In this review, we will be comparing Foundation B1 and Q150, two Passive Bookshelf speakers from MartinLogan and KEF.
Let's have a brief look at the main features
of MartinLogan Foundation B1 and KEF Q150 first before getting into our more
detailed comparison.
| Key Specs | MartinLogan Foundation B1 | KEF Q150 |
|---|
| Design | 2-way | 2-way |
|---|
| Uni-Q driver | — | 11th Generation Uni-Q |
|---|
| Tweeter | 1" Folded Motion Ribbon | 1" Dome |
|---|
| Woofer | 5-1/2" Aluminum | 5.25" Aluminum |
|---|
| Frequency response | 48-23k Hz | 51-28k Hz |
|---|
| Sensitivity | 89 dB | 86 dB |
|---|
| Impedance | 5 ohms | 8 ohms |
|---|
| Power range | up to 100 watts | 10-100 watts |
|---|
| Weight | 5.23kg / 11.5lbs | 5.60kg / 12.3lbs |
|---|
| Dimensions (H x W x D) | 13-5/8" x 7-1/4" x 9-1/2"
347.0 x 185.0 x 242.0mm | 11.9" x 7.0" x 10.9"
303.0 x 180.0 x 278.0mm |
|---|
What size room are the MartinLogan Foundation B1 and KEF Q150 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* |
MartinLogan Foundation B1 |
KEF Q150 |
| 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.
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Drivers
Both Foundation B1 and Q150 are 2-way speakers.
MartinLogan Foundation B1KEF Q150
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
MartinLogan Foundation B1 |
KEF Q150 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5-1/2-inch
|
1 x 5.25-inch
|
Foundation B1 features a 1" Gen2 Obsidian Folded Motion Ribbon Tweeter and 1 x 5-1/2" Aluminum Woofer with a Crossover frequency at 3400Hz. On the other hand, the Q150 features a 1" vented aluminum Dome Tweeter and 1 x 5.25" Aluminum Woofer with a Crossover frequency at 2500Hz.
Frequency Response
Foundation B1 has a frequency range of 48-23k Hz whereas Q150 has a frequency range of 51-28k Hz. With a minimum frequency of 48Hz, the Foundation B1 can go slightly deeper then the Q150's min frequency of 51Hz.
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
Foundation B1 is a 5 ohms speaker compared to the Q150 which has a nominal impedance of 8 ohms.
These two speakers also have different sensitivity levels. Foundation B1 sensitivity is rated at 89 dB and the Q150's is rated at 86 dB. This 3 dB difference makes the MartinLogan Foundation B1 a more sensitive speaker compared to KEF Q150, 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.
Both handle the same maximum of 100 watts RMS, though Foundation B1 is rated up to 100 watts and Q150 10-100 watts.
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.
MartinLogan Foundation B1
Input Type and Bi-Amping / Bi-Wiring
Foundation B1 features Post type posts and Q150 has a Post type posts. None of these speakers feature bi-amping/bi-wiring.
MartinLogan Foundation B1's Binding post terminals
KEF Q150's Post terminals
Cabinet Type and Port Position
Both Foundation B1 and Q150 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.
KEF Q150 Port
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 MartinLogan Foundation B1's and KEF Q150's external dimensions. MartinLogan Foundation B1 has external dimensions of 347.0 x 185.0 x 242.0mm (13-5/8inch x 7-1/4inch x 9-1/2inch) whereas KEF Q150 has external dimensions of 303.0 x 180.0 x 278.0mm (11.9 x 7.0 x 10.9inch).
KEF Q150 is 5mm narrower and 44mm shorter than MartinLogan Foundation B1 but it is also 36mm deeper.
Below you can see the front view size comparison of MartinLogan Foundation B1 and KEF Q150 in scale.
Comparison image of MartinLogan Foundation B1 and KEF Q150 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 MartinLogan Foundation B1 is approximately 447.7cm2 / 69.4inch2 and base area of the KEF Q150 is approximately 500.4cm2 / 77.6inch2. The Foundation B1 requires 11% less surface area than the Q150 which gives it a small advantage 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 MartinLogan Foundation B1 and KEF Q150 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 MartinLogan Foundation B1 weighs 5.23kg / 11.5lbs and the KEF Q150 weighs 5.60kg / 12.3lbs. This makes the Q150 7% heavier than the Foundation B1.
Here is a comparison of how Foundation B1 and Q150's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
MartinLogan Foundation B1
What's in the Box of KEF Q150?
Here are the items that come with the Q150:
- 2 Bookshelf loudspeakers
- 2 Foam port plugs
- 8 Self-adhesive rubber feet
- Owner's Manual
- Warranty Registration Card
 Sensitivity |
89 dB
vs
86 dB
|
Play louder with same amount of amplification power |
 Low Frequency Response |
48 Hz
vs
51 Hz
|
Generates deeper bass |
 Base Surface Area |
447cm2
vs
500cm2
|
Takes less floor space |
 Price per pair* |
599USD
vs
600USD
|
costs less (*prices may change depending on the seller, location and time) |
 Nominal Impedance |
8 ohms
vs
5 ohms
|
Less selective with amplifiers |
|
Woofer Size |
5.25 inches
vs
5-1/2 inches
|
Larger woofer |
 High Frequency Response |
28k Hz
vs
23k Hz
|
Generates higher frequency |
 Height |
303mm
vs
347mm
|
Easier to fit in smaller spaces |
| General |
MartinLogan Foundation B1 |
KEF Q150 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
up to 100 watts |
10-100 watts |
| Sensitivity |
89 dB |
86 dB |
| Impedance |
5 ohms |
8 ohms |
| Impedance |
n/a |
3.7 ohms |
| Frequency Response |
48-23k Hz |
51-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5-1/2" |
5.25" |
| Woofer Composition |
Aluminum |
Aluminum |
| Woofer Surround Material |
n/a |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Folded Motion Ribbon |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
3400Hz |
2500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
347.0mm (13.7") |
303.0mm (11.9") |
| Width |
185.0mm (7.3") |
180.0mm (7.1") |
| Depth |
242.0mm (9.5") |
278.0mm (10.9") |
| Weight |
5.23kg (11.5lbs) |
5.60kg (12.3lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
n/a |
MDF/Vinyl-wrapped |
| Available Colors |
Walnut,Black,Satin White |
Black, Walnut, White |
| Mounting Bracket |
|
No |
| Recommended Stand Height |
n/a |
18-24" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
No |
Other |
|
|
| Parts Warranty |
5 years |
5 Years |
| Labor Warranty |
5 years |
5 Years |
A generation apart: MartinLogan Foundation B1 is the newer design, against a 2019 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass |
A |
MartinLogan Foundation B1 digs deeper - 48Hz against 51Hz. A subwoofer would even that out. |
| Amplifier needs |
A |
MartinLogan Foundation B1 is more sensitive (89dB vs 86dB), so it goes louder on the same amplifier. |
| Amplifier match |
B |
KEF Q150 is the easier load at 8 ohms. |
| Headroom |
evenly matched |
Similar power handling (100W vs 100W). |
| Size |
depends |
Similar cabinet size - neither is easier to fit. |
| Price |
evenly matched |
Much the same money ($599 vs $600 a pair). |
A MartinLogan Foundation B1
B KEF Q150
depends neither is better in the abstract - it turns on your room, placement 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?
MartinLogan Foundation B1 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 your amplifier is modest, vintage or valve-based, MartinLogan Foundation B1 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.