Raven-TBFC (Dayton RS180s-8 with Seas 27TBFC)

27L Bass Reflex Tower

The Raven-TBFC is a continuation of the Raven tower line. The objective of this 27 liters tower is to extract more bass in a conventional 2-way design. As the name implies, the tweeter is now a Seas 27TBFC. Matching the RS180s-8 with a Seas 27TBFC elevates this design as the Seas is superior to the Dayton RST28A-4 that was used in the previous Raven-RST.

Fig 1 – Black plot=Dayton RS180s RAW • Blue plot=with Low Pass Filter (LPF)

The Black plot in Fig 1 is the RAW response of the RS180s-8 with a baffle width of 9-1/2″. Disregard the notch at 150Hz. It’s caused by a floor bounce in my setup.

What I’m looking for is the relative loudness between the bass and the midrange. Attenuating the midrange is the key in a 2-way when I’m aiming to get the bass to stand out.

After some adjustments with the tweeter in place, the Blue plot is the RS180s-8 with the Low Pass network.

Fig 2 – Dayton RS180s-8 Low Pass • Seas 27TBFC High Pass

The Red plot in Fig 2 is the Seas 27TBFC tweaked for this bass reflex. The two drivers are crossing at 1.7kHz. These two plots were arrived at after numerous auditions.

Fig 3 – Raven-TBFC Passband

The Black plot in Fig 3 is the summation of the crossover. No cancellations are seen in the passband which is an indication of optimal crossover phasing.

Fig 4 – Raven-TBFC Frequency Response

Fig 4 is the final frequency response of the Raven-TBFC. The midrange is at the same level with the bass as is the treble. 

Fig 5 – Raven-TBFC Null

When I flipped the tweeter wires around, it resulted in a null centered at 1.7kHz. I did not set out to achieve this. I adjusted the crossover by ear instead of blindly following measurements.

Fig 6 – Raven-TBFC Step Response

The Step response of the Raven-TBFC looks much smoother than the Raven-RST. I have no idea why because it’s the same Dayton RS180s-8 woofer.

Fig 7 – Raven-TBFC Waterfall

Fig 8 – Raven-TBFC Toneburst Energy Storage

The Waterfall (Fig 7) and Toneburst plot (Fig 8) recorded some excess energy at 2kHz. I doubt they are harmful because they last for only 6 cycles at most.

Fig 9 – Raven-TBFC Spectrogram

The Spectrogram in Fig 9 shows a very clean reproduction above 1kHz. There is a delayed hot spot at about 2.2kHz which is about -65dB below the fundamental. They won’t smear the treble because they are dissipated by 5 msec. 

Sound of Raven-TBFC

It took me a while to tune this Raven-TBFC but it was worth the effort. At first, it was getting the midrange and the treble to integrate properly. That in itself was one big circus. After that, I wasn’t too happy with the bass. I wanted more dynamics. More work. Once I got the rhythm in the bass right, it sounds perfect.

In voicing the Raven-TBFC, I used disco music. Even though they are from a bygone era, what I like about it is the dance beat. Disco Inferno (The Trammps) is one such track. I used this recording for bass articulation. In Car Wash (Rose Royce), it’s that disco beat I mentioned earlier. And that bass guitar running through the song. It’s as though the guitarist is the second star. For bass punch, I turned to Knock on Wood (Eddie Floyd). The Raven-TBFC performed fabulously in all these songs. Ah, the memories. The world was more innocent fifty years ago.

How does this Raven-TBFC compare to the Raven-RST. Personally, I prefer this version. The bass is more dynamic. Makes me want to dance. 

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.