Acoustic Image FAQ Page (originally published at Acoustic Image's website)
FAQ Page originally hosted at AcousticIMG.com
Acoustic Image closed its doors in 2023 after the sudden passing of the president and founder, Rick Jones. We sold many, many Acoustic Image amplifiers, speakers, combos, and preamps over the years, so we want to continue to support them as best as we can. Rick had authored these FAQs and had them posted on their website - I've reproduced them here for your benefit, as I suspect that the Acoustic Image website at www.acousticimg.com will not remain online for long.
Most of these FAQs were written during the Series III and Series 4 models, and they don't directly refer to later products like the Doubleshot, Upshot, and upfiring Coda amp. Some of the information is still helpful, though.
My combo amp isn’t loud enough. Is there a solution?
The best way to increase volume for a Contra or Coda is by adding an Contra EX extension cabinet. By lowering combined resistance to 2 ohms you get the highest rated wattage from the amplifier. And, by increasing speaker area, you move a lot more air. One of our combos with extension speaker will play very loud (and clean). At the same time, they aren’t designed for heavy metal. In designing a small, highly portable, full-range, high fidelity amplifier system the major tradeoff is extreme volume capability.
I have a piezo pickup on my instrument. Which input should I use, high or low Z?
That depends. For most piezos, the low Z input gets best results. In particular, The Realist pickup for upright bass seems (like magnetic pickups) to be happiest with the Low Z. Both inputs have equal gain through the amp, but in general, the high Z input tends to increase the relative prominence of bass over treble. But don’t be afraid to experiment. You won’t do any harm. And what sounds best to you, on your instrument, is what counts.
When should I use the tilt mechanism on my combo amp?
There is no hard and fast rule. It’s a function of the room, the stage, the music, the sound of your instrument, and your sonic preferences. Generally speaking, the tilt mechanism (along with EQing bass and midrange) will help to reduce room-effect “boominess” in your sound. It can also make it easier for you to hear your intonation by aiming the midrange speaker at ear level. As with most things, we advise you to experiment to find out what works best in each situation.
I am getting “boomy” sound, even with the tilt mechanism in place. What do I do?
If your amp has a notch/high pass filter, try adjusting it to remove low frequency boominess. If necessary, you can also lift the amp onto a table or chair, as long as it’s in a stable position. Physics dictates that you will get the most bass from your cabinet when it is resting on the ground—and more still if it is backed into a corner.
The sound on my bass seems “muddy”. What’s up?
Chances are there is too much bass dialed in. Adjust the EQ. As a starting point, turn the bass and mid-range controls to 9 o’clock.
How does the downfiring woofer work on carpet versus a hardwood floor?
The frequencies coming from the downfiring woofer are, in general, not affected by the surface on which the amp is sitting. Carpet reflects bass and mid bass frequencies just like a hardwood floor, unless the carpet is extremely thick. The sound of the combo is more affected by the room acoustics than the floor surface. A room with a carpeted floor generally has other acoustically absorbent materials in the room so it sounds dead compared to the live sound of a room with a hardwood floor that has other reflecting surfaces. So, it only seems that the floor surface has an impact on the sound when, in reality, it is the room.
My integrated amp came with a cable with twist-lock connectors at both ends. My non-AI speaker cabinet only has quarter inch inputs. Am I stuck?
No. At most music stories you can buy quarter-inch to twist-lock adaptors or a cable with a quarter-inch plug on one end and a twist-lock adaptor on the other. Twist-lock connectors are more secure than phone plugs and transfer electrical energy (and sound) more efficiently.
How do I overdrive my AI amplifier?
Basically, you don’t. Our amps were not designed to generate distortion. If you want an “overdriven” sound, we suggest that you insert a pedal or other external device into the effects loop.
Can I operate my AI amplifier without a connected loudspeaker?
Yes, but you should turn the master volume to zero (all the way counterclockwise). In some of our products built more than a few years ago, you can do damage to the amplifier when attempting to connect speakers while the amp is “on”. Even if your amp doesn’t carry that warning label, we recommend that you plug in speaker cables when your amp is “off”, to be on the safe side of caution.
Is my Series II Focus capable of driving 2-ohm speaker loads?
While it isn’t rated at 2 ohms, it will handle the load in most cases, as long as the volume isn’t cranked to extreme levels. Give it a try. If the amp isn’t up to the task, an internal protection device will shut things down momentarily… however you won’t do any harm.
How do I connect my Focus SA to my Focus or Clarus head?
You connect the send output or the direct out of the Focus or Clarus head to the input of the Focus SA. Do not connect the speaker output of the head to the SA, otherwise damage will occur to both amps.
Why don’t you have a bass amp, a guitar amp or a keyboard amp?
Our amps are designed to be high fidelity reproducers of the instruments they are amplifying. In that sense, they are like a PA system. They are not designed or voiced for specific instruments, but are designed to reproduce the full frequency spectrum. So our amps can reproduce bass as well as piano as well as voice. Because the early users of our products were bass players, we got the reputation of being a “bass amp company.” But, when the bass player let the keyboard player or guitar player or vocalist use his amp, the other musicians quickly found out how great the amps sound with all instruments.
What instruments are your amps good for? Which amp should I choose for my instrument?
Our amps are designed for all instruments and they work much like a PA system in reproducing the full spectrum of sound. So, you should choose the amp or combo based on the features it has — as they relate to your instrument. Some examples. An acoustic bass player uses a single piezo pickup on his/her bass and wants the smallest rig possible. The best choice in this case would be the Contra combo since no features other than the single channel with no effects (and light weight) are needed. An electric bass player wants a small rig but needs high power for rock and blues gigs. A Clarus+ used with a higher output speaker system such as a 2x10 or 4x10 would be a good choice in this case. A Ten2 combo may also work in this situation. A guitar player sings and plays acoustic guitar. The Coda+ combo would be a good choice because it allows the guitar and voice to be mixed and it has effects such as reverb which can be used on either the guitar or voice, or both. The Corus+ or Ten2 would also be a good choice. An archtop guitar player wants the classic jazz sound (a more forward sound with boosted midrange), so our cabinets (with natural, flat-across-the-spectrum sound) are unsuitable. A Clarus+ with a guitar-oriented cabinet would be one choice. The Corus+ or Ten2 combos would also be a good choice. A violin player wants to mix a mic and pickup to get the best amplified sound possible. The Coda+, Corus+ or Ten2 would all be the good choices for this application. You should give each a try to see which one you like best. Hopefully, these examples will help you to choose the right amp. If you have questions, feel free to call us. We will be happy to help you.
Why is your cabinet cylindrical?
One of the biggest problems with speaker cabinets is the fact that the panels of the typical square cabinet vibrate and add unwanted sounds to the output of the amp. The result is that the amp will lose focus and not sound as defined. A cylinder is inherently stiff and does not vibrate like the panel of a typical speaker cabinet, which means our cabinets have better definition and more focus.
Why are your amps so light?
Design techniques make our amps lighter. For example, switch mode power supplies eliminate heavy power transformers and reduce weight considerably. This type of power supply has been used in the computer and telecom industries so they are proven and reliable. There is no compromise in the performance or reliability of our amps. We also use cool-running switch mode power amps that eliminate fans and heavy heat sinks to reduce weight. Finally, our cylindrical speaker cabinets are inherently stiff and can be made from thinner and lighter materials, again reducing weight.
How do you rate your amps? Are they really as powerful as you say?
Our power ratings are RMS continuous sine wave and our ratings apply over the full frequency spectrum. Our amps deliver their full rated power at 20 Hz (low frequencies are where the most power is needed), something that most musical instrument amps won’t do. We also test our amps with a 40% duty cycle burst mode sine wave signal. This signal is more like a music signal than the continuous sine so this test tells us how much headroom our amps have with music signals. Typically the burst mode power is 25 to 30% higher indicating that there is lots of headroom in our amps.
Can I use your amps with a 16 ohm speaker? What happens if I connect an 8 ohm speaker and a 4 ohm speaker at the same time?
Because our amps are solid state amps, they automatically adjust for any impedance load. But, as you can see from our ratings, the power output depends on the impedance. The power rating at 16 ohms will be about half of the 8 ohm rating. You can mix cabinets of different impedance ratings. Just be sure that the overall impedance is at or above the 2 ohm rating of the amps. If you mix impedances like combining 4 ohm and 8 ohm cabinets, more power will flow to the lower impedance cabinet so you may have an imbalance in output and sound quality. If in doubt, try it and see how it sounds.
Why do you only use Speakon connectors on your amps?
Using a 1/4-inch plug and jack for speaker connections has a couple of significant problems.
First, that type of connection can’t handle the high current that modern power amps can put out. The best 1/4-inch connectors can handle only 15 amps and average ones handle only 6 amps before their resistance properties change. With high current, the resistance of the connection goes up which results in a degradation in bass response in the speaker. In contrast, a Speakon connector can handle up to 40 amps. Our amps can put out as much as 40 amps of peak current (that’s over 3000 watts peak into 2 ohms!).
Secondly, a 1/4-inch plug exposes the amp output to potential shorts and damage if the amp is on while the speaker cable is unplugged. (It’s always a good idea to turn the amp off before plugging or unplugging the speaker cable.) And, when a 1/4-inch plug is inserted in the jack, there is a momentary short that occurs between tip and sleeve which means that the amp’s output is shorted whenever a speaker is connected or disconnected when the amp is on. The Speakon connector does not have its terminals exposed when it is unplugged and there is no momentary short when connectinh or disconnecting.
Why does my old combo amp sound louder than my AI combo but doesn’t sound as natural?
The loudness of a speaker system is a function of the efficiency of the speaker and the volume of air it moves (which, in turn, is related to the diameter of the speaker). The typical musical instrument combo amp uses a high efficiency, large diameter (12 inches or higher) speaker. Our combos use a lower efficiency, smaller diameter speaker (10 inches) which results in a lower output level at a given input level. So, our combos aren’t as loud as the typical bass or guitar combo.
There are a couple of reasons why we took this approach. First, there is a trade-off between speaker efficiency and fidelity of low bass sound: high efficiency speakers typically don’t have very good bass response, especially in small speaker cabinets. Because good low frequency response is crucial to accurately reproducing the sound of an acoustic bass and the lower octaves of a keyboard, we opted for good low frequency response over efficiency. Secondly, large speakers tend to be slower than smaller speakers in responding to transient signals (such as the “ping” of a plucked string) which can result in a loss of transparency. We opted for a small speaker in order to get the best transient response and thus a clearer, more focused sound.
In short, we designed our combos for higher fidelity at the expense of efficiency, so they sound better and more accurate than the typical combo. We make up for the lower efficiency by using higher power in the amp portion of the combo, something that we can do while maintaining small size and low weight because of the unique nature of our amp designs.
If something goes wrong with my amp or combo, can I fix it myself?
In some cases. Here are some examples of situation where you may be able to do just that, or at least find out more precisely what the problem is:
If there is no sound and no green light, there is a problem (at least) with the external fuse. These normally don’t blow for no reason, but it does happen. Make sure that the voltage selection switch is in the proper position (115V or 230V). Operating the amp at 230V input with the switch in the 115V position can cause the fuse to blow. The fuse also can become loose in its holder. So, as a first step, reinstall and/or replace the external fuse.
If there is no sound but the green light is on, (and you have tried another instrument cable and another speaker cable), the first step is to isolate the problem between the preamp, the power amp and the speaker. First connect the direct out or send jacks of your AI amp to the input jack (NOT an external speaker or other output jack) of another power amp. If you get sound, the problem is not in the preamp… if you don’t, first try another speaker cable. If that doesn’t work, disconnect the internal speaker (or whatever speaker have been using) and connect the amp to another speaker. If you get sound, the fault is with the speaker, if you don’t, it is likely in the power amp.
If the sound is distorted and greatly reduced in volume, chances are an internal fuse is blown (SI and SII versions). If you are capable of doing it, unplug the amp, remove the cover and replace the fuse. This problem typically happens when the speaker output of the amp is plugged into the input or output of another amp. Only plug the speaker output of your amp into a speaker.
However, if there is a “ticking sound”, you likely have a blown output transistor. You will need to send the amp to AI for repair.
In all cases where you can’t get the amp to work or don’t feel confident trying without assistance, please call us. If we can’t help you fix things over the phone… or arrange to ship you a part for installation at home… we will give you clearance to ship the amp to us for a fast-turnaround fix.
What is Corus? What’s different about it?
Corus+ is, essentially, a Series III Coda+ combo with a different crossover and woofer selected to trade off bass extension below 60 Hz for greater volume and mid-range projection. The fundamental AI sound is unchanged, but Corus is optimized to achieve a sound many guitar players like — and have achieved until now by marrying a Clarus or Focus to a non-AI speaker cabinet. With Corus+, these same players have the sound they want, the on-the-gig convenience of a combo, and the ability to be heard more forcefully out-front as well as all over the bandstand.
Aren’t Contra and Coda a good fit with guitar? What about Clarus and Focus?
Contra and Coda+ are true full-range combos and we have many customers who love their sound with guitar. Also, we anticipate that many guitarists will continue to purchase our heads for use with other cabs. In both cases, it’s a matter of individual taste. However, we think Corus+ will be the best overall solution — in sound and portability — for most guitar players.