Falcon-II Baffleless Concept Speaker
The Falcon-II is an exercise in minimizing the effects of baffle diffraction. For those who are not familiar with baffle diffraction, it is the sound that’s bouncing off the baffle. I am particularly sensitive to this. I hear it as “glare”. It is that hardness in the upper mids, where vocals start to sound uncomfortable.
This brings me to the Dayton RS52AN, a 2″ aluminum dome midrange driver. The RS52AN is ideally suited for what I have in mind because it comes with a “closed back”. I can simply mount the RS52AN and a tweeter on a L-frame and have the assembly sit on top of any woofer box for testing.
Without a front panel to diffract sound, baffle diffraction is now greatly reduced. This results in improved clarity in the all important mid-range. Please bear in mind that the Falcon-II is not an Open Baffle design.
Dayton RS52AN Frequency Response
Fig 1 – Dayton RS52AN RAW Frequency Response without front panel
Fig 1 is the RAW response of the RS52AN without smoothing applied. Impulse window is 3.5ms. Note the hard knee at 5kHz. This is where the RS52AN dome starts to breakup. A sharp peak at 12kHz is consistent with metal diaphragms.
Crossing the RS52AN
Fig 2 – RS52AN Bandpass Response
The Blue plot in Fig 2 is the response of the RS52AN with a bandpass filter. Special attention was paid to suppress the 12kHz peak to -25dB. This effectively kills off the nasty peak. I’m confident it will not interfere with the treble now.
Crossing to the Peerless XT25SC90-04 Tweeter
Fig 3 – Frequency Response of RS52AN and XT25SC90
The Red plot in Fig 3 is of the Peerless XT25SC90 tweeter with a high pass filter. Acoustically, the two drivers are crossing at 4kHz. Note the tweeter SPL is 3dB lower than the RS52AN. This is due to the mic being placed on the axis of the RS52AN. If I adjust the tweeter output to the same SPL as the RS52AN, the treble will sound too bright.
Dayton RS52AN with Peerless XT25SC90 Spectrogram
Fig 4 – Spectrogram of RS52AN with Peerless XT25SC90
Fig 4 is the Spectrogram of the Summed Response of the RS52AN with the Peerless XT25SC90. Measurement is made with the Impulse Window at 3.5ms, therefore 20kHz down to 1kHz is free of room reflections. Zooming in to a 3ms Time Range shows an astonishingly clean response of the RS52AN and the XT25SC90.
Falcon-II Baffleless Concept Speaker Frequency Response
Fig 5 – Summed response of Dayton RS180s, RS52AN and XT25SC90
Fig 5 is the response of the Falcon-II when the RS52AN and the Peerless XT25SC90 is integrated with the Dayton RS180s. Measurements below 500Hz are inaccurate as they include my room reflections. The deep notch at 150Hz is cause by a floor bounce.
What is interesting is the exceptional smoothness of the midrange and the tweeter. Considering I did not apply any smoothing for this measurement, the response is quite remarkable.
Cumulative Spectral Decay (CSD) Plot of Falcon-II
Fig 6 – CSD Rise Time = 0.1ms, Window = 1.5ms (667Hz), Time Range = 1ms, Total Slices = 100
Falcon-II Toneburst Energy Storage (TES)
Fig 7 – TES at 3.5ms Window
The Cumulative Spectral Decay (Fig 6) and the Toneburst Engergy Storage (Fig 7) of the Falcon-II show minimal artifacts in the midrange and treble regions. This is further evidence of the spectacular performance of the RS52AN and the XT25SC90.
Falcon-II Step Response
Fig 8 – Falcon-II Step Response with mic on RS52AN axis at 1meter ( 5ms time window )
The Falcon-II Step Response is in Fig 8. The large peak is that of the Dayton RS180s. Note that the apex is about 0.35ms. This meets my objective of a faster woofer to go with the RS52AN mid dome.
Falcon-II Impedance & Phase
Fig 9 – Falcon-II Impedance & Phase
The Falcon-II is an easy load for power amplifiers. Lowest impedance is 4 ohms at 10kHz. Remarkably, there’s very little deviation in the electrical phase from 200Hz to 20kHz. Even in the bass region, phase is very well behaved.
Falcon-II Harmonic Distortion
Fig 10 – 2nd and 3rd Harmonic Distortion
Harmonic distortion is impressive. Generally, it’s -60dB below the fundamental. Of particular interest is from 500Hz to 10kHz. This is from the the RS52AN mid-dome and the XT25SC90 tweeter. Disregard the measurements below 500Hz. My room is affecting the measurements.
the Sound of the Falcon-II
If you love listening to vocals or instrumental tracks, look no further. The Falcon-II is the one.
The clarity of the midrange have to be heard to be appreciated. Totally transparent. No veil. No glare. None of my 2-way designs, even my Time-Aligned ones, can beat the Falcon-II in the midrange.
Vocals are bewitching. I actually enjoyed the Mamas and the Papas all over again. Their vocal harmony is still unmatched today.
Acoustic steel guitar like Paradise Cafe by Antar, is reproduced exceptionally well. Lots of detail in the strings.
Crossover Values & Box Dimensions
If you’re interested to build this project, kindly send me a mail for the crossover and box dimensions. For non-commercial use only.
This page was last modified on 19 Feb, 2018.