I bought it last year and use it for small events.
Its main strength is, without a doubt, its ease of use, its almost plug'n'play!
It has two XLR inputs, two 1/4" jack/XLR inputs (including one with a Hi-Z button) and two Line Inputs, one on RCA and the other one on minijack. You could connect a whole band, except for the drummer. Apart from that, it has yet another (stereo) monitoring output and inputs for the footswitches (not included) and a digital reverb
The sound, be it a low or high volumes, is very good and precise. The EQ is very "extreme," you need to be subtle, like with the reverb (it's easy to get carried away). I like the EQ Master a lot, which allows you to either boost the low end to listen to music or reduce it to hear better the vocals.
I haven't found any negative aspects right now. You certainly shouldn't expect to be able to do large concert halls, but it is more than enough for a bar or a small stage.
When you get a Yamaha you know you're getting good quality. Be it for speech or for a music group, I think it's a great value for money. It remains to be seen how long the mixer will last.
I bought the stagepas for a very specific application: To reinforce a small acoustic combo (piano - guitar - vocals). The stagepas 400i is perfect for this application! The vocals are rendered very well, the piano and the guitar are reproduced with a good precision across all frequencies, and the effects (reverb, etc.) are really nice.
What I like the most about this product is the hyper-warm Yamaha sound. No instrument is distorted, the vocals sound really good.
Careful: It's obvious that this small PA system won't be enough for an entire electric band. Electric guitars don't work (maybe with a POD, an even then...) and some frequencies overlap.
To cut it short, an excellent portable PA system for setups like ours or as a monitor speaker for piano and vocals (bear in mind the limited power of the 400i). If you want to do bigger concert halls and electric sets you'd better get something more powerful.
On paper, 400 watts into 4 ohms! It's obviously "dynamic." An exotic output power. In fact, it's rated at 125 watts before clipping (with 1% THD, 1khz @ 1W) per channel into the same impedance (percentage of the 3rd harmonic with respect to the root note). Nominal, it's no more than 37 watts! The power divided by 5, two times 40 watts RMS!!! In practice, you will never have more than 50 watts per channel. Enough for a musician to do a small hall, especially if you connect all your instruments to the small mixer.
The mic inputs are very faithful for vocals, especially with dynamic mics. As a PA system with around 100 people in the audience (applying a 1 watt/1meter per person rule), it's a reasonable choice that won't hurt your budget. The Stagepass 400I is rated at 125 db SPL, but in the manual there's not a single word about the speakers, which is 8" big and seems quite stiff, so you will need to break it in to get the best of it. The Bass Reflex speakers almost don't vibrate at all and have a good diffraction.
The StagePas 400I is IPOD and IPhone compatible, according to the manual. But not only. First generation IPADs are also welcome. And even more so the later versions. The Stagepass 400I plays the audio and recharges the iPAD! MP3s obviously. A good EQ is needed for pre-mixing. A limiter and an EQ per band will do the job. To get better results you can use an external CD player. You should preferably listen to the mix using the monitor's mono output to avoid phase shifts. A drawback is that it has no stereo headphone connector for the controls. The simple addition of a powered sub of at least 120 watts RMS will give this system the power it lacks in the bottom end.
In conclusion, the Yamaha StagePas 400I is not exceptional on paper, in terms of power characteristics, for a low-end PA system. On the other hand, its overall quality is all right. And its durability is a bonus.
There's always a but... in this case it's the sound the amp's cooling fans make! It's useless in "quiet" environments, which is a pity (it seems to be a chronic issue with all stagepasses).
It's OK for bars.
It has the typical Yamaha sound: The mids are very present and detailed. I'm used to it but it's very particular.
It's not the best for dub or electronic music with deep lows.
Diverse connection options, even for iThings via USB...nice.
No pan...which is strange (and a pity, in my view)
Power: OK for small bars, I haven't tried it in bigger stages.
The system is easily transportable.