alone. Then I'll throw an IBP on every other mic channel. This gives me a lot of tonal options when doubling parts. Sometimes switching pickups doesn't work, or the guy insists on using his only guitar. Maybe the sound we are getting is spectacular, but on the double, just turn the knob a touch on 1 or 2 mics and it can change your tone in very pleasant ways.
JJ