18 Sound XT1086 with Peerless DFM2535

18 Sound XT1086

In my previous posts, I touched on two popular vintage horns, namely a JBL 2370A and an EV HT94. Now, I’ll examine a modern horn, a XT1086 by 18 Sound.

If I’m not mistaken, the XT1086 is a Constant Directivity horn but with a major difference. It has no sharp corners in the flare. The flare walls are smooth throughout, unlike the older CD designs. Flare rate is Elliptical with a Spherical wavefront.

In traditional constant directivity horns like the EV HT94, constant directivity starts at 3kHz. With the XT1086, it’s at an astounding 1.4kHz. Dispersion is 80ºH x 60ºV. I was quite taken aback when I saw this. A Vertical coverage of 60º is highly desirable. Normally, it’s only 40º. With this wider coverage, integration with the woofer is improved. This will result in a better vertical dispersion in the loudspeaker.

But it’s more than constant directivity. This horn is touted to be very “clean”, meaning very little internal reflections when sound is moving through it. With a well matched compression driver, there is minimal artifacts. This degree of precision can only be achieved with the aid of computers.

18 Sound XT1086 with Peerless DFM2535R00-08

Fig 1 – 18Sound XT1086 with DFM2535 RAW Frequency Response.

I tested it with my collection of compression drivers and found the Peerless DFM2535 to be the most promising. As seen in Fig 1, there are virtually no peaks and dips in the response. There is a very slight depression close to 3kHz but I won’t worry too much about it. The horn cuts off at 1.4kHz which is where the constant directivity starts. Unfortunately, I have to cross the DFM2535 at 2kHz for I doubt it’ll survive at 1.4kHz in pro use.

Fig 2 – 18Sound XT1086 with DFM2535 Impedance

Fig 2 is the impedance of the 18Sound XT1086 with the DFM2535. It shows a beautiful single peak at resonance. More importantly, it’s at a low of 743Hz. I’m quite confident I won’t need to use a conjugate network if I cross at 2Khz.

Fig 3 – Spectrogram of 18Sound XT1086 with DFM2535

The Wavelet in Fig 3 is the first indication of the performance of this XT1086 horn. Note the absence of reflections as the sound wave transverse from 1.5kHz ~ 20kHz.

Fig 4 – Waterfall of 18Sound XT1086 with DFM2535

The Waterfall plot in Fig 4 supports the Wavelet in Fig 3. There are no destructive artifacts in the working range of the horn.

Fig 5 – ToneBurst Energy Storage of 18Sound XT1086 with DFM2535

I thought the The ToneBurst Energy Storage (TES) of the EV HT94 with the PRV D280Ti was incredible. This XT1086 with the DFM2535 (Fig 5) is simply amazing. I’ve never seen anything so “clean” in a horn before. 

Fig 6 –  Harmonic Distortion of 18Sound XT1086 with DFM2535

The Total Harmonic Distortion is slightly high at 1.25%. This is the summation of all harmonics from 2nd to 9th. The 2nd Harmonic recorded at 0.447% whereas the 3rd is at a low of 0.164%.

Summary

The 18 Sound XT1086 is indeed an exceptional horn. What they said in their promotional literature is true, not BS. I don’t have the 18 Sound compression driver that was specially developed for this horn but I managed to find a good match in the Peerless DFM2535 that showcases it’s unique properties.

This horn is on the expensive side but for users that demand top quality, it’s cheap compared to what we used to pay in the 80’s. The performance beats those vintage horns hands down. It’s that good.

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.