AER's Acousticube has been at the pinnacle of acoustic instrument amps since 1992. Does the latest revision live up to the legacy?
Specialised amplifiers for acoustic instruments seem to fall broadly into two factions: those that are designed primarily to mitigate the known defects of the most common pickup types, by imposing a character of their own, and those that assume you're using a high–quality pickup system that you would like to hear amplified as faithfully as possible. The line between products in the latter group and PA systems really is a fine one, with perhaps only the need for a wider range of input matching in the instrument amp differentiating the two. German company AER (Audio Electric Research) definitely make amps that fall into the 'virtual PA' category, with their acclaimed flagship Acousticube series having carved out an enviable reputation for itself as the benchmark product in its field for several years now. As an owner and very happy long–term user of an Acousticube IIa, I was pleased to be able to check out the latest Acousticube 3 model, complete with a new speaker design, new preamp configuration and a USB connection allowing reprogramming and organisation of the on–board 32–bit digital effects processor.
Measuring just 13 inches square by 10.4 inches deep, the Acousticube is amongst the smallest acoustic instrument amps on the market, but this certainly doesn't seem to compromise its performance in its intended applications. The cabinet houses a single Hexacone–based eight–inch driver with Neodymium magnet and a concentric one–inch dome tweeter. Hexacone is a composite material based on Kevlar, which allows the cone to be both stiffer and lighter than conventional paper or polymer cones, giving less cone break–up and an overall faster response, for a tight low–end and smoother mid–range. Only a small port on the rear panel identifies this as a bass–reflex design.
The 120W RMS power amp resides at the rear of the box, with the preamp sub–chassis slotted in the top. A ribbon cable joins the two, lying exposed on the surface of the back panel for a couple of inches, creating what seems like an unnecessary vulnerability in an otherwise pretty bullet–proof design. At a little over 28 pounds, the Acousticube is an easy one–handed carry via the side–mounted, recessed handle, or the twin webbing handles of the impressively padded gig bag provided with the amp. The open–cell acoustic foam that covers the speaker actually conceals a steel mesh grille underneath, so there should be no danger of accidental damage in that area.
Where previous Acousticube models have offered, effectively, a dedicated instrument channel and a microphone channel, the preamp is now configured with two apparently identical channels, each with a three–pole quarter–inch jack input on the front and all input–selection options available to both. A balanced XLR mic input is still available, but it is now on the back panel, and although both channels have a Mic input setting, only Channel two can in fact access the XLR. Channel one's Mic setting seems to switch its quarter–inch jack to mic sensitivity. The additional flexibility that the two almost identical channels confers will, I'm sure, be welcomed by most users, particularly for working with dual–source pickup systems.
The jack inputs can each be cycled around four modes, optimising the connection for passive piezo pickups, which require a very high input impedance; line input; mic input; and 'E/P' — an electret mic and piezo combination, with pickup on the tip and mic on the ring circuit. Phantom power at 9V can be activated on the line input and mic/pickup combo, and at 48V on the mic input, by holding in the Mode selector switch for three seconds. The huge disparity in sensitivity between some of the modes makes it all too possible to give yourself a nasty surprise when you inadvertently cycle back from the last one to the first — the most sensitive of all — unless, that is, you actually follow the advice in the manual about making all connections and settings with the master volume control well down!
Preamp mode and phantom status can be seen at all times, thanks to a row of multi–coloured LEDs, and a 15dB pad can be inserted to optimise gain range with exceptionally hot signals, although I didn't find anything at all that required it amongst my extensive arsenal of pickup systems, and I rarely provoked the Clip LED into action once the gain setting was optimised. There's a lot of headroom on these inputs.
The one area of the earlier Acousticubes that invariably came in for criticism was the lack of any facility to edit the effects programs. Even if you were quite happy with the programs themselves, you would usually want different mix settings for, say, a reverb, at maybe 15 percent effect, and perhaps a chorus effect where you would probably need a 50/50 balance. Even this most basic requirement was beyond the scope of the Acousticube's single Return level control, often rather undermining the benefit of having two memory locations at all.
At the back of the new Acousticube 3, however, lurks a USB connector that finally lets us get in there and tweak. A software editor program is supplied on CD-ROM (PC-only at present, although a Mac version will allegedly be coming soon), complete with a conveniently lengthy USB cable. The editor's graphical front-end lets you design your own effects program by selecting and arranging modules within a block diagram and then send the preset to the Acousticube. Double-clicking a module opens a detailed view, where you can tweak the available parameters. It is advisable to save the preset locally before sending, so you can perform further edits, as you can't get a program from the Acousticube into the editor. The software editor includes the complete factory set, though, so you've got a starting point for every existing preset. Once you've sent a preset to the editor, the parameters for that preset are all live and can be tweaked in real time, with immediate audible result.
It's not the most elegant software editor I've ever used; parts of it are still in German, even when you select English as the language, and its use of separate Mixer objects, rather than having a wet/dry mix parameter within the effects blocks themselves, does little for the visual clarity of the interface. But this is only version 1.0 and I'm just pleased to have it at all, especially once I discovered that it would run perfectly happily on a Mac under Virtual PC!
It seems to be possible to randomly lose the connection to the amp, whilst the software still shows it as connected — you only find out when it tells you it can't send a preset — but restarting the application and activating the 'Connect to amp' routine got things back on track every time, so it's not too much of a headache in practice.
I suspect that many users will remain content to never delve into the inner workings of their effects processor, but, like so many of the Acousticube's extensive facilities, it's nice to know that it's there for when you need it.
A Mute switch is a welcome new addition to the preamp section, allowing silent instrument changes on stage, and the useful 'Colour' voicing switch of the earlier models now features on both inputs. This offers a preset EQ curve, simultaneously dipping the mid–range and lifting the top end, giving a sparkle and transparency that particularly suits finger–picking and lighter playing styles. I find the Colour switch well–voiced for taking excessive mid–range out of magnetic pickups, or sweetening an aggressive–sounding under–saddle pickup.
The preamp stages all seem subjectively a little quieter than the IIa — the IIa is itself a very quiet amplifier— and activating the Colour switch now raises the hiss level barely at all, unless you have a noisy source connected. A three–band EQ completes the channel facilities. Channel one's frequencies are Bass, 60Hz (+/–10dB); Mid, 600Hz (+/–6dB); and Treble, 13kHz (+/–13dB). This is a rather different configuration to most instrument amplifiers, working mainly at the two extremes of the spectrum, with a low–Q soft slope and limited gain range in the mid band. Channel two's EQ is subtly different, with more conventional turnover frequencies at top and bottom (100Hz and 10kHz) and a much wider mid–range gain (+/–12dB at 1kHz). If your pickup needs radical surgery, neither of these EQs alone will do it. It would be better to get an outboard EQ/preamp with a sweep mid designed for the purpose and use the AER's EQ for what it does best: adjusting the amp's overall tonal response to different rooms, without producing anything too peaky or coloured that might provoke earlier onset of feedback. To further help combat the latter, there is a notch filter — still located at the back, as on the IIa, and still not sweepable. Being an analogue filter, it offers nothing like the pinpoint notching we have become used to with digital anti–feedback processors. A notch that is 24dB down at 120Hz, recovering to –12dB by 36Hz, makes a sizeable hole in the bottom end of most guitars — so much so that I have only ever found myself using it with naturally boomy big–bodied instruments or in particularly adverse monitoring conditions. Even then, I always put back a little bottom end with the Bass control, to avoid over–thinning the sound.
One further tonal adjustment is available in the form of the Presence control, again located on the rear panel. The documentation implies that this is for fine–tuning the response of the tweeter, affecting frequencies above 4kHz, but I have never felt the need to set it anywhere other than maximum. Still, it's good to know it's there.
The Acousticube 3 has sprouted a new Pre-Master control, alongside the main master volume, governing the Left and Right line–level outputs and dedicated recording outputs independently of the main master volume settings, adding still more flexibility to this range's legendary interconnectivity.
The on–board 32–bit digital effects processor has a very simple three–control interface: a continuous rotary encoder for program selection; return level; and pan to assign the effect between the two channels. A comprehensive selection of treatments is offered, ranging from different sizes of dark, bright and soft rooms, halls, churches and cathedrals to ambiences, unusual spaces such as corridors, a swimming pool and a railway station, and assorted choruses, flanges and delays. A lot of subtle variations are offered on the same basic themes within the 100 programs.
Bass Reflex: A cabinet design with a small opening, or 'port' that allows some of the sound from the rear of the loudspeaker to escape from the enclosure in phase with the signal from the front of the speaker, thereby enhancing bass response.
Cone Break-up: An ideal loudspeaker cone acts as a piston, increasing and decreasing air pressure over its entire surface area, but the designer always has to strike a balance between stiffness and a light enough weight to respond at high frequencies. When a cone receives too much level it first bends and then 'breaks up', in that part of it can be moving in one direction, while the rest is moving the other way, producing modes of distortion not harmonically related to the input signal, and an audibly unpleasant result.
Neodymium Magnet: Very high strength 'rare–earth' magnet type made out of neodymium, iron and boron. Its use in a loudspeaker allows the coil attached to the diaphragm to be made smaller and therefore lighter, thereby increasing efficiency.
Phantom Power: Standardised scheme of providing an invisible (hence 'phantom') power supply voltage using the same cable as the balanced audio output.
RMS (Root Mean Square): A calculation (using the square root of the average of the squares of a group of numbers) for obtaining the effective average voltage or current of an AC signal. Assuming the source is a sine wave, the rms value will be 0.707 times the peak value, or 0.354 times the peak-to-peak value (from full negative to full positive).
Acousticubes have always been renowned for their comprehensive connectivity, yet the latest version has still managed to add some more, with the addition of a pair of phonos for connecting a CD player or other –10dBV line–level source. A level control allows you to balance this source independently of the main signal paths. Although the Acousticube itself is mono, the aux signal, like the on–board effects, is sent to the left and right line outputs and the phones output in full stereo.
A master insert point has also been added (while retaining the Effect 2 send and return loop). This appears on a stereo jack (tip send, ring return), allowing for the insertion of a permanent master effect such as a compressor, limiter or EQ, without having to tie up the footswitchable Effect 2 circuit. I must admit that this was one of my few frustrations with the IIa configuration and it's great to see it solved in the latest model.
Two sets of line–level outputs are provided: Left and Right line outputs for connecting to active extension cabs or a PA system; and two Recording outputs, which allow you to access the separate signals of channels one and two, with their EQ, but without effects and independent of the master level setting. The Left/Right line outputs include anything patched into the Effect 2 return circuit, but not the internal effects unit, with the front–panel Pre–Master control determining the level independently of the master monitoring level. There's also a separate mono Line output which both tracks the Master volume and includes the on–board effect signal, for expanding your rig with another amp (AER would probably like you to use their CX8 powered extension).
An electronically balanced XLR forms the main DI output for connection to a PA. DI level is independently adjustable (via a rather too small pot shaft on the back), and the signal can also be switched between dry with no EQ, or post–EQ and with the internal effect signal.
The Effect 2 circuit allows the connection of an external effect in addition to the on–board processor, with both being controllable from the supplied footswitch. The return is in stereo, which is retained in the line outputs (and headphones), though not, of course, in the main amp, which is mono. The send is switchable between series and parallel operation, allowing you to set the mix locally, using the Return level control, and also keep at least half your signal entirely in the analogue domain if you are not entirely convinced about the integrity of your effects unit's A–D converters. A Pan control determines whether the send to Effect 2 is sourced from channel one, two or both.
Staying with the theme of signal integrity for a moment, the presence of a dedicated Tuner output allows you to keep a tuner permanently in circuit without having to have it in the primary signal path. Helpfully, the line–level output is independent of all level controls except the input gain setting.
A dedicated line–level sub–woofer output is slightly unusual in this type of amplifier. This one is optimised for connection to AER's active auxiliary bass–box, the Sub12/400A, and automatically engages a high–pass filter to relieve the Acousticube's own speaker of everything below 200Hz. The signal includes tone controls and effects and follows the master volume. The comprehensive connection facilities are completed by the stereo phones output, which cuts out the internal speaker, the eight–pin DIN master control socket and the newly added USB connection (see 'Editing Effects Via USB' box).
An eight-pin DIN cable connects to the supplied Acousticube two-button footswitch, allowing remote selection between the two user-stored effects in the memory one and two slots. Effects are stored by dialling up the one you want on the amp's rotary encoder and simply pressing the pot in towards the chassis. While one footswitch toggles between programs, the other activates or deactivates either the internal effects processor, via a short tap, or the Effect 2 loop, via a longer press. Very clever, and far more intuitive to use than to describe!
The footswitch also features a couple of controller inputs giving access to a VCA in each channel. A simple 'shorting' footswitch will act as a channel mute here (although, cleverly, the tuner output stays active), or you can use a volume pedal. There's nothing in the documentation to suggest an optimum pot value, but my empirical messing about settled on 22k Log as the best combination of offering both a progressive taper and ensuring no loss of volume when the pot is fully turned up. The nearest off-the-shelf component is an Ernie Ball 25k 'line' pedal which worked well enough, although I felt that the usable range was too concentrated at the toe-end compared to using the same pedal in-line with the signal.
Both channels can be controlled together if only channel one's jack is connected, or separately, using two pedals. There's also a neat trick you can try when using an external processor in the Effect 2 circuit: if you return the effect only to channel two (using channel one as your primary signal), the VCA foot volume on channel two then acts as an independent effects level control.
The Acousticube 3 delivers everything that its predecessors have always offered, and then some, offering smooth, neutral sound that is every bit as at home with acoustic guitar, vocals, or even amplified upright bass. Power delivery seems more effortless than the IIa, for while there's still a speaker protection limiter in the system it now seems virtually impossible to trigger it with normal music signals. The overall response of the new speaker system seems better, too, the subjectively smoother sound being confirmed by a higher initial feedback threshold.
In my primary application, acoustic guitar amplification, the Acousticube 3 surpasses my IIa version in areas that I really hadn't expected, such as lower front–end noise and higher headroom, whilst retaining the same intrinsic quality of sound. Specific settings that worked with certain pickups on the IIa still work on the '3'; they just work a bit better. This is a remarkably versatile, high–quality amplifier, equally adept at filling a room on its own in a 'reinforced acoustic' context, or slotting into a larger rig as a performer's monitor feeding a FOH system. Despite the diminutive driver, there's a reasonable amount of volume on tap. I use mine with a small band line–up including drums and electric bass and never need to ask for any guitar in the monitor mixes. The single (actually dual–concentric) driver and narrow cabinet frontal dimension serve to create a very predictable and even spread, both vertically and horizontally, with none of the beaming effects of larger boxes or multi–driver systems. There are practical limits to how much level a single eight–inch driver can generate, however, and I wouldn't expect to be able to keep up with a less subtle drummer, or an electric guitar–based line–up, unless it was just with background strummy filler.
The on–board effects, with a few exceptions, are mostly the kind you can just dial–in as a sweetener and leave alone. I know some people criticise them as not radical — not 'effecty' — enough, but I think they have been well chosen as subtle enhancements rather than show–stealers. Of course, now you can 'roll your own' anyway, via the USB link and supplied software.
Granted, the Acousticube 3 is by no means cheap — there are perfectly respectable acoustic guitar amps on the market for a third of the cost of one of these — but high–quality components and engineering cost. With the release of the new version, at least there might now be a few IIa models on the second–hand market, as owners look to upgrade! Will I be upgrading? Now that I've heard the new model, yes. Will everyone want to upgrade? Probably not. The IIa is still a great acoustic amp, and unless you're perceiving limitations with it, why spend more money?
AER make a whole family of PA/acoustic instrument products, including a number of rather more affordable models such as the Compact 60 amplifier, but manufacturers tend to be judged on the performance of their flagship products, so, as a big fan of AER's 'quality is everything' company ethos, it's nice to be able to report that 'the best' just got even better.
- Excellent sound quality.
- Extremely compact.
- Rugged and well built.
- Comprehensive connectivity.
- Now with effects editing.
- Poor documentation for a premium product.
- No Mac version of the editor yet.
Quite rightly, the Acousticube is the benchmark product in its field.
£1495 including VAT.
Westside Distribution +44 (0)141 248 4812.