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Author Topic: Micing the bass cabinet  (Read 10086 times)

David Sturzenbecher

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Re: Micing the bass cabinet
« Reply #20 on: May 26, 2016, 03:02:06 PM »

If you are on a digital desk that runs plugins, check out "inphase" from waves for a supper quick and easy way to align two inputs like this.


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Doug Fowler

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Re: Micing the bass cabinet
« Reply #21 on: May 26, 2016, 04:02:39 PM »

As usual-it depends.

A DI will give the cleanest sound.  But in some cases, the sound of the bass is SUPPOSED to be dirty. 

That is what they are looking for.

So a mic is the best way to deal with that.

HOWEVER-if you use both a mic and a DI, when both are used at the same time, you can have some serious issues.

The main thing being the latency between the mic and the DI.

That is called "combfiltering".  Maybe you have heard me mention it before ;)

Let's assume a analog bass path.  Digital anywhere after the DI point will add latency.

But since the mic cannot be on the speaker cone-it is some distance away.

This distance (between when the signal comes out of the amp) and before it gets to time mic take time.

And that time is latency.

So the signal coming from the DI and the speaker arrive at the console inputs at different times.  Ie combfiltering.

If you have a digital console you can delay the DI input.

The problem is "how much"?  The "proper way" would be to take an impulse response measurement of the signal going into the DI and the mic-figure out the time difference and add it to the mic.

But most people will not take the time to do that-or don't have the tools/knowledge to do so.

So we are either left to guess at what time "sounds best" or do nothing.

In the old analog days, the only tool we had was polarity.

That would sometimes help or hurt.  We just played with it until it sounded "better".

But unless the time is exactly correct, there WILL be cancellation and peaks at various freq.

So be careful in what you, why you do it and HOW you do it.

But all this only matters if you care about getting the best sound.

But sadly these days-sound quality is not up on the top of most peoples list. :(

During measurement training I play examples of

1.  Kick drum with two mics, separated a foot apart at equal level.  It's not subtle cancellation. Think B52 and SM-91 on the same drum. 

2.  Bass with mic and DI. Again, not subtle. 

Most people don't think about this stuff. 
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Art Welter

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Re: Micing the bass cabinet
« Reply #22 on: May 26, 2016, 05:52:39 PM »

During measurement training I play examples of

1.  Kick drum with two mics, separated a foot apart at equal level.  It's not subtle cancellation. Think B52 and SM-91 on the same drum. 

2.  Bass with mic and DI. Again, not subtle. 

Most people don't think about this stuff.
Doug,

Another thing few think about is the difference in phase response of a dynamic and condenser microphone insures they will not combine perfectly even if placed in the same position.

My standard operating procedure for combining a bass mic and DI has always been to ask the bass player to play a sustained low E (or B) while switching polarity on the DI to see if one position resulted in greater bass response. I continued that procedure even when using boards without polarity switches to make sure the combined response always sounded more "full".

Several years ago I measured the phase and frequency response of the active direct boxes normally used for bass and found they were wired pin 3+, the opposite polarity of the current pin 2+ microphone standard. Even though convention would indicate a polarity reversal would be required, in several hundred different listening tests over the past 20 years, found the difference in phase response between the a miced speaker cabinet and the direct output of the pickup or amp are so far off that it was rare to find that the combination of the reversed polarity DI and mic did not result in at least 3 dB more overall output than one or the other.

In roughly 75% of bass players, I prefer the mix of DI and miced cabinet (or miced upright bass), in the remaining 25% that the combination did not sound better found about equal preference for one or the other.

Art
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Jim McKeveny

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Re: Micing the bass cabinet
« Reply #23 on: May 31, 2016, 07:44:16 AM »

During measurement training I play examples of

1.  Kick drum with two mics, separated a foot apart at equal level.  It's not subtle cancellation. Think B52 and SM-91 on the same drum. 

2.  Bass with mic and DI. Again, not subtle. 

Most people don't think about this stuff.

The K.I.S.S. Principle rears its sensible head again! Adding additional complexity, cost, and effort often produces retrograde results...
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Doug Fowler

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Re: Micing the bass cabinet
« Reply #24 on: May 31, 2016, 12:33:15 PM »

The K.I.S.S. Principle rears its sensible head again! Adding additional complexity, cost, and effort often produces retrograde results...

Agreed.  I do understand why this was a standard R&R setup.  Thud from the B52, attack from the 91.  If that's your sound then it is what it is, alignment issues aside.  But I'm sure many never even considered what's actually happening.

Depending on where the two mics sit in relation to the source (the head/beater), it's entirely possible (I think :-) to get cancellation exactly in the area one would normally cut in the low mids for this type of sound.  The depth of the drum would be in play, though, and one of the mics would surely be well outside the drum.  In a live situation this probably would not happen, but a smart studio engineer might use this successfully. 

Let's say we wished for cancellation near 350 Hz, generally an area one might carve out for a R&R kick drum.

So using t = 1/f, we get a time value of about 2.8 msec with f = 350.  But that only yields the frequency of interest.  The first notch is an octave above, so we actually need 5.6 msec spacing, or about six feet for the first notch to be near 350 Hz.  This clearly would not be easy or desirable in a live situation, but in the studio it's entirely possible.  Of course the two microphones have to be at equal level for max effect.

Otherwise, inside the drum with both mics and equal level, it just sounds hollow and "phasey".  Different mic models mitigate it somewhat (different phase response), but the effect is still there.

But again, if you just need the thud and the whack, well there's yer B52/SM91 solution.  And if it sounds good, it _is_ good.

Check my math please ;-)

edit: 350 is the frequency value, not the time value.  oops....
« Last Edit: May 31, 2016, 02:10:34 PM by Doug Fowler »
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Jim McKeveny

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Re: Micing the bass cabinet
« Reply #25 on: May 31, 2016, 01:59:29 PM »

... a standard R&R setup. 

The universal rock and roller tombstone: "Seemed like a good idea at the time".
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Re: Micing the bass cabinet
« Reply #25 on: May 31, 2016, 01:59:29 PM »


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