In this review, we will be comparing Ultra Bookshelf and LS50, two Passive Bookshelf speakers from SVS and KEF.
Let's have a brief look at the main features
of SVS Ultra Bookshelf and KEF LS50 first before getting into our more
detailed comparison.
| Key Specs | SVS Ultra Bookshelf | KEF LS50 |
|---|
| Brand | SVS
United States · founded 1998 | KEF
United Kingdom · founded 1961 |
|---|
| Design | 2-way | 2-way |
|---|
| Uni-Q driver | — | 11th Generation Uni-Q |
|---|
| Tweeter | 1" Hard-Dome | 1" Vented dome |
|---|
| Woofer | 6.5" Composite glass-fiber | 5.25" Magnesium/aluminum alloy |
|---|
| Frequency response | 45-32k Hz | 79-28k Hz |
|---|
| Sensitivity | 87 dB | 85 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 20-150 watts | 25-100 watts |
|---|
| Weight | 8.64kg / 19lbs | 7.20kg / 15.8lbs |
|---|
| Dimensions (H x W x D) | 14-15/16" x 8-9/16" x 11-1/16"
380.0 x 218.0 x 281.0mm | 11.8" x 7.8" x 10.9"
302.0 x 200.0 x 278.0mm |
|---|
What size room are the SVS Ultra Bookshelf and KEF LS50 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* |
SVS Ultra Bookshelf |
KEF LS50 |
| Near-field |
Poor |
Average |
| Small Room |
Average |
Good |
| Mid-size Room |
Good |
Average |
| Large Room |
Average |
Poor |
| Very Large Room |
Poor |
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 Ultra Bookshelf and LS50 are 2-way speakers.
SVS Ultra BookshelfKEF LS50
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
SVS Ultra Bookshelf |
KEF LS50 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 6.5-inch
|
1 x 5.25-inch
|
Ultra Bookshelf features a 1" aluminum Hard-Dome Tweeter and 1 x 6.5" Composite glass-fiber Woofer with a Crossover frequency at 2000Hz. On the other hand, the LS50 features a 1" Aluminum Vented dome Tweeter and 1 x 5.25" Magnesium/aluminum alloy Woofer with a Crossover frequency at 2200Hz.
Frequency Response
Ultra Bookshelf has a frequency range of 45-32k Hz whereas LS50 has a frequency range of 79-28k Hz. With a minimum frequency of 45Hz, the Ultra Bookshelf can go significantly deeper on the low side and provide stronger bass compared to the LS50's min frequency of 79Hz.
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
Ultra Bookshelf and LS50 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. Ultra Bookshelf sensitivity is rated at 87 dB and the LS50's is at 85 dB. This 2 dB difference makes the SVS Ultra Bookshelf a more sensitive speaker compared to KEF LS50, 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.
Ultra Bookshelf can handle a max power of 150 watts RMS, whereas LS50 has a max power handling value of 100 watts RMS, 50 watts less than the Ultra Bookshelf.
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.
Input Type and Bi-Amping / Bi-Wiring
Ultra Bookshelf features 5-way post posts which make bi-amping or bi-wiring possible. LS50 has a Post which doesn't feature bi-amping/bi-wiring.
SVS Ultra Bookshelf's 5-way post terminals allows Bi-amping or bi-wiring
KEF LS50's Post terminals
Cabinet Type and Port Position
Both Ultra Bookshelf and LS50 have rear firing ports. Rear ported speakers generally need more room between the backside of the speaker and the wall compared to sealed and front/bottom ported speakers. Placing the speakers too close to the walls may cause the bass to sound boomy.
If you are limited in space and can't get the speakers away from the backwall, check our Speakers with Front Firing Ports page.
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 SVS Ultra Bookshelf's and KEF LS50's external dimensions. SVS Ultra Bookshelf has external dimensions of 380.0 x 218.0 x 281.0mm (14-15/16 x 8-9/16 x 11-1/16inch) whereas KEF LS50 has external dimensions of 302.0 x 200.0 x 278.0mm (11.8 x 7.8 x 10.9inch).
SVS Ultra Bookshelf is clearly the larger of the two speakers. Its body is 18mm wider, 78mm taller and 3mm deeper than KEF LS50.
Below you can see the front view size comparison of SVS Ultra Bookshelf and KEF LS50 in scale.
Comparison image of SVS Ultra Bookshelf and KEF LS50 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 SVS Ultra Bookshelf is approximately 612.6cm2 / 95.0inch2 and base area of the KEF LS50 is approximately 556.0cm2 / 86.2inch2. The Ultra Bookshelf requires 10% more surface area than the LS50 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 SVS Ultra Bookshelf and KEF LS50 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 SVS Ultra Bookshelf weighs 8.64kg / 19lbs and the KEF LS50 weighs 7.20kg / 15.8lbs. This makes the Ultra Bookshelf 20% heavier than the LS50.
Here is a comparison of how Ultra Bookshelf and LS50's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of SVS Ultra Bookshelf?
Here are the items that are included inside the box of Ultra Bookshelf:
- 2 Bookshelf loudspeakers
- 2 Grilles
- 8 Rubber feet
- 2 Terminal jumpers (pre-installed)
- Owners Manual
- SVS brochure
- Online Product Registration Card
What's in the Box of KEF LS50?
Here are the items that come with the LS50:
- 2 Bookshelf loudspeakers
- 2 Foam port plugs
- 8 Self-adhesive rubber feet
- Owner's Manual
- Warranty Registration Card
 Max Input Power |
150 watts
vs
100 watts
|
Handle more power from your amplifier |
 Sensitivity |
87 dB
vs
85 dB
|
Play louder with same amount of amplification power |
 Woofer Size |
6.5 inches
vs
5.25 inches
|
Larger woofer |
|
Low Frequency Response |
45 Hz
vs
79 Hz
|
Generates deeper bass |
 High Frequency Response |
32k Hz
vs
28k Hz
|
Generates higher frequency |
 Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
 Price per pair* |
1200USD
vs
1300USD
|
costs less (*prices may change depending on the seller, location and time) |
 Height |
302mm
vs
380mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
556cm2
vs
612cm2
|
Takes less floor space |
| General |
SVS Ultra Bookshelf |
KEF LS50 |
| Brand |
SVS |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-150 watts |
25-100 watts |
| Sensitivity |
87 dB |
85 dB |
| Impedance |
8 ohms |
8 ohms |
| Impedance |
n/a |
3.2 ohms |
| Frequency Response |
45-32k Hz |
79-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
6.5" |
5.25" |
| Woofer Composition |
Composite glass-fiber |
Magnesium/aluminum alloy |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Hard-Dome |
Vented dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2000Hz |
2200Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
380.0mm (15") |
302.0mm (11.9") |
| Width |
218.0mm (8.6") |
200.0mm (7.9") |
| Depth |
281.0mm (11.1") |
278.0mm (10.9") |
| Weight |
8.64kg (19lbs) |
7.20kg (15.8lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Oak veneer |
Polymer/Lacquer |
| Available Colors |
Black Oak,Piano Gloss Black,Piano Gloss White |
Black, High Gloss Piano Black, High Gloss Piano White |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
22-28" |
18-28" |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
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 | SVS Ultra Bookshelf digs deeper - 45Hz against 79Hz. |
| Amplifier needs | A | SVS Ultra Bookshelf is more sensitive (87dB vs 85dB), so it goes louder on the same amplifier. |
| Headroom | A | SVS Ultra Bookshelf takes more power (150W vs 100W) - more in hand in a big room. |
| Size | depends | KEF LS50 is easier to place; SVS Ultra Bookshelf is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | SVS Ultra Bookshelf: bi-amping. KEF LS50 sits in a wider range (10 models), so a matched surround system is easier later. |
| Price | evenly matched | Much the same money ($1,200 vs $1,300 a pair). |
A SVS Ultra Bookshelf B KEF LS50
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?
SVS Ultra Bookshelf 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 79Hz anyway, so judge these on the other rows instead. Match it to your room: we rate SVS Ultra Bookshelf the better fit for a mid-size room and a large room, and KEF LS50 for near-field listening and a small room.
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.