High Performance Subwoofer Systems for Music and Home Theater Enthusiasts
 
The frequency response specification is obviously different for each of the 9 preset curves for Blackbird and Raptor Systems. Rather than list a number specification 18 times for the two Systems, the focus here, and the reason for carefully designing 9 curves for each system, is the result at your seat. You may opt for a higher F3 with a steeper roll off while playing some music discs because it appears to be “tighter” or because you wish to push the system to its maximum output levels. You may also prefer to watch bass-heavy movies with a roll off at 18 Hz or 10 Hz for the same reasons. Or, you may prefer to select the maximum extension curve to get the widest possible in-room bandwidth for all source material.
 
Unfortunately, accurate measurement hardware and software is necessary to achieve the best and flattest in-room response possible. In other words, you have to be able to “see” what your System is presenting in your room. There are various options for purchasing a calibrated microphone, PC interface and measurement software available today, as many people are realizing the importance of measurements to optimizing your audio sound system hardware. In the near future, we will add a page to this site that offers links to the best options, guides to making accurate measurements, how to select the best curve for your room or preferred listening pleasure and more.
 
The bottom line with specifications, after you’ve optimized your in-room frequency response, is listening level in dBSPL. As we’ve consistently maintained over the past decade or so, output is achieved by adding more displacement and amplification. That’s exactly why we offer Systems. The sonic signature from the 9 curve option is the same for every System. The only difference is the maximum potential output of each curve, realized by adding more displacement (more modules=more drivers=more displacement) and more amplification to drive the modules.
 
There is also a major advantage to owning a multiple module System. Many believe that multiple placement of subwoofers helps to smooth the frequency response. We’ve taken that concept to a new dimension. Nearly every White Paper, Study and Opinion on the subject views multiple placement from a 2-dimensional aspect. We decided to try a vertical placement (stacking modules) because in many rooms we’ve installed Systems into, a recurring theme appeared. The floor-to-ceiling distance caused a peak or a null (depending where the listening position was) at the frequency that equals the ceiling height times two. For an eight foot high ceiling, that frequency is approximately 70 Hz.
 
We selected a room and then selected the worst corner in the room for frequency response at the listening position. The measurement microphone was placed at the listening position and not moved from that spot throughout the experiment. Here is the response with a single module placed in the corner in which you can clearly see the huge dip at 72 Hz:
 
 
 
 
 
 
 
 
 
 
The full stack of 4 Blackbird modules is approximately 87” tall and sits completely in 2.76 square feet of space. Because the modules exert precisely opposite driver motion there are virtually no extraneous vibrations. Only sound pressure waves emanate from the column. To prove this, in our tests we included a stability test in which the stack rests on a wood disc of just enough diameter to accommodate the 4 legs of the bottom module. After frequency response measurements were taken, the stack was subjected to a few dozen of the most bass-heavy soundtracks ever recorded over a span of two weeks or so, during which the stack did not move from its original placement on the wood disc by as much as a millimeter.
 
Getting back to the original purpose for the test, notice that the frequency response has gone from (+/-) 20dB to (+/-) 8dB. More importantly, notice that the -30dB hole at 72 Hz is now completely gone! There is a +35dB gain from one module to 4 modules and, more importantly, the critical crossover region is nearly perfectly flat.
 
Here are the one module and four modules response traces normalized, showing the huge improvement using a single subwoofer placement location, but adding a third dimension to the placement:
Note that, when stacking dual modules vs one, the connection to the amplifier drops in resistance from eight ohms to four ohms. That effectively doubles the amplifier power, or adds +3dB of power. Note also that doubling the number of drivers adds +3dB of sensitivity against the amplifier power, so, as expected by the physics involved, the dual module sweep is an average of +6dB louder, all else being left the same. Finally, note that the dip at 72 Hz has begun to improve by 8dB versus the single module.
 
The next step was to stack two additional modules for a total of four modules, connected to two amplifiers for a total of another +6dB of additional headroom:
As you can see, the response is very non-linear, approximately (+/-) 20dB. Also notice that, right at two times the floor to ceiling distance in this room, the huge dip in response at 72 Hz. NOTE: the wavelength of 72 Hz is 188 inches. Half that distance is 94”, which happens to be the ceiling height in this room.
 
We then stacked a second Blackbird module onto the first and ran another sweep:
BLACKBIRD MIC’D AT THE SEAT
DIGITAL FEED FROM DVD PLAYER
Maybe you’ll decide to use the curve that best matches your particular room gain profile to achieve the deepest extension Or, you may decide to sacrifice a bit of extension for more output in the middle or upper ranges of the subwoofer signal. You may decide that, after experimentation, you simply prefer a curve that you think offers the best sound quality with a specific disc.   It may be that you’re searching for the  curve that works best with your receiver’s auto-EQ. Having that flexibility at your fingertips is like having nine distinctly different subwoofers at your fingertips, less the expense, complexity and clutter.
From Star Trek, chapter 1; the Nirada emerges from the singularity, with full extension vs an 18 Hz high pass filter engaged.
Yet another very difficult scene to reproduce from Star Trek (2009) in the first chapter where the Romulun mining ship Nirada emerges from the black hole. Both of these graphs are generated by using a microphone at the listening position with a Blackbird System #3 in a 3500 cubic feet room. The top spectrograph is a with the Blackbird System in full extension and the bottom graph is with the 18 Hz high pass filter engaged. This comparison gives an accurate description of what is missed when using a subwoofer that rolls off at 20 Hz, which happens to be the roll off point for most so-called “high end” subwoofers. All of the content below 20 Hz is attenuated and everything below 12 Hz is missing completely from the presentation of this scenes extraordinary sound design.
Let’s look at one of the most difficult soundtrack events to accurately reproduce ever designed, the scene where the huge dragon “Red Death” crashes into the ground in How To Train Your Dragon. A spectrograph capture comparison of the digital feed from the player vs the same scene captured with a microphone of a Blackbird System #2 at the listening position is shown. As the picture tells the tale, the reproduction is extraordinarily accurate all the way down to 3 Hz.
The Effect Of Different Curve Selection On What You Experience:
Here, the same scene from The Incredible Hulk is repeated 3 times; first with no filtering (which includes strong content to 5 Hertz!), next with the 10 Hz high pass filter selected and finally, with the 18 Hz high pass filter selected. The differences are dramatic to most listeners, but some prefer to forego the infrasonic experience for higher output. Not only is it your choice, there are 9 selections of frequency response in addition to what is shown. Go for the most accurate reproduction, opt instead for less extension with the highest output or select anything in between at the flip of a switch. It’s like having nine subwoofers all in a single system without having to change in-room placement.
Technical Data 
& Specifications
We then placed the tower in the best corner for flat response at the seats and this is the result, with no post smoothing EQ and no receiver on-board Auto-EQ: