In this review, we will be comparing Nero MB5 and R-51M, two Passive Bookshelf speakers from OSD and Klipsch.
Let's have a brief look at the main features
of OSD Nero MB5 and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | OSD Nero MB5 | Klipsch R-51M |
|---|
| Brand | OSD
United States · founded 2003 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Soft-Dome | 1" Tractrix Horn |
|---|
| Woofer | 5.25" Fiberglass | 5.25" Copper-spun IMG |
|---|
| Frequency response | 50-30k Hz | 62-21k Hz |
|---|
| Sensitivity | 90 dB | 93 dB |
|---|
| Impedance | 4 ohms | 8 ohms |
|---|
| Power range | 100 watts | Up to 85 watts |
|---|
| Weight | 5.45kg / 12lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 11-15/16" x 7-5/16" x 9-5/8"
304.0 x 177.8 x 245.0mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
What size room are the OSD Nero MB5 and Klipsch R-51M speakers good for?
The size of the room in which you are planning to use these loudspeakers is an important decision
factor. Here we have compared their suitability to various sizes of environments considering their size
and max power parameters:
| Listening Environment* |
OSD Nero MB5 |
Klipsch R-51M |
| Near-field |
Average |
Average |
| Small Room |
Good |
Good |
| Mid-size Room |
Average |
Average |
| Large Room |
Poor |
Poor |
| Very Large Room |
Bad |
Bad |
(* Approximate Room sizes: Small < 100sq. ft / 9 m2,
Mid-size: 100-220 sq. ft / 9-20 m2, Large 220-400 sq. ft / 20-36 m2, Very Large: >
400 sq. ft / 36 m2.
Average Floor Height: 9" / 2.7m. Typical room sizes differ from country to country, and the actual
listening experience changes depending on floor height, room shape, surface materials, listening
position, speaker locations, etc.)
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
Drivers
Both Nero MB5 and R-51M are 2-way speakers.
OSD Nero MB5Klipsch R-51M
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
OSD Nero MB5 |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-inch
|
Nero MB5 features a 1" Soft-Dome Tweeter and 1 x 5.25" Fiberglass Woofer. On the other hand, the R-51M features a 1" Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1660Hz.
Frequency Response
Nero MB5 has a frequency range of 50-30k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 50Hz, the Nero MB5 can go significantly deeper on the low side and provide stronger bass compared to the R-51M's min frequency of 62Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
Neither pair reaches down to 20Hz, the usual definition of full-range, which is normal for speakers of this size. If you want the bottom octave for movies or bass-heavy music, add a subwoofer to whichever you choose. Visit our Powered Subwoofers section to find out more about the available options.
Impedance and Sensitivity
Nero MB5 is a 4 ohms speaker compared to the R-51M which has a nominal impedance of 8 ohms. Lower impedance speakers, especially the ones that are rated at 4 ohms may put more pressure on the amplifier unit especially when played at high volume levels, so make sure the amp you pair with the Nero MB5 can provide this impedance level.
These two speakers also have different sensitivity levels. Nero MB5 sensitivity is rated at 90 dB and the R-51M's is rated at 93 dB. This 3 dB difference makes the Klipsch R-51M a more sensitive speaker compared to OSD Nero MB5, hence will play louder with the same amount of watts.
Sensitivity
Bookshelf Speakers
Power Range
Power
range is the range of input power in watts RMS that a loudspeaker is designed to handle. Staying
within that range gives nominal performance; driving the speaker beyond its maximum wattage can damage it.
Nero MB5 can handle a max power of 100 watts RMS, whereas R-51M has a max power handling value of 85 watts RMS, 15 watts less than the Nero MB5.
Note that higher power handling does not make a speaker louder: that depends mainly on
sensitivity and impedance. The calculator below shows how loud each of these actually plays
on a real amplifier.
Which plays louder on your amplifier?
Starting with a popular amplifier - change it to the one you own, or any you are
considering, and watch both numbers move.
Physical Specs
The size of a speaker can sometimes be an important decision factor due to space constraints or in some cases purely for esthetic reasons. In this section, we are going to compare OSD Nero MB5's and Klipsch R-51M's external dimensions. OSD Nero MB5 has external dimensions of 304.0 x 177.8 x 245.0mm (11-15/16inch x 7-5/16inch x 9-5/8inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch).
OSD Nero MB5 is 0.19999999999999mm narrower and 34mm shorter than Klipsch R-51M but it is also 30mm deeper.
Below you can see the front view size comparison of OSD Nero MB5 and Klipsch R-51M in scale.
Comparison image of OSD Nero MB5 and Klipsch R-51M Size and External Dimensions
Base Surface Area Comparison
Base surface area of a loudspeaker may become a determining factor when the space in your room or desk is limited.
The base surface area of the OSD Nero MB5 is approximately 435.6cm2 / 67.5inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The Nero MB5 requires 14% more surface area than the R-51M which gives it a small disadvantage on placement in tight spaces.
Here is another comparison that shows both speakers on a BDI Octave Media Cabinet, next to a standard size amplifier and turntable in scale:
Size Comparison image of OSD Nero MB5 and Klipsch R-51M on a Media Console
Weight Comparison The weight of a loudspeaker can become an important factor if you need to move and reposition the unit often. Weight of a speaker can also "sometimes" be an indicator of the rigidity of the enclosure and the quality of the internal components used. The OSD Nero MB5 weighs 5.45kg / 12lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the Nero MB5 9% heavier than the R-51M.
Here is a comparison of how Nero MB5 and R-51M's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of OSD Nero MB5?
Here are the items that are included inside the box of Nero MB5:
- 2 Bookshelf loudspeakers
- 2 Grilles
What's in the Box of Klipsch R-51M?
Here are the items that come with the R-51M:
- 2 Bookshelf loudspeakers
- 2 Grilles (installed)
- 8 Self-adhesive rubber feet
- Quick Setup Guide
- Important Safety Instructions
- Warranty Information
 Max Input Power |
100 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
50 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
30k Hz
vs
21k Hz
|
Generates higher frequency |
 Height |
304mm
vs
338mm
|
Easier to fit in smaller spaces |
 Sensitivity |
93 dB
vs
90 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
4 ohms
|
Less selective with amplifiers |
 Base Surface Area |
382cm2
vs
435cm2
|
Takes less floor space |
| General |
OSD Nero MB5 |
Klipsch Reference R-51M |
| Brand |
OSD |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
100 watts |
Up to 85 watts |
| Sensitivity |
90 dB |
93 dB |
| Impedance |
4 ohms |
8 ohms |
| Frequency Response |
50-30k Hz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Fiberglass |
Copper-spun IMG |
| Woofer Surround Material |
n/a |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Soft-Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
1660Hz |
| Firing Direction |
n/a |
rear |
Physical Specs |
|
|
| Height |
304.0mm (12") |
338.0mm (13.3") |
| Width |
177.8mm (7") |
178.0mm (7") |
| Depth |
245.0mm (9.6") |
215.0mm (8.5") |
| Weight |
5.45kg (12lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
n/a |
MDF/Wood-grain vinyl |
| Available Colors |
Black |
Black |
| Mounting Bracket |
|
No |
| Recommended Stand Height |
n/a |
24-28" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
n/a |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
No single best speaker here - they are built to different priorities, and the right one depends on your room, your amplifier and what you listen to.
| Area | Better | Why |
|---|
| Bass | A | OSD Nero MB5 digs deeper - 50Hz against 62Hz. |
| Amplifier needs | B | Klipsch R-51M is more sensitive (93dB vs 90dB), so it goes louder on the same amplifier. |
| Amplifier match | B | Klipsch R-51M is the easier load at 8 ohms; the other is 4 ohms and wants an amplifier rated for it. |
| Headroom | evenly matched | Similar power handling (100W vs 85W). |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | depends | Neither adds bi-amping, a sub output or height drivers. Klipsch R-51M sits in a wider range (5 models), so a matched surround system is easier later. |
A OSD Nero MB5 B Klipsch R-51M
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Klipsch R-51M has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 62Hz anyway, so judge these on the other rows instead. If your amplifier is modest, vintage or valve-based, Klipsch R-51M is the safer partner - the other will want more current or more watts to sound its best.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.