The REL T/9x Red Subwoofer: Beyond the Black Box

Most subwoofers are black boxes. This is almost always true for inexpensive subs like the $300 Monoprice SW-15, but it’s often true even when prices get very high, as with the $7K RTJ Audio 18Sub. These monochrome monoliths are fine for dedicated home theaters, but may be less welcome in the living room, where style must compete with sound quality to win the approval of non-audiophile members of the household. I’m always on the lookout for subs that go “beyond the black box,” and I’ll be featuring a few of them here at Audioholics, starting with the new REL T/9x Red ($1,650). This isn’t sponsored content — just a quick look at products that have caught my eye.

The regular T/9x ($1,500) comes in black or white, and is one of REL’s most popular models because it’s a great all-rounder. It performs admirably for both music and theater in typical living-room systems that aim for a reasonable compromise between style and substance. It doesn’t deliver single-digit bass, but I know from experience that it sounds superb, especially in pairs. It’s the flagship of REL’s Serie T/x range, which is the brand’s entry-level offering for music-focused performance (as opposed to REL’s Serie HT, which focuses on theater performance). Despite its flagship status within Serie T/x, the T/9x is not a large sub. Its 10-inch forward-firing driver and 10-inch down-firing passive radiator are built into a beautifully-made cabinet measuring 13.4 inches tall, 14.5 inches wide, and 15.5 inches deep. This compact size is one of the reasons why it’s so popular. Now this same form-factor is available in a fetching Rosso Corsa Red paint. It’s the same paint that adorns Italian sports cars from brands like Ferrari, Maserati, and Alfa Romeo. REL’s high-gloss, hand-polished finishes are really exquisite, so I’d expect the T/9x Red to look even better in person than it does in photos. There are seven coats of Rosso Corsa paint on the T/9x Red.

REL’s owner and lead designer, John Hunter, says that this particular paint costs an astonishing $600 per gallon! That ridiculous figure helps to explain the $150 price increase over the standard T/9x, but luckily your money isn’t being spent on paint alone. The T/9x Red also includes some upgrades that affect sound quality. The driver has been upgraded over the standard version, resulting in a 25% price increase over the original driver. The standard T/9x driver is made from a composite of air-dried white paper, stiffened by an aluminum center cap. In the T/9x Red, the aluminum is replaced by a 6-inch, pure carbon fiber center cap. The center cap is responsible for holding the structural integrity of the cone intact when it’s under pressure. The louder the sub plays, the more important the center cap becomes. The stiffer center cap reportedly results in better bass articulation. The use of carbon fiber also reduces the weight of the cone’s moving surface by 10 grams and increases the driver’s overall sensitivity by 1.2 dB. The result, according to REL, is a driver that’s quicker off the line, and more dynamic than the standard version. The improved driver allowed REL’s engineers to retune the driver’s suspension, making it a bit stiffer and “more like a sports car,” according to Hunter. “It goes a little bit deeper and it hits a little harder,” he said in a video explaining the new sub. “(The T/9x Red) is very reactive, and it stops and starts even quicker than the (standard) T/9x.”

The driver is powered by a 300-watt Class AB amplifier. REL says that this time-tested Mosfet design has integrated heat sinks and offers bulletproof performance and dependability. Although the amp has been tweaked over the years, it is essentially the same design that has been used since the first Series T flagship sub was launched in 2007. REL says that nearly 90,000 of these amps are in circulation and still used regularly. 

Note: The plate amps used on powered subwoofers are notorious for being the least reliable electronics in a typical audio system. They’re almost always the first thing to go bust — I’ve had to replace three of them over the years. 

The T/9x Red is covered by a 3-year warranty, but these amps should last far longer than that, even with daily use. Around back, you’ll find a high-level input coupled to REL’s proprietary analog input filter with a claimed 8ms of delay which is a considerable amount that you may need to compensate for with placement for proper alignment with your mains if you aren't using bass management and delay compensation. REL recommends running your speakers full range, and supplementing the bass by attaching your amp’s output to the subwoofer’s high-level input. (A long cable with a Neutrik Speakon connector is included.) 

At Audioholics, we tend to recommend a different approach to subwoofer integration, involving the application of a high-pass filter to the main speakers. You’d then run a line-level cable to the sub(s). Luckily, the T/9x Red also accommodates this method via a low-level (RCA) input. This is the better connection for proper integration with a bass managed home theater system and how we recommend for most systems. And for those who want to use the sub for both 2-channel listening and home theater, there’s a separate .1/LFE input with its own level control. You can even use the high-level input and the .1/LFE input at the same time. If you need to go wireless, the optional “Arrow” zero compression wireless system ($220) delivers the high-level signal along with the .1/LFE signal simultaneously, without the “thin, dried out sound most wireless systems deliver,” according to REL. This is achieved by eliminating the (often very slow) delivery methods provided by off-the-shelf systems based on Wi-Fi. REL uses LSI (large scale integrated circuit chips) technology to lower the cost of the system while maintaining high performance. The receiver docks and locks directly to the rear of the sub.

As I said from the start, the fact that this sub is not just another black box will certainly play a part in making it a popular choice, particularly among those audiophiles who lean toward contemporary design. I don’t know how well it would blend in with the decor in my girlfriend’s 1908 Craftsman-style home in Seattle, but I’d be willing to find out. In addition to the racing red paint, the T/9x features other style flourishes, including a chrome and carbon-fiber top badge, and metal feet that undergo a three-day chroming process. Copper, nickel, and chrome are meticulously layered, with each coat being given a day to set before adding the next. Many readers might balk at this level of attention to detail, and it’s true that these aesthetic choices don’t affect performance. But for others, looks matter, even in audio. The REL T/9X is available for purchase through our channel partner Audio Advice.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.