QUESTION: How are you determining that there is a problem at 100-Hz? By ear? By examining a real-time spectral meter? THOUGHTS ON STUDIO MONITORSAs a bit of follow-up, I checked the specifications for the M-AUDIO Studiophile BX8a Deluxe - 130-watt Bi-amplified Studio Reference Monitors, and it is
good that the frequency response is 40-Hz to 22,000-Hz, but the full-range of normal human hearing is 20-Hz to 20,000-Hz, which is fine at the high-end but not so good at the low-end . . .
Studiophile BX8a Deluxe - 130-watt Bi-amplified Studio Reference MonitorsHowever, the low-pitch "
E" string on an electric bass at standard tuning (Concert A = 440-Hz) is 41.204-Hz, which maps nicely to the low-end of the frequency response being 40-Hz . . .
The very low bass frequencies are more focused on kick drums and other percussion stuff, but they are important . . .
And while the specified frequency response is 40-Hz to 22,000-Hz, this allows lower frequencies but just not at the same volume level, which is where calibrating can be helpful, although it depends on the way the calibrating is done . . .
From what I can determine by the specifications, these should be
good studio monitors, and I like the lower range of the frequency response, but the strategy I use here in the sound isolation studio is based on focusing on the
full-range aspect with specific attention to the basic principles of acoustic physics, where for low frequencies the fact is that deep bass maps to "big and heavy" woofers no matter how "big and heavy" is done, where it can be done with a 15" woofer, a pair of 12" woofers, or a set of 8" or 10" woofers, as is done in the classic Ampeg bass guitar loudspeaker cabinet, as well as with the now rare Fender Custom Shop Rumble Bass rig (a personal favorite) which was available for a few years in the late-1990s and has cabinets with four 10" loudspeakers, as well as a 300-watt vacuum-tube power amplifier that is mind-boggling and generates so much heat that it requires a set of high-power cooling fans . . .
The basis for the strategy I use here in the sound isolation studio is the fact that the folks who do sound reinforcement for musical groups tend to have a
different perspective than musicians and singers, which maps generally to being concerned solely with acoustic physics, which curiously maps to DJ and PA loudspeaker systems (a) being better than everything, including so-called "studio monitors", and (b) vastly low prices, where the latter aspect is due to sound reinforcement folks generally having the view that musicians and singers have entirely too much self-esteem, often in the extreme, which is an abstruse way of explaining that promoting a guitar amplifier as being "fantastic" because Ace Frehley (KISS) or any other famous lead guitar players uses it is meaningless, because all that matters are the loudspeakers, cabinets, preamplifiers, and power amplifiers . . .
Consequently, my strategy is to use a pair Kustom KPC15P 15" Powered PA Speakers (purchased separately rather than as a pair, which for some puzzling reason saves approximately $50 [US] compared to the cost of a pair), which at present cost $130 (US) per loudspeaker and amplifier unit . . .
The specified frequency response is 60-Hz to 20,000-Hz, but since they are "big and heavy" and massively amplified, I run them at a very low volume and push the low frequency range downward, which at low volume levels does not cause a problem by damaging the 15" woofers, and this is possible in part because the sound isolation studio is approximately 6' wide by 7' tall and 12' long, which makes it similar to a walk-in closet with a low ceiling, hence two 100-watt amplified PA loudspeaker units are so overpowered that running them at full volume would cause irreparable hearing loss . . .
I have a NADY SPL Meter, and I use it to set the listening level in the range of 80 to 85 dB SPL, which is at the high-end of what is tolerable and conveniently maps to a nearly flat frequency response or "equal loudness curve" once the loudspeakers are calibrated . . .
All this stuff is explained in detail in my topic in this FORUM, and one of the stellar insights which appeared with a bit of serendipity is the vast importance of determining whether one is (a) a fundamental tone hearer or (b) an overtone hearer, where the former folks are the only ones who actually hear everything and are not easily fooled or mislead by the "Missing Fundamental" auditory illusion . . .
The Fabulous Affordable Studio Monitor System Project (IK Multimedia FORUM)Missing Fundamental Auditory Illusion (wikipedia)THOUGHTS ON ACOUSTIC TREATMENTSI like the concept of the London 12 Acoustic Kit, for sure . . .
London 12 Room Kit (Primacoustic Acoustic Solutions)For sure! 
Another stellar technique is to get a few rolls of fiberglass insulation, which you leave rolled and put in the corners of the room, where they absorb excessive deep bass . . .
The key bit of information is that you need to check the acoustics of the room with microphones and calibrating equipment to determine precisely how the room is behaving, and this can be a bit complex, but the ARC System (IK Multimedia) is an affordable solution, and I use it here in the sound isolation studio . . .
But I also have a Behringer DEQ2496 Ultra-Curve Pro Mastering Processor, which I am planning to use sooner or later, since it works independently of the computer and Digital Audio Workstation (DAW) software, plus it has a calibration system and a matching calibrating microphone which curiously looks nearly identical to the calibrating microphone that comes with the ARC System, but it is tiny bit different, and so forth and so on . . .
The reason at present that I have not done a lot of the calibrating stuff is that the Kustom loudspeaker units already are reasonably flat, and I tend to be a bit lazy with respect to running cables and reading instruction manuals, but so what . . .
So what! Another key aspect is that I designed the sound isolation studio specifically to have neutral acoustic behaviors . . .
SUMMARY
In some respects, I am a bit bored and and I like to write, but overall I am intrigued by the problem of a bit of "boominess" at 100-Hz, and these are a few more thoughts on possible explanations and solutions . . .
If you have T-RackS 3.5 Deluxe, I can provide some advice on different strategies for smoothing the frequency response of the bass guitar and Ampeg SVX emulation software, which certainly is one way to solve the problem, but this is something that happens in listening rooms which have "hot spots" . . .
Without doubt, you can use the T-RackS 3.5 Deluxe Linear Phase Equalizer to smooth the frequency response of the electric bass rig, and it is not difficult to do, since basically all you need to do is to use it as a parametric equalizer, where using the controls you create a "notch" centered on 100-Hz, which looks something like the following screen capture, which for reference has an exaggerated "notch" to make it easier to see . . .
[
NOTE: I reduced the volume by -10 dB to make it easier to see the "notch", which is a lot, so in practice it probably only needs to be reduced by -0.5 to perhaps -3 dB, depending on several factors, and the width of the notch can be varied, as well . . . ]
Linear Phase Equalizer ~ Detail ~ T-RackS 3.5 Deluxe (IK Multimedia)SUGGESTION FOR AN EXPERIMENTIf you have a way to output a section of the electric bass track where the 100-Hz problem occurs, I can run it through some of the VST plug-ins I have here in the sound isolation studio to get more information, where (a) an AIFF, WAVE, or MP3 audio file will be fine for doing the experiment and (b) the notes can be a simple scale or whatever, with 30 seconds to 1 minute being a nice length, with a chromatic scale from the low-pitch "
E" string to the "E" on the low-pitch "
D" string will work nicely, although extending the scale to 5th fret of the low-pitch "
g" string is better . . .
Another though comes to mind, which is that if you are playing a real electric bass and running its output signal to the computer, the problem might be simply a matter of pickup in the area of the low-pitch "
A" string on the electric bass being too hot, which you probably can adjust by lowering the pickup or, if it has separate screws for string, then lowering the respective screw height . . .
Lots of FUN! 
