A big shout out of thanks to my long time friend Jonathan for the inspiration for this article.

Setting the Baseline

I think that we, or most of us, understand the concept behind an Impulse Response system. For electric players, IRs have always been about being able to record as if you were playing through a particular speaker and cabinet. This makes sense because we know that different speaker/cabinet combinations sound different and we might want to achieve a particular sound.

When it comes to acoustic guitars, the more serious buyer will select a guitar or guitars based on their acoustic sound. Amplifying these instruments was originally a challenge because it meant using a flat response microphone and then feeding that signal to a flat response amplification system. While this worked, there were some unwanted side effects like extraneous noise, potential for feedback and that a microphone locks the player into a specific position.

When pickups came to acoustic guitars, they were at first magnetic pickups derived from electric guitars. All good, but we know that different pickups deliver different tone and acoustic makers who spent their time to achieve a particular tone hated them. At the high end, this is still true about any pickup. Most all the higher end makers will tell the serious buyer that miking the guitar is still optimal. However, this is not convenient and so we saw the proliferation of the piezo electric pickup. The physics of piezo electric effects is fascinating but the sound is pretty uniformly high biased, missing lows a subsonics and has a nasal quality. Some people, including myself, find the sound of a direct piezo like being stabbed in the ear drum.

Some manufacturers that use piezo electric pickups, and I will use Taylor Guitars as an example, were not happy with what the piezos were delivering directly. So they invested in a preamp system to go with the piezo pickup to address the inadequacies of the piezo electric pickup. If you have an acoustic with a pickup that needs a battery, there is some kind of preamp in there, but in most cases, it is only a signal booster. Taylor is different as an example because their Expression System preamp not only boosts, it also equalizes the signal to deliver what Taylor believes is the sound of the guitar itself. If one is going to buy a guitar with a built in pickup, the Taylor Expression System is in my opinion, the best commercial outcome.

For guitars that don’t have a pickup, I prefer the condenser contact system of the K&K Pure Mini, but even how excellent it is, engineers and producers will still advocate for a preamp for live play and a channel strip when recording. I agree completely.

Up to this point, I have been talking about reproducing the sound of the guitar when plugged in. A PA system or excellent acoustic amplifier has a flat frequency response as the sound leaves the speaker cabinet. Once the sound is in the room, the acoustics of the room start to impact the sound. An acoustically bad room will destroy all the hard work that comes before.

Thus the presumption is that if an Impulse Response file is created to apply changes to the amplified signal to emulate a specific room, it will bring back the real sound of the guitar if the acoustics of the room are bad.

Nope. Never going to work because the final acoustics of the room will override whatever you send it.

Could an IR pedal in this case be used in recording? Certainly. However studio professionals are more inclined to use good studio space rather than try to fake out another location. So, you may ask, what’s the point of these pedals?

Let’s Find Out

So I did what I always do. Research.

My first discovery following a number of searches was that there were not any IR pedals that said that they provided room IRs. There are videos on YouTube where some pedals are identified as doing this. Without getting into naming and shaming, the content creator is in error. The pedals referenced do not provide room simulation, they provide speaker and cabinet emulation. Some provide the emulation of a full range flat response system, what you will already get in a PA or superior acoustic amplifier, so no point to that. The rest of the IRs are for guitar and bass speakers and cabinets, and any acoustic player with some experience knows that acoustic guitars sound like shit through traditional electric guitar or bass amplifiers. You could use a computational audio system like a Spark or a Katana and get a decent acoustic sound because the speakers in these devices are effectively FRFRs that put out a digitally altered signal. That works great.

However, it does not address the issue of the effect of the room where you are playing. The room acoustics will matter. Anyone who has attended a concert by the same performers done in a concert hall vs a sports arena will tell you that there is a massive difference in sound. Concert halls are designed for music. Arenas are not. This is why arena concerts always have one or more sound engineers set about halfway back on the floor, not just to manage volume levels but to use equalization tools to correct for the acoustics of the arena. This is not a trivial skill, and in practical terms it takes time to build competence in this space. All too often a good band or performer will have their performance destroyed by not having a capable sound engineer controlling what comes out of the speaker systems.

What does this mean to the acoustic player who wants great sound from his or her instrument when it is amplified but who does not have the luxury of a dedicated sound person? The answer is actually pretty simple. It is an EQ pedal. There are pedals, like the very nice TC Electronic BodyRez that strives to bring the sound of a guitar back when a general piezo is used, however to do that AND to adjust for room acoustics a simple multi-band EQ pedal is a better option. Best of course is a pedal that does EQ, compression and also includes a high quality preamp with a DI out direct to the PA’s low impedance inputs. This is my recommendation all the time, even if your acoustic pickup system includes a preamp, and even if it is a good preamp like the Taylor system.

Recommended Acoustic Preamp/EQ Pedals

Budget will always come into play, and if you are playing in a small coffee house and not getting good compensation, you may not be financially comfortable with a good pedal. But if you have paid over $1000 for your acoustic guitar, do consider this option because it will serve you for both playing live and for recording, even if you only record at home.

I recommend consideration of the following. I add what I consider the pros and cons for each. You should get to a real guitar shop and audition them to make the purchase that is right for you. if I don’t mention a pedal, it does not mean that I don’t know about it, and in truth, I may not but I also just leave out things I don’t recommend rather than throw mud at them.

Radial Amplification Tonebone PZ-Pre - About $410 USD

Pros

• Acoustic specific preamplifier

• 2 separate channels, supporting two instruments

• Works by design with orchestral instruments in addition to guitars

• DI out

• Acoustic specific equalization including notch filter

• Built in clean boost

• Built in looper

• Effects loop

• Tuner send

Cons

• No Compressor

Tech 21 Acoustic Fly Rig - About $250 USD

Pros

• Acoustic specific preamplifier

• DI out

• Acoustic specific equalization including notch filter

• Built in clean boost

• Built in simple delay and reverb

• Built in tuner

Cons

• Control knobs are very small

LR Baggs Venue DI Acoustic Guitar Preamp / DI / EQ / Tuner Pedal - About $330 USD

Pros

• Acoustic specific preamplifier

• DI out

• Acoustic specific equalization including notch filter

• Built in clean boost

• Built in tuner

• Built in Effects loop

Cons

• No Compressor

Wrapping Up

At first glance you would say that the Tech 21 is the best option at the lowest price. I own one and have used it for years. It is a really fine product, but you came here for honesty knowing that I am not compensated in any way by anyone. Of the three recommended, the preamp is the weakest in the Tech 21 in my view. i think that the preamps in the other two are quite comparable. The big difference in the Radial unit is its construction in addition to its superb audio response. The darn thing is tough. There is no plastic anywhere and while you could kill one, it would be work to do so.

Folks will notice the lack of anything from Fishman. Yes I don’t recommend the products, but if you have questions about a specific Fishman product, I can in high probability answer you. You will note that when a device does not have a built in compressor, I note that as a con, because I believe that a compressor is a requirement for great acoustic guitar sound because of how the transients attack and the rapid fall off in sustain. I never recommend a squishy compressor for anything and for acoustic instruments I recommend a compressor that is very fast with control over attack, release, compression and make up gain. Save yourself time and money and just buy the Universal Audio 1176 Compressor Pedal, about $180 USD. It is effectively a studio rack 1176 compressor in a foot pedal, and it’s perfect for ANY acoustic instrument.

The links in this article take you to Sweetwater in the US. I am not a Sweetwater affiliate, but they did help sort the wheat from the chaff when it comes to the erroneous bafflegab of Acoustic IR Pedals. If you are not in the US, check your local guitar shop as these products are available internationally.

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