Topic: Diagnose this clipping problem

[relaxing]

Pulled a tape last night and every kick drum hit (and only the kick) came out clipped.
Actually, the first few kicks came out fine, and then I assume the sound guy turned it up and every kick after that was distorted. You can hear this in the recording attached.
I may have been very close to the subs that night, but I've taped by the stacks before and never had this problem.

What's going on here? It's not brickwalled, and it's not digital distortion. The meters looked good when I was taping, and obviously everything is well below 0dB.  I believe the artifact is visible as that curve/arc in the wave.

Advice?

[Belexes]

Lineage for your gear that you used? Mics, pre, deck?

[relaxing]

DPA 4061 stereo pair into Marantz PMD620 mic in.

[acidjack]

That is a tough one.  I feel like although the PMD620 is supposed to be able to provide plug-in power to the 4061s, it has to somehow be related to the pre on the 620, or the PA itself distorting.  The 4061s are, in my experience, virtually impossible to distort.

[relaxing]

Searching around some more, I found this page with a similar picture. Says it is a form of brickwalling.
http://jokerman.org.uk/lb/LosslessBob-what-images.html

So it was just the Marantz being unable to hand the extreme bass.
Does that mean it didn't matter how low I set my levels, I would have needed an attenuator between the mics and the deck?

Is the answer to finally grow up and quit taping in front of the stacks?

[Belexes]

Omni's are more sensitive on the low end. Could be brickwalling at the capsule.

[relaxing]

The 4061's are rated for 144dB though... well above the threshold of pain. Unless that's nonlinear through the low end. Need to study up on psychoacoustics 

[acidjack]

^^ I *think* your easiest solution would be to impose a cheap BB like the SPSB-8 from SoundProfessionals ($59) in between the 4061s and the 620 for super-loud situations.  Those are really nice mics, and frankly I doubt you overloaded the caps.  If you run line-in with a BB, I can't imagine you will ever get clipping.

[jefflester]

The 4061's are rated for 144dB though... well above the threshold of pain. Unless that's nonlinear through the low end. Need to study up on psychoacoustics 

Under exact DPA designed voltage, which is not what the 620 is supplying. I believe the 620 supplies the somewhat typical 5V which should be enough to power the DPA 4061s, but possibly not under all situations (like a loud bass transient)?

But acidjack's suggestion solves two potential issues - it ups the voltage to 9V and you use line-in to avoid possible brickwall on the mic-in (which you obviously can't do if you need the plug-in power on the mic-in).

[darktrain]

DPA 4061 stereo pair into Marantz PMD620 mic in.

were you using the -12 or -24 "pad" setting for mic in, i have used the 620 in some insanely loud shows using the mic in but always used the -12 setting and have never had a problem

[relaxing]

The pad was -12db... anyway the levels on the meters looked good. Never hit red so not sure what difference setting the pad lower would have made?

I have the sp-preamp, but I really wanted to carry around less gear when stealthing...

How do I know the brickwalling won't occur on the line in?

[it-goes-to-eleven]

How do I know the brickwalling won't occur on the line in?

You gotta test your rig bro.  What was the gain set at?

Based on my experience recording very intense bass with 4061's at 4.6 volts, I think it is extremely unlikely that was the issue.

[bugg100]

How much air were the subs moving? Enough to need a pop screen or wind sock?

[boojum]

AS the DPA's are rated at 144 dB, previously pointed out as above the threshold of pain and 24 dB past jet engines, I doubt the mic failed.  The 4061 was built to be usable under auto hoods.  So it would look like it is not getting the power it needs.  Borrow a BB for a test.  That's you best bet and as long as you do not damage the borrowed BB you are out no money.

You will still need the pre-amp with the BB.     ;o)

[Belexes]

I have the sp-preamp, but I really wanted to carry around less gear when stealthing...

Consider the Church Audio BB. I have it. Slightly bigger than a 9v and much smaller than the SP.