In this review, we will be comparing SCM11 and P3ESR XD2, two Passive Bookshelf speakers from ATC and Harbeth.
Let's have a brief look at the main features
of ATC SCM11 and Harbeth P3ESR XD2 first before getting into our more
detailed comparison.
| Key Specs | ATC SCM11 | Harbeth P3ESR XD2 |
|---|
| Brand | ATC
United Kingdom · founded 1974 | Harbeth
United Kingdom · founded 1977 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 0.98" | 0.75" Dome |
|---|
| Woofer | 5.91" | 4.5" RADIAL |
|---|
| Frequency response | 56-22k Hz | 75-20k Hz |
|---|
| Sensitivity | 85 dB | 83 dB |
|---|
| Impedance | 8 ohms | 6 ohms |
|---|
| Power range | 75 to 300 Watts watts | 15-50 watts |
|---|
| Weight | 10.90kg / 24lbs | 6.10kg / 13.4lbs |
|---|
| Dimensions (H x W x D) | 15" x 9.13" x 9.29"
381.0 x 232.0 x 236.0mm | 12-1/16" x 7-1/2" x 7-1/4"
306.0 x 190.0 x 184.0mm |
|---|
What size room are the ATC SCM11 and Harbeth P3ESR XD2 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* |
ATC SCM11 |
Harbeth P3ESR XD2 |
| Near-field |
Good |
Good |
| Small Room |
Good |
Good |
| Mid-size Room |
Average |
Average |
| Large Room |
Poor |
Poor |
| Very Large Room |
No way |
No way |
(* 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 SCM11 and P3ESR XD2 are 2-way speakers.
ATC SCM11Harbeth P3ESR XD2
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
ATC SCM11 |
Harbeth P3ESR XD2 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
0.98-inch
|
0.75-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.91-inch
|
1 x 4.5-inch
|
SCM11 features a 0.98" Tweeter and 1 x 5.91" Woofer with a Crossover frequency at 2.2kHz. On the other hand, the P3ESR XD2 features a 0.75" Ferrofluid-cooled dome Dome Tweeter and 1 x 4.5" RADIAL Woofer.
Frequency Response
SCM11 has a frequency range of 56-22k Hz whereas P3ESR XD2 has a frequency range of 75-20k Hz. With a minimum frequency of 56Hz, the SCM11 can go significantly deeper on the low side and provide stronger bass compared to the P3ESR XD2's min frequency of 75Hz.
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
SCM11 is a 8 ohms speaker compared to the P3ESR XD2 which has a nominal impedance of 6 ohms.
These two speakers also have different sensitivity levels. SCM11 sensitivity is rated at 85 dB and the P3ESR XD2's is rated at 83 dB. This 2 dB difference makes the ATC SCM11 a more sensitive speaker compared to Harbeth P3ESR XD2, 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.
SCM11 can handle a max power of 300 watts RMS, whereas P3ESR XD2 has a max power handling value of 50 watts RMS, 250 watts less than the SCM11.
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
SCM11 features Binding post type posts and P3ESR XD2 has a Binding post type posts. None of these speakers feature bi-amping/bi-wiring.
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 ATC SCM11's and Harbeth P3ESR XD2's external dimensions. ATC SCM11 has external dimensions of 381.0 x 232.0 x 236.0mm (15 x 9.13 x 9.29inch) whereas Harbeth P3ESR XD2 has external dimensions of 306.0 x 190.0 x 184.0mm (12-1/16 x 7-1/2 x 7-1/4inch).
ATC SCM11 is clearly the larger of the two speakers. Its body is 42mm wider, 75mm taller and 52mm deeper than Harbeth P3ESR XD2.
Size, drawn to scale
Both speakers and both views share one scale, so everything here is directly comparable. Hover a box for its dimensions.
One scale for both, standing on the same surface and pushed back to the same wall, so the deeper one visibly sticks out further.
ATC SCM11 needs about 57% more floor or shelf area. ATC SCM11 is 52mm deeper, so it stands that much further out from the wall. ATC SCM11 is 75mm taller.
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 ATC SCM11 is approximately 547.5cm2 / 84.9inch2 and base area of the Harbeth P3ESR XD2 is approximately 349.6cm2 / 54.2inch2. The SCM11 requires 57% more surface area than the P3ESR XD2 which gives it a small disadvantage on placement in tight spaces.
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 ATC SCM11 weighs 10.90kg / 24lbs and the Harbeth P3ESR XD2 weighs 6.10kg / 13.4lbs. This makes the SCM11 79% heavier than the P3ESR XD2.
Here is a comparison of how SCM11 and P3ESR XD2's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
 Max Input Power |
300 watts
vs
50 watts
|
Handle more power from your amplifier |
 Sensitivity |
85 dB
vs
83 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
6 ohms
|
Less selective with amplifiers |
 Woofer Size |
5.91 inches
vs
4.5 inches
|
Larger woofer |
|
Low Frequency Response |
56 Hz
vs
75 Hz
|
Generates deeper bass |
 High Frequency Response |
22k Hz
vs
20k Hz
|
Generates higher frequency |
 Price per pair* |
2699USD
vs
3790USD
|
costs less (*prices may change depending on the seller, location and time) |
 Height |
306mm
vs
381mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
349cm2
vs
547cm2
|
Takes less floor space |
| General |
ATC SCM11 |
Harbeth P3ESR XD2 |
| Brand |
ATC |
Harbeth |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
75 to 300 Watts watts |
15-50 watts |
| Sensitivity |
85 dB |
83 dB |
| Impedance |
8 ohms |
6 ohms |
| Frequency Response |
56-22k Hz |
75-20k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.91" |
4.5" |
| Woofer Composition |
|
RADIAL |
| Tweeter Size |
0.98" |
0.75" |
| Tweeter Type |
n/a |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2.2kHz |
n/a |
Physical Specs |
|
|
| Height |
381.0mm (15") |
306.0mm (12") |
| Width |
232.0mm (9.1") |
190.0mm (7.5") |
| Depth |
236.0mm (9.3") |
184.0mm (7.2") |
| Weight |
10.90kg (24lbs) |
6.10kg (13.4lbs) |
| Enclosure |
Sealed |
Bass Reflex |
| Mounting Bracket |
|
|
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
n/a |
No |
Other |
|
|
| Parts Warranty |
|
5 Years |
| Labor Warranty |
|
5 Years |
A generation apart: Harbeth P3ESR XD2 is the newer design, against a 2018 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 | ATC SCM11 digs deeper - 56Hz against 75Hz. |
| Amplifier needs | A | ATC SCM11 is more sensitive (85dB vs 83dB), so it goes louder on the same amplifier. |
| Amplifier match | A | ATC SCM11 is the easier load at 8 ohms. |
| Headroom | A | ATC SCM11 takes more power (300W vs 50W) - more in hand in a big room. |
| Size | depends | Harbeth P3ESR XD2 is easier to place; ATC SCM11 is bigger, which usually goes with fuller bass. Your room decides. |
| Cabinet | depends | Sealed vs Ported. Sealed is tighter and happier near a wall; ported digs lower but wants space behind it. |
| Price | A | ATC SCM11 is cheaper - $2,699 against $3,790, about 29% less. |
A ATC SCM11 B Harbeth P3ESR XD2
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?
ATC SCM11 is the easier recommendation: it leads on most of the measured areas and costs less. Take Harbeth P3ESR XD2 if its size, looks or fit in your room suit you better. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 75Hz anyway, so judge these on the other rows instead. In a large or open-plan room, ATC SCM11 has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Harbeth P3ESR XD2 is the easier speaker to get right.
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.