Sparrow-X (SB Acoustics SB13PFC25-08 with HiVi RT1C-A)

HiVi RT1C-A Planar Isodynamic Tweeter

I have the RT1C for many years but never used it much because of the high crossover frequency. It needs to be crossed at 4kHz and the 6″ woofers that I had then do not extend up that that frequency without cone breakup. Even my HIVi M5a sounds brittle when crossed at 4kHz.

Having just finished working on the Sparrow, where I used the SB13PFC up to 4kHz successfully, I am confident that it would be a perfect mate for the RT1C-A planar tweeter. It is not my policy to use a tweeter that cost almost double that of the woofer but since I have both, why not.

As luck would have it, the cut-out of the Tang Band W5-704 fits the SB13PFC exactly. Out came the Tang Band W5-704 from my Oriole and the Sparrow-X is born.

Sparrow-X Frequency Response

Summed Response of SB13PFC25-08 with HiVi RT1C-A

Fig 1 – Summed Response of SB13PFC25-08 with HiVi RT1C-A

Disregard the deep notch at 150Hz. It is caused by a “floor bounce”

The Black plot in Fig 1 is the Frequency Response of the Sparrow-X. To get this, the RT1C must be wired in Reversed Phase. When the RT1C is connected in-phase, it resulted in a notch (Violet plot). It is not as deep and symmetrical as I would like it to be but it’s perfectly fine as I did not detect any phasing issues on playback.

Sparrow-X vs Sparrow

The bass of the Sparrow-X is “fuller and deeper”. That’s due to a larger volume of the box. This Sparrow-X is loaded into a 13 liters bass reflex whereas the Sparrow is almost half, at 7 liters.

The vocals of the “X” are slightly more forward than the Sparrow. There’s no veil in the mid-range. Voices and instruments are well isolated in the recording.

The treble, obviously, doesn’t sound the same. The RT1C produces exceptionally refined highs. However, that is not so say the TN28 is a bad tweeter. You would not know the difference unless in an AB test.

Is one better than the other?

Not really. If space is a constrain, the smaller Sparrow obviously wins. If you want a tighter bass with a bit more punch, again, it’s the Sparrow.

The Sparrow-X is the speaker of choice when you want the bass to sound “more natural”. Some would call it more “Hi-Fi sounding”.

The important point is one will suit your preference and hopefully your listening room.