I got my DPA 4099, bundled with the DAD4099 pre-amp with XLR adapter, a week ago and mostly love it but have been grappling, since then, with how best way to deal with all the issues discussed here: phantom power; feedback; impedance matching; tone; resisting gear bloat, etc.
Let me start by saying, I haven't tried this mic with my upright bass yet - I'm focused on getting a good sound with my nylon string guitars, especially my 7-string, tuned to A1 (55 Hz, same as A string on the bass).
Phase reverse is the single most important thing I have found to make this mic sound great.
I tried different phantom power voltages (15v and 48v) and I think 15v was a tiny bit more noisy, but it didn't seem to affect the EQ issues.
Then I decided I needed a really good set of notch filters, not just one or two notches, with some wide bandwidth like 1/3 octave, which is common and sucks away tone, besides getting rid of feedback. (The more narrow the filter 'Q' (bandwidth), the better control you have over feedback, without compromising overall tone.)
I considered getting an automatic DSP feedback eliminator, but didn't want to risk having to give up control and possibly deal with computer hiss, etc. I finally bought a very nice analog equalizer: Rane PE-15 Parametric Equalizer, with variable bandwidth, center, gain and bypass on each of the five filters, not to mention shelving EQ at top and bottom ends.
This is way better than one or two notch filters: it is dead quiet and I can slowly turn up the gain and then zero in on killing any feedback, using just the minimal amount of attenuation, with the narrowest bandwidth on the filter. Though it handles feedback nicely, I still noticed the tone was a bit thin until I tried flipping the phase and it seemed to brighten and balance the sound a lot.
Here are a few more things I've discovered.
A very high frequency squeal easily pops up at around 10 kHz, this may be due to the boost that the DAD4099 provides there. Not sure, but watch out: I simply shelve everything > 10 kHz for now and it sounds fine to me.
Feedback is also very prevalent at around 100-150 Hz, then again at ~250 Hz and ~750 Hz, in my case, with the mic on a guitar.
Please see the 4099 manual: p. 23 has some helpful graphs of performance with and without the pre-amp cut-off, at both 20cm and 10cm.
[Invalid or Expired Link Removed]
As the graphs show, at 20cm, without the DAD4099, the mic is pretty flat, except for a ramp from around 5 to 10 kHz.
At 10cm, however, proximity effect results in going from flat at 500 Hz (above the range, of most basses, near B4, 493.9 Hz, the octave on the B string of the guitar) to a maximum of about 4 dB gain at around 200 Hz (near G3, 196 Hz: the octave on the G string of the bass), after which it levels off.
In other words, without any pre-amp bass cut, at 10cm distance, this mic would deliver a graceful bass boost throughout the normal playing range of the bass: everything below the octave on the G string.
With the use of the DAD4099, however, you get a roll-off of about -10 dB throughout this same range, both at 20cm and at 10cm - the difference being that, at 10cm, DAD4099 gives a resonance peak at around 150 Hz (exactly where I notice it being most prone to feedback), whereas, at 20cm response falls off from flat at around G3 to -10 dB at E1: you would probably just say that your bass sounds too thin, since most of us like to boost the bass, to compensate for the decreasing sensitivity of our hearing which is normal, as frequency declines in this range.
In other words, for bassists using the DPA 4099 mic, proximity effect is your friend; the DAD4099 may be your foe.
If I had known what I know now, I would have ordered the DAD6001-BC XLR adapter (flat response version), instead of the DAD4099 and maybe also avoided that horrible 10 kHz squeal, likely also caused by the preamp boost!
Some have reported elsewhere on this forum that DPA tech support told them that the 80 Hz cut-off provided by the DAD4099 pre-amp was for controlling proximity effect, however the manual says something different:
"....The DAD4099 adapter features a permanent second-order
low-cut filter at 80 Hz. The filter minimizes handling and wind
noise at the microphone output without compromising sound
quality, as guitar, sax, trumpet and violin have no appreciable
frequency response below 80 Hz."
I have a few problems with this statement:
1) First of all, guitar is quite often tuned down to D2 (73.42 Hz)
2) Seven string guitars are often tuned down to A1 (55 Hz)
3) The same mic and preamp (with 80 Hz cut-off) are sold to bassists who often tune down to C1 (32.70 Hz) or B0 (30.87 Hz)
4) The natural 'warmth' of both guitar and bass is effected by resonance below the frequency of the lowest string.
It almost seems that this mic was marketed to bassists, after becoming successful with other instruments, yet bundled with the same preamp, almost without concern for the true nature of the instrument.
I do not even know where I can buy the DAD6001-BC XLR adapter. DPA doesn't seem to sell it directly and I cannot find anyone who sells it.
In any case, keep the mic close to your bass and it will probably sound pretty good, as long as you have a phase reverse option and at least one notch filter to control 150 Hz feedback.
It was an amazing experience having Scotty's bass!
