The majority of the Cardinal projects are in 15 liter boxes. In this version, I’m examining the bass character when she’s loaded onto a 27 liters bass reflex.
Fig 1 – Black plot=830974 RAW Response • Baffle Width=9-1/2″
The Black plot in Fig 1 is the RAW response of the Peerless 830874 in this larger box. Baffle width is 9-1/2″. Disregard the deep notch ay 150Hz. It’s a floor bounce in my setup. Measurements below 500Hz includes room reflections. What I want to do is to balance the midrange with the bass.
The Blue plot is with a new low pass network. The midrange is very close to the bass level. The speaker is in full space (4 pi). Beware that in a small room, the bass may be overwhelming.
Fig 2 – Blue plot=830874 Low Pass • Red plot=Seas 27TBFC High Pass
The Red plot in Fig 2 is the Seas 27TBFC tweeter. The two drivers appear to be crossing at 2kHz.
Fig 3 – Black plot=Cardinal-TBFC-II Passband
The Black plot in Fig 3 is the passband of the crossover. There is a slight dip at 2.5kHz and 5kHz. They look like baffle edge diffraction. If I want a smoother response, I’ll have to use a waveguide with the 27TBFC.
Fig 4 – Cardinal-TBFC-II Frequency Response
Fig 4 is the final frequency response of the Cardinal-TBFC-II. The response is exceptionally flat except for the dip at 5kHz.
Fig 5 – Cardinal-TBFC-II Null
Fig 5 is the null when I flipped the tweeter wires. The tip is at 2.1kHz, very close to Fig 2.
Fig 6 – Step Response
The Peerless 830874 exhibits a fast transient. Astonishing, she hits 300 microsec at 95%. Overall, the step is very clean. No breaks in the attack.
Fig 7 – Waterfall
Fig 8 – Toneburst Energy Storage
The Waterfall (Fig 7) and Toneburst (Fig 8) plots show no excess energy from 1kHz~2kHz. There are some light blue slices from 3kHz upwards but I doubt they’ll present any issues.
Fig 9 – Spectrogram
As I had anticipated, the treble is clean. Actually, this is one of the cleanest I’ve ever seen. Lower down, there’s a streak at 1.1kHz. It is dissipated by 7 msec. I don’t think it’ll smear the vocals.
Bass Reflex Alignment
Fig 10 – 830874 box modelling
Fig 10 is the box modelling of the Peerless 830874 for a maximally flat response. F3 is 43Hz. For a smaller box, like an 18 liters bookshelf, the F3 is 50Hz.
Sound of Cardinal-TBFC-II
In my initial crossover, I felt I wasn’t getting the kind of bass that I wanted. After a couple of days, I still couldn’t digest the sound. She sounded plain. Totally unexciting. I eventually threw out the crossover and did it by ear. A tweak here, a tweak there and the music came to life. The measurements above are the ones after adjustments. Goes to show one simply can’t rely on measurements alone. Speakers are meant to be listened to with ears, not microphones.
Comparing the Peerless 830874, 835025 and the SB17NRX all in 27 liters bass reflex boxes, this Cardinal-TBFC-II is the most musical. It’s completely due to the crossover. There’s punch and tempo in the beat. Very enjoyable to listen to.
The stands for the Cardinal-TBF-II has a direct impact on the bass quality. For best results, the height of the tweeter should be at exactly 33 inches from the floor. Lower than this, the bass will be stronger but it’ll lose it’s definition.
Crossover is available on request. Free for DIY. Not for Commercial use.
February 6, 2021Projects