No disk streaming, all samples are stored in the 256mb RAM. I’m yet to hit the RAM limit, but I am careful with my files to ensure everything is perfectly looped, and loops are generally no more than four bars. If you’re looking to loop entire stems, the SP-16 isn’t for you - the maximum sample length is 32 seconds. I tend to make tracks out of mostly one-shots, with a few stereo loops between one and four bars long, typically between 136 and 148bpm.
Here’s a quote from a developer:
The SP-16 has 8GB of internal memory (flash ROM) and 256MB RAM for audio samples. The reason why we have limited the length of samples loaded is to ensure maximum performance utilising all performance features over all 16 TRACKS simultaneously. To switch between scenes whilst playing back the sequence, all of the samples used in the project must be loaded onto the RAM. Once above the 32 second sample length limit we start to jeopardise the performance of the hardware, hence why we need a sample length limit.
There are 16 TRACK’s and 16 SCENE’s, so in total there are 256 sample slots (16 x 16) in one PROJECT. The 256 sample slots share the 256MB RAM (without elaborating, 1MB per 1 sample slot). Here, we will calculate the the size of a 1 second sample as 44,100Hz x 3 Byte (24 bit) x 2 CH = 264KB. Note that some of these numbers have been rounded to the nearest whole number to make it easier to understand. 1MB divided by 264KB = 3.78 seconds. If you want to assign different samples to every TRACK in each SCENE, the samples have to be less than 3.78 seconds. Remember you have in total 256MB RAM to play with, so the previous is the most extreme. Generally, a project will consist of one shots and loops which are duplicates of other samples used across other SCENE’s. The total size of the samples exceeding 256MB is up to the user.
Next, we considered what the optimal and convenient length of a sample is. The SP-16’s pattern is up to 4 bars, so the longest loop is 16 seconds at 60 BPM. However, many users want to use longer loops and set the start/end point in the playback menu, for example, you could have a 32 second sample (16 bars at 120BPM) and select 8 seconds of that sample to create a 4 bar loop. Users would also like to record over 16 second samples, since recording guitars and vocals would require margins.
From the above reasons, we’ve balanced out the length and performance, choosing to limit the length of a sample to 32 seconds. Having said this, we are currently investigating how we can remove this limit but as its stands this is the current specification.