Size comparison: Marshall Stanmore II at the top and Woburn II at the bottom.
In Marshall's line-up, Woburn II and Stanmore II are the first and second largest bluetooth speakers. Woburn II is more like a living room speaker whereas the Stanmore II is more like a shelf speaker.
In summary, owing to its extra 50 W woofer (a HUGE difference), Marshall Woburn II is not only louder than the Stanmore II, but it's also more satisfying to listen to - even at lower volume levels.
Now let's get to their bolts and nuts.
In summary, owing to its extra 50 W woofer (a HUGE difference), Woburn II is not only louder than the Stanmore II, but it's also more satisfying to listen to - even at lower volume levels.
Loudness
Although the Woburn is louder, Stanmore II is still significantly loud. For most people, at full volume, it's even drunk party level loud.
In their product manuals (Manual of Stanmore II [PDF] - Manual of Woburn II [PDF]), you can see that the maximum sound pressure level of Stanmore II stands at 101 dB.
Whereas that of the Woburn II is at 110 dB.
In their manuals you'll also see that the Stanmore II is equipped with 2 pieces of 15 Watt Class D amplifiers for the tweeters and one piece of 50 Watt Class D amplifier for the woofer.
The tweeters are smaller amplifiers are able to vibrate quicker. They're responsible for producing high frequency sounds.
Whereas the woofers are the larger amplifiers, placed at the bottom of speakers, under the tweeters. They produce lower frequency sounds.
In addition to these exact amplifiers in the Marshall Stanmore II, Woburn II steps up its game and brings in an additional 50 W woofer in the table.
Now this is what I call a huge difference.
Having an equally powerful, extra woofer is a game changer. It's like equipping the same airplane with two more engines.
Marshall Stanmore II.
Now you might think to yourself that the difference in the decibel department doesn't seem to reflect that much of a difference: 110 vs 101 dB.
But there's one part you got wrong there: Decibel scale is logarithmic, not linear.
This means that the difference between them is FAR more than the difference between two speakers at, say, 51 and 60 dB.
Same amount increase in the dB scale, but far different results.
So, in reality, assuming everything else is equal, a 110 dB speaker will almost be twice as loud as a 101 dB speaker.
But loudness isn't the only advantage you get with an extra woofer. There's another advantage, and to most people (including me and probably you), it's even a more important one.
Sound quality
Let me tell you something right off the bat.
Room acoustics, particularly room dimensions and speaker positioning, will have an immense effect on sound quality.
The impact of the combination of these two is actually so strong that in most cases, it doesn't even make sense to utter a single word on sound quality without speaking of them.
This is why I'd hiiiiiiighly recommend you to check out this simple, 2D, online speaker placement calculator. I've had an Acoustics & Audio PhD build this tool specifically for this purpose. It's also completely free and mobile compatible. It's GOOOOLLLDDDDD.
ASAP Science made a video on the loudest and quietest rooms in the world. A mind blowing example of the importance of acoustics (time adjusted video).
Other parameters such as the age/materials of the building, the furniture & carpets in place, ceiling height, etc can and will, of course, have an effect on room acoustics, too. But much less.
Anyways...
The extra woofer in Marshall Woburn II will help it product more satisfying sounds compared to Stanmore II. You can see also this being reflected to the technical specs in the lower frequency department.
Notice the horizontal beige stripe at the bottom of this Marshall Woburn II. Base (not II) models of both Woburn and Stanmore speakers lack this stripe - which you can use to distinguish them from one another.
Stanmore II is listed at 50 - 20,000 Hz whereas the Woburn II at 30 - 20,000 Hz (find source at their manuals: Manual of Stanmore II [PDF] - Manual of Woburn II [PDF]).
The lower number is the lowest sound the speaker cone can emit. May be lower than you can actually hear. Probably not the most important stat to look for in speaker specs but it’s there.
Marshall Woburn II is not only able to produce sounds with frequencies lower than 50 Hz, but it's also able to produce sounds with frequencies up to 2,000 Hz noticeably better.
Lower frequency sounds does NOT simply represent bass strength. It's deeper than that.
The take away here is that the Marshall Woburn II will be able to produce more quality sounds than the Marshall Stanmore II.
Durability
Before you pull the trigger and buy one of these speakers, I'd recommend you to consider durability as well.
If you won't be gentle to these speakers, then certainly don't get them. Their coverage and overall structure aren't made to stand against strikes and scratches. To me it feels like it's almost possible to peel the surface with my bare fingertips.
These 60's rock and roll hipster speakers are made to be an elegant and functional piece of your authentically furnished home, boutique store, or a music studio.
You can't toss them around or throw them into the back of your pick-up truck and forget about them.
You get the picture. Their outer shell is vulnerable.
Conclusion
I'd recommend you to base your decision primarily on the living space you'll place these speakers.
Get the Marshall Woburn II for a living room and the Stanmore II for a smaller room.
Some good reviews:
Marshall Woburn II Bluetooth Review
Marshall Stanmore II Review