I've enjoyed getting acquainted with the B2 Four. Because there's not a lot of review info out there, I offer this review for users and potential buyers. It has some info not found in the docs or online. Strap in, though, it's a long one. I hope you find it helpful.
HARDWARE
The design and build-quality seem like a good balance of durability, simplicity, and functionality. The 1/4" jacks are metal, mounted on the plastic chassis. The 3.5mm headphone & aux in jacks are not metal and not chassis-mounted. Buttons all feel solid. The recessed 9V power jack is clever, but might not fit some power cords.
The cursor buttons are difficult to use with the foot. Pressing the right buttons our foot blocks the display. A diamond configuration would have been more intuitive and easier access with a foot; especially if the buttons had carefully-designed raised shapes.
Where it counts, the display is bright enough, and easy enough to read for calling up presets and menu operations. For editing, bring it up off the floor, and/or use the GL for B2 Four app.
Turning off with the power button, the display shows "Please wait... Saving Settings." So is powering off by unplugging or power strip switch a bad idea?
ROUTING
With only 5-slots, a serial-only path, and no send-return loop; routing options are limited. Fortunately, we can place any FX in any order (within CPU constraints). The DI/XLR out and 1/4" outs are both fixed as post-FX. So both can be wet, or both can be dry, but we can't have dry DI and wet 1/4" outs, which would have been useful.
The mono input can be run through stereo reverbs, delays, and mod FX. However, if we place any mono module after a stereo module, the signal becomes mono (unless the mono modules are bypassed) This also applies to the DI model. Even if those mono modules have wet/dry mix, the dry output is always mono. So if we want to hear stereo FX, they must be placed AFTER any mono FX modules, and the DI model must be OFF.
LEVELS
The global EQ with 3 fixed bands (low/mid/high) and a master volume are helpful. However, the lack of a patch-volume setting is disappointing. This requires us to control levels via preamps, amps and fx in ways that won't affect tone. This just means more steps. As long as we do an occasional A/B comparison of dry bass level (bypass all) with the level of the patch, we can probably stay within a reasonable range.
EQ/TONE CONTROL
Because of the multi-layer convolution, the amp/cab combos are hardwired (no IR swapping or user IR's).
With EQ we can adjust the tone/character pretty freely. The EQ modules include a low shelf/HPF, a single-band sweepable peak/notch, and a high shelf/LPF, graphic EQs, a splitter, and an exciter. The parametric EQ's are one-band-per-module, so we use up three slots to get a 3-band parametric. Some of the preamps and amps have EQs, with either fixed frequencies or just a few selections.
GENERAL SOUND
Dynamic range refers to how well a unit reproduces every level of playing from very soft to very loud-- without compressing or limiting the very loudest notes. I think the B2 Four does pretty well with dynamics, some preamps & amps will squish/limit more than others.
Most of the factory patches celebrate cabinet resonances from around 40 Hz to maybe 120Hz. It's a hump in the low or low-mid range. Fortunately, we can remove or reduce this hump either with preamp EQ, amp EQ, or an EQ module.
I didn't notice any latency; except with some pitch fx.
Depending on what is in the chain, there can be varying amounts of noise. Usually the Zoom Noise Reduction (which is excellent) takes care of it.
I was playing with a env filter, and noticed the output was clipping; so I put a compressor after the filter, and it cleaned up. This implies that there is plenty of headroom within the module path, but you have to make sure to get it down to a reasonable level by the time it reaches the output stage.
THE FX
The compressors sound good. Most are snappy enough for slap. Good range of adjustments and nice variety of options. They have much better quality and response than those on the B1 Four.
The Slow Attack module is disappointing. Each note starts from zero and ramps up -- which is unnatural sounding. I was hoping to use this for an "arco" (bowed) effect, no luck. If there was a dry level, then a dry attack and decay could be enhanced by a natural swell. That would be ideal.
Many of the envelope followers are too sensitive, even with the sensitivity all the way down. I often don't want the filter open all the way even when I play loud. Auto Filter is a welcome exception.
The Envelope Generator filter snaps to a 2nd frequencies when the foot switch is pressed, then immediately begins gliding back to 1st frequency at the set "speed" (regardless of holding the switch).
With the Zoom NR, we can put it anywhere in our path, and set it to either detect signal from the EFXIN (whatever signal is preset at that point in the chain) or GTRIN (which is like side-chaining the dry input signal). I usually choose GTRIN.
The Drive FX all seem to have a similar character.
The preamps have useful EQ and drive options.
I love all the modulation modules; EXCEPT for Tremolo which is very limited. The triangle waveform is ok. The TUBE and SQUARE are both clicky, and none of them sound like a proper tremolo. I've heard much better tremolos, even from Zoom.
Most of the pitch-shifters are barely useable. The bass polyphonic is ok for octaves. Harmony, Bass Mono Pitch Shift, and Pitch Shift are cartoonishly unusable. The other octavers seem ok, but fall apart on lower notes.
The Bass Talk Synth is too bright & edgy, and the tone knob doesn't begin to tame it, so it needs some filter/EG after. The Z Synth and Bass Synth are both great.
The delays are fine.
The reverbs are just ok. Not good enough to "feature" them.
The Air module is actually quite a nice stereo-izer when the values are cranked. When summed to mono, it sounds like a small room (but still good).
The fretless is subtle and cool. I wish it had a dry level. Combined the flip-top, we might get fairly close to an upright pizz character.
The amps seem good. Some tend to be woofy and humpy in the lows; and the hump can't be tamed with the amp's EQ controls. Thankfully, an EQ or preamp can flatten it, if needed.
PATCHES
The patches don't show off a ton of range or versatility. But they focus on usable tones. There are varying degrees of drive, lots of clean tones with hyped lows or low mids. The env filters are all too wide open. Makes me wonder if they were made with/for low output basses?
Fortunately any and all patches can be tweaked and over-written in their same ID number. If we ever want the original factory patch back, that's easily done.
USEABILITY
FUN FACT: when we are in the FX Library (choosing a module with arrows), we are auditioning the modules by themselves in isolation from what is in the rest our chain; and we can adjust knobs while in the library, so we can adjust before choosing.
In the editor, when we turn a knob the values appear, then vanish after 3 seconds. Frustrating. I understand why it is this way, but I don't like it.
It woudl be better if Zoom added a preference setting for
Knob Display Dwell Time:
3 seconds
5 seconds
10 seconds
BUTTON EXIT (pressing the center button exits the knob-value display)
Better yet, Zoom could just use the screen real-estate differently Put the patch #/name and slot dots on top of the screen, same size, and rework the module graphics. This way knobs could just be always visible for the currently selected module.
APP
I installed the app before I bought the unit, to see if I could learn stuff just from the app, but it has no "off-line" mode, so no dice. Once my unit arrived, connecting the unit was easy enough. BTW, I have no qualms about buying the app for $1.
There are three sections:
The Effect Pool shows a full list of available FX modules (FX, amps). I don't know if Zoom will put new FX there as they become available, but for now it is a list of all of the built-in modules with descriptions. From here we can remove some FX from our unit, or put them back. This could reduce unwanted clutter in the FX Library on the unit.
The Patch Pool is empty until we load some patches into it. As far as I can tell, we cannot remove patches from the Patch Pool.
In the News Feed, there is an option to download the factory patches which puts them in our Patch Pool.
The Editor is nice because it doesn't do the disappearing knobs trick. To change/add an FX module, choose "Change". Then tap a slot or module. It helps to think of "blank" as a pass-thru module. Enable/bypass via the square above each module. Re-order by tapping/holding on a module then drag.
SUMMARY
I have no regrets about this purchase. I knew I'd be getting good basic FX and signal path. It will serve the purpose I intended.
Pros: Versatile, flexible, uncomplicated. Many good and useable FX modules. 300 slots.
Cons: No patch level setting. Slow Attack module lacks dry level. Env Filters have poor sensitivity range. Knob display awkward. Tremolo needs reworked. Most pitch shifters weak. Cursor buttons awkward for foot. Reverbs mediocre. Routing limitations. DI models prevent stereo operation.
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