Compared to traditional speaker simulators, IRs offer much greater realism and depth.
I find the evolution of rock guitar tone to be a fascinating subject. A ā59 Fender Bassman cranked up through its internal 4x10ā speaker configuration sounds nothing like a Mesa Dual Rectifier through its oversized, closed-back 4x12ā cabinet with Celestion Vintage 30s. And the speakers and speaker cabinet are a huge part of the equationāif you were to run the Mesa Recto into the Bassman speakers, youād get a completely different tone, but one that leans in the classic Bassman direction.
The same thing goes for Vox tonesātry running almost any amp into an open back 2x12ā with Celestion Blues and youāll instantly see just how much of that classic Vox character is actually coming from the cabinet.
Itās not always easy to do this kind of research. A lot of these differences become more apparent at volume, and cranking tube amps is just not an option for many guitarists. Assembling a large speaker cabinet collection is even more impractical. But because of these factors, guitarists have long been using speaker simulation devices to simulate the characteristic sound of different cabinets. Devices such as the Palmer PDI-09 apply a filter or EQ curve that mimics the sound of a guitar speaker to the full range output coming off your amp speaker out. This processed signal can then be sent to a PA or recording setup. Devices like this can work well, but you are usually stuck with one or two preset EQ curves, and the filter doesnāt replicate many of the complex factors that come into play when micāing a speakerāthe thump of the cabinet, the airiness, or early reflections.
Recently, a whole new technology has surfaced called Impulse Responses (IRs). The first time I encountered Impulse Responses was in reading about Altiverb, the popular convolution reverb plug in. In lay terms, Altiverb gives you the power to sample any acoustic space you can think of, load it as an IR into the plug in, and voila, you have the characteristic reverb of say, the Sydney Opera House available to you in your DAW. But IRs are not just used for reverbs. You can effectively capture the sonic fingerprint of just about anything you can pass a sound through using IR technologyālike a micād speaker cabinet.
Compared to traditional speaker simulators, I find that IRs offer much greater realism and depth. When you apply an IR to a line out signal from your amp, you are not just applying a preset EQ curve to your ampās signal, you are essentially applying the distinct sonic characteristics of a certain speaker, cabinet, mic, mic preamp, and any early reflections that also make it into the mic during the recording process. There are libraries of IRs available to you at your fingertips, an almost endless variety of cabinet and micāing combinations. You can mix and match and blend virtual cabinets to your heartās content. And when you land on a sound you really like, itās easy to store that sound within your DAW, so you can call it up again later.
Of course, you canāt just plug a line out from your tube amp into your recording console or computer interface. Tube amps need to see a load (either a speaker or a dummy load of some sort). And youāll need a good DAW and a convolution plug in that allows you to load IRs as well. To help us get a handle on what IRs mean for us guitarists, and how we can use them both live and in the studio, Iāve asked Mike Grabinski from Red Wirez Impulse Responses a number of questions.
Thanks for being a part of this, Mike! First off, what is an impulse Response, and how can guitarists incorporate them into their rigs?
Technically, an Impulse Response, or IR for short, refers to a system's output when presented with a very short input signal called an impulse. Basically, you can send any device or chain of devices a specially crafted audio signal and the system will spit out a digital picture of its linear characteristics. For speaker cabs, that means frequency and phase response, phase cancellation between multiple speakers, edge reflections, and other audible signatures wrapped up in the gnarly, old pieces of wood, paper, and glue that guitarists find so endearing. IRs will not capture non-linear stuff like distortion and compression.
When you're capturing an IR from a speaker cab, by necessity you are also sampling your D/A converter, power amp, the mic, mic preamp, your A/D converter, the cables you're using, and the room you are in. Basically, everything that comes in contact with the impulse as it makes it round-trip from your DAW and back again. So, it's important to use high quality gear and have a good recording environment. There's really no cheating physics.
Once you've captured a speaker cabinet IR, you process the signal coming from your amp by convolving it with the IR, imprinting the signal with the sound of your speaker cabinet. There are quite a few plug-ins and a few devices these days that will do the convolution part.
What are the benefits of using impulse Responses versus traditional micāing of speaker cabinets? IRs give you access to gear and acoustic spaces that might be too expensive or otherwise unattainable. The ability to run totally silent can be a real plus, too. Especially when cranking even a 30-watt amp can make your ears bleed, your dog run for the hills, or make your neighbors call the SWAT team.
IRs are a boon in a live situation, as well. Because you are essentially going straight from your rig into the house system, a setup using IRs is mostly immune to bleed and feedback from other instruments. You have more control over your tone. You are no longer at the mercy of the overworked sound guy, who would probably love to spend 10 minutes finding just the right mic position, but just doesn't have the time. And because you are eliminating a lot of the variables from the process, you can more easily reproduce your tone from venue to venue.
In your opinion, how close does an impulse response come to replicating the tone and overall coloration that that the typical cabinet/mic/mic preamp chain creates?
Early on I did double blind tests to convince myself it was worth the effort and expense to sample all these cabs. When levels are matched and you are comparing an IR and a mic in exactly the same position it is very hard to hear any difference at all. With dynamic mics, at least, I can sometimes pick out the IR, because a mic like the SM57 exhibits some distortion and I know what to listen for, and more importantly I actually know one of them is a real mic and one is an IR. With condenser mics, which are generally more linear, they sound pretty much identical. If you gave someone a recording and didn't tell them you were using IRs, they would never know, or even think to ask.
What's the best way to get your guitar amp signal into an Impulse Response that's loaded up in a typical computer host?Well, if making noise is an option, the best way, in my opinion, is to tap your amp's speaker out with a DI that can handle the power and then pass the signal through to a real speaker. That way, you are capturing preamp and power tube distortion and your amp still gets a reactive load. You don't really care what the speaker sounds like because you are going to be using IRs for the tone. You can shove it in a closet in the basement and as long as it can move some air, it's shouldn't negatively impact the DI signal. Some amps have the DI function built into the amp. Some even tap the signal coming from the power tubes, so a separate DI is not always necessary.
If you have to run silent, then you need a dummy load to take the place of the speaker, otherwise you can damage your amp's output transformer. There are lots of attenuators that also function as dummy loads out there. It is important to understand that your tube amp will probably react differently to a dummy load and you may find that your tone is missing the low-end bump and upper-mid rise you are accustomed to when using a speaker.
There can be several reasons for this, but one major factor is that speakers do not present a uniform load to your amp. If you look at a typical guitar speaker's impedance curve, which is a plot of the speaker's impedance across the frequency spectrum, you will see a big low-end bump and a steady upper-mid rise. This can also be described as a midrange scoop, depending on your perspective.
The load, or impedance, measured in ohms, will differ based on the frequency of the your amp's output. Solid-state amps have low output impedance, so their power output is not jerked around very much by the speaker's varying load. Tube amps have relatively high output impedance and as a result they deliver more power as the impedance of the speaker rises. And for a typical guitar speaker, that means you hear more bass and upper-mids.
Because a lot of dummy loads and attenuators present a uniform load to the amp, your amp's output will remain constant across the frequency spectrum. If you're accustomed to a low-end bump and upper-mid rise, you will probably hear this as the dreaded attenuator tone suck. To alleviate tone suck, you can use EQ. An alternative would be to use the sampled impedance curve of a real speaker to adjust the highs and lows in an authentic way.
What equipment does a musician need in order to use Impulse Responses with amplifiers, both live and in the recording studio?
You need a load for your amp, either a speaker or dummy load and a DI capable of tapping the speaker out of your amp. You also need a means to convolve the IR with your amps' output. In the studio, you can use a convolution plug-in. There are quite a few, including our own mixIR2 (wink, wink, nudge, nudge).
Live, the options are fewer and generally more expensive because you need a reliable device with enough horsepower to do the convolution with minimal latency. Not an easy task on a stage.
Letās look at that for a minute. It's relatively easy to load an IR into a host on a computer in the studio, but what about boxes that allow you to do this easily live, in a road-worthy portable package? Say, with a built in load for your amp, and with multiple memory locations for IRs so you can load them up and take them to the gig? What's out there now, and do you see a market for more boxes like this down the road?
There aren't too many that I know of. There's the Fractal Audio Axe-Fx and Axe-Fx II, the Torpedo VB-101, and apparently you can load IRs into the Digitech GSP 1101 with some unofficial firmware mods. It is my understanding that the GSP 1101 truncates the IRs to 128 samples, which would limit your low and low-mid resolution. I suppose you could rig up a laptop, but I'm not sure how reliable and road-worthy that would be.
There seems to be increasing interest in these kinds of devices, so I'm sure more will pop up in the future.
Right. Also, we should mention, the Axe-FX and the GSP 1101 wonāt provide a load for a tube amp but they do work great as hosts for IRs. I use the Axe FX this way live. Anything else you'd like to share?
San Dimas High School Football rules!
[Updated 12/12/21]
- The Recording Guitarist: Impulse ControlāMastering Fake Spaces ... āŗ
- The Recording Guitarist: Speakers? We Don't Need No Stinking ... āŗ
- Amp Mic'ing vs. Impulse Responses - Premier Guitar āŗ
Wampler Pedals releases the Brent Mason signature ReWired pedal.
Brent Masonās career as a session guitarist spans over five decades, making him one of the most recorded musicians in history. His unparalleled talent has graced more than 1,000 albums, playing with and contributing to chart-topping hits from icons like Alan Jackson, Brooks & Dunn, Vince Gill, George Jones, Dolly Parton, Blake Shelton, Shania Twain, and many others. A Grammy winner and Musicians Hall of Fame inductee, Brent has also earned twelve Guitarist of the Year awards from the Academy of Country Music, two CMAĀ® Musician of the Year titles, and was named one of the top ten session guitarists ever by Guitar World magazine.
Brian Wamplerās journey with Brent Mason began way back around 2004, when heād make weekend trips to Nashville just to watch Brent play. Inspired by Brentās incredible talent and effortless touch, Brian set out to craft a signature pedal that would become the cornerstone of Brentās sound. The Overdrive channel perfectly captures Brentās iconic rhythm tones, offering everything from crystal-clear light dirt to a punchy, muscular Overdrive. The Distortion channel screams with rich harmonics, making it ideal for solos - whether used on its own or stacked with the Overdrive for maximum impact.
An Iconic Tone, Reimagined
With two fully independent circuits, the ReWired gives you access to both classic Overdrive and powerful Distortion channels that have been tweaked to Brentās exact specs. The Overdrive side is perfect for rhythm and Chicken Pickinā - built for warmth and maximum clarity, staying true to Brent's iconic sound. The Distortion channel is a perfect lead tone and offers a weighty āBritishā Plexi-like punch. The ReWired also features an order switch that allows the stacking direction to be changed on-the-fly without the hassle of changing cables.
Dual inputs and Outputs
The ReWired can be connected with a single mono input and output cable, just like a regular guitar pedal, or you can connect each channel independently (very useful when used with a loop switcher!). You can even connect a pedal in between both channels - try adding a compressor or an EQ if you want to sculpt your tone further.
Fat Blends
The ReWired incorporates our unique āFatā circuit control onto each channel as separate knobs. This allows you to dial in just the right amount of low end thump and presence into your rig - helping tame big speaker cabs or enhance smaller ones. The Overdrive channel also has Brentās signature blend control, allowing you to tune the amount of drive to your liking.
ReWired - for ALL players
This is not a guitar pedal to be bought and put in a case and admired - but with its exclusive new Prime Silver finish (a nod to Brentās infamous ā67 Telecaster) and custom graphics we wouldnāt blame you if you did. The Wampler ReWired is designed to be at the heart of your rig. It sounds great with every guitar and amp weāve tried it with and covers so many genres of music with ease. It comes with Wamplerās standard no fuss 5 Year guarantee and is built from the highest grade components to withstand the rigors of practice and gigging for years to come. The Wampler Brent Mason ReWired Signature Overdrive and Distortion - Rewire Your Sound Today Built in the U.S.A. with high-grade components selected for superior sound and response, premium finish and controls Dual Independent Overdrive and Distortion channels Independent Level, Gain, Tone and Fat controls for both channels, Blend Control for Overdrive channel Channel Order switch with two pairs of Input and Output jacks Power draw: 35mA at 9V and 40mA at 18V. 9-18v power jack - DC supply only, do not exceed 18v DC, battery Included Includes Limited 5-Year Warranty Dimensions: 5ā x 4.5ā x 2.4ā³ (88.9mm x 114.3mm x 58.0mm)
The Wampler ReWired carries a street price of $279.97. For more information visit https://www.wamplerpedals.com/
Want to know how tubes shape your tone? Join PG contributor Tom Butwin as he breaks down preamp vs. power tubes, tone tweaks, and biasing, in this ultimate beginner's guide to tube amps. From Fender cleans to Marshall grit, learn how to unlock the full potential of your amp!
Shop for tubes for your amp:
https://www.thetubestore.com/shop-by-amp/guitar-am...
https://www.tubeampdoctor.com/en/tubes-accessoires...
Hand-built in the USA, this pedal features original potentiometer values, True Bypass, and three unique modes for versatile distortion options. Commemorative extras included.
This limited-edition pedal is limited to a 1,974-piece run to commemorate the year of DODās start, 1974. The original OD250 put DOD on the map as āAmericaās Pedalā and continues to be an industry favorite today. Each pedal will have a serial-numbered Certificate of Authenticity, a commemorative laser-etched pedal topper, several commemorative guitar picks, and multiple commemorative stickers.
Hand-built in the USA, the DOD OD250 ā 50th Anniversary Edition pedal boasts Gain and Level controls using the original potentiometer values and tapers giving the control knob the feel and range that DOD enthusiasts love. A three-position toggle switch features the OD250ās classic āSILICONā mode replicating that original sound. The āGe/ASYMā mode uses a vintage Germanium diode for asymmetrical even-harmonic distortion. āLIFTā mode cuts the diode clipping from the signal path allowing for a clean boost or even a dirty boost when the vintage LM741 op-amp is clipped at higher gain settings. The DOD 250 also features True Bypass to maintain the integrity of your guitar tone.
This limited edition OD250 is outfitted in a stunning metal flake gray finish with classic yellow screenprint in a callback to the original OD250 of the 1970s. An etched aluminum badge on each unit commemorates this occasion. The DOD OD 250 ā 50th Anniversary is ready to take its place among the historic DOD pedal lineup.
When John Johnson and āMr. DODā himself, David O. DiFrancesco set out to make DOD Electronics in Salt Lake City, Utah 50 years ago, they had no idea how enduring their legacy would be. Now 50 years later, DOD Electronics continues to be at the forefront of pedal technology. The DOD OD 250 ā 50th Anniversary Pedal is an exceptional testament to DOD Electronicsā longāstanding success.
Retail Price: $250.00
For more information, please visit digitech.com.
Want to know how tubes shape your tone? Join PG contributor Tom Butwin as he breaks down preamp vs. power tubes, tone tweaks, and biasing, in this ultimate beginner's guide to tube amps. From Fender cleans to Marshall grit, learn how to unlock the full potential of your amp!
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