NHT Speaker S 20 User Manual

professional  
S-20  
Powered Subwoofer  
Owner’s Manual  
NHT, Inc.  
6400 Goodyear Road  
Benicia, CA 94510  
www.nhthifi.com  
 
INTRODUCTION  
Thank you for your purchase, and congratulations on  
your selection of the NHT Pro S-20 powered subwoofer.  
The S-20 will add dynamic bass response to any pair of  
smaller, powered monitors, or can be used to reproduce  
the .1 LFE channel for surround mixing. The S-20 was  
designed to mate seamlessly with the NHT Pro M-00 and  
M-20 monitor systems, and offers tremendous flexibility:  
- Use multiple S-20’s to improve bass output if desired.  
- Add an optional footswitch and you take the S-20 in and  
out of the audio chain on the fly.  
- Use as a ported or sealed design as NHT includes a  
port plug with every S-20.  
Investing some time learning about the S-20's features  
and capabilities will reward you with the best possible  
performance. Now would also be an excellent time to fill  
out and send in your warranty registration card; or regis-  
This action will automatically extend both the parts and  
labor warranty for an additional two years, for a total of  
three years! If at any time, you require assistance, call  
our customer service hotline at (800)-NHT-9993 (648-  
9993).  
increase power handling. Setting the Subwoofer Bypass  
switch to BYPASS eliminates this circuit and sends all  
frequencies in the signal to the satellite monitors.  
4) Phase Switch: This switch sets the polarity of the  
subwoofer at either the 0° position (normal phase) or the  
180° position (reverse phase) to achieve the smoothest  
possible bass response in your system.  
USER CONTROLS / CONNECTORS  
1) Sub Level Control:  
The subwoofer level control matches the S-20 output  
level to the satellite monitors. This control differs from  
most as it doesn't turn the woofer all the way off, but  
offers a 18dB range of adjustment. Fully clockwise, out-  
put is maximum (0 dB or unity). In the counter clockwise  
position, the sub output is attenuated by 18dB.  
This phase-reversing option is important because when  
bass frequencies come from both the subwoofer and the  
main speakers, peaks and dips in the frequency  
response can occur at the listening position. In these  
cases, reversing the subwoofer polarity can improve  
blending and balance.  
2) Input Sensitivity Control:  
This control affects the level of all signals that go through  
the S-20, both the subwoofer and satellite signals. Use  
the +4dB position when you have a normal or high signal  
level (most cases). Use the -10dB position when you  
have a very low signal level (rarely). When setting up the  
system, start with the control in the +4dB position. If the  
system output is adequate, when your signal source has  
it's volume or gain control at the maximum position, leave  
the control in that position. If the system does not have  
enough output, move the control to the -10dB position.  
Following this procedure will give you the minimum sys-  
tem noise level.  
To properly set the Subwoofer Phase:  
• Play familiar music, reversing polarity settings. Listen  
from your usual position.  
• Avoid evaluating while standing above the subwoofer or  
amplifier; sound at the listening position will be signifi-  
cantly different.  
• The correct setting is the one in which the bass is the  
loudest at the listening position.  
3) High Pass (HP) Frequency Switch:  
5) Low Pass (LP) Frequency Control:  
The High Pass Frequency switch determines the lowest  
frequency passed on to the satellite monitors. There are  
two settings: 80Hz and 110Hz. Selecting the proper  
switch position (see the Initial Control Settings section  
on Pg. 4) will help blend the overall system response and  
This control allows fine adjustment of the subwoofer  
crossover point to match the point where the satellites  
roll off at the low end of their response. This detented low  
pass control has a range of 80Hz -110Hz.  
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6) Input Section:  
The S-20 offers three stereo input options: two types of  
balanced inputs (TRS and XLR) and unbalanced RCA.  
The two balanced inputs are wired in parallel. Note:  
Standard 1/4” connectors may be used in place of the  
TRS type if the source equipment employs unbalanced  
outputs, but this method may induce unwanted noise.  
PLEASE NOTE: These different connector options  
have been provided for your convenience. Use only  
one connection for the left channel and only one con-  
nection for the right channel or damage may result to  
your subwoofer.  
7) Output Section:  
The output connectors to the satellite monitors are bal-  
anced, TRS type. Two 12' cables are included to connect  
the S-20 left and right outputs to the satellite monitors.  
PLEASE NOTE: If you are using your S-20 subwoofer  
with a pair of NHT M-00’s, set the sensitivity switch  
on the M-00’s to +4.  
probably sound best. In a larger room or where the sub-  
woofer is farther from the walls or corners, bass reflex  
mode will work best.  
8) Subwoofer Bypass:  
When installing the port plug, put it in the port until it  
stops, and then push it in another 1/4". It is not necessary  
to use a lot of force. As long as there is no audible air  
noise coming from the port, the plug is in far enough.  
This feature, helpful when monitoring, allows you to turn  
the S-20 “ON” or ”OFF” on the fly. Any standard “latching”  
or two-position foot switch that has a 1/4”plug will control  
this function. A press of the foot switch will place the S-  
20 and its High Pass filter into BYPASS mode and  
remove them from the signal chain. A second press of  
the foot switch, causes the S-20 to resume operation.  
CONNECTING THE S-20 SUBWOOFER:  
Using the S-20 as a .1 or LFE stand-alone device:  
Connect either an RCA, XLR or TRS from your designat-  
ed LFE channel or buss output assignment to either the  
left or right input on the S-20 “INPUT SECTION”. If more  
subwoofer sensitivity is required, use a “Y” adaptor and  
connect to both left and right inputs. Turn the low pass  
control to it’s maximum position. Be sure to utilize sur-  
round test tone signals to properly balance the woofer  
level with the other monitor channels. Please read  
through the Subwoofer Placement and User Controls  
sections before you begin.  
9) Power Section:  
The main power ON and OFF switch is located above the  
power cord receptacle.  
Located above to the power switch is an LED Inticator:  
GREEN: the S-20 is operating normally.  
AMBER: the S-20 is in Standy Mode. When the S-20  
doesn’t hear an incoming signal after a period of time it  
will go into standy mode and will ‘wake up’ and come out  
of standby mode when it hears a signal.  
RED: the S-20 is in FAULT, consult the Troubleshooting  
section of this manual (pg. 5)  
Using the S-20 to augment the frequency response of  
powered mini-monitors:  
Connect the left and right outputs from your mixer or  
source unit to either the XLR, TRS or RCA jacks on the  
“INPUT” section of the S-20. Now connect the supplied  
left and right TRS cables from the “OUTPUT” jacks on  
the S-20 to your satellite monitors' input jacks. You may  
also want to connect a foot switch (or any standard 1/4”,  
2-position switch) into the BYPASS input on the rear of  
the S-20. Using this feature is not necessary to the basic  
operation of the S-20.  
The Port Plug:  
The S-20 subwoofer is designed to be used as either a  
bass reflex or acoustic suspension subwoofer. With the  
port plug removed, the subwoofer is a bass reflex sys-  
tem. With the plug in, the system is acoustic suspension.  
In bass reflex mode, the subwoofer will have lower bass  
extension and more output capability, but somewhat less-  
ened transient response. In acoustic suspension mode,  
the subwoofer will have less bass extension and output,  
but better transient response. In a room with a lot of low  
frequency standing waves or where the subwoofer must  
be placed in a corner, acoustic suspension mode will  
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INITIAL CONTROL SETTINGS:  
The S-20 subwoofer amplifier has a number of controls  
which can help you determine optimal placement. A little  
time spent experimenting with these options should yield  
just the right solution for your installation.  
Input Sensitivity Selection:  
This switch affects the input sensitivity of all three sets  
(XLR, TRS and RCA) of input jacks. When satellites  
are connected to the S-20, the subwoofer takes over  
as the master sensitivity control for the system.  
TECH TIP: The bypass foot switch is very helpful when  
setting up and tuning the S-20 to your room. When  
switching the woofer in and out, no tonal difference  
should be noticeable, just bass or no bass.  
IMPORTANT: Set the satellite speakers you're using  
to the +4 setting. Set the sensitivity on the S-20 to  
the appropriate setting for your source equipment.  
SYSTEM OPERATION  
HP Frequency Selection:  
If you are using NHTPro M-00 monitors as satellites, set  
the HP FREQ to the 110Hz setting. If you use a different  
brand of powered satellites try setting the switch to 110  
Hz when the satellite woofer size is 5” or smaller and  
80Hz if larger than 5”.  
The S-20 used in conjunction with good satellite  
monitors, like the M-00's, can play very loud with low  
distortion. Although designed to handle a wide range of  
listening levels, every speaker has its limits. Harsh  
breakup is an indication your monitors or the subwoofer  
have exceeded their output limits. Excessive boosting of  
bass, treble or equalizer controls can worsen the  
problem. If you hear continuous distortion or feel heat  
emanating from the drivers, reduce the level immediate-  
ly. Most speaker damage occurs from sustained high  
volume levels, not from transient sounds or brief musical  
peaks. Listening at high volume levels is potentially dan-  
gerous and can lead to permanent hearing loss,  
especially when listening in the near-field. Protect your  
ears and use common sense.  
Subwoofer Level Setting:  
The level you select will depend largely on placement.  
We suggest you start with this control in the 12 o'clock  
position. Move the control in a clockwise direction to  
increase bass output and counterclockwise to decrease  
it. Adjust the level so that the S-20 seamlessly integrates  
with the satellites, ie. you can tell it's operating but can't  
“hear” it as a separate entity.  
Low Pass Frequency Setting:  
Getting this setting right may take a little time. Using a  
variety of demo material you are very familiar with, start  
with the control in the 12 o'clock position. If the bass  
sounds too “punchy”, turn the control counter clockwise  
towards 80Hz. If the bass sounds thin, turn the control  
clockwise towards 110Hz.  
SYSTEM MAINTENANCE  
Your S-20 subwoofer needs no regular maintenance.  
The S-20 cabinet is finished with a durable, powder-coat  
paint. Light dusting is usually sufficient, although the  
cabinet can be cleaned with a non-abrasive, water  
based, cleaner.  
SUBWOOFER PLACEMENT:  
WARNING: To avoid risk of electrical shock, do not  
remove the amplifier from the rear of the cabinet.  
Refer all repairs to a qualified authorized service cen-  
ter. Always disconnect the S-20 from the AC power  
source prior to any maintenance.  
Where you locate the S-20 subwoofer will have a pro-  
found effect on the system's performance. Unfortunately,  
there are no hard and fast rules to find the best location.  
If you have some flexibility, we encourage you to experi-  
ment. The following guidelines should help you in your  
placement decisions:  
TROUBLESHOOTING  
Placement near walls and corners will reinforce low fre-  
quencies; conversely, placement out into open space will  
add definition, but will reduce bass weight and extension.  
If the S-20 fails to operate when the Power Switch is  
turned on, thoroughly check the power cord, input and  
output connections  
Ideally, the subwoofer should be adjusted so that you  
hear the additional bass extension, but cannot localize  
the subwoofer itself. The subwoofer should be placed  
somewhere in the same plane as the left and right moni-  
tors. Listen as you go, using a wide variety of program  
material. Jazz recordings with acoustic bass and piano  
are particularly helpful in determining location, sub level  
and crossover settings. Transparency and integration  
are the goals.  
If the S-20 turns on but the LED indicator fails to illumi-  
nate, mis-wiring or a power surge may have caused the  
amplifier to become damaged.  
If the S-20 turns on but its status LED appears AMBER,  
the unit has gone into FAULT (protect mode), which  
could be caused by incorrect wiring, short circuits, or  
excessive volume. Turn off the Power Switch on the sub-  
woofer for two or more seconds to reset. If this doesn’t  
help, contact NHT customer service.  
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TECHNICAL SUPPORT:  
Specifications:  
System Type  
Driver  
Toll free: 800-NHT-9993 (648-9993). Fax: 1-707-747-  
Bass Reflex  
or Sealed, Powered  
Postal Mail: NHTPro, 6400 Goodyear Road., Benicia,  
CA 94510  
10” Aluminum Cone  
(Not Video Shielded)  
Response  
32Hz - 110Hz +/- 3dB  
200 watts, Class D Amplifier  
35 lbs.  
Amplifier Power  
Weight  
Dimensions H” x W” x D”  
Finish  
17.5” x 12.2” x 15”  
Matte Black  
Per the EC directive of WEEE (Waste Electrical and Electronic  
Equipment) this product may not be disposed of as waste. It must be  
recycled through an approved recycling method. This recycling serv-  
ice shall be provided, at no cost to the consumer, by the distributor or  
retail outlet where the product was originally purchased. For recy-  
cling, the consumer should contact the place of original purchase for  
more information.  
**  
**16” with grille and rear panel controls.  
Allow additional room for wire dress.  
Limited Warranty  
Valid Only in the U.S.A.  
Warranty Period  
For a period of 5 years for parts and 5 years for labor (1 year parts and 90 days labor for electronics) from the date this product is first purchased from an authorized NHT  
dealer, Now Hear This (NHT) warrants that if it fails to function properly due to a manufacturing defect, despite its being installed and operated according to these instruc-  
tions and used under normal conditions, it will be either replaced or repaired with new or rebuilt parts (both at NHT's option) with a unit of comparable value without charge  
to you.  
What's Not Covered  
Altered, defaced or removed serial numbers void this warranty.  
This warranty does not cover any product used in trade, business, industrial or commercial applications.  
This warranty also does not cover the cabinet or appearance factors, or costs, defects or damage resulting from misuse, abuse, accident, improper maintenance, alter-  
ations or modifications not authorized in writing by NHT, or parts or labor from any source other than an authorized NHT service location.  
Damage due to power exposure in excess of the speaker's published power ratings; ie, overpowering, lightning or power surges, are also not covered.  
Your Rights  
This warranty gives you specific legal rights, and you may have other rights which vary from state to state.  
NHT limits this warranty to the purchase price of the product, excludes incidental or consequential damages, and limits its obligations under any implied warranties under  
state laws to a period not exceeding their warranty periods. As some states do not allow the above limitations, however, they may not apply to you.  
To Obtain Service  
To find the name and address of the nearest authorized NHT service location, call or write:  
For your future convenience, please keep this warranty with your sales receipt, and record date and place of purchase for further reference.  
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