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Rel Acoustics No.25 Subwoofer Listening Demo Results

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Summary

  • Product Name: No.25 Subwoofer
  • Manufacturer: Rel Acoustics
  • Review Date: June 26, 2017 19:00
  • MSRP: $7,500
  • First Impression: Pretty Cool
  • Buy Now

  • Type: Closed box, front firing woofer
  • Drive Unit: 15 in., 380mm long throw, carbon fibre cone with inverted carbon fibre centre cap
  • Lower Frequency Response in Room: -6dB at 15Hz
  • Input Connectors: High Level Neutrik Speakon, Low Level stereo RCA, LFE RCA, LFE XLR
  • Output Connectors: High Level Neutrik Speakon, LFE RCA, LFE XLR
  • Gain Control Range: 80 dB
  • Power Output: 1000 watts (RMS) Ultra High-Current Power Supply
  • Phase Switch: Yes, 0 or 180 degrees
  • Amplifier Type: NextGen3 Class D
  • Wireless Capability: Yes - REL Longbow™ transmitter [required]; sold separately
  • Protection System Fully Electronic with SET-SAFE: Yes
  • DC Fault: Yes
  • Output Short: Yes
  • Mains Input Voltage: 220-240 volts, 110-120 volts for certain markets Fuses 7 Amp semi delay 230 volts operation; 15 Amp semi delay 115 volts operation
  • DIMENSIONS: W x H x D, Inc. Feet 29 x 21.3 x 30 in., (736.5 x 540 x 762 mm)
  • Net Weight: 168 lbs. (78 kg)
  • Finish: Gloss Piano Black

Executive Overview

Long-time subwoofer manufacturer Rel Acoustics has decided to bring something special to the market in 2017no25.jpg. To commemorate their 25th year as a subwoofer manufacturer they’ve launched a new flagship in their ‘No.25.’ subwoofer. The No.25 is the new top dog in their Reference line, which is their highest-end product series. The No.25 is a sealed subwoofer using a 15” woofer, but to describe it as plainly as that is like saying the Bugatti Veyron is a car that uses four wheels. There is quite a bit more to the No.25 than base specs. Yes, it is a sealed 15”, but what a sealed 15”!

Design Overview

Let’s begin with the cabinet. This is a massive sealed 15” sub with an enclosure volume larger than some 18” subs on the market. It uses width and curvature to its advantage to not seem like a behemoth. It is a large sub, but it doesn’t look as large as it really is. However, this is not to say that it will go unnoticed in a living room, which given its size, would be impossible. In order to make such a large subwoofer aesthetically palatable, Rel has given it an exquisite shape and finish, a trait that Rel is known for. The No.25 uses a backward curving cabinet for a sleek and elegant appearance, and it does remind one of a high-end sports car. The paneling is a substantial 1.2” thick with bracing that Rel claims is like the spars in a ship’s hull. This likely comprises most of the No.25’s titanic 168 lb weight, but over-building is all a part of making the highest-end subwoofer that a high-end subwoofer manufacturer can make.

Another part of the equation of making a high-end subwoofer is the driver. Tsingle_setting.jpghe cone is made from a high-grade carbon fiber, which has a great combination of being both stiff and light-weight. The 15” cone is a healthy diameter size, but a large diameter woofer doesn’t necessarily guarantee that a lot of displacement is available. However, with a 4” peak-to-peak stroke, the No.25 can move a tremendous amount of air.

Having a lot of air displacement is nice, but the mark of a good subwoofer is how precisely it can move that air. Towards this end, John Hunter, owner of Rel, told me that their design team worked very hard at getting the internal geometry balanced. Rel subs use ultra tight gaps and precision aluminum formers so they have very little room for error. The attention to detail that Rel has for the No.25 is very exacting. One example is the lead-in wire and how to route it.  Hunter says,

There is exactly one company that can do lead in wire for a project of this caliber and it takes tremendous work to keep the wires attached because the acceleration forces on large transients can literally leave the wire behind.

remote.jpg      coneC.jpg

As with displacement vs precision of air movement, a good driver is essential, but it is nothing without power. On this Front, Rel has supplied the No.25 with a beefy 1,000 kW advanced class D amplifier that they have called a NextGen3 design. This amp is loaded with connectivity and control. For connectivity, the No.25 can accept high-level Neutrik Speakon, line-level stereo RCA inputs, LFE input of both RCA and XLR, and it also has a wireless adapter. Daisy-chaining subwoofers is made easy with the Speakon and LFE outputs. The No.25 has two parametric EQs that can be set at any frequency from 20 Hz to 90 Hz that can boost or cut the signal by 6 dB. A digital display in the front of the sub allows you to see the changes being made all with the use of  Rel’s remote control. The remote control is a luxury statement unto itself, with a carbon fiber face-plate and a stainless-steel body.

room_viewC.jpg 

Demo Results

The No.25 are made to be easily stacked for a ‘line-array’ of subwoofers, in case just one does not suffice the user’s craving for bass. I took aheroC.jpgn opportunity to hear a “six-pack” of No.25 subwoofers at Joseph Audio Video Solutions, Inc in Midlothian, IL recently (not to mistaken for the loudspeaker manufacturer Joseph Audio, by the way). The overall sound was stellar, which is what one might expect from high-end Dynaudio speakers run from top-of-the-line Mark Levinson electronics. But the subs stole the show. The bass was refined and precise yet almost physiologically-damaging in output capability. Joseph Hesse, the proprietor, walked me through some demo music including the popular demo piece for audiophile bass, Chris Jones’ “No Sanctuary” with its deep bass guitar and baritone chorus, and Yello’s “Planet Dada” with its pinpoint-sharp electronic bass line. Bass was felt as much as it was heard, and the physical sensation of each note was as distinct as its sound. Joseph also demo’d some movie content, and we viewed the bombastic finale of Cher’s 2010 musical “Burlesque”, that, on a system like that, proved to be sensory overload. The whole experience was a lot of fun.

Rel_badge.jpg      grille_angle.jpg

The Rel No.25’s are pricey subwoofers at $7,500 each, but if you want something that packs as much build quality and technology in a gleaming package like the No.25’s, it cannot be done inexpensively. Although, the high price of entry affords one the pride of ownership of such a finely-crafted device. Have you heard these subwoofers yet? If so, share your experiences in the related forum thread below.

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About the author:

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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Recent Forum Posts:

shadyJ posts on June 27, 2017 00:04
lovinthehd, post: 1194863, member: 61636
So you enjoyed testing it but wouldn't buy it? Still haven't read the article, something about Rel persuades me it isn't worth my time as I'd never consider them for product. So they still doing the funky two way connection?
I didn't test the Rel subs, I just listened to them for a little while. If I had the money and means for something like these, I would probably just commission the construction of a subwoofer to my own specifications, but I am far more interested in subwoofer technology than your average buyer. As for the connectivity, Rel's preferred connectivity is Neutrick Speakon high-level inputs, but the No.25 can also accommodate RCA, XLR, and wireless connections.

Anyway, value is subjective. You can get three of these for the price of a Wilson Watchdog or four of these for a Magico Q sub. But until I win the lottery, I am not really concerned with any of them.
lovinthehd posts on June 26, 2017 23:43
shadyJ, post: 1194861, member: 20472
The Paradigm Persona sub drivers likely have relatively little xmax compared to the No.25. That extra cone surface area might not be able to make up the difference. And the Persona drivers are certainly going to have a higher Fs. Yeah, the No.25 is expensive but it is dead sexy. I wouldn't mind having a pair. Or a pair of stacks of three.

As for value, this is a luxury, high ticket item. It operates on a different market plane than high value item like Hsu or SVS. It's like Rolex; sure, you can get a more accurate timepiece with a $50 Casio, but no one is buying Rolex watches so they can know what time it is.

So you enjoyed testing it but wouldn't buy it? Still haven't read the article, something about Rel persuades me it isn't worth my time as I'd never consider them for product. So they still doing the funky two way connection?
shadyJ posts on June 26, 2017 23:40
The Paradigm Persona sub drivers likely have relatively little xmax compared to the No.25. That extra cone surface area might not be able to make up the difference. And the Persona drivers are certainly going to have a higher Fs. Yeah, the No.25 is expensive but it is dead sexy. I wouldn't mind having a pair. Or a pair of stacks of three.

As for value, this is a luxury, high ticket item. It operates on a different market plane than high value item like Hsu or SVS. It's like Rolex; sure, you can get a more accurate timepiece with a $50 Casio, but no one is buying Rolex watches so they can know what time it is.
rojo posts on June 26, 2017 22:08
KEW, post: 1194854, member: 41838
Yep, my sensibilities top out somewhere right around Funk Audio (that is not what I have, but what I think I'd want)!

Yeah, really. For that kind of dough I'd prefer a pair of these subs with their 18Hz - 40kHz range.

I'm struggling to understand the target market for this sub. I get that pretty comes at a premium, but how is it worth $5500 more than the SVS SB16 Ultra? And padding the price for dealer markup is likewise allowable, but Paradigm also has a furniture-grade 15" offering for $3500 less. If the additional output of Rel's larger enclosure is preferred, then Paradigm's hexa-driver Persona can still be had for $1000 less, pushing 700 more watts and 40% more driver surface area. What niche is Rel filling?
lovinthehd posts on June 26, 2017 22:04
Then there's the goofy hookup method for Rel for audiophiles….altho I haven't read the article yet, just assuming they're still on that horse.
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