The Osprey-12 is the long awaited 12″ coaxial using Eminence Beta 12CX. As in the earlier Osprey-BR, I used the same compression driver, the Selenium D220Ti. This CD is modestly priced yet exhibits exceptional performance. For home use, I can cross at a low of 1.5kHz without stressing it.
Fig 1 – Eminence 12CX with Selenium D220Ti RAW Response
The plot in Fig 1 shows the relative loudness of the 12CX woofer and the Selenium D220Ti. Both measurements are the RAW responses, that is without any crossovers.
Fig 2 – Selenium D220Ti in 12CX
As in all horns, the difficulty lies in the control of the response. Get it wrong and the speaker falls apart. The Black plot (Fig 2) is the RAW response of the Selenium D220Ti through the 12CX short horn. Fortunately, it is sloping downwards linearly as the frequency increases. If not, I will have to find another CD.
The Red plot is with my High Pass network. The response now is flat at 95dB. This would make it easier to integrate with the woofer.
Fig 3 – Blue plot=12CX with Low Pass • Red plot=D220Ti with High Pass
Fig 3 shows the 12CX woofer and the D220Ti crossing at 1.5kHz. This is about the practical limit for the Selenium D220Ti. Actually, it’s not the D220Ti. She can go lower. It’s the horn that’s cutting off at 1.5kHz.
Fig 4 – Crossover Passband
The Black plot in Fig 4 is the summation of the 12CX and the D220Ti. The passband looks good. There’s some minor cancellation on the right of 1.5kHz but it’s not something I worry about. I can have perfect summation by removing the peaks at 2kHz to 3kHz in the 12CX roll-off but it would only add to the crossover cost. It wouldn’t make any difference during playback.
Fig 5 – Null Response
The Violet plot in Fig 5 is when I flipped the D220Ti wires around. What resulted is a deep notch centered at 1.5kHz. This is an indication that the two drivers are as good as time-aligned.
Fig 6 – Osprey-12 Frequency Response
Fig 6 is the final response of the Osprey-12. She is reasonably flat from 200Hz to 15kHz. There is a notch at 6kHz, followed by another at 12kHz. They are likely from cancellations in the horn.
Fig 7 – Osprey-12 Excess Phase
Fig 7 is the Excess Phase of the Osprey-12. This is actually quite an impressive excess phase plot. My previous crossovers have worse excess phase.
Fig 8 – Osprey-12 Spectrogram
The Osprey-12 Spectrogram (Fig 8) reveals the behavior of the frequency response with respect to time. The ringing in the horn is seen at 6kHz and 12kHz. In the frequency response plot (Fig 6), they are recorded as notches.
Fig 9 – Osprey-12 Toneburst Energy Storage
The Toneburst Energy Storage (Fig 7) shows what happens after the fundamental tone. It shows a massive amount of excess energy, particularly in the horn. This looks frightening but in reality, the Spectrogram shows the excess energy don’t last long enough for the ears to pick up. All excess energy from 2kHz onwards dissipated by 2 msec.
Fig 10 – Osprey-12 Waterfall
Fig 10 is the Waterfall plot of the Osprey-12. The excess energy at 6kHz and 12kHz are seen as longer decays. There’s actually another one at 16kHz. But all of them are inaudible.
Fig 11 – Osprey-12 Harmonic Distortion
The Osprey-12 distortion (Fig 11) is quite normal. Generally, the 2nd and 3rd distortions are about -55dB below the fundamental. What I didn’t expect is the rising distortion from 4kHz onwards. They are no cause for concern as they are 2nd harmonics (Red plot). The 3rd harmonics (Violet plot) are impressively low, about -65dB below the fundamental.
Fig 12 – Osprey-12 Step Response
The Osprey-12 Step Response (Fig 12) is not as pretty as the Condor-III. There are 3 peaks in the D220Ti as she reaches the top. This step is very similar to the 10CX that is used in the Osprey-BR. During auditioning, I couldn’t detect any adverse effects so nothing to worry about.
Fig 13 – Osprey-12 Port
The Brown plot in Fig 13 is the output from the port. I’m relieved that there are no sharp port resonance in the midrange. Presently, the ports are two pieces of standard 2″ PVC tubes used for plumbing.
Fig 14 – Osprey-12 Impedance
The Osprey-12 is not a difficult load. The Nominal Impedance is 8Ω (Fig 14). Nowhere does the Osprey-12 dip below 6.6Ω. The bass reflex tuning is 45Hz as seen in the saddle at left. There is a slight fluctuation in the electrical phase but it will not stress power amplifiers.
It took me a while to muster enough courage to work on this Beta 12CX coaxial. The main problem I had is with the Thiele & Small parameters that I extracted with DATS. They are not the same as Eminence specs. Actually worse. Even with the published specs, I already had difficulty deciding whether I should go for a sealed box or a bass reflex.
After months of procrastination, I finally bit the bullet and mounted the 12CX onto a 60 liters bass reflex. This is much smaller than the optimum size of 100 liters that’s recommended in my box simulation. I don’t really have much of a choice as 60 liters is about the largest box I can lift on my own. Don’t forget, it’s not an empty box. The 12CX and the D220Ti are mounted onto the baffle.
I played some music using the woofer only and was surprised the bass is quite decent. There’s more body and it goes deeper than the 10CX. Having established that, I proceeded to work on the crossover.
One would be tempted to use the Osprey-II or BR crossover but that’s not me. The 12CX and the 10CX are not the same drivers and I was proven right. Strangely, I need to rework the horn as well.
When I finished with the crossover, I gave the Osprey-12 a run for a few days. In the end, I would say the Osprey-12 exceeded my expectations. The vocal clarity and treble are outstanding but it is the bass that contributed to her musicality. The Osprey-12 is ideal for hifi and home theater. Tube amp owners will be pleased with her high sensitivity too.
For professional applications, I don’t recommend the Osprey-12 as is because I seriously doubt the D220Ti is robust enough for the abuse. If I insist on using the D220Ti, I would have to shift the crossover to 2kHz but I cringe at the thought. Swapping the D220Ti with the Eminence PSD2002 is a better option but I have no idea how well they’ll mate. I may explore this in future. Right now, I want to enjoy listening to the Osprey-12. She’s one of those speakers you fall in love with the minute she sings.
Unless otherwise stated, all measurements were made in Full Space (4 pi) with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.
August 23, 2021Projects