Which Sub. Rel B-1 or Fathom F-113

If you check HT Shack Subwoofer test you will see data on the JL F113 - it is pretty impressive (although distortion is a wee bit high - and compression does become an issue - however it is amazingly good for such a small sub - appears to beat everything else that size)

I am in favor of a sealed box for a sub like the JL (and the Rel B-1 is ported - so I am not sure what that does to the impressive low group delay of older generation Rel's - as I have not seen any data on the B-1 so far)

speed of the JL Audio drivers.

"speed' is a good description of the JL design. What does this mean in practice?

It means low group delay - which means critically damped design and generally a sealed box.

Compare the Group Delay and response plots from HT Shack Subwoofer Tests.

SVS PB13 ports open

SVS PB13 Sealed

Notice that a port can raise output level, reduce distortion however the trade off is Group Delay. Basically it allows the use of a cheaper driver and a smaller cheaper box to get the same undistorted output as a more expensive sealed box design.

Most subwoofers are intended to make a profit for the manufacturer and therefore you can guess which way most designs go......ported!

What is the downside to group delay. Well it means your bass will sound 'slow' like it does with bass bins folded horns at a concert...for each bass note you are getting an extra cycle or more from the subwoofer and hence it lacks "musicality" and there is a loss of accurate timbre.

A glance at the REL Storm 5 shows that it too has low group delay and is indeed a "fast" or musical sub. (I have seen no data on the B-1)