Starling-TPC (a Time & Phase Coherent 2-way)

Starling-TPC

The Starling-TPC takes the development of the Starling into the realm of Time and Phase Coherency made famous by Thiele and Dunlavy. Both these manufacturers are no longer around but their legacies live on. I will continue where they left off. 

For this project, I am using a step for the ER18RNX. This is the method favored by Dunlavy. The step brings the woofer forward but it is still not enough to align the acoustic center with that of the Seas 27TDFC tweeter. To do that, I replaced the Seas with a Peerless H26TG45-06. Now, their acoustic centers are close enough for Time and Phase Coherency to work.

Fig 1 – Seas ER18RNX RAW Response and with Low Pass Filter. Nearfield below 500Hz.

Working with the Seas ER18RNX is always a challenge. The Black plot in Fig 1 is the RAW response of the ER18RNX. As can be seen, it’s quite wild above 1kHz. This woofer will bite you if you are not careful. It took some effort but I eventually got this baby to roll-off the way I wanted (Blue plot).

Fig 2 – Peerless H26TG45-06 RAW Response and with High Pass Filter.

The Black plot in Fig 2 is the RAW response of the Peerless H26TG45-06 horn tweeter. The Red plot is with a High Pass Filter with additional networks added to adjust the roll-off slope as shown.

Fig 3 – ER18RNX with LPF and H26TG45 withHPF

Fig 3 shows the ER18RNX and the H26TG45 crossing at 2.5kHz. This is exactly my target crossover frequency. 

Fig 4 – Summing of ER18RNX with the H26TG45

The Black plot in Fig 4 is the summed response of the ER18RNX with the H26TG45. No cancellations are observed on either side of the crossover frequency, indicating the drivers are summing properly.

Fig 5 – Starling-TPC Frequency Response

For clarity, I removed the individual driver responses, leaving only the Black plot in Fig 5. This is the final Frequency Response of the Starling-TPC. 

Fig 6 – Null Response

Fig 6 is the Null Response of the Starling-TCP. The notch coincides with the crossover frequency of 2.5kHz. This confirms that the ER18RNX and the H26TG45 are indeed crossing at the targeted frequency.

Fig 7 – Starling-TPC Step Response

The Step Response in Fig 7 is what the Starling-TPC is all about. The step is still not 100% perfect though. The tweeter is leading the woofer by a few microseconds. With a bit more work, I can make it 100% but it will not make any difference during playback. As far as I’m concern, this is Time & Phase Coherent enough.

Fig 8 – Starling-TPC Waterfall

Fig 9 – Starling-TPC Spectrogram

The Waterfall (Fig 8) and Spectrogram (Fig 9) do not reveal any anomalies in the Starling-TPC. There is a light notch at about 1.2kHz but it’s nothing serious. This notch is seen as a small dip at 1.2kHz in the frequency response plot in Fig 5. My guess is it’s probably caused by diffraction at the baffle edge.  

Fig 10 – Starling-TPC Impedance

The Starling-TPC is a friendly load for power amplifiers. Throughout it’s working range, the impedance is well above 4Ω. The only time it touches 4Ω is at 3kHz. Electrical phase is remarkably flat except for a minor dip at 2kHz.

the sound of Starling-TPC

This is one speaker I can live with. The music is lifelike and sounds completely natural. Maybe it has to do with the Time and Phase Coherency thing. Whatever it is, once you hear it, there’s no turning back.

Baby One More Time (Britney Spears) is one of those difficult tracks to reproduce properly. One of the biggest issues is to get her singing to cut through the mix. Initially, the Starling-TPC couldn’t do it. Britney’s voice sounded restrained and the music was drowning her out. After I fine-tuned the ER18RNX, Britney came alive. Even the bass has clearer definition.

Up next is Annie Lennox (Medusa album). I thoroughly enjoyed No More ‘I Love You’s and A Whiter Shade of Pale. Listening to her with the Starling-TPC made me realized how good a singer she really is.

I was never a fan of Roy Orbison because the recordings that I heard were not very good, to say they least. Then I came across this album, A Love So Beautiful – Roy Orbison & The Royal Philharmonic Orchestra. When I heard it, I was stunned. Beautiful recording. But more than that, it made me appreciate the vocal prowess of Roy Orbison. Frankly, I’ve never heard a voice with this kind of vocal range. I think it spans 3-1/2 to 4 octaves. And he did not need to scream to hit the high notes. He just soars.

A good example is the first track – In Dreams. He was so effortless in switching octaves. And that vibrato. It just captivates the listener. In the entire song, you feel as though you’re floating through a dream. It’s eerie when listening with the Starling-TPC. It’s easy to forget that it’s a recording.

Of all my Starlings, this version, the Starling-TPC, is the best. It takes a bit more work to make the step but it’s well worth the effort. I will construct a proper box and make the step more attractive visually in a few weeks time. 

Crossover is available on request. Free for DIY. Not for Commercial use.
Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.