Never specifically tested it, but it wouldn’t surprise me. The Roam not only has smaller speakers it can drive than the PLAY:1 does, but it’s also designed to not use too much battery. Significantly different types of speakers, with significantly different designs and purposes.

The Move is basically a portable Play:1, very similar size and volume.

The volume numbers are not comparable between products.  They just represent a 0 - 100 scale from silent to max volume.

I don't think it's a linear scale, btw, but not sure what the curve is (logarithmic?)

OK, thank you for the responses so far. I still would like to hear from someone who has my setup, specifically a Play:1 or One, and a Roam, and please comment on how the volumes of those 2 specifically compare when each is set to the same volume setting. Do you find your One or Play:1 about twice as loud as the Roam when each is set to about 20-25 volume? Do you find that to get the same loudness from the Roam when the One of Play:1 is set to 20, you have to set the Roam to about 40? Thank you. 

I have no idea how to judge how twice as loud sounds, but I  can confirm that a Play:1 is significantly more powerful than a Roam.

What is the cause of your concern? Are you worried that your Roam may be faulty?

I, also, don’t have a db meter. Nor is this of significant issue, IMHO, as I have both, and use the Roam as designed for a personal speaker, and the PLAY:1s (and Ones) as surrounds, and music speakers. 

Not at all scientific, but using a mobile dB meter App (set approx. equidistant from both and ‘no’ I didn’t measure it, but around one metre away) .. the Roam gave me an average reading of 33dB and the Sonos One an average of 46dB at volume level 20

For volume level 50 - The Roam average showed 46dB

For volume level 50 - The One average showed 66dB

I’m not sure why this is being discussed however, as they’re different size speakers and the 0-100% volume range is there to fit every Sonos speakers volume range/abilities, but who sets different sized speakers to the same volume-level, thinking they ‘might’ give the same output anyway across all the available volume range‍♂️?

It is what it is ..and clearly what the Sonos Engineers have chosen to put in place in the grand scheme of all the products they produce. These things may even change from time to time with firmware updates.

Anyow, those were my ‘slightly assisted’ observations in the ‘quick’ rough’n’ready tests done here.

yeah, ok, the reason I’m asking this is because I was wondering if the speaker is faulty. Also, I have all the speakers reduced max volume to the correct degree based on the size room they’re in, so that I can control all the volumes with the master slider volume, don’t ever have to individually adjust any of the speakers, which is very convenient. So this Roam is behaving differently, and now I have to deal with adjusting its volume separate from the others, which is a bit of a pain. Thanks anyway. 

I would think a Five and a Play:3 will each be different too. Different amplification electronics, different speakers and different enclosures will all have a bearing on the overall volume and sound. That’s all a part of the fun of selecting a music system that (to you) sounds good.