REL Acoustics No. 25 User manual

Operang Instrucons for the
N o . 2 5
S u b - B a s s
S y s t e m

2
Cauon Marking Explanaon
The lightning ash with arrowhead symbol within an equilateral triangle is intended to alert the
user to the presence of un-insulated dangerous voltage within the product’s enclosure that may
be of sucient magnitude to constute a risk of electric shock to persons.
The exclamaon point within an equilateral triangle is intended to alert the user to the presence
of important operang and maintenance (servicing) instrucons in the literature accompanying
the appliance.

4
3
1 Read all of these instrucons.
2 Save these instrucons for future use.
3 Heed all warnings.
4 Follow all instrucons.
5 Do not use this apparatus near water.
6 Clean only with automove polish and micro ber cloth.
7 Install in accordance with the manufacturer’s instrucons.
8 Do not install near any heat sources such as radiators, heat registers, stoves or other apparatus (including
ampliers) that produce heat.
9 Do not defeat the safety purpose of the grounding-type plug. A grounding type plug has two blades and
a third grounding prong. The third prong is provided for your safety. If the provided plug does not t
into your outlet, consult and electrician for replacement of the obsolete outlet.
10 Protect the power cord from being walked on or pinched parcularly at plugs, convenience receptacles,
and the point where they exit from the apparatus.
11 Only use aachments/accessories specied by the manufacturer.
12 Use only with a cart, stand, tripod, bracket, or table specied by the manufacturer, or sold with the
apparatus. When a cart is used, use cauon when moving the cart/apparatus combinaon to avoid
injury from p-over.
13 Unplug this apparatus during lightning storms or when unused for long periods of me.
14 Refer all servicing to qualied service personnel. Servicing is required when the apparatus has been
damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects
have fallen into the apparatus, the apparatus has been exposed to rail or moisture, does not operate
normally, or has been dropped.
Cauon: Any changes or modicaons not expressly approved by the party responsible for compliance
could void the user’s authority to operate this equipment.
Important Safety Instrucons

4
Warning
To reduce the risk of re or electric shock, do not expose this apparatus to rain or moisture.
The apparatus shall not be exposed to dripping or splashing and no objects lled with liquids, such as vases,
shall be placed on apparatus.
The mains plus is used as disconnect device. The mains plug of the apparatus should not be obstructed OR
should be easily accessed during intended use. To be completely disconnected from the power input, the
mains plug of the apparatus shall me disconnected from the mains.
An appliance with a protecve earth terminal should be connected to a mains outlet with a protecve
earth connecon.
Design Safety
This apparatus is supplied with a detachable mains cord. For 240V operaon a 3.15/S/2, 5A/S/3, 5A/S/5
fuse is ed in the socket, for 120V operaon a 6.3A/S/2, 9A/S/3, 9A/S/5 fuse is ed. Should the fuse
need to be replaced use a similar rated fuse approved to ASTA or BSI 362 standards. Do not use without
the fuse cover in place. Replacement fuse covers are available from your distributor.

5
Aenon Explicaon Marquage
L’éclair avec le symbole de pointe de èche dans un triangle équilatéral est desné à alerter
l’ ulisateur de la présence de non isolée tension dangereuse à l’intérieur de l’enceinte du
produit qui peut être d’une ampleur susante pour constuer un risque d’électrocuon pour
les personnes.
Le point d’exclamaon dans un triangle équilatéral est desné à alerter l’ulisateur de la
présence d’instrucons dans la documentaon accompagnant l’appareil exploitaon et de
maintenance (entreen).

6
1 Lisez aenvement ces instrucons.
2 Conservez ces instrucons.
3 Respectez tous les averssements.
4 Suivez toutes les instrucons.
5 Ne pas uliser cet appareil près de l’eau.
6 Neoyez seulement avec du vernis automobile et ssu microbre.
7 Installer conformément aux instrucons du fabricant.
8 Ne pas installer près de sources de chaleur telles que des radiateurs, registres de chaleur, poêles ou
autres appareils (y compris les amplicateurs) qui produisent de la chaleur.
9 Ne pas contourner le disposif de sécurité de la prise de terre. Une che de terre a deux lames et une
troisième broche de mise à la terre. La troisième broche est fournie pour votre sécurité. Si la che fournie
ne rentre pas dans votre prise, consultez un électricien pour le remplacement de la prise obsolète.
10 Protégez le cordon d’alimentaon ne soit piéné ou pincé, en parculier au niveau des ches, des prises
de courant, et le point de sore de l’appareil.
11 Ulisez uniquement des xaons/accessoires spéciés par le fabricant.
12 Ulisez seulement avec un chariot, stand, trépied, support ou table spécié par le fabricant, ou vendu
avec l’appareil. Lorsque vous ulisez un chariot, soyez prudent lorsque vous déplacez l’ensemble
chariot/appareil pour éviter les blessures en cas de chute.
13 Débranchez cet appareil pendant un orage ou lorsqu’il est inulisé storsm pour de longues périodes de temps.
14 Conez toute réparaon à un personnel qualié. Une réparaon est nécessaire lorsque l’appareil a été
endommagé de quelque façon que ce cordon d’alimentaon ou la che est endommagé, du liquide a
été renversé ou des objets sont tombés dans l’appareil, l’appareil a été exposé à rail ou à l’humidité, ne
fonconne pas normalement, ou a été échappé.
Aenon: Tout changement ou modicaon non expressément approuvés par la pare responsable de la
conformité pourraient annuler l’autorité de l’ulisateur à uliser cet équipement.
Informaons Importantes Relaves a la Securite

7
Averssement
Cet arcle est lourd. Pour éviter tout risque de blessure, prendre soin lors de la manipulaon.
L’ appareil ne doit pas être exposé à des éclaboussures et aucun objet rempli de liquide, comme des vases,
ne doit être placé sur l’appareil.
Les conduites Plus est ulisé comme disposif de déconnexion. La che de l’appareil ne doit pas être
obstruée OU doit être facilement accessible pendant l’ulisaon. Pour être complètement déconnecté de
l’alimentaon électrique, le cordon d’alimentaon de l’appareil doit me débranché.
Un appareil avec une borne de terre doit être branché sur une prise de courant en étant relié à la terre.
Sécurité Design
Cet appareil est livré avec un cordon amovible cordon. Pour le fonconnement d’un fusible de 220V
3.15/S/2, 5A/S/3, 5A/S/5 est montée dans la douille, pour le fonconnement de 120V un fusible de
6.3A/S/2, 9A/S/3, 9A/S/5 est monté. Si le fusible doit être remplacé ulisaon un fusible similaire
approuvé pour ASTA ou BSI normes 362. Ne pas uliser sans le couvercle de fusible en place. Les
couvercles de rechange sont disponibles auprès de votre distributeur
FCC STATEMENT
This device complies with Part 15 of the FCC Rules. Operaon is subject to the following two condions:
(1) This device may not cause harmful interference, and
(2) This device must accept any interference received, including interference that may cause
undesired operaon.
NOTE: This equipment has been tested and found to comply with the limits for a Class B digital Device, pursuant to Part 15 of the
FCC Rules. These limits are designed to provide reasonable protecon against harmful interference in a residenal installaon.
This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the
instrucons, may cause harmful interference to radio communicaons. However, there is no guarantee that the interference will
not occur in a parcular installaon. If this equipment does cause harmful interference to radio or television recepon, which can
be determined by turning the equipment o and on, the user is encouraged to try and correct the interference by one or more of the
following measures:
Reorient or relocate the receiving antenna.
Increase the separaon between the equipment and receiver.
Connect the equipment into an outlet on a circuit dierent from that to which the receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.

8
Thank you for purchasing your new REL No.25, this unit is produced with great pride and operates as the
standard bearer summarizing a journey that has taken REL 25 years to achieve. As the commemorave
unit marking 25 successful years, the No.25 takes all the best technologies developed over the past quarter
century and adds a few important design improvements to create a new standard to carry us on to the
next 25 years.
Scale and Power: There is, as the saying goes, no replacement for displacement. Our development of a
super, light, fast 15 inch driver was no easy task and it took quite some me to nd a manufacturer capable
of building to our standard. Anyone can build a big, loud 15 inch driver; the hard part lies in keeping it
lightweight and yet s enough to hold up to the rigors our customers regularly put their units through.
160 square inches, capable of moving 2” fore and a (total stroke of 100mm or approx. 4”) of specially
prepared, woven carbon bre allows for massive wave-fronts to be developed. And yet, what will surprise
serious students of the infra bass art is the speed, texture and liquidity this driver expresses. But for the
eortless extension and power it produces in spades, it sounds even faster than a great 10” driver.
Un-corrupble Power: REL required serious power to unlock the performance potenal of the No.25 driver
and so we turned to our newest amplier design, a specially developed Class D amplier that produces a
connuous 1,000 was and can deliver yet higher output on peaks. Naturally, this amplier has already
proven itself to be rugged and reliable in the eld so feel comfortable trusng our commemorave design
to this beast of an amp.
It All Begins Up Front: To this bulletproof amplier and driver combinaon, we applied the legendary lter
set we developed for the No.25; these are the fastest lters we have ever measured at just 4 ms and a
crossover that begins as low as 20Hz. Beyond simply technical bragging rights, they are the most natural
sounding lters we have ever experienced.
Taming the Room: We don’t believe in room correcon, too oen this is the bason of those who would
rather not get it right in room design nor set-up, but believe they can “correct” it all with an enormously
complicated lter called room correcon. There is no free lunch in high end audio and the price that must
be paid is loss of impulse response (speed and dynamics)—not to menon highly variable results using
these computerized aempts to x all.
We have chosen to include not 1 but 2 parametric equalizers using specially developed REL-fast lters. Each
lter permits boost or cut of 6 dB, a perceived doubling or halving of output in a narrow frequency range.
REL Parity™ allows the advanced set-up arst the ability to idenfy room modes, both peaks and dips, and
Dear No.25 Owner

9
smooth out the overall in-room response. While it takes a lile pracce (and generally a gentle hand on the
controls is highly recommended) the results are highly grafying. Use it to gently ll in an area that requires
more output and then gently cut bass in the upper range that is too exuberant.
A Beauful Body: The curvaceous cabinet is designed to push further the experience of minimizing internal
cabinet resonances by creang a curvilinear cabinet that does not permit any single frequency from building
up a dominant mode. It is this s, fully-braced like a ne musical instrument design that allows the full
palee of tonal colors to emerge from No.25 along with the prodigious dynamics for which it is quickly
becoming known. Even the Bass String™ grille has been designed with an eye to beauty and airow, allowing
enormous displacement of air to pass through without restricon, where a convenonal grille would muddy
the sound.
In sum, the No.25 puts into pracce all the many lessons – and more – learnt by REL along its 25 year
journey-to-date. We look forward to enjoying the next 25 with you, many thanks for allowing us to serve you.
Sincerely,
John Hunter

Remote Control
1 Crossover: Used to adjust crossover frequency. Variable between 20-90Hz.
2 .1/LFE Level: Used to adjust output level when using .1/LFE input from a surround-sound processor.
Also used to adjust Parametric EQ frequency.
3 High/Low Level: Volume control for High/Low Input. Use to adjust output when using either High Level
or Low Level input. Also used to a adjust Parametric EQ level.
4 Filter: Used to select lter operaon.
5 Phase: Used to set phase 0-180 degrees.
6 Security: Used to lock remote sengs. To extend baery life of the remote, always leave the toggle
switch in the locked posion when not in use.
10
REL No.25 Remote Control and Rear Panel Legends
1
23
4
5
6

11
REL No.25 Rear Panel Connecon Legend
1 .1/LFE RCA Input: Used to connect to the .1/LFE output of a surround-sound processor.
2 .1/LFE RCA Output: Used to connect or “daisy chain” another REL No.25 in tandem.
3 Le & Right Channel Low-Level RCA Input: Used to connect low-level signals to the sub-bass system from
the output of a preamplier, integrated amplier or receiver. (For home cinema use, use .1/LFE input).
4 High Level Input (Neutrik Speakon): Used to connect to the main front amplier speaker terminals.
5 High Level Output (Neutrik Speakon): Used to connect or “daisy chain” another REL No.25 in tandem.
6 .1/LFE Balanced Input: Balanced (XLR connector) version of .1/LFE Input. For use only with fully
balanced cables.
7 .1/LFE Balanced Output: Balanced (XLR connector) version of .1/LFE Output. For use only with fully
balanced cables.
8 Ambient Trig: Used to turn ambient light on the underside of the sub on and o by a 12VDC trigger
9 Ambient Control: Used to pre-set the amount of ambient light from the underside of the sub.
10 Parametric Filter: Used to engage parametric lter into the signal path.
11 Antenna Connector: Used with REL Longbow™ transmier.
12 Pair Pilot Light: Indicates if unit has been paired with REL Longbow™ transmier.
13 Pair Switch: Used to iniate pair sequence with REL Longbow™ transmier.
14 Wireless enable switch:Used to turn on wireless receiver when connected to REL Longbow(TM)
wireless transmier.
15 Standby/Always On Switch: Used to enable standby mode.
16 Power Pilot Light: Power On/O indicator.
17 Power On/O Switch: Use to turn unit on or o.
18 IEC Mains Socket: Fused mains (AC) input socket that accepts detachable power cord.

12
8 9
10
11
12
13
1 2 3
4 5 6 7
14
15 16
17
18

13
High-Level Input
Connecons should be made to the same binding post on main amplier as the main speakers. Red to amplier main
right speaker red terminal, yellow to amplier main le speaker red terminal and black to amplier main speaker
black terminal, right or le but not both. Plug the Neutrik® Speakon® plug into the HI LEVEL Speakon® socket.
.1 Input
This requires a RCA to RCA or XLR to XLR cable and is a dedicated true .1 channel. This circuit therefore
eliminates the normal Natural RollO™ Crossover and passes the .1 low-level signal through with only the
required 120Hz fourth-order lter.
Low-Level Input
The RCA inputs allow for convenonal connecon from a preamplier and should be used in the rare event
that a high-level connecon proves incompable. Plug one end of the RCA to RCA cables into the LOW
LEVEL INPUT jacks of the REL and the other end into the le and right channel output of your preamplier.
Phase Switch
Used to set phase. Phase Switch on remote control is momentary. Refer to display for 0 or 180 degree status.
Phase selecon aects High Level, Low Level and .1/LFE inputs.
PHASE SELECTION AFFECTS BOTH HIGH AND LOW LEVEL INPUTS
Crossover is always engaged for high and low level inputs. The .1/LFE signal does not pass through the
crossover circuit.
Filter
The No.25 can employ a two band parametric EQ lter. With the top Filter switch in the center locaon the
remote acts in normal operaon. With the switch in the far le posion, the .1/Level control on the remote
changes the frequency of EQ lter 1, and the Hi/Lo Level control on the remote changes the level of EQ lter 1.
With the switch in the far right posion, the .1/Level control on the remote changes the frequency of EQ
Connecvity and Funconality

14
lter 2, and the Hi/Lo Level control on the remote changes the level of EQ lter 2. Each lter has a frequency
range from 20Hz to 90Hz. The level set of each lter is +/- 6 dB in 1/3 dB increments.
LED Display
An LED display is located on the upper right front of No.25. All funcons that are user adjustable via the
remote control can be seen here. The display reverts to o a few seconds aer adjustment. The top three
characters indicate the parameter being controlled by the remote and the boom two numbers indicate
the value of the parameter controlled.
Parameter Display
High/Low Level HL
.1 Level .1
Crossover Frequency CO
Phase PH
Parametric EQ1 E1
Parametric EQ2 E2
Ambient Control
No.25 has an array of ambient lights on each side, outboard of the feet. The intensity of these lights can
be controlled with the 4 posion AMBITET CONTROL switch. Starng with the switch in the far counter
clockwise posion, the lights are o, as the switch in moved to the next three posions, the intensity will
increase. The ambient lights can be triggered o for theater viewing with a common 12VDC trigger. 0V at
AMBIENT TRIG keeps the lights ON, +12V at this trigger input turns them OFF.
Remote Control Baery Installaon
No.25’s Remote Control Unit requires two AAA baeries. These are not installed but are supplied. To install
or replace baeries in the Remote Control Unit, rst remove the boom aluminum cover by using the
supplied 2.5mm Hex key to loosen the two visible screws. With the boom cover removed, you will see a
baery holder, which will accept two AAA baeries. Follow the images on the holder for proper orientaon
of the baeries. Aer installing the baeries, test the unit by seng the SECURITY switch to UNLOCK and
turning one of the knobs. If the baeries are installed properly, you will see one of the red LEDs on the
remote control’s front panel illuminate. Replace the boom cover and ghten the two screws using the
supplied Hex key. Baery life can be extended if the SECURITY toggle switch is le in the LOCK posion
when the Remote Control is not in use.

15
Always switch o your system before disconnecng any wires.
To increase the versality of connecng up, the No.25 models have three separate inputs. A high-level input
socket, a .1/LFE input consisng of both RCA and XLR connectors, and a low-level input that includes two
RCA sockets for stereo input. This is to facilitate use with both two-channel stereo systems and AV surround
sound systems.
The high-level, unbalanced, dual-channel (stereo) input is via a Neutrik® Speakon® connector is designed to
accept the stereo (two-channel) signals from the speaker terminals of your receiver, integrated amplier or
basic amplier. This has the advantage of ensuring that your subwoofer receives exactly the same signal as
the main speakers, which means that the character of the bass from the main system is carried forward into
the Sub-Bass System.
This is a very important point and together with REL’s Natural RollO™ circuitry, ensures far superior system
integraon of the Sub-Bass System with the main system.
To engage the Neutrik® Speakon® plug, insert fully into socket and rotate clockwise unl locked.
To remove the Neutrik® Speako n® plug , grip body of plug , place thumb on chro me lever, move lever b ac kward s,
rotate plug anclockwise quarter turn and withdraw.
There are two RCA sockets for low-level connecon to the output of a stereo preamplier or receiver. Another
single RCA socket connects to the .1/LFE output of a home cinema processor.
HIGH LEVEL and .1/LFE inputs can be used simultaneously. The benets are two-fold when used with a
home cinema processor. The low-level input reproduces the .1/LFE channel and the high-level connecon
underpins the main front speakers. The main front speakers should be set to the ‘large’ opon on the
processor. See “theatre Applicaons” for more informaon.
Connecng Up

REL products are not tradional subwoofers, but true Sub-Bass Systems. A REL is designed to augment the
performance of “full range” speaker systems in order to provide, in certain cases, linear response below 15Hz.
Therefore, for the moment, please set aside everything you’ve been taught about subwoofers and how they
are integrated into a stereo or home cinema system. REL Sub-Bass Systems set-up and posioning diers
from convenonal subwoofers. A REL will take advantage of physics and room acouscs to provide deep
pressurizaon as no tradional subwoofer can. It is important that you bring to the set-up process a willingness
to do things a lile dierently in order to obtain these superior results. The end result of your labors will be
an uerly seamless integraon of true deep bass to a sound system, regardless of the main speakers’ low
bass capability.
Basic set-up should take no more than ten to een minutes to accomplish once connected.
Two Things Before You Begin
1 It is helpful to know that you will almost always connect the REL to the input on the rear panel labeled
“HIGH-LEVEL INPUT.” This connecon is made using the supplied 32’ 10” (10 meters) cable, the bare
leads of which connect to the speaker output terminals of the power amplier. The easy and foolproof
connecon at the REL is done with a Neutrik® Speakon® connector. The purpose of connecng to the
speaker output terminals is one of the unique secrets of REL’s success. By connecng to the High Level
input on the REL from the amplier, you build forward the sonic signature of your main system, including
the tonal balance and ming cues of the enre electronics chain. In this way, the REL is fed the exact
signal that is fed to the main speakers.
2 When possible, the REL should be placed in one of the corners behind the speakers. Remember, we are
dealing with true LOW bass pressurizaon with RELs. Low bass pressurizaon below 40Hz is best derived
from corner placement, where the most linear and ecient low bass can be produced because the
subwoofer is able to take advantage of the tangenal (corner-to-corner) axis which is typically the
longest axis in a room.
Connecng and Seng Up
High-level connecon, using the enclosed cable with the Neutrik® Speakon® connector, is always the rst
choice. This connecon can be made without aecng the performance of the amplier because the REL’s
amplier input impedance is 150,000 ohms, in eect producing NO addional load on the rest of your system.
16
REL Set-Up Made Simple

17
• The standard high-level hook up procedure is: aach the red wire to the amplier’s right posive speaker
output terminal; aach the yellow wire to the amplier’s le posive speaker output terminal; aach
the black wire to whichever of the amplier’s ground output terminals is convenient; plug the Speakon®
connector into the Sub-Bass System’s high-level input.
• For dierenal (i.e. fully balanced) ampliers using one REL, simply use the standard connecng scheme
with the excepon of NOT connecng the black wire to a negave speaker terminal. Instead, it should
rst be allowed to “oat” or hang down without connecon to ANY terminal. Should hum occur using
this method, please try connecng to an unused RCA connector on the rear of a preamp or amplier.
Please contact your dealer should there be any quesons concerning this or any other hookup procedure.
NOTE: No.25 models are equipped with internal circuitry to allow connecon to many Class-D (digital)
ampliers. Warning: Do NOT connect the Black wire to the main Class D power amplier’s speaker ground
terminal. Some Class D ampliers produce posive voltage at the amplier’s speaker ground terminal (black)
Standard High-level
Dierenal (i.e. Fully Balanced)

18
and connecng the REL’s ground will produce an undesirable shorng to ground. If connecng to a Class-D
amplier, follow the above connecon procedure for dierenal ampliers.
• When connecng RELs to Mono Bloc ampliers (2) RELs, one for each amplier, must be used. Connect
the black wire of each REL to the negave speaker terminal of the corresponding amplier channel; twist
together the red and yellow wires of each REL separately and connect each pair to the posive speaker
terminal of the corresponding amplier channel. In some instances, this will result in exceponally high
gain (output) from the RELs. If it seems simply too high in gain, please remove either the red or yellow
wire from the twisted pair. This will reduce output by half and restore a natural dynamic.
If the amplier is of balanced dierenal design, please follow the instrucons in the secon above labeled
Dierenal Connecon.
Mono Bloc
Mono Bloc Dierenal

19
• If connecng a single REL as a dedicated centre channel sub, an insider p is to consider connecng to
the rear of the speaker, rather than roung the REL High Level enable all the way back to the amplier.
Connect the black wire of the REL to the negave centre channel speaker terminal; twist together the
red and yellow wires and connect this paired cable (red/yellow paired together) to the posive centre
channel speaker terminal.
• If connecng a REL as a dedicated rear channel sub, connect the black wire of the REL to either the le
rear or right rear negave speaker terminal; connect the yellow wire to the le rear posive speaker
terminal; connect the red wire to the right rear posive speaker terminal. If the amplier is of balanced
dierenal design, please follow the instrucons in the secon above labeled Dierenal Connecon.
Low-level connecon (via RCA connectors) is always an opon if high-level connecon is not possible. When
connecng to the low-level inputs in a system in which high-level connecon is not possible, such as if using
internally-amplied speakers, connect le and right RCA cables between the LOW LEVEL INPUT jacks of the
REL and the le and right channel outputs of your preamplier.
Dedicated Centre Channel
Dedicated Rear Channel